Yusuke Suzuki, Motoharu Sasaki, Yuji Nakaguchi, Takeshi Kamomae, Yuki Kanazawa, Yuki Tominaga, Sohma Sawada, Yuto Yamaji and Hitoshi Ikushima : Efficient Knowledge-based Planning Model Construction in Institutions with Limited Cases Using Plan Quality Metrics, Radiological Physics and Technology, 2025.
(要約)
Prostate cancer volumetric modulated arc therapy (VMAT) planning often faces challenges in the construction of high-quality RapidPlan models when the number of cases is limited. In the present study, we retrospectively scored 90 VMAT plans using Plan Quality Metrics (PQM) and Adjusted PQM (APQM) and constructed 12 RapidPlan models from various combinations of cases with high and low PQM or APQM scores, each trained on 30 cases. Six representative models were selected for a detailed evaluation, including the P_H model based on the top 30 PQM cases and the AP_H model based on the top 30 APQM cases. All models were tested on ten independent cases that exhibited varying planning difficulties. The overall plan quality was assessed using PQM scores and dose-volume histogram (DVH) metrics for targets and organs at risk (OARs). The P_H model demonstrated significantly higher PQM scores than all other models (p < 0.05), with superior consistency and improved OAR sparing. Although the AP_H model performed well, the results were inconsistent. In challenging cases, the P_H model maintained a stable quality and outperformed both manual plans and APQM-based models. These findings indicated that case selection based on the actual clinical plan quality (PQM) is more effective than selection based on theoretical dose distributions (APQM) for building robust RapidPlan models, particularly when data are limited. This method is practical for small institutions and could be further improved by standardizing the PQM-based selection criteria and optimizing priority settings to enhance the generalizability and clinical utility of knowledge-based planning.
Yushi Wakisaka, Yuki Tominaga, Keith M Furutani and Teiji Nishio : Dosimetric and Temporal Evaluation of Dynamic Collimation with Multi-Leaf Collimator in Scanned Proton Therapy: A Planning Study, Physica Medica, 137, 105088, 2025.
(要約)
The MELTHEA V proton therapy system incorporates a beam nozzle capable of both passive scattering and active scanning, featuring a multi-leaf collimator (MLC). This study evaluates the dosimetric and temporal efficiency of dynamic collimation using the universal MLC with the scanning method. Three MLC configurations were defined: (1) nMLC - no MLC use; (2) sMLC - static leaf positioning across all energy layers; and (3) dMLC - dynamic leaf positioning changing with each energy layer. Since the treatment planning system does not support dMLC natively, it was implemented via scripting. First, various MLC margins were evaluated through phantom simulations. Then, using a representative margin, treatment plans for nine liver cancer cases were assessed for each MLC configuration. Irradiation delay time was simulated considering monitor units, dose rates, and the time characteristics of the irradiation system. Phantom simulations demonstrated that an MLC margin of 0.5ς (with ς representing the in-medium spot size) effectively reduced the surrounding dose while preserving target coverage. For liver cancer cases, the average conformity index at the 50 % isodose line for nMLC, sMLC, and dMLC was 3.27 ± 0.60, 2.61 ± 0.28, and 2.28 ± 0.24, respectively. The mean doses in a 10-mm ring surrounding the target were 54.9 ± 2.5, 48.3 ± 3.9, and 41.4 ± 3.8 Gy, respectively. The average irradiation delay time of the dMLC was 8.4 %. The dMLC demonstrated enhanced dosimetric performance compared to nMLC and sMLC, with minimal irradiation time delays, making it suitable for clinical liver cancer treatment.
Yuki Tominaga, Yushi Wakisaka, Takahiro Kato, Masaya Ichihara, Keisuke Yasui, Motoharu Sasaki, Masataka Oita and Teiji Nishio : Commissioning of respiratory-gated 4D dynamic dose calculations for various gating widths without spot timestamp in proton pencil beam scanning, Medical Physics, 52, 8, e18026, 2025.
(要約)
Proton pencil beam scanning (PBS) is susceptible to dose degradation because of interplay effects on moving targets. For cases of unacceptable motion, respiratory-gated (RG) irradiation is an effective alternative to free breathing (FB) irradiation. However, the introduction of RG irradiation with larger gate widths (GW) is hindered by interplay effects, which are analogous to those observed with FB irradiation. Accurate estimation of interplay effects can be performed by recording spot timestamps. However, our machine lacks this feature, making it imperative to find an alternative approach. Thus, we developed an RG 4-dimensional dynamic dose (RG-4DDD) system without spot timestamps. This study aimed to investigate the accuracy of calculated doses from the RG-4DDD system for PBS plans with varying breathing curves, amplitudes, and periods for 10%-50% GW. RG-4DDDs were reconstructed using in-house developed software that assigned timestamps to individual spots, integrated start times for spills with breathing curves, and utilized deformable registrations for dose accumulation. Three cubic verification plans were created using a heterogeneous phantom. Additionally, typical liver and lung cases were employed for patient plan validation. Single- and multi-field-optimized (SFO and IMPT) plans (ten beams in total) were created for the liver and lung cases in a homogeneous phantom. Lateral profile measurements were obtained under both motion and no-motion conditions using a 2D ionization chamber array (2D-array) and EBT3 Gafchromic films on the CIRS dynamic platform. Breathing curves from the cubic plans were used to assess nine patterns of sine curves, with amplitudes of 5.0-10.0 mm (10.0-20.0 mm target motions) and periods of 3-6 sec. Patient field verifications were conducted using a representative patient curve with an average amplitude of 6.4 mm and period of 3.2 sec. Additional simulations were performed assuming a ± 10% change in assigned timestamps for the dose rate (DR), spot spill (0.08-s), and gate time delay (0.1-s) to evaluate the effect of parameter selection on our 4DDD models. The 4DDDs were compared with measured values using the 2D gamma index and absolute doses over that required for dosing 95% of the target. The 2D-array measurements showed that average gamma scores for the reference (no motion) and 4DDD plans for all GWs were at least 99.9 ± 0.2% and 98.2 ± 2.4% at 3%/3 mm, respectively. The gamma scores of the 4DDDs in film measurements exceeded 95.4% and 92.9% at 2%/2 mm for the cubic and patient plans, respectively. The 4DDD calculations were acceptable under DR changes of ±10% and both spill and gate time delays of ±0.18 sec. For the 4DDD plan using all GWs for all measurement points, the absolute point differences for all validation plans were within ±5.0% for 99.1% of the points. The RG-4DDD calculations (less than 50% GW) of the heterogeneous and actual patient plans showed good agreement with measurements for various breathing curves in the amplitudes and periods described above. The proposed system allows us to evaluate actual RG irradiation without requiring the ability to record spot timestamps.
Yuya Miyasaka, Yuki Tominaga, Yushi Wakisaka and Isamu Maeshima : Survey and profile data study on particle therapy technology in Japan, Japanese Journal of Radiology, 2025.
(要約)
The purpose of this study is to report profile data on the technical elements of Japanese particle therapy facilities. We requested a survey on the following four technical elements; (1) facilities and systems, (2) immobilization device and treatment planning CT, (3) patient specific QA, and (4) patient positioning. Responses were received from 21 facilities. The most commonly used accelerators were synchrotrons, which were used in 17 facilities (81.0%). The lowest available energy was widely distributed between 55.6 MeV/u and 290 MeV/u, but the maximum energy was often around 240 MeV/u for proton beams and 430 MeV for carbon ion beams. Of all treatment rooms, passive irradiation accounted for 57.7% (30 rooms), layer stacking irradiation for 7.7% (4 rooms), and scanning irradiation for 32.7% (17 rooms). Shell-type immobilization devices were most commonly used in the head and neck region, and vacuum bags were most commonly used in the thoracic to caudal regions. Lateral dose profile measurement was the most commonly used patient specific QA method. The most commonly used detector was the ionization chamber or ionization chamber-type planar detector. 2D X-ray radiography was the most commonly used in patient positioning. Marker matching was commonly used for the prostate and liver, bone matching for the head and neck and lungs, and tumor matching was used only sparingly. The results of this study may clarify current issues in particle therapy technology and provide data to guide further technology development.
Keisuke Yasui, Miuna Hayashi, Shiryu Otsuka, Toshiyuki Toshito, Chihiro Omachi, Masaya Ichihara, Riki Oshika, Yuki Tominaga, Hiromi Baba, Hidetoshi Shimizu and Naoki Hayashi : Postal dosimetry audit for scanning proton beam using radiophotoluminescence glass dosimeter: A multicenter pilot study, Medical Physics, 52, 6, 4996-5004, 2025.
(要約)
Accurate dosimetry is important in radiotherapy, and all equipment used for radiotherapy shoud be audited by an independent external dose audit. Radiophotoluminescence glass dosimeter (RPLD) has excellent characteristics and is widely used for postal dose audit; however, postal dose audit for proton therapy using RPLD has not been established. This study aims to develop a postal dose audit procedure for scanning proton beams using RPLD, estimate uncertainties, and conduct a multicenter pilot study to validate the methodology. A postal toolkit was developed and a postal dose audit procedure for RPLD measurements of scanning proton beams was established in cooperation with several facilities that employ various accelerators, irradiation equipment, and treatment planning systems (TPS) for clinical use. Based on basic and previous studies, an uncertainty budget was developed for estimating relative uncertainty and pilot studies were conducted at each site. A method for postal dose audits was developed in a multicenter collaboration to develop an approach suitable for implementation across multiple facilities. The relative response of 60 RPLDs for scanning proton beam examined in this study was 1.00 ± 1.28% mean ± standard deviation. The combined relative standard uncertainty of postal dosimetry for scanning proton beams using the RPLD was 2.97% (k = 1). Under the reference condition, the maximum differences between the ionization chamber measurement (IC) and TPS, RPLD and TPS, and RPLD and IC were 0.97, 1.88, and 2.12%, respectively. The maximum differences between the RPLD and ionization chamber for plateau measurements at 3 cm depth using single-energy and non-reference conditions were 11.31 and 4.02%, respectively. We established a procedure for the postal dose audits of proton beams using RPLD and presented the results of a multicenter pilot study. By standardizing the reference conditions, the dosimetry uncertainty was estimated at 2.92%. The results demonstrated the feasibility of performing an independent third-party dose audit of scanning proton beams using RPLD, and for such postal dose audits for proton beams, the irradiation conditions should be standardized to reduce uncertainties. These results are expected to contribute to the development of proton beams.
Yushi Wakisaka, Masashi Yagi, Yuki Tominaga, Shinichi Shimizu, Teiji Nishio and Kazuhiko Ogawa : Nuclear interaction correction based on dual-energy computed tomography in carbon-ion radiotherapy, Physics in Medicine and Biology, 70, 5, 2025.
(要約)
Objective.Accurate dose predictions are crucial to maximizing the benefits of carbon-ion therapy (CIT). Carbon beams incident on the human body cause nuclear interactions with tissues, resulting in changes in the constituent nuclides and leading to dose errors that are conventionally corrected using conventional single-energy computed tomography (SECT). Dual-energy computed tomography (DECT) has frequently been used for stopping power estimation in particle therapy and is well suited for correcting nuclear reactions because of its detailed body-tissue elemental information. This study proposes a correction method for the absolute dose in CIT that considers changes in nuclide composition resulting from nuclear reactions with body tissues, as a novel application of DECT.Approach.The change in dose associated with nuclear reactions is determined by correcting each integrated depth dose component of the carbon beam using a nuclear interaction correction factor. This factor is determined based on the stopping power, mass density, and nuclear interaction cross-section in body tissue. The stopping power and mass density were calculated using established methods, whereas the nuclear interaction cross-section was newly defined through a conversion equation derived from the effective atomic number.Main results.Nuclear interaction correction factors and corrected doses were determined for 85 body tissues with known compositions, comparing them with existing SECT-based methods. The root-mean-square errors of the SECT- and DECT-based nuclear interaction correction factors relative to theoretical values were 0.66% and 0.39%, respectively.Significance.This indicates a notable enhancement in the estimation accuracy with DECT. The dose calculations in uniform body tissues derived from SECT showed slight over-correction in adipose and bone tissues, whereas those based on DECT were almost consistent with theoretical values. Our proposed method demonstrates the potential of DECT for enhancing dose calculation accuracy in CIT, complementing its established role in stopping power estimation.
(キーワード)
Heavy Ion Radiotherapy / Tomography, X-Ray Computed / Humans / Radiotherapy Dosage
Motoharu Sasaki, Yuji Nakaguchi, Takeshi Kamomae, Akira Tsuzuki, Sohma Sawada, Kohki Shibuya, Masataka Oita, Masahide Tominaga, Yuki Tominaga and Hitoshi Ikushima : Comparative analysis of two dose-volume histogram prediction tools for treatment planning in volumetric-modulated arc therapy: A multi-planner study, Medical Dosimetry, 49, 3, 271-275, 2024.
(要約)
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.
Yuki Tominaga, Masaki Suga, Mikuni Takeda, Yuki Yamamoto, Takashi Akagi, Takahiro Kato, Sunao Tokumaru, Michinori Yamamoto and Masataka Oita : Comparing interplay effects in scanned proton therapy of lung cancer: Free breathing with various layer and volume rescanning versus respiratory gating with different gate widths., Physica Medica, 120, 103323, 2024.
(要約)
PURPOSE: We investigated interplay effects and treatment time (TT) in scanned proton therapy for lung cancer patients. We compared free-breathing (FB) approaches with multiple rescanning strategies and respiratory-gating (RG) methods with various gating widths to identify the superior irradiation technique. METHODS: Plans were created with 4/1, 2/2, and 1/4 layered/volume rescans of FB (L4V1, L2V2, and L1V4), and 50%, 30%, and 10% gating widths of the total respiratory curves (G50, G30, and G10) of the RG plans with L4V1. We calculated 4-dimensional dynamic doses assuming a constant sinusoidal curve for six irradiation methods. The reconstructed doses per fraction were compared with planned doses in terms of dose differences in 99% clinical-target-volume (CTV) (ΔD99%), near-maximum dose differences (ΔD2%) at organs-at-risk (OARs), and TT. RESULTS: The mean/minimum CTV ΔD99% values for FB were -1.0%/-4.9%, -0.8%/-4.3%, and -0.1%/-1.0% for L4V1, L2V2, and L1V4, respectively. Those for RG were -0.3%/-1.7%, -0.1%/-1.0%, and 0.0%/-0.5% for G50, G30, and G10, respectively. The CTV ΔD99% of the RGs with less than 50% gate width and the FBs of L1V4 were within the desired tolerance (±3.0%), and the OARs ΔD2% for RG were lower than those for FB. The mean TTs were 90, 326, 824, 158, 203, and 422 s for L4V1, L2V2, L1V4, G50, G30, and G10, respectively. CONCLUSIONS: FB (L4V1) is the most efficient treatment, but not necessarily the optimal choice due to interplay effects. To satisfy both TT extensions and interplay, RG with a gate width as large as possible within safety limits is desirable.
Yuki Tominaga, Masaki Suga, Mikuni Takeda, Yuki Yamamoto, Takashi Akagi, Takahiro Kato, Sunao Tokumaru, Michinori Yamamoto and Masataka Oita : Dose-volume comparisons of proton therapy for pencil beam scanning with and without multi-leaf collimator and passive scattering in patients with lung cancer, Medical Dosimetry, 49, 1, 13-18, 2023.
(要約)
This study evaluated the dose distributions of proton pencil beam scanning (PBS) with/without a multileaf collimator (MLC) compared to passive scattering (PS) for stage I/II lung cancers. Collimated/uncollimated (PBS+/PBS-) and PS plans were created for 20 patients. Internal-clinical-target-volumes (ICTVs) and planning-target-volumes (PTVs) with a 5 mm margin were defined on the gated CTs. Organs-at-risk (OARs) are defined as the normal lungs, spinal cord, esophagus, and heart. The prescribed dose was 66 Gy relative-biological-effectiveness (RBE) in 10 fractions at the isocenter and 50% volume of the ICTVs for the PS and PBS, respectively. We compared the target and OAR dose statistics from the dose volume histograms. The PBS+ group had a significantly better mean PTV conformity index than the PBS- and PS groups. The mean dose sparing for PBS+ was better than those for PBS- and PS. Only the normal lung doses of PBS- were worse than those of PS. The overall performance of the OAR sparing was in the order of PBS+, PBS-, and PS. The PBS+ plan showed significantly better target homogeneity and OAR sparing than the PBS- and PS plans. PBS requires collimating systems to treat lung cancers with the most OAR sparing while maintaining the target coverage.
Yuki Tominaga, Masataka Oita, Junya Miyata and Takahiro Kato : Experimental validation of a 4D dynamic dose calculation model for proton pencil beam scanning without spot time stamp considering free-breathing motion., Medical Physics, 51, 1, 566-578, 2023.
(要約)
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.
Junya Miyata, Yuki Tominaga, Kazuto Kondo, Yasuaki Sonoda, Hideki Hanazawa, Mami Sakai, Satoshi Itasaka, Masataka Oita and Masahiro Kuroda : Dosimetric comparison of pencil beam scanning proton therapy with or without multi-leaf collimator versus volumetric-modulated arc therapy for treatment of malignant glioma, Medical Dosimetry, 48, 2, 105-112, 2023.
(要約)
This study aimed to examine the dosimetric effect of intensity-modulated proton therapy (IMPT) with a multi-leaf collimator (MLC) in treating malignant glioma. We compared the dose distribution of IMPT with or without MLC (IMPTMLC+ or IMPTMLC-, respectively) using pencil beam scanning and volumetric-modulated arc therapy (VMAT) in simultaneous integrated boost (SIB) plans for 16 patients with malignant gliomas. High- and low-risk target volumes were assessed using D2%, V90%, V95%, homogeneity index (HI), and conformity index (CI). Organs at risk (OARs) were evaluated using the average dose (Dmean) and D2%. Furthermore, the dose to the normal brain was evaluated using from V5Gy to V40Gy at 5 Gy intervals. There were no significant differences among all techniques regarding V90%, V95%, and CI for the targets. HI and D2% for IMPTMLC+ and IMPTMLC- were significantly superior to those for VMAT (p < 0.01). The Dmean and D2% of all OARs for IMPTMLC+ were equivalent or superior to those of other techniques. Regarding the normal brain, there was no significant difference in V40Gy among all techniques whereas V5Gy to V35Gy in IMPTMLC+ were significantly smaller than those in IMPTMLC- (with differences ranging from 0.45% to 4.80%, p < 0.05) and VMAT (with differences ranging from 6.85% to 57.94%, p < 0.01). IMPTMLC+ could reduce the dose to OARs, while maintaining target coverage compared to IMPTMLC- and VMAT in treating malignant glioma.
Yuki Tominaga, Masataka Oita, Takashi Akagi, Junya Miyata, Shuichi Harada, Tetsunori Matsuda and Masahiro Kuroda : Comparison of the Dose Calculation Accuracy between the Commercial Pencil Beam Algorithm and Various Statistical Uncertainties with Monte Carlo Algorithm in New Proton Pencil Beam Scanning System, Radiation Environment and Medicine, 12, 1, 53-64, 2023.
(要約)
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.
Yuki Tominaga, Yusuke Sakurai, Junya Miyata, Shuichi Harada, Takashi Akagi and Masataka Oita : Validation of pencil beam scanning proton therapy with multi-leaf collimator calculated by a commercial Monte Carlo dose engine., Journal of Applied Clinical Medical Physics, 23, 12, e13817, 2022.
(要約)
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.
(キーワード)
Humans / Radiotherapy Dosage / Phantoms, Imaging / Proton Therapy / Lipopolysaccharides / Radiotherapy Planning, Computer-Assisted / Monte Carlo Method
Soichi Sugiyama, Kuniaki Katsui, Yuki Tominaga, Takahiro Waki, Norihisa Katayama, Hidenobu Matsuzaki, Shin Kariya, Masahiro Kuroda, Kazunori Nishizaki and Susumu Kanazawa : Dose distribution of intensity-modulated proton therapy with and without a multi-leaf collimator for the treatment of maxillary sinus cancer: a comparative effectiveness study, Radiation Oncology, 14, 1, 209, 2019.
(要約)
Severe complications, such as eye damage and dysfunciton of salivary glands, have been reported after radiotherapy among patients with head and neck cancer. Complications such as visual impairment have also been reported after proton therapy with pencil beam scanning (PBS). In the case of PBS, collimation can sharpen the penumbra towards surrounding normal tissue in the low energy region of the proton beam. In the current study, we examined how much the dose to the normal tissue was reduced by when intensity-modulated proton therapy (IMPT) was performed using a multi-leaf collimator (MLC) for patients with maxillary sinus cancer. Computed tomography findings of 26 consecutive patients who received photon therapy at Okayama University Hospital were used in this study. We compared D2% of the region of interest (ROI; ROI-D2%) and the mean dose of ROI (ROI-mean) with and without the use of an MLC. The organs at risk (OARs) were the posterior retina, lacrimal gland, eyeball, and parotid gland. IMPT was performed for all patients. The spot size was approximately 5-6 mm at the isocenter. The collimator margin was calculated by enlarging the maximum outline of the target from the beam's eye view and setting the margin to 6 mm. All plans were optimized with the same parameters. The mean of ROI-D2% for the ipsilateral optic nerve was significantly reduced by 0.48 Gy, and the mean of ROI-mean for the ipsilateral optic nerve was significantly reduced by 1.04 Gy. The mean of ROI-mean to the optic chiasm was significantly reduced by 0.70 Gy. The dose to most OARs and the planning at risk volumes were also reduced. Compared with the plan involving IMPT without an MLC, in the dose plan involving IMPT using an MLC for maxillary sinus cancer, the dose to the optic nerve and optic chiasm were significantly reduced, as measured by the ROI-D2% and the ROI-mean. These findings demonstrate that the use of an MLC during IMPT for maxillary sinus cancer may be useful for preserving vision and preventing complications.
Yuki Tominaga, Yushi Wakisaka, Takahiro Kato, Masataka Oita, Robabeh Rahimi and Teiji Nishio : Improvements of lateral penumbra at various depth regions in scanned proton treatment system with a multi-leaf collimator: Dose verifications and plan comparisons, The 67th Annual Meeting & Exhibition of the American Association of Physicists in Medicine, Jul. 2025.
2.
Masato Horita, Ryo Tanokura, Yuki Tominaga, Takahiro Kato and Nobukazu Fuwa : Validation of four different dose calculation algorithms in a new type of scanned proton therapy system, The 67th Annual Meeting & Exhibition of the American Association of Physicists in Medicine, Jul. 2025.
3.
Yuki Tominaga, Takahiro Kato, Masataka Oita and Teiji Nishio : Experimental Validations of Two Different 4D Dynamic Dose Calculation Methods for Free Breathing in Proton Pencil Beam Scanning, The 66th Annual Meeting & Exhibition of the American Association of Physicists in Medicine, Jul. 2024.
4.
Yuki Tominaga, Masataka Oita, Junya Miyata, Yusuke Sakurai and Takashi Akagi : Experimental validation of model-based 4D dynamic doses calculated by a commercial treatment planning system in proton pencil beam scanning, The 59th Annual Conference of the Particle Therapy Co-Operative Group, Jun. 2021.
5.
Shun Fujiwara, Yuki Tominaga, Takayasu Haruna and Masataka Oita : Spot characteristic stability for utilizing the XRV-2000 scintillation detector in proton pencil beam scanning, PTCOG59, Jun. 2021.
6.
Takahiro Waki, Yuki Tominaga, Yasue Niwa, Hiroki Ihara, Dongcun Jin, Soichi Sugiyama, Takahiro Kawabata, Kuniaki Katsui, Mamoru Fujishima and Susumu Kanazawa : Proton therapy for prostate cancer: Comparison of acute toxicity between moderate-hypo and conventional fraction, ESTRO 38, Apr. 2019.
Yuki Tominaga, Yushi Wakisaka, Takahiro Kato, Masataka Oita and Teiji Nishio : Experimental validation of 4D dynamic dose calculation method to deal with simulated amplitude changes over time in scanned proton therapy, The 129st Scientific Meeting of the Japan Society of Medical Physics, Apr. 2025.
7.
Yushi Wakisaka, Yuki Tominaga and Teiji Nishio : Dynamic Collimation with Multi-Leaf Collimator in Scanned Proton Therapy, The 129st Scientific Meeting of the Japan Society of Medical Physics, Apr. 2025.
8.
Masato Horita, Ryo Tanokura, Takahiro Kato and Yuki Tominaga : Validation of Beam Data Registration for a New Proton Therapy System, The 129st Scientific Meeting of the Japan Society of Medical Physics, Apr. 2025.
9.
Ryo Tanokura, Masato Horita, Yuki Tominaga and Takahiro Kato : Introduction of the proton therapy system at Central Japan International Medical Center and report on commissioning up to beam modeling, The 129st Scientific Meeting of the Japan Society of Medical Physics, Apr. 2025.
冨永 裕樹, Takahiro Kato, Tomomi Uenaka, Yudai Tokuhiro, Teiji Nishio : Comparisons of dose distributions, irradiation time, and optimization time for various beam parameters in arc proton pencil beam scanning, The 127st Scientific Meeting of the Japan Society of Medical Physics, 2024年4月.
15.
Kyotaro Tsuzuki, 冨永 裕樹, Masashi Tomida, Yasuhiro Ito, Masaya Ichihara, Mako Nagata, Takeshi Yanagi, Yuto Imai, Yuta Shibamoto : Spot Position Verification for Patient-Specific QA, The 127st Scientific Meeting of the Japan Society of Medical Physics, 2024年4月.
16.
Yudai Tokuhiro, 冨永 裕樹, Tomomi Uenaka, Teiji Nishio : Availability of beam log data based dose distribution in proton beam scanning irradiation for patient QA, The 127st Scientific Meeting of the Japan Society of Medical Physics, 2024年4月.
17.
Shiryu Otsuka, Keisuke Yasui, Miuna Hayashi, Toshiyuki Toshito, Chihiro Omachi, Hidetoshi Shimizu, Masaya Ichihara, Hiromi Baba, Riki Oshika, 冨永 裕樹, Naoki Hayashi : Verification of the response of radiophotoluminescence dosimeters to proton beams and independent dosimetry audit for scanning beam, The 80th Annual Meeting of the Japanese Society of Radiological Technology, 2024年4月.
Yuki Tominaga, Masataka Oita, Junya Miyata, Yusuke Sakurai and Takashi Akagi : Efficient automated patient specific quality assurance using log files and a commercial treatment planning system in proton pencil beam scanning, 第123回日本医学物理学会学術大会, Apr. 2022.
