Purpose.High-dose-rate interstitial brachytherapy (HDR-IBT) is an essential component of curative treatment for locally advanced cervical cancer, but it is invasive and resource-intensive. Alternative boost techniques are needed when brachytherapy is not feasible. This study compares the dosimetric performance of stereotactic body radiotherapy (SBRT) and Syed-based HDR-IBT to evaluate the potential role of SBRT as a non-invasive boost modality.Materials and Methods.Eighteen patients with stage III-IV cervical cancer previously treated with external beam radiotherapy (EBRT) (45 Gy/25 fx ± nodal boost) followed by Syed HDR-IBT (28 Gy/4 fx) in our clinic were retrospectively analyzed. For each patient, SBRT plans prescribing 28 Gy in 4 fractions were generated on EBRT computed tomography images using fused Syed contours. Dosimetric parameters for targets and organs-at-risk (OARs), such asD98,D90, mean dose, maximum dose,D2cc,D1cc, were compared using the Wilcoxon signed-rank test.Results.For the high-risk clinical target volume (CTV_HR), HDR-IBT provided significantly superior coverage: mean 27 GyD98and 32 GyD90(Syed) vs. mean 25 GyD98and 29 GyD90(SBRT) (p= 0.04 andp< 0.001). For the intermediate-risk CTV, SBRT plans achieved significantly better coverage: mean 18 GyD98and 22 GyD90(SBRT) vs. mean 14 GyD98and 18 GyD90(Syed) (p< 0.001 for both). OAR doses were largely comparable between the two modalities, except that HDR-IBT resulted in significantly lower mean bladder dose and improved bowel sparing, whereas SBRT yielded significantly lower bladder maximum dose and reduced rectumD2cc. Overall, SBRT exhibited greater low-dose spread to surrounding tissues, while HDR-IBT produced higher intratumoral dose hot spots.Conclusion.HDR-IBT remains superior for CTV_HR dose escalation, but SBRT can achieve acceptable target coverage and OAR sparing when brachytherapy is not feasible. SBRT may serve as a practical alternative for selected patients who are medically inoperable, anatomically unsuitable, or lack access to brachytherapy services. Prospective studies are needed to optimize SBRT planning strategies and define appropriate patient selection criteria.

This study evaluates the use of magnetic resonance-guided radiation therapy (MRgRT) as an alternative to brachytherapy in treating para-urethral gynecological cancers, particularly for patients who are not candidates for brachytherapy. Five female patients with advanced para-urethral gynecological cancers underwent MRgRT using a custom 3-dimensional-printed intravaginal cylinder for image registration and treatment alignment. MRgRT was administered as a five-fraction adaptive boost following standard chemoradiation, with each fraction utilizing the cylinder to achieve precise positioning and improve organ sparing. A 1.5T magnetic resonance linear accelerator was used to deliver adapt-to-shape treatment, allowing real-time adjustments to compensate for anatomical variations. The cylinder served not only as a surrogate for accurate image registration but also as a spacer to displace the rectum from high-dose regions. The median follow-up period was 14.4 months, during which all patients completed treatment with no grade >3 genitourinary toxicities. Acute toxicities included dysuria and vaginal pain, while chronic toxicities, such as urinary incontinence and mild cystitis, were recorded in a subset of patients. Treatment achieved an overall survival rate of 100% and a recurrence-free survival rate of 80%. Dosimetric analysis demonstrated effective target coverage with minimal exposure to surrounding organs, particularly sparing the urethra from hotspots, unlike traditional brachytherapy. These results suggest that MRgRT with a vaginal cylinder offers a promising approach for managing para-urethral gynecological cancers in patients ineligible for brachytherapy. Further studies are warranted to validate these findings and refine treatment protocols.

