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Purpose: With the increasing use of flattening filter free (FFF) beams, it is important to evaluate impact on the skin dose and target coverage of breast cancer treatments. This study aimed to compare skin doses of treatments using FFF and flattening filter (FF) beams for breast cancer.Materials and methods: The study established treatment plans for left breast of an anthropomorphic phantom using Halcyon’s 6-MV FFF beam and TrueBeam’s 6-MV FF beam. Volumetric modulated arc therapy (VMAT) with varying numbers of arcs and intensity modulated radiation therapy (IMRT) were employed, and skin doses were measured at five points using Gafchromic EBT3 film. Each measurement was repeated three times, and averaged to reduce uncertainty. All plans were compared in terms of plan quality to ensure homogeneous target coverage.Results: The study found that when using VMAT with two, four, and six arcs, in-field doses were 19%, 15%, and 6% higher, respectively, when using Halcyon compared to TrueBeam. Additionally, when using two arcs for VMAT, in-field doses were 10% and 15% higher compared to four and six arcs when using Halcyon. Finally, in-field dose from Halcyon using IMRT was about 1% higher than when using TrueBeam.Conclusion: Our research confirmed that when treating breast cancer with FFF beams, skin dose is higher than with traditional FF beams. Moreover, number of arcs used in VMAT treatment with FFF beams affects skin dose of the patient. To maintain a skin dose similar to that of FF beams when using Halcyon, it may be worth considering increasing the number of arcs.

Our study reanalyzed the use factor of linear accelerators (LINACs) by using an in-house program based on Digital Imaging and Communications in Medicine radiation therapy (DICOM-RT). We took into account the impact of advancements and changes in treatment trends, including modality, technology, and radiation dose. The use factor was calculated for four LINACs in three hospitals and compared with that of the NCRP 151 report. We analyzed the results based on the treatment techniques and treatment sites for three-dimensional conformal radiation therapy (3D CRT) and intensity modulated radiation therapy or volumetric modulated arc therapy. Our findings revealed that the use factors obtained at 45° and 90° were 14.8% and 13.5% higher than those of the NCRP 151 report. In treatment rooms with a high 3D CRT ratio, the use factor at a specific angle differed by up to 14.6% relative to the NCRP 151 report value. Additionally, the use factors for different treatment sites, especially for breast and spinal treatments, were significantly different from those of the NCRP 151 report.

The purpose of our study is to establish an efficient quality assurance (QA) procedure using a Stealth Chamber—a reference signal detector—as a field chamber. Among the annual QA items, relative dosimetry items such as monitor unit linearity, output constancy according to dose rate, and output constancy according to gantry angle, and the output factor according to the field size were measured and compared with the results of the Farmer-type chamber for True Beam and Halcyon. In addition, output measurement was performed for each field size to evaluate the applicability to small fields. The results obtained using the Stealth Chamber for all items, except for the output constancy according to the gantry angle, were in good agreement with that obtained using the Farmer-type chamber within 1.0%. In the measurement of output constancy items according to gantry angle, the stealth chamber had an error of up to 1.1%, while the Farmer-type chamber had an error of up to 2.7%. The Stealth Chamber had a difference of up to 6% output factor, and in the case of CC13 Ionization Chamber, there was a difference of up to 13% output factor in a small field of 1 x 1 cm2. Our study confirmed the possibility of performing relative dosimetry measurement items among QA items using stealth chambers, especially useful for small field dosimetry of equipment without light fields such as halcyon.

