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Background Purpose Methods and materials Results Conclusion Stereotactic arrythmia radioablation (STAR) is a noninvasive technique to treat ventricular tachycardia (VT). Management of cardiorespiratory motion plays an essential role in VT‐STAR treatments to improve treatment outcomes by reducing positional uncertainties and increasing dose conformality. Use of an electrocardiogram (ECG) signal, acquired in real‐time, as a surrogate to gate the beam has the potential to fulfil that intent.To investigate the gated delivery of volumetric‐modulated arc therapy (VMAT) for STAR on a TrueBeam linear accelerator (linac) using a real‐time acquired ECG signal and a dynamic cardiac phantom.Dosimetric characteristics of a 6 MV flattening filter free (FFF) beam from a Varian TrueBeam linac were initially evaluated under high‐frequency gating scenarios relevant to cardiac rhythms with respect to dose linearity, beam output, and energy quality. A microcontroller board was used to interface and gate the linac, sending a beam on/off signal. For real‐time cardiac gated measurements, an AD8232 Heart Monitor board was used to acquire the ECG signal and synchronize the VMAT delivery to an ArcCHECK detector to a specific phase of the cardiac cycle. Gated dose distributions were compared against those acquired for a non‐gated delivery mode. An in‐house dynamic cardiac phantom was developed to simulate cardiorespiratory motion that correlates target position with the signal to gate the beam. Measured dose distributions using gafchromic film were also compared against the static (reference) mode in different scenarios with and without gating.Maximum difference in dose per monitor unit (MU) was found to be no greater than 1% as compared to static mode with variation in the chamber response within 0.2% in the range of 50 MUs to 200 MUs. Maximum percentage differences for the beam output and beam qualiy index (TPR20,10) between gated and non‐gated modes were 0.91% and ‐0.44%, respectively. Comparison of delivered dose distributions for the VMAT plan without gating versus ECG synchronized gating modes provided a passing rate 98% for the gamma analysis with 1% relative dose difference, 1 mm distance‐to‐agreement criteria. For the synchronization of dose delivery with target position, passing rates were 98%, 97%, and 99% for the axial, coronal, and sagittal planes, respectively, when gating the beam based on target position for cardiac motion only, for 3%, 3 mm tolerance as compared to static mode. Without gating the beam, passing rates of the respective plans are 97%, 94%, and 99% for the cardiac motion only, and 67%, 57%, and 55% when including respiratory component of motion.A 6 MV‐FFF TrueBeam is stable for performing gating in STAR under high‐frequency gate windows within typical cardiac cycles. Agreement between measured dose distributions for a VMAT plan in static and ECG‐synchronized deliveries and between static and target‐position gated modes shows that the proposed methodology is feasible and can be implemented on a TrueBeam platform. [ABSTRACT FROM AUTHOR]

Objective: Compared the dosimetric characteristics of half-field-based VMAT and half-field-based IMRT for left breast cancer patients combined with deep inspiration breath-hold (DIBH) and free breathing (FB) techniques. Methods: Twenty-one left breast cancer patients were included. Each patient underwent DIBH and FB CT scans, IMRT and VMAT plans in half-field beam mode for both breathing techniques, resulting in four plans: FB-IMRT (F-IMRT), FB-VMAT (F-VMAT), DIBH-IMRT (D-IMRT) and DIBH-VMAT (D-VMAT). The conformity index (CI), homogeneity index (HI), and the doses received at the heart, left anterior descending (LAD), left lung, right breast, and right lung, were compared among plans.The correlation between the difference in the volume of lung_L (ΔLVL) and the difference in the mean dose (ΔDmean) of lung_L under the DIBH and FB plans, the correlation between the difference in the heart-chest distance (ΔHCD) and the ΔDmean of the heart,LAD under the DIBH and FB plans. Results: The D-VMAT plan lower lung_L V5 than both the F-IMRT and F-VMAT plans (p <0.05), The D-VMAT plan lower values for V10, V20, V30, and Dmean than did the other plans (p < 0.05). For the heart, the D-VMAT plan lower V5, V10, V20, and Dmean values than did the other plans (p < 0.05). The D1% and Dmax of the heart and the Dmax and Dmean of the LAD obtained with the D-VMAT plan were lower than those obtained with the F-IMRT and F-VMAT plans (p < 0.05). ΔHCD exhibited correlation with the ΔDmean of the LAD between the D-VMAT and F-IMRT plans and between the D-VMAT and F-VMAT plans (R = -0.765 and -0.774, respectively, p = 0.000). Conclusion: the D-VMAT plan offered enhanced protection for OARs. The integration of the DIBH technique with half-field and VMAT technology in the D-VMAT plan offers a superior dose distribution. [ABSTRACT FROM AUTHOR]

This study aimed to investigate whether the RapidPlan (RP) model configured by volumetric modulated arc therapy (VMAT) plans of nasopharyngeal carcinoma (NPC) could be used to assist in the optimization of HT plans and improve their quality. An RP model was trained using 100 clinically accepted VMAT plans of NPC patients. The predicted dose constraints of the VMAT trained RP model were used to reoptimize 25 consecutive clinically accepted HT plans (HT_clinical) and perform new VMAT plans based on the same computed topography (CT). The dosimetric quality of the reoptimized HT plans (HT_reoptimized), HT_clinical, and VMAT group were compared. The minimum dose encompassing 2% target (D 2%), the minimum dose encompassing 98% target (D 98%), homogeneity index (HI) and conformity index (CI) were similar for most targets between the HT_clinical and HT_reoptimized plans, although certain targets in the HT_reoptimized plans had higher D 2% and HI and lower D 98%. The HT_reoptimized plans outperformed the HT_clinical plans in the Dmax and D1cc of the spinal cord, V 40Gy of the left temporal lobe, Dmean and V 30Gy of the oral cavity, Dmean of the larynx and thyroid, and the differences were statistically significant. HT plans had higher CI and HI than VMAT plans. HT plans outperformed VMAT plans in the Dmax of the spinal cord and lenses, V 30Gy of the oral cavity and parotids, and V 40Gy of the temporal lobes, but underperformed in the Dmax and D1cc of the brainstem, D1cc of the spinal cord and Dmean of the oral cavity. The VMAT-based RP model can be used to assist in the planning of HT plans and improve the dosimetry quality of HT plans. [ABSTRACT FROM AUTHOR]

Increasing numbers of dogs and cats with cancer are treated with stereotactic radiosurgery, stereotactic radiation therapy or stereotactic body radiotherapy (SRS, SRT or SBRT). We provide a systematic review of the current data landscape with a focus on technical and dosimetric data of stereotactic radiotherapy in veterinary oncology. Original peer‐reviewed articles on dogs and cats with cancer treated with SRT were included. The systematic search included Medline via PubMed and EMBASE. The study was performed according to the Preferred Reporting Items for Systematic Reviews (PRISMA) statement. We assessed the manuscripts regarding outcome reporting, treatment planning, dose prescription, ‐delivery and ‐reporting as well as quality assurance. As of February 2024, there are 80 peer‐reviewed publications on various disease entities on SRS, SRT and SBRT in veterinary medicine. Overall, we found often insufficient or highly variable technical data, with incomplete information to reproduce these treatments. While in some instances, technical factors may not impact clinical outcome, the variability found in protocols, outcome and toxicity assessments precludes accurate and reliable conclusions for a benefit of stereotactic radiotherapy for many of the treated diseases. In line with the extensive recommendations from human stereotactic radiotherapy practise, we propose a draft of reporting items for future stereotactic radiation treatments in veterinary medicine. SRS, SRT and SBRT have specific clinical and technological requirements that differ from those of standard radiation therapy. Therefore, a deep understanding of the methodologies, as well as the quality and precision of dose delivery, is essential for effective clinical knowledge transfer. [ABSTRACT FROM AUTHOR]

