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Background Purpose Methods Results Conclusions The field of artificial intelligence (AI)‐based patient‐specific quality assurance (PSQA) for volumetric modulated arc therapy (VMAT) faces challenges in terms of developing general models across institutions due to the prevalence of multi‐institution data collection and multivariate heterogeneity. Building a general model that is capable of handling diverse multi‐institution data is critical for enabling large‐scale integration and analysis.This study aims to develop a star generative adversarial network (StarGAN) and transformer‐based hybrid classification‐regression PSQA framework to address unification of heterogeneous data from different institutions.A StarGAN and transformer‐based hybrid classification‐regression model was developed as a general PSQA framework to predict gamma passing rates (GPRs) and classify quality assurance (QA) results as “Pass” or “Fail” at multiple institutions. A total of 1815 VMAT plans were collected from eight institutions to develop the general PSQA framework and perform clinical commissioning and implementation. Among them, 20 independent clinical plans from each of eight institutions, for a total of 160 plans, were used for the clinical commissioning, and 205 new clinical plans from eight institutions were used for clinical implementation.For the 3%/3, 3%/2, and 2%/2 mm gamma criteria, the sensitivity of the proposed PSQA framework with pretraining was 90.13%, 92.03%, and 95.84%, respectively, while the specificity was 76.01%, 76.12%, and 85.34%, respectively. The mean absolute errors (MAEs) of the proposed PSQA framework with pretraining were 1.36%, 2.37%, and 3.96%, respectively, while the root‐mean‐square errors (RMSEs) were 2.31%, 3.89%, and 5.17%, respectively. The results demonstrated visible improvement at multiple institutions. For clinical commissioning, the deviations between the predicted and measured results were all within 3% for 3%/3 and 3%/2 mm at eight institutions. For clinical implementation, all failure plans were correctly identified by the proposed PSQA framework.The general PSQA framework enables diverse clinical data sources to be handled to achieve enhanced model performance and generalizability, and provides a solution to the unification of heterogeneous data from different institutions to construct robust QA models. This approach can be clinically deployed for VMAT QA. [ABSTRACT FROM AUTHOR]

This article from BJU International presents a case study of a 74-year-old patient with castration-resistant prostate cancer who underwent stereotactic body radiotherapy (SBRT) for 20 metastatic lesions. The patient had a complex treatment history involving various therapies before receiving SBRT, which served as a bridge therapy while awaiting 177Lu-PSMA-617 therapy. The SBRT treatment was delivered without reported side effects, resulting in a decrease in PSA levels and a partial or complete response at treated sites. The article discusses the efficacy and challenges of SBRT in treating multiple metastatic sites, highlighting the evolving landscape of prostate cancer therapy. [Extracted from the article]

Background Purpose Methods Results Conclusions Non‐coplanarity and mixed beam modality could be combined to further enhance dosimetric treatment plan quality. We introduce dynamic mixed beam arc therapy (DYMBARC) as an innovative technique that combines non‐coplanar photon and electron arcs, dynamic gantry and collimator rotations, and intensity modulation with photon multileaf collimator (MLC). However, finding favorable beam directions for DYMBARC is challenging due to the large solution space, machine component constraints, and optimization parameters, posing a highly non‐convex optimization problem.To establish DYMBARC and solve the pathfinding challenge by employing direct aperture optimization (DAO) to determine the table angles and gantry angle ranges of photon and electron arcs for different clinically motivated cases.The method starts by generating a grid of beam directions based on user‐defined resolutions along the gantry and table angle axes for each beam quality considered. Beam directions causing collisions or entering through the end of CT are excluded. For electrons, a fixed source‐to‐surface distance of 80 cm is used to reduce in‐air scatter. Electron beam energies with insufficient range to reach the target or beam directions impinging on the table before reaching the patient are excluded. The remaining beam directions form the pathfinding solution space. Promising photon and electron MLC‐defined apertures, with associated monitor unit (MU) weights, are iteratively added using a hybrid‐DAO algorithm. This algorithm combines column generation to add apertures and simulated annealing to further refine aperture shapes and weights. Apertures are added until the requested number of paths are formed and the user‐defined maximum total gantry angle range is reached. Paths are resampled to a finer gantry angle resolution and subject to DAO for simultaneous optimization of beam intensities along the photon/electron arcs. Subsequent final dose calculation and MU weight reoptimization result in a deliverable DYMBARC plan. DYMBARC plans are created for three clinically motivated cases (brain, breast, and pelvis) and compared to DYMBARC variants: colli‐DTRT (dynamic collimator trajectory radiotherapy) using non‐coplanar photon arcs; and Arc‐MBRT (mixed beam radiotherapy) using photons and electrons but restricted to coplanar setup. Additionally, a manually defined volumetric modulated arc therapy (VMAT) setup serves as a reference clinical technique. Dose distributions, dose‐volume histograms, and dosimetric endpoints are evaluated. Dosimetric validation with radiochromic film measurements (gamma evaluation, 3% / 2 mm (global), 10% dose threshold) is performed on a TrueBeam system in developer mode for one case.While maintaining similar target coverage and homogeneity, DYMBARC reduced mean doses to organs‐at‐risk compared to VMAT by an average of 3.2, 0.5, and 2.9 Gy for the brain, breast, and pelvis cases, respectively. Similar or smaller mean dose reductions were observed for Arc‐MBRT or colli‐DTRT, compared to VMAT. Electron contributions to the mean planning target volume dose ranged from 2% to 34% for DYMBARC and from 11% to 40% for Arc‐MBRT. Measurement validation showed >99.7% gamma passing rate.DYMBARC was successfully established using a dosimetrically optimized pathfinding approach, combining non‐coplanarity with mixed beam modality. DYMBARC facilitated the determination of photon and electron contributions on a case‐by‐case basis, enhancing more personalized treatment modalities. [ABSTRACT FROM AUTHOR]