The spin-forbidden CO a 3Π→ X 1Σ Cameron bands (190-270 nm) are the dominant feature of the middle ultraviolet spectrum of the Martian dayglow and aurora. Since their discovery in the Mars dayglow during the Mariner era (Barth, 1969), a number of studies based on observations with the SPICAM instrument on board the Mars Express (Leblanc et al., 2006; Cox et al., 2010; González‐Galindo et al., 2018) and IUVS/MAVEN (Jain et al., 2015) have revealed their altitude distribution and seasonal changes (Gérard et al., 2019). The Cameron bands are also an important marker of the distribution of auroral events on the nightside aurora, together with the CO2+ ultraviolet doublet at 288-289 nm (Gérard et al., 2015; Schneider et al., 2015). One of the important processes producing the metastable a 3Π upper state of the transition is dissociative excitation of CO2 by impact of photoelectrons or auroral electrons: e (E> 11.5 eV) + CO2 à CO (a 3Π) + O + e The excitation process includes cascades from higher lying states, which makes ab initio calculations quite complex. Until recently, models for the production of the Cameron bands used the energy dependence of the cross section initially published by Ajello (1971) 50 years ago. It was later normalized by Avakyan et al. (1999) to the value of Erdman and Zipf (1983) at 80 eV. The absolute value of the cross section was later scaled by different factors to account for revisions of the radiative lifetime of the a3Π state and match the observations. Recently, a new set of measurements in a large laboratory facility attenuating the wall effects has led to a revision of both the shape and the peak value of this cross section (Lee et al., 2021a). In this presentation, we assess the consequences of this revision on the production of the Cameron bands in the Martian airglow and aurora. In particular, we discuss the importance of the contribution of the excitation of CO by electron impact e (E> 6 eV) + CO → CO(a 3Π) + e, also recently re-examined by Lee et al. (2021b). We discuss the relative importance of the two processes and its dependence on the CO mixing ratio in the Mars thermosphere. We also examine how these new values may affect the anomalies in the Cameron/CO2+ UV doublet intensity ratio observed with IUVS in the discrete aurora (Soret et al., 2021). References Ajello, J. M. (1971). The Journal of Chemical Physics, 55(7), 3169-3177. Avakyan, S. V. et al. (1999). CRC Press. Barth, C. A. et al. (1969). Science, 165(3897), 1004-1005. Cox, C. et al. (2010). Journal of Geophysical Research: Planets, 115(E4). Erdman, P. W., & Zipf, E. C. (1983). Planetary and Space Science, 31(3), 317-321. Gérard, J. C. et al. (2019). Journal of Geophysical Research: Space Physics, 124(7), 5816-5827. González‐Galindo, F. et al. (2018). Journal of Geophysical Research: Planets, 123(7), 1934-1952. Jain, S. K. et al. (2015). Geophysical Research Letters, 42(21), 9023-9030. Leblanc, F. et al. (2006). Journal of Geophysical Research: Planets, 111(E9). Lee, R., et al. (2021a). Mars and Venus dayglow studies based upon laboratory aeronomy from electron Impact of CO2 for analysis of UV Observations by MAVEN, EMM, MEx, and VEx. AGU Fall meeting 2021, New Orleans. Lee, R. A. et al. (2021b). Journal of Geophysical Research: Planets, 126(1), e2020JE006602. Schneider, N. M. et al. (2015). Discovery of diffuse aurora on Mars. Science, 350(6261), aad0313. Soret, L. et al. (2021). Journal of Geophysical Research: Space Physics, 126(10), e2021JA029495.

For minimizing patient inconvenience caused by intraoral sensor discomfort and unnecessary radiational exposure of diagnosis of dental caries, we developed a new system that insert the x-ray source tube (diameter: 3 mm, tube voltage: ~ 55 kV, tube current: ~ 300 uA) inside of the oral cavity and placed the the radiation acquisition device outside. The purpose of this study was to investigate the optimal acquisition conditions for the diagnosis of dental caries and to evaluate the image performance of the new intraoral x-ray imaging system. The 33 model sets were made with 3 teeth were randomly selected from 99 extracted human teeth, total of 5 conventional radiographic sets as control groups and 1 experimental set were prepared after cavity forming the 4 sites of artificial proximal caries(grade 1 to 4). Total 198 images were obtained and those were read by seven dentists of the grades and the correct answer rates were calculated and analyzed by one - way ANOVA. The new x-ray images were shown that there is no significant difference in reading for the diagnosis of proximal caries. Therefore the new x-ray system might be considerable for using in the clinical dental caries diagnosis, especially initial caries stage.

Objectives To compare overall survival (OS) in locally advanced hypopharyngeal cancer treated with surgery or definitive chemoradiotherapy in the contemporary era. Methods From 2010 to 2015, data for patients diagnosed with hypopharyngeal cancer (T2‐T4aM0) and treated with total pharyngectomy with lymph node dissection (surgery group) or definitive radiotherapy and chemotherapy (chemoradiotherapy group) was retrieved from the SEER database. Multivariate analyses were performed in each subgroup divided according to T category (T2‐3 or T4a). Results The number of patients in the surgery and chemoradiotherapy groups was 209 and 648, respectively. Among them, the number of T4a patients was 111 and 126 in each group. Three‐year OS rate in the surgery and chemoradiotherapy groups was 37.9% and 44.1%, respectively (P = 0.178). The 3‐year OS rate for the T2‐3 patients was 46.5% and 48.7% (P = 0.598), and the 3‐year OS rate for the T4a patients was 29.9% and 26.1% in the surgery and chemoradiotherapy groups, respectively (P = 0.439). On multivariate analysis, the chemoradiotherapy group was not inferior to the surgery group in T2‐T4a patients (Hazard ratio [HR] for the chemoradiotherapy group 0.889, 95% confidence interval [CI] 0.699‐1.129, P = 0.334), in T2‐3 patients (HR 0.932, 95% CI 0.699‐1.297, P = 0.675), and in T4a patients (HR 0.880, 95% CI 0.617‐1.256, P = 0.481). Conclusions Chemoradiotherapy for locally advanced hypophagyngeal cancer showed a comparable OS rate to surgery. For patients with T4a category cancer with high possibility of preserving the laryngopharyngeal function, chemoradiotherapy may be a promising alternative treatment.

