67 results on '"Yuji Nakaguchi"'
Search Results
2. Differences between professionals in treatment planning for patients with stage III lung cancer using treatment-planning QA software.
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Daisuke Sato, Motoharu Sasaki, Yuji Nakaguchi, Takeshi Kamomae, Takashi Kawanaka, Akiko Kubo, Chisato Tonoiso, Yuki Kanazawa, Masataka Oita, Akimi Kajino, Akira Tsuzuki, and Hitoshi Ikushima
- Abstract
Background: The quality of treatment planning for stage III non-small cell lung cancer varies within and between facilities due to the different professions involved in planning. Dose estimation parameters were calculated using a feasibility dose-volume histogram (FDVH) implemented in the treatment planning quality assurance software PlanIQ. This study aimed to evaluate differences in treatment planning between occupations using manual FDVH-referenced treatment planning to identify their characteristics. Materials and methods: The study included ten patients with stage III non-small cell lung cancer, and volumetric-modulated arc therapy was used as the treatment planning technique. Fifteen planners, comprising five radiation oncologists, five medical physicists, and five radiological technologists, developed treatment strategies after referring to the FDVH. Results: Medical physicists had a higher mean dose at D98% of the planning target volume (PTV) and a lower mean dose at D2% of the PTV than those in other occupations. Medical physicists had the lowest irradiation lung volumes (V5 Gy and V13 Gy) compared to other professions, and radiation oncologists had the lowest V20 Gy and mean lung dose. Radiological technologists had the highest irradiation volumes for dose constraints at all indexes on the normal lung volume. Conclusions: The quality of the treatment plans developed in this study differed between occupations due to their background expertise, even when an FDVH was used as a reference. Therefore, discussing and sharing knowledge and treatment planning techniques among professionals is essential to determine the optimal treatment plan for each facility and patient. [ABSTRACT FROM AUTHOR]
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- 2023
- Full Text
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3. Impact of treatment planning quality assurance software on volumetric-modulated arc therapy plans for prostate cancer patients
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Motoharu Sasaki, Akimi Kajino, Yuji Nakaguchi, Takeshi Kamomae, and Hitoshi Ikushima
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Male ,Organs at Risk ,medicine.medical_specialty ,Dose-volume histogram ,Computer science ,media_common.quotation_subject ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,Prostate cancer ,0302 clinical medicine ,Software ,medicine ,Dosimetry ,Humans ,Radiology, Nuclear Medicine and imaging ,Medical physics ,Quality (business) ,Radiation treatment planning ,media_common ,Radiological and Ultrasound Technology ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Prostatic Neoplasms ,Radiotherapy Dosage ,medicine.disease ,Volumetric modulated arc therapy ,Oncology ,030220 oncology & carcinogenesis ,Radiotherapy, Intensity-Modulated ,business ,Quality assurance - Abstract
Introduction Software that evaluates the quality of treatment plans (PlanIQTM) has become commercially available in recent years. It includes a feasibility assessment tool that provides the ideal dose volume histogram (DVH) for each organ at risk, based on the ideal dose falloff from the prescribed dose at the target boundary. It is important to investigate whether the PlanIQTM assessment tool (Feasibility DVHTM) can assist treatment planners who have limited to no experience in treatment planning. Therefore, the present study aimed to evaluate this tool's usefulness for improving the quality of treatment plans. Materials & Methods This study included 5 patients with prostate cancer. The treatment planners were 2 graduate students, 2 undergraduate students, and one clinical planner. All students were radiological technology and medical physics students with no clinical experience. Two different volumetric-modulated arc therapy (VMAT) plans were developed before and after Feasibility DVHTM. The quality of each treatment plan was evaluated based on a scoring system implemented in PlanIQTM. Results Of 5 patients included, 4 received improved treatment plans when Feasibility DVHTM was used. Moreover, 4 of 5 treatment planners showed improvement in treatment planning using Feasibility DVHTM. Conclusions The findings suggest that using the Feasibility DVHTM tool may improve treatment plans for different planners and patients. However, planners at any level of experience should be trained to check the dose distribution in addition to checking the DVH, which depends on the adequacy of the contours.
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- 2021
4. [Methodologies and Necessity for IMRT Verification]
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Yuji Nakaguchi
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medicine.medical_specialty ,Computer science ,business.industry ,Radiotherapy Planning, Computer-Assisted ,MEDLINE ,Radiotherapy Dosage ,General Medicine ,Text mining ,medicine ,Radiometry ,Medical physics ,Radiotherapy, Intensity-Modulated ,business - Published
- 2020
5. Image quality of four-dimensional cone-beam computed tomography obtained at various gantry rotation speeds for liver stereotactic body radiation therapy with fiducial markers
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Ryo Toya, Keisuke Yonemura, Yudai Kai, Fujio Araki, Masato Maruyama, Yuji Nakaguchi, and Yoshinobu Shimohigashi
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Cone beam computed tomography ,Rotation ,Image quality ,medicine.medical_treatment ,Biophysics ,General Physics and Astronomy ,Radiosurgery ,Imaging phantom ,030218 nuclear medicine & medical imaging ,Root mean square ,03 medical and health sciences ,0302 clinical medicine ,Fiducial Markers ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Four-Dimensional Computed Tomography ,Projection (set theory) ,Retrospective Studies ,Physics ,Phantoms, Imaging ,business.industry ,General Medicine ,Liver ,030220 oncology & carcinogenesis ,Fiducial marker ,Nuclear medicine ,business - Abstract
In this study, qualities of 4D cone-beam CT (CBCT) images obtained using various gantry rotation speeds (GRSs) for liver stereotactic body radiation therapy (SBRT) with fiducial markers were quantitatively evaluated. Abdominal phantom containing a fiducial marker was moved along a sinusoidal waveform, and 4D-CBCT images were acquired with GRSs of 50–200° min−1. We obtained the 4D-CBCT projection data from six patients who underwent liver SBRT and generated 4D-CBCT images at GRSs of 67–200° min−1, by varying the number of projection data points. The image quality was evaluated based on the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and structural similarity index (SSIM). The fiducial marker positions with different GRSs were compared with the setup values and a reference position in the phantom and clinical studies, respectively. The root mean square errors (RMSEs) were calculated relative to the reference positions. In the phantom study, the mean SNR, CNR, and SSIM decreased from 37.6 to 10.1, from 39.8 to 10.1, and from 0.9 to 0.7, respectively, as the GRS increased from 50 to 200° min−1. The fiducial marker positions were within 2.0 mm at all GRSs. Similarly, in the clinical study, the mean SNR, CNR, and SSIM decreased from 50.4 to 13.7, from 24.2 to 6.0, and from 0.92 to 0.73, respectively. The mean RMSEs were 2.0, 2.1, and 3.6 mm for the GRSs of 67, 100, and 200° min−1, respectively. We conclude that GRSs of 67 and 85° min−1 yield images of acceptable quality for 4D-CBCT in liver SBRT with fiducial markers.
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- 2018
6. Validation of a method for in vivo 3D dose reconstruction in <scp>SBRT</scp> using a new transmission detector
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Yudai Kai, Yuji Nakaguchi, Takeshi Ono, Yoshinobu Shimohigashi, and Masato Maruyama
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animal structures ,87.55.Qr ,medicine.medical_treatment ,87.56.Fc ,Dose profile ,Radiosurgery ,030218 nuclear medicine & medical imaging ,transmission detector ,03 medical and health sciences ,0302 clinical medicine ,Compass ,Image Processing, Computer-Assisted ,Humans ,Radiation Oncology Physics ,Dosimetry ,Medicine ,Radiology, Nuclear Medicine and imaging ,Radiometry ,QA ,Radiation treatment planning ,spatial resolution ,Instrumentation ,Image resolution ,SBRT ,Radiation ,business.industry ,Radiotherapy Planning, Computer-Assisted ,in vivo ,87.55.km ,Detector ,Radiotherapy Dosage ,030220 oncology & carcinogenesis ,Radiotherapy, Intensity-Modulated ,business ,Nuclear medicine ,Monte Carlo Method ,Quality assurance - Abstract
Stereotactic body radiation therapy (SBRT) involves the delivery of substantially larger doses over fewer fractions than conventional therapy. Therefore, SBRT treatments will strongly benefit patients using vivo patient dose verification, because the impact of the fraction is large. For in vivo measurements, a commercially available quality assurance (QA) system is the COMPASS system (IBA Dosimetry, Germany). For measurements, the system uses a new transmission detector (Dolphin, IBA Dosimetry). In this study, we evaluated the method for in vivo 3D dose reconstruction for SBRT using this new transmission detector. We confirmed the accuracy of COMPASS with Dolphin for SBRT using multi leaf collimator (MLC) test patterns and clinical SBRT cases. We compared the results between the COMPASS, the treatment planning system, the Kodak EDR2 film, and the Monte Carlo (MC) calculations. MLC test patterns were set up to investigate various aspects of dose reconstruction for SBRT: (a) simple open fields (2 × 2–10 × 10 cm2), (b) a square wave chart pattern, and (c) the MLC position detectability test in which the MLCs were changed slightly. In clinical cases, we carried out 6 and 8 static IMRT beams for SBRT in the lung and liver. For MLC test patterns, the differences between COMPASS and MC were around 3%. The COMPASS with the dolphin system showed sufficient resolution in SBRT. For clinical cases, COMPASS can detect small changes for the dose profile and dose–volume histogram. COMPASS also showed good agreement with MC. We can confirm the feasibility of SBRT QA using the COMPASS system with Dolphin. This method was successfully operated using the new transmission detector and verified by measurements and MC.
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- 2017
7. Evaluation of Absorbed Dose for CBCT in Image-guided Radiation Therapy: Comparison of Each Devices and Facilities
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Yumiko Kitazato, Fujio Araki, Toshihisa Kawasaki, Masahiro Enzaki, Yoshinobu Shimohigashi, Shinji Kawamura, Masahiko Toyoda, Katsutoshi Shirieda, Daisuke Kawahara, Yuji Nakaguchi, and Noriyuki Kuga
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Dosimeter ,Phantoms, Imaging ,business.industry ,Radiotherapy Planning, Computer-Assisted ,medicine.medical_treatment ,Radiotherapy Dosage ,General Medicine ,Dose distribution ,Cone-Beam Computed Tomography ,Imaging phantom ,030218 nuclear medicine & medical imaging ,Radiation therapy ,03 medical and health sciences ,0302 clinical medicine ,030220 oncology & carcinogenesis ,Absorbed dose ,Calibration ,Ionization chamber ,Dose verification ,Medicine ,business ,Nuclear medicine ,Radiotherapy, Image-Guided ,Image-guided radiation therapy - Abstract
Recently, intensity-modulated radiation therapy (IMRT) is used worldwide, highly accurate verification of the location using image-guided radiation therapy (IGRT) has become critical. However, the use of cone-beam computed tomography (CBCT) to ascertain the location each time raises concerns about its influence on radiotherapy dosage and increased radiation exposure. The purpose of this study was to measure the absorbed dose using nine kilovoltage (kV) devices and two megavoltage (MV) devices (total 11 devices) at eight facilities, compare the absorbed dose among the devices, and assess the characteristics of the respective devices to ensure optimal clinical operation. For the measurement of the absorbed dose, a farmer-type ionization chamber dosimeter, calibrated using a 60Co and an IMRT dose verification phantom manufactured from water-equivalent material RW3, was used to measure the absorbed dose at nine points in the phantom for two regions, the pelvic and cephalic region. The average absorbed dose of the pelvic region was 3.09±0.21 cGy in kV-CBCT (OBI), 1.16±0.16 cGy in kV-CBCT (XVI), 5.64±1.48 cGy in MV-CBCT (4 MV), and 6.33±1.54 cGy in MV-CBCT (6 MV). The average absorbed dose of the cephalic region was 0.38±0.03 cGy in kV-CBCT (OBI), 0.23±0.06 cGy in kV-CBCT (XVI), 4.02±0.72 cGy in MV-CBCT (4 MV), and 4.46±0.77 cGy in MV-CBCT (6 MV). There was a difference in the absorbed dose at the measured points as well as in the dose distribution in the phantom cross section. No major difference was observed in the absorbed dose among identical devices, but a difference was identified among the devices installed at multiple facilities. Therefore, the angle of rotation should be paid attention to when CBCT is taken, and the image-taking conditions should be determined. In addition, it is important to handle the devices only after ascertaining the absorbed dose of each device.