Purpose/Objective(s) Stereotactic body radiotherapy (SBRT) is an established treatment for most oligometastatic cancers. The challenge when treating oligometastatic GYN cancer (OGYNC) is metastases are commonly found near organs at risk (OAR). Therapeutic ratio may be improved using MR-guided radiation therapy (MRgRT) as it offers better soft tissue resolution and onboard adaptation, allowing for safe dose escalation on a mobile target or surrounded by mobile OARs. Few published prospective studies assess the role of Non-MRg SBRT in OGYNC. Reports of acute/late grade 2+ toxicity from the MITO retrospective cohorts range between 5% and 7%. Evidence for MRgRT in OGYNC is limited to small institutional series, and prospective outcomes using this technology have been reported only in a single institution stage I trial with 10 ovarian cancer patients. We report outcomes of the largest retrospective, multicenter cohort of MRgSBRT in patients with OGYNC. Materials/Methods We gathered data from 7 centers located in Miami, Dallas, Istanbul, London, and Munich, and included patients with OGYNC (≤ 5 metastases) treated by MRgSBRT w/wo online adaptation between January 2018 - July 2023. Primary endpoints were local control (LC) and Acute/late toxicities, recorded via version 5.0 of Common Terminology Criteria for Adverse Events (CTCAE). Secondary endpoints were progression free survival (PFS) defined as time from MRgSBRT to1st event: death, locoregional failure (using RECIST 1.1 criteria), or distant failure at 12 months, and overall survival (OS) at 12 months; both estimated using Kaplan-Meier method. Results We obtained data-sharing agreements and identified 81 patients (106 MRgSBRT courses) with a median follow-up of 15 months. Primary diagnoses were Ovary (n = 41), Vagina (n = 3), Uterine (n = 26), Cervix (n = 10). Sites treated included 28 RP lesions (26.4%), 15 intrabdominal (14.2%), 24 pelvic (22.6%), 10 vaginal (9.4%), 10 lung/mediastinal (9.4%), 17 liver/periportal lesions (16%), and 2 supraclavicular nodes (1.9%). Median GTV and PTV size was 8.14 cc (range = 0.5-274cc) and 16.6 cc (2-487cc) respectively. Median prescription dose was 40 Gy (18-60 Gy) in a median 5 (1-10) fractions, and median BED10 of 72 Gy (28-180Gy). Ninety-six MRgSBRT courses were adaptive (90%), of which 6.8% were due to motion management, 25.4% and 16.9% due to PTV or OAR violations respectively, and 32.2% due to violation of both. LC rate was 84.6%, of which 63.5% had complete response (Table 1). Estimated PFS and OS at 12 months were 48% (95% CI = 36-59) and 91% (95% CI = 81-96) respectively. Incidence of grade 2+ toxicity was 2.8% (2 grade 2 acute GI/GU events and 1 grade 3 vertebral fracture). Conclusion We provide the largest cohort to date of OGYNC treated with MRgSBRT, showing that dose escalation with this technology is feasible and well-tolerated with minimal toxicity and ∼85% local control.

PURPOSE: Prospectively measure change in vaginal length after definitive chemoradiation (CEBRT) with Intracavitary Brachytherapy (ICBT) for locally advanced cervix cancer (LACC) and correlate with vaginal dose (VD). MATERIALS AND METHODS: Twenty one female patients with LACC receiving C-EBRT and ICBT underwent serial vaginal length (VL) measurements. An initial measurement was made at the time of the first ICBT procedure and subsequently at 3 month intervals up to 1 year post radiation. The vagina was contoured as a 3 -dimensional structure for each brachytherapy plan. The difference in VL before and at least 6 months after the last fraction of brachytherapy was considered as an indicator of toxicity. RESULTS: The mean initial VL was 8.7 cm (6.5-12) with median value of 8.5 cm. The mean VL after 6 months was 8.6 cm (6.5-12) and VL change was not found to be statistically significant. The median values (interquartile ranges) for vaginal D0.1cc, D1cc, and D2cc were 129.2 Gy (99.6-252.2), 96.9 Gy (84.2-114.9), and 89.6 Gy (82.4-102.2), respectively. No significant correlation was found between vaginal length change and the dosimetric parameters calculated for all patients. CONCLUSION: Definitive C-EBRT and ICBT did not significantly impact VL in this prospective cohort probably related to acceptable doses per ICRU constraints. Estimate of vaginal stenosis and sexual function was not performed in this cohort which is a limitation of this study and which we hope to study prospectively going forward. (c) 2023 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Background: The BEBIG Portio multi-channel applicator provides better target dose coverage and sparing organs-at-risk compared to a single-channel cylinder. However, artifacts and distortions of Portio in magnetic resonance images (MRI) have not yet been reported.Objective: We aimed to quantify the artifacts and distortions in its 1.5-Tesla MR images before clinical use.Material and Methods: In this experimental study, we employed a gelatin-filled phantom to conduct our measurements. T2-weighted (T2W) images were examined for artifacts and distortions. Computed tomography (CT) images were used as a reference to assess image distortions. Artifact severity was measured by recording the full-width-at-half-maximum (FWHM) image pixel values at various positions along the length of the applicator/channels. CT and MRI-based applicator reconstruction accuracy were then compared, and signal-to-noise ratio (SNR) and contrast were also determined for the applicator images.Results: The applicator distortion level for the Portio applicator was less than the image spatial resolution (0.5±0.5 pixels). The average FWHM for the tandem applicator images was 5.23±0.39 mm, while it was 3.21±0.37 mm for all channels (compared to their actual diameters of 5.0 mm and 3.0 mm, respectively). The average applicator reconstruction difference between CT and MR images was 0.75±0.30 mm overall source dwell positions. The image SNR and contrast were both acceptable. Conclusion: These findings indicate that the Portio applicator has a satisfactory low level of artifacts and image distortions in 1.5-Tesla, T2W images. It may, therefore, be a promising option for MRI-guided multi-channel vaginal brachytherapy.

Purpose:Suitable commissioning and quality control (QC) tests for high-dose-rate brachytherapy (HDR-BT) is necessary to ensure dosimetric and geometric accuracy of the treatment. This study aimed to present the methodology of developing a novel multi-purpose QC phantom (AQuA-BT) and examples of its' application in 3D image-based (particularly magnetic resonance imaging [MRI]-based) planning for cervix BT.Material and methods:Design criteria led to a phantom with sufficient size waterproof box for dosimetry and capability for inserting other components inside the phantom for: (A) Validating dose calculation algorithms in treatment planning systems (TPSs) using a small-volume ionization chamber; (B) Testing volume calculation accuracy in TPSs for bladder, rectum, and sigmoid organs at risk (OARs) constructed by 3D printing; (C) Quantification of MRI distortions using 17 semi-elliptical plates with 4,317 control points to mimic a realistic female's pelvis size; and (D) Quantification of image distortions and artifacts induced by MRI-compatible applicators using a specific radial fiducial marker. The utility of the phantom was tested in various QC procedures.Results:The phantom was successfully implemented for examples of intended QC procedures. The maximum deviation between the absorbed doses to water assessed with our phantom and those calculated by SagiPlan TPS was 1.7%. The mean discrepancy in volumes of TPS-calculated OARs was 1.1%. The differences between known distances within the phantom on MR imaging were within 0.7 mm compared with computed tomography.Conclusions:This phantom is a promising useful tool for dosimetric and geometric quality assurance (QA) in MRI-based cervix BT.

BACKGROUND:MRI-only radiotherapy planning (MROP) is beneficial to patients by avoiding MRI/CT registration errors, simplifying the radiation treatment simulation workflow and reducing exposure to ionizing radiation. MRI is the primary imaging modality for soft tissue delineation. Treatment planning CTs (i.e., CT simulation scan) are redundant if a synthetic CT (sCT) can be generated from the MRI to provide the patient positioning and electron density information. Unsupervised deep learning (DL) models like CycleGAN are widely used in MR-to-sCT conversion, when paired patient CT and MR image datasets are not available for model training. However, compared to supervised DL models, they cannot guarantee anatomic consistency, especially around bone.PURPOSE:The purpose of this work was to improve the sCT accuracy generated from MRI around bone for MROP.METHODS:To generate more reliable bony structures on sCT images, we proposed to add bony structure constraints in the unsupervised CycleGAN model's loss function and leverage Dixon constructed fat and in-phase (IP) MR images. Dixon images provide better bone contrast than T2-weighted images as inputs to a modified multi-channel CycleGAN. A private dataset with a total of 31 prostate cancer patients were used for training (20) and testing (11).RESULTS:We compared model performance with and without bony structure constraints using single- and multi-channel inputs. Among all the models, multi-channel CycleGAN with bony structure constraints had the lowest mean absolute error, both inside the bone and whole body (50.7 and 145.2 HU). This approach also resulted in the highest Dice similarity coefficient (0.88) of all bony structures compared with the planning CT.CONCLUSION:Modified multi-channel CycleGAN with bony structure constraints, taking Dixon-constructed fat and IP images as inputs, can generate clinically suitable sCT images in both bone and soft tissue. The generated sCT images have the potential to be used for accurate dose calculation and patient positioning in MROP radiation therapy.