Background Methods Results Conclusions Hippo‐avoidance prophylactic cranial irradiation (HA‐PCI) requires a hippocampal avoidance zone expanded from hippocampus to ensure dose fall‐off and compensate for setup errors. Most studies recommend a 5‐mm margin, while it could be optimized to a 2‐mm expansion. Here, we showed the details of optimized HA‐PCI for limited‐stage small cell lung cancer (LS‐SCLC).This cohort study reviewed patients with LS‐SCLC receiving optimized HA‐PCI from August 2014 to June 2020 in the National Cancer Center of China. The hippo‐related dose parameters were summarized. The comparison of the Hopkins Verbal Learning Test—Revised (HVLT‐R) scores in different time points was conducted. The Kaplan–Meier method was used to calculate the survival rates.A total of 112 patients were included. The average doses of hippocampus and hippocampal avoidance zone were 6.80 Gy (IQR: 6.40–7.44) and 7.63 Gy (IQR: 7.14–8.39). No differences were observed in the two radiation techniques (tomotherapy [TOMO] vs. volumetric‐modulated arc therapy [VMAT]). The decline of HVLT‐R score remained in a low level and not significant in assessable patients (p = 0.095). With a median follow‐up of 52 months (95% CI: 47.2–56.7), the 2‐year overall survival and progression‐free survival were 74.1% and 50.0%, respectively. Two intracranial recurrence lesions (2.3%) located <2 mm from the hippocampus.Optimized HA‐PCI could achieve similar dose limitation by TOMO and VMAT techniques with favorable efficacy and minor toxicity. [ABSTRACT FROM AUTHOR]

To evaluate the dosimetric benefits and clinical feasibility of deep inspiratory breath-hold (DIBH) combined with volumetric modulated arc therapy (VMAT) in left-sided postmastectomy radiotherapy (PMRT). Eligible patients with left-sided breast cancer undergoing DIBH-based PMRT were prospectively included. Chest wall, supra/infraclavicular fossa, and/or internal mammary node irradiation (IMNI) were planned with a prescription dose of 43.5 Gy in 15 fractions. VMAT plans were designed on free breathing (FB)—and DIBH-CT to compare dosimetric parameters in heart, left anterior descending artery (LAD) and lung. Cone-beam computed tomography (CBCT) was performed before and after treatment to evaluate inter- and intra-fractional setup errors. Heart position and dose variations during treatment were estimated by fusing CBCT with DIBH-CT scans.Twenty patients were included with 10 receiving IMNI. In total, 193 pre-treatment and 39 pairs pre- and post-treatment CBCT scans were analyzed. The Dmean, Dmax, and V5−40 of the heart, LAD, and left lung were significantly lower in DIBH than FB (p < 0.05 for all), except for V5 of LAD (p = 0.167). The cardiopulmonary dosimetric benefits were maintained regardless of IMNI. The inter- and intra-fractional setup errors were < 0.3 cm; and the overall estimated PTV margins were < 1.0 cm. During treatment, the mean dice similarity coefficient of heart position and the mean ratio of heart Dmean between CBCT and DIBH-CT plans was 0.95 (0.88–1.00) and 100% (70.6–119.5%), respectively. DIBH-VMAT could effectively reduce the cardiopulmonary doses with acceptable reproducibility and stability in left-sided PMRT regardless of IMNI. [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]

Purpose: This paper discusses an advanced version of our audiovisual-assisted therapeutic ambience in radiotherapy (AVATAR) radiolucent display systems designed for pediatric radiotherapy, enabling anesthesia-free treatments, video communication, and biofeedback. The scope of the AVATAR system is expanded here in two major ways: (i) through alternative mounting systems to accommodate a broader range of radiotherapy machines (specifically to fit robotic-arm and toroidal geometry photon radiotherapy and proton radiotherapy systems) and (ii) through additional hardware to provide videocalling, optimized audio for clear communication, and combined video inputs for biofeedback, translation, and other advanced functionalities. Methods and materials: Because robustness requires strong parts and radiotransparency requires thin, light parts, three-dimensional printing was used to rapidly prototype hollow structures and to iteratively improve robustness. Two system designs were made: one that mounts superior and another that mounts inferior to the patient's head. Radiation dose measurements and calculations were conducted to assess dose perturbations at surface and depth due to the screen. Results: For 6-MV volumetric modulated arc therapy (VMAT) plans, with and without the screen, the mean and maximum dose differences inside the planning target volume were 0.2% and 2.6% of the 200 cGy prescription, respectively. For a single static beam through the screen, the maximum measured excess surface dose was 13.4 ± 0.5%, and the largest measured dose attenuation at 5-cm waterequivalent depth was 2.1 ± 0.2%. These percentages are relative to the dose without the screen at those locations. Conclusions: The radiolucent screen systems provided here are shown to give minimal dosimetric effects on megavoltage VMAT photon treatments. For static beams, however, surface dose effects should be considered when these beams pass through the thickest components of the screen. Design files are also provided. [ABSTRACT FROM AUTHOR]

Thoracic bulky esophageal cancer shrinks during radiotherapy, changing the location and shape of the surrounding heart and lungs. The current study aimed to explore how replanning by volumetric-modulated arc radiotherapy (VMAT) and three-dimensional conformal radiotherapy (3DCRT) influences the target coverage and dose to organs at risk in locally advanced unresectable middle to lower thoracic esophageal cancer. We retrospectively collected CT simulation images of initial and boost radiotherapy plans for locally advanced unresectable thoracic esophageal cancer in 17 consecutive patients. First, we created boost plans of 20 Gy using 3DCRT and VMAT on the initially acquired CT images. Second, we replicated the process on CT images acquired after 20–40 Gy of radiotherapy. We then compared non-replanned boost radiotherapy plans with replanned boost plans. Replanned radiotherapy delivered more conformal doses to the target and reduced heart and lung doses. VMAT reduced more irradiated mean doses to the heart than 3DCRT in the case of replanning (1.7 and 1.1 Gy, p < 0.001). Replanning to accommodate tumor shrinkage during radiotherapy effectively lowers the irradiated doses to the heart and lungs in patients with locally advanced unresectable middle to lower thoracic esophageal cancer, especially those treated with VMAT. [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]

