記述言語：英語   掲載種別：研究論文（学術雑誌）  

Increased heart dose during postoperative radiotherapy (RT) for left-sided breast cancer (BC) can cause cardiac injury, which can decrease patient survival. The deep inspiration breath-hold technique (DIBH) is becoming increasingly common for reducing the mean heart dose (MHD) in patients with left-sided BC. However, treatment planning and DIBH for RT are laborious, time-consuming and costly for patients and RT staff. In addition, the proportion of patients with left BC with low MHD is considerably higher among Asian women, mainly due to their smaller breast volume compared with that in Western countries. The present study aimed to determine the optimal machine learning (ML) model for predicting the MHD after RT to pre-select patients with low MHD who will not require DIBH prior to RT planning. In total, 562 patients with BC who received postoperative RT were randomly divided into the trainval (n=449) and external (n=113) test datasets for ML using Python (version 3.8). Imbalanced data were corrected using synthetic minority oversampling with Gaussian noise. Specifically, right-left, tumor site, chest wall thickness, irradiation method, body mass index and separation were the six explanatory variables used for ML, with four supervised ML algorithms used. Using the optimal value of hyperparameter tuning with root mean squared error (RMSE) as an indicator for the internal test data, the model yielding the best F2 score evaluation was selected for final validation using the external test data. The predictive ability of MHD for true MHD after RT was the highest among all algorithms for the deep neural network, with a RMSE of 77.4, F2 score of 0.80 and area under the curve-receiver operating characteristic of 0.88, for a cut-off value of 300 cGy. The present study suggested that ML can be used to pre-select female Asian patients with low MHD who do not require DIBH for the postoperative RT of BC.

DOI： 10.3892/etm.2023.12235

PubMed

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：(公社)日本診療放射線技師会  

日本では画像診断装置を有する全ての医療施設において,放射線量の記録と管理が義務付けられている.被ばく線量の記録・管理には,放射線量管理システム(DMS)が不可欠であるが,高価なため全ての医療施設に導入することは困難である.そこで本研究では,オープンソースのDMSである「MiSDO」を開発し,シミュレーションによって性能を検証した.その結果,MiSDOは被ばく線量を迅速かつ正確に記録・管理できることが確認できた.MiSDOは,日本の全ての医療施設で使用できる,被ばく線量を記録・管理するためのフリーソフトウエアとして有望である.(著者抄録)

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：VM Media Group sp. z o.o  

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.

DOI： 10.5603/rpor.97511

PubMed

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study evaluated the validity of internal target volumes (ITVs) defined by three- (3DCT) and four-dimensional computed tomography (4DCT), and subsequently compared them with actual movements during treatment. Five patients with upper lobe lung tumors were treated with stereotactic body radiotherapy (SBRT) at 48 Gy in four fractions. Planning 3DCT images were acquired with peak-exhale and peak-inhale breath-holds, and 4DCT images were acquired in the cine mode under free breathing. Cine images were acquired using an electronic portal imaging device during irradiation. Tumor coverage was evaluated based on the manner in which the peak-to-peak breathing amplitude on the planning CT covered the range of tumor motion (± 3 SD) during irradiation in the left-right, anteroposterior, and cranio-caudal (CC) directions. The mean tumor coverage of the 4DCT-based ITV was better than that of the 3DCT-based ITV in the CC direction. The internal margin should be considered when setting the irradiation field for 4DCT. The proposed 4DCT-based ITV can be used as an efficient approach in free-breathing SBRT for upper-lobe tumors of the lung because its coverage is superior to that of 3DCT.

DOI： 10.1007/s12194-023-00737-y

PubMed

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

PURPOSE: We developed a 4-dimensional dynamic dose (4DDD) calculation model for proton pencil beam scanning (PBS). This model incorporates the spill start time for all energies and uses the remaining irradiated spot time model instead of irradiated spot time logs. This study aimed to validate the calculation accuracy of a log file-based 4DDD model by comparing it with dose measurements performed under free-breathing conditions, thereby serving as an alternative approach to the conventional log file-based system. METHODS: Three cubic verification plans were created using a heterogeneous block phantom; these plans were created using 10 phase 4D-CT datasets of the phantom. The CIRS dynamic platform was used to simulate motion with amplitudes of 2.5, 3.75, and 5.0 mm. These plans consisted of eight- and two-layered rescanning techniques. The lateral profiles were measured using a 2D ionization chamber array (2D-array) and EBT3 Gafchromic films at four starting phases, including three sinusoidal curves (periods of 3, 4, and 6 s) and a representative patient curve during actual treatment. 4DDDs were calculated using in-house scripting that assigned a time stamp to each spot and performed dose accumulation using deformable image registration. Furthermore, to evaluate the impact of parameter selection on our 4DDD model calculations, simulations were performed assuming a ±10% change in irradiation time stamp (0.8 ± 0.08 s) and spot scan speed. We evaluated the 2D gamma index and the absolute point doses between the calculated values and the measurements. RESULTS: The 2D-array measurements revealed that the gamma scores for the static plans (no motion) and 4DDD plans exceeded 97.5% and 93.9% at 3%/3 mm, respectively. The average gamma score of the 4DDD plans was at least 96.1%. When using EBT3 films, the gamma scores of the 4DDD model exceeded 92.4% and 98.7% at 2%/2 mm and 3%/3 mm, respectively. Regarding the 4DDD point dose differences, more than 95% of the dose regions exhibited discrepancies within ±5.0% for 97.7% of the total points across all plans. The spot time assignment accuracy of our 4DDD model was acceptable even with ±10% sensitivity. However, the accuracy of the scan speed, when varied within ±10% sensitivity, was not acceptable (minimum gamma scores of 82.6% and maximum dose difference of 12.9%). CONCLUSIONS: Our 4DDD calculations under free-breathing conditions using amplitudes of less than 5.0 mm were in good agreement with the measurements regardless of the starting phases, breathing curve patterns (between 3 and 6 s periods), and varying numbers of layered rescanning. The proposed system allows us to evaluate actual irradiated doses in various breathing periods, amplitudes, and starting phases, even on PBS machines without the ability to record spot logs.

DOI： 10.1002/mp.16725

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Hirosaki University Press.  

The ion recombination factor (k_s) of a beam without a flattening filter differs from that of a filtered beam. In this study, we examined the effect of changing the measurement conditions on k_s in the off-axis direction, and clarified the effect on the beam profile. We calculated ks using the Jaffe plot and two-voltage method (TVM) by varying the measurement conditions, adding k_s,_rel, _off-ax to the beam profile, and comparing the changes via local gamma analysis. The central value of k_s increased with X-ray energy, and the effect become more pronounced when the measurement depth is varied. For the beam profile with high energy and a field size of 40 × 40 cm², the results of the local gamma analysis are lower than the reference value. At the maximum dose depth, the results are poor, even when the field size is 30× 30 cm². At 40× 40 cm², the results are lower than the reference value even when the criteria are further relaxed. Our results indicate that k_s differs depending on the measurement method, and thus, k_s,_rel,_off-ax should be considered when measuring beam profiles with field sizes larger than 30 × 30 cm².

DOI： 10.51083/radiatenvironmed.12.2_99

CiNii Books

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：MDPI AG  

Deep inspiration breath-hold (DIBH) is an excellent technique to reduce the incidental radiation received by the heart during radiotherapy in patients with breast cancer. However, DIBH is costly and time-consuming for patients and radiotherapy staff. In Asian countries, the use of DIBH is restricted due to the limited number of patients with a high mean heart dose (MHD) and the shortage of radiotherapy personnel and equipment compared to that in the USA. This study aimed to develop, evaluate, and compare the performance of ten machine learning algorithms for predicting MHD using a patient’s body mass index and single-slice CT parameters to identify patients who may not require DIBH. Machine learning models were built and tested using a dataset containing 207 patients with left-sided breast cancer who were treated with field-in-field radiotherapy with free breathing. The average MHD was 251 cGy. Stratified repeated four-fold cross-validation was used to build models using 165 training data. The models were compared internally using their average performance metrics: F2 score, AUC, recall, accuracy, Cohen’s kappa, and Matthews correlation coefficient. The final performance evaluation for each model was further externally analyzed using 42 unseen test data. The performance of each model was evaluated as a binary classifier by setting the cut-off value of MHD ≥ 300 cGy. The deep neural network (DNN) achieved the highest F2 score (78.9%). Most models successfully classified all patients with high MHD as true positive. This study indicates that the ten models, especially the DNN, might have the potential to identify patients who may not require DIBH.