Intensity-modulated radiation therapy or volumetric-modulated arctherapy is nowadays the recommended radiation technique for the treatment of head and neck cancers. However, by providing a significant dose gradient between target volumes and organs at risk, there is a risk of target missing and thus recurrence in case of inadequate delineation. It is therefore necessary to determine the origin of these recurrences to improve clinical practice. Over the past years, different methods have been described for the analysis of recurrences. Using the patterns of failure of patients with oral cavity and oropharynx carcinoma, treated with postoperative volumetric-modulated arctherapy in our institution, the purpose of this work was to analyse the sites of local recurrences and to evaluate the disparity in the classification of recurrences when different methods were used. Between 2011 and 2019, 167 patients who underwent postoperative volumetric-modulated arctherapy for oral cavity or oropharyngeal cancers were included (60 and 40 % respectively). Two or three dose levels were prescribed (54 Gy, 59.4/60 Gy ± 66 Gy). Local recurrence occurred in 17 patients (10.2 %). We assessed the patterns of local recurrences according to four methods: 1/ volume-based method using the volume overlap between the recurrence volume and initial target volumes; 2/ volume-based method of overlap between the recurrence volume and the 95 % treatment isodose; 3/ point-based method using the position of the barycentre of the recurrence volume; 4/ combined centroid method classifying recurrences according to both the initial target volumes and dose distribution. Each case was reviewed to make a clinical judgment on these classifications and assessed them as "appropriate", "possible", or "inappropriate". For the volume-based method using overlap between the recurrence volume and the initial clinical target volume, this classification was clinically judged as inappropriate in 11 out of 17 cases (65 %). For the volume-based method using overlap between the recurrence volume and the 95 % prescribed isodose, this classification was clinically judged as appropriate in 15 out of 17 cases (88 %). For the point-based method, this classification was clinically judged as appropriate in 14 out of 17 cases (82 %). Thirteen out of 17 local recurrences had the same classification between this point-based method and the volume-based method of overlap between the recurrence volume and the 95 % prescribed isodose. For the combined centroid method, among 17 local recurrences nine were classified as type A, two as type B, two as type C, three as type D and one as type E. This classification was clinically judged as appropriate in 15 out of 17 cases (88 %). Only five out of 17 of the local recurrences were classified the same way according to the four different methods (29 %). Recurrences that are "marginal" or "outfield" represent a major challenge for intensity-modulated radiation therapy/volumetric-modulated arctherapy quality assurance and improvement of delineation recommendations. To date, there are no published methods that give complete satisfaction. [ABSTRACT FROM AUTHOR]

Purpose: To investigate risk factors for esophageal fistula in esophageal squamous cell cancer (ESCC) patients who treated with volumetric modulated arc therapy (VMAT). Patients and Methods: A retrospective analysis was performed on 171 ESCC patients treated with VMAT at Hefei Cancer Hospital, Chinese Academy of Sciences, from February 2017 to February 2021. Clinical and dosimetric parameters, including age, gender, feeding channel, tumor location, T stage, ulcerative tumor, were recorded. Univariate and multivariate logistic regression were used to determine risk factors for esophageal fistula. The predictive accuracy of the constructed nomogram was assessed using a receiver operating characteristic (ROC) curve and calibration curves. Results: Esophageal fistula occurred in 12.87% (22/171) of all the patients. Univariate analysis showed that gender, age, diabetes, T4 stage, ulcerative tumor, total radiation dose, maximum gross tumor volume (GTV) diameter, and GTV length correlated with the incidence of esophageal fistula. Multivariable analysis highlighted gender, age, diabetes, T4 stage, and total radiation dose as significant predictors. A predictive nomogram including these five factors was developed and showed an AUC of 0.876 (95% CI 0.807– 0.946), a C-index of 0.847, and a corrected C-index of 0.833. Conclusion: Gender, age, diabetes, T4 stage, and total radiation dose emerged as significant risk factors for esophageal fistula in ESCC patients undergoing VMAT. The developed nomogram provides a reliable tool to predict the risk of esophageal fistula risk in this cohort. [ABSTRACT FROM AUTHOR]

To develop and assess an automated Sub-arc Collimator Angle Optimization (SACAO) algorithm and Cumulative Blocking Index Ratio (CBIR) metrics for single-isocenter coplanar volumetric modulated arc therapy (VMAT) to treat multiple brain metastases. This study included 31 patients with multiple brain metastases, each having 2 to 8 targets. Initially, for each control point, the MLC blocking index was calculated at different collimator angles, resulting in a two-dimensional heatmap. Optimal sub-arc segmentation and collimator angle optimization were achieved using an interval dynamic programming algorithm. Subsequently, VMAT plans were designed using two approaches: SACAO and the conventional Full-Arc Fixed Collimator Angle. CBIR was calculated as the ratio of the cumulative blocking index between the two plan approaches. Finally, dosimetric and planning parameters of both plans were compared. Normal brain tissue, brainstem, and eyes received better protection in the SACAO group (P < 0.05).Query Notable reductions in the SACAO group included 11.47% in gradient index (GI), 15.03% in monitor units (MU), 15.73% in mean control point Jaw area (AJaw,mean), and 19.14% in mean control point Jaw-X width (WJaw-X,mean), all statistically significant (P < 0.001). Furthermore, CBIR showed a strong negative correlation with the degree of plan improvement. The SACAO method enhanced protection of normal organs while improving transmission efficiency and optimization performance of VMAT. In particular, the CBIR metrics show promise in quantifying the differences specifically in the 'island blocking problem' between SACAO and conventional VMAT, and in guiding the enhanced application of the SACAO algorithm. [ABSTRACT FROM AUTHOR]

Xiujuan Gai,1– 3,&ast; Shiqi Huang,1,2,&ast; Jiang Zeng,1,2,4 Jun Chen,1,2,4 Feng Liu,1,2,4 Shan Li,1,2,4 Wenlong Lv,1,2,4 Feibao Guo,1,2,4 Chuanshu Cai,1,2,4 Jinsheng Hong,1,2,4 Li Su1,2,4 1Department of Radiotherapy, Cancer Center, The First Affiliated Hospital of Fujian Medical University, Fuzhou, 350005, People’s Republic of China; 2Department of Radiotherapy, National Regional Medical Center, Binhai Campus of the First Affiliated Hospital, Fujian Medical Universisty, Fuzhou, Fujian, 350212, People’s Republic of China; 3Department of Oncology, Laiyang Central Hospital of Yantai, Yantai, 265200, People’s Republic of China; 4Key Laboratory of Radiation Biology of Fujian Higher Education Institutions, The First Affiliated Hospital, Fujian Medical University, Fuzhou, 350005, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Li Su; Jinsheng Hong, Department of Radiotherapy, Cancer Center, The First Affiliated Hospital of Fujian Medical University, Fuzhou, 350005, People’s Republic of China, Email lily2230@126.com; 13799375732@163.comPurpose: To investigate the impact of Intensity-Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) on hippocampal radiation dosage and psychological status in patients newly diagnosed with nasopharyngeal carcinoma (NPC).Patients and Methods: A retrospective analysis was conducted on 269 NPC patients who received initial treatment between January 2013 and April 2022. Patients were categorized into the IMRT group and the VMAT group based on the radiotherapy technique employed. The differences in hippocampal doses for NPC patients at different stages between the two groups were analyzed. The Hospital Anxiety and Depression Scale (HADS) was used to assess patients’ anxiety and depression states. Before radiotherapy, patients with anxiety scores (HADS-A) between 0 and 10 points were included to analyze the differences in anxiety occurrence rates between IMRT and VMAT techniques. Similarly, patients with depression scores (HADS-D) between 0 and 10 points were included to analyze the differences in depression occurrence rates between the two radiotherapy techniques.Results: In patients with T1-2 stage, those treated with IMRT had significantly higher hippocampal doses compared to those treated with VMAT. Furthermore, after radiotherapy, the occurrence rates of anxiety (HADS-A ≥ 11) and depression (HADS-D ≥ 11) in the IMRT group were 27.3% and 19.5%, respectively, while in the VMAT group, they were 9.5% and 7.4%, both showing significant statistical differences (P=0.010, P=0.035). However, there was no significant correlation between the radiotherapy technique and anxiety or depression occurrence rates in patients with T3-4 stage. Additionally, age and gender exhibited certain influences on psychological status.Conclusion: In the absence of hippocampal protection, opting for a VMAT treatment plan over IMRT may potentially reduce the incidence of anxiety and depression. This perspective offers new insights for optimizing treatment strategies and improving quality of life.Keywords: nasopharyngeal carcinoma, IMRT, VMAT, hippocampal doses, psychological status

Oligometastatic breast cancer patients can today could benefit from a multimodal approach, combining systemic therapy with metastasis-directed treatment using stereotactic body radiotherapy (SBRT). However, the possibility to synchronously treat multiple lesions is still challenging, needing the ability to generate complex dose distributions with steep dose gradients outside the lesions and major sparing of surrounding organs at risk and accurately track and reproduce the patient's position before and during radiation therapy. We report the case of an oligometastatic patient from left breast cancer, which occurred after a full course of whole breast radiotherapy, treated using the potential of modern technology including single-isocenter setup, plan automation, breath-hold technique and surface guided tracking and reproducibility of patient's position before and during radiation therapy. A 44-year-old female patient with a history of left breast cancer, specifically a luminal-B-like invasive ductal carcinoma with Her2 overexpression, was admitted to our department. The patient previously underwent a left mastectomy (pT2N0M0), 4 cycles of adjuvant chemotherapy, adjuvant radiotherapy on the chest wall and lymph nodes drainage, and 5 years of hormonal therapy. A chest wall ultrasound and positron emission tomography revealed the presence of new lesions in the area of the surgical scar from the previous mastectomy, internal mammary, axillary and retropectoral levels. The 3 lesions were simultaneously treated with a mono-isocentric VMAT plan using SBRT technique with a total dose of 30 Gy delivered in 5 fractions. Due to the technical challenges, this treatment was supported by the use of planning automation, breath-hold technique and surface-guided radiation therapy to improve the accuracy of the dose delivery. Two different plans were generated and compared to pursue the best dosimetric result, including a summed plan obtained from 3 individual SBRT plans for each lesion with a separate isocenter placed in each of them (MIP), and a single-isocenter SBRT plan able to treat multiple lesions synchronously (SIP). Because of the advantages in terms of dosimetry and dose delivery efficiency, the patient was successfully treated with the SIP plan. The treatment time was reduced to about 4.5 minutes, allowing the comfortably use of breath-hold technique. After treatment, the condition of the patient was normal, and no toxicities have been observed in follow-up. SBRT with mono isocentric VMAT planning represents the recommended approach to simultaneously treat multiple lesions in close proximity in the thoracic district. [ABSTRACT FROM AUTHOR]