The advancement of precision radiotherapy techniques, such as volumetric modulated arc therapy (VMAT), stereotactic body radiotherapy (SBRT), and particle therapy, highlights the importance of radiotherapy in the treatment of cancer, while also posing challenges for respiratory motion management in thoracic and abdominal tumors. MRI-guided radiotherapy (MRIgRT) stands out as state-of-art real-time respiratory motion management approach owing to the non-ionizing radiation nature and superior soft-tissue contrast characteristic of MR imaging. In clinical practice, MR imaging often operates at a frequency of 4 Hz, resulting in approximately a 300 ms system latency of MRIgRT. This system latency decreases the accuracy of respiratory motion management in MRIgRT. Artificial intelligence (AI)-based respiratory motion prediction has recently emerged as a promising solution to address the system latency issues in MRIgRT, particularly for advanced contour prediction and volumetric prediction. However, implementing AI-based respiratory motion prediction faces several challenges including the collection of training datasets, the selection of prediction methods, and the formulation of complex contour and volumetric prediction problems. This review presents modeling approaches of AI-based respiratory motion prediction in MRIgRT, and provides recommendations for achieving consistent and generalizable results in this field. [ABSTRACT FROM AUTHOR]

At the first interim analysis of the phase 3 ENGOT-cx11/GOG-3047/KEYNOTE-A18 study, the addition of pembrolizumab to chemoradiotherapy provided a statistically significant and clinically meaningful improvement in progression-free survival in patients with locally advanced cervical cancer. We report the overall survival results from the second interim analysis of this study. Eligible patients with newly diagnosed, high-risk (FIGO 2014 stage IB2–IIB with node-positive disease or stage III–IVA regardless of nodal status), locally advanced, histologically confirmed, squamous cell carcinoma, adenocarcinoma, or adenosquamous cervical cancer were randomly assigned 1:1 to receive five cycles of pembrolizumab (200 mg) or placebo every 3 weeks with concurrent chemoradiotherapy, followed by 15 cycles of pembrolizumab (400 mg) or placebo every 6 weeks. Pembrolizumab or placebo and cisplatin were administered intravenously. Patients were stratified at randomisation by planned external beam radiotherapy type (intensity-modulated radiotherapy [IMRT] or volumetric-modulated arc therapy [VMAT] vs non-IMRT or non-VMAT), cervical cancer stage at screening (FIGO 2014 stage IB2–IIB node positive vs III–IVA), and planned total radiotherapy (external beam radiotherapy plus brachytherapy) dose (<70 Gy vs ≥70 Gy [equivalent dose of 2 Gy]). Primary endpoints were progression-free survival per RECIST 1.1 by investigator or by histopathological confirmation of suspected disease progression and overall survival defined as the time from randomisation to death due to any cause. Safety was a secondary endpoint. Between June 9, 2020, and Dec 15, 2022, 1060 patients at 176 sites in 30 countries across Asia, Australia, Europe, North America, and South America were randomly assigned to treatment, with 529 patients in the pembrolizumab–chemoradiotherapy group and 531 patients in the placebo–chemoradiotherapy group. At the protocol-specified second interim analysis (data cutoff Jan 8, 2024), median follow-up was 29·9 months (IQR 23·3–34·3). Median overall survival was not reached in either group; 36-month overall survival was 82·6% (95% CI 78·4–86·1) in the pembrolizumab–chemoradiotherapy group and 74·8% (70·1–78·8) in the placebo–chemoradiotherapy group. The hazard ratio for death was 0·67 (95% CI 0·50–0·90; p=0·0040), meeting the protocol-specified primary objective. 413 (78%) of 528 patients in the pembrolizumab–chemoradiotherapy group and 371 (70%) of 530 in the placebo–chemoradiotherapy group had a grade 3 or higher adverse event, with anaemia, white blood cell count decreased, and neutrophil count decreased being the most common adverse events. Potentially immune-mediated adverse events occurred in 206 (39%) of 528 patients in the pembrolizumab–chemoradiotherapy group and 90 (17%) of 530 patients in the placebo–chemoradiotherapy group. This study is registered with ClinicalTrials.gov , NCT04221945. Pembrolizumab plus chemoradiotherapy significantly improved overall survival in patients with locally advanced cervical cancer These data, together with results from the first interim analysis, support this immuno-chemoradiotherapy strategy as a new standard of care for this population. Merck Sharp & Dohme, a subsidiary of Merck & Co. [ABSTRACT FROM AUTHOR]

Introduction: Radiotherapy plays a key role in the multidisciplinary management of oesophageal cancers across neoadjuvant, definitive and palliative settings. Improved precision in radiotherapy planning and delivery techniques have allowed treating disease with tighter margins reducing toxicity. In this study, we examine the appropriateness of current practice in defining the planning target volume (PTV). Methods: This is a single institutional retrospective study of patients who received radiotherapy for oesophageal cancers using volumetric modulated arc therapy (VMAT) during 2020. All cone‐beam computerised tomography (CBCT) scans were reviewed to assess whether PTV expansions appropriately accounted for tumour motion and interfractional variation. Results: Of the 27 patients, 2 (7%), 5 (19%) and 20 (74%) had cervical, thoracic and distal/gastro‐oesophageal junction (GOJ) disease, respectively. 16 (59%) had adenocarcinoma and 9 (33%) had squamous cell carcinoma. 9 of 20 distal/GOJ patients were planned and treated according to the institutional stomach filling protocol. 521/528 (98.7%) CBCTs demonstrated adequate target coverage. Cervical, thoracic and GOJ regions demonstrated adequate target coverage in 57/58, 96/97 and 368/373 CBCTs with median PTV expansions of 5, 7 and 7 mm, respectively. In four patients with GOJ disease, CBCT review identified five episodes where the target volume was insufficiently covered during the treatment course. Conclusion: In this single institutional retrospective study, for the vast majority of patients, our institutional practice of defining PTV margins achieved satisfactory target treatment. The interfractional variations observed in patients with GOJ tumours due to target motion and variable gastric volume, highlights the role of further refinements to motion management techniques in this cohort. [ABSTRACT FROM AUTHOR]

The article from the Journal of Medical Imaging & Radiation Oncology discusses the use of low-dose VMAT radiotherapy for treating actinic keratosis, a condition that can affect large areas of the skin. The study conducted at Sir Charles Gairdner Hospital in Perth, Australia, analyzed patients treated for actinic keratosis and found that VMAT radiotherapy resulted in a complete response in 100% of treated areas, with favorable patient-reported outcomes. The study demonstrated excellent short-term response with lower doses than previously published data, highlighting the potential of this treatment for actinic keratosis. [Extracted from the article]