DOI： 10.3390/curroncol30080537

PubMed

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Magnetic resonance (MR) images require a process known as windowing for optimizing the display conditions. However, the conventional windowing process often fails to achieve the preferred display conditions for observers due to various factors. This study proposes a novel framework for predicting the preferred windowing parameters for each observer using Bayesian statistical modeling. MR images obtained from 1000 patients were divided into training and test sets at a 7:3 ratio. The image intensity and windowing parameters were standardized using previously reported methods. Bayesian statistical modeling was utilized to predict the windowing parameters preferred by three MR imaging (MRI) operators. The performance of the proposed framework was evaluated by assessing the mean relative error (MRE), mean absolute error (MAE), and Pearson's correlation coefficient (ρ) of the test set. In addition, the naive method, which presumes that the average value of the windowing parameters for each acquisition sequence and body region in the training set is optimal, was also used for comparison. Three MRI operators and three radiologists conducted visual assessments. The mean MRE, MAE, and ρ values for the window level and width (WL/WW) in the proposed framework were 12.6 and 13.9, 42.9 and 85.4, and 0.98 and 0.98, respectively. These results outperformed those obtained using the naive method. The visual assessments revealed no significant differences between the original and predicted display conditions, indicating that the proposed framework accurately predicts individualized windowing parameters with the additional advantages of robustness and ease of use. Thus, the proposed framework can effectively predict the windowing parameters preferred by each observer.

DOI： 10.1016/j.heliyon.2023.e19038

Scopus

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

BACKGROUND: Computed tomography (CT) angiography (CTA) is a non-invasive imaging method used to detect arteries and examine various brain diseases. When CTA is performed for follow-up or postoperative evaluation, reproducibility of vessel delineation is required. A reproducible and stable contrast enhancement can be achieved by manipulating the factors affecting it. Previous studies have investigated several factors that alter the contrast enhancement of arteries. However, no reports establishing the effect of different operators on contrast enhancement exist. PURPOSE: To assess the differences between inter-operator arterial contrast enhancement in cerebral CTA using Bayesian statistical modeling. METHODS: Image data were obtained using a multistage sampling method from the cerebral CTA scans of patients who underwent the process between January 2015 and December 2018. Several Bayesian statistical models were developed, and the objective variable was the mean CT number of the bilateral internal carotid arteries after contrast enhancement. The explanatory variables were sex, age, fractional dose (FD), and the operator's information. The posterior distributions of the parameters were computed via Bayesian inference using the Markov chain Monte Carlo (MCMC) method, with the Hamiltonian Monte Carlo method employed as the algorithm. The posterior predictive distributions were computed using the posterior distributions of the parameters. Finally, the differences between inter-operator arterial contrast enhancement on the CT number in cerebral CTA were estimated. RESULTS: The posterior distributions showed that all parameters representing the difference between operators included zero at the 95% credible intervals (CIs). The maximum mean difference between inter-operator CT number in the posterior predictive distribution was only 12.59 Hounsfield units (HUs). CONCLUSIONS: The Bayesian statistical modeling results suggest that contrast enhancement of cerebral CTA examination between operator-to-operator differences in postcontrast CT number was small compared to those within-operator differences resulting from factors not considered in the model.

DOI： 10.1002/mp.16549

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Diffusion kurtosis (DK) imaging (DKI), a type of restricted diffusion-weighted imaging, has been reported to be useful for tumor diagnoses in clinical studies. We developed a software program to simultaneously create DK images with apparent diffusion coefficient (ADC) maps and conducted an initial clinical study. Multi-shot echo-planar diffusion-weighted images were obtained at b-values of 0, 400, and 800 sec/mm2 for simple DKI, and DK images were created simultaneously with the ADC map. The usefulness of the DK image and ADC map was evaluated using a pixel analysis of all pixels and a median analysis of the pixels of each case. Tumor and normal tissues differed significantly in both pixel and median analyses. In the pixel analysis, the area under the curve was 0.64 for the mean kurtosis (MK) value and 0.77 for the ADC value. In the median analysis, the MK value was 0.74, and the ADC value was 0.75. The MK and ADC values correlated moderately in the pixel analysis and strongly in the median analysis. Our simple DKI system created DK images simultaneously with ADC maps, and the obtained MK and ADC values were useful for differentiating head and neck tumors from normal tissue.

DOI： 10.18926/AMO/65492

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.meddos.2023.01.008

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Hirosaki University Press.  

We validated the calculation accuracies and times between the pencil beam algorithm (PBA) and the Monte Carlo (MC) algorithm in the new proton pencil beam scanning system. Thirty-three (homogeneous phantom) and three (heterogeneous phantom) uniform-dose plans were verified for cubic targets. These plans were calculated using the PBA and five MC statistical uncertainties of 0.3%, 0.5%, 1.0%, 1.5%, and 2.0%. We also evaluated the required dose calculation times per beam with the statistical analysis. Then, eight clinically realistic beams were validated as the end-toend test. The dose differences of 0.3% and 0.5% uncertainty MC plans were satisfied our tolerance (< ±3.0%). All five uncertainty MC plans improved at least the average/minimum gamma score from 93.8%/33.5% to 98.5%/88.9% for homogeneous (2%/2 mm) and 96.7%/83.9% to 98.8%/94.1% for heterogeneous (3%/3 mm) than PBA plans. However, the average calculation times of 0.3% and 0.5% uncertainties in MC plans were 15.5 and 5.8 times longer than in PBA plans (p < 0.001). The endto-end tests satisfied the acceptable with a statistical uncertainty of MC below 0.5%. Although the dose calculation times would be significantly increased, we suggest that the statistical uncertainty of MC below 0.5% is appropriate for clinical use with PBS plans.

DOI： 10.51083/radiatenvironmed.12.1_53

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Spandidos Publications  

DOI： 10.3892/etm.2023.11808

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担当区分：最終著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study aimed to evaluate the clinical beam commissioning results and lateral penumbra characteristics of our new pencil beam scanning (PBS) proton therapy using a multi-leaf collimator (MLC) calculated by use of a commercial Monte Carlo dose engine. Eighteen collimated uniform dose plans for cubic targets were optimized by the RayStation 9A treatment planning system (TPS), varying scan area, modulation widths, measurement depths, and collimator angles. To test the patient-specific measurements, we also created and verified five clinically realistic PBS plans with the MLC, such as the liver, prostate, base-of-skull, C-shape, and head-and-neck. The verification measurements consist of the depth dose (DD), lateral profile (LP), and absolute dose (AD). We compared the LPs and ADs between the calculation and measurements. For the cubic plans, the gamma index pass rates (γ-passing) were on average 96.5% ± 4.0% at 3%/3 mm for the DD and 95.2% ± 7.6% at 2%/2 mm for the LP. In several LP measurements less than 75 mm depths, the γ-passing deteriorated (increased the measured doses) by less than 90% with the scattering such as the MLC edge and range shifter. The deteriorated γ-passing was satisfied by more than 90% at 2%/2 mm using uncollimated beams instead of collimated beams except for three planes. The AD differences and the lateral penumbra width (80%-20% distance) were within ±1.9% and ± 1.1 mm, respectively. For the clinical plan measurements, the γ-passing of LP at 2%/2 mm and the AD differences were 97.7% ± 4.2% on average and within ±1.8%, respectively. The measurements were in good agreement with the calculations of both the cubic and clinical plans inserted in the MLC except for LPs less than 75 mm regions of some cubic and clinical plans. The calculation errors in collimated beams can be mitigated by substituting uncollimated beams.

DOI： 10.1002/acm2.13817

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

The evaluation of the entrance surface dose (ESD) ensures safe radiation doses for X-ray imaging patients. The air kerma free-in-air value used to estimate ESD may be affected by those X-rays that scatter from the scatterer placed behind the chamber at the time of measurement, thereby leading to assessment errors. Therefore, the influence of scattered radiation on air kerma measurements was investigated. Monte Carlo simulations were performed for various detector-to-scatterer distances and scatterer materials. The simulation results were compared with actual measurements to confirm the simulation accuracy. The source-chamber distance was set to 50 and 100 cm for the experimental measurements and simulation, respectively, and the chamber-scatterer distance was varied. The Monte Carlo simulation results reproduced the actual measurements with an accuracy of 3.5%. The effect of backscattering varied with the tube voltage and irradiation field size. The effect was observed in the order of prominence for the following scatterer materials: water-equivalent phantom, acrylic, concrete, lead, and iron. Furthermore, this effect decreased exponentially with increasing chamber-scatterer distance. For a field size of 10 × 10 cm2, the finite-distance backscatter factor decreased with an increasing chamber-scatterer distance for all materials. The cause of backscattering in diagnostic X-ray energy regions differs depending on the scatterer material, as well as the photon energy and field size. Backscattering decreases exponentially as the distance between the detector and scatterer increases.