Purpose Prospectively measure change in vaginal length after definitive Chemoradiation (C-EBRT) with Intracavitary Brachytherapy (ICBT) for locally advanced cervix cancer (LACC) and correlate with vaginal dose (VD) Materials and Methods 21 female patients with LACC receiving C-EBRT and ICBT underwent serial vaginal length (VL) measurements. 6 of these women had Hybrid interstitial/intracavitary brachytherapy, the rest had Tandem and ovoid alone. Initial measurement was made at time of first ICBT procedure and subsequently at 3 month intervals till one year post radiation. For consistency the length was defined as distance between external cervical os and the introitus. All patients underwent radiation per ASTRO cervix cancer guidelines. Education regarding the use of vaginal dilator was given to all but compliance was less than 50%. For VD co-relation, the vagina was contoured as a 3- dimensional structure for each brachytherapy plan. All contouring was performed on CT (with MR fusion- if available) using a 0.5-cm fixed brush to outline the vagina around applicator and/or packing, expanded to include any grossly visible vagina. The surface of the cervix was specifically excluded from the contour, but the fornices were included. High-dose-rate (HDR) doses were converted to the equivalent dose in 2-Gy fractions using an α/β of 3 for late effects and added to the dose received by vagina in external beam radiotherapy. The parameters D0.1cc, D1cc, and D2cc and ICRU rectovaginal point dose were calculated for all patients. The difference in VL before and at least 6 months after the last fraction of brachytherapy was considered as an indicator of toxicity. Linear regressions were performed for the generation of Pearson correlation coefficients to explore VD with changes in VL. A Holm-Bonferroni correction was used for all correlations. Results The mean initial VL was 8.7 (6.5 - 12cm) with median value of 8.5. The mean VL after six months was 8.6 (6.5 - 12cm) and VL change was not found to be statistically significant. The median values (interquartile ranges) for vaginal D0.1cc, D1cc, and D2cc were 129.2 (99.6-252.2) Gy, 96.9 (84.2-114.9) Gy, and 89.6 (82.4-102.2) Gy, respectively. No significant correlation was found between vaginal length change and the dosimetric parameters calculated for all patients. The values were within normal range (ICRU 89), ICRU rectovaginal point was higher than 65Gy in 12 of patients but this did not significantly correlate with change in VL. Conclusion Definitive C-EBRT and ICBT did not significantly impact VL in this prospective cohort probably related to acceptable doses per ICRU constraints. Estimate of vaginal stenosis and sexual function was not performed in this cohort which is a limitation of this study and which we hope to study prospectively going forward. Prospectively measure change in vaginal length after definitive Chemoradiation (C-EBRT) with Intracavitary Brachytherapy (ICBT) for locally advanced cervix cancer (LACC) and correlate with vaginal dose (VD) 21 female patients with LACC receiving C-EBRT and ICBT underwent serial vaginal length (VL) measurements. 6 of these women had Hybrid interstitial/intracavitary brachytherapy, the rest had Tandem and ovoid alone. Initial measurement was made at time of first ICBT procedure and subsequently at 3 month intervals till one year post radiation. For consistency the length was defined as distance between external cervical os and the introitus. All patients underwent radiation per ASTRO cervix cancer guidelines. Education regarding the use of vaginal dilator was given to all but compliance was less than 50%. For VD co-relation, the vagina was contoured as a 3- dimensional structure for each brachytherapy plan. All contouring was performed on CT (with MR fusion- if