Background: The current level of automation in the production of radiotherapy plans for lung cancer patients is relatively low. With the development of artificial intelligence, it has become a reality to use neural networks to predict dose distributions and provide assistance for radiation therapy planning. However, due to the significant individual variability in the distribution of non‐small cell lung cancer (NSCLC) planning target volume (PTV) and the complex spatial relationships between the PTV and organs at risk (OARs), there is still a lack of a high‐precision dose prediction network tailored to the characteristics of NSCLC. Purpose: To assist in the development of volumetric modulated arc therapy (VMAT) plans for non‐small cell lung cancer patients, a deep neural network is proposed to predict high‐precision dose distribution. Methods: This study has developed a network called MHA‐ResUNet, which combines a large‐kernel dilated convolution module and multi‐head attention (MHA) modules. The network was trained based on 80 VMAT plans of NSCLC patients. CT images, PTV, and OARs were fed into the independent input channel. The dose distribution was taken as the output to train the model. The performance of this network was compared with that of several commonly used networks, and the networks' performance was evaluated based on the voxel‐level mean absolute error (MAE) within the PTV and OARs, as well as the error in clinical dose‐volume metrics. Results: The MAE between the predicted dose distribution and the manually planned dose distribution within the PTV is 1.43 Gy, and the D95 error is less than 1 Gy. Compared with the other three commonly used networks, the dose error of the MHA‐ResUNet is the smallest in PTV and OARs. Conclusions: The proposed MHA‐ResUNet network improves the receptive field and filters the shallow features to learn the relative spatial relation between the PTV and the OARs, enabling accurate prediction of dose distributions in NSCLC patients undergoing VMAT radiotherapy. [ABSTRACT FROM AUTHOR]

Background: Intensity modulation with dynamic multi‐leaf collimator (MLC) and monitor unit (MU) changes across control points (CPs) characterizes volumetric modulated arc therapy (VMAT). The increased uncertainty in plan deliverability required patient‐specific quality assurance (PSQA), which remained inefficient upon Quality Assurance (QA) failure. To prevent waste before QA, plan complexity metrics (PCMs) and machine learning models with the metrics were generated, which were lack of providing CP‐specific information upon QA failures. Purpose: By generating 3D images from digital imaging and comminications in medicine in radiation therapy (DICOM RT) plan, we proposed a predictive model that can estimate the deliverability of VMAT plans and visualize CP‐specific regions associated with plan deliverability. Methods: The patient cohort consisted of 259 and 190 cases for left‐ and right‐breast VMAT treatments, which were split into 235 and 166 cases for training and 24 cases from each treatment for testing the networks. Three‐channel 3D images generated from DICOM RT plans were fed into a DenseNet‐based deep learning network. To reflect VMAT plan complexity as an image, the first two channels described MLC and MU variations between two consecutive CPs, while the last channel assigned the beam field size. The network output was defined as binary classified PSQA results, indicating deliverability. The predictive performance was assessed by accuracy, sensitivity, specificity, F1‐score, and area under the curve (AUC). The gradient‐weighted class activation map (Grad‐CAM) highlighted the regions of CPs in VMAT plans associated with deliverability, compared against PCMs by Spearman correlation. Results: The DenseNet‐based predictive model yielded AUCs of 92.2% and 93.8%, F1‐scores of 97.0% and 93.8% and accuracies of 95.8% and 91.7% for the left‐ and right‐breast VMAT cases. Additionally, the specificity of 87.5% for both cases indicated that the predictive model accurately detected QA failing cases. The activation maps significantly differentiated QA failing‐labeled from passing‐labeled classes for the non‐deliverable cases. The PCM with the highest correlation to the Grad‐CAM varied from patient cases, implying that plan deliverability would be considered patient‐specific. Conclusion: This work demonstrated that the deep learning‐based network based on visualization of dynamic VMAT plan information successfully predicted plan deliverability, which also provided control‐point specific planning parameter information associated with plan deliverability in a patient‐specific manner. [ABSTRACT FROM AUTHOR]

External beam radiotherapy incorporates treatment techniques such as three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), image-guided radiotherapy and volumetric modulated arc therapy to deliver high-energy radiation to cancer. The use of IMRT for cancer treatment is also associated with significant costs for patients in low--middle-income countries. The purpose of this study was to compare the dosimetric properties of 3DCRT and IMRT treatment plans for the external beam irradiation of patients with prostate cancer (Pca) to ascertain the superiority of IMRT in terms of dose homogeneity, conformity and dose limitation to organs at risk (OAR) in a resource-limited setting. One hundred and sixty treatment plans for 80 patients were created using 3DCRT and IMRT on the Eclipse treatment planning system (version 13.6). Data were collected and assessed from the dose-volume histogram of each plan. The conformity and homogeneity index (HI) for each of the plans were calculated. The doses to the OAR were also recorded and evaluated. The mean HIs for the IMRT and 3DCRT treatment techniques were 0.04 ± 0.02 (range: 0.01-0.011) and 0.09 ± 0.02 (range: 0.04-0.016), respectively. The mean conformity index (CI) for IMRT and 3DCRT techniques were 1.257 ± 0.112 (range: 0.99-1.58) and 1.302 ± 0.196 (range: 1.10-2.26). IMRT had a better significant mean HI and CI compared to 3DCRT. Generally, for this study, IMRT had better organ sparing compared to 3DCRT. The mean doses for the OARs ranged from 4.3-74.6 Gy for IMRT and 3.1-75.9 Gy for the 3DCRT technique. Overall, this study demonstrates that IMRT may offer an enhanced therapeutic profile, potentially reducing toxicity to the patient and ensuring more precise dose delivery to the target volume compared to 3DCRT in PCa external beam irradiation. [ABSTRACT FROM AUTHOR]

