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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., Competing Interests: Declaration of competing interest Yuji Nakaguchi is an employee of TOYO MEDIC Co., Ltd., (Copyright © 2024 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.)

This study devised a method to efficiently launch the RapidPlan model for volumetric-modulated arc therapy for prostate cancer in small- and medium-sized facilities using high-quality treatment plans with the PlanIQ software as a reference. Treatment plans were generated for 30 patients with prostate cancer to construct the RapidPlan model using PlanIQ as a reference. In the context of PlanIQ-referenced treatment planning, treatment plans were developed, such that the feasibility dose-volume histogram of each organ-at-risk fell within F ≤ 0.1. For validation of the RapidPlan model, treatment plans were formulated for 20 patients using both RapidPlan and PlanIQ, and the differences were evaluated. The results of RapidPlan model validity assessment revealed that the RapidPlan-produced treatment plans exhibited higher quality in 11 of 20 patients. No significant differences were found between the treatment plans. In conclusion, high-quality treatment plans formulated using PlanIQ as reference facilitated efficient implementation of RapidPlan modeling., (© 2023. The Author(s), under exclusive licence to Japanese Society of Radiological Technology and Japan Society of Medical Physics.)

This review provides an overview of the application of artificial intelligence (AI) in radiation therapy (RT) from a radiation oncologist's perspective. Over the years, advances in diagnostic imaging have significantly improved the efficiency and effectiveness of radiotherapy. The introduction of AI has further optimized the segmentation of tumors and organs at risk, thereby saving considerable time for radiation oncologists. AI has also been utilized in treatment planning and optimization, reducing the planning time from several days to minutes or even seconds. Knowledge-based treatment planning and deep learning techniques have been employed to produce treatment plans comparable to those generated by humans. Additionally, AI has potential applications in quality control and assurance of treatment plans, optimization of image-guided RT and monitoring of mobile tumors during treatment. Prognostic evaluation and prediction using AI have been increasingly explored, with radiomics being a prominent area of research. The future of AI in radiation oncology offers the potential to establish treatment standardization by minimizing inter-observer differences in segmentation and improving dose adequacy evaluation. RT standardization through AI may have global implications, providing world-standard treatment even in resource-limited settings. However, there are challenges in accumulating big data, including patient background information and correlating treatment plans with disease outcomes. Although challenges remain, ongoing research and the integration of AI technology hold promise for further advancements in radiation oncology., (© The Author(s) 2023. Published by Oxford University Press on behalf of The Japanese Radiation Research Society and Japanese Society for Radiation Oncology.)

Background: Currently, the standard curative treatment for ventricular tachycardia (VT) and ventricular fibrillation (VF) is radiofrequency catheter ablation. However, when the VT circuit is deep in the myocardium, the catheter may not be delivered, and a new, minimally invasive treatment using different energies is desired., Methods: This is a protocol paper for a feasibility study designed to provide stereotactic radiotherapy for refractory VT not cured by catheter ablation after at least one catheter ablation. The primary end point is to evaluate the short-term safety of this treatment and the secondary endpoint is to evaluate its efficacy as assessed by the reduction in VT episode. Cyberknife M6 radiosurgery system will be used for treatment, and the prescribed dose to the target will be 25Gy in one fraction. The study will be conducted on three patients., Conclusion: Since catheter ablation is the only treatment option for VT that is covered by insurance in Japan, there is currently no other treatment for VT/VF that cannot be cured by catheter ablation. We hope that this feasibility study will provide hope for patients who are currently under the stress of ICD activation., Trial Registration: The study has been registered in the Japan Registry of Clinical Trials (jRCTs042230030)., Competing Interests: No competing interests were disclosed., (Copyright: © 2023 Kawamura M et al.)

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., Competing Interests: Conflict of interest: Yuji Nakaguchi is an employee of TOYO MEDIC CO., LTD., (© 2023 Greater Poland Cancer Centre.)

Prostatic urethra identification is crucial in prostate stereotactic body radiotherapy (SBRT) to reduce the risk of urinary toxicity. Although computed tomography (CT) with a catheter is commonly employed, it is invasive, and catheter placement may displace the urethral position, resulting in possible planning inaccuracies. However, magnetic resonance imaging (MRI) can overcome these weaknesses. Accurate urethral identification and minimal daily variation could ensure a highly accurate SBRT. In this study, we investigated the usefulness of a three-dimensional (3D) T2-weighted (T2W) sequence for urethral identification, and the interfractional motion of the prostatic urethra on CT with a catheter and MRI without a catheter for implementing noninvasive SBRT. Thirty-two patients were divided into three groups. The first group underwent MRI without a catheter to evaluate urethral identification by two-dimensional (2D)- and 3D-T2W sequences using mean slice-wise Hausdorff distance (MSHD) and Dice similarity coefficient (DSC) of the contouring by two operators and using visual assessment. The second group provided 3-day MRI data without a catheter using 3D-T2W, and the third provided 3-day CT data with a catheter to evaluate the interfractional motion using MSHD, DSC, and displacement distance (Dd). The MSHD and DSC for the interoperator variability in urethral identification and visual assessment were superior in 3D-T2W than in 2D-T2W. Regarding interfractional motion, the Dd value for prostatic urethra was smaller in MRI than in CT. These findings indicate that the 3D-T2W yielded adequate prostatic urethral identification, and catheter-free MRI resulted in less interfractional motion, suggesting that 3D-T2W MRI without a catheter is a feasible noninvasive approach to performing prostate SBRT., Competing Interests: The authors declare that they have no conflicts of interest.