An X-ray control algorithm to modulate the X-ray intensity distribution over the FOV (field of view) has been developed by using numerical analysis and MCNP5, a particle transport simulation code on the basis of the Monte Carlo method. X-rays, which are widely used in medical diagnostic imaging, should be controlled in order to maximize the performance of the X-ray imaging system. However, transporting X-rays, like a liquid or a gas is conveyed through a physical form such as pipes, is not possible. In the present study, an X-ray control algorithm and technique to uniformize the Xray intensity projected on the image sensor were developed using a flattening filter and a collimator in order to alleviate the anisotropy of the distribution of X-rays due to intrinsic features of the X-ray generator. The proposed method, which is combined with MCNP5 modeling and numerical analysis, aimed to optimize a flattening filter and a collimator for a uniform distribution of X-rays. Their size and shape were estimated from the method. The simulation and the experimental results both showed that the method yielded an intensity distribution over an X-ray field of 6×4 cm2 at SID (source to image-receptor distance) of 5 cm with a uniformity of more than 90% when the flattening filter and the collimator were mounted on the system. The proposed algorithm and technique are not only confined to flattening filter development but can also be applied for other X-ray related research and development efforts.

This study applied statistical process control to set and verify the quality assurances (QA) tolerance standard for our hospital’s characteristics with the criteria standards that are applied to all the treatment sites with this analysis. Gamma test factor of delivery quality assurances (DQA) was based on 3%/3 mm. Head and neck, breast, prostate cases of intensity modulated radiation therapy (IMRT) or volumetric arc radiation therapy (VMAT) were selected for the analysis of the QA treatment sites. The numbers of data used in the analysis were 73 and 68 for head and neck patients. Prostate and breast were 49 and 152 by MapCHECK and ArcCHECK respectively. Cp value of head and neck and prostate QA were above 1.0, Cpml is 1.53 and 1.71 respectively, which is close to the target value of 100%. Cpml value of breast (IMRT) was 1.67, data values are close to the target value of 95%. But value of was 0.90, which means that the data values are widely distributed. Cp and Cpml of breast VMAT QA were respectively 1.07 and 2.10. This suggests that the VMAT QA has better process capability than the IMRT QA. Consequently, we should pay more attention to planning and QA before treatment for breast Radiotherapy.

Computed tomographic (CT) is a fundamental imaging modality to generate cross-sectional views of internal anatomy in a living subject or interrogate material composition of an object, and it has been routinely used in clinical applications and nondestructive testing. In a standard CT image, pixels having the same Hounsfield Units (HU) can correspond to different materials, and it is therefore challenging to differentiate and quantify materials. Dual-energy CT (DECT) is desirable to differentiate multiple materials, but the costly DECT scanners are not widely available as single-energy CT (SECT) scanners. Recent advancement in deep learning provides an enabling tool to map images between different modalities with incorporated prior knowledge. Here we develop a deep learning approach to perform DECT imaging by using the standard SECT data. The end point of the approach is a model capable of providing the high-energy CT image for a given input low-energy CT image. The feasibility of the deep learning-based DECT imaging method using a SECT data is demonstrated using contrast-enhanced DECT images and evaluated using clinical relevant indexes. This work opens new opportunities for numerous DECT clinical applications with a standard SECT data and may enable significantly simplified hardware design, scanning dose and image cost reduction for future DECT systems.

Purpose The purpose of this study is to evaluate the treatment outcomes of adjuvant radiotherapy using vaginal brachytherapy (VB) with a lower dose per fraction and/or external beam radiotherapy (EBRT) following surgery for patients with stage I endometrial carcinoma. Materials and methods The subjects were 43 patients with the International Federation of Gynecology and Obstetrics (FIGO) stage I endometrial cancer who underwent adjuvant radiotherapy following surgery between March 2000 and April 2014. Of these, 25 received postoperative VB alone, while 18 received postoperative EBRT to the whole pelvis; 3 of these were treated with EBRT plus VB. The median EBRT dose was 50.0 Gy (45.0-50.4 Gy) and the VB dose was 24 Gy in 6 fractions. Tumor dose was prescribed at a depth of 5 mm from the cylinder surface and delivered twice per week. Results The median follow-up period for all patients was 57 months (range, 9 to 188 months). Five-year disease-free survival (DFS) and overall survival (OS) for all patients were 92.5% and 95.3%, respectively. Adjuvant radiotherapy was performed according to risk factors and stage IB, grade 3 and lymphovascular invasion were observed more frequently in the EBRT group. Five-year DFS for EBRT and VB alone were 88.1% and 96.0%, respectively (p = 0.42), and 5-year OS for EBRT and VB alone were 94.4% and 96%, respectively (p = 0.38). There was no locoregional recurrence in any patient. Two patients who received EBRT and 1 patient who received VB alone developed distant metastatic disease. Two patients who received EBRT had severe complications, one each of grade 3 gastrointestinal complication and pelvic bone insufficiency fracture. Conclusion Adjuvant radiotherapy achieved high DFS and OS with acceptable toxicity in stage I endometrial cancer. VB (with a lower dose per fraction) may be a viable option for selected patients with early-stage endometrial cancer following surgery.

Legal Order in the World’s Oceans: UN Convention on the Law of the Sea assesses the impact of the 1982 Convention on the Law of the Sea (UNCLOS) and many aspects and challenges of modern law of the sea.

CT (computed tomography) images, metal materials such as tooth supplements or surgical clips can cause metal artifact and degrade image quality. In severe cases, this may lead to misdiagnosis. In this research, we developed a new MAR (metal artifact reduction) algorithm by using an edge preserving filter and the MATLAB program (Mathworks, version R2012a). The proposed algorithm consists of 6 steps: image reconstruction from projection data, metal segmentation, forward projection, interpolation, applied edge preserving smoothing filter, and new image reconstruction. For an evaluation of the proposed algorithm, we obtained both numerical simulation data and data for a Rando phantom. In the numerical simulation data, four metal regions were added into the Shepp Logan phantom for metal artifacts. The projection data of the metal-inserted Rando phantom were obtained by using a prototype CBCT scanner manufactured by medical engineering and medical physics (MEMP) laboratory research group in medical science at Ewha Womans University. After these had been adopted the proposed algorithm was performed, and the result were compared with the original image (with metal artifact without correction) and with a corrected image based on linear interpolation. Both visual and quantitative evaluations were done. Compared with the original image with metal artifacts and with the image corrected by using linear interpolation, both the numerical and the experimental phantom data demonstrated that the proposed algorithm reduced the metal artifact. In conclusion, the evaluation in this research showed that the proposed algorithm outperformed the interpolation based MAR algorithm. If an optimization and a stability evaluation of the proposed algorithm can be performed, the developed algorithm is expected to be an effective tool for eliminating metal artifacts even in commercial CT systems.

Conventional VMAT optimizes aperture shapes and weights at uniformly sampled stations, which is a generalization of the concept of a control point. Recently, rotational station parameter optimized radiation therapy (SPORT) has been proposed to improve the plan quality by inserting beams to the regions that demand additional intensity modulations, thus formulating nonuniform beam sampling. This work presents a new rotational SPORT planning strategy based on reweighted total-variation (TV) minimization (min.), using beam’s-eye-view dosimetrics (BEVD) guided beam selection. The convex programming based reweighted TV min. assures the simplified fluence-map, which facilitates single-aperture selection at each station for single-arc delivery. For the rotational arc treatment planning and non-uniform beam angle setting, the mathematical model needs to be modified by additional penalty term describing the fluence-map similarity and by determination of appropriate angular weighting factors. The proposed algorithm with additional penalty term is capable of achieving more efficient and deliverable plans adaptive to the conventional VMAT and SPORT planning schemes by reducing the dose delivery time about 5 to 10 s in three clinical cases (one prostate and two head-and-neck (HN) cases with a single and multiple targets). The BEVD guided beam selection provides effective and yet easy calculating methodology to select angles for denser, non-uniform angular sampling in SPORT planning. Our BEVD guided SPORT treatment schemes improve the dose sparing to femoral heads in the prostate and brainstem, parotid glands and oral cavity in the two HN cases, where the mean dose reduction of those organs ranges from 0.5 to 2.5 Gy. Also, it increases the conformation number assessing the dose conformity to the target from 0.84, 0.75 and 0.74 to 0.86, 0.79 and 0.80 in the prostate and two HN cases, while preserving the delivery efficiency, relative to conventional single-arc VMAT plans.

Researchers at Changwon National University’s Radiation Detector Development Laboratory(RDD) fabricated a single-channel double-GEM(gas electron multiplier) chamber and measured the pulse height distribution of signals produced by exposing the chamber to an Sr-90 source provided by the Korea Research Institute of Standards and Science(KRISS). A beta-ray electron incident on the GEM chamber ionizes gaseous molecules in the drift region of the chamber by means of electromagnetic interactions. After the leased electrons are amplified by electron avalanches in the GEM stages, the multiplied electrons go from the lowest GEM foil toward the anode of the chamber and induce one signal pulse, corresponding to the incident electron, on the readout pad. The charge signal distribution measured during Sr-90 radioactive source irradiation was compared with the simulation done by using a Landau probability distribution. The energy loss distribution of beta-ray electrons, which deposited part of their energy in a thin GEM chamber while traversing gases within the drift region of that chamber, was in good agreement with the calculation of the Landau probability distribution. The pulse height distributions for energy losses of beta-ray electrons incident on the chamber due to Sr-90 disintegrations were observed in order to select a suitable gas mixture for the chamber. The ratios of the Ar/CO2 gas were 75/25, 80/20, 85/15, and 90/10.

A beam stop array (BSA) is widely used to estimate the scatter distribution of cone-beam computed tomography (CT) experimentally. A rectangular BSA, which is the most generally used, produces a penumbra region at the edge of the grid on the projection image. The penumbra region can be the cause of an inaccurate scatter estimate and loss of image data. In this study, two types of BSAs have been designed and developed, a linear BSA (l-BSA), which is a simple rectangular type, and a curved BSA (c-BSA) to avoid the penumbra effect. A Monte Carlo simulation was performed to determine the thickness and the material of beam stop arrays. The particle tracking technique of MCNP5 code was used to analyze the accuracy of the scatter distribution acquired by the beam stop arrays. The improvement in the image quality was analyzed by using an in-house phantom, a simple type CT phantom, and a humanoid phantom. How the curved beam stop array improved the penumbra effect was also analyzed in a large field of view. The additional dose caused by a dual scan was analyzed by using a Monte Carlo simulation and experiment. The accuracies of the scatter estimates were 83.4% for the c-BSA and 90.4% for the l-BSA. The c-BSA compensated the penumbra effect effectively while the l-BSA had a severe penumbra region in the partial projection image in a large field of view. Contrasts were improved by 24.8 (air-PMMA), 55.8 (Teflon-PMMA), and 81.7% (water-PMMA) for the c-BSA and 11.1 (air-PMMA), 44.1 (Teflon-PMMA), and 82.2% (water-PMMA) for the l-BSA by scatter correction. After noise suppression, the contrast-to-noise ratios were improved by 2.7–4.1 times for the c-BSA and 3.5–5.3 times for the l-BSA. Uniformities were also improved by up to 10 times for the c-BSA and 12 times for the l-BSA. The quality of the humanoid phantom image was also improved after the scatter correction. Consequently, the c-BSA can improve the image quality of cone-beam CT and compensate for the penumbra effect without an additional dose of radiation.

In this paper, we present a nonlinear three-dimensional interpolation scheme for gray-level medical images. The scheme is based on the moving least squares method but introduces a fundamental modification. For a given evaluation point, the proposed method finds the local best approximation by reproducing polynomials of a certain degree. In particular, in order to obtain a better match to the local structures of the given image, we employ locally data-adapted least squares methods that can improve the classical one. Some numerical experiments are presented to demonstrate the performance of the proposed method. Five types of data sets are used: MR brain, MR foot, MR abdomen, CT head, and CT foot. From each of the five types, we choose five volumes. The scheme is compared with some well-known linear methods and other recently developed nonlinear methods. For quantitative comparison, we follow the paradigm proposed by Grevera and Udupa (1998). (Each slice is first assumed to be unknown then interpolated by each method. The performance of each interpolation method is assessed statistically.) The PSNR results for the estimated volumes are also provided. We observe that the new method generates better results in both quantitative and visual quality comparisons.

A new concept of periapical radiography, intra oral x-ray tube and detector system is introduced. It is new system that a miniature x-ray tube is inserted into mouse and it acquired digital image using external detector. In this study, we have investigated temperature and dose distribution of insertional x-ray tube for periapical radiography. To analyze temperature characteristic of x-ray tube, we attached the thermocouple to surface of x-ray tube and we measured the temperature according to distance. Also, we measured the dose distribution of a miniature x-ray tube according to distance. As a result, temperature was constant to over 2mm without cooling system, dose distribution of x-ray tube was 3.14 and 1.84mGy in 3 and 5cm, respectively. Therefore, the proposed x-ray system works in lower dose than conventional dental x-ray system. Thus, it is considered that new concept of system will have a significant effect on medical imaging technology.

Background/aim We evaluated dosimetric and clinical results of volumetric-modulated arc therapy (VMAT) treating internal mammary nodes (IMNs) in patients with locally advanced breast cancer. Patients and methods Between July 2012 and December 2013, treatment outcomes of 31 patients with stage III breast cancer treated with postoperative radiotherapy including the IMN field using VMAT were analyzed. Results The median follow-up was 25.2 months. VMAT showed good homogeneity and improved conformity. The incidence of lung toxicity of grade 2 or more was 3.2%, and cardiac toxicity was not observed. No patient developed local recurrence. Conclusion VMAT appears safe for the treatment of locally advanced breast cancer including the IMN field.

A new treatment facility for heavy ion therapy since 2010 was constructed. In the broad beam, a range shifter, ridge filter and multi leaf collimator (MLC) for the generation of the spread-out Bragg peak is used. In this case, secondary neutrons produced by the interactions of the ion field with beam-modifying devices (e.g. double-scattering system, beam shaping collimators and range compensators) are very important for patient safety. Therefore, these components must be carefully examined in the context of secondary neutron yield and associated secondary cancer risk. In this article, Monte Carlo simulation has been carried out with the FLUktuierende KAskade particle transport code, the fluence and distribution of neutron generation and the neutron dose equivalent from the broad beam components are compared using carbon and proton beams. As a result, it is confirmed that the yield of neutron production using a carbon beam from all components of the broad beam was higher than using a proton beam. The ambient dose by neutrons per heavy ion and proton ion from the MLC surface was 0.12-0.18 and 0.0067-0.0087 pSv, respectively, which shows that heavy ions generate more neutrons than protons. However, ambient dose per treatment 2 Gy, which means physical dose during treatment by ion beam, is higher than carbon beam because proton therapy needs more beam flux to make 2-Gy prescription dose. Therefore, the neutron production from the MLC, which is closed to the patient, is a very important parameter for patient safety.

Purpose: A new treatment scheme coined as dense angularly sampled and sparse intensity modulated radiation therapy (DASSIM-RT) has recently been proposed to bridge the gap between IMRT and VMAT. By increasing the angular sampling of radiation beams while eliminating dispensable segments of the incident fields, DASSIM-RT is capable of providing improved conformity in dose distributions while maintaining high delivery efficiency. The fact that DASSIM-RT utilizes a large number of incident beams represents a major computational challenge for the clinical applications of this powerful treatment scheme. The purpose of this work is to provide a practical solution to the DASSIM-RT inverse planning problem. Methods: The inverse planning problem is formulated as a fluence-map optimization problem with total-variation (TV) minimization. A newly released L1-solver, template for first-order conic solver (TFOCS), was adopted in this work. TFOCS achieves faster convergence with less memory usage as compared with conventional quadratic programming (QP) for the TV form through the effective use of conic forms, dual-variable updates, and optimal first-order approaches. As such, it is tailored to specifically address the computational challenges of large-scale optimization in DASSIM-RT inverse planning. Two clinical cases (a prostate and a head and neck case) are used to evaluate the effectiveness and efficiency of the proposed planning technique. DASSIM-RT plans with 15 and 30 beams are compared with conventional IMRT plans with 7 beams in terms of plan quality and delivery efficiency, which are quantified by conformation number (CN), the total number of segments and modulation index, respectively. For optimization efficiency, the QP-based approach was compared with the proposed algorithm for the DASSIM-RT plans with 15 beams for both cases. Results: Plan quality improves with an increasing number of incident beams, while the total number of segments is maintained to be about the same in both cases. For the prostate patient, the conformation number to the target was 0.7509, 0.7565, and 0.7611 with 80 segments for IMRT with 7 beams, and DASSIM-RT with 15 and 30 beams, respectively. For the head and neck (HN) patient with a complicated target shape, conformation numbers of the three treatment plans were 0.7554, 0.7758, and 0.7819 with 75 segments for all beam configurations. With respect to the dose sparing to the critical structures, the organs such as the femoral heads in the prostate case and the brainstem and spinal cord in the HN case were better protected with DASSIM-RT. For both cases, the delivery efficiency has been greatly improved as the beam angular sampling increases with the similar or better conformal dose distribution. Compared with conventional quadratic programming approaches, first-order TFOCS-based optimization achieves far faster convergence and smaller memory requirements in DASSIM-RT. Conclusions: The new optimization algorithm TFOCS provides a practical and timely solution to the DASSIM-RT or other inverse planning problem requiring large memory space. The new treatment scheme is shown to outperform conventional IMRT in terms of dose conformity to both the targetand the critical structures, while maintaining high delivery efficiency.