Background: Craniospinal irradiation (CSI) poses a challenging planning process because of the complex target volume. Traditional 3D conformal CSI does not spare any critical organs, resulting in toxicity in patients. Here the dosimetric advantages of volumetricmodulated arc therapy (VMAT) using partial arc and avoidance sectors are compared with each other in planning in adult patients undergoing CSI to develop a clinically feasible technique that is both effective and efficient. Patient and methods: Eight adult patients treated with CSI were retrospectively identified. In total 16 plans were made. We generated two plans for each patient: 1. VMAT plan using partial arc, namely VMAT&lowbar;pa. 2. VMAT plan using avoidance sectors, namely VMAT&lowbar;as. The dose prescribed was 36 Gy in 20 fractions. The dose-volume histogram for planning target volume (PTV) and organs at risk (OAR) (lens, eye, heart, thyroid, lungs, liver, gonads and kidneys) were analysed and compared. Dose parameters of mean dose, V95%, and V107% for the PTV were evaluated. Results: The median length of PTV is 65.58 cm (45.8-79.5). The volume of PTV receiving 95% of the dose (V95%) in both the plans are 97.51% (VMAT&lowbar;as) and 97.99% (VMAT&lowbar;pa) (p = 0.121) while V107% are 0.733 and 0.742 for VMAT&lowbar;as and VMAT&lowbar;pa, respectively (p = 0.969). The doses of OARs such as lens, eye, liver and gonads were comparable. The mean heart dose was 10.4 and 9.0 Gy in VMAT&lowbar;as and VMAT&lowbar;pa plans, respectively (p = 0.005). Significant lower doses to the thyroid, kidneys and lungs were seen in VMAT plans using avoidance sectors. Conclusion: This study provides a practically useful VMAT planning method for the treatment of CSI and illustrates the ability of VMAT using avoidance sectors to generate highly conformal and homogeneous treatment plans for CSI, while limiting the dose to the relevant OARs. [ABSTRACT FROM AUTHOR]

Our purpose was to provide an understanding of current functional lung imaging (FLI) techniques and their potential to improve dosimetry and outcomes for patients with lung cancer receiving radiation therapy (RT). Excerpta Medica dataBASE (EMBASE), PubMed, and Cochrane Library were searched from 1990 until April 2023. Articles were included if they reported on FLI in one of: techniques, incorporation into RT planning for lung cancer, or quantification of RT-related outcomes for patients with lung cancer. Studies involving all RT modalities, including stereotactic body RT and particle therapy, were included. Meta-analyses were conducted to investigate differences in dose-function parameters between anatomic and functional RT planning techniques, as well as to investigate correlations of dose-function parameters with grade 2+ radiation pneumonitis (RP). One hundred seventy-eight studies were included in the narrative synthesis. We report on FLI modalities, dose-response quantification, functional lung (FL) definitions, FL avoidance techniques, and correlations between FL irradiation and toxicity. Meta-analysis results show that FL avoidance planning gives statistically significant absolute reductions of 3.22% to the fraction of well-ventilated lung receiving 20 Gy or more, 3.52% to the fraction of well-perfused lung receiving 20 Gy or more, 1.3 Gy to the mean dose to the well-ventilated lung, and 2.41 Gy to the mean dose to the well-perfused lung. Increases in the threshold value for defining FL are associated with decreases in functional parameters. For intensity modulated RT and volumetric modulated arc therapy, avoidance planning results in a 13% rate of grade 2+ RP, which is reduced compared with results from conventional planning cohorts. A trend of increased predictive ability for grade 2+ RP was seen in models using FL information but was not statistically significant. FLI shows promise as a method to spare FL during thoracic RT, but interventional trials related to FL avoidance planning are sparse. Such trials are critical to understanding the effect of FL avoidance planning on toxicity reduction and patient outcomes. [ABSTRACT FROM AUTHOR]

Purpose: To determine if patient‐specific IMRT quality assurance can be measured on any matched treatment delivery system (TDS) for patient treatment delivery on another. Methods: Three VMAT plans of varying complexity were created for each available energy for head and neck, SBRT lung, and right chestwall anatomical sites. Each plan was delivered on three matched Varian TrueBeam TDSs to the same Scandidos Delta4 Phantom+ diode array with only energy‐specific device calibrations. Dose distributions were corrected for TDS output and then compared to TPS calculations using gamma analysis. Round‐robin comparisons between measurements from each TDS were also performed using point‐by‐point dose difference, median dose difference, and the percent of point dose differences within 2% of the mean metrics. Results: All plans had more than 95% of points passing a gamma analysis using 3%/3 mm criteria with global normalization and a 20% threshold when comparing measurements to calculations. The tightest gamma analysis criteria where a plan still passed > 95% were similar across delivery systems—within 0.5%/0.5 mm for all but three plan/energy combinations. Median dose deviations in measurement‐to‐measurement comparisons were within 0.7% and 1.0% for global and local normalization, respectively. More than 90% of the point differences were within 2%. Conclusion: A set of plans spanning available energies and complexity levels were delivered by three matched TDSs. Comparisons to calculations and between measurements showed dose distributions delivered by each TDS using the same DICOM RT‐plan file meet tolerances much smaller than typical clinical IMRT QA criteria. This demonstrates each TDS is modeled to a similar accuracy by a common class (shared) beam model. Additionally, it demonstrates that dose distributions from one TDS show small differences in median dose to the others. This is an important validation component of the common beam model approach, allowing for operational improvements in the clinic. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study is to determine the effect of forcing and filling the electron density (ED) to 1.0 of the planning target volume (PTV) overdose distribution in lung SBRT treatment leading to shortening patient treatment time and increasing patient comfort by reducing MU/fraction due to ED manipulation effect. Methods: In this study, 36 lung SBRT plans of 12 suitable patients who prescribed a total dose of 50 Gy in five fractions were generated with Monaco v.5.10 TPS using the Monte Carlo (MC) algorithm and volumetric modulated arc therapy (VMAT) technique by PTV ED values forcing as well as filling to 1.0 and comparatively assessed. The first group of plans was created by using the patient's original ED, second and third groups of plans were reoptimized by forcing and filling the ED of PTV to 1.0, respectively, therefore acquiring a new dose distribution which lead to comparatively assessment the effects of changes in ED on PTV and OAR doses. Results: Assessment of treatment plans revealed that mean MU/fx numbers were decreased by 76% and 75.25% between Groups 1 and 2, Groups 1 and 3, respectively. The number of segments was also reduced in Group 1 by up to 15% compared with Groups 2 and 3. Maximum HI and CI differences for PTV between Groups 1 and 2 were less than 1% and Groups 1 and 3 were 1.5% which indicates all 3 group plans were comparable in terms of dose distribution within PTV. Conclusions: Forcing and filling the ED of PTV to 1.0 strategy has provided reduced a number of segments and MU/fx without a significant change in PTV mean and maximum doses, thereby decreasing treatment time and patient discomfort during treatment. This process should be considered in line of a potential number of patients as well as prescribed dose and MU/fx numbers. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to introduce modified fixed field volumetric modulated arc therapy (MF‐VMAT) which manually opened the field size by fixing the jaws and comparing it to the typical planning technique, auto field volumetric modulated arc therapy (AF‐VMAT) in cervical cancer treatment planning. Methods and materials: Previously treated twenty‐eight cervical cancer plans were retrospectively randomly selected and replanned in this study using two different planning techniques: AF‐VMAT and MF‐VMAT, resulting in a total of fifty‐six treatment plans. In this study, we compared both planning techniques in three parts: (1) Organ at Risk (OARs) and whole‐body dose, (2) Treatment plan efficiency, and (3) Treatment plan accuracy. Results: For OARs dose, bowel bag (p‐value = 0.001), rectum (p‐value = 0.002), and left femoral head (p‐value = 0.001) and whole‐body (p‐value = 0.000) received a statistically significant dose reduction when using the MF‐VMAT plan. Regarding plan efficiency, MF‐VMAT exhibited a statistically significant increase in both number of monitor units (MUs) and control points (p‐values = 0.000), while beam‐on time, maximum leaf travel, average maximum leaf travel, and maximum leaf travel per gantry rotation were statistically significant decreased (p‐values = 0.000). In terms of plan accuracy, the average gamma passing rate was higher in the MF‐VMAT plan for both absolute dose (AD) (p‐value = 0.001, 0.004) and relative dose (RD) (p‐value = 0.000, 0.000) for 3%/3 and 3%/2 mm gamma criteria, respectively. Conclusion: The MF‐VMAT planning technique significantly reduces OAR doses and decreases the spread of low doses to normal tissues in cervical cancer patients. Additionally, this planning approach demonstrates efficient plans with lower beam‐on time and reduced maximum leaf travel. Furthermore, it indicates higher plan accuracy through an increase in the average gamma passing rate compared to the AF‐VMAT plan. Consequently, MF‐VMAT offers an effective treatment planning technique for cervical cancer patients. [ABSTRACT FROM AUTHOR]