DOI： 10.1007/s12194-021-00641-3

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Volumetric-modulated arc therapy (VMAT) requires highly accurate control of multileaf collimator (MLC) movement, rotation speed of linear accelerator gantry, and monitor units during irradiation. Pretreatment validation and monitoring of these factors during irradiation are necessary for appropriate VMAT treatment. Recently, a gantry mounted transmission detector "Delta4 Discover® (D4D)" was developed to detect errors in delivering doses and dose distribution immediately after treatment. In this study, the performance of D4D was evaluated. Simulation plans, in which the MLC position was displaced by 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm from the clinically used original plans, were created for ten patients who received VMAT treatment for prostate cancer. Dose deviation (DD), distance-to-agreement (DTA), and gamma index analysis (GA) for each plan were evaluated by D4D. These results were compared to the results (DD, DTA and GA) measured by Delta4 Phantom + (D4P). We compared the deviations between the planned and measured values of the MLC stop positions A-side and B-side in five clinical cases of prostate VMAT during treatment and measured the GA values. For D4D, when the acceptable errors for DD, DTA, and GA were determined to be ≤3%, ≤2 mm, and ≤3%/2 mm, respectively, the minimum detectable errors in the MLC position were 2.0, 1.5, and 1.5 mm based on DD, DTA, and GA respectively. The corresponding minimum detectable MLC position errors were 2.0, 1.0, and 1.5 mm, respectively, for D4P. The deviation between the planned and measured position of MLC stopping point of prostate VMAT during treatment was stable at an average of -0.09 ± 0.05 mm, and all GA values were above 99.86%. In terms of delivering doses and dose distribution of VMAT, error detectability of D4D was comparable to that of D4P. The transmission-type detector "D4D" is thus suitable for detecting delivery errors during irradiation.

DOI： 10.1002/acm2.13260

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Reports on irradiation dose distribution in breast cancer radiotherapy with sufficient sample size are limited in Asian patients. Elucidating dose distribution in Asian patients is particularly important as their breast volume differs compared to patients in Europe and North America. Here, we examined dose distribution in the irradiation field relative to breast volume for three irradiation methods historically used in our facility. We investigated the influence of breast volume on each irradiation method for Asian women. A total of 573 women with early-stage breast cancer were treated with breast-conserving surgery and adjuvant radiotherapy. Three methods were compared: wedge (W), field-in-field (FIF), and wedge-field-in-field (W-FIF). In patients with small breast volume, FIF decreased low- and high-dose areas within the planning target volume, and increased optimal dose area more than W. In patients with medium and large breast volumes, FIF decreased high-dose area more than W. The absolute values of correlation coefficients of breast volume to low-, optimal-, and high-dose areas and mean dose were significantly lower in FIF than in W. The correlation coefficients of V107% were 0.00 and 0.28 for FIF and W, respectively. FIF is an excellent irradiation method that is less affected by breast volume than W in Asian breast cancer patients.

DOI： 10.18926/AMO/62225

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

During radiation therapy, incident radiation oblique to the skin surface is high and may cause severe skin damage. Understanding the dose of radiation absorbed by the skin is important for predicting skin damage due to radiation. In this study, we used a high-energy (4 MV) X-ray system and an optically stimulated luminescence dosimeter (OSLD) that was developed for personal exposure dosimetry. We determined the dose variation and angular dependence, which are the characteristics of a small OSLD required to derive the calculation formula for the oblique surface dose. The dose variation was determined using the coefficient of variation. The maximum coefficient of variation for 66 small-field OSLDs was 1.71%. The angular dependence, obtained from the dose ratio of the dosimeter in the vertical direction, had a maximum value of 1.37. We derived a new equation in which the oblique surface dose can be calculated within the error range of -7.7-5.1%.

DOI： 10.18926/AMO/60801

PubMed

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The aim of this study is to evaluate the patient positioning uncertainty in noncoplanar stereotactic radiosurgery or stereotactic radiotherapy (SRS/SRT) for intracranial lesions with the frameless 6D ExacTrac system. In all, 28 patients treated with SRS/SRT of 70 treatment plans at our institution were evaluated in this study. Two X-ray images with the frameless 6D ExacTrac system were first acquired to correct (XC) and verify (XV) the patient position at a couch angle of 0º. Subsequently, the XC and XV images were also acquired at each planned couch angle for using noncoplanar beams to detect position errors caused by rotating a couch. The translational XC and XV shift values at each couch angle were calculated for each plan. The percentages of the translational XC shift values within 1.0 mm for each planned couch angle for using noncoplanar beams were 77.86%, 72.26%, and 98.47% for the lateral, longitudinal, and vertical directions, respectively. Those within 2.0 mm were 98.22%, 97.96%, and 99.75% for the lateral, longitudinal, and vertical directions, respectively. The maximum absolute values of the translational XC shifts among all planned couch angles for using noncoplanar beams were 2.69, 2.45, and 2.17 mm for the lateral, longitudinal, and vertical directions, respectively. The overall absolute values of the translational XV shifts were less than 1.0 mm for all directions except for one case in the longitudinal direction. The patient position errors were detected after couch rotation for using noncoplanar beams, and they exceeded a planning target volume (PTV) margin of 1.0-2.0 mm used commonly in SRS/SRT treatment. These errors need to be corrected at each planned couch angle, or the PTV margin should be enlarged.

DOI： 10.1002/acm2.12820

PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.18926/AMO/56167

Web of Science

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担当区分：最終著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

The aim of this study was to quantify the effect of multi-leaf collimators (MLCs) with different leaf widths on the planning of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT). Toward this objective, dose transmission through a high-definition 120-leaf MLC (HD120MLC) and 120-leaf Millennium MLC (M120MLC) was investigated, using it with a test case and clinical case studies. In test case, studies with IMRT and VMAT plans, the difference in MLC leaf width had a limited effect on planning target volumes (PTVs). Organs at risk (OARs) were more affected by a reduction in dose transmission through the MLC than by a reduction in MLC leaf width. The results of the test case studies and clinical case studies were mostly similar. In the latter, the different MLCs had no effect on the PTV regardless of the treatment method; however, the HD120MLC plans achieved dose reductions to OARs similar to or larger than the dose reduction of the M120MLC plans. The similar results of the test case and clinical case studies showed that despite a limitation of the irradiation field size, the HD120MLC plans were superior.

DOI： 10.1007/s11604-017-0661-8

Web of Science

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

The aim of this study is to investigate the dosimetric uncertainty of stochastic noise and the post-irradiation density growth for reflective-type radiochromic film to obtain the appropriate dose from the exactly controlled film density. Film pieces were irradiated with 6-MV photon beams ranging from 0 to 400cGy. The pixel values (PVs) of these films were obtained using a flatbed scanner at elapsed times of 1min to 120h between the end of irradiation and the film scan. The means and standard deviations (SDs) of the PVs were calculated. The SDs of the converted dose scale, usd, and the dose increases resulting from the PV increases per ±29min at each elapsed time, utime, were computed. The combined dose uncertainties from these two factors, uc, were then calculated. A sharp increase in the PV occurred within the first 3h after irradiation, and a slight increase continued from 3h to 120h. usd was independent of post-irradiation elapsed time. Sharp decreases in utime were obtained within 1h after irradiation, and slight decreases in utime were observed from 1 to 24h after irradiation. uc first decreased 1h after irradiation and remained constant afterward. Assuming that the post-irradiation elapsed times of all of the related measurements are synchronized within ±29min, the elapsed time should be at least 1h in our system. It is important to optimize the scanning protocol for each institution with consideration of the required measurement uncertainty and acceptable latency time.

DOI： 10.1016/j.ejmp.2016.07.091

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

BACKGROUND/AIM: The aims of this study were to evaluate the cell survival uncertainty distribution of radiation and to assess the accuracy of predictions of tumor response by using three different in vitro experimental cell cultures with radiosensitizers (including etanidazole). MATERIALS AND METHODS: Using EMT6 cells and X-rays, the cell survival fraction was obtained from 15, 34, and 21 different experiments under normoxic, hypoxic, and hypoxic-plus-radiosensitizer culture, respectively. RESULTS: The α coefficients were 0.257 ± 0.188, 0.078 ± 0.080, and 0.182 ± 0.116 Gy(-1), respectively. The β coefficients were 0.0159 ± 0.0208, 0.0076 ± 0.0113, and 0.0062 ± 0.0077 Gy(-2), respectively. The α coefficient and the dose that killed half of the clonogens population (D50) were significantly different between normoxic cell and hypoxic cell cultures (p<0.01), respectively. The use of radiosensitizers under hypoxic conditions improved radiosensitivity. CONCLUSION: Our results suggest that parameter value distributions are required for biophysical modeling of applications for radiotherapy.

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

In multileaf collimator (MLC)-based intensity modulated radiation therapy (IMRT), the dose is influenced by the uncertainty of MLC driving control. In this study, we examined the influence of MLC driving control accuracy on dose evaluation (gamma analysis) by evaluating 60-day MLC driving control accuracy (stationary positioning accuracy and positioning reproducibility) once a week as well as measuring IMRT dose distribution. The MLC positioning accuracy accompanied variation over time and tended to expand by 0.1 to 0.15 mm in one week and about 1 mm in 60 days. In terms of reproducibility, errors were within 0.2 mm for more than 95%. For prostate IMRT, when MLC stationary positioning accuracy was around 1 mm, no significant difference was observed in the pass rate in gamma analysis. Therefore, the results suggest that regular maintenance by setting a permissible value determined by the MLC positioning accuracy test can be an effective indicator in the future for maintaining the safety of IMRT.

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

PURPOSE: Radiographic film is generally used for inspection of dose distribution in intensity modulated radiation therapy (IMRT) at many institutions. However, the distribution of filmless systems can be expected to be used increasingly in the future. Therefore, we confirmed the utility of radiochromic film by comparing it with radiographic film that does not need an automatic processor. RESULT: Difference in does measured by radiographic film and radiochromic film tended to increase in the low does area, but it was limited in a range of 1.5%. CONCLUSION: When the dose distribution was verified in a highly accurate radiation therapy such as IMRT, the results suggested that radiochromic film can be useful in addition to radiographic film.

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/s0167-8140(12)73156-0

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：(株)医学書院  

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その他リンク： https://search.jamas.or.jp/index.php?module=Default&action=Link&pub_year=2009&ichushi_jid=J00269&link_issn=&doc_id=20090507170018&doc_link_id=0905156&url=https%3A%2F%2Fkango-sakuin.nurse.or.jp%2Fnid%2F0905156&type=%8D%C5%90V%8A%C5%8C%EC%8D%F5%88%F8Web&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00014_1.gif

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE INC  

Purpose: OncoSeed is delivered in a sterile environment in the form of a cartridge, so it is impractical to resterilize and reload seeds after calibration. We investigated a new method using an imaging plate dosimetry system to characterize all seeds in the OncoSeed cartridge in a sterile environment.Methods and Materials: Seeds within the cartridge were placed on an imaging plate, and the imaging plate irradiated. To remove scatter radiation, and improve spatial resolution of seed images, we used X-ray parallel cross grids. The irradiated imaging plate was scanned using a Bio-imaging Analyzer System, and radioactivity intensities of seed images were given in counts. Counts could be translated to profiles, and each seed within the cartridge was analyzed.Results: Results showed a good correlation between counts and total radioactivity of the seeds within the cartridge. Thus, using a least-squares line, it was possible to characterize a cartridge with unknown apparent activity. By analyzing the profiles, it was possible not only to detect a miscalibrated seed in the cartridge from its relative difference in counts, but also to identify its position in the cartridge. No significant changes in counts were seen between sterile and nonsterile environments.Conclusion: Using an imaging plate dosimetry system, all seeds in a cartridge could be characterized in a sterile environment. (c) 2006 Elsevier Inc.

DOI： 10.1016/j.ijrobp.2006.05.052

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）  

PURPOSE: Recent years, CT on rail system was reported to be useful as a tool for image-guided radiotherapy (IGRT). This system was clinically developed with the aim of stereotactic irradiation (STI) for brain, lung, liver, prostate and other sites. Quality assurance and quality control (QC) is an important issue in CT on rail system to assure geometric accuracies. The purpose of this study is to estimate the geometric accuracies of our CT on rail system using a detachable micro-multi leaf collimator (mMLC) with new type radiochromic films. Carrying out our original QC program, translational errors, setup reproducibility, beam misalignment and beam characteristics were evaluated. METHODS AND MATERIALS: We have studied with CT on rail system (FOCAL unit, Toshiba Medical systems, Tokyo, Japan) and mMLC unit (Accuknife, Direx Inc., Tokyo, Japan). We have developed original alignment phantom and small steel markers (2 mm phi) were implanted on its surface at certain intervals. Firstly, we have evaluated the accuracy of self-moving CT gantry and CT resolutions for cranio-caudal directions by changing slice thickness. And then using the phantom, we have measured the accuracy and reproducibility of geometric isocenter of the linac side and the CT gantry side by scanning the phantom. We have also measured the geometric changes of the common treatment couch by weight-loaded test (up to 135 kgw). To estimate dosimetric and geometric accuracies with the mMLC unit, the misalignment of the beam axes (gantry, collimator and couch rotation axis), mMLC leaf positions, and dose distributions for the verification plan were measured with new type GafChromic films (GafChromic-RTQA, ISP Inc., USA) and cylindrical phantom. The dose characteristics of the GafChromic film were also evaluated. RESULTS: The reproducibility of the self-moving CT gantry have a good agreement within 1 mm. Weight-load test have shown a good reliability within 2 mm at the common treatment couch. The translational precision of the common treatment couch was 0.0 +/- 0.1 mm at linac side and -0.2 +/- 0.5 mm at CT gantry side. The misalignments of beam axes have been kept within 0.4 mm at maximum. Gap test have shown the accuracies of the mMLC leaf positions, which is needed to keep within 1 mm by a routine calibration. CONCLUSIONS: To practice quality control program for the FOCAL unit and the mMLC unit is essential for a regular interval to reduce systematic errors. New type radiochromic film would be useful for a verification tool as alternative to conventional film.

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

PURPOSE: To reduce setup error and intrafractional movement in head-and-neck treatment, a real-time tumor tracking radiotherapy (RTRT) system was used with the aid of gold markers implanted in a mouthpiece. METHODS AND MATERIALS: Three 2-mm gold markers were implanted into a mouthpiece that had been custom made for each patient before the treatment planning process. Setup errors in the conventional immobilization system using the shell (manual setup) and in the RTRT system (RTRT setup) were compared. Eight patients with pharyngeal tumors were enrolled. RESULTS: The systematic setup errors were 1.8, 1.6, and 1.1 mm in the manual setup and 0.2, 0.3, and 0.3 mm in the RTRT setup in right-left, craniocaudal, and AP directions, respectively. Statistically significant differences were observed with respect to the variances in setup error (p <0.001). The systematic and random intrafractional errors were maintained within the ranges of 0.2-0.6 mm and 1.0-2.0 mm, respectively. The rotational systematic and random intrafractional errors were estimated to be 2.2-3.2 degrees and 1.5-1.6 degrees , respectively. CONCLUSIONS: The setup error and planning target volume margin can be significantly reduced using an RTRT system with a mouthpiece and three gold markers.

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記述言語：日本語   出版者・発行元：一般社団法人 日本放射線腫瘍学会  

【背景】強度変調放射線治療（IMRT）は標的体積の三次元形状に合わせて線量集中度を高めることが可能である．頭頸部領域においては耳下腺線量低減を主目的としてIMRTが行われている．一般的にIMRTでは治療時間が長いこと，および線量勾配が照射野内に存在することより，従来の放射線治療と比較し，より精度の高いセットアップが必要とされる．<br>【目的】われわれの施設で開発した動体追跡放射線治療装置の 2 方向Ｘ線透視を頭頸部癌に対するIMRTのセットアップに用い，その安全性を検証する．<br>【対象・方法】2002年 5 月から2004年10月まで当院でIMRTを施行した 9 例．PTV-marginは 3 mmで治療を行った．口腔内乾燥症はVAS（visual analogue scale）を用い自覚症状で評価した．<br【結果】全ての患者が治療を完遂した．観察期間の中央値17カ月で，全ての患者が局所再発および遠隔転移なく生存している．治療前，治療開始後 1～4カ月，5～8カ月，9～12月および13カ月以降のVAS平均値は 9.6mm，51.4mm，55.1mm，39.7mm，47.9 mmであった． 唾液腺機能温存を目的としたIMRTの安全性が確認された．

DOI： 10.11182/jastro.18.191

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Purpose: We evaluated a self-color developing sheet-type film for the detection of dead seeds in I-125 permanent implant therapy for prostate cancer. Materials and Methods: As a preliminary study, we irradiated X-rays to a self-developing reflection-type sheet film and created a relational curve between absorbed dose and film density. I-125 seeds were placed on a film and the approximate absorbed dose of 1-125 was calculated from the relational curve of X-rays. A cartridge in which a dead seed was loaded among 10 I-125 seeds was placed on the film and the detectability of the dead seed was evaluated. Results: Using the relational curve of X-rays, it was possible to measure the approximate absorbed dose of I-125 seeds and to easily detect a dead seed at a glance. Using sterilized film, it was possible to detect a dead seed. Conclusion: The self-developing film method is feasible for the detection of a dead seed in a cartridge without re-sterilization of seeds.