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- 2017
8. 8. Commissioning and Quality Assurance of Image Guided Radiation Therapy(IGRT)
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Yuji Nakaguchi
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medicine.medical_specialty ,Quality management ,business.industry ,Project commissioning ,Computer science ,medicine.medical_treatment ,Radiotherapy Planning, Computer-Assisted ,General Medicine ,Radiation therapy ,medicine ,Medical physics ,Radiotherapy, Intensity-Modulated ,business ,Quality assurance ,Image-guided radiation therapy ,Radiotherapy, Image-Guided - Published
- 2019
9. Modalities and techniques used for stereotactic radiotherapy, intensity-modulated radiotherapy, and image-guided radiotherapy: A 2018 survey by the Japan Society of Medical Physics
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Yuichi Akino, Iori Sumida, Kazunori Miyaura, Ryu Kawamorita, N Tohyama, Masahiko Kurooka, Mitsuhiro Nakamura, Masayori Ishikawa, Yuji Nakaguchi, and Kazuhiko Akita
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Societies, Scientific ,medicine.medical_specialty ,medicine.medical_treatment ,Biophysics ,General Physics and Astronomy ,Image registration ,Image guided radiotherapy ,Radiosurgery ,030218 nuclear medicine & medical imaging ,Stereotactic radiotherapy ,03 medical and health sciences ,0302 clinical medicine ,Japan ,Neoplasms ,Surveys and Questionnaires ,Medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Medical physics ,Image-guided radiation therapy ,Internet ,Modalities ,business.industry ,General Medicine ,Volumetric modulated arc therapy ,Radiation therapy ,030220 oncology & carcinogenesis ,Intensity modulated radiotherapy ,Radiotherapy, Intensity-Modulated ,business ,Radiotherapy, Image-Guided - Abstract
Over the last several decades, there have been great advances in radiotherapy with the development of new technologies and modalities, and radiotherapy trends have changed rapidly. To comprehend the current state of radiotherapy in Japan, the QA/QC 2016–2017 Committee of the Japan Society of Medical Physics set up an intensity-modulated radiotherapy/image-guided radiotherapy (IMRT/IGRT) working group and performed a Web-based survey to show the current status of radiotherapy in Japan. The Web-based questionnaire, developed using Google Forms, contained 42 items: 7 on stereotactic radiotherapy implementation, 4 on IMRT, 24 on IGRT, and 7 on respiratory motion management. The survey was conducted from 17 January to 9 March of 2018; in total, 335 institutions provided data. The results show that volumetric modulated arc therapy was used at a level comparable to that of static gantry IMRT. For IGRT, machine-integrated computed tomography (CT), including kilovoltage or megavoltage cone-beam CT and megavoltage CT, was used at many institutions in conjunction with target-based image registration. For respiratory motion management, breath holding was the most commonly used technique. Our hope is that multi-institutional surveys such as this one will be conducted periodically to elucidate the current status of radiotherapy and emerging developments in this field. If our questionnaire was distributed worldwide, in the same format, then global trends in radiotherapy could be better understood.
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- 2019
10. Dynamic positioning accuracy of a novel multileaf collimator for volumetric modulated arc therapy
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Masato Maruyama, Yoshinobu Shimohigashi, Yudai Kai, Ryota Onizuka, Takeshi Ono, and Yuji Nakaguchi
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Radiation ,Phantoms, Imaging ,Computer science ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Physical Therapy, Sports Therapy and Rehabilitation ,Pass rate ,General Medicine ,Dose distribution ,Volumetric modulated arc therapy ,030218 nuclear medicine & medical imaging ,Multileaf collimator ,03 medical and health sciences ,Gamma analysis ,0302 clinical medicine ,030220 oncology & carcinogenesis ,Dynamic positioning ,Radiology, Nuclear Medicine and imaging ,Radiotherapy, Intensity-Modulated ,Test plan ,Nuclear medicine ,business ,Biomedical engineering - Abstract
We investigated the dynamic positioning accuracy of Agility (Elekta) for volumetric modulated arc therapy (VMAT). The accuracy of the multileaf collimator (MLC) leaf position during VMAT was evaluated using three different tests: (1) a dynamic multileaf collimator (DMLC) output test with various leaf speeds, and gantry angles; (2) a slit-fence test with and without gantry rotation; and (3) a complicated VMAT plans test with dose distributions compared with measurements using gamma analysis. The DMLC output was within 1.5 % under all test conditions. The agreement between the static and VMAT in the slit-fence test was within 0.5 mm. The pass rate of each complicated VMAT test plan was more than 93.9 % ± 0.36 for gamma analysis. We confirmed the dynamic positioning accuracy of Agility, which during VMAT delivery is within VMAT tolerances. The fastest MLC was found to have the potential to offer clinical advantages, such as high-quality rapid VMAT.
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- 2015
11. Validation of secondary dose calculation system with manufacturer-provided reference beam data using heterogeneous phantoms
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Yohei Yotsuji, Yuya Nakamura, and Yuji Nakaguchi
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Radiation ,Materials science ,Dose calculation ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Dose profile ,Physical Therapy, Sports Therapy and Rehabilitation ,General Medicine ,Dose distribution ,Radiation Dosage ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,030220 oncology & carcinogenesis ,Reference beam ,Dosimetry ,Humans ,Radiology, Nuclear Medicine and imaging ,business ,Radiation treatment planning ,Radiometry ,Quality assurance ,Medical systems ,Biomedical engineering - Abstract
The Mobius3D (M3D) system (Mobius Medical Systems) is a second-check dosimetry system. We investigated the dose calculation accuracy of this system using heterogeneous phantoms with reference beam data provided by the manufacturer using simple and patient plans. We compared the dose distributions between M3D and the treatment planning system, as well as the measurements in solid water phantoms, heterogeneous phantoms, and patient plans for Varian and Elekta accelerators. The M3D results agreed well with the measurements in the solid water phantoms for the simple plans. However, the accuracy of M3D appeared to depend on the type of accelerator, as indicated by the slight differences in the dose measurements. Furthermore, the M3D dose measurements differed by 5-10% in the lung and bone regions. Regarding the patient plans, we confirmed that M3D is reasonably accurate as a second-check system, despite the slight accelerator type-dependent dose difference.
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- 2018
12. Accuracy of dose calculation algorithms for virtual heterogeneous phantoms and intensity-modulated radiation therapy in the head and neck
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Ryota Onizuka, Yudai Kai, Yuji Nakaguchi, Yuuki Tomiyama, Fujio Araki, Kazunari Hioki, and Takeshi Ohno
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Dose calculation ,medicine.medical_treatment ,Monte Carlo method ,Physical Therapy, Sports Therapy and Rehabilitation ,Radiation Dosage ,Imaging phantom ,030218 nuclear medicine & medical imaging ,User-Computer Interface ,03 medical and health sciences ,0302 clinical medicine ,medicine ,Humans ,Cutoff ,Radiology, Nuclear Medicine and imaging ,Head and neck ,Radiation treatment planning ,Physics ,Radiation ,Phantoms, Imaging ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Radiotherapy Dosage ,General Medicine ,Intensity-modulated radiation therapy ,Radiation therapy ,Head and Neck Neoplasms ,030220 oncology & carcinogenesis ,Radiotherapy, Intensity-Modulated ,Nuclear medicine ,business ,Monte Carlo Method ,Algorithm ,Algorithms - Abstract
This study verified the dose calculation accuracy of the analytical anisotropic algorithm (AAA), Acuros XB version 10 (AXB10), and version 11 (AXB11) installed in an Eclipse treatment planning system, by comparing with Monte Carlo (MC) simulations. First, the algorithms were compared in terms of dose distributions using four types of virtual heterogeneous multi-layer phantom for 6 and 15 MV photons. Next, the clinical head and neck intensity-modulated radiation therapy (IMRT) dose distributions for 6 MV photons were evaluated using dose volume histograms (DVHs) and three-dimensional gamma analysis. In percentage depth doses (PDDs) for virtual heterogeneous phantoms, AAA overestimated absorbed doses in the air cavity, bone, and aluminum in comparison with MC, AXB10, and AXB11. The PDDs of AXB10 almost agreed with those of MC and AXB11, except for the air cavity. The dose in the air cavity was higher for AXB10 than for AXB11, because their electron cutoff energies are set at 500 and 200 keV, respectively. For head and neck IMRT dose distributions, the D95 in the clinical target volume (CTV) for AAA was almost the same as that for AXB10 and was approximately 7 % larger than that for MC. Comparing each approach with MC using a criterion of 3 %/3 mm, the pass rates for AXB10, AXB11, and AAA were 92.4, 94.7, and 90.4 % in the CTV, respectively. In conclusion, AAA produces dose errors in heterogeneous regions, while AXB11 provides calculation accuracy comparable to MC. AXB10 overestimates the dose in regions that include an air cavity.
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- 2015
13. Validation of fluence-based 3D IMRT dose reconstruction on a heterogeneous anthropomorphic phantom using Monte Carlo simulation
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Nozomu Nagasue, Masato Maruyama, Yoshinobu Shimohigashi, Yuji Nakaguchi, Yudai Kai, and Takeshi Ono
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Computer science ,Monte Carlo method ,quality assurance ,Fluence ,Linear particle accelerator ,Imaging, Three-Dimensional ,Neoplasms ,Compass ,Image Processing, Computer-Assisted ,Radiation Oncology Physics ,Humans ,Radiology, Nuclear Medicine and imaging ,IMRT ,Radiometry ,Radiation treatment planning ,Instrumentation ,Simulation ,Radiation ,Dosimeter ,Phantoms, Imaging ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Radiotherapy Dosage ,three‐dimensional measurement ,Anthropomorphic phantom ,Radiotherapy, Intensity-Modulated ,Particle Accelerators ,verification ,Nuclear medicine ,business ,Monte Carlo Method ,Quality assurance ,Software ,three‐dimensional reconstruction - Abstract
In this study, we evaluated the performance of a three‐dimensional (3D) dose verification system, COMPASS version 3, which has a dedicated beam models and dose calculation engine. It was possible to reconstruct the 3D dose distributions in patient anatomy based on the measured fluence using the MatriXX 2D array. The COMPASS system was compared with Monte Carlo simulation (MC), glass rod dosimeter (GRD), and 3DVH, using an anthropomorphic phantom for intensity‐modulated radiation therapy (IMRT) dose verification in clinical neck cases. The GRD measurements agreed with the MC within 5% at most measurement points. In addition, most points for COMPASS and 3DVH also agreed with the MC within 5%. The COMPASS system showed better results than 3DVH for dose profiles due to individual adjustments, such as beam modeling for each linac. Regarding the dose‐volume histograms, there were no large differences between MC, analytical anisotropic algorithm (AAA) in Eclipse treatment planning system (TPS), 3DVH, and the COMPASS system. However, AAA underestimated the dose to the clinical target volume and Rt‐Parotid slightly. This is because AAA has some problems with dose calculation accuracy. Our results indicated that the COMPASS system offers highly accurate 3D dose calculation for clinical IMRT quality assurance. Also, the COMPASS system will be useful as a commissioning tool in routine clinical practice for TPS. PACS number: 87.55.Qr, 87.56.Fc, 87.61.Bj
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- 2015
14. Commissioning and validation of fluence-based 3D VMAT dose reconstruction system using new transmission detector
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Yudai Kai, Takeshi Oono, Yuji Nakaguchi, Yuya Nakamura, Yoshinobu Shimohigashi, and Masato Maruyama
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Monte Carlo method ,Physical Therapy, Sports Therapy and Rehabilitation ,Radiation Dosage ,Linear particle accelerator ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Optics ,Compass ,Dosimetry ,Humans ,Radiology, Nuclear Medicine and imaging ,Physics ,Radiation ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Detector ,3D reconstruction ,Radiotherapy Dosage ,General Medicine ,Multileaf collimator ,030220 oncology & carcinogenesis ,Ionization chamber ,Radiotherapy, Intensity-Modulated ,Particle Accelerators ,business ,Monte Carlo Method - Abstract
In this study, we evaluated the basic performance of the three-dimensional dose verification system COMPASS (IBA Dosimetry). This system is capable of reconstructing 3D dose distributions on the patient anatomy based on the fluence measured using a new transmission detector (Dolphin, IBA Dosimetry) during treatment. The stability of the absolute dose and geometric calibrations of the COMPASS system with the Dolphin detector were investigated for fundamental validation. Furthermore, multileaf collimator (MLC) test patterns and a complicated volumetric modulated arc therapy (VMAT) plan were used to evaluate the accuracy of the reconstructed dose distributions determined by the COMPASS. The results from the COMPASS were compared with those of a Monte Carlo simulation (MC), EDR2 film measurement, and a treatment planning system (TPS). The maximum errors for the absolute dose and geometrical position were − 0.28% and 1.0 mm for 3 months, respectively. The Dolphin detector, which consists of ionization chamber detectors, was firmly mounted on the linear accelerator and was very stable. For the MLC test patterns, the TPS showed a > 5% difference at small fields, while the COMPASS showed good agreement with the MC simulation at small fields. However, the COMPASS produced a large error for complex small fields. For a clinical VMAT plan, COMPASS was more accurate than TPS. COMPASS showed real delivered-dose distributions because it uses the measured fluence, a high-resolution detector, and accurate beam modeling. We confirm here that the accuracy and detectability of the delivered dose of the COMPASS system are sufficient for clinical practice.