Purpose: A single treatment planning system (TPS) model for matched linacs provides flexible clinical workflows from patient treatment to intensity‐modulated radiation therapy (IMRT) quality assurance (QA) measurement. Since general guidelines for building a single TPS model and its validation for matched linacs are not well established, we present our RayStation photon TPS modeling strategy for matched Elekta VersaHD linacs. Method: The four linacs installed from 2013 to 2020 were matched in terms of Percent Depth Dose (PDD), profile, output factor and wedge factors for 6‐MV, 10‐MV, 15‐MV, and 6‐MV‐FFF, and maintained following TG‐142 recommendations until RayStation commissioning. The RayStation single model was built to represent all four linacs within the tolerance limits recommended by MPPG‐5.a. The comprehensive validation tests were performed for one linac following MPPG‐5.a and TG‐119 guidelines, and spot checks for the other three. Our TPS modeling/validation method was evaluated by re‐analyzing the previous 103 patient‐specific IMRT/volumetric modulated arc therapy (VMAT) QA measurements with the calculated planar doses by the single model in comparison with the analysis results using four individual Pinnacle TPS models. Results: For all energies, our single model PDDs were within 1% agreement of the four‐linac commissioning measurements. The MPPG‐5.a validation tests from 5.1 through 7.5 and all TG‐119 measurements passed within the recommended tolerance limits. The IMRT QA results (mean ± standard deviation) for RayStation single model versus Pinnacle individual models were 98.9% ± 1.3% and 98.0% ± 1.4% for 6‐MV, 99.9% ± 0.1% and 99.1% ± 1.9% for 10‐MV, and 98.2% ± 1.3% and 97.9% ± 1.8% for 6‐MV‐FFF, respectively. Conclusion: We successfully built and validated a single photon beam model in RayStation for four Elekta Linacs. The proposed new validation methods were proven to be both efficient and effective. [ABSTRACT FROM AUTHOR]

Objective: This study aims to analyze setup errors in pelvic Volumetric Modulated Arc Therapy (VMAT) for patients with non‐surgical primary cervical cancer, utilizing the onboard iterative kV cone beam CT (iCBCT) imaging system on the Varian Halcyon 2.0 ring gantry structure accelerator to enhance radiotherapy precision. Method: We selected 132 cervical cancer patients who underwent VMAT with daily iCBCT imaging guidance. Before each treatment session, a registration method based on the bony structure was employed to acquire iCBCT images with the corresponding planning CT images. Following verification and adjustment of image registration results along the three axes (but not rotational), setup errors in the lateral (X‐axis), longitudinal (Y‐axis), and vertical (Z‐axis) directions were recorded for each patient. Subsequently, we analyzed 3642 iCBCT image setup errors. Results: The mean setup errors for the X, Y, and Z axes were 4.50 ± 3.79 mm, 6.08 ± 6.30 mm, and 1.48 ± 2.23 mm, respectively. Before correction with iCBCT, setup margins based on the Van Herk formula for the X, Y, and Z axes were 6.28, 12.52, and 3.26 mm, respectively. In individuals aged 60 years and older, setup errors in the X and Y axes were significantly larger than those in the younger group (p < 0.05). Additionally, there is no significant linear correlation between setup errors and treatment fraction numbers. Conclusion: Data analysis underscores the importance of precise Y‐axis setup for cervical cancer patients undergoing VMAT. Radiotherapy centers without daily iCBCT should appropriately extend the planning target volume (PTV) along the Y‐axis for cervical cancer patients receiving pelvic VMAT. Elderly patients exhibit significantly larger setup errors compared to younger counterparts. In conclusion, iCBCT‐guided radiotherapy is recommended for cervical cancer patients undergoing VMAT to improve setup precision. [ABSTRACT FROM AUTHOR]