This technical report provides useful information on the current status and issues of quality control in 125 I seed source strength measurement for Permanent Prostate Brachytherapy in Japan.With the spread of 125 I seed brachytherapy, the traceability of source strength measurements with the single-seed assay was established in Japan. This allows medical facilities to measure reference air kerma rate of 125 I seeds with their own well-type of ionization chamber. However, it is difficult to maintain the traceability chain because the 125 I reference air kerma rate standards have been hardly utilized by medical facilities so far. Meanwhile, some serious incidents of contamination of the different source strengths and dead seeds were reported in Japan.To address the specific issues in Japan, JASTRO Brachytherapy Subcommittee established a working group (WG) in 2021. The goal of this WG is to investigate the management methods of source strength measurement used in medical facilities, and to discuss the ideal and practicable methods of source management such as verifying the number of seeds and source strength. Initially, a questionnaire survey was conducted to facilities offering 125 I seed brachytherapy in Japan. Sixty-seven out of 95 facilities responded (response rate 70.5%). This survey revealed that 41% of facilities did not perform either confirmation of the number of seeds or measurement of source strength. There are several reasons why the source strength was not measured in those facilities. For example, 125 I seeds are provided under the sterilized conditions; quality assurance by source suppliers is reliable; and there is not sufficient staff.The single-seed assay is regarded as an internationally standardized and the most reliable measurement method. Therefore, it is an essential measurement technique to ensure traceability of source strength measurements. However, our survey found that most Japanese facilities do not perform single-seed assays. Meanwhile, some facilities have performed batch assay as an alternative method, in which all of the multiple sources in a batch are measured while loaded into sterilized cartridges. Although the measurement by the batch assay is less accurate than the one by the single-seeded assay, the batch assay does not require re-sterilization of the source and can be performed quickly. It might be useful to detect unexpected errors such as differences in the number of sources and abnormalities in source strength.In this report, we will introduce several methods of source strength measurement that have been implemented in medical facilities. The quality assurance of 125 I seed sources in prostate interstitial brachytherapy should be provided not only by the source suppliers but also by the medical facilities that use sources to treat patients. We hope that medical facilities will refer to this technical report and use it as an aid to quality assurance in their own facilities.

Background/aim: The more complex the treatment plan, the higher the possibility of errors in dose verification. Recently, a treatment planning quality assurance (QA) software (PlanIQ) with a function to objectively evaluate the quality of volumetric-modulated arc therapy (VMAT) treatment plans by scoring and calculating the ideal dose-volume histogram has been marketed. This study aimed to assess the association between the scores of ideal treatment plans identified using PlanIQ and the results of dose verification and to investigate whether the results of dose verification can be predicted based on the complexity of treatment plans., Materials and Methods: Dose verification was performed using an ionization chamber dosimeter, a radiochromic film, and a three-dimensional dose verification system, Delta4 PT. Correlations between the ideal treatment plan scores obtained by PlanIQ and the results of the absolute dose verification and dose distribution verification were obtained, and it was examined whether dose verifications could be predicted from the complexity of the treatment plans., Results: Even when the score from the ideal treatment plan was high, the results of absolute dose verification and dose distribution verification were sometimes poor. However, even when the score from the ideal treatment plan was low, the absolute volume verification and dose distribution verification sometimes yielded good results., Conclusions: Treatment plan complexity can be determined in advance from the ideal treatment plan score calculated by PlanIQ. However, it is difficult to predict the results of dose verification using an ideal treatment plan., Competing Interests: Conflict of interest Yuji Nakaguchi is an employee of TOYO MEDIC CO., LTD., (© 2022 Greater Poland Cancer Centre.)

Purpose: Given its high spatial resolution and vasculature selectivity, the cone-beam computed tomography (CT) angiography (CBCTA) image acquired by selective 3D rotational angiography (3DRA) is the most suitable 3D image for the target definition of stereotactic radiosurgery (SRS) for intracranial arteriovenous malformations (AVMs) and dural arteriovenous fistulas (DAVFs). Furthermore, the relatively low temporal resolution of 3DRA-based CBCTA can be complemented by the stereotactic co-registration of orthogonally paired 2D dynamic digital subtraction angiography (2D-DSA). The integration of 2D-DSA, which is usually limited to one or a few frames for each projection, into CBCTA and/or planning CT can be achieved only by catheter-directed angiography on the day of SRS via a dedicated image localizer under rigid frame fixation to the skull, which imposes substantial burdens on patients. This study aimed to demonstrate a novel, convenient, and significantly less invasive method for the frameless co-registration of biplane 2D-DSA whole frames and CBCTA on commercially available dedicated software, namely, Brainlab ® Elements (Brainlab AG, Munich, Germany), and present its prerequisite for successful image fusion. Technical Report: Elements have afforded the following functionality: A 3D vasculature image is automatically extracted as a floating image from any 3D image series containing vascular details and then subsequently co-registered manually and automatically to a selected frame pair of 2D-DSA with a six-degree-of-freedom rigid registration. As a preclinical feasibility study, two anonymous image datasets from patients harboring cerebral AVM and transverse-sigmoid (TS) DAVF were used to verify the accuracy and practicality of Elements for the frameless co-registration of 2D/3D vascular images, particularly on the assumption of clinical workflow for the target delineation of SRS planning. The use of ordinary unsubtracted CBCTA resulted in the insufficient extraction of abutting vessels or vessels that are in close proximity to bony structures, particularly in the case of TS-DAVF, where the fistulous pouch and the affected venous sinuses were adjacent to the cranial bone. By contrast, the amount and selectivity of vasculatures and the accuracy of subsequent image fusion were significantly improved from the subtracted CBCTA. The integration of CBCTA into dynamic 2D-DSA allowed the simultaneous review of both image information by sharing any concerning point and 2D or 3D structures under a common 3D coordinate., Conclusions: Elements enable the clinically useful frameless co-registration of biplane 2D-DSA whole frames into CBCTA, for which the routine acquisition of both subtracted and unsubtracted CBCTA axial images for ordinary diagnostic purposes is an indispensable prerequisite for successful image fusion and further widespread application. This frameless integration of the 2D/3D angiogram would dramatically enhance both the frame-based and frameless SRS workflow and circumstances by allowing users to forward SRS planning well in advance before SRS, along with the omission of invasive angiography on the day of SRS, and would broaden the implementation of frameless SRS. Furthermore, the comprehensive alternating interactive review of the 2D/3D integrated angiogram leads to a more in-depth quasi-4D understanding of the affected angioarchitectures compared with the separate viewing of each image., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2022, Ohtakara et al.)

We aim to evaluate the basic characteristics of SRS MapCHECK (SRSMC) for CyberKnife (CK) and establish a dose verification system using SRSMC for the tumor-tracking irradiation for CK. The field size and angular dependence of SRSMC were evaluated for basic characterization. The output factors (OPFs) and absolute doses measured by SRSMC were compared with those measured using microDiamond and microchamber detectors and those calculated by the treatment planning system (TPS). The angular dependence was evaluated by comparing the SRSMC with a microchamber. The tumor-tracking dose verification system consists of SRSMC and a moving platform. The doses measured using SRSMC were compared with the doses measured using a microchamber and radiochromic film. The OPFs and absolute doses of SRSMC were within ±3.0% error for almost all field sizes, and the angular dependence was within ±2.0% for all incidence angles. The absolute dose errors between SRSMC and TPS tended to increase when the field size was smaller than 10 mm. The absolute doses of the tumor-tracking irradiation measured using SRSMC and those measured using a microchamber agreed within 1.0%, and the gamma pass rates of SRSMC in comparison with those of the radiochromic film were greater than 95%. The basic characteristics of SRSMC for CK presented acceptable results for clinical use. The results of the tumor-tracking dose verification system realized using SRSMC were equivalent to those of conventional methods, and this system is expected to contribute toward improving the efficiency of quality control in many facilities., (© 2022 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, LLC on behalf of The American Association of Physicists in Medicine.)