Purpose: Volumetric modulated arc therapy (VMAT) is a widespread technique for the delivery of normo-fractionated radiation therapy (NFRT) and stereotactic body radiation therapy (SBRT). It is associated with a significant hardware burden requiring dose rate modulation, collimator movement and gantry rotation synchronisation. Patient specific quality assurance (PSQA) guarantees that the linacs can precisely and accurately deliver the planned dose. However, PSQA requires a significant time allocation and class solutions to reduce this while guaranteeing the deliverability of the plans should be investigated. Methods: In this study, an in-house developed Eclipse Scripting API (ESAPI) script was used to extract five independent plan complexity metrics from N = 667 VMAT treatment fields. The correlation between metrics and portal dosimetry measurements was investigated with Pearson correlation, box plot analysis and receiver operating characteristic curves, which were used to defined the best performing metric and its threshold. Results: The incidence of fields failing the clinical PSQA criteria of 3%/2mm (NFRT) and 3%/1.5mm (SBRT) was low (N = 1). The mean MLC opening was the metric with the highest correlation with the portal dosimetry data and among the best in discriminating the requirement of PSQA. The thresholds of 16.12 mm (NFRT) and 7.96 mm (SBRT) corresponded to true positive rates higher than 90%. Conclusions: This work presents a quantitative approach to reduce the time allocation for PSQA by identifying the most complex plans demanding a dedicated measurement. The proposed method requires PSQA for approximately 10% of the plans. The ESAPI script is distributed open-source to ease the investigation and implementation at other institutions.

Introduction: This study aims to compare tangential volumetric modulated arc therapy with half beam volumetric modulated arc therapy in the treatment of cancer in the left and right breasts. Material and Methods: Twenty patients (10 with left and 10 with right breast cancer) were planned with Tangential Volumetric Modulated Arc Therapy (tVMAT) and Half Beam Volumetric Modulated Arc Therapy (HVMAT) techniques for prescribed dose of 42.56Gy over 16 fractions with 6MV photon. The tVMAT technique limit the radiation to non-target areas. Dosimetric evaluations were performed for planning target volume (PTV), ipsilateral lung, heart, and contralateral breast with analysis via Repeated Measures ANOVA with a significance level of 5%. Results: tVMAT achieved superior target coverage and dose homogeneity compared to HVMAT. For left breast cancer, HVMAT reduced ipsilateral lung doses but increased contralateral breast doses. Heart doses remained similar in both techniques. For right breast cancer, tVMAT provided higher target coverage and reduced doses across critical parameters. Conclusion: tVMAT demonstrates strong potential as an advanced radiotherapy technique for breast cancer, improving dose control to the ipsilateral lung and heart while minimizing dose spread to the contralateral side, making it a promising alternative to conventional VMAT for enhanced precision in breast cancer treatment.

Abstract Background Volumetric modulated arc therapy (VMAT) planning optimization involves iterative adjustment of numerous parameters, and hence requires repeatedly dose recalculation. In this study, we used the deep learning method to develop a fast and accurate dose calculation method for VMAT. Methods The classical 3D UNet was adopted and trained to learn the physics principle of dose calculation. The inputs included the projected fluence map (FM), computed tomography (CT) images, the radiological depth and the source-to-voxel distance (SVD). The projected FM was generated by projecting the accumulated FM between two consecutive control points (CPs) onto the patient’s anatomy. The accumulated FM was calculated by simulating the movement of the multi-leaf collimator (MLC) from one CP to the next. The dose, calculated by the treatment planning system (TPS), was used as ground truth. 51 head and neck VMAT plans were used, with 43, 1 and 7 cases as training, validation, and testing datasets, respectively. Correspondingly, 7182, 180 and 1260 CP samples were included in the training, validation, and testing datasets. Results This presented method was evaluated by comparing the derived dose distribution to the TPS calculated dose distribution. The dose profiles coincided for both the single CP and the entire plan (summation of all CPs). But the network derived dose was smoother than the TPS calculated dose. Gamma analysis was performed between the network derived dose and the TPS calculated dose. The average gamma pass rate was 96.56%, 98.75%, 98.03% and 99.30% under the criteria of 2% (tolerance) -2 mm (distance to agreement, DTA). 2%-3 mm, 3%-2 mm and 3%-3 mm. No significant difference was observed on the critical indices including the max, mean dose, and the relative volume covered by the 2000 cGy, 4000 cGy and the prescription dose. For one CP, the average computational time of the network and TPS was 0.09s and 0.53s. And for one patient, the average time was 16.51s and 95.60s. Conclusion The dose distribution derived by the network showed good agreement with the TPS calculated dose distribution. The computational time was reduced to approximate one-sixth of its original duration. Therefore the presented deep learning-based dose calculation method has the potential to be used for planning optimization.

Simple Summary: In recent years, advanced radiotherapy techniques such as intensity-modulated radiation therapy (IMRT) and simultaneous integrated boost (SIB) irradiation have played a key role in enhancing the precision of radiation delivery to tumors. However, these advancements have also increased the complexity of treatment planning by involving a trial-and-error approach, resulting in greater variability between operators and longer planning times. The automation of planning processes has shown promise in standardizing treatment plans while maintaining their quality and reducing workload. Additionally, deep learning-based fully automated planning solutions have become a significant focus of research in radiation oncology. In this study, we propose a single, end-to-end pipeline for normo-fractionated prostate-only and whole-pelvic cancer treatments, requiring minimal human input and producing a machine-deliverable volumetric modulated arc therapy (VMAT) plan. A comprehensive clinical evaluation was performed, incorporating both dosimetric analysis and plan deliverability assessment. Background/Objectives: To evaluate an end-to-end pipeline for normo-fractionated prostate-only and whole-pelvic cancer treatments that requires minimal human input and generates a machine-deliverable plan as an output. Methods: In collaboration with TheraPanacea, a treatment planning pipeline was developed that takes as its input a planning CT with organs-at-risk (OARs) and planning target volume (PTV) contours, the targeted linac machine, and the prescription dose. The primary components are (i) dose prediction by a single deep learning model for both localizations and (ii) a direct aperture VMAT plan optimization that seeks to mimic the predicted dose. The deep learning model was trained on 238 cases, and a held-out set of 86 cases was used for model validation. An end-to-end clinical evaluation study was performed on another 40 cases (20 prostate-only, 20 whole-pelvic). First, a quantitative evaluation was performed based on dose–volume histogram (DVH) points and plan parameter metrics. Then, the plan deliverability was assessed via portal dosimetry using the global gamma index. Additionally, the reference clinical manual plans were compared with the automated plans in terms of monitor unit (MU) numbers and modulation complexity scores (MCSv). Results: The automated plans provided adequate treatment plans (or minor deviations) with respect to the dose constraints, and the quality of the plans was similar to the manual plans for both localizations. Moreover, the automated plans showed successful deliverability and passed the portal dose verification. Despite higher median total MUs, no statistically significant correlation was observed between any of the gamma criteria tested and the number of MUs or MCSv. Conclusions: This study shows the feasibility of a deep learning-based fully automated treatment planning pipeline that generates high-quality plans that are competitive with manually made plans and are clinically approved in terms of dosimetry and machine deliverability. [ABSTRACT FROM AUTHOR]

This study compares dosimetric outcomes of high-dose-rate (HDR) interventional radiotherapy (IRT) using Iridium-192, Volumetric Modulated Arc Therapy (VMAT), and electron beam therapy for non-melanoma skin cancer (NMSC). A retrospective analysis of 25 patients showed that IRT provided a significantly higher mean dose to the clinical target volume (CTV) compared to VMAT and electron beam therapy. IRT and VMAT had comparable V95%CTV coverage, whilst electron therapy was less feasible for large CTVs. IRT delivered higher surface doses while minimizing deep tissue exposure compared to partial arc VMAT. Our findings support IRT for personalized and effective NMSC treatment. [ABSTRACT FROM AUTHOR]

Background: Delivery variations during radiotherapy can cause discrepancies between planned and delivered dose distribution. These variations could arise from random and systematic offsets in certain machine parameters or systematic offsets related to the calibration process of the treatment unit. Purpose: The aim of this study was to present a novel simulation‐based methodology to evaluate realistic delivery variations in three dimensions (3D). Additionally, we investigated the dosimetric impact of delivery variations for volumetric modulated arc therapy (VMAT) plans for different treatment sites and complexities. Methods: Twelve VMAT plans for different treatment sites (prostate‐, head & neck‐, lung‐, and gynecological cancer) were selected. The clinical plan used for the treatment of each patient was reoptimized to create one plan with reduced complexity (i.e., simple plan) and one of higher complexity (i.e., complex plan). This resulted in a total of 36 plans. Delivery variations were simulated by randomly introducing offsets in multi‐leaf collimator position, jaw position, gantry angle and collimator angle simultaneously. Twenty simulations were carried out for each of the 36 plans, yielding 720 simulated deliveries. To explore the impact of individual offsets, additional simulations were conducted for each type of offset separately. A 3D dose calculation was performed for each simulation using the same calculation engine as for the clinical plan. Two standard deviations (2SD) of dose were determined for every voxel for 3D‐spatial evaluations. The dose variation in certain DVH metrics, that is, D2% and D98% for the clinical target volume and five different DVH metrics for selected organs at risk, was calculated for the twenty simulated deliveries of each plan. For comparison, the effect of delivery variations was assessed by conducting measurements with the Delta4 phantom. Results: The volume of voxels with 2SD above 1% of the prescribed dose was consistently larger for the complex plans in comparison to their corresponding simple and clinical plans. 2SDs larger than 1% were in many cases, found to accumulate outside the planning target volume. For complex plans, regions with 2SDs larger than 1% were detected also inside the high dose region, exhibiting, on average, a size six times larger volume, than those observed in simple plans. Similar results were found for all treatment sites. Variation in the selected DVH metrics for the simulated deliveries was generally largest for the complex plans with few exceptions. When comparing the 2SD distribution of the measurements with the 2SD distribution from the simulations, the spatial information showed deviations outside the PTV in both simulations and measurements. However, the measured values were, on average, 35% higher for the prostate plans and 10% higher for the head & neck plans compared to the simulated values. Conclusions: The presented methodology effectively quantified and localized dose deviations due to delivery offsets. The 3D analysis provided information that was undetectable using the analysis based on DVH metrics. Dosimetric uncertainties due to delivery variations were prominent at the edge of the high‐dose region irrespective of treatment site and plan complexity. Dosimetric uncertainties inside the high‐dose region was more profound for plans of higher complexity. [ABSTRACT FROM AUTHOR]

Volumetric modulated arc therapy (VMAT) is a widespread technique for the delivery of normo-fractionated radiation therapy (NFRT) and stereotactic body radiation therapy (SBRT). It is associated with a significant hardware burden requiring dose rate modulation, collimator movement and gantry rotation synchronisation. Patient specific quality assurance (PSQA) guarantees that the linacs can precisely and accurately deliver the planned dose. However, PSQA requires a significant time allocation and class solutions to reduce this while guaranteeing the deliverability of the plans should be investigated. In this study, an in-house developed Eclipse Scripting API (ESAPI) script was used to extract five independent plan complexity metrics from N = 667 VMAT treatment fields. The correlation between metrics and portal dosimetry measurements was investigated with Pearson correlation, box plot analysis and receiver operating characteristic curves, which were used to defined the best performing metric and its threshold. The incidence of fields failing the clinical PSQA criteria of 3%/2mm (NFRT) and 3%/1.5mm (SBRT) was low (N = 1). The mean MLC opening was the metric with the highest correlation with the portal dosimetry data and among the best in discriminating the requirement of PSQA. The thresholds of 16.12 mm (NFRT) and 7.96 mm (SBRT) corresponded to true positive rates higher than 90%. This work presents a quantitative approach to reduce the time allocation for PSQA by identifying the most complex plans demanding a dedicated measurement. The proposed method requires PSQA for approximately 10% of the plans. The ESAPI script is distributed open-source to ease the investigation and implementation at other institutions. [ABSTRACT FROM AUTHOR]

The aim of this work was to evaluate the conformity of intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), and verify the accuracy of the planning and delivery system used in this work based on the AAPM TG-119 protocol. The Eclipse 13.6 treatment planning system (TPS) was used to plan the TG-119 test suite, which included four test cases: MultiTarget, Prostate, Head/Neck, and C-Shape for IMRT and VMAT techniques with 6 MV and 10 MV acceleration voltages. The results were assessed and discussed in terms of the TG-119 protocol and the results of previous studies. In addition, point dose and planar dose measurements were done using a semiflex ion chamber and an electronic portal imaging device (EPID), respectively. The planned doses of all test cases met the criteria of the TG-119 protocol, except those for the spinal cord of the C-Shape hard case. There were no significant differences between the treatment planning doses and the doses given in the TG-119 report, with p-values ranging from 0.974 to 1 (p > 0.05). Doses to the target volumes were similar in the IMRT and VMAT plans, but the organs at risk (OARs) doses were different depending on the test case. The planning results showed that IMRT is more conformal than VMAT in certain cases. For the point dose measurements, the confidence limit (CLpoint) of 0.030 and 0.021 were better than the corresponding values of 0.045 and 0.047 given in the TG-119 report for high-dose and low-dose areas, respectively. Regarding the planar dose measurements, the CLplanar value of 0.38 obtained in this work was lower than that given in the TG-119 report (12.4). It is concluded that the dosimetry measurements performed in this study showed better confidence limits than those provided in the TG 119 report. IMRT remains more conformal in certain circumstances than the more progressive VMAT. When selecting the method of delivering a dose to the patient, several factors must be considered, including the radiotherapy technique, energy, treatment site, and tumour geometry. [ABSTRACT FROM AUTHOR]

Introduction: This study primarily aims to investigate the suitability of Halcyon in the context of cervical-thoracic esophageal cancer by exploring the dosimetric quality and delivery efficiency of Halcyon plans with different arc configurations. Additionally, it compares these findings with the dosimetric indices and delivery efficiency of TrueBeam and TomoTherapy accelerators, focusing on their capability to optimize protection for organs at risk (OARs) while maintaining efficient treatment delivery strategies. Methods: This retrospective study involved 26 patients diagnosed with cervical-thoracic esophageal cancer, and new radiotherapy plans were created using Halcyon, TrueBeam, and TomoTherapy. Dose volume histogram (DVH) metrics and delivery efficiency for plans involving different arc numbers on Halcyon (2, 3, and 4 arcs) were compared with those from TrueBeam and TomoTherapy. T-tests were employed to evaluate differences in organ protection among the accelerators. Results: The Halcyon plans, especially those with 4 arcs, provided superior protection for organs at risk, including the heart, lungs, and spinal cord, while maintaining excellent delivery efficiency. Compared to TrueBeam 2arc plans and TomoTherapy helical plans, Halcyon plans with 3 arcs also showed slight advantages. Although TomoTherapy offered better uniformity in dose distribution, it did not demonstrate a clear advantage over the other accelerators in terms of OAR protection or treatment efficiency. Furthermore, despite the lack of clear advantages in TrueBeam 2arc plans with flattening filter (FF), TrueBeam with flattening filter free (FFF) plans may hold potential in the treatment. Conclusion: Halcyon, particularly with 4 arcs, offers an optimal balance between reducing toxicity to organs at risk and maintaining treatment efficiency, making it a preferred choice in cervical thoracic esophageal cancer radiotherapy. The findings highlight the need for careful selection of radiotherapy accelerators based on specific clinical goals, with Halcyon showing potential advantages in scenarios where both treatment efficiency and OAR protection are paramount. [ABSTRACT FROM AUTHOR]