Purpose: Recent papers suggested a correlation between the risk of distant metastasis (DM) and dose outside the PTV, though conclusions in different publications conflicted. This study resolves these conflicts and provides a compelling explanation of prognostic factors. Materials and methods: A dataset of 478 NSCLC patients treated with SBRT (IMRT or VMAT) was analyzed. We developed a deep learning model for DM prediction and explainable AI was used to identify the most significant prognostic factors. Subsequently, the prognostic power of the extracted features and clinical details were analyzed using conventional statistical methods. Results: Treatment technique, tumor features, and dosiomic features in a 3 cm wide ring around the PTV (PTV3cm) were identified as the strongest predictors of DM. The Hazard Ratio (HR) for Dmean,PTV3cm was significantly above 1 (p < 0.001). There was no significance of the PTV3cm dose after treatment technique stratification. However, the dose in PTV3cm was found to be a highly significant DM predictor (HR > 1, p = 0.004) when analyzing only VMAT patients with small and spherical tumors (i.e., sphericity > 0.5). Conclusions: The main reason for conflicting conclusions in previous papers was inconsistent datasets and insufficient consideration of confounding variables. No causal correlation between the risk of DM and dose outside the PTV was found. However, the mean dose to PTV3cm can be a significant predictor of DM in small spherical targets treated with VMAT, which might clinically imply considering larger PTV margins for smaller, more spherical tumors (e.g., if IGTV > 2 cm, then margin ≤ 7 mm, else margin > 7 mm). [ABSTRACT FROM AUTHOR]

Introduction: Volumetric modulated arc therapy (VMAT) total body irradiation (TBI) allows for greater organ sparing with improved target coverage compared to 2D-TBI. However, there is limited evidence of whether improved organ sparing translates to decreases in toxicities and how its toxicities compare to those of the 2D technique. We aimed to compare differences in toxicities among patients treated with TBI utilizing VMAT and 2D techniques. Methods/materials: A matched-pair single-institution retrospective analysis of 200 patients treated with TBI from 2014 to 2023 was performed. Overall survival (OS) and progression-free survival (PFS) were analyzed using the Kaplan-Meier method and compared using log-rank tests. Differences in characteristics and toxicities between the VMAT and 2D cohorts were compared using Fisher's exact test. Results: Of the 200 patients analyzed, 100 underwent VMAT-TBI, and 100 underwent 2D-TBI. The median age for VMAT-TBI and 2D-TBI patients was 13.7 years and 16.2 years, respectively (p = 0.25). In each cohort, 53 patients were treated with myeloablative regimens (8-13.76 Gy), and 47 were treated with nonmyeloablative regimens (2-4 Gy). For the entire VMAT-TBI cohort, lung Dmean, kidney Dmean, and lens Dmax were spared to 60.6% ± 5.0%, 71.0% ± 8.5%, and 90.1% ± 3.5% of prescription, respectively. For the non-myeloablative VMAT-TBI cohort, testis/ovary Dmax, brain, and thyroid Dmean were spared to 33.4% ± 7.3%, 75.4% ± 7.0%, and 76.1% ± 10.5%, respectively. For 2D-TBI, lungs were spared using partial-transmission lung blocks for myeloablative regimens. The VMAT-TBI cohort experienced significantly lower rates of any grade of pneumonitis (2% vs. 12%), nephrotoxicity (7% vs. 34%), nausea (68% vs. 81%), skin (16% vs. 35%), and graft versus host disease (GVHD) (42% vs. 62%) compared to 2D-TBI patients. For myeloablative regimen patients, rates of pneumonitis (0% vs. 17%) and nephrotoxicity (9% vs. 36%) were significantly lower with VMAT-TBI versus 2D-TBI (p < 0.01). Median follow-up was 14.3 months, and neither median OS nor PFS for the entire cohort was reached. In the VMAT versus 2D-TBI cohort, the 1-year OS was 86.0% versus 83.0% (p = 0.26), and the 1-year PFS was 86.6% and 80.0% (p = 0.36), respectively. Conclusion: Normal tissue sparing with VMAT-TBI compared to the 2D-TBI translated to significantly lower rates of pneumonitis, renal toxicity, nausea, skin toxicity, and GVHD in patients, while maintaining excellent disease control. [ABSTRACT FROM AUTHOR]

Purpose: The 3D U-Net deep neural network structure is widely employed for dose prediction in radiotherapy. However, the attention to the network depth and its impact on the accuracy and robustness of dose prediction remains inadequate. Methods: 92 cervical cancer patients who underwent Volumetric Modulated Arc Therapy (VMAT) are geometrically augmented to investigate the effects of network depth on dose prediction by training and testing three different 3D UNet structures with depths of 3, 4, and 5. Results: For planning target volume (PTV), the differences between predicted and true values of D98, D99, and Homogeneity were statistically 1.00 ± 0.23, 0.32 ± 0.72, and -0.02 ± 0.02 for the model with a depth of 5, respectively. Compared to the other two models, these parameters were also better. For most of the organs at risk, the mean and maximum differences between the predicted values and the true values for the model with a depth of 5 were better than for the other two models. Conclusions: The results reveal that the network model with a depth of 5 exhibits superior performance, albeit at the expense of the longest training time and maximum computational memory in the three models. A small server with two NVIDIA GeForce RTX 3090 GPUs with 24 G of memory was employed for this training. For the 3D U-Net model with a depth of more than 5 cannot be supported due to insufficient training memory, the 3D U-Net neural network with a depth of 5 is the commonly used and optimal choice for small servers. [ABSTRACT FROM AUTHOR]

Background: This research aims to evaluate the usability of the HyperArc (HA) technique in stereotactic radiosurgery for cervical spine metastasis by comparing the dosimetry of the target and organs at risk, specifically the spinal cord, between HA and VMAT and conventional volumetric modulated arc therapy (VMAT). Methods: A RANDO® phantom and QFix EncompassTM and support system were used to simulate three target types (A, B, and C) based on RTOG0631 guidelines. Treatment plans included one VMAT and two HyperArc techniques with different SRS NTO values (100 and 250). Dosimetric parameters such as conformity index (CI), homogeneity index (HI), R50, and spinal cord sparing were analyzed. Gamma analysis was performed using portal dosimetry to validate the dose delivery accuracy. Results: HyperArc plans demonstrated higher conformity, sharper dose fall-off, and improved quality assurance (QA) results compared to VMAT plans. HA with SRS NTO 250 showed even better results in terms of conformity, dose fall-off, and spinal cord dose reduction (V10 and Dmax) compared to HA with SRS NTO 100. Although the mean gamma passing rates were slightly lower, all plans achieved rates above 95%. Conclusion: The findings suggest that HA provides superior dosimetric benefits over VMAT and could be effectively utilized for cervical spine radiation therapy. [ABSTRACT FROM AUTHOR]