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Although patient exposure has been increasing in recent years, few institutions have dosimeters and are able to ascertain patients' exposure dose. Internationally, however, it is necessary to adopt safety levels for patient exposure doses, and guidance levels have been introduced. Therefore, the need for measurement in areas of x-ray diagnosis has been increasing. As a result, several societies concerned with radiation dose have been endeavoring to establish a calibration system of radiation measurement and a dosimeter calibration system, which are the basics of radiation protection. Ten regional centers for standardization of doses in x-ray diagnosis were established and have begun trials relating to dosimeter cross calibration. Our institution, as one of these centers, has instituted a trial. In this study, the cross-calibration field, the reliability of the cross-calibration skill of our regional center, and the standard uncertainty of cross calibration were investigated. As a consequence of the investigation, it was determined that our cross-calibration field follows the protocol of the Japanese Society of Radiological Technology, the difference between calibration factor/cross calibration factor obtained by JQA and our regional center is within 2.5%, and the expanded uncertainty of our cross calibration is about 7.2% (k=2).

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

The output factor of high-energy X-ray machines varies with collimation. According to Khan's theory, collimator and phantom scatter factors contribute to total scatter factor. For precise X-ray irradiation, the two factors need to be taken into consideration. To obtain proper factors, we made two original polystyrene cylindrical mini-phantoms. These phantoms are both 4 cm in diameter and have a pinpoint ion chamber placed at a depth of 5 cm and 10 cm, respectively. Using a 6 MV X-ray machine, collimator scatter factors were calculated for various field arrangements (i.e., field sizes ranging from 4 cm x 4 cm to 40 cm x 40 cm at isocenter). To determine if calculated values were appropriate, we measured point doses of 20 X-ray irradiation patterns using a Farmer-type ion chamber with a water equivalent phantom at depths of 5 cm and 10 cm, respectively. Two hundred MUs were irradiated to the above-mentioned depths for each field. Based on the measured doses, variations were obtained for four calculation methods. Accounting for 1) secondary collimator (jaw) setting, 2) blocked field (multi-leaf collimator) setting, 3) Khan's theory using a 5 cm mini-phantom, and 4) Khan's theory using a 10 cm mini-phantom. Dose variations in each method of calculation were as follows: 1) +0.3 to +10.2% (mean, +2.0 to +3.2%) , 2) -2.3 to 0.0% (mean, -0.8 to -0.6%), 3) 0.0 to +1.5% (mean, +0.1 to +0.3%), 4) 0.0 to +1.4% (mean, -0.1 to +0.1%).

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE INC  

Purpose: To test the accuracy of a system for correcting for the rotational error of the clinical target volume (CTV) without having to reposition the patient using three fiducial markers and two orthogonal fluoroscopic images. We call this system "three-dimensional conformal setup" (3D-CSU).
Methods and Materials: Three 2.0-mm gold markers are inserted into or adjacent to the CTV. On the treatment couch, the actual positions of the three markers are calculated based on two orthogonal fluoroscopies crossing at the isocenter of the linear accelerator. Discrepancy of the actual coordinates of gravity center of three markers from its planned coordinates is calculated. Translational setup error is corrected by adjustment of the treatment couch. The rotation angles (alpha, beta, gamma) of the coordinates of the actual CTV relative to the planned CTV are calculated around the lateral (x), craniocaudal (y), and anteroposterior (z) axes of the planned CTV. The angles of the gantry head, collimator, and treatment couch of the linear accelerator are adjusted according to the rotation of the actual coordinates of the tumor in relation to the planned coordinates. We have measured the accuracy of 3D-CSU using a static cubic phantom.
Results: The gravity center of the phantom was corrected within 0.9 +/- 0.3 mm (mean +/- SD), 0.4 +/- 0.2 mm, and 0.6 +/- 0.2 mm for the rotation of the phantom from 0-30 degrees around the x, y, and z axes, respectively, every 5 degrees. Dose distribution was shown to be consistent with the planned dose distribution every 10 degrees of the rotation from 0-30 degrees. The mean rotational error after 3D-CSU was -0.4 +/- 0.4 (mean +/- SD), -0.2 +/- 0.4, and 0.0 +/- 0.5 degrees around the x, y, and z axis, respectively, for the rotation from 0-90 degrees.
Conclusions: Phantom studies showed that 3D-CSU is useful for performing rotational correction of the target volume without correcting the position of the patient on the treatment couch. The 3D-CSU will be clinically useful for tumors in structures such as paraspinal diseases and prostate cancers not subject to large internal organ motion. (C) 2004 Elsevier Inc.

DOI： 10.1016/j.ijrobp.2004.05.042

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE INC  

Purpose: Synchronization of the techniques in real-time tumor-tracking radiotherapy (RTRT) and intensity-modulated RT (IMRT) is expected to be useful for the treatment of tumors in motion. Our goal was to estimate the feasibility of the synchronization from the viewpoint of excessive dose resulting from the use of fluoroscopy.
Methods and Materials: Using an ionization chamber for diagnostic X-rays, we measured the air kerma rate, surface dose with backscatter, and dose distribution in depth in a solid phantom from a fluoroscopic RTRT system. A nominal 50-120 kilovoltage peak (kVp) of X-ray energy and a nominal 1-4 ms of pulse width were used in the measurements.
Results: The mean +/- SD air kerma rate from one fluoroscope was 238.8 +/- 0.54 mGy/h for a nominal pulse width of 2.0 ms and nominal 100 kVp of X-ray energy at the isocenter of the linear accelerator. The air kerma rate increased steeply with the increase in the X-ray beam energy. The surface dose was 28-980 mGy/h. The absorbed dose at a 5.0-cm depth in the phantom was 37-58% of the peak dose. The estimated skin surface dose from one fluoroscope in RTRT was 29-1182 mGy/h and was strongly dependent on the kilovoltage peak and pulse width of the fluoroscope and slightly dependent on the distance between the skin and isocenter.
Conclusion: The skin surface dose and absorbed depth dose resulting from fluoroscopy during RTRT can be significant if RTRT is synchronized with IMRT using a multileaf collimator. Precise estimation of the absorbed dose from fluoroscopy during RT and approaches to reduce the amount of exposure are mandatory. (C) 2004 Elsevier Inc.

DOI： 10.1016/j.ijrobp.2004.04.028

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/s0360-3016(03)00095-6

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掲載種別：研究論文（学術雑誌）  

Head-and-Neck is a suitable site for IMRT. Organ motion can be more easily controlled with immobilization devices as compared to other sites such as lung and abdomen. There are various critical organs, for which tolerance doses are different (i.e., 40Gy for the spinal cord, 25-30Gy for the parotid glands, etc. etc.). Recent reports on IMRT are impressive in that salivary function is preserved without compromising tumor control. With rapidly developing technology, this new treatment could be available in many hospitals in the near future. However, we must proceed to do IMRT with caution; the technique requires high-level quality assurance (ideally with experienced medical physicists), which requirement is not necessarily met here in Japan. Thus, deep understanding of both physical and biological aspects of IMRT, and perhaps sound judgment also, will promise good-quality radiotherapy leading to the well-being for suffering patients.

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記述言語：日本語   出版者・発行元：一般社団法人 日本医学物理学会  

Recent external radiotherapy requires precise localization of the target because advance in diagnostic imaging has made it possible to visualize a tiny tumor which would be curable with focused high dose irradiation. However, tumors in respiratory and bowel organs have been difficult to be given the high dose because of 1 to 3 cm movement during delivery of irradiation. Respiratory-gating techniques have been used with medical linear accelerators and particle therapy machines. Real-time tumortracking radiotherapy has been realized using fluoroscopic x-rays, internal gold-markers, and pattern recognition technology. Advantage and disadvantage of each gating technique have been realized. Active breath control method would be a cost-effective way of precise treatment without gating. More work is required to find the relationship between abdominal wall and internal movement of the tumor in many respiratorygating radiotherapy and between the internal markers and target volume in real-time tracking radiotherapy.

DOI： 10.11323/jjmp2000.21.1_17

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00091159113?from=CiNii

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The advancement of irradiation technology has increased the demand for quality control of radiation therapy equipment. Consequently, the number of quality control items and required personnel have also increased. However, differences in the proportion of qualified personnel to irradiation techniques have caused bias in quality control systems among institutions. To standardize the quality across institutions, researchers should conduct mutual quality control by analyzing the quality control data of one institution at another institution and comparing the results with those of their own institutions. This study uses failure mode and effects analysis (FMEA) to identify potential risks in 12 radiation therapy institutions, compares the results before and after implementation of mutual quality control, and examines the utility of mutual quality control in risk reduction. Furthermore, a cost-effectiveness factor is introduced into FMEA to evaluate the utility of mutual quality control.

DOI： 10.1007/s12194-024-00857-z

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

The increase in high-precision radiation therapy, particularly volumetric-modulated arc therapy (VMAT), has increased patient numbers and expanded treatment sites. However, a significant challenge in VMAT treatment planning is the inconsistent plan quality among different planners and facilities. This study explored the use of dose-volume histogram (DVH) prediction tools to address these disparities, specifically focusing on RapidPlan (Varian Medical Systems) and PlanIQ (Sun Nuclear). RapidPlan predicts achievable DVHs and automatically generates optimization objectives. While it has demonstrated organ-at-risk (OAR) dose reduction benefits, the quality of the plan used to build its model significantly affects its predictions. On the other hand, PlanIQ offers ease of use and does not require prior model-building. Five planners participated in this study, each creating two treatment plans: one referencing RapidPlan and the other using PlanIQ. The planners had the freedom to adjust parameters while referencing the DVH predictions. The plans were evaluated using "Plan Quality Metric" (PQM) scores to assess the planning target volume excluding the rectum and OARs. The results revealed that RapidPlan-referenced plans often outperformed PlanIQ-based plans, with less interplanner variability. PlanIQ played a pivotal role in the construction of the RapidPlan model. This study is the first to compare plans generated by multiple planners using both tools. This study provides insights into optimizing treatment planning by considering the characteristics of both RapidPlan and PlanIQ.

DOI： 10.1016/j.meddos.2024.02.002

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：KEK High Energy Accelerator Research Organization  

Brachytherapy planning is performed based on the AAPM TG-43U1 protocol. The protocol is normalized in the air-kerma strength. The absorbed dose of air and the air-kerma are regarded as the same in a state where the charged particle equilibrium is established. However both dose not match within some distances from the radiation source. we investigate the air and air-kerma strength using EGS5 simulations. Determinations of the air-kerma strength are methods of using the mass energy-transfer coefficient and integrating the electron kinetic energy directly. These two results we were compared.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：KEK High Energy Accelerator Research Organization  

Monte Carlo simulations can be approximated considering the environment of actual measurement in detail. However, it can not be completely corrected by simulations. Because there are some uncertainties on the actual measurement. For example, the amount of charge using the ionization chamber is used to convert the dosimeter measurement of the absorbed dose by the exposure calibration factor for cobalt-60 and the absorbed dose conversion factor. In the simulation, absorbed dose is seeking direct energy per unit mass of water, on the other hand, it is converted to energy per unit mass of water from the charge amount in the air by the exposure calibration factor for cobalt-60 and the absorbed dose conversion factor in actual measurement. We suspect these factors containing uncertainties. Focusing on the absorbed dose conversion factor, we investigated it by EGS5. We specialized microSelectron-HDR v2 as a radiation source and PTW TN30013 as an ionization chamber.

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記述言語：日本語   出版者・発行元：国立病院総合医学会  

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記述言語：日本語   出版者・発行元：(公社)日本診療放射線技師会  

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記述言語：日本語   出版者・発行元：放射線生物研究会  

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記述言語：英語   出版者・発行元：(公社)日本放射線技術学会  

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記述言語：日本語   出版者・発行元：(一財)津山慈風会津山中央病院  

【目的】近年、高エネルギーX線による前立腺癌の高精度放射線外部照射ではガントリを回転させながら強度や照射野形状を変えて最適な線量分布を形成する強度変調回転放射線治療法(以下、VMAT法)が可能となっている。一方、当院ではエネルギー強度の異なる数十種類の陽子線ビームを段階的に照射するラスタースキャニング法(以下、RS法)による強度変調陽子線治療(IMPT)を2018年5月より開始した。本研究では、前立腺癌患者のうち前立腺および精嚢への照射を含む高リスク症例に対するRS法とVMAT法の違いによる線量分布比較を行ったので報告する。【方法】対象は局所進行前立腺癌高リスク症例10例とし、治療計画装置RayStation(RaySearch社製)によって治療計画を立案した。その際、臨床標的体積(以下、CTV)は、前立腺および被膜外浸潤部位、精嚢を含む領域とした。次に両照射法の線量分布評価のためにCTVに対して全周5mmを拡大したPTV5を作成した。リスク臓器(以下、OAR)には直腸、膀胱、両側大腿骨頭部を定義し、直腸、膀胱に対しては内側3mmの直腸壁と膀胱壁を輪郭作成した。処方線量はCTVに対してRS法では70GyE、VMAT法では70Gyをそれぞれ体積の50%が照射される線量(RS法ではD50GyE、VMAT法ではD50Gy)とした。RS法はガントリ角度90度と270度の左右対向2門照射、VMAT法はガントリ角度181度から179度の範囲での回転照射の治療計画を立案した。線量基準はCTVに対し、最小線量(以下、Dmin)がRS法では66.5GyE、VMAT法では66.5Gyを超えることとし、OARの線量は極力低減した。その後、線量体積ヒストグラム(以下、DVH)でCTVはDminおよび体積の98%、2%がそれぞれ照射される線量(以下、D98、D2)、線量均一性を示すHomogeneity index(以下、HI)を算出した。さらに、PTV5はV95、D98、最大線量(以下、Dmax)および体積の95%照射線量(以下、D95)を算出し、直腸壁、膀胱壁はDmaxおよび10〜70GyE(Gy)が照射される体積(以下、V10〜V70)を5GyE(Gy)間隔で比較した。また、すべての輪郭において平均線量を求めた。二群間の有意差検定はウィルコクソン符号付順位検定を用いた。【結果】RS法はVMAT法に比べてCTVのD98およびD2に有意な差が見られ、HIが向上した(p<0.01)。PTV5に関しては、D98とDmaxでは有意な差が見られたが(D98:p<0.05、Dmax:p<0.01)、V95およびD95では差が見られなかった(V95:p=0.333、D95:p=0.114)。OARに関しては、直腸壁のV10〜V35およびV60〜V70でRS法は線量が軽減された(p<0.05)。また、Dmaxにおいても線量が軽減された(p<0.05)。膀胱壁の線量はV10〜V25(低線量域)ではRS法が低くなり、V45〜V70(中・高線量域)ではVMAT法が低くなった(p<0.05)。Dmaxにおいては差が見られなかった(p=0.386)。平均線量に関しては、CTVおよびPTV5では有意な差は見られず、直腸および膀胱ではRS法が低くなった。しかし、左右大腿骨頭部の平均線量はRS法が高くなった(p<0.05)。【結論】RS法はVMAT法と比べてPTV5への線量は同等と考えられた。しかし、CTVに対してより均一に照射することが可能であった。また、RS法はCTVに近接する直腸壁に関する線量軽減が可能であるが、膀胱壁に関する中・高線量域の線量や大腿骨頭部の平均線量は高くなる場合があることが示唆され、治療計画作成時には注意が必要であった。(著者抄録)

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記述言語：英語   出版者・発行元：(公社)日本放射線技術学会  

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記述言語：英語   出版者・発行元：ELSEVIER SCI LTD  

The aim of this study is to investigate the dosimetric uncertainty of stochastic noise and the postirradiation density growth for reflective-type radiochromic film to obtain the appropriate dose from the exactly controlled film density. Film pieces were irradiated with 6-MV photon beams ranging from 0 to 400 cGy. The pixel values (PVs) of these films were obtained using a flatbed scanner at elapsed times of 1 min to 120 h between the end of irradiation and the film scan. The means and standard deviations (SDs) of the PVs were calculated. The SDs of the converted dose scale, u(sd), and the dose increases resulting from the PV increases per +/- 29 min at each elapsed time, u(time), were computed. The combined dose uncertainties from these two factors, u(c), were then calculated. A sharp increase in the PV occurred within the first 3 h after irradiation, and a slight increase continued from 3 h to 120 h. usd was independent of post-irradiation elapsed time. Sharp decreases in utime were obtained within 1 h after irradiation, and slight decreases in utime were observed from 1 to 24 h after irradiation. uc first decreased 1 h after irradiation and remained constant afterward. Assuming that the post-irradiation elapsed times of all of the related measurements are synchronized within +/- 29 min, the elapsed time should be at least 1 h in our system. It is important to optimize the scanning protocol for each institution with consideration of the required measurement uncertainty and acceptable latency time. (C) 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ejmp.2016.07.091

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：WILEY  

DOI： 10.1118/1.4956867

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：WILEY  

DOI： 10.1118/1.4956168

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：WILEY  

DOI： 10.1118/1.4956517

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記述言語：英語   出版者・発行元：SPRINGER  

In this study, we compared the dose impact of the heterogeneity caused by rectal gas using two methods of treatment planning for intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT).
In addition to the structure set used for the standard treatment plan, we created a structure set for evaluation for each patient. These sets were transferred to the same isocenter as the respective treatment plans for IMRT and VMAT that were to become the standard. Values were then recalculated.
During the standard prostatic IMRT and VMAT treatment planning, all study participants met dose restrictions in place at our hospital. Dose restrictions were fulfilled in treatment plans for evaluation, excluding those with a clinical target volume (CTV) of V (100 %) and planning target volume (PTV) of D (95) when the rectum was excluded. However, in treatment plans for evaluation, IMRT was shown to have a higher concordance rate with standard treatment plans than VMAT.
If rectal gas is present during either IMRT or VMAT, a dose decrease will occur in relation to CTV and PTV, suggesting that a plan does not eliminate adverse effects on organs at risk.

DOI： 10.1007/s11604-015-0481-7

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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DOI： 10.6009/jjrt.2014_JSRT_70.2.163

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At present, every manufacturer of intensity modulated radiation therapy (IMRT) equipment uses multi-leaf collimators (MLCs); however, each company's intensity modulation methods and dose calculation algorithms differ. This study used four typical radiation treatment planning systems (RTPSs) employed domestically for prostate IMRT plans to carry out 15 case studies by one planner based on the dose limits at this clinic. The results were used to compare the differences, if any, in RTPS treatment plans. With prostate IMRT plans, an overlap area exists between the PTV and the rectum. For this reason, while observing dose limits of 60-75 Gy (within the dose tolerated by the rectum), securing uniformity and concentration of dose is essential to create the most appropriate treatment plan for the PTV and other targets. Although each RTPS uses different planning methods, it was generally possible to observe this clinic's dose limits by adjusting the parameter values. When identical beam data is used, it is possible to create similar treatment plans.

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記述言語：英語   出版者・発行元：John Wiley and Sons Ltd  

Purpose: A 3.0-T MRI phantom (called the CAGN-3.0T phantom) having human-equivalent relaxation times and human-equivalent conductivity was developed. Methods: The ingredients of the phantom are carrageenan (as a gelatinizer), agarose (as a T2-relaxation modifier), GdCl3 (as a T1-relaxation modifier), NaCl (as a conductivity modifier), and NaN3 (as an antiseptic). Numerous samples with varying concentrations of agarose, GdCl3, and NaCl were prepared, and T 1 and T2 values were measured using 3.0-T MRI. Results: The T1 values of the CAGN-3.0T phantom were unaffected by NaCl, while the T2 values were only slightly affected. Based on the measured data, empirical formulae were devised to express the relationships between the concentrations of agarose, GdCl3, and NaCl and the relaxation times. The formula for expressing the conductivity of the CAGN-3.0T phantom was obtained. Conclusions: By adjustments to the concentrations of agarose, GdCl3, and NaCl, the relaxation times and conductivity of almost all types of human tissues can be simulated by CAGN-3.0T phantoms. The phantoms have T1 values of 395-2601 ms, T2 values of 29-334 ms, and conductivity of 0.27-1.26 S/m when concentrations of agarose, GdCl3, and NaCl are varied from 0 to 2.0 w/w%, 0 to 180 μmol/kg, and 0 to 0.7 w/w%, respectively. The CAGN-3.0T phantom has sufficient strength to replicate the torso without using reinforcing agents, and can be cut with a knife into any shape. © 2013 American Association of Physicists in Medicine.

DOI： 10.1118/1.4790023

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記述言語：日本語   出版者・発行元：公益社団法人 日本放射線技術学会  

DOI： 10.6009/jjrt.2013_JSRT_69.7.761

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その他リンク： https://search.jamas.or.jp/link/ui/2013320922

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記述言語：日本語   出版者・発行元：Japanese Society of Radiological Technology  

The purpose of this study was to clinically evaluate the automatic outline extraction properties using general-purpose deformable image registration (DIR) software for the head and neck region. To this end, we evaluated the following: (1) the difference between manual outline extraction carried out by a radiation therapy specialist and automatic outline extraction using the DIR software, and (2) the precision of the automatic outline extraction for the diachronic figure change and change in the organ shape. The manually-extracted outline and that extracted using the DIR software closely resembled each other at 0.70. Further, in the same case, the automatic outline extraction precision of the DIR software was greater at about 0.80. Our findings suggest DIR software to be useful for lessening the work involved in outline extraction.

DOI： 10.6009/jjrt.2013_JSRT_69.11.1250

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その他リンク： https://jlc.jst.go.jp/DN/JALC/10025901763?from=CiNii

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS  

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：WILEY  

DOI： 10.1118/1.3612218

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：WILEY  

DOI： 10.1118/1.3612437

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DOI： 10.6009/jjrt.67.497

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）  

DOI： 10.1118/1.3468943

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記述言語：英語   出版者・発行元：SPRINGER  

Purpose. The aim of this study was to evaluate distortion of the tabletop in a diagnostic positron emission tomography-computed tomography (PET-CT) system to determine its suitability for planning radiotherapy positioning.
Materials and methods. Distortion of the tabletop was compared among PET-CT, lineac CT, and CT simulator systems. A phantom or angiography catheter was fixed to the tabletop and imaged after iron plate weight loading. The acquired images were analyzed using radiotherapy planning software. Distortion of the tabletop was measured based on the displayed coordinates.
Results. Sinking represented the greatest distortion of the tabletop in all systems. Using the same baseline, the maximum sinking were -0.4, -0.2, and +0.4 cm, respectively. The distortion of the tabletop in the PET-CT system was more similar to that in the lineac CT than in the CT simulator system.
Conclusion. Distortion of the tabletop in a diagnostic PET-CT system may be within the acceptable range to allow it use for planning radiotherapy positioning.

DOI： 10.1007/s11604-009-0398-0

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DOI： 10.6009/jjrt.66.525

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記述言語：英語   出版者・発行元：SPANDIDOS PUBL LTD  

Diffusion-weighted magnetic resonance imaging (MRI) is frequently used clinically, and is available for the whole-body screening for tumors. The exact mechanism by which the apparent diffusion coefficient (ADC) value decreases in tumorous tissue remains unclear, although various theories have been proposed, including intracellular and extracellular factor theories. It is impossible to distinguish each factor in the intracellular and extracellular spaces as the source of MR signal generation by means of conventional comparison between MR images and pathological specimens. Other factors which have been reported to affect ADC include cellularity and cellular edema of human tissues, and temperature of phantoms at the time of measurement. We employed a new technique that enables cellular MR imaging using a newly developed bio-phantom containing a living culture tumor cell line, Jurkat-N1. We investigated possible reasons for observed decreases in ADC values for tumors, and we considered the contribution of both the intracellular and extracellular space to such a decrease. The ADC values of the bio-phantom increased with increasing heat exposure from 27 to 45 degrees C. ADC values also increased after the destruction by sonication of tumor cell membranes. ADC values decreased as cellularity increased in the bio-phantorn. ADC values decreased due to cellular edema caused by a low salt concentration in the bio-phantom. Changes in pressure in the bio-phantom had no effect on the observed ADC values. We calculated both the intracellular ADC and extracellular ADC values using the ADC values, cellularity, and cellular volume of Jurkat-N1 cells in the bio-phantom. The extracellular ADC values in the bio-phantom were estimated to be lower than the ADC value of distilled water. These results indicate that not only intracellular ADC values, but also extracellular ADC values contribute to the determination of the ADC values of bio-phantoms. This is the first report to have examined the contribution of intracellular and extracellular space on the ADC values of bio-phantoms containing cultured tumor cells.