Background Purpose Methods Results Conclusions Dose calculation in radiotherapy aims to accurately estimate and assess the dose distribution of a treatment plan. Monte Carlo (MC) dose calculation is considered the gold standard owing to its ability to accurately simulate particle transport in inhomogeneous media. However, uncertainties such as the patient's dynamically deforming anatomy can still lead to differences between the delivered and planned dose distribution.Development and validation of a deformable voxel geometry for MC dose calculations (DefVoxMC) to account for dynamic deformation in the dose calculation process of photon‐ and electron‐based radiotherapy treatment plans for clinically motivated cases.DefVoxMC relies on the subdivision of a regular voxel geometry into dodecahedrons. It allows shifting the dodecahedrons’ corner points according to the deformation in the patient's anatomy using deformation vector fields (DVF). DefVoxMC is integrated into the Swiss Monte Carlo Plan (SMCP) to allow the MC dose calculation of photon‐ and electron‐based treatment plans on the deformable voxel geometry. DefVoxMC is validated in two steps. A compression test and a Fano test are performed in silico. Delta4 (for photon beams) and EBT4 film measurements in a cubic PMMA phantom (for electron beams) are performed on a TrueBeam in Developer Mode for clinically motivated treatment plans. During these measurements, table motion is used to mimic rigid dynamic patient motion. The measured and calculated dose distributions are compared using gamma passing rate (GPR) (3% / 2 mm (global), 10% threshold). DefVoxMC is used to study the impact of patient‐recorded breathing motion on the dose distribution for clinically motivated lung and breast cases, each prescribed 50 Gy to 50% of the target volume. A volumetric modulated arc therapy (VMAT) and an arc mixed‐beam radiotherapy (Arc‐MBRT) plan are created for the lung and breast case, respectively. For the dose calculation, the dynamic deformation of the patient's anatomy is described by DVFs obtained from deformable image registration of the different phases of 4DCTs. The resulting dose distributions are compared to the ones of the static situation using dose–volume histograms and dose differences.DefVoxMC is successfully integrated into the SMCP to enable the MC dose calculation of photon‐ and electron‐based treatments on a dynamically deforming patient anatomy. The compression and the Fano test agree within 1.0% and 0.1% with the expected result, respectively. Delta4 and EBT4 film measurements agree with the calculated dose by a GPR >95%. For the clinically motivated cases, breathing motion resulted in areas with a dose increase of up to 26.9 Gy (lung) and up to 7.6 Gy (breast) compared to the static situation. The largest dose differences are observed in high‐dose‐gradient regions perpendicular to the beam plane, consequently decreasing the planning target volume coverage (V95%) by 4.2% for the lung case and 2.0% for the breast case.A novel method for MC dose calculation for photon‐ and electron‐based treatments on dynamically deforming anatomy is successfully developed and validated. Applying DefVoxMC to clinically motivated cases, we found that breathing motion has non‐negligible impact on the dosimetric plan quality. [ABSTRACT FROM AUTHOR]

Background: Volumetric modulated arc therapy (VMAT) planning optimization involves iterative adjustment of numerous parameters, and hence requires repeatedly dose recalculation. In this study, we used the deep learning method to develop a fast and accurate dose calculation method for VMAT. Methods: The classical 3D UNet was adopted and trained to learn the physics principle of dose calculation. The inputs included the projected fluence map (FM), computed tomography (CT) images, the radiological depth and the source-to-voxel distance (SVD). The projected FM was generated by projecting the accumulated FM between two consecutive control points (CPs) onto the patient's anatomy. The accumulated FM was calculated by simulating the movement of the multi-leaf collimator (MLC) from one CP to the next. The dose, calculated by the treatment planning system (TPS), was used as ground truth. 51 head and neck VMAT plans were used, with 43, 1 and 7 cases as training, validation, and testing datasets, respectively. Correspondingly, 7182, 180 and 1260 CP samples were included in the training, validation, and testing datasets. Results: This presented method was evaluated by comparing the derived dose distribution to the TPS calculated dose distribution. The dose profiles coincided for both the single CP and the entire plan (summation of all CPs). But the network derived dose was smoother than the TPS calculated dose. Gamma analysis was performed between the network derived dose and the TPS calculated dose. The average gamma pass rate was 96.56%, 98.75%, 98.03% and 99.30% under the criteria of 2% (tolerance) -2 mm (distance to agreement, DTA). 2%-3 mm, 3%-2 mm and 3%-3 mm. No significant difference was observed on the critical indices including the max, mean dose, and the relative volume covered by the 2000 cGy, 4000 cGy and the prescription dose. For one CP, the average computational time of the network and TPS was 0.09s and 0.53s. And for one patient, the average time was 16.51s and 95.60s. Conclusion: The dose distribution derived by the network showed good agreement with the TPS calculated dose distribution. The computational time was reduced to approximate one-sixth of its original duration. Therefore the presented deep learning-based dose calculation method has the potential to be used for planning optimization. [ABSTRACT FROM AUTHOR]

Background: This study aimed to identify the efficacy of increasing the dose of stereotactic body radiotherapy (SBRT) for lung cancer. Method and Materials: Patients who received SBRT for primary lung cancer between 2002 and 2021 were evaluated retrospectively. The patients were categorized into the 48, 50, and 55 Gy groups according to the prescribed dose. Analyses were performed for all matched patients. Result: A total of 323 patients underwent SBRT for lung lesions at doses of 48, 50, and 55 Gy in four fractions. The median follow-up period in the 55 Gy group (32.3 months; Interquartile range (IQR), 15.1–54.1 months, P = 0.01) was significantly shorter than in the 48 Gy (47.0 months; IQR, 16,2–107.7 months) and 50 Gy (78.9 months; IQR 47.2–104.2 months) groups. The 3-year local progression-free survival (LPFS) was 90% in the 55 Gy group (95% confidence interval (CI), 62.4%–94.0%), 75.7% in the 48 Gy group (62.1%–85.0%), and 79.1% in the 50 Gy group (62.2%–89.1%). LPFS in the 55 Gy group was significantly higher than that in the 48 Gy group (hazard ratio (HR), 0.40; 95% CI, 0.20–0.79; P = 0.025). There is no significant difference in the local control rate between the 55 Gy group and the 50 Gy group (HR 0.60, CI 0.27–1.39). After propensity score matching, the 3-year LPFS in the 55 Gy group was 88.3% (CI, 71.2–95.5%). LPFS in the 55 Gy group did not significantly differ from that of the 48 Gy group (HR, 0.47; CI, 0.17–1.35) and the 50 Gy group (HR, 0.83; CI, 0.28–2.51). Conclusion: We conducted the analysis using propensity score matching. It was not apparent whether there was a significant difference in the effect of increasing the dose, owing to a lack of power caused by the small number of cases after propensity score matching. A prospective study is in progress, and the results are awaited. [ABSTRACT FROM AUTHOR]

To investigate how absorbed doses to mastication structures in modern radiotherapy (RT) technique for head and neck cancer (HNC) compared with earlier RT techniques and with published trismus tolerance doses. To compare the incidence of radiation-induced trismus by earlier and newer RT techniques. This study investigated two HNC patient cohorts treated with RT in 2007–2012 (three-dimensional conformal radiotherapy [3DCRT] and/or intensity-modulated radiotherapy [IMRT]; n =121 [ Cohort 1 ]) and 2017–2020 (volumetric-modulated arc therapy [VMAT]; n =124 [ Cohort 2 ]). All patients underwent RT without mastication structure–sparing intent, had normal mouth-opening ability before RT, and were prospectively assessed. Trismus was defined as the maximal interincisal opening ≤35 mm at any follow-up (3-, 6-, and 12-months post-RT). The temporomandibular joints (TMJs), masseter, and medial/lateral pterygoid muscles were delineated on the planning CT:s. Mean doses were compared between cohorts, and evaluated with respect to published trismus tolerance doses. P values ≤ 0.05 indicated statistical significance. Within 12 months post RT, 74/121 (61%) of patients in Cohort 1 had experienced trismus compared to 11/124 (9%) in Cohort 2. Averaged mean doses (±S.D.) for the masseter muscles were 35.2±8.3 Gy in Cohort 1 and 20.2±8.7 Gy in Cohort 2 (P <0.001). Corresponding numbers were 19.1±16.2 and 4.3±4.3 Gy for the TMJs, 53.7±10.1 and 40.2±16.8 Gy for the medial pterygoid muscles, and 29.2±18.7 and 9.2±8.4 Gy for the lateral pterygoid muscles (all P <0.001). Masseter muscle doses were below tolerance doses in 23% of patients in Cohort 1 compared with 90% in Cohort 2. The corresponding numbers were 52% and 96% for the TMJs, 8% and 36% for the medial pterygoid muscles and 72% and 100% for the lateral pterygoid muscles. Mastication structure mean doses by more recent RT techniques were generally below proposed tolerance doses, with dose reductions of 10–20 Gy compared with earlier techniques. Modern RT without mastication-structure-sparing intent resulted in below 10% of HNC patients experiencing trismus compared with 60% treated with earlier techniques. • Modern radiotherapy can substantially spare organs-at-risk in head and neck cancer. • Mastication-structure mean radiation doses were reduced by 10–20 Gy. • These dose reductions were accompanied by a trismus reduction from 60% to 10%. [ABSTRACT FROM AUTHOR]