Background and purpose: Radiotherapy is a primary therapeutic approach for breast cancer following breast-conserving surgery. The TaiChiB dual-modality radiotherapy system combining X-ray and focused γ-ray, offers a new approach to reduce the radiation dose of organs at risk (OARs) and has the potential to mitigate the adverse effects of radiotherapy. Currently, there are few studies on the dosimetric characteristics of the TaiChiB dual-modality system for actual treatment plans for specific diseases. The purpose of this work is to study the dosimetric advantages of dual-modal systems for right breast patients after breast-conserving surgery. Material and methods: Treatment plans for 20 patients with right breast cancer were generated for a linear accelerator (LINAC) based system and the TaiChiB dual-modality system, respectively. Volumetric modulated arc therapy plans with simultaneous integrated boost (VMAT-SIB) were made for the LINAC. Focused g-ray was used to deliver the boost dose with the dual-modality system. The dosimetric parameters of the target and OARs were evaluated and compared between the treatment plans generated for the two systems. Results: The TaiChiB dual-modality plans exhibit a higher conformal index (CI) and lower gradient index (GI) for the PGTV and PTV compared with the LINACbased VMAT-SIB plans. Compared to VMAT-SIB plans, the PTV Dmax, PTV Dmean, PTV V110, PGTV Dmax, and PGTV Dmean of the TaiChiB dualmodality plans are significantly lower. Meanwhile, the dose to OARs, such as the Dmean of the heart, the V5 of liver, the Dmean of ipsilateral lung, the V30 of ipsilateral lung, the V20 of ipsilateral lung, the V5 of ipsilateral lung, the Dmean of contralateral lung, Dmax of contralateral breast and the Dmean of contralateral breast are significantly reduced. Conclusions: Our study demonstrates the dosimetric advantages of the novel TaiChiB dual-modality radiotherapy system for the treatment of right-sided breast cancer. Overall, for the TaiChiB dual-modality radiotherapy system, the radiation dose outside the target region decreases rapidly, thereby minimizing radiation exposure to neighboring organs and ensuring the conformity of the target area. Our research confirms the potential of the TaiChiB dual-modality system for future radiotherapy. [ABSTRACT FROM AUTHOR]

This document is a letter to the editor discussing the topic of trismus, or difficulty opening the mouth, in patients with head and neck tumors who have undergone radiotherapy. The letter highlights the use of advanced radiotherapy techniques, such as Intensity Modulated Radiotherapy Technology (IMRT) and Volumetric Modulated Arc Therapy (VMAT), in the treatment of head and neck cancers. The study conducted a prospective cohort study on 14 patients receiving IMRT/VMAT and found a correlation between radiation doses to the masticatory muscles and temporomandibular joint and the development of trismus. The study also reported declines in nutritional status and quality of life post-treatment. Further research is being conducted to investigate additional risk factors for trismus. [Extracted from the article]

Purpose: Hippocampal-avoidance whole-brain radiotherapy (HA-WBRT) planning can present challenges. This study examines the influence of head tilt angles on the dosimetric characteristics of target and organs at risk (OARs), aiming to identify the optimal tilt angle that yields optimal dosimetric outcomes using tomotherapy (TOMO). Methods: Eight patients diagnosed with brain metastases underwent CT scans at five tilt angles: [0°, 10°), [10°, 20°), [20°, 30°), [30°, 40°), and [40°, 45°]. Treatment plans were generated using TOMO and volumetric modulated arc therapy (VMAT). Dosimetric parameters including conformity index (CI), homogeneity index (HI), D2cc, D98%, and Dmean of PTV, as well as Dmax, and Dmean of OARs were analyzed. Furthermore, a comparison was made between the dosimetric parameters of TOMO and VMAT plans. Finally, delivery efficiency of TOMO plans were assessed. Results: For the PTV, [40°, 45°] tilt angle demonstrated significantly better conformity, homogeneity, lower D2cc, and lower Dmean for the PTV. Regarding the OARs, the [40°, 45°] head tilt angle demonstrated significantly lower Dmax and Dmean in hippocampus, eyes, optic chiasm, and optic nerves. The [40°, 45°] tilt angle also showed significantly lower Dmax for brainstem and cochleas, as well as a lower Dmean for lens. In the [40°,45°] tilt angle for HA-WBRT, TOMO showed superior performance over VMAT for the PTV. TOMO achieved lower Dmax for brainstem, cochleas, optic nerves, and optic chiasm, as well as a lower Dmean for hippocampus. Furthermore, a significant correlation was found between delivery time and the PTV projection length in the sagittal plane. Conclusion: The TOMO plan utilizing a tilt angle range of [40°, 45°] demonstrated superior PTV conformity and uniformity, along with enhanced OARs sparing. Furthermore, it exhibited a dosimetric advantage over VMAT for PTV and most OARs at the same angle range. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) are the main radiotherapy techniques for treating and managing rectal cancer. Collimator rotation is one of the crucial parameters in radiotherapy planning, and its alteration can cause dosimetric variations. This study assessed the effect of collimator rotation on the dosimetric results of various IMRT and VMAT plans for rectal cancer. MATERIALS AND METHODS: Computed tomography (CT) images of 20 male patients with rectal cancer were utilized for IMRT and VMAT treatment planning with various collimator angles. Nine different IMRT techniques (5, 7, and 9 coplanar fields with collimator angles of 0°, 45°, and 90°) and six different VMAT techniques (1 and 2 full coplanar arcs with collimator angles of 0°, 45°, and 90°) were planned for each patient. The dosimetric results of various treatment techniques for target tissue (conformity index [CI] and homogeneity index [HI]) and organs at risk (OARs) sparing (parameters obtained from OARs dose–volume histograms [DVH]) as well as radiobiological findings were analyzed and compared. RESULTS: The 7-fields IMRT technique demonstrated lower bladder doses (V40Gy, V45Gy), unