31 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
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- View/download PDF
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
- Published
- 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. Comparison of 3-dimensional dose reconstruction system between fluence-based system and dose measurement-guided system
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Ryota Onitsuka, Yuji Nakaguchi, Yoshinobu Shimohigashi, Takeshi Ono, Yudai Kai, and Masato Maruyama
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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
18. [Potential uncertainty about image registration in thoracic image-guided radiotherapy]
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Akiko Kuraoka, Tetsuo Saito, Ryuji Murakami, Yuji Nakaguchi, Yudai Kai, Naoki Kai, Yujiro Fujita, and Masato Maruyama
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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.
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- 2014
19. Absorbed dose measurements for kV-cone beam computed tomography in image-guided radiation therapy
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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
20. 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
21. 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
22. 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
23. 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
24. 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
25. 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
26. 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
27. 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
28. 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
- Full Text
- View/download PDF
29. 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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Yoshinobu Shimohigashi, Fujio Araki, Masato Maruyama, Kengo Nakato, Yuji Nakaguchi, and Yudai Kai
- Published
- 2016
- Full Text
- View/download PDF
30. 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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Kazunari Hioki, Fujio Araki, Takeshi Ohno, Yuji Nakaguchi, and Yuuki Tomiyama
- Subjects
COMPUTED tomography ,RADIATION doses ,RADIOTHERAPY - Abstract
A correction to the article "Absorbed dose measurements for kV-cone beam computed tomography in image-guided radiation therapy" that was published in a 2014 issue.
- Published
- 2015
- Full Text
- View/download PDF
31. Absorbed dose measurements for kV-cone beam computed tomography in image-guided radiation therapy.
- Author
-
Kazunari Hioki, Fujio Araki, Takeshi Ohno, Yuji Nakaguchi, and Yuuki Tomiyama
- Subjects
CONE beam computed tomography ,IMAGE-guided radiation therapy ,ABSORBED dose ,RADIATION dosimetry ,MONTE Carlo method dose calculation - 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 a60 Co calibration factor and a Monte Carlo (MC)-calculated beam quality conversion factor, kQ , for60 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. [ABSTRACT FROM AUTHOR]- Published
- 2014
- Full Text
- View/download PDF
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