Purpose: Several factors, including the surrounding brain volume receiving specific doses, have hitherto been reported to correlate with brain radionecrosis (BR) after single or fractionated stereotactic radiosurgery (sSRS or fSRS) for brain metastases (BMs); however, those, especially for fSRS, have not yet been fully elucidated. Furthermore, the clinical outcome data of patients with BM treated with SRS using Vero4DRT are extremely limited. Therefore, this study aimed to demonstrate the incidence of BR requiring intervention (BRRI) and its highly correlated factors., Materials and Methods: Patients with BMs treated with sSRS or fSRS using Vero4DRT at Toyohashi Municipal Hospital between July 2017 and June 2021 were retrospectively reviewed, of whom patients were available for at least 20 weeks of magnetic resonance imaging follow-up from SRS were included, and analyzed. The prescribed dose fractionation schemes to the planning target volume (PTV) boundary included 24 Gy (sSRS), 35 Gy (5 fractions [fr]), 42 Gy (10 fr), and 30 Gy (3 fr), according to the tumor volume and location. The volume of the surrounding normal brain receiving 84 Gy (V84 Gy, biologically effective dose [BED 2 ] based on a linear-quadratic model with an alpha/beta ratio of 2, single-dose equivalent [SDE] to 12 Gy), V112 Gy (BED 2 , SDE to 14 Gy) for all lesions, and all irradiated volume, including gross tumor volume (GTV) receiving 81.6 Gy (81.6 Gy vol., BED 2 ) for fSRS were calculated, for which cerebrospinal fluid and bone volumes were cautiously excluded. The diagnosis of tumor progression or BR dominance was based on serial T1/T2 matching., Results: Sixty patients with 120 lesions (65 treated with sSRS and 55 treated with fSRS) were included in the final analysis, with a median follow-up period of 65 weeks. The local control rate at one year was 87.5%. The cumulative incidence of BRRI within two years was 11.5%. The risk of symptomatic BR was significantly higher for V84 Gy >10 cc ( p <0.001) and V112 Gy >5 cc ( p = 0.021). In the fSRS group, the cumulative incidence of Grade 3 BR and those requiring resection was significantly higher for 81.6 Gy vol. >14 cc ( p = 0.003 and p = 0.004, respectively). The coexistence of viable tumor tissue and BR could not be ruled out for enlarging lesions after the nadir response, especially for fSRS, due to a lower BED 10 to GTV margin (<80 Gy, BED 10 )., Conclusions: Stereotactic irradiation with Vero4DRT provided efficacy and safety comparable to previous linear accelerator series, and most of the dose-volume thresholds for BRRI presented in this study were notably lower than those reported in previous studies. This study suggests that the indication of single and up to 5 frSRS should be limited to far smaller tumors than previously acknowledged to ensure long-term safety and efficacy., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2022, Yamada et al.)

Purpose: Gold fiducial markers are used to guide liver stereotactic body radiation therapy (SBRT) and are hard to detect by magnetic resonance imaging (MRI). In this study, the parameters of the three-dimensional T1-weighted turbo gradient-echo (3D T1W-GRE) sequence were optimized for gold marker detection without degrading tumor delineation., Methods: Custom-made phantoms mimicking tumor and normal liver parenchyma were prepared and embedded with a gold marker. The 3D T1W-GRE was scanned by varying echo time (TE), bandwidth (BW), flip angle (FA), and base matrix size. The signal-to-noise ratio (SNR), contrast ratio (CR), and relative standard deviation (RSD) of the signal intensity in the area including the gold marker were evaluated, and the parameters were optimized accordingly. The modified 3D T1W-GRE (called HYBRID) was compared with the conventional T1W-GRE- and T2*-sequences in both phantom and clinical studies. In the clinical study of six patients with primary liver tumors, two observers visually assessed marker detection, tumor delineation, and overall image quality on a four-point scale., Results: In the phantom study, HYBRID showed significantly higher SNR and RSD than those of conventional T1W-GRE (P < 0.001). In the clinical study, HYBRID yielded significantly higher scores than conventional T1W-GRE did in terms of marker detection (P < 0.001). The scores of both sequences were not statistically different in terms of tumor delineation and overall image quality (P = 0.56 and P = 0.32)., Conclusions: The proposed HYBRID sequence improved gold fiducial marker detection without degrading tumor delineation in MRI for SBRT of primary liver tumor., (Copyright © 2022 Associazione Italiana di Fisica Medica e Sanitaria. Published by Elsevier Ltd. All rights reserved.)

This study aimed to investigate the effect of two different image density adjustment parameters on the results of image matching at six degrees of freedom using radiographic images generated by the ExacTrac X-ray system in brain stereotactic radiosurgery (SRS). This study comprised 32 patients who underwent brain SRS at our hospital from January 2020 to December 2020. In this study, (1) the default parameter (an image density parameter between "tissue" and "bone") was an image density parameter for digitally reconstructed radiograph (DRR) generation used at many facilities, and (2) the bone parameter was the steepest contrast parameter used at our hospital. Of the 32 patients, 24 (75%) had a couch angle of 0.5 mm or more in the translational direction or 0.5° or more in the rotational direction, and 10 (31%) had a couch angle of 1.0 mm or more in the translational direction or 1.0° or more in the rotational direction. Among the 131 cases of all couch angles, 46 (35%) cases had a translational direction of 0.5 mm or more or a rotational direction of 0.5° or more, and 15 (11%) had a translational direction of 1.0 mm or more or a rotational direction of 1.0° or more. The results of this study indicate the usefulness of using appropriate DRR parameters for each case, rather than using the default settings. The use of appropriate DRR parameters can lead to accurate position matching results, leading to fewer image-guided radiation therapy shots and a lower imaging dose., (© 2021 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, LLC on behalf of The American Association of Physicists in Medicine.)