available) using a 0.5-cm fixed brush to outline the vagina around applicator and/or packing, expanded to include any grossly visible vagina. The surface of the cervix was specifically excluded from the contour, but the fornices were included. High-dose-rate (HDR) doses were converted to the equivalent dose in 2-Gy fractions using an α/β of 3 for late effects and added to the dose received by vagina in external beam radiotherapy. The parameters D0.1cc, D1cc, and D2cc and ICRU rectovaginal point dose were calculated for all patients. The difference in VL before and at least 6 months after the last fraction of brachytherapy was considered as an indicator of toxicity. Linear regressions were performed for the generation of Pearson correlation coefficients to explore VD with changes in VL. A Holm-Bonferroni correction was used for all correlations. The mean initial VL was 8.7 (6.5 - 12cm) with median value of 8.5. The mean VL after six months was 8.6 (6.5 - 12cm) and VL change was not found to be statistically significant. The median values (interquartile ranges) for vaginal D0.1cc, D1cc, and D2cc were 129.2 (99.6-252.2) Gy, 96.9 (84.2-114.9) Gy, and 89.6 (82.4-102.2) Gy, respectively. No significant correlation was found between vaginal length change and the dosimetric parameters calculated for all patients. The values were within normal range (ICRU 89), ICRU rectovaginal point was higher than 65Gy in 12 of patients but this did not significantly correlate with change in VL. Definitive C-EBRT and ICBT did not significantly impact VL in this prospective cohort probably related to acceptable doses per ICRU constraints. Estimate of vaginal stenosis and sexual function was not performed in this cohort which is a limitation of this study and which we hope to study prospectively going forward.

PURPOSE: Intracavitary cervical brachytherapy (BT) has transitioned from a two-dimensional nonvolumetric (NV) dosimetry system to three-dimensional computed tomography (CT) and/or magnetic resonance imaging (MRI)-based planning techniques. The purpose of this study is to retrospectively evaluate the relative improvements in image-guided planning strategies over time with regards to dosimetry, survival, and toxicity. METHODS AND MATERIALS: A single site retrospective review of 95 locally advanced cervical cancer patients treated with concurrent chemoradiation and high dose rate BT from 2009 to 2016 were divided into three BT planning groups: point-A based NV dosimetry using CT imaging ( n = 37), CT-based volumetric dosimetry ( n = 33), and MRI-based volumetric dosimetry ( n = 25). Overall survival (OS), progression free survival (PFS), and pelvic control (PC) at 5 years were plotted using Kaplan-Meier curves. Univariate and multivariate (MVA) cox proportional -hazards models calculated hazard-ratios (HZ). Finally, acute and late grade 3-4 toxicities were compared between the cohorts. RESULTS: Both MRI and CT had significantly less D2cc to bowel ( p < 0.001) and sigmoid ( p < 0.001) compared to NV-based planning. On MVA, age ( < 60 vs. > 60 years) was significant for worse 5-year OS (HZ: 2.48) and PC (HZ: 5.25). MRI, with NV as the reference, had significantly improved 5-year OS (HZ: 0.26), PFS (HZ: 0.34) and PC (HZ: 0.16). There was no significant difference in grade > 3 toxicities between the cohorts. CONCLUSIONS: CT and MRI-based 3D planning had significantly less D2cc to bowel and sigmoid. MRI-based planning had significant improvement in 5-year OS, PFS, and LC compared to NV on MVA. (C) 2022 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