Intensity modulated radiation therapy (IMRT) inverse planning using total-variation (TV) regularization has been proposed to reduce the complexity of fluence maps and facilitate dose delivery. Conventionally, the optimization problem with L-1 norm is solved with quadratic programming (QP), which is time consuming and memory expensive due to the second-order Newton update. This study proposes to use a new algorithm, template for first-order conic solver (TFOCS), for fast and memory-efficient optimization in IMRT inverse planning. The TFOCS utilizes dual-variable updates and first-order approaches for TV minimization without the need to compute and store the enlarged Hessian matrix required for Newton update in the QP technique. To evaluate the effectiveness and efficiency of the proposed method, two clinical cases were used for IMRT inverse planning: a head and neck case and a prostate case. For comparison, the conventional QP-based method for the TV form was adopted to solve the fluence map optimization problem in the above two cases. The convergence criteria and algorithm parameters were selected to achieve similar dose conformity for a fair comparison between the two methods. Compared with conventional QP-based approach, the proposed TFOCS-based method shows a remarkable improvement in computational efficiency for fluence map optimization, while maintaining the conformal dose distribution. Compared with QP-based algorithms, the computational speed using TFOCS for fluence optimization is increased by a factor of 4 to 6, and at the same time the memory requirement is reduced by a factor of 3 to 4. Therefore, TFOCS provides an effective, fast and memory-efficient method for IMRT inverse planning. The unique features of the approach should be particularly important in inverse planning involving a large number of beams, such as in VMAT and dense angularly sampled and sparse intensity modulated radiation therapy (DASSIM-RT).

Conventional periphery radiography system has a various problem such as patient dose and the pain of X-ray examination. In this paper, to solve these problems, we suggested insertional miniature x-ray system and we verified the feasibility of this system. First, we performed the Geant4 x-ray simulation to design x-ray collimator and filter to use miniature x-ray tube and we decided optimized thickness of filter and collimator. Also, we measured x-ray spectrum using CdTe detector and PX4 module to verify simulation results. Also, we acquired teeth image of fabricated phantom using conventional dental x-ray and prosed miniature x-ray system. As a results, our system has good image quality as compared to those of conventional systems. Our evaluation of the proposed system indicates that it can be potentially very useful for dental imaging.

The commercially available glass dosimeter (model GD-301) was investigated for its dosimetric characteristics, in order to evaluate its use for in vivo dosimetry. We specifically assessed overall precision of dosimetric dose data in patients who received treatment with the total body irradiation (TBI). Uniformity obtained in this study was within 1.2% (1 SD). The dose–response was linear in the range of 0.5–10 Gy with R of 0.999. Dose rate, SSD, field size, angular and energy dependence were found to be within 3.0%. In vivo skin dosimetry for TBI was performed for 3 patients. For all patients, the glass dosimeter was exposed and measured dose recorded for one fraction in addition to conventional used TLD and MOSFET. Overall uncertainty of the glass dosimeter for in vivo dose measurement was estimated at 2.4% (68.3% confidence level). The measured doses of the glass dosimeter were well within ±5.0% of the prescription dose at all sites expect mediastinum of one patient, for which it is within ±5.7%. Agreement of measured doses between glass dosimeter and TLD, MOSFET was within ±6.3% and ±6.6%, respectively. Results show that the glass dosimeter can be used as an accurate and reproducible dosimeter for TBI treatment skin dose measurements. The glass dosimeter is a practical alternative to TLD or MOSFET as an in vivo dosimeter.

This study compares and analyzes stereotactic radiotherapy using tomotherapy and linac-based fractionated stereotactic radiotherapy in the treatment of intra-cranial tumors, according to some cases. In this study, linac-based fractionated stereotactic radiotherapy and tomotherapy treatment were administered to five patients diagnosed with intra-cranial cancer in which the dose of 18–20 Gy was applied on 3–5 separate occasions. The tumor dosing was decided by evaluating the inhomogeneous index (II) and conformity index (CI). Also, the radiation-sensitive tissue was evaluated using low dose factors V1, V2, V3, V4, V5, and V10, as well as the non-irradiation ratio volume (NIV). The values of the II for each prescription dose in the linac-based non-coplanar radiotherapy plan and tomotherapy treatment plan were (0.125±0.113) and (0.090±0.180), respectively, and the values of the CI were (0.899±0.149) and (0.917±0.114), respectively. The low dose areas, V1, V2, V3, V4, V5, and V10, in radiation-sensitive tissues in the linac-based non-coplanar radiotherapy plan fell into the ranges 0.3%−95.6%, 0.1%−87.6%, 0.1%−78.8%, 38.8%-69.9%, 26.6%-65.2%, and 4.2%−39.7%, respectively, and the tomotherapy treatment plan had ranges of 13.6%−100%, 3.5%−100%, 0.4%−94.9%, 0.2%−82.2%, 0.1%−78.5%, and 0.3%−46.3%, respectively. Regarding the NIV for each organ, it is possible to obtain similar values except for the irradiation area of the brain stem. The percentages of NIV 10%, NIV20%, and NIV30%for the brain stem in each patient were 15%−99.8%, 33.4%−100%, and 39.8%−100%, respectively, in the fractionated stereotactic treatment plan and 44.2%-96.5%, 77.7%-99.8%, and 87.8%−100%, respectively, in the tomotherapy treatment plan. In order to achieve higher-quality treatment of intra-cranial tumors, treatment plans should be tailored according to the isodose target volume, inhomogeneous index, conformity index, position of the tumor upon fractionated stereotactic radiosurgery, and radiation dosage for radiation-sensitive tissues.

We measured the secondary neutron dose from proton craniospinal irradiaton and assessed ways to reduce the secondary neutron dose. A polymethyl methacrylate phantom was irradiated with 159.5MeV proton beams, and CR-39 etch detectors were used to measure the neutron dose equivalent to the proton absorbed dose. We compared the neutron doses generated in cases with and without the neutron absorbing blocks. The neutron dose equivalent to the proton dose (H(10)/D) absorbed on the surface of the phantom showed a decrease from 7.24 to 4.76 mSv/Gy with a change in the displacement from the primary field edge and a decrease from 7.24 to 1.06 mSv/Gy with a change in the depth at a 5-cm displacement from the field edge. When 4.32-mm-thick neutron absorbing blocks were added, the neutron dose decreased by about 30%. We conclude that ratio of the neutron dose to the proton absorbed dose for a proton craniospinal irradiation treatment beam on the surface is less than 1% of the prescription dose. We also observed a 30% decrease in the neutron dose on adding 4.32-mm-thick neutron-absorbing blocks. The contribution of secondary neutrons to the integral dose was found to be very low, and it can be reduced further by using high hydrogen-boron containing blocks.

Although a gel dosimeter is not widely used, it has many potential merits for 3D dosimetry in the development of radiotherapy techniques. Because conventional gel dosimeters tend to sensitively polymerize with oxygen. A new polymer gel that solves these problems was introduced recently. The gel dosimeter contains anti-oxidants that eliminate oxygen chemically instead of using complicated facilities. The type and the concentration of the monomer affect the polymerization of the polymer gel dosimeter. Therefore, the polymerization of the normoxic polymer gel dosimeter is affected by anti-oxidant, the monomer, the constituent ratio, and the condition of the monomer, so many researchers have concentrated on the anti-oxidant, the type of monomer, and the constituent ratio. In this study, a normoxic polymer gel dosimeter was composed using anti-oxidants in a laboratory, and the dose response and sensitivity were measured. The results of this study are as follow the threshold R2 values were reduced, and the radio sensitivity was reduced with the increasing MAA ratio. Otherwise, the increase in the gelatin represented an increase and decrease in the threshold value of R2 values and the radio sensitivity, respectively. Therefore, in this study, 6 − 8 % MAA ratios and an 8 % gelatin ratio, considering the aging effect of the gel, were the optimal values.