We propose two methods to evaluate system-related distortion in magnetic resonance imaging (MRI) in radiation therapy treatment planning (RTP) and demonstrate the importance of three-dimensional (3D) distortion correction (DC) by quantitatively measuring the distortion magnitude. First, a small pin phantom was scanned at multiple positions using an external laser guide for accurate phantom placement and combined into one image encompassing a large area. Direct plane images were used for evaluating in-plane distortion and multiplanar reconstruction images for through-plane distortion with no DC, two-dimensional (2D) DC, and 3D DC. Second, a large grid sheet was scanned as the direct plane of the phantom placement. The distortion magnitude was determined by measuring the displacement between the MRI and reference coordinates. The measured distortions were compared between in- and through-plane when applying DC and between the two methods. The small pin phantom method can be used to evaluate a wide range of distortions, whereas data from the entire plane can be obtained with a single scan using the grid sheet without a laser guide. The mean distortion magnitudes differed between the methods. Furthermore, the 3D DC reduced in- and through-plane distortions. In conclusion, the small pin phantom method can be used to evaluate a wide range of distortions by creating a combined image, whereas the grid sheet method is simpler, accurate, repeatable, and does not require a special-order phantom or laser guide. As 3D DC reduces both in- and through-plane distortions, it can be used to improve RTP quality., Competing Interests: The authors declare that they have no conflict of interest.

Purpose: Accurate calculation of the proton beam range inside a patient is an important topic in proton therapy. In recent times, a computed tomography (CT) image reconstruction algorithm was developed for treatment planning to reduce the impact of the variation of the CT number with changes in imaging conditions. In this study, we investigated the usefulness of this new reconstruction algorithm (DirectDensity™: DD) in proton therapy based on its comparison with filtered back projection (FBP)., Methods: We evaluated the effects of variations in the X-ray tube potential and target size on the FBP- and DD-image values and investigated the usefulness of the DD algorithm based on the range variations and dosimetric quantity variations., Results: For X-ray tube potential variations, the range variation in the case of FBP was up to 12.5 mm (20.8%), whereas that of DD was up to 3.3 mm (5.6%). Meanwhile, for target size variations, the range variation in the case of FBP was up to 2.2 mm (2.5%), whereas that of DD was up to 0.9 mm (1.4%). Moreover, the variations observed in the case of DD were smaller than those of FBP for all dosimetric quantities., Conclusion: The dose distributions obtained using DD were more robust against variations in the CT imaging conditions (X-ray tube potential and target size) than those obtained using FBP, and the range variations were often less than the dose calculation grid (2 mm). Therefore, the DD algorithm is effective in a robust workflow and reduces uncertainty in range calculations., (Copyright © 2021 Associazione Italiana di Fisica Medica e Sanitaria. Published by Elsevier Ltd. All rights reserved.)

Purpose: We developed an x-ray-opaque-marker (XOM) system with inserted fiducial markers for patient-specific quality assurance (QA) in CyberKnife (Accuray) and a general-purpose linear accelerator (linac). The XOM system can be easily inserted or removed from the existing patient-specific QA phantom. Our study aimed to assess the utility of the XOM system by evaluating the recognition accuracy of the phantom position error and estimating the dose perturbation around a marker., Methods: The recognition accuracy of the phantom position error was evaluated by comparing the known error values of the phantom position with the values measured by matching the images with target locating system (TLS; Accuray) and on-board imager (OBI; Varian). The dose perturbation was evaluated for 6 and 10 MV single-photon beams through experimental measurements and Monte Carlo simulations., Results: The root mean squares (RMSs) of the residual position errors for the recognition accuracy evaluation in translations were 0.07 mm with TLS and 0.30 mm with OBI, and those in rotations were 0.13° with TLS and 0.15° with OBI. The dose perturbation was observed within 1.5 mm for 6 MV and 2.0 mm for 10 MV from the marker., Conclusions: Sufficient recognition accuracy of the phantom position error was achieved using our system. It is unnecessary to consider the dose perturbation in actual patient-specific QA. We concluded that the XOM system can be utilized to ensure quantitative and accurate phantom positioning in patient-specific QA with CyberKnife and a general-purpose linac., (Copyright © 2021 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

Purpose: Equipment refurbishment was performed to remove the beam-hardening filter (BHF) from the CyberKnife system (CK). This study aimed to confirm the change in the beam characteristics between the conventional CK (present-BHF CK) and CK after the BHF was removed (absent-BHF CK) and evaluate the impact of BHF removal on the beam quality correction factors k Q ., Methods: The experimental measurements of the beam characteristics of the present- and absent-BHF CKs were compared. The CKs were modeled using Monte Carlo simulations (MCs). The energy fluence spectra were calculated using MCs. Finally, k Q were estimated by combining the MC results and analytic calculations based on the TRS-398 and TRS-483 approaches., Results: All gamma values for percent depth doses and beam profiles between each CK were less than 0.5 following the 3%/1 mm criteria. The percentage differences for tissue-phantom ratios at depths of 20 and 10 cm and percentage depth doses at 10 cm between each CK were -1.20% and -0.97%, respectively. The MC results demonstrated that the photon energy fluence spectrum of the absent-BHF CK was softer than that of the present-BHF CK. The k Q values for the absent-BHF CK were in agreement within 0.02% with those for the present-BHF CK., Conclusions: The photon energy fluence spectrum was softened by the removal of BHF. However, no remarkable impact was observed for the measured beam characteristics and k Q . Therefore, the previous findings of the k Q values for the present-BHF CK can be directly used for the absent-BHF CK., (Copyright © 2021 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

Purpose: The purpose of this study was to assess the quality of treatment planning using the PlanIQ TM software and to investigate whether it is possible to improve the quality of treatment planning using the "Feasibility dose-volume histogram (DVH) TM " implemented in the PlanIQ TM software., Methods: Using the PlanIQ TM software, we retrospectively analyzed the learning curve regarding the quality of the treatment plans for 148 patients of prostate intensity-modulated radiation therapy and volumetric-modulated radiation therapy performed at our institution over the past eight years. We also sought to examine the possibility of improving treatment planning quality by re-planning in 47 patients where the quality of the target dose and the dose limits for organs at risk (OARs) were inadequate. The re-planning treatment plans referred to the Feasibility DVH TM implemented in the PlanIQ TM software and modified the treatment planning system based on the target dose and OAR constraints., Results: Analysis of the learning curve of the treatment plans quality using PlanIQ TM software retrospectively showed a trend of improvement in the treatment plan quality from year to year. The improvement in the treatment plans quality was more influenced by dose reduction in the OARs than by target coverage. In all cases where re-planning was performed, the improvement in the treatment plan's quality resulted in a better treatment plan than the one adopted for delivery to patients in the clinical plan., Conclusions: The PlanIQ TM provided insights into the quality of the treatment plans at our institution and identified problems and areas for improvement in the treatment plans, allowing for the development of appropriate treatment plans for specific patients., (© 2021 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.)

Introduction: Software that evaluates the quality of treatment plans (PlanIQ TM ) has become commercially available in recent years. It includes a feasibility assessment tool that provides the ideal dose volume histogram (DVH) for each organ at risk, based on the ideal dose falloff from the prescribed dose at the target boundary. It is important to investigate whether the PlanIQ TM assessment tool (Feasibility DVH TM ) can assist treatment planners who have limited to no experience in treatment planning. Therefore, the present study aimed to evaluate this tool's usefulness for improving the quality of treatment plans., Materials & Methods: This study included 5 patients with prostate cancer. The treatment planners were 2 graduate students, 2 undergraduate students, and one clinical planner. All students were radiological technology and medical physics students with no clinical experience. Two different volumetric-modulated arc therapy (VMAT) plans were developed before and after Feasibility DVH TM . The quality of each treatment plan was evaluated based on a scoring system implemented in PlanIQ TM ., Results: Of 5 patients included, 4 received improved treatment plans when Feasibility DVH TM was used. Moreover, 4 of 5 treatment planners showed improvement in treatment planning using Feasibility DVH TM ., Conclusions: The findings suggest that using the Feasibility DVH TM tool may improve treatment plans for different planners and patients. However, planners at any level of experience should be trained to check the dose distribution in addition to checking the DVH, which depends on the adequacy of the contours., Competing Interests: Conflicts of Interest Yuji Nakaguchi is an employee of TOYO MEDIC CO., LTD., (Copyright © 2021 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.)

Containing 80% tungsten by weight, tungsten functional paper (TFP) is a radiation-shielding material that is lightweight, flexible, disposable, and easy to cut. Through experimental measurements and Monte Carlo simulations, we investigated the feasibility of using TFP as a bolus in electron beam radiotherapy. Commercial boluses of thickness 5 and 10 mm and from one to nine layers of TFPs (0.3-2.7 mm) were positioned on the surface of water-equivalent phantoms. The percentage depth dose curves and transverse dose profiles were measured using a 9-MeV electron beam from a clinical linear accelerator. Normalized to the value at the depth of maximum dose without bolus, the relative doses at the phantom surface for no bolus, 5-mm bolus, 10-mm bolus, 1 TFP, 3 TFPs, 6 TFPs, and 9 TFPs were 78%, 88%, 92%, 84%, 92%, 102%, and 112%, respectively; the therapeutic depths corresponding to a 90% dose level were 29.1 mm, 22.7 mm, 17.7 mm, 26.6 mm, 23.2 mm, 19.3 mm, and 15.8 mm, respectively. The TFP contributed to increased skin dose and provided dose uniformity within the target volume. However, it also resulted in increased lateral constriction and penumbra width. The results of Monte Carlo simulation produced similar trends as the experimental measurements. Our findings suggest that using TFP as a novel thin and flexible skin bolus for electron beam radiotherapy is feasible.

Although phase III trials have been published comparing whole breast irradiation (WBI) with accelerated partial breast irradiation (APBI) using intraoperative radiotherapy (IORT), long-term follow-up results are lacking. We report the 10-year follow-up results of a prospective phase I/II clinical trial of IORT. The inclusion criteria were as follows: (i) tumor size <2.5 cm, (ii) desire for breast-conserving surgery, (iii) age >50 years, (iv) negative margins after resection and (v) sentinel lymph node-negative disease. A single dose of IORT (19-21 Gy) was delivered to the tumor bed in the operation room just after wide local excision of the primary breast cancer using a 6-12 MeV electron beam. Local recurrence was defined as recurrence or new disease within the treated breast and was evaluated annually using mammography and ultrasonography. A total of 32 patients were eligible for evaluation. The median patient age was 65 years and the median follow-up time was 10 years. Two patients experienced local recurrence just under the nipple, out of the irradiated field, after 8 years of follow-up. Three patients had contralateral breast cancer and one patient experienced bone metastasis after 10 years of follow-up. No patient experienced in-field recurrence nor breast cancer death. Eight patients had hypertrophic scarring at the last follow-up. There were no lung or heart adverse effects. This is the first report of 10-year follow-up results of IORT as APBI. The findings suggest that breast cancer with extended intraductal components should be treated with great caution., (© The Author(s) 2020. Published by Oxford University Press on behalf of The Japanese Radiation Research Society and Japanese Society for Radiation Oncology.)

Purpose: In the previous treatment planning system (TPS) for CyberKnife (CK), multileaf collimator (MLC)-based treatment plans could be created only by using the finite-size pencil beam (FSPB) algorithm. Recently, a new TPS, including the FSPB with lateral scaling option (FSPB+) and Monte Carlo (MC) algorithms, was developed. In this study, we performed basic and clinical end-to-end evaluations for MLC-based CK tumor-tracking radiotherapy using the MC, FSPB+, and FSPB., Methods: Water- and lung-equivalent slab phantoms were combined to obtain the percentage depth dose (PDD) and off-center ratio (OCR). The CK M6 system and Precision TPS were employed, and PDDs and OCRs calculated by the MC, FSPB+, and FSPB were compared with the measured doses obtained for 30.8 × 30.8 mm 2 and 60.0 × 61.6 mm 2 fields. A lung motion phantom was used for clinical evaluation and MLC-based treatment plans were created using the MC. The doses were subsequently recalculated using the FSPB+ and FSPB, while maintaining the irradiation parameters. The calculated doses were compared with the doses measured using a microchamber (for target doses) or a radiochromic film (for dose profiles). The dose volume histogram (DVH) indices were compared for all plans., Results: In homogeneous and inhomogeneous phantom geometries, the PDDs calculated by the MC and FSPB+ agreed with the measurements within ±2.0% for the region between the surface and a depth of 250 mm, whereas the doses calculated by the FSPB in the lung-equivalent phantom region were noticeably higher than the measurements, and the maximum dose differences were 6.1% and 4.4% for the 30.8 × 30.8 mm 2 and 60.0 × 61.6 mm 2 fields, respectively. The maximum distance to agreement values of the MC, FSPB+, and FSPB at the penumbra regions of OCRs were 1.0, 0.6, and 1.1 mm, respectively, but the best agreement was obtained between the MC-calculated curve and measurements at the boundary of the water- and lung-equivalent slabs, compared with those of the FSPB+ and FSPB. For clinical evaluations using the lung motion phantom, under the static motion condition, the dose errors measured by the microchamber were -1.0%, -1.9%, and 8.8% for MC, FSPB+, and FSPB, respectively; their gamma pass rates for the 3%/2 mm criterion comparing to film measurement were 98.4%, 87.6%, and 31.4% respectively. Under respiratory motion conditions, there was no noticeable decline in the gamma pass rates. In the DVH indices, for most of the gross tumor volume and planning target volume, significant differences were observed between the MC and FSPB, and between the FSPB+ and FSPB. Furthermore, significant differences were observed for lung D mean , V 15 Gy , and V 20 Gy between the MC, FSPB+, and FSPB., Conclusions: The results indicate that the doses calculated using the MC and FSPB+ differed remarkably in inhomogeneous regions, compared with the FSPB. Because the MC was the most consistent with the measurements, it is recommended for final dose calculations in inhomogeneous regions such as the lung. Furthermore, the sufficient accuracy of dose delivery using MLC-based tumor-tracking radiotherapy by CK was demonstrated for clinical implementation., (© 2020 American Association of Physicists in Medicine.)

Background: The role of local radiotherapy in the treatment of metastatic rhabdomyosarcoma is important. However, with peritoneal dissemination, the application of local therapy is challenging. Although there are few reports addressing the efficacy of the whole abdominopelvic irradiation to peritoneal disseminated rhabdomyosarcoma patients, no precise curse of treatment nor the follow up result is explained in paper nor in the text., Case Presentation: Six years old rhabdomyosarcoma boy with peritoneal dissemination was treated at our facility under COG D9803 protocol (vincristine, dactinomycin, and cyclophosphamide (VAC)). He underwent tumor resection on the 14th week according to the protocol. During surgery, the 2-cm residual tumor was completely resected, but in the pelvis, numerous nodules that were suspected as peritoneal disseminated tumors were observed. We administered 30 Gy/20fr whole abdominopelvic radiotherapy using volumetric modulated arc therapy (VMAT) technique and a 6 Gy sequential boost to pelvis after the surgery and completed the protocol treatment. During the course of treatment, the patient experienced G4 hematological toxicity and received multiple transfusions, particularly after whole abdominopelvic irradiation. He has achieved complete remission and is alive without evidence of recurrence and severe late adverse effect for 3 years. In terms of growth, his height and weight are within the average values for Japanese boys at the same age., Conclusion: By using the VMAT technique, a patient with peritoneal disseminated rhabdomyosarcoma can be treated, and a dose of 30 Gy to the whole abdominopelvis with concurrent chemotherapy may be tolerable.

Background/aim: The aim of the study was to investigate the dosimetric characteristics of electron beams with a tungsten functional paper (TFP) surface collimator., Materials and Methods: The circular field of 6.0 cm diameter was created with the TFP collimator put on the phantom. Depth and lateral dose profiles for 4 and 6 MeV electron beams were obtained. The characteristics of lateral dose profile, treatment diameter as width over 90% of the dose, and penumbra as width of the off-axis positions from 80% to 20% dose levels were evaluated., Results: Compared to the lead collimator, the TFP collimator generated higher surface doses, the treatment diameters were increased from 42.8 to 48.6 mm and from 40.0 to 41.4 mm, and the penumbras were reduced from 15.0 to 9.6 mm and from 16.4 to 13.0 mm for 4 and 6 MeV electron beams, respectively., Conclusion: The TFP surface collimator can provide an excellent dose distribution compared to the conventional lead collimator., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Intraoperative electron radiotherapy (IOERT), which is an accelerated partial breast irradiation method, has been used for early-stage breast cancer treatment. In IOERT, a protective disk is inserted behind the target volume to minimize the dose received by normal tissues. However, to use such a disk, the surgical incision must be larger than the field size because the disk is manufactured from stiff and unyielding materials. In this study, the applicability of newly developed tungsten-based functional paper (TFP) was assessed as an alternative to the existing protective disk. The radiation-shielding performance of the TFP was verified through experimental measurements and Monte Carlo simulations. Percentage depth dose curves and lateral dose profiles with and without TFPs were measured and simulated on a dedicated IOERT accelerator. The number of piled-up TFPs was changed from 1 to 40. In the experimental measurements, the relative doses at the exit plane of the TFPs for 9 MeV were 42.7%, 9.2%, 0.2%, and 0.1% with 10, 20, 30, and 40 TFPs, respectively, whereas those for 12 MeV were 63.6%, 27.1%, 8.6%, and 0.2% with 10, 20, 30, and 40 TFPs, respectively. Slight dose enhancements caused by backscatter radiation from the TFPs were observed at the entrance plane of the TFPs at both beam energies. The results of the Monte Carlo simulation indicated the same tendency as the experimental measurements. Based on the experimental and simulated results, the radiation-shielding performances of 30 TFPs for 9 MeV and 40 TFPs for 12 MeV were confirmed to be acceptable and close to those of the existing protective disk. The findings of this study suggest the feasibility of using TFPs as flexible chest wall protectors in IOERT for breast cancer treatment.

Pretreatment intensity-modulated radiotherapy quality assurance is performed using simple rectangular or cylindrical phantoms; thus, the dosimetric errors caused by complex patient-specific anatomy are absent in the evaluation objects. In this study, we construct a system for generating patient-specific three-dimensional (3D)-printed phantoms for radiotherapy dosimetry. An anthropomorphic head phantom containing the bone and hollow of the paranasal sinus is scanned by computed tomography (CT). Based on surface rendering data, a patient-specific phantom is formed using a fused-deposition-modeling-based 3D printer, with a polylactic acid filament as the printing material. Radiophotoluminescence glass dosimeters can be inserted in the 3D-printed phantom. The phantom shape, CT value, and absorbed doses are compared between the actual and 3D-printed phantoms. The shape difference between the actual and printed phantoms is less than 1 mm except in the bottom surface region. The average CT value of the infill region in the 3D-printed phantom is -6 ± 18 Hounsfield units (HU) and that of the vertical shell region is 126 ± 18 HU. When the same plans were irradiated, the dose differences were generally less than 2%. These results demonstrate the feasibility of the 3D-printed phantom for artificial in vivo dosimetry in radiotherapy quality assurance., (Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