PURPOSE: To evaluate an iterative metal-artifact reduction (iMAR) algorithm, dual-energy CT (DECT) through virtual monoenergetic images (VMI), and a combination of iMAR and DECT for reducing metal artifact severity (AS) induced by Fletcher titanium applicators used in cervix brachytherapy, the efficacy of which are hitherto unreported. METHODS AND MATERIALS: 120 kV p single-energy CT (SECT) (Siemens) of BEBIG tandem applicators, varying in shape (straight or curved) and diameter (3.5 mm or 5 mm) in a custom-made water-filled phantom, and their DECT images obtained from extrapolation of 80 kVp and 140 kVp, were reconstructed using four methods: DECT through VMI +/- iMAR, and SECT +/- iMAR. The DECT images were reconstructed monoenergetically at 70, 150, and 190 keV. AS was evaluated using measured values and statistical analysis. RESULTS: iMAR, DECT, and combined DECT and iMAR reduced AS (p < 0.05). DECT had a lower AS than SECT, even without iMAR (p < 0.025). SECT+iMAR was more effective than DECT-iMAR with VMI at 70 and 190 keV (p < 0.05), whereas showing no statistically significant difference at 150 keV. With DECT and iMAR combined, AS was reduced more effectively compared to the SECT+iMAR or DECT alone. It also reduced the mean interobserver uncertainty by 0.2 mm. CONCLUSIONS: These findings indicate that iMAR reduces the AS caused by Fletcher titanium applicators for both SECT and DECT, a combination of iMAR and DECT is superior to either strategy alone, and at low energies, DECT+iMAR also produces similar artifact reduction. These practical strategies promise more accurate source-position and structure definitions in CT-based gynecological brachytherapy treatment planning. (c) 2022 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Background and purpose. Replacing CT imaging with MR imaging for MR-only radiotherapy has sparked the interest of many scientists and is being increasingly adopted in radiation oncology. Although many studies have focused on generating CT images from MR images, only models on data with the same dataset were tested. Therefore, how well the trained model will work for data from different hospitals and MR protocols is still unknown. In this study, we addressed the model generalization problem for the MR-to-CT conversion task. Materials and methods. Brain T2 MR and corresponding CT images were collected from SZSPH (source domain dataset), brain T1-FLAIR, T1-POST MR, and corresponding CT images were collected from The University of Texas Southwestern (UTSW) (target domain dataset). To investigate the model’s generalizability ability, four potential solutions were proposed: source model, target model, combined model, and adapted model. All models were trained using the CycleGAN network. The source model was trained with a source domain dataset from scratch and tested with a target domain dataset. The target model was trained with a target domain dataset and tested with a target domain dataset. The combined model was trained with both source domain and target domain datasets, and tested with the target domain dataset. The adapted model used a transfer learning strategy to train a CycleGAN model with a source domain dataset and retrain the pre-trained model with a target domain dataset. MAE, RMSE, PSNR, and SSIM were used to quantitatively evaluate model performance on a target domain dataset. Results. The adapted model achieved best quantitative results of 74.56 ± 8.61, 193.18 ± 17.98, 28.30 ± 0.83, and 0.84 ± 0.01 for MAE, RMSE, PSNR, and SSIM using the T1-FLAIR dataset and 74.89 ± 15.64, 195.73 ± 31.29, 27.72 ± 1.43, and 0.83 ± 0.04 for MAE, RMSE, PSNR, and SSIM using the T1-POST dataset. The source model had the poorest performance. Conclusions. This work indicates high generalization ability to generate synthetic CT images from small training datasets of MR images using pre-trained CycleGAN. The quantitative results of the test data, including different scanning protocols and different acquisition centers, indicated the proof of this concept.