DOI： 10.3892/or_00000484

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：ELSEVIER SCIENCE INC  

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記述言語：日本語   出版者・発行元：公益社団法人日本放射線技術学会  

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記述言語：日本語   出版者・発行元：公益社団法人日本放射線技術学会  

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS  

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記述言語：日本語   出版者・発行元：(公社)日本医学放射線学会  

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記述言語：日本語   出版者・発行元：公益社団法人日本放射線技術学会  

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記述言語：日本語   出版者・発行元：公益社団法人日本放射線技術学会  

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS  

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記述言語：日本語   出版者・発行元：公益社団法人日本放射線技術学会  

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE INC  

Purpose: To reduce setup error and intrafractional movement in head-and-neck treatment, a real-time tumor tracking radiotherapy (RTRT) system was used with the aid of gold markers implanted in a mouthpiece.
Methods and Materials: Three 2-mm gold markers were implanted into a mouthpiece that had been custom made for each patient before the treatment planning process. Setup errors in the conventional immobilization system using the shell (manual setup) and in the RTRT system (RTRT setup) were compared. Eight patients with pharyngeal tumors were enrolled.
Results: The systematic setup errors were 1.8, 1.6, and 1.1 nun in the manual setup and 0.2, 0.3, and 0.3 mm in the RTRT setup in right-left, craniocaudal, and AP directions, respectively. Statistically significant differences were observed with respect to the variances in setup error (p &lt; 0.001). The systematic and random intrafractional errors were maintained within the ranges of 0.2-0.6 mm and 1.0-2.0 mm, respectively. The rotational systematic and random intrafractional errors were estimated to be 2.2-3.2 degrees and 1.5-1.6 degrees, respectively.
Conclusions: The setup error and planning target volume margin can be significantly reduced using an RTRT system with a mouthpiece and three gold markers. (c) 2006 Elsevier Inc.

DOI： 10.1016/j.ijrobp.2005.11.038

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：ELSEVIER SCIENCE INC  

DOI： 10.1016/j.ijrobp.2006.05.052

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE INC  

PURPOSE: OncoSeed is delivered in a sterile environment in the form of a cartridge, so it is impractical to resterilize and reload seeds after calibration. We investigated a new method using an imaging plate dosimetry system to characterize all seeds in the OncoSeed cartridge in a sterile environment. METHODS AND MATERIALS: Seeds within the cartridge were placed on an imaging plate, and the imaging plate irradiated. To remove scatter radiation, and improve spatial resolution of seed images, we used X-ray parallel cross grids. The irradiated imaging plate was scanned using a Bio-imaging Analyzer System, and radioactivity intensities of seed images were given in counts. Counts could be translated to profiles, and each seed within the cartridge was analyzed. RESULTS: Results showed a good correlation between counts and total radioactivity of the seeds within the cartridge. Thus, using a least-squares line, it was possible to characterize a cartridge with unknown apparent activity. By analyzing the profiles, it was possible not only to detect a miscalibrated seed in the cartridge from its relative difference in counts, but also to identify its position in the cartridge. No significant changes in counts were seen between sterile and nonsterile environments. CONCLUSION: Using an imaging plate dosimetry system, all seeds in a cartridge could be characterized in a sterile environment.

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記述言語：日本語   出版者・発行元：放射線生物研究会  

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その他リンク： http://search.jamas.or.jp/link/ui/2006148201

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：ELSEVIER IRELAND LTD  

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：ELSEVIER IRELAND LTD  

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記述言語：日本語   出版者・発行元：公益社団法人 日本放射線技術学会  

DOI： 10.6009/jjrt.kj00004028462

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その他リンク： https://search.jamas.or.jp/link/ui/2005297832

記述言語：日本語  

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Purpose: To improve set-up accuracy in head and neck radiotherapy, a real-time tumor tracking radiotherapy (RTRT) system and a mouthpiece with gold markers has been developed. The reduction in set-up error was estimated in this study. Method and Materials: Four patients with oropharyngeal carcinoma were enrolled in this study. Three 2-mm gold markers were implanted into a mouthpiece, which was designed specifically for each patient. The center of gravity of the three markers and its relationship to the tumor was registered using computed tomography (CT) and 3-D treatment planning system. Translational set-up error was calculated by comparing the actual and planned position of the three markers. Set-up errors by conventional manual immobilization and the RTRT system were compared. Results: In manual set-up, median set-up errors along right-left (RL), cranio-caudal (CC), antero-posterior (AP) directions, and three-dimensional (3D) vector length were 0.5, -0.8, 1.3, and 4.1 mm, respectively (n=87). Systematic set-up errors were 2.8, 3.5, 0.6, and 1.9 mm (n=4). Random set-up errors were 2.6, 3.2, 1.7, and 1.9 mm. In RTRT set-up, translational set-up errors were 0.2, 0.3, -0.3, and 1.6 mm, respectively. Systematic set-up errors were 0.8, 0.8, 0.9, and 0.9 mm (n=4). Random set-up errors were 1.2, 1.5, 1.1, and 1.3 mm (n=92). Statistically significant difference (p<0.001) was seen in random set-up errors of x, y, and 3D vector between the two methods. Conclusion: Set-up errors were improved by using RTRT system with a mouthpiece with three gold markers in head and neck radiotherapy (p<0.001). This system will be useful to improve the accuracy of intensity-modulated radiotherapy (IMRT), which requires meticulous set-up.

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：ELSEVIER SCIENCE INC  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会-北海道部会  

線量測定の精度向上を目的としてEDR2フィルムを用いた線量測定に影響を与える様々な誤差要因について検討した.濃度線量変換テーブル作成法,X線エネルギー量,測定深度による誤差を測定したところ,1枚のフィルムに照射する照射野数が多くなると線量に関わらず誤差が大きくなり,照射野数5×5cmとして6照射野以上作成すると測定誤差は5%を超えた.フィルムの線量特性はエネルギーや深さに強い影響を受け,測定誤差は低エネルギーほど大きく,校正深(5cm)では最小であるが,校正深より深くなるに従って大きくなった.EDR2フィルムを用いた線量測定では照射条件,深さ,エネルギー依存性,現像処理,濃度の読み取りなどを行った場合,測定誤差を3%以内に抑制可能であることが示唆された.線量測定,特に絶対線量測定に使用する時にはフィルムの特性を十分に熟知しておく必要があると考えられた

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記述言語：日本語   出版者・発行元：公益社団法人 日本放射線技術学会  

DOI： 10.6009/jjrt.kj00000922184

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その他リンク： https://search.jamas.or.jp/link/ui/2004049715

記述言語：日本語   出版者・発行元：公益社団法人 日本放射線技術学会  

DOI： 10.6009/jjrt.kj00003111072

CiNii Article

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その他リンク： https://search.jamas.or.jp/link/ui/2002233403

記述言語：日本語   出版者・発行元：公益社団法人 日本放射線技術学会  

DOI： 10.6009/jjrt.kj00003110263

CiNii Article

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その他リンク： https://search.jamas.or.jp/link/ui/1998255552

開催年月日： 2022年9月16日 - 2022年9月18日

記述言語：日本語   会議種別：口頭発表（一般）  

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開催年月日： 2022年4月14日 - 2022年4月17日

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開催年月日： 2021年12月18日 - 2021年12月19日

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開催年月日： 2021年12月10日 - 2021年12月12日

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開催年月日： 2021年11月12日 - 2021年11月14日

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開催年月日： 2021年10月16日

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開催年月日： 2021年6月4日 - 2021年6月7日

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開催年月日： 2021年6月4日 - 2021年6月7日

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開催年月日： 2021年4月15日 - 2021年4月18日

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開催年月日： 2020年10月1日 - 2020年10月3日

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開催年月日： 2020年5月23日 - 2020年6月14日

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開催年月日： 2019年3月

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開催年月日： 2019年

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記述言語：日本語   会議種別：口頭発表（一般）  

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記述言語：英語   会議種別：口頭発表（一般）  

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記述言語：日本語   会議種別：口頭発表（一般）  

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記述言語：英語  

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