To present the final results of a phase I trial on stereotactic radiosurgery (SRS) delivered using volumetric modulated arc therapy (VMAT) in patients with primary or metastatic tumors in different extracranial sites. The DESTROY-2 trial, planned as a prospective dose escalation study in oligometastatic (one to five lesions) cancer patients relied on the delivery of a single high dose of radiation utilizing high-precision technology. The primary study endpoint was the definition of the maximum tolerated dose (MTD) of SRS-VMAT. The secondary objectives of the study were the evaluation of safety, efficacy, and long-term outcomes. All patients consecutively observed at our radiotherapy unit matching the inclusion criteria were enrolled. Each enrolled subject was included in a different phase I study arm, depending on the tumor site and the disease stage (lung, liver, bone, other), and sequentially assigned to a particular dose level. Two hundred twenty seven lesions in 164 consecutive patients (male/female: 97/67, median age: 68 years; range: 29–92) were treated. The main primary tumors were: prostate cancer (60 patients), colorectal cancer (47 patients), and breast cancer (39 patients). The maximum planned dose level was achieved in all study arms, and the MTD was not exceeded. 34 Gy, 32 Gy, 24 Gy, and 24 Gy were established as the single-fraction doses for treating lung, liver, bone, and other extracranial lesions, respectively. The prescribed BED 2Gy α/β:10 to the planning target volume ranged from 26.4 Gy to 149.6 Gy. Twenty-seven patients (16.5%) experienced grade 1–2 and only one grade 3 acute toxicity, which was a pulmonary one. In terms of late toxicity, we registered only 5 toxicity>G2: a G3 gastro-intestinal one, three G3 bone toxicity, and a G3 laryngeal toxicity. The overall response was available for 199 lesions: 107 complete response (53.8%), 50 partial response (25.1%), and 31 stable disease (15.6%), leading to an overall response rate of 94.5%. Progression was registered only in 11 cases (5.5%). The overall response rate in each arm ranged from 88.6% to 96.4%. The overall two-year local control, distant metastasis free survival, disease free survival, and overall survival were 81.7%, 33.0%, 25.4%, and 78.7% respectively. In conclusion, the planned doses of 34 Gy, 32 Gy, 24 Gy, and 24 Gy were successfully administered as single-fractions for the treatment of lung, liver, bone, and other extracranial lesions, respectively, in a prospective SRS dose-escalation trial. No dose-limiting toxicities were registered, and minimal acute and late toxicity were reported. New indications for SRS are currently being studied in oligoprogressive patients receiving targeted drugs or in combination with immunotherapy. The DESTROY-2 trial represents, in our opinion, a credible starting point for future modern radiosurgery trials. • One of the few prospective SRS studies exploring MTD across different clinical settings. • 34 Gy, 32 Gy, and 24 Gy single fraction were safely delivered to lung, liver, bone. • The highest dose level was reached in all the settings, not exceeding the MTD. • The toxicity profile was low with one acute and five late toxicities >G2. • High LC rates and encouraging long-term outcomes were observed. [ABSTRACT FROM AUTHOR]

Previous plan competitions have largely focused on dose metric assessments. However, whether the submitted plans were realistic and reasonable from a quality assurance (QA) perspective remains unclear. This study aimed to investigate the relationship between aperture-based plan complexity metrics (PCM) in volumetric modulated arc therapy (VMAT) competition plans and clinical treatment plans verified through patient-specific QA (PSQA). In addition, the association of PCMs with plan quality was examined. A head and neck (HN) plan competition was held for Japanese institutions from June 2019 to July 2019, in which 210 competition plans were submitted. Dose distribution quality was quantified based on dose-volume histogram (DVH) metrics by calculating the dose distribution plan score (DDPS). Differences in PCMs between the two VMAT treatment plan groups (HN plan competitions held in Japan and clinically accepted HN VMAT plans through PSQA) were investigated. The mean (± standard deviation) DDPS for the 98 HN competition plans was 158.5 ± 20.6 (maximum DDPS: 200). DDPS showed a weak correlation with PCMs with a maximum r of 0.45 for monitor unit (MU) ; its correlation with some PCMs was "very weak." Significant differences were found in some PCMs between plans with the highest 20% DDPSs and the remaining plans. The clinical VMAT and competition plans revealed similar distributions for some PCMs. Deviations in PCMs for the two groups were comparable, indicating considerable variability among planners regarding planning skills. The plan complexity for HN VMAT competition plans increased for high-quality plans, as shown by the dose distribution. Direct comparison of PCMs between competition plans and clinically accepted plans showed that the submitted HN VMAT competition plans were realistic and reasonable from the QA perspective. This evaluation may provide a set of criteria for evaluating plan quality in plan competitions. [ABSTRACT FROM AUTHOR]

This study provides a concise and structured overview of a dosimetric comparison study conducted to assess the feasibility and effectiveness of 4 advanced radiotherapy techniques in treating brain metastases with hippocampus sparing and simultaneous integrated boost (HS-WBRT+SIB). Eleven patients with brain metastases previously treated with radiotherapy were included in the study. Planning CT scans with 2 mm slice thickness and MR imaging were used for contouring and dose prescription. The bilateral hippocampus and other organs at risk (OARs) were automatically contoured, and hippocampal avoidance regions (HAR) were defined as a 7 mm 3D expansion around the hippocampus. Gross tumor volume for each metastasis (GTV met) and planning target volume for metastases (PTV met) were delineated. The whole-brain CTV (CTV WB) and planning target volume for whole brain (PTV WB) were defined accordingly. Treatment planning and optimization were conducted using state-of-the-art radiotherapy techniques: Ethos, HyperArc, VMAT, and Tomotherapy. Tomotherapy achieved the highest D98% for PTV met , indicating the best metastasis coverage. HyperArc plans showed the highest D98% for PTV WB , suggesting superior whole-brain coverage. Tomotherapy demonstrated significantly lower D98%, D2%, and D mean values for the hippocampus, indicating its superiority in sparing the hippocampus. VMAT resulted in the lowest D2% values for the eyes, optic nerves, brainstem, and hypophysis, showing the best sparing of these critical structures. Tomotherapy consistently achieved lower D mean values for parotids, oral cavity, and lips compared to the other techniques. The dosimetric comparison revealed distinct strengths and weaknesses for each radiotherapy technique. Tomotherapy excelled in sparing the hippocampus, while VMAT showed promise in sparing OARs. HyperArc plans demonstrated the best overall whole-brain coverage. These findings should guide clinicians in selecting the most suitable technique based on patient characteristics and institutional resources. [ABSTRACT FROM AUTHOR]

Background: As radiotherapy techniques advance, so do planning methods for multi‐target intracranial SRS cases. Multi‐target‐single‐isocenter (MTSI) planning offers high‐precision beam delivery with shortened duration. However, accommodating all targets in a single Patient‐Specific‐Quality‐Assurance (PSQA) with QA devices like SRS MapCHECK (SRS MC) is generally impractical. Purpose: Consequently, we conducted PSQA, using a custom script, by relocating each Target or Neighboring‐Target‐Group (T‐NTG) relative to the beam isocenter on the PSQA device, ensuring each target's dose coverage at high precision. Methods: SRS treatment plans use 6MV–FFF beams, consisting of four Volumetric Modulated ARC Therapy (VMAT) arcs, including one full‐arc and three half arcs with couch‐kicks. A custom script calculated T‐NTG coordinates relative to the beam isocenter. QA verification plans were created for each T‐NTG, redefining the beam isocenter for precise alignment with the center of the SRS MC. CBCT images were acquired during PSQA for SRS MC alignment, and gamma‐index analysis (GIA) was performed. A single‐tail paired t‐test assessed the passing rate (PR) for 75 QA verification plans. Results: GIA with l.0 mm/2.0% criteria for each QA plan yielded a PR > 95.5%, with an average of 98.9%. Plans achieving PR > 99.0% and > 97.0% constituted 63% and 92% of studied plans, respectively. Statistical significance was observed in a t‐test with an ideal PR value of 100%, while insignificance was found with a PR value of 99%, suggesting that PSQA for individual targets consistently approaches 99% PR. In MTSI cases using 6MV‐FFF beams, targets within the lateral dose‐fall‐off region require careful verification for acceptability. Our clinical study on individual T‐NTG relocation demonstrates that the presented PSQA methods are generally acceptable, supported by a statistically insignificant PR against a 99% PR value. Conclusions: Presented statistical analysis results indicate that the proposed PSQA approach can serve as a reliable tool in clinical settings. [ABSTRACT FROM AUTHOR]

Introduction: This study aims to compare tangential volumetric modulated arc therapy with half beam volumetric modulated arc therapy in the treatment of cancer in the left and right breasts. Material and Methods: Twenty patients (10 with left and 10 with right breast cancer) were planned with Tangential Volumetric Modulated Arc Therapy (tVMAT) and Half Beam Volumetric Modulated Arc Therapy (HVMAT) techniques for prescribed dose of 42.56Gy over 16 fractions with 6MV photon. The tVMAT technique limit the radiation to non-target areas. Dosimetric evaluations were performed for planning target volume (PTV), ipsilateral lung, heart, and contralateral breast with analysis via Repeated Measures ANOVA with a significance level of 5%. Results: tVMAT achieved superior target coverage and dose homogeneity compared to HVMAT. For left breast cancer, HVMAT reduced ipsilateral lung doses but increased contralateral breast doses. Heart doses remained similar in both techniques. For right breast cancer, tVMAT provided higher target coverage and reduced doses across critical parameters. Conclusion: tVMAT demonstrates strong potential as an advanced radiotherapy technique for breast cancer, improving dose control to the ipsilateral lung and heart while minimizing dose spread to the contralateral side, making it a promising alternative to conventional VMAT for enhanced precision in breast cancer treatment. [ABSTRACT FROM AUTHOR]

Purpose: SRS MapCHECK (SMC) is a commercially available patient‐specific quality assurance (PSQA) tool for stereotactic radiosurgery (SRS) applications. This study investigates the effects of degree of modulation, location off‐axis, and low dose threshold (LDT) selection on gamma pass rates (GPRs) between SMC and treatment planning system, Analytical Anisotropic Algorithm (AAA), or Vancouver Island Monte Carlo (VMC++ algorithm) system calculated dose distributions. Methods: Volumetric‐modulated arc therapy (VMAT) plans with modulation factors (MFs) ranging from 2.7 to 10.2 MU/cGy were delivered to SMC at isocenter and 6 cm off‐axis. SMC measured dose distributions were compared against AAA and VMC++ via gamma analysis (3%/1 mm) with LDT of 10% to 80% using SNC Patient software. Results: Comparing on‐axis SMC dose against AAA and VMC++ with LDT of 10%, all AAA‐calculated plans met the acceptance criteria of GPR ≥ 90%, and only one VMC++ calculated plan was marginally outside the acceptance criteria with pass rate of 89.1%. Using LDT of 80% revealed decreasing GPR with increasing MF. For AAA, GPRs reduced from 100% at MF of 2.7 MU/cGy to 57% at MF of 10.2 MU/cGy, and for VMC++ calculated plans, the GPRs reduced from 89% to 60% in the same MF range. Comparison of SMC dose off‐axis against AAA and VMC++ showed more pronounced reduction of GPR with increasing MF. For LDT of 10%, AAA GPRs reduced from 100% to 83% in the MF range of 2.7 to 9.8 MU/cGy, and VMC++ GPR reduced from 100% to 91% in the same range. With 80% LDT, GPRs dropped from 100% to 42% for both algorithms. Conclusions: MF, dose calculation algorithm, and LDT selections are vital in VMAT‐based SRT PSQA. LDT of 80% enhances sensitivity of gamma analysis for detecting dose differences compared to 10% LDT. To achieve better agreement between calculated and SMC dose, it is recommended to limit the MF to 4.6 MU/cGy on‐axis and 3.6 MU/cGy off‐axis. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to find descriptors that correlates with normal brain dose to determine the feasibility of performing fractionated stereotactic radiosurgery (SRS) for multiple brain metastases (BMs) using five linac machines. Methods: Thirty‐two patients with 1–30 BMs were enrolled. Treatment plans were created using TrueBeam, Novalis Tx, TrueBeam Edge, Halcyon, and Tomotherapy linacs. The sum of all planning target volumes (PTVs) was defined as PTVall, and the brain region excluding PTVall was defined as normal brain. The total surface area (TSA) of the PTV was calculated from the sum of the surface areas of the equivalent spheres for each PTV. Volumes receiving more than 5, 12, and 18 Gy (V5Gy, V12Gy, and V18Gy, respectively) were used for evaluation of normal brain dose. Correlations between normal brain dose and each tumor characteristic (number, PTVall, and TSA) were investigated using the Spearman rank correlation coefficient. Results: Correlations between each characteristic and normal brain dose were statistically significant (p < 0.05) across all machines. The correlation coefficients between each characteristic and V18Gy for the five machines were as follows: tumor number, 0.39–0.60; PTVall, 0.79–0.93; TSA, 0.93–0.99. The fit equations between TSA and V18Gy exhibited high coefficients of determination, ranging from 0.92 to 0.99 across five machines. Conclusion: This study devised fractionated SRS plans using for 1–30 BMs across five linac machines to find descriptors for determining SRS feasibility based on normal brain dose. TSA proved to be a promising descriptor of SRS feasibility for treating multiple BMs. [ABSTRACT FROM AUTHOR]

Background This study investigates the impact of convergence mode (CM) in Eclipse (Varian Medical Systems) on the quality and complexity of volumetric modulated arc therapy (VMAT) plans for nasopharyngeal carcinoma (NPC) patients. Methods We retrospectively analyzed data from 21 NPC patients. For each patient, three VMAT plans with different CM settings (Off, On, and Extended) were created using identical optimization objectives. Plan quality was assessed using indices such as the conformity index (CI) and homogeneity index (HI), as well as evaluating target coverage and sparing of organs at risk (OARs). Complexity was measured by metrics including average leaf pair opening (ALPO), modulation complexity scores for VMAT (MCSv), monitor units (MUs), and optimization time. Dosimetric verification was performed based on the gamma pass rate. Results Different CM settings can generate treatment plans that meet clinical dose objectives for planning target volumes (PTVs) and OARs. The ‘On’ or ‘Extended’ CM settings improved CI and HI for the NPC target volume and reduced OAR doses, especially the mean dose, without compromising target coverage. The ‘Extended’ CM setting produced the most favorable outcomes. ALPO values for CM settings ‘Off’, ‘On’, and ‘Extended’ were 29.1 ± 4.3 mm, 28.6 ± 4.2 mm, and 28.4 ± 4. 2 mm, respectively. MCSv values for these settings were 0.1730 ± 0.0215, 0.1691 ± 0.0204, and 0.1693 ± 0.0208, respectively. MUs were 796.2 ± 110.8 for CM ‘Off’, 798.6 ± 106.1 for CM ‘On’, and 799.7 ± 103.6 for CM ‘Extended’, with no significant differences (p > 0.05). Gamma pass rates for all plans were above 99% (3%/3 and 2%/2 mm), with no significant differences among groups (p > 0.05). The average optimization times for CM settings ‘Off’, ‘On’, and ‘Extended’ were 14.4 ± 3.2, 35.9 ± 8.9, and 145.6 ± 50.3 min, respectively (p < 0.001). Conclusion CM usage can improve the CI and HI of the target volume and decrease the dose to OARs in VMAT plans for NPC patients. This study suggests that CM can be a valuable tool in VMAT planning for nasopharyngeal carcinoma, given adequate planning time.

Introduction: Treatment of pelvic bone metastases using a Halcyon machine, mostly presents some difficulties to plan, especially for big volumes because of the machine field size. The purpose of this study is to use two lateral isocenters in the treatment of pelvic bone metastases with the Halcyon machine, in order to overcome its limitations in treating large volumes.Material and Methods: We report a retrospective study of 8 patients who received radiotherapy for pelvic bone metastases, all treated by two different VMAT techniques. The first technique was performed by two longitudinal isocenters (LONI) and the second by two lateral isocenters (LATI) respecting the authorized distance longitudinally between two isocenters which must be less than 8 cm. For each isocenter, two opposite arcs are used for all treated patients.Results: The plans conformity index (CI) assessment shows no difference between the two used techniques for all the treated patients. Remarkable coverage of PTVs was obtained in lateral isocenter (LATI) with 96.2% compared to 94%.6% for LONI, as well as the maximum dose which was 109.4% for LATI versus 112.3% for LONI. However, the Conformation number (CN) that takes into account both healthy tissue and organ at risk protection was improved by 7.3% by using LATI.Conclusion: A very satisfactory result has been obtained in the treatment of pelvic bone metastases with LATI. With this technique, we can exceed the limits of the Halcyon machine and process larger volumes.

Introduction: The aim of this study is to find out the influence of different Segment shape optimization (SSO) parameters in radiotherapy Volumetric Modulated Arc therapy (VMAT) planning of Cervical Cancer and to find out the optimized value for cervical cancer patients.Material and Methods: It was a retrospective study of 20 Ca cervix patients. Every patient had six plans named SL1, SL5, SL10, SL15, SL20, and NSL. In each case, the value of the shaping loop will be changed during the VMAT plan, while the other optimization parameters and constraint functions will remain the same in each case. All Dosimetric parameters have been measured and analysed for Planning Target Volume (PTV) and Organ at risk (OAR) dose, Monitor Unit (MU), memory, Plan Delivery Time (PDT), and Gamma Passing Rate (GPR) for comparison purposes.Results: In NSL cases, the PTV dose derived from the DVH did not meet the clinical standards D95% = 86.8% ( 0.05) compared with the other groups. SL5 has the least plan memory compared to other SL values.Conclusion: Based on the plan quality, the dose accuracy, and the efficiency of delivery, SL1 and SL5 have similar characteristics in cervical cancer cases. Both SL1 and SL5 values should recommend for cervical cancer VMAT planning.