Yuki Tominaga, Masataka Oita, Junya Miyata, Yusuke Sakurai, Shuichi Harada and Takashi Akagi : Improvements of lateral penumbra widths for various optimized parameters in proton pencil beam scanning with and without a multi-leaf collimator, 第121回日本医学物理学会学術大会, Apr. 2021.
29.
Takayasu Haruna, Masataka Oita, Yuki Tominaga, Mitsutoshi Tada, Masashi Yamanaka, Tetsunori Matsuda and Masahiro Kuroda : Ion recombination and polarity correction factors for different types of ionization, 第121回日本医学物理学会学術大会, Apr. 2021.
30.
Yuki Tominaga, Masataka Oita, Junya Miyata, Yusuke Sakurai, Masashi Yamanaka, Mitsutoshi Tada, Tetsunori Matsuda, Shuichi Harada and Takashi Akagi : Clinical beam commissioning results of proton pencil beam scanning system using multi leaf collimator., 第33回日本放射線腫瘍学会学術大会, Oct. 2020.
31.
Yuki Tominaga, Masataka Oita, Junya Miyata, Yusuke Sakurai, Masashi Yamanaka, Mitsutoshi Tada, Tetsunori Matsuda, Shuichi Harada and Takashi Akagi : Improvements dose calculations accuracy in the proton pencil beam scanning treatment planning system. equipped with a commercial Monte Carlo algorithm, 第119回日本医学物理学会学術大会, May 2020.
32.
Yuki Tominaga, Masataka Oita, Takahiro Waki, Hiroki Ihara, Dongcun Jin, Yasue Niwa, Masahiro Kuroda, Mamoru Fujishima and Tetsunori Matsuda : Dose volume comparison of raster scanning proton therapy and VMAT for high-risk prostate cancer, 第32回日本放射線腫瘍学会学術大会, Nov. 2019.
Yuki Tominaga, Masataka Oita, Takahiro Waki, Ryota Hirai, Masashi Yamanaka, Mitsutoshi Tada, Takayasu Haruna, Mizuki Tamura, Takahiro Yamamoto, Kazushi Ida, Katsuyuki Tsunazawa, Masahiro Kuroda, Dongcun Jin, Yasue Niwa and Tetsunori Matsuda : Dose volume comparison of spot scanning proton therapy and passive method for prostate cancer, 第31回日本放射線腫瘍学会学術大会, Oct. 2018.
37.
Yukako Kishigami, Takashi Akagi, Katsuyuki Tsunazawa, Yuki Tominaga, Mitsutoshi Tada, Masashi Yamanaka and Masahiko Koizumi : Effect of range-shifter on dose distributions in proton spot-scanning fields, 第116回日本医学物理学会学術大会, Sep. 2018.
38.
Takashi Akagi and Yuki Tominaga : Comparison of conversion tables for CT-number to water-equivalent thickness between RayStation and the poly-binary calibration in particle therapy, 第116回日本医学物理学会, Sep. 2018.
39.
Mitsutoshi Tada, Yuki Tominaga, Katsuyuki Tsunazawa, Takahiro Yamamoto, Yoshiyuki Yamada, Shuichi Harada, Takashi Akagi, Yusuke Sakurai and Tetsunori Matsuda : An initial report of a new proton therapy machine commissioning in uniform-scan: the principle and verification, 第112回日本医学物理学会学術大会, Sep. 2016.
40.
Yuki Tominaga, Mitsutoshi Tada, Katsuyuki Tsunazawa, Takahiro Yamamoto, Yoshiyuki Yamada, Shuichi Harada, Takashi Akagi, Yusuke Sakurai and Tetsunori Matsuda : Commissioning status of Tsuyama Chuo Hospital proton beam center, 第112回日本医学物理学会学術大会, Sep. 2016.