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- 2017
15. Dispatch Reports on the International Conference on Medical Physics (ICMP)
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Yuji Nakaguchi, Hiroaki Hayashi, Takahiro Shimo, Yuki Matsumoto, Yuki Kanazawa, and Keisuke Usui
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Internet Control Message Protocol ,Engineering ,medicine.medical_specialty ,business.industry ,medicine ,Medical physics ,General Medicine ,business - Published
- 2017
16. Optimization of acquisition parameters and accuracy of target motion trajectory for four-dimensional cone-beam computed tomography with a dynamic thorax phantom
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Kengo Nakato, Yudai Kai, Fujio Araki, Masato Maruyama, Nozomu Nagasue, Yuji Nakaguchi, and Yoshinobu Shimohigashi
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Cone beam computed tomography ,Accuracy and precision ,Movement ,Acoustics ,Physical Therapy, Sports Therapy and Rehabilitation ,Imaging phantom ,Image Processing, Computer-Assisted ,Humans ,Radiology, Nuclear Medicine and imaging ,Computer vision ,Four-Dimensional Computed Tomography ,Projection (set theory) ,Image-guided radiation therapy ,Mathematics ,Radiation ,Phantoms, Imaging ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Respiration ,Detector ,General Medicine ,Cone-Beam Computed Tomography ,Thorax ,Trajectory ,Artificial intelligence ,business ,Algorithms - Abstract
Our purpose in this study was to evaluate the performance of four-dimensional computed tomography (4D-CBCT) and to optimize the acquisition parameters. We evaluated the relationship between the acquisition parameters of 4D-CBCT and the accuracy of the target motion trajectory using a dynamic thorax phantom. The target motion was created three dimensionally using target sizes of 2 and 3 cm, respiratory cycles of 4 and 8 s, and amplitudes of 1 and 2 cm. The 4D-CBCT data were acquired under two detector configurations: “small mode” and “medium mode”. The projection data acquired with scan times ranging from 1 to 4 min were sorted into 2, 5, 10, and 15 phase bins. The accuracy of the measured target motion trajectories was evaluated by means of the root mean square error (RMSE) from the setup values. For the respiratory cycle of 4 s, the measured trajectories were within 2 mm of the setup values for all acquisition times and target sizes. Similarly, the errors for the respiratory cycle of 8 s were
- Published
- 2014
17. Validation of a quick three-dimensional dose verification system for pre-treatment IMRT QA
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Yoshinobu Shimohigashi, Masato Maruyama, Takeshi Ono, Yuji Nakaguchi, Fujio Araki, Yudai Kai, Yuki Tomiyama, and Nozomu Nagasue
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Film Dosimetry ,Computer science ,Monte Carlo method ,Physical Therapy, Sports Therapy and Rehabilitation ,Imaging phantom ,Linear particle accelerator ,law.invention ,Imaging, Three-Dimensional ,law ,Compass ,Image Processing, Computer-Assisted ,Humans ,Dosimetry ,Radiology, Nuclear Medicine and imaging ,Radiation ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Radiotherapy Dosage ,Collimator ,General Medicine ,Head and Neck Neoplasms ,Dose verification ,Radiotherapy, Intensity-Modulated ,business ,Nuclear medicine ,Monte Carlo Method ,Quality assurance ,Software - Abstract
In this study, we evaluated the dosimetric performance of the three-dimensional (3D) dose verification system, COMPASS version 3 (IBA Dosimetry, GmbH, Germany). The COMPASS has the function of a dedicated beam modeling and dose calculation. It is able to reconstruct 3D dose distributions on patient CT images, using the incident fluence from a linear accelerator measured with the MatriXX 2D array (IBA Dosimetry). The dose profiles measured with various multi-leaf collimator (MLC) test patterns for the COMPASS were checked by comparison with those of EDR2 (Eastman Kodak, Rochester, NY) films and Monte Carlo (MC) simulations. The COMPASS was also used for dose verification in clinical intensity-modulated radiation therapy (IMRT) plans for head and neck cases. The dose distributions were compared with those measured by 3DVH (Sun Nuclear, Melbourne, FL) and MC. In addition, the quality assurance (QA) times among the COMPASS, 3DVH, and EDR2 were compared. For MLC test patterns, the COMPASS dose profiles agreed within 3 % with those of EDR2 films and MC simulations. The physical resolution of the COMPASS detectors was lower than that of film, but the dose resolution for MLC patterns was comparable to that of film. In clinical plans, the dose-volume-histograms were equal for all systems. The average QA times of the COMPASS, 3DVH, and EDR2 film were 40.1, 59.4, and 121.4 min, respectively. The COMPASS system provides fast and reliable 3D dose verification for clinical IMRT QA. The COMPASS QA process does not require phantom plans. Therefore, it allows a simple QA workflow.
- Published
- 2014
18. Development of a Quality Assurance Phantom for Brachytherapy: The Feasibility of Daily Check with the Phantom
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Kiyotaka Kakei, Yuji Nakaguchi, Tetsuo Saito, Masato Maruyama, Eriko Takenaga, Ryuji Murakami, Masahiro Hashida, Nozomu Nagasue, and Yudai Kai
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Dosimeter ,Materials science ,Quality Assurance, Health Care ,Phantoms, Imaging ,business.industry ,medicine.medical_treatment ,Brachytherapy ,General Medicine ,Radiation Dosage ,Imaging phantom ,Particle detector ,Semiconductor detector ,Mockup ,Ionization chamber ,medicine ,Humans ,Female ,Radiometry ,business ,Nuclear medicine ,Genital Diseases, Female ,Quality assurance - Abstract
Purpose We developed a quality assurance (QA) phantom to enable easy confirmation of radiation source output measurements of a high dose rate (192)Ir intracavitary brachytherapy unit in gynecology. The purpose of this study was to evaluate the feasibility of daily checks using the QA phantom. Methods and materials The QA phantom was designed with tough water phantoms to hold a Farmer-type ionization chamber, with semiconductor detectors used as in vivo dosimeters to measure rectal dose, and three transfer tubes for gynecology. To test the reliability of our QA phantom for the detection of abnormalities in source output or semiconductor detectors, we applied different doses. Results Variations due to different settings of the QA phantom were within 2%. The temporal variations were less than 2% and 5% in the Farmer-type ionization chamber and semiconductor detectors, respectively. Interobserver variations were below 3%. Conclusions With tolerance levels of 2% and 5% for a Farmer-type ionization chamber and semiconductor detectors, respectively, a QA phantom is potentially useful for easily detecting abnormalities by applying daily checks of the brachytherapy unit.
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- 2014
19. A Comparison of Four Commercial Radiation Treatment Planning Systems for Prostate Intensity Modulated Radiation Therapy
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Yuji Nakaguchi, Ryouta Bandou, Tarou Kishi, Masashi Kimura, Motoharu Sasaki, Masataka Oita, and Hitoshi Ikushima
- Subjects
Male ,medicine.medical_specialty ,Dose calculation ,business.industry ,Radiotherapy Planning, Computer-Assisted ,medicine.medical_treatment ,Prostatic Neoplasms ,General Medicine ,Intensity-modulated radiation therapy ,Radiation therapy ,medicine.anatomical_structure ,Treatment plan ,Prostate ,Planning method ,medicine ,Humans ,Medical physics ,Radiotherapy, Intensity-Modulated ,Radiation treatment planning ,business ,Intensity modulation ,Algorithms - Abstract
At present, every manufacturer of intensity modulated radiation therapy (IMRT) equipment uses multi-leaf collimators (MLCs); however, each company's intensity modulation methods and dose calculation algorithms differ. This study used four typical radiation treatment planning systems (RTPSs) employed domestically for prostate IMRT plans to carry out 15 case studies by one planner based on the dose limits at this clinic. The results were used to compare the differences, if any, in RTPS treatment plans. With prostate IMRT plans, an overlap area exists between the PTV and the rectum. For this reason, while observing dose limits of 60-75 Gy (within the dose tolerated by the rectum), securing uniformity and concentration of dose is essential to create the most appropriate treatment plan for the PTV and other targets. Although each RTPS uses different planning methods, it was generally possible to observe this clinic's dose limits by adjusting the parameter values. When identical beam data is used, it is possible to create similar treatment plans.
- Published
- 2013
20. Development of multi-planar dose verification by use of a flat panel EPID for intensity-modulated radiation therapy
- Author
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Fujio Araki, Kazunari Hioki, Yuji Nakaguchi, Tomohiro Kouno, and Takeshi Ono
- Subjects
Physics ,Measurement method ,Radiation ,business.industry ,Electrical Equipment and Supplies ,Radiotherapy Planning, Computer-Assisted ,High resolution ,Radiotherapy Dosage ,Physical Therapy, Sports Therapy and Rehabilitation ,General Medicine ,Dose distribution ,Intensity-modulated radiation therapy ,Radiation Dosage ,Flat panel ,Gamma analysis ,Planar ,Optics ,Dose verification ,Radiology, Nuclear Medicine and imaging ,Radiotherapy, Intensity-Modulated ,business ,Nuclear medicine ,Monte Carlo Method - Abstract
Our purpose in this study was to evaluate the accuracy of a new multi-planar dose measurement method. The multi-planar dose distributions were reconstructed at each depth by convolution of EPID fluence and dose kernels with the use of EPIDose software (SunNuclear). The EPIDose was compared with EPID, MapCHECK (SunNuclear), EDR2 (Kodak), and Monte Carlo-calculated dose profiles. The EPIDose profiles were almost in agreement with Monte Carlo-calculated dose profiles and MapCHECK for test plans. The dose profiles were in good agreement with EDR2 at the penumbra region. For dose distributions, EPIDose, EDR2, and MapCHECK agreed with that of the treatment-planning system at each depth in the gamma analysis. In comparisons of clinical IMRT plans, EPIDose had almost the same accuracy as MapCHECK and EDR2. Because EPIDose has a wide dynamic range and high resolution, it is a useful tool for the complicated IMRT verification. Furthermore, EPIDose can also evaluate the absolute dose.
- Published
- 2012
21. Comparison of Dose Accuracy between 2D Array Detectors for Pre-treatment IMRT QA
- Author
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Yuji Nakaguchi, Kiyotaka Kakei, Masato Maruyama, Fujio Araki, Shunji Saiga, Nozomu Nagasue, Masahiro Hashida, and Tomohiro Kouno
- Subjects
Physics ,Film Dosimetry ,business.industry ,Detector ,Radiotherapy Dosage ,General Medicine ,Standard deviation ,Particle detector ,Linear particle accelerator ,Semiconductor detector ,Semiconductors ,Mockup ,Ionization chamber ,Humans ,Dosimetry ,Radiotherapy, Intensity-Modulated ,Radiometry ,Nuclear medicine ,business - Abstract
The dosimetric properties between various 2D array detectors were compared and were evaluated with regard to the accuracy in absolute dose and dose distributions for clinical treatment fields. We used to check the dose accuracy: 2D array detectors; MapCHECK (Sun Nuclear), EPID (Varian Medical Systems), EPID-based dosimetry (EPIDose, Sun Nuclear), COMPASS (IBA) and conventional system; EDR2 film (Eastman Kodak), Exradin A-14SL ion chamber (0.016 cc, Standard Imaging). First, we compared the dose linearity, dose rate dependence, and output factor between the 2D array detectors. Next, the accuracy of the absolute dose and dose distributions were evaluated for clinical fields. All detector responses for the dose linear were in agreement within 1%, and the dose rate dependence and output factor agreed within a standard deviation of ±1.2%, except for EPID. This is because EPID is fluence distributions. In all the 2D array detectors, the point dose agreed within 5% with treatment planning system (TPS). Pass rates of each detector for TPS were more than 97% in the gamma analysis (3 mm/3%). EPIDose was in a good agreement with TPS. All 2D array detectors used in this study showed almost the same accuracy for clinical fields. EPIDose has better resolution than other 2D array detectors and thus this is expected for dose distributions with a small field.
- Published
- 2012
22. Longitudinal Changes over 2 Years in Parotid Glands of Patients Treated with Preoperative 30-Gy Irradiation for Oral Cancer
- Author
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Toshinori Hirai, Tomoko Nomura, Yuji Nakaguchi, Masanori Shinohara, Etsushi Tomitaka, Yasuyuki Yamashita, Yushi Araki, Keiko Teshima, Hideki Nakayama, Ryuji Murakami, and Mika Kitajima
- Subjects
Male ,Cancer Research ,medicine.medical_specialty ,Saliva ,Time Factors ,medicine.medical_treatment ,Xerostomia ,Preoperative care ,stomatognathic system ,Preoperative radiation ,medicine ,Humans ,Parotid Gland ,Radiology, Nuclear Medicine and imaging ,Irradiation ,Aged ,Retrospective Studies ,Aged, 80 and over ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Cancer ,Organ Size ,Recovery of Function ,General Medicine ,Middle Aged ,medicine.disease ,Neoadjuvant Therapy ,Surgery ,Parotid gland ,Radiation therapy ,stomatognathic diseases ,medicine.anatomical_structure ,Oncology ,Chemotherapy, Adjuvant ,Total dose ,Carcinoma, Squamous Cell ,Female ,Mouth Neoplasms ,Radiotherapy, Adjuvant ,Tomography, X-Ray Computed ,Nuclear medicine ,business ,Follow-Up Studies - Abstract
Objective: To evaluate longitudinal changes in parotid volumes and saliva production over 2 years after 30 Gy irradiation. Methods: We retrospectively evaluated 15 assessable patients treated for advanced oral cancer. Eligibility criteria were a pathologic diagnosis of squamous cell carcinoma, preoperative radiation therapy with a total dose of 30 Gy delivered in 15 fractions, and the availability of longitudinal data of morphological assessments by computed tomography and functional assessments with the Saxon test spanning 2 years after radiation therapy. In the Saxon test, saliva production was measured by weighing a folded sterile gauze pad before and after chewing; the low-normal value is 2 g/2 min. Repeated-measures analysis of variance with Bonferroni adjustment for multiple comparisons was used to determine the longitudinal changes. Results: The normalized ipsilateral parotid volumes 2 weeks and 6-, 12- and 24 months after radiation therapy were found to be 72.5, 63.7, 66.9 and 78.1%, respectively; the normalized contralateral volumes were 69.8, 64.6, 72.2 and 82.0%, respectively. The bilateral parotid volumes were significantly decreased after radiation therapy (P , 0.01). The nadir appeared at 6 months post-radiation therapy and the volumes substantially recuperated 24 months after radiation therapy (P , 0.01). Mean saliva production before radiation therapy was 3.7 g; the longitudinal changes after radiation therapy were 31.3, 38.0, 43.3 and 69.6%, respectively. Substantial recuperation of saliva production was observed 24 months after radiation therapy (P ¼ 0.01). Conclusions: Although parotid volumes and saliva production were decreased after 30 Gy irradiation, we observed the recuperation of morphological and functional changes in the parotid glands 2 years after radiation therapy.
- Published
- 2011
23. Participate in ECR 2010
- Author
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Yuji Nakaguchi, Takeshi Ishimoto, Takayoshi Yamaguchi, Yoshiyuki Noto, Noriyuki Tawara, and Taiki Chono
- Subjects
business.industry ,Medicine ,General Medicine ,business - Published
- 2010
24. Comparison of 3-dimensional dose reconstruction system between fluence-based system and dose measurement-guided system
- Author
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Ryota Onitsuka, Yuji Nakaguchi, Yoshinobu Shimohigashi, Takeshi Ono, Yudai Kai, and Masato Maruyama
- Subjects
medicine.medical_specialty ,Quality Assurance, Health Care ,Computer science ,Monte Carlo method ,Imaging phantom ,030218 nuclear medicine & medical imaging ,law.invention ,03 medical and health sciences ,0302 clinical medicine ,Software ,law ,Compass ,medicine ,Dosimetry ,Humans ,Radiology, Nuclear Medicine and imaging ,Medical physics ,Simulation ,Radiological and Ultrasound Technology ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Detector ,Collimator ,Radiotherapy Dosage ,Oncology ,030220 oncology & carcinogenesis ,Radiotherapy, Intensity-Modulated ,business ,Quality assurance ,Monte Carlo Method - Abstract
COMPASS system (IBA Dosimetry, Schwarzenbruck, Germany) and ArcCHECK with 3DVH software (Sun Nuclear Corp., Melbourne, FL) are commercial quasi-3-dimensional (3D) dosimetry arrays. Cross-validation to compare them under the same conditions, such as a treatment plan, allows for clear evaluation of such measurement devices. In this study, we evaluated the accuracy of reconstructed dose distributions from the COMPASS system and ArcCHECK with 3DVH software using Monte Carlo simulation (MC) for multi-leaf collimator (MLC) test patterns and clinical VMAT plans. In a phantom study, ArcCHECK 3DVH showed clear differences from COMPASS, measurement and MC due to the detector resolution and the dose reconstruction method. Especially, ArcCHECK 3DVH showed 7% difference from MC for the heterogeneous phantom. ArcCHECK 3DVH only corrects the 3D dose distribution of treatment planning system (TPS) using ArcCHECK measurement, and therefore the accuracy of ArcCHECK 3DVH depends on TPS. In contrast, COMPASS showed good agreement with MC for all cases. However, the COMPASS system requires many complicated installation procedures such as beam modeling, and appropriate commissioning is needed. In terms of clinical cases, there were no large differences for each QA device. The accuracy of the compass and ArcCHECK 3DVH systems for phantoms and clinical cases was compared. Both systems have advantages and disadvantages for clinical use, and consideration of the operating environment is important. The QA system selection is depending on the purpose and workflow in each hospital.
- Published
- 2015
25. [Potential uncertainty about image registration in thoracic image-guided radiotherapy]
- Author
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Akiko Kuraoka, Tetsuo Saito, Ryuji Murakami, Yuji Nakaguchi, Yudai Kai, Naoki Kai, Yujiro Fujita, and Masato Maruyama
- Subjects
3d registration ,medicine.medical_specialty ,Esophageal Neoplasms ,Computer science ,business.industry ,Uncertainty ,Isocenter ,Image registration ,General Medicine ,Image guided radiotherapy ,Positive correlation ,medicine ,Humans ,Computer vision ,Medical physics ,Radiography, Thoracic ,Artificial intelligence ,business ,Tomography, X-Ray Computed ,Thoracic esophageal cancer ,Cone beam ct ,Image-guided radiation therapy ,Radiotherapy, Image-Guided - Abstract
PURPOSE Although image-guided radiotherapy (IGRT) is widely used to determine and correct daily setup errors, the additional interpretation for image registration would provide another error. We evaluated the uncertainty in image registration in IGRT. METHOD The subjects consisted of 12 consecutive patients treated with IGRT for thoracic esophageal cancer. Two radiation therapists had consensually achieved daily 3D registration between planning computed tomography (CT) and cone beam CT (CBCT). The original data sets of image registration in all fractions except for boost irradiations with a change in the isocenter positions were selected for evaluation. There were 20 to 32 data sets for each patient: a total of 318 data sets. To evaluate daily setup errors, the mean 3D displacement vector was calculated for each patient. To assess the reproducibility of image registration, two other radiation therapists reviewed the data sets and recorded geometric differences as uncertainty in the image registration. RESULTS The mean 3D displacement vector for each patient ranged from 4.9 to 15.5 mm for setup errors and 0.7 to 2.2 mm for uncertainty in image registration. There was a positive correlation between the 3D vectors for setup error and uncertainty in image registration (r = 0.487, p = 0.016). CONCLUSION Although IGRT can correct the setup errors, potential uncertainty exists in image registration. The setup error would disturb the image registration in IGRT.
- Published
- 2014
26. Absorbed dose measurements for kV-cone beam computed tomography in image-guided radiation therapy
- Author
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Fujio Araki, Takeshi Ohno, Kazunari Hioki, Yuuki Tomiyama, and Yuji Nakaguchi
- Subjects
Cone beam computed tomography ,Radiological and Ultrasound Technology ,business.industry ,Phantoms, Imaging ,Cone-Beam Computed Tomography ,Radiation Dosage ,Imaging phantom ,Kerma ,Mockup ,Absorbed dose ,Ionization chamber ,Calibration ,Dosimetry ,Medicine ,Radiology, Nuclear Medicine and imaging ,business ,Nuclear medicine ,Radiometry ,Algorithms ,Image-guided radiation therapy ,Radiotherapy, Image-Guided - Abstract
In this study, we develope a novel method to directly evaluate an absorbed dose-to-water for kilovoltage-cone beam computed tomography (kV-CBCT) in image-guided radiation therapy (IGRT). Absorbed doses for the kV-CBCT systems of the Varian On-Board Imager (OBI) and the Elekta X-ray Volumetric Imager (XVI) were measured by a Farmer ionization chamber with a (60)Co calibration factor. The chamber measurements were performed at the center and four peripheral points in body-type (30 cm diameter and 51 cm length) and head-type (16 cm diameter and 33 cm length) cylindrical water phantoms. The measured ionization was converted to the absorbed dose-to-water by using a (60)Co calibration factor and a Monte Carlo (MC)-calculated beam quality conversion factor, kQ, for (60)Co to kV-CBCT. The irradiation for OBI and XVI was performed with pelvis and head modes for the body- and the head-type phantoms, respectively. In addition, the dose distributions in the phantom for both kV-CBCT systems were calculated with MC method and were compared with measured values. The MC-calculated doses were calibrated at the center in the water phantom and compared with measured doses at four peripheral points. The measured absorbed doses at the center in the body-type phantom were 1.96 cGy for OBI and 0.83 cGy for XVI. The peripheral doses were 2.36-2.90 cGy for OBI and 0.83-1.06 cGy for XVI. The doses for XVI were lower up to approximately one-third of those for OBI. Similarly, the measured doses at the center in the head-type phantom were 0.48 cGy for OBI and 0.21 cGy for XVI. The peripheral doses were 0.26-0.66 cGy for OBI and 0.16-0.30 cGy for XVI. The calculated peripheral doses agreed within 3% in the pelvis mode and within 4% in the head mode with measured doses for both kV-CBCT systems. In addition, the absorbed dose determined in this study was approximately 4% lower than that in TG-61 but the absorbed dose by both methods was in agreement within their combined uncertainty. This method is more robust and accurate compared to the dosimetry based on a conventional air-kerma calibration factor. Therefore, it is possible to be used as a standard dosimetry protocol for kV-CBCT in IGRT.
- Published
- 2014
27. 3D evaluation of 3DVH program using BANG3 polymer gel dosimeter
- Author
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Yoichi, Watanabe and Yuji, Nakaguchi
- Subjects
Phantoms, Imaging ,Polymers ,Radiotherapy Planning, Computer-Assisted ,Calibration ,Uncertainty ,Humans ,Radiotherapy Dosage ,Radiometry ,Gels - Abstract
With the recent introduction of intensity modulated arc therapy techniques, there is an increasing need for validation of treatment delivery in three-dimensional (3D) space. A commercial dosimetry device ArcCHECK™ (Sun Nuclear Corporation, Melbourne, FL, USA) can be used in conjunction with 3DVH program. With this system, one can reconstruct the 3D dose distribution produced in the actual patient. In this work the authors evaluate the relative accuracy of the ArcCHECK™-3DVH system using BANG3 (MGS Research, Guilford, CT, USA) polymer gel dosimeter.About 15-cm diameter and 20-cm long cylindrical phantoms filled with BANG3 was used to simulate a patient, to which a volumetrically modulated arc therapy plan was created with Pinnacle3 treatment planning software (Philips Healthcare, Andover, MA, USA). The plan (76 Gy total in 38 fractions) was designed for prostate radiotherapy using a 6 MV photon beam from an Elekta Synergy linear accelerator (Elekta AB, Stockholm, Sweden). The treatment was delivered to the simulated patient. The same plan was used to irradiate an ArcCHECK™ device with an insert plug. The point dose at the isocenter was measured using a Farmer-type ionization chamber. The measured dose data were imported into the 3DVH program, which generated the 3D dose distributions projected onto the simulated patient. The dose data recorded in the polymer gel were read out using a MRI scanner and the 3D dose distribution delivered to the simulated patient was analyzed and compared with those from the 3DVH program and the Pinnacle3 software. The comparison was accomplished by using the gamma index, overlaying the isodose lines for a set of data on selected planes, and computing dose-volume histogram of structures.The dose at the center of the ArcCHECK™ device measured with an ionization chamber was 1.82% lower than the dose predicted by Pinnacle3. The 3D dose distribution generated by Pinnacle3 was compared with those obtained by the ArcCHECK™-3DVH system and BANG3. The gamma passing rates for criteria of 3% dose difference, 3 mm distance-to-agreement, and 25% lower dose threshold were 99.1% for the former and 95.7% for the latter. The mean and maximum PTV doses estimated by the 3DVH were 74.0 and 79.3 Gy in comparison to 74.4 and 76.5 Gy with Pinnacle3. Those values for BANG3 measurements were 74.7 and 79.5 Gy. The mean doses to rectum were 40.2, 39.8, and 38.8 Gy for Pinnacle3, 3DVH, and BANG3, whereas the mean doses to the bladder were 26.7, 25.7, and 21.7 Gy, respectively.The ArcCHECK™-3DVH system provides an accurate estimation of 3D dose distribution in an actual patient within a clinically meaningful tolerance level. However, both 3DVH and BANG3 showed two noticeable differences from Pinnacle3. First, the measured dose throughout the PTV region was less uniform than Pinnacle3. Second, the dose gradient at the interface between PTV and rectum was steeper than Pinnacle3 prediction. Further investigation may be able to identify the cause for these findings.
- Published
- 2013
28. [Physical characterizations for an integrated 160-leaf multi-leaf collimator with a new concept design]
- Author
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Fujio Araki, Masato Maruyama, Yuji Nakaguchi, and Takeshi Oono
- Subjects
Materials science ,business.industry ,Penumbra ,Radiotherapy Planning, Computer-Assisted ,Isocenter ,General Medicine ,Equipment Design ,Multi leaf collimator ,Stereotactic radiotherapy ,Optics ,Mockup ,Photon beams ,Large head ,Radiotherapy, Conformal ,business ,Leakage (electronics) - Abstract
In this article, we present a physical characterization of the agility(™) (Elekta). agility(™) is composed of 160 interdigitating multileaf collimators (MLCs) with a width of 5 mm at the isocenter. The physical characterizations that include leaf position accuracy, leakage, field penumbra and the tongue-and-groove (T&G) effect were evaluated using well-commissioned 4, 6 and 10-MV photon beams. The leaf position accuracy was within 0.5 mm for all gantry angles and each MLC. The leakage was 0.44% on average and reached 0.47% at 10 MV: remarkably low due to a new design with tilted leaves. However, the T&G effect occurred due to tilt. It was approximately 20.8% on average and reached 22.3% at 6 MV. The penumbra width increased up to 8.5 mm at a field size of 20×20 cm at 4 MV. High position designed MLCs create a wider penumbra but show lower leakage and large head clearance. Head clearance is an important factor in stereotactic radiotherapy with multiple non-coplanar beams.
- Published
- 2013
29. [Dose distribution from kV-cone beam computed tomography in image-guided radiotherapy]
- Author
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Tomohiro Kouno, Yuji Nakaguchi, Fujio Araki, and Takeshi Oono
- Subjects
Cone beam computed tomography ,Dosimeter ,Materials science ,business.industry ,Phantoms, Imaging ,medicine.medical_treatment ,General Medicine ,Cone-Beam Computed Tomography ,equipment and supplies ,Imaging phantom ,Tomotherapy ,Pelvis ,Absorbed dose ,Ionization chamber ,medicine ,Dosimetry ,Humans ,Nuclear medicine ,business ,Radiometry ,Head ,Monte Carlo Method ,Image-guided radiation therapy ,Radiotherapy, Image-Guided - Abstract
Image-guided radiotherapy (IGRT) is an increasingly commonly adopted technique. As a result, however, total patient dose is increasing rapidly, especially when kV-cone beam computed tomography (CBCT) is applied. This study investigated the dosimetry of kV-CBCT using a Farmer ionization chamber with a (60)Co absorbed-dose calibration factor. The absorbed-dose measurements were performed using an I'mRT phantom (RW3, IBA) which is employed for dose verification of intensity-modulated radiotherapy (IMRT). The I'mRT phantom was used as a substitute for head and pelvis phantoms. The kV-CBCT absorbed dose was evaluated from a beam quality conversion factor of kV to (60)Co and the ionization ratio of the I'mRT phantom and water, calculated using the Monte Carlo method. The dose distribution in the I'mRT phantom was also measured using a radiophotoluminescent glass dosimeter (RGD). The absorbed doses for the pelvis phantom (full scan) ranged from 2.5-4 cGy for kV-CBCT and 4-8 cGy for MV-CBCT. TomoTherapy resulted in a lower dose of approximately 1.3 cGy due to fan-beam. For the head phantom (half scan), the doses ranged from 0.1-0.7 cGy for kV-CBCT and 3-5 cGy for MVCBCT. The results for RGD were similar to ion chamber measurements. It is necessary to decrease the absorbed dose of the organs at risk every time IGRT is applied.
- Published
- 2013
30. [Report on short-time overseas study in 2012]
- Author
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Yuji Nakaguchi
- Subjects
Education, Continuing ,Japan ,Minnesota ,International Educational Exchange ,General Medicine ,Technology, Radiologic - Published
- 2013
31. [Practical method for six-dimensional online correction system with image guided radiation therapy]
- Author
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Fujio Araki, Yuji Nakaguchi, Tomohiro Kouno, and Masato Maruyama
- Subjects
Hexapod ,Correction method ,business.industry ,Computer science ,Significant difference ,Coordinate system ,Robotics ,General Medicine ,Radiotherapy Setup Errors ,Sensitivity and Specificity ,Cat scanning ,Correction system ,Computer vision ,Artificial intelligence ,Particle Accelerators ,Nuclear medicine ,business ,Image-guided radiation therapy ,Radiotherapy, Image-Guided - Abstract
In this study, we developed a correction method for coordinate transformation errors that are produced in combination with the ExacTrac X-ray system (BrainLAB) and HexaPOD (Elekta) in image guided radiation therapy (IGRT). The positional accuracy of the correction method was compared between the ExacTrac Robotics (BrainLAB) and no correction. We tried to correct iBeam evo couch top (Elekta) by operating two steps drive like ExacTrac Robotics. No correction for HexaPOD showed a maximal error of 4.52 mm, and the couch did not move to the correct position. However, our correction method for HexaPOD showed the positional accuracy within 1 mm. Our method has no significant difference with ExacTrac Robotics (paired t-test, P>0.1). But, when the correction values for the rotatory directions were large, the positional accuracy tended to be poor. The smallest setup errors for the rotatory directions are important for IGRT.
- Published
- 2012
32. [Quality assurance of respiratory-gated stereotactic body radiation therapy in lung using real-time position management system]
- Author
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Yuji Nakaguchi, Tomohiro Kouno, Fujio Araki, and Masato Maruyama
- Subjects
Quality Control ,medicine.medical_specialty ,Quality Assurance, Health Care ,Radiotherapy Setup Errors ,Radiosurgery ,Sensitivity and Specificity ,Imaging phantom ,medicine ,Humans ,Respiratory system ,Radiation treatment planning ,Lung ,Reproducibility ,business.industry ,Phantoms, Imaging ,Isocenter ,Radiotherapy Dosage ,General Medicine ,medicine.anatomical_structure ,Absorbed dose ,Radiology ,business ,Nuclear medicine ,Quality assurance ,Algorithms - Abstract
In this study, we investigated comprehensive quality assurance (QA) for respiratory-gated stereotactic body radiation therapy (SBRT) in the lungs using a real-time position management system (RPM). By using the phantom study, we evaluated dose liberality and reproducibility, and dose distributions for low monitor unite (MU), and also checked the absorbed dose at isocenter and dose profiles for the respiratory-gated exposure using RPM. Furthermore, we evaluated isocenter dose and dose distributions for respiratory-gated SBRT plans in the lungs using RPM. The maximum errors for the dose liberality were 4% for 2 MU, 1% for 4-10 MU, and 0.5% for 15 MU and 20 MU. The dose reproducibility was 2% for 1 MU and within 0.1% for 5 MU or greater. The accuracy for dose distributions was within 2% for 2 MU or greater. The dose error along a central axis for respiratory cycles of 2, 4, and 6 sec was within 1%. As for geometric accuracy, 90% and 50% isodose areas for the respiratory-gated exposure became almost 1 mm and 2 mm larger than without gating, respectively. For clinical lung-SBRT plans, the point dose at isocenter agreed within 2.1% with treatment planning system (TPS). And the pass rates of all plans for TPS were more than 96% in the gamma analysis (3 mm/3%). The geometrical accuracy and the dose accuracy of TPS calculation algorithm are more important for the dose evaluation at penumbra region for respiratory-gated SBRT in lung using RPM.
- Published
- 2012
33. Plan Quality and Delivery Time Comparisons Between Volumetric Modulated Arc Therapy and Intensity Modulated Radiation Therapy for Scalp Angiosarcoma: A Planning Study Using X-ray Voxel Monte Carlo Algorithm
- Author
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Ryo Toya, Yoshinobu Shimohigashi, Tetsuo Saito, Natsuo Oya, Yasuyuki Yamashita, Akiko Kuraoka, Masato Maruyama, R. Murakami, Yudai Kai, and Yuji Nakaguchi
- Subjects
Cancer Research ,Radiation ,business.industry ,X-ray ,computer.software_genre ,Volumetric modulated arc therapy ,Quality (physics) ,medicine.anatomical_structure ,Oncology ,Voxel ,Scalp ,Planning study ,Medicine ,Radiology, Nuclear Medicine and imaging ,Angiosarcoma ,business ,Nuclear medicine ,computer ,Monte Carlo algorithm ,Biomedical engineering - Published
- 2016
34. SU-F-T-549: Validation of a Method for in Vivo 3D Dose Reconstruction for SBRT Using a New Transmission Detector
- Author
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Takeshi Ohno, Yuji Nakaguchi, Yoshinobu Shimohigashi, and Ryota Onizuka
- Subjects
Radiobiology ,business.industry ,medicine.medical_treatment ,Detector ,Dose profile ,General Medicine ,Radiation therapy ,Multileaf collimator ,Compass ,Medicine ,Dosimetry ,business ,Nuclear medicine ,Quality assurance - Abstract
Purpose: Recently, there has been increased clinical use of stereotactic body radiation therapy (SBRT). SBRT treatments will strongly benefit from in vivo patient dose verification, as any errors in delivery can be more detrimental to the radiobiology of the patient as compared to conventional therapy. In vivo dose measurements, a commercially available quality assurance platform which is able to correlate the delivered dose to the patient's anatomy and take into account tissue inhomogeneity, is the COMPASS system (IBA Dosimetry, Germany) using a new transmission detector (Dolphin, IBA Dosimetry). In this work, we evaluate a method for in vivo 3D dose reconstruction for SBRT using a new transmission detector, which was developed for in vivo dose verification for intensity-modulated radiation therapy (IMRT). Methods: We evaluated the accuracy of measurement for SBRT using simple small fields (2×2−10×10 cm2), a multileaf collimator (MLC) test pattern, and clinical cases. The dose distributions from the COMPASS were compared with those of EDR2 films (Kodak, USA) and the Monte Carlo simulations (MC). For clinical cases, we compared MC using dose-volume-histograms (DVHs) and dose profiles. Results: The dose profiles from the COMPASS for small fields and the complicated MLC test pattern agreed with those of EDR2 films, and MC within 3%. This showed the COMPASS with Dolphin system showed good spatial resolution and can measure small fields which are required for SBRT. Those results also suggest that COMPASS with Dolphin is able to detect MLC leaf position errors for SBRT. In clinical cases, the COMPASS with Dolphin agreed well with MC. The Dolphin detector, which consists of ionization chambers, provided stable measurement. Conclusion: COMPASS with Dolphin detector showed a useful in vivo 3D dose reconstruction for SBRT. The accuracy of the results indicates that this approach is suitable for clinical implementation.
- Published
- 2016
35. SU-F-T-364: Monte Carlo-Dose Verification of Volumetric Modulated Arc Therapy Plans Using AAPM TG-119 Test Patterns
- Author
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Yuji Nakaguchi, Ryota Onizuka, Takeshi Ohno, and Fujio Araki
- Subjects
Physics ,Gamma analysis ,business.industry ,Monte Carlo method ,Tongue and groove ,Dose verification ,Dosimetry ,General Medicine ,Dose distribution ,Radiation treatment planning ,Nuclear medicine ,business ,Volumetric modulated arc therapy - Abstract
Purpose: To investigate the Monte Carlo (MC)-based dose verification for VMAT plans by a treatment planning system (TPS). Methods: The AAPM TG-119 test structure set was used for VMAT plans by the Pinnacle3 (convolution/superposition), using a Synergy radiation head of a 6 MV beam with the Agility MLC. The Synergy was simulated with the EGSnrc/BEAMnrc code, and VMAT dose distributions were calculated with the EGSnrc/DOSXYZnrc code by the same irradiation conditions as TPS. VMAT dose distributions of TPS and MC were compared with those of EBT3 film, by 2-D gamma analysis of ±3%/3 mm criteria with a threshold of 30% of prescribed doses. VMAT dose distributions between TPS and MC were also compared by DVHs and 3-D gamma analysis of ±3%/3 mm criteria with a threshold of 10%, and 3-D passing rates for PTVs and OARs were analyzed. Results: TPS dose distributions differed from those of film, especially for Head & neck. The dose difference between TPS and film results from calculation accuracy for complex motion of MLCs like tongue and groove effect. In contrast, MC dose distributions were in good agreement with those of film. This is because MC can model fully the MLC configuration and accurately reproduce the MLC motion between control points in VMAT plans. D95 of PTV for Prostate, Head & neck, C-shaped, and Multi Target was 97.2%, 98.1%, 101.6%, and 99.7% for TPS and 95.7%, 96.0%, 100.6%, and 99.1% for MC, respectively. Similarly, 3-D gamma passing rates of each PTV for TPS vs. MC were 100%, 89.5%, 99.7%, and 100%, respectively. 3-D passing rates of TPS reduced for complex VMAT fields like Head & neck because MLCs are not modeled completely for TPS. Conclusion: MC-calculated VMAT dose distributions is useful for the 3-D dose verification of VMAT plans by TPS.
- Published
- 2016
36. SU-G-JeP4-06: Evaluation of Interfractional and Intrafractional Tumor Motion in Stereotactic Liver Radiotherapy, Based On Four-Dimensional Cone-Beam Computed Tomography Using Fiducial Markers
- Author
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Fujio Araki, R. Toya, Yoshinobu Shimohigashi, Masato Maruyama, and Yuji Nakaguchi
- Subjects
Cone beam computed tomography ,medicine.medical_specialty ,Liver tumor ,business.industry ,medicine.medical_treatment ,General Medicine ,medicine.disease ,Radiation therapy ,stomatognathic system ,Medical imaging ,Medicine ,Statistical analysis ,Radiology ,business ,Nuclear medicine ,Fiducial marker ,Tumor motion ,Image-guided radiation therapy - Abstract
Purpose: The purpose of this study was to evaluate the interfractional and intrafractional motion of liver tumors in stereotactic body radiation therapy (SBRT), based on four-dimensional cone-beam computed tomography using fiducial markers. (4D-CBCT). Methods: Seven patients with liver tumors were treated by SBRT with abdominal compression (AC) in five fractions with image guidance based on 4D-CBCT. The 4D-CBCT studies were performed to determine the individualized internal margin for the planning simulation. The interfractional and intrafractional changes of liver tumor motion for all patients was measured, based on the planning simulation 4D-CBCT, pre-SBRT 4D-CBCT, and post-SBRT 4D-CBCT. The interfractional motion change was calculated from the difference in liver tumor amplitude on pre-SBRT 4D-CBCT relative to that of the planning simulation 4D-CBCT for each fraction. The intrafractional motion change was calculated from the difference between the liver tumor amplitudes of the pre- and post-SBRT 4D-CBCT for each fraction. Significant interfractional and intrafractional changes in liver tumor motion were defined as a change ≥3 mm. Statistical analysis was performed using the Pearson correlation. Results: The values of the mean amplitude of liver tumor, as indicated by planning simulation 4D-CBCT, were 1.6 ± 0.8 mm, 1.6 ± 0.9 mm, and 4.9 ± 2.2 mm in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions, respectively. Pearson correlation coefficients between the liver tumor amplitudes, based on planning simulation 4D-CBCT, and pre-SBRT 4D-CBCT during fraction treatment in the LR, AP, and SI directions were 0.6, 0.7, and 0.8, respectively. Interfractional and intrafractional motion changes of ≥3 mm occurred in 23% and 3% of treatment fractions, respectively. Conclusion: The interfractional and intrafractional changes of liver tumor motion were small in most patients who received liver SBRT with AC. In addition, planning simulation 4D-CBCT was useful for representing liver tumor movement in patients undergoing SBRT. This work was supported by JSPS KAKENHI Grant Number 26861004.
- Published
- 2016
37. Evaluation of target localization accuracy for image-guided radiation therapy by 3D and 4D cone-beam CT in the presence of respiratory motion: a phantom study
- Author
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Yuji Nakaguchi, Yudai Kai, Fujio Araki, Yoshinobu Shimohigashi, Kengo Nakato, and Masato Maruyama
- Subjects
business.industry ,media_common.quotation_subject ,Standard deviation ,Imaging phantom ,030218 nuclear medicine & medical imaging ,Intensity (physics) ,03 medical and health sciences ,0302 clinical medicine ,Sine wave ,Optics ,030220 oncology & carcinogenesis ,Maximum intensity projection ,Contrast (vision) ,Projection (set theory) ,business ,General Nursing ,media_common ,Mathematics ,Image-guided radiation therapy - Abstract
We evaluate the target definition accuracy of four-dimensional CT (4D-CT) simulation and target localization accuracy of 3D or 4D cone-beam CT (CBCT) in the presence of respiration. The target motion is modelled by a sine curve or a cos6 curve. The target volumes, shapes, and positions obtained from the 4D-CT simulation are compared with the static CT image and theoretical values of the phantom. Reference average intensity projection (AIP) and maximum intensity projection (MIP) images for target localization are generated from the 4D-CT simulation. Localization involves aligning the AIP/MIP to 3D cone-beam CT (3D-CBCT) or 4D cone-beam CT (4D-CBCT), and localization accuracy is evaluated from the difference in target position between the reference AIP/MIP image and 3D-CBCT/4D-CBCT measurements. 4D-CBCT also allows measurement of the target motion standard deviation (SD) and excursion (EX). The SD and EX errors are calculated with respect to the theoretical value of the phantom. The target volume and position accuracies obtained via 4D-CT at each phase are within 3.0% and 2.5 mm, respectively, of the static and theoretical values for the sine and cos6 curves. The target localization errors for 3D-CBCT are within 1.0 mm regardless of the EX variation and reference image for the sine curve, whereas the errors for the cos6 curve increase from 0.1 to 5.1 mm with increasing EX variation. In contrast, the 4D-CBCT localization errors are within 1.0 mm regardless of EX variation, reference image, and motion pattern. In addition, SD and EX errors, respectively, range from −1.3 to 0.1 mm and −2.2 to 0.1 mm (AIP) and from −4.4 to −2.7 mm and −13.5 to −4.2 mm (MIP). 4D-CBCT for AIP is more accurate than that for MIP. Target localization is simple and accurate for 3D-CBCT and 4D-CBCT with the AIP. However, 3D-CBCT is more inaccurate than 4D-CBCT when considering EX variations with the cos6 curve.
- Published
- 2016
38. [Comparison of various image guided radiation therapy systems; image-guided localization accuracy and patient throughput]
- Author
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Yuji Nakaguchi, Masahiro Hashida, Kiyotaka Kakei, Masato Maruyama, Nozomu Nagasue, Yudai Kai, Motoharu Sasaki, Eriko Takenaga, and Tomohiro Kouno
- Subjects
Cone beam computed tomography ,medicine.medical_specialty ,Patient throughput ,Computer science ,business.industry ,Phantoms, Imaging ,medicine.medical_treatment ,General Medicine ,Cone-Beam Computed Tomography ,Imaging phantom ,Image (mathematics) ,Radiation therapy ,medicine ,Humans ,Computer vision ,Medical physics ,Tomography ,Artificial intelligence ,business ,Throughput (business) ,Image-guided radiation therapy ,Radiotherapy, Image-Guided - Abstract
In this study, we evaluated various image guided radiation therapy (IGRT) systems regarding accuracy and patient throughput for conventional radiation therapy. We compared between 2D-2D match (the collation by 2 X-rays directions), cone beam computed tomography (CBCT), and ExacTrac X-Ray system using phantom for CLINAC iX and Synergy. All systems were able to correct within almost 1 mm. ExacTrac X-Ray system showed in particular a high accuracy. As for patient throughput, ExacTrac X-Ray system was the fastest system and 2D-2D match for Synergy was the slowest. All systems have enough ability with regard to accuracy and patient throughput on clinical use. ExacTrac X-Ray system showed superiority with accuracy and throughput, but it is important to note that we have to choose the IGRT technique depending on the treatment site, the purpose, and the patient's state.