Background: Modern radiotherapy exemplified by intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), has transformed esophageal cancer treatment. Facing challenges in treating thoracic esophageal cancer near vital organs, this study introduces a regression model-based decision support tool for the optimal selection of radiotherapy techniques. Methods: We enrolled 106 patients diagnosed with locally advanced thoracic esophageal cancer in this study and designed individualized IMRT and VMAT radiotherapy plans for each patient. Detailed dosimetric analysis was performed to evaluate the differences in dose distribution between the two radiotherapy techniques across various thoracic regions. Single-factor and multifactorial logistic regression analyses were employed to establish predictive models (P1 and P2) and factors such as TLV/PTV ratio. These models were used to predict the compliance and potential advantages of IMRT and VMAT plans. External validation was performed in a validation group of 30 patients. Results: Using predictive models, we developed a data-driven decision support tool. For upper thoracic cases, VMAT plans were recommended; for middle/ lower thoracic cases, the tool guided VMAT/IMRT choices based on TLV/PTV ratio. Models P1 and P2 assessed IMRT and VMAT compliance. In validation, the tool showed high specificity (90.91%) and sensitivity (78.95%), differentiating IMRT and VMAT plans. Balanced performance in compliance assessment demonstrated tool reliability. Conclusion: In summary, our regression model-based decision support tool provides practical guidance for selecting optimal radiotherapy techniques for thoracic esophageal cancer patients. Despite a limited sample size, the tool demonstrates potential clinical benefits, alleviating manual planning burdens and ensuring precise, individualized treatment decisions for patients. [ABSTRACT FROM AUTHOR]

This retrospective study was performed to evaluate plan quality and treatment delivery parameters of stereotactic body radiation therapy (SBRT) for prostate cancer. The study utilized different isocentric modulated techniques: intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) using 6 MV flattening filter (FF) and 10 MV flattening filter-free beams (FFF). Fifteen retrospective prostate cancer patients were selected for this study. Sixty plans were created with an SBRT-prescribed dose of 36.25 Gy delivered in five fractions. Planning target volume (PTV) coverage, plan quality indices, doses delivered to organs at risk (OARs), and treatment delivery parameters were compared for all plans. It turned out that VMAT plans, particularly those using the FFF beam, provided superior target conformality and a steeper dose gradient as compared to IMRT plans. Additionally, VMAT plans showed better OARs sparing compared to IMRT plans. However, IMRT plans delivered a lower maximum dose to the target than VMAT plans. Importantly, the VMAT plans resulted in reduced treatment delivery parameters, including beam on time (BOT), monitor unit (MU), and modulation factor (MF), compared to IMRT plans. Furthermore, a statistically significant difference was observed in BOT and mean body dose between FF and FFF beams, with FFF beams showing superior performance. Considering all results, VMAT using 10 MV (FFF) is suggested for treating prostate cancer patients with SBRT. This offers the fastest delivery in addition to maintaining the highest plan quality. [ABSTRACT FROM AUTHOR]

Introduction: The aim of this study is to find out the influence of different Segment shape optimization (SSO) parameters in radiotherapy Volumetric Modulated Arc therapy (VMAT) planning of Cervical Cancer and to find out the optimized value for cervical cancer patients. Material and Methods: It was a retrospective study of 20 Ca cervix patients. Every patient had six plans named SL1, SL5, SL10, SL15, SL20, and NSL. In each case, the value of the shaping loop will be changed during the VMAT plan, while the other optimization parameters and constraint functions will remain the same in each case. All Dosimetric parameters have been measured and analysed for Planning Target Volume (PTV) and Organ at risk (OAR) dose, Monitor Unit (MU), memory, Plan Delivery Time (PDT), and Gamma Passing Rate (GPR) for comparison purposes. Results: In NSL cases, the PTV dose derived from the DVH did not meet the clinical standards D95% = 86.8% (<95%) with a poorer homogeneity index (HI = 0.2). As the SL value increases, plan quality increases, monitor units increase slightly and plan delivery time decreases while there is a parallel increase in memory consumption. There is no statistical difference in target dose and OAR dose between the SL5 and SL1 plans (P > 0.05) compared with the other groups. SL5 has the least plan memory compared to other SL values. Conclusion: Based on the plan quality, the dose accuracy, and the efficiency of delivery, SL1 and SL5 have similar characteristics in cervical cancer cases. Both SL1 and SL5 values should recommend for cervical cancer VMAT planning. [ABSTRACT FROM AUTHOR]

Introduction: Treatment of pelvic bone metastases using a Halcyon machine, mostly presents some difficulties to plan, especially for big volumes because of the machine field size. The purpose of this study is to use two lateral isocenters in the treatment of pelvic bone metastases with the Halcyon machine, in order to overcome its limitations in treating large volumes. Material and Methods: We report a retrospective study of 8 patients who received radiotherapy for pelvic bone metastases, all treated by two different VMAT techniques. The first technique was performed by two longitudinal isocenters (LONI) and the second by two lateral isocenters (LATI) respecting the authorized distance longitudinally between two isocenters which must be less than 8 cm. For each isocenter, two opposite arcs are used for all treated patients. Results: The plans conformity index (CI) assessment shows no difference between the two used techniques for all the treated patients. Remarkable coverage of PTVs was obtained in lateral isocenter (LATI) with 96.2% compared to 94%.6% for LONI, as well as the maximum dose which was 109.4% for LATI versus 112.3% for LONI. However, the Conformation number (CN) that takes into account both healthy tissue and organ at risk protection was improved by 7.3% by using LATI. Conclusion: A very satisfactory result has been obtained in the treatment of pelvic bone metastases with LATI. With this technique, we can exceed the limits of the Halcyon machine and process larger volumes. [ABSTRACT FROM AUTHOR]

Background: Chemoradiation in head and neck carcinoma (HNC) shows significant anatomical resulting in erroneous dose deposition in the target or the organ at risk (OAR). Adaptive radiotherapy (ART) can overcome this. Timing of significant target and OAR changes with dosimetric impact; thus, most suitable time and frequency of ART is unclear. Methods: This dosimetric study used prospective weekly non‐contrast CT scans in 12 HNC patients (78 scans). OARs and TVs were manually contoured after registration with simulation scan. Dose overlay done on each scan without reoptimization. Dosimetric and volumetric variations assessed. Results: Commonest site was oropharynx. Gross Tumor Volume (GTV) reduced from 47.5 ± 19.2 to 17.8 ± 10.7 cc. Nodal GTV reduced from 15.7 ± 18.8 to 4.7 ± 7.1 cc. Parotid showed mean volume loss of 35%. T stage moderately correlated with GTV regression. Conclusion: Maximum GTV changes occurred after 3 weeks. Best time to do single fixed interval ART would be by the end of 3 weeks. [ABSTRACT FROM AUTHOR]

Background: For patient‐specific quality assurance (PSQA) for small targets, the dose resolution can change depending on the characteristics of the dose calculation algorithms. Purpose: This study aimed to evaluate the influence of the dose calculation algorithms Acuros XB (AXB), anisotropic analytical algorithm (AAA), photon Monte Carlo (pMC), and collapsed cone (CC) on a helical diode array using volumetric‐modulated arc therapy (VMAT) for small targets. Materials and methods: ArcCHECK detectors were inserted with a physical depth of 2.9 cm from the surface. To evaluate the influence of the dose calculation algorithms for small targets, rectangular fields of 2×100, 5×100, 10×100, 20×100, 50×100, and 100×100 mm2 were irradiated and measured using ArcCHECK with TrueBeam STx. A total of 20 VMAT plans for small targets, including the clinical sites of 19 brain metastases and one spine, were also evaluated. The gamma passing rates (GPRs) were evaluated for the rectangular fields and the 20 VMAT plans using AXB, AAA, pMC, and CC. Results: For rectangular fields of 2×100 and 5×100 mm2, the GPR at 3%/2 mm of AXB was < 50% because AXB resulted in a coarser dose resolution with narrow beams. For field sizes > 10×100 mm2, the GPR at 3%/2 mm was > 88.1% and comparable for all dose calculation algorithms. For the 20 VMAT plans, the GPRs at 3%/2 mm were 79.1 ± 15.7%, 93.2 ± 5.8%, 94.9 ± 4.1%, and 94.5 ± 4.1% for AXB, AAA, pMC, and CC, respectively. Conclusion: The behavior of the dose distribution on the helical diode array differed depending on the dose calculation algorithm for small targets. Measurements using ArcCHECK for VMAT with small targets can have lower GPRs owing to the coarse dose resolution of AXB around the detector area. [ABSTRACT FROM AUTHOR]