PURPOSE: The purpose of this study is to compare the predicted rate of local control and bladder and rectum toxicity rates for image-guided adaptive brachytherapy plans using a tandem and ovoid (T/O) applicator versus using a simulated hybrid intracavitary/interstitial tandem and ring applicator with needles (T/R + N) for patients with locally advanced cervical cancer (LACC). METHODS AND MATERIALS: Patients with >= FIGO Stage IIB locally advanced cervical cancer treated with T/O from a single institution were included. Simulated treatment plans were created with a T/R + N applicator for the best high-risk clinical target volume (CTV) coverage and minimal dose to organs at risk. Three-year local control rate was estimated using published dose-volume effect relationships. Next, the high-risk CTV EQD2 D90 of T/R + N plans were calculated, and bladder and rectum toxicity rates were estimated. Analysis was performed in subpatient groups defined based on tumor volume and ratio of maximal and minimal tumor radii (RR) that reflects tumor shape asymmetry. RESULTS: Improvements in predicted local control rate for the T/R + N were 0.8, 4.1, 1.6, and 3.9% for groups with tumor volume <35 cc, >= 35 cc, RR < 2.0, and >= 2.0, respectively, with the latter three being statistically significant. Predicted reductions in Grade 2-4 toxicity rates of bladder and rectum were significant in all groups except bladder toxicity in tumor volume < 35 cc, when T/R + N plans were normalized to the same CTV coverage as the T/O plans. Comparing unnormalized T/R + N plans and T/O plans, predicted toxicity reductions were significant in all groups except rectum toxicity in RR >= 2.0. Predicted reduction of toxicity rate was larger for patients with large tumor or large tumor RR, although some reductions were relatively small. CONCLUSIONS: Cases with large tumor (volume >= 35 cc) or large tumor asymmetry (RR >= 2.0) would probably benefit more from the use of hybrid applicators. (c) 2021 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

AbstractPurposeThe purpose of this study was to address the dosimetric accuracy of synthetic computed tomography (sCT) images of patients with brain tumor generated using a modified generative adversarial network (GAN) method, for their use in magnetic resonance imaging (MRI)‐only treatment planning for proton therapy.MethodsDose volume histogram (DVH) analysis was performed on CT and sCT images of patients with brain tumor for plans generated for intensity‐modulated proton therapy (IMPT). All plans were robustly optimized using a commercially available treatment planning system (RayStation, from RaySearch Laboratories) and standard robust parameters reported in the literature. The IMPT plan was then used to compute the dose on CT and sCT images for dosimetric comparison, using RayStation analytical (pencil beam) dose algorithm. We used a second, independent Monte Carlo dose calculation engine to recompute the dose on both CT and sCT images to ensure a proper analysis of the dosimetric accuracy of the sCT images.ResultsThe results extracted from RayStation showed excellent agreement for most DVH metrics computed on the CT and sCT for the nominal case, with a mean absolute difference below 0.5% (0.3 Gy) of the prescription dose for the clinical target volume (CTV) and below 2% (1.2 Gy) for the organs at risk (OARs) considered. This demonstrates a high dosimetric accuracy for the generated sCT images, especially in the target volume. The metrics obtained from the Monte Carlo doses mostly agreed with the values extracted from RayStation for the nominal and worst‐case scenarios (mean difference below 3%).ConclusionsThis work demonstrated the feasibility of using sCT generated with a GAN‐based deep learning method for MRI‐only treatment planning of patients with brain tumor in intensity‐modulated proton therapy.

Purpose: Correct commissioning of treatment planning systems (TPSs) is important for reducing treatment failure events. There is currently no comprehensive and robust methodology available for TPS commissioning in modern brachytherapy. This review aimed to develop a comprehensive template for commissioning modern 3D-image-based brachytherapy TPSs for high dose rate (HDR) gynaecological applications. Methods: The literature relevant to TPS commissioning, including both external beam radiation therapy (EBRT) and brachytherapy, as well as guidelines by the International Atomic Energy Agency (IAEA), the American Association of Physicists in Medicine (AAPM), and the European Society for Radiotherapy and Oncology (ESTRO) were searched, studied and appraised. The applied relevant EBRT TPS commissioning tests were applied to brachytherapy. The developed template aimed to cover all dosimetric and non-dosimetric issues. Results: The essential commissioning items could be categorized into six parts: geometry, dose calculation, plan evaluation tools, plan optimization, TPS output, and end-to-end verification. The final template consists of 43 items. This paper presents the purpose and role of each test, as well as tolerance limits, to facilitate the use of the template. Conclusion: The information and recommendations available in a collection of publications over many years have been reviewed in order to develop a comprehensive template for commissioning complex modern 3D-image-based brachytherapy TPSs for HDR gynaecological applications. The up-to-date and concise information contained in the template can aid brachytherapy physicists during TPS commissioning as well as devising a regular quality assurance program and allocation of time and resources.