- Published
- 2012
39. FDG-PET/CT-based gross tumor volume contouring for radiation therapy planning: an experimental phantom study
- Author
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Fumi Sakamoto, Morikatsu Yoshida, Ryuji Murakami, Koichi Kawanaka, Yasuyuki Yamashita, Ryo Toya, Kuniyuki Tashiro, Seiji Tomiguchi, Shinya Shiraishi, Yuji Nakaguchi, Naoko Tsujita, and Natsuo Oya
- Subjects
Materials science ,Health, Toxicology and Mutagenesis ,medicine.medical_treatment ,Standardized uptake value ,Sensitivity and Specificity ,Imaging phantom ,Imaging, Three-Dimensional ,Fluorodeoxyglucose F18 ,Neoplasms ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Radiation treatment planning ,Contouring ,Radiation ,medicine.diagnostic_test ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Reproducibility of Results ,Radiotherapy Dosage ,Tumor Burden ,Radiation therapy ,Surface-area-to-volume ratio ,Positron emission tomography ,Positron-Emission Tomography ,Subtraction Technique ,Tomography ,Radiopharmaceuticals ,Nuclear medicine ,business ,Tomography, X-Ray Computed ,Radiotherapy, Image-Guided - Abstract
Positron emission tomography/Radiation therapy planning/Gross tumor volume/Threshold/Standardized uptake value. As there is continuing controversy over the role of F-18-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/CT-fused imaging in radiation therapy (RT) planning, we performed a phantom s tudy to assess the feasibility of FDG-PET/CT-based gross tumor volume (GTV) contouring. The phantom set, consisting of an elliptical bowl and 6 spheres measuring from 10–37 mm in diameter, were filled with FDG to obtain 3 source-to-background ratios (SBRs) of 4, 8, and 16. The ratio to maximum intensity at 5% intervals was applied as the threshold for contouring. The ratio between contoured- and actual volumes (volume ratio) was calculated, and the threshold ratio was selected to provide a volume ratio close to 100%. To consider the clinical application, we applied the threshold value (maximum intensity × threshold ratio) for the largest 37-mm sphere to the 6 spheres. The threshold ratio and the volume ratio in 6 spheres with 3 SBRs were compared using the Friedman test. Threshold ratios ranged from 25–80%; they were higher for smaller spheres (p = 0.003) and lower SBRs (p < 0.001). The volume ratios with the threshold value for the largest 37-mm sphere were lower in smaller spheres (p = 0.010). These results suggest that smaller lesions and higher background activities require a higher threshold ratio and smaller lesions a lower threshold value. FDG-PET/CT-fused imaging should not be used as a single modality but rather to obtain supplemental information in RT planning. The contoured GTV should be adjusted based on clinical data including conventional images.
- Published
- 2012
40. [Cone-beam computed tomography-derived adaptive radiotherapy]
- Author
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Naoko Tsujita, Kiyotaka Kakei, Masato Maruyama, Eriko Takenaga, Tsukasa Kodabashi, Takayuki Yokoo, Yuki Omura, Yuji Nakaguchi, Tetsuo Saito, Tomohiko Matsuyama, and Ryuji Murakami
- Subjects
Radiography, Abdominal ,medicine.medical_specialty ,Cone beam computed tomography ,medicine.medical_treatment ,urologic and male genital diseases ,Pelvis ,stomatognathic system ,medicine ,Humans ,Adaptive radiotherapy ,Lung ,Image-guided radiation therapy ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Radiotherapy Dosage ,General Medicine ,respiratory system ,Cone-Beam Computed Tomography ,equipment and supplies ,Effective depth ,Radiation therapy ,medicine.anatomical_structure ,Abdomen ,Radiology ,Tomography ,Nuclear medicine ,business ,Head ,Neck - Abstract
The purpose of this study was to evaluate the reliability of cone-beam computed tomography (CBCT)-derived adaptive radiotherapy. We evaluate planning computed tomography (pCT) and CBCT in 50 patients who had undergone image guided radiotherapy (IGRT) with CBCT. Irradiated sites included head, neck, chest, abdomen, and pelvis; there were 10 patients in each group. Treatment plans including 153 beam data were recalculated based on CBCT. To compare between pCT and CBCT, we estimated CT values of normal tissues, body contour, effective depth, and monitor units (MU) calculation. The maximum difference in CT values was observed in lung estimation. The 5 mm or more differences in depth were observed in 2 beams of 2 pelvic cases, but CBCT also demonstrated a shift of abdominal wall due to intestinal motility. There were downward trends for the effective depth and MU based on CBCT, especially in lung cases. However, the differences in prescribed dose due to MU calculation were less than 5% because all patients were treated with a multifield irradiation plan. CBCT provides not only precise daily setup but also accurate anatomical information on body contour. In addition, CBCT may be considered as a useful tool for dose calculation.
- Published
- 2012
41. Histopathological Changes in Parotid and Submandibular Glands of Patients Treated with Preoperative Chemoradiation Therapy for Oral Cancer
- Author
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Mitsuhiro Furusawa, Toshinori Hirai, Hideki Nakayama, Yuji Nakaguchi, Akimitsu Hiraki, Etsushi Tomitaka, Naoko Tsujita, Yasuyuki Yamashita, Ryuji Murakami, Ryoji Yoshida, Masanori Shinohara, and Keiko Teshima
- Subjects
Male ,Saliva ,Pathology ,medicine.medical_specialty ,Health, Toxicology and Mutagenesis ,medicine.medical_treatment ,Submandibular Gland ,Adipose tissue ,Antineoplastic Agents ,stomatognathic system ,Acinar cell ,Humans ,Parotid Gland ,Medicine ,Radiology, Nuclear Medicine and imaging ,Aged ,Retrospective Studies ,Tegafur ,Preoperative chemoradiotherapy ,Radiation ,business.industry ,Cancer ,Histology ,Chemoradiotherapy ,Middle Aged ,medicine.disease ,Submandibular gland ,Radiation therapy ,Drug Combinations ,Oxonic Acid ,stomatognathic diseases ,medicine.anatomical_structure ,Preoperative Period ,Carcinoma, Squamous Cell ,Female ,Mouth Neoplasms ,Salivation ,Tomography, X-Ray Computed ,business - Abstract
Radiation therapy/Xerostomia/Salivary glands/Computed tomography/Histology. We retrospectively evaluated the relationship betw een computed tomography (CT)- and histopathological findings of parotid and submandibular glands in six patients treated for advanced oral cancer. Eligibility criteria were a pathologic diagnosis of oral squamous cell carcinoma, preoperative chemoradiation t herapy (CRT) with a total dose of 30 Gy and oral S-1 (80 mg/m 2 /day), the availability of morphological assessments by CT and of functional assessments with the Saxon test before- and 2 weeks after CRT, and the availability of histopathological slides of irradiated parotid and submandibular glands. In the histopathological interpretation, gland structures were divided into acinar-, duct-, and adipose cells and other tis sues. The Mann-Whitney test and the Spearman rank correlation test were used to determine histopathological changes. After 30-Gy irradiation, saliva production and parotid and submandibular volumes were significantly decreased (P < 0.05 each). Histopathological analysis demonstrated that 30-Gy irradiation r esulted in a loss of acinar cells although acinar cells in the submandibular gland were relatively retained; the median acinar rate in the parotid and submandibular glands was 1.1% and 19.0%, respectively. The CT values after CRT were inversely correlated with adipose ratios (r = –0.98, P < 0.01) and there was a strong correlation between CT values before and after CRT (r = 0.97, P < 0.01). Our results suggested that acinar cell loss is a main contributor to changes in the volume and function of irradiated human parotid and submandibular glands. The CT value may reflect the ad ipose ratio rather than salivary function.
- Published
- 2012
42. [Dosimetric correction for a six degrees carbon fiber couch]
- Author
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Nozomu Nagasue, Masato Maruyama, Kiyotaka Kakei, Fujio Araki, Yuji Nakaguchi, and Ryuji Murakami
- Subjects
Monitor unit ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Isocenter ,General Medicine ,Dose distribution ,Imaging phantom ,Carbon ,Mockup ,Carbon Fiber ,Maximum difference ,Medicine ,Tomography ,Radiotherapy, Intensity-Modulated ,Nuclear medicine ,business ,Radiation treatment planning ,Radiometry ,Tomography, X-Ray Computed - Abstract
We investigated experimentally and clinically the influence of a six degree (6D) carbon fiber couch on conventional radiation therapy. We used 4, 6 and 10 MV X-rays and compared dose distributions based on correction methods, i.e. monitor unit (MU) addition, including computed tomography (CT) couch, and the couch modeling. Additionally, we evaluated the clinical value of dosimetric correction for the 6D couch in 30 patients treated with multi-field irradiation. In the phantom study, the maximum difference of isocenter doses attributable to the 6D couch was 5.1%; the difference was reduced with increasing X-ray energy. Although the isocenter dose based on each correction method was precise within ±1%, MU addition underestimated the surface dose. In the clinical study, the maximum difference of isocenter doses attributable to the 6D couch was 2.7%. The correction methods for the 6D couch provide for highly precise treatment planning. However, the clinical indication of complicated correction methods should be considered for each institution or each patient, because the influence of the 6D couch was reduced with multi-field irradiation.
- Published
- 2011
43. Recurrence patterns of glioblastoma treated with postoperative radiation therapy: relationship between extent of resection and progression-free interval
- Author
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Mitsuhiro Furusawa, Yuji Nakaguchi, Yasuyuki Yamashita, Toshinori Hirai, Hideo Nakamura, Hiroyuki Uetani, Mika Kitajima, and Ryuji Murakami
- Subjects
Oncology ,Adult ,Gadolinium DTPA ,Male ,Cancer Research ,medicine.medical_specialty ,Adolescent ,medicine.medical_treatment ,Biopsy ,Contrast Media ,Extent of resection ,Statistics, Nonparametric ,Free interval ,Internal medicine ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Progression-free survival ,Child ,Aged ,Aged, 80 and over ,Radiation ,medicine.diagnostic_test ,business.industry ,Brain Neoplasms ,Postoperative radiation ,Magnetic resonance imaging ,Middle Aged ,medicine.disease ,Magnetic Resonance Imaging ,Hyperintensity ,Surgery ,Tumor Burden ,Radiation therapy ,Disease Progression ,Female ,Radiology ,Neoplasm Recurrence, Local ,business ,Glioblastoma - Abstract
To evaluate progression pattern and progression-free interval for patients with glioblastoma multiforme (GBM), on the basis of the extent of resection. Between January 2000 and September 2009, 138 patients with GBM underwent postoperative radiation therapy and longitudinal magnetic resonance imaging studies. The operations were classified as biopsy, partial resection (PR), and gross total resection (GTR). Progression patterns were classified as gross tumor volume (GTV), T2 hyperintensity (T2h), distant, and free. We used the Kruskal–Wallis test to compare progression-free intervals on the basis of the extent of resection and the progression pattern. Recurrence of biopsied and PR tumors at the GTV site was 100 and 97%, respectively. The median progression-free interval was 3 months for biopsied (n = 29), 4 months for PR (n = 70), and 8 months for GTR (n = 39) tumors (p
- Published
- 2011
44. Dose verification of IMRT by use of a COMPASS transmission detector
- Author
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Shunji Saiga, Masato Maruyama, Yuji Nakaguchi, and Fujio Araki
- Subjects
Physics ,Radiation ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Detector ,Monte Carlo method ,Dose profile ,Physical Therapy, Sports Therapy and Rehabilitation ,Radiotherapy Dosage ,General Medicine ,Gamma analysis ,Optics ,Transmission (telecommunications) ,Head and Neck Neoplasms ,Compass ,Dose verification ,Humans ,Radiology, Nuclear Medicine and imaging ,Radiotherapy, Intensity-Modulated ,business ,Nuclear medicine ,Radiometry ,Quality assurance ,Monte Carlo Method - Abstract
Our purpose in this study was to evaluate the fundamental accuracy of reconstructed dose distributions from the COMPASS system using specific MLC test patterns and complicated IMRT neck plans. The COMPASS-reconstructed dose distributions were compared with those measured with EPID, MapCHECK, and EDR2 film and as well as Monte Carlo-calculated dose profiles with use of square-wave chart patterns of 20-, 10-, and 5-mm gaps and step and pyramid patterns. Additionally, the COMPASS dose distributions for clinical IMRT neck plans were tested. The COMPASS dose profiles were almost in agreement with the Monte Carlo-calculated dose profiles and point doses measured with MapCHECK for 20- and 10-mm gap patterns. The dose profile for a 5-mm gap pattern showed a narrow width due to the detector size in the penumbra region. For step and pyramid patterns, COMPASS agreed with MapCHECK and Monte Carlo calculation, except for EDR2 film. The COMPASS and MapCHECK dose distributions agreed with that of a treatment planning system by gamma analysis (criteria; 3 mm/3%). In comparisons of clinical IMRT neck dose distributions, COMPASS was measured with almost the same accuracy as MapCHECK, but slight deviations were found for large IMRT fields. These deviations could be minimized by improvement of the beam model of the COMPASS system. The COMPASS system can be expected to be used for traditional QA methods in clinical routine with the same accuracy as a MapCHECK diode detector.
- Published
- 2011
45. Comparison of RTPS and Monte Carlo dose distributions in heterogeneous phantoms for photon beams
- Author
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Yuji Nakaguchi, Shogo Fukuda, Fujio Araki, and Masato Maruyama
- Subjects
Electron density ,Photon ,Lung Neoplasms ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Monte Carlo method ,Fast Fourier transform ,General Medicine ,Particle detector ,Computational physics ,Pencil (optics) ,Superposition principle ,symbols.namesake ,Fourier transform ,symbols ,Nuclear medicine ,business ,Monte Carlo Method ,Algorithms ,Mathematics - Abstract
The purpose of this study was to compare dose distributions from three different RTPS with those from Monte Carlo (MC) calculations and measurements, in heterogeneous phantoms for photon beams. This study used four algorithms for RTPS: AAA (analytical anisotropic algorithm) implemented in the Eclipse (Varian Medical Systems) treatment planning system, CC (collapsed cone) superposition from the Pinnacle (Philips), and MGS (multigrid superposition) and FFT (fast Fourier transform) convolution from XiO (CMS). The dose distributions from these algorithms were compared with those from MC and measurements in a set of heterogeneous phantoms. Eclipse/AAA underestimated the dose inside the lung region for low energies of 4 and 6 MV. This is because Eclipse/AAA do not adequately account for a scaling of the spread of the pencil (lateral electron transport) based on changes in the electron density at low photon energies. The dose distributions from Pinnacle/CC and XiO/MGS almost agree with those of MC and measurements at low photon energies, but increase errors at high energy of 15 MV, especially for a small field of 3x3 cm(2). The FFT convolution extremely overestimated the dose inside the lung slab compared to MC. The dose distributions from the superposition algorithms almost agree with those from MC as well as measured values at 4 and 6 MV. The dose errors for Eclipse/AAA are lager in lung model phantoms for 4 and 6 MV. It is necessary to use the algorithms comparable to superposition for accuracy of dose calculations in heterogeneous regions.
- Published
- 2010
46. Monte Carlo-calculated patient organ doses from kV-cone beam CT in image-guided radiation therapy
- Author
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Kazunari Hioki, Yuji Nakaguchi, Yuuki Tomiyama, Takeshi Ohno, and Fujio Araki
- Subjects
medicine.medical_specialty ,business.industry ,medicine.medical_treatment ,Monte Carlo method ,Patient specific ,Imaging phantom ,Radiation therapy ,medicine.anatomical_structure ,medicine ,Radiology ,Nuclear medicine ,business ,Head and neck ,KV Cone Beam CT ,General Nursing ,Pelvis ,Image-guided radiation therapy - Abstract
This study evaluated patient specific organ doses from kV-cone beam computed tomography (kV-CBCT) for the Varian on-board imager (OBI) and the Elekta x-ray volumetric imager (XVI) used in image-guided radiation therapy using Monte Carlo (MC) simulations. The beam modeling for both kV-CBCT systems was performed with the EGSnrc/BEAMnrc user-code. The patient dose distributions were calculated from the modeled kV-CBCT beams by using planning CT data sets for five anatomical regions of head, 'head and neck', chest, abdomen, and pelvis. Two default acquisition modes, full scan mode for chest, abdomen, and pelvis, and half scan mode for head and 'head and neck', were used for both kV-CBCT systems. The MC-calculated dose distributions were converted into absorbed doses by Farmer chamber measurements in body- and head-type phantoms. A body-type phantom (30 cm diameter and 51 cm length) and a head-type phantom (16 cm diameter and 33 cm length) were irradiated with the full scan mode and the half scan mode, respectively. Finally, the patient specific organ doses were quantitatively evaluated from dose-volume histograms. The mean organ doses for soft tissue in chest, abdomen, and pelvis were 1.52-4.13 cGy, 1.30-2.56 cGy, and 2.32-3.81 cGy for OBI, and 0.82-1.60 cGy, 0.66-1.04 cGy, and 0.97-1.41 cGy for XVI, respectively. In the full scan mode, organ doses for XVI were one-half to one-third of those for OBI. The organs located at the anterior surfaces like heart and testes were higher doses than central regions. Meanwhile, the mean doses for soft tissue in the head and 'head and neck' were 0.09-0.43 cGy and 0.09-0.45 cGy for OBI, and 0.13-0.39 cGy and 0.09-0.31 cGy for XVI, respectively. In the half scan mode, the higher doses were observed at the posterior surface for OBI and at the anterior surface for XVI, depending on the scan direction.
- Published
- 2015
47. SU-E-T-342: Dynamic Accuracy and Stability of Novel Multi-Leaf Collimator (MLC) for Volumetric Modulated Arc Therapy (VMAT)
- Author
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Yuji Nakaguchi
- Subjects
business.industry ,Isocenter ,Collimator ,General Medicine ,Multi leaf collimator ,Rotation ,Volumetric modulated arc therapy ,Stability (probability) ,law.invention ,law ,business ,Dose rate ,Nuclear medicine ,Quality assurance ,Mathematics - Abstract
Purpose: We have investigated the dynamic accuracy and long-term stability of an Agility (Elekta, Stockholm, Sweden) multi-leaf collimator (MLC) for volumetric modulated arc therapy (VMAT). Methods: The MLC leaf position accuracy during VMAT delivery was evaluated with the use of three different quality assurance tests for several months: (1) a leaf gap-width test between opposing leaves by measurement of the isocenter dose during constant-gap sliding-window delivery with varied dose rates, MLC leaf speeds, and gantry angles; (2) a leaf position test by picket-fence delivery with and without gantry rotation; and (3) the complicated VMAT test plans were evaluated by measurement using gamma analysis with criteria of 3 mm distance-to-agreement (DTA) and 3% percent dose difference (DD). Results: The leaf gap-width deviation once a week for five months was within 0.15 mm under all the test fractions. There were not clear differences of the accuracy depending on the dose rates, the leaf speeds, and gantry angles. Agreement in the static vs. rotation picket fence test was better than 0.5 mm. This difference is near to the limit of the measurement and is not the difference between static and rotation. The pass rates of each complicated VAMT test plans once a day for a month were more than 90% in the gamma analysis. These pass rates are accuracy enough for VMAT because the test plans included strict test plans. Conclusion: MLC leaf position accuracy and long-term stability were confirmed by the proposed procedures. The Agility MLC showed enough MLC leaf position accuracy and long-term stability for VMAT.
- Published
- 2015
48. Corrigendum: Absorbed dose measurements for kV-cone beam computed tomography in image-guided radiation therapy (Phys. Med. Biol. 59 7297)
- Author
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Yuuki Tomiyama, Kazunari Hioki, Yuji Nakaguchi, Fujio Araki, and Takeshi Ohno
- Subjects
Physics ,medicine.medical_specialty ,Cone beam computed tomography ,Radiological and Ultrasound Technology ,business.industry ,Absorbed dose ,medicine ,Radiology, Nuclear Medicine and imaging ,Medical physics ,Nuclear medicine ,business ,Image-guided radiation therapy - Published
- 2015
49. Tumor motion changes in stereotactic body radiotherapy for liver tumors: an evaluation based on four-dimensional cone-beam computed tomography and fiducial markers.
- Author
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Yoshinobu Shimohigashi, Ryo Toya, Tetsuo Saito, Osamu Ikeda, Masato Maruyama, Keisuke Yonemura, Yuji Nakaguchi, Yudai Kai, Yasuyuki Yamashita, Natsuo Oya, Fujio Araki, Shimohigashi, Yoshinobu, Toya, Ryo, Saito, Tetsuo, Ikeda, Osamu, Maruyama, Masato, Yonemura, Keisuke, Nakaguchi, Yuji, Kai, Yudai, and Yamashita, Yasuyuki
- Subjects
STEREOTACTIC radiotherapy ,LIVER tumors ,TUMOR treatment ,TUMORS ,MOTION capture (Human mechanics) ,CONE beam computed tomography ,FOUR-dimensional imaging ,PHYSIOLOGY - Abstract
Background: For stereotactic body radiation therapy (SBRT) of liver tumors, tumor motion induced by respiration must be taken into account in planning and treatment. We evaluated whether liver tumor motion at the planning simulation represents liver tumor motion during SBRT, and estimated inter- and intrafractional tumor motion changes in patients undergoing liver SBRT.Methods: Ten patients underwent four-dimensional cone-beam computed tomography (4D-CBCT) image-guided liver SBRT with abdominal compression (AC) and fiducial markers. 4D-CBCT was performed to evaluate liver tumor motion at the planning simulation, pre-, and post-SBRT. The translational distances at the center position of the fiducial markers from all 10 phases on the 4D-CBCT images were measured as the extent of the liver tumor motion in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions. Pearson correlation coefficients were calculated to evaluate the correlation between liver tumor motion of the planning simulation and the mean liver tumor motion of the pre-SBRT. Inter- and intrafractional liver tumor motion changes were measured based on the 4D-CBCT of planning simulation, pre-, and post-SBRT. Significant inter- and intrafractional changes in liver tumor motion were defined as a change of >3 mm.Results: The mean (± SD) liver tumor motion of the planning simulation 4D-CBCT was 1.7 ± 0.8 mm, 2.4 ± 2.2 mm, and 5.3 ± 3.3 mm, in the LR, AP, and SI directions, respectively. Those of the pre-SBRT 4D-CBCT were 1.2 ± 0.7 mm, 2.3 ± 2.3 mm, and 4.5 ± 3.8 mm, in the LR, AP, and SI directions, respectively. There was a strong significant correlation between liver tumor motion of the planning simulation and pre-SBRT in the LR (R = 0.7, P < 0.01), AP (R = 0.9, P < 0.01), and SI (R = 0.9, P < 0.01) directions. Significant inter- and intrafractional liver tumor motion changes occurred in 10 and 2% of treatment fractions, respectively.Conclusions: Liver tumor motion at the planning simulation represents liver tumor motion during SBRT. Inter- and intrafractional liver tumor motion changes were small in patients with AC. [ABSTRACT FROM AUTHOR]- Published
- 2017
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50. Can MRI-derived Factors Predict Survival in Patients with Glioblastoma Multiforme?
- Author
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Yuji Nakaguchi, Toshinori Hirai, Shinichiro Nishimura, Jun Ichi Kuratsu, Mika Kitajima, Hiroyuki Uetani, Hideo Nakamura, Yasuyuki Yamashita, and Ryuji Murakami
- Subjects
Oncology ,Cancer Research ,medicine.medical_specialty ,Radiation ,business.industry ,Internal medicine ,medicine ,Radiology, Nuclear Medicine and imaging ,In patient ,medicine.disease ,business ,Glioblastoma - Published
- 2011
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