Stereotactic body radiation therapy (SBRT) using recently introduced multileaf collimators (MLC) is preferred over circular collimators in the treatment of localized prostate cancer. The objective of this study was to assess the clinical usefulness of MLCs in prostate SBRT by comparing the effectiveness of treatment plans using fixed collimators, variable collimators, and MLCs and by ensuring delivery quality assurance (DQA) for each. For each patient who underwent conventional radiation therapy for localized prostate cancer, mock SBRT plans were created using a fixed collimator, a variable collimator, and an MLC. The total MUs, treatment times, and dose-volume histograms of the planning target volumes and organs at risk for each treatment plan were compared. For DQA, a phantom with a radiochromic film or an ionization chamber was irradiated in each plan. We performed gamma-index analysis to evaluate the consistency between the measured and calculated doses. The MLC-based plans had an ~27% lower average total MU than the plans involving other collimators. Moreover, the average estimated treatment time for the MLC plan was 31% and 20% shorter than that for the fixed and variable collimator plans respectively. The gamma-index passing rate in the DQA using film measurements was slightly lower for the MLC than for the other collimators. The DQA results acquired using the ionization chamber showed that the discrepancies between the measured and calculated doses were within 3% in all cases. The results reinforce the usefulness of MLCs in robotic radiosurgery for prostrate SBRT treatment planning; most notably, the total MU and treatment time were both reduced compared to the cases using other types of collimators. Moreover, although the DQA results based on film dosimetry yielded a slightly lower gamma-index passing rate for the MLC than for the other collimators, the MLC accuracy was determined to be sufficient for clinical use., (© 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.)

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.

Tungsten functional paper (TFP), which contains 80% tungsten by weight, has radiation-shielding properties. We investigated the use of TFP for the protection of operators during interventional or therapeutic angiography. The air kerma rate of scattered radiation from a simulated patient was measured, with and without TFP, using a water-equivalent phantom and fixed C-arm fluoroscopy. Measurements were taken at the level of the operator's eye, chest, waist, and knee, with a variable number of TFP sheets used for shielding. A Monte Carlo simulation was also utilized to analyze the dose rate delivered with and without the TFP shielding. In cine mode, when the number of TFP sheets was varied through 1, 2, 3, 5, and 10, the respective reduction in the air kerma rate relative to no TFP shielding was as follows: at eye level, 24.9%, 29.9%, 41.6%, 50.4%, and 56.2%; at chest level, 25.3%, 33.1%, 34.9%, 46.1%, and 44.3%; at waist level, 45.1%, 57.0%, 64.4%, 70.7%, and 75.2%; and at knee level, 2.1%, 2.2%, 2.1%, 2.1%, and 2.1%. In fluoroscopy mode, the respective reduction in the air kerma rate relative to no TFP shielding was as follows: at eye level, 24.8%, 30.3%, 34.8%, 51.1%, and 58.5%; at chest level, 25.8%, 33.4%, 35.5%, 45.2%, and 44.4%; at waist level, 44.6%, 56.8%, 64.7%, 71.7%, and 77.2%; and at knee level, 2.2%, 0.0%, 2.2%, 2.8%, and 2.5%. The TFP paper exhibited good radiation-shielding properties against the scattered radiation encountered in clinical settings, and was shown to have potential application in decreasing the radiation exposure to the operator during interventional radiology., (© 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.)

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, u sd , and the dose increases resulting from the PV increases per ±29min 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 3h after irradiation, and a slight increase continued from 3h to 120h. u sd was independent of post-irradiation elapsed time. Sharp decreases in u time were obtained within 1h after irradiation, and slight decreases in u time were observed from 1 to 24h after irradiation. u c 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., (Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

The application of neoadjuvant androgen deprivation (NAD) in prostate cancer leads to a reduction in prostate volume, and the trends in volume reduction differ according to the treatment duration of NAD. A reduction in volume during external beam radiation therapy may lead to the exposure of normal tissues to an unexpected dose. In fact, prostate volume reductions have primarily been reported in European and American institutions. Although the prostate volume of Japanese patients is known to be small, the trends in prostate volume change during radiation therapy remain unclear. In the present study, we aimed to evaluate the changes in prostate volume of Japanese patients during intensity-modulated radiation therapy (IMRT) with NAD. Nineteen Japanese patients with prostate cancer underwent IMRT with NAD. Kilovoltage computed tomography (CT) images were obtained for treatment planning and verification of the treatment position for each treatment fraction. The patients were divided into 3 groups based on the duration of NAD, as follows: NAD < 3 months (short NAD: S-NAD), 3 months ≤ NAD < 6 months (middle NAD: M-NAD), and NAD ≥ 6 months (long NAD: L-NAD). The prostate volume reductions at the 36th treatment fraction, relative to the planning CT, were 7.8%, 2.0%, and 1.7% for the S-NAD, M-NAD, and L-NAD groups, respectively. Prostate volume shrunk greater in the S-NAD group than in the M-NAD and L-NAD groups; this finding was consistent with those of previous studies. The prostate volume changes in Japanese patients were smaller compared to those in European and American patients.

Aim: Late rectal toxicity (LRT) was retrospectively evaluated in men with prostate cancer treated with image-guided intensity modulated radiotherapy (IG-IMRT)., Patients and Methods: Between May 2008 and December 2009, 47 men with prostate adenocarcinoma were treated with IG-IMRT using in-room computed tomography (CT)., Results: The median time to grade 2 LRT was 12 months (range=1-24 months). Two of 3 men who developed grade 2 LRT had received treatment for diabetes, and the other was receiving anticoagulant/antiplatelet therapy (AC therapy). Their rectal wall V70 (the volume of rectal wall receiving 70 Gy) values were 12.6%, 13.0%, and 13.3%. Univariate analysis revealed that V70 of the rectal wall was the only significant risk factor for LRT (p=0.0073)., Conclusion: No man with V70 ≤12.0% experienced grade 2 LRT. Strict rectal wall V70 ≤12% dose constraints should be considered when treating prostate cancer patients who are also receiving diabetic or AC therapy., (Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.)

Metal dental restoration materials cause dose enhancement upstream and dose disturbance downstream of the high-density inhomogeneous regions in which these materials are used. In this study, we evaluated the impact of a dental metallic crown (DMC) on intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) for head and neck cancer. Additionally, the possibility of sparing the oral mucosa from dose enhancement using an individual intraoral mouthpiece was evaluated. An experimental oral phantom was designed to verify the dosimetric impact of a DMC. We evaluated the effect on single beam, parallel opposing beam, arc beam, IMRT, and VMAT treatment plans. To evaluate the utility of a 3-mm-thick intraoral mouthpiece, the doses across the mouthpiece were measured. For single beam irradiation, the measured doses at the entrance and exit planes of the DMC were 51% higher and 21% lower than the calculated dose by the treatment planning system, respectively. The maximum dose enhancements were 22% and 46% for parallel opposing beams and the 90° arc rotation beam, respectively. For IMRT and VMAT, the measured doses adjacent to the DMC were 12.2% ± 6.3% (mean ± 1.96SD) and 12.7% ± 2.5% higher than the calculated doses, respectively. With regard to the performance of the intraoral mouthpiece for the IMRT and VMAT cases, the disagreement between measured and calculated doses at the outermost surface of the mouthpieces were -2.0%, and 2.0%, respectively. Dose enhancements caused by DMC-mediated radiation scattering occurred during IMRT and VMAT. Because it is difficult to accurately estimate the dose perturbations, careful consideration is necessary when planning head and neck cancer treatments in patients with DMCs. To spare the oral mucosa from dose enhancement, the use of an individual intraoral mouthpiece should be considered.

Purpose: 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)., Materials and Methods: 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., Results: 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 D95 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., Conclusion: 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.

Background: To date, there are no reports of intraoperative radiotherapy (IORT) use with long-term follow up as a method of accelerated partial breast irradiation (APBI) in Asian countries. We initiated a prospective phase I/II clinical trial of IORT in Japan in 2007, and herein, we report the 5-year follow-up results., Materials and Methods: The following inclusion criteria were used for enrollment in the trial: (1) tumor size < 2.5 cm, (2) desire for breast-conserving surgery, (3) age >50 years, and (4) negative margins after resection. In February 2009, the eligibility criteria were changed to include only patients with sentinel lymph node-negative disease. In phase I, the radiotherapy dose was escalated from 19 Gy/fr to 21 Gy/fr, incremented by 1 Gy per step, with 3 patients in each step. Doses were escalated after all patients in the preceding cohort had completed treatment and exhibited only grade 1 or 2 toxicities at a given dose level. The recommended phase II dose was set at 21 Gy at 90 % isodose. The primary endpoint was early toxicity. Secondary endpoints were long-term efficacy and late toxicity. In addition, Hypertrophic scarring was evaluated retrospectively as a cosmetic outcome by a radiation oncologist., Results: Between December 2007 and March 2010, 32 women with breast cancer were enrolled in the trial. The median age was 65 years (51-80 years), and the median follow-up time was 6 years. No recurrence or metastasis was observed in any patient. Grade 2 fibrosis was detected in 3 patients as an acute adverse event and in 2 patients as a late adverse event. Ten patients developed a hypertrophic scar 1 year after the IORT; the number of patients decreased to 7 in the 3 years of follow-up., Conclusion: The first group of female Asian patients tolerated the treatment with IORT in this Phase I/II study and remained recurrence-free for more than 5 years after treatment. However, 24 % of the patients developed hypertrophic scarring, an event that is being further examined in our ongoing multi-center Phase II trial of IORT for early breast cancer.

Movement of the target object during cone-beam computed tomography (CBCT) leads to motion blurring artifacts. The accuracy of manual image matching in image-guided radiotherapy depends on the image quality. We aimed to assess the accuracy of target position localization using free-breathing CBCT during stereotactic lung radiotherapy. The Vero4DRT linear accelerator device was used for the examinations. Reference point discrepancies between the MV X-ray beam and the CBCT system were calculated using a phantom device with a centrally mounted steel ball. The precision of manual image matching between the CBCT and the averaged intensity (AI) images restructured from four-dimensional CT (4DCT) was estimated with a respiratory motion phantom, as determined in evaluations by five independent operators. Reference point discrepancies between the MV X-ray beam and the CBCT image-guidance systems, categorized as left-right (LR), anterior-posterior (AP), and superior-inferior (SI), were 0.33 ± 0.09, 0.16 ± 0.07, and 0.05 ± 0.04 mm, respectively. The LR, AP, and SI values for residual errors from manual image matching were -0.03 ± 0.22, 0.07 ± 0.25, and -0.79 ± 0.68 mm, respectively. The accuracy of target position localization using the Vero4DRT system in our center was 1.07 ± 1.23 mm (2 SD). This study experimentally demonstrated the sufficient level of geometric accuracy using the free-breathing CBCT and the image-guidance system mounted on the Vero4DRT. However, the inter-observer variation and systematic localization error of image matching substantially affected the overall geometric accuracy. Therefore, when using the free-breathing CBCT images, careful consideration of image matching is especially important.

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.

The purpose of this study was to experimentally assess the validity of heterogeneity-corrected dose-volume prescription on respiratory-averaged computed tomography (RACT) images in stereotactic body radiotherapy (SBRT) for moving tumors. Four-dimensional computed tomography (CT) data were acquired while a dynamic anthropomorphic thorax phantom with a solitary target moved. Motion pattern was based on cos⁶ (t) with a constant respiration period of 4.0 sec along the longitudinal axis of the CT couch. The extent of motion (A₁) was set in the range of 0.0-12.0 mm at 3.0-mm intervals. Treatment planning with the heterogeneity-corrected dose-volume prescription was designed on RACT images. A new commercially available Monte Carlo algorithm of well-commissioned 6-MV photon beam was used for dose calculation. Dosimetric effects of intrafractional tumor motion were then investigated experimentally under the same conditions as 4D CT simulation using the dynamic anthropomorphic thorax phantom, films, and an ionization chamber. The passing rate of γ index was 98.18%, with the criteria of 3 mm/3%. The dose error between the planned and the measured isocenter dose in moving condition was within ± 0.7%. From the dose area histograms on the film, the mean ± standard deviation of the dose covering 100% of the cross section of the target was 102.32 ± 1.20% (range, 100.59-103.49%). By contrast, the irradiated areas receiving more than 95% dose for A₁ = 12 mm were 1.46 and 1.33 times larger than those for A₁ = 0 mm in the coronal and sagittal planes, respectively. This phantom study demonstrated that the cross section of the target received 100% dose under moving conditions in both the coronal and sagittal planes, suggesting that the heterogeneity-corrected dose-volume prescription on RACT images is acceptable in SBRT for moving tumors., (Copyright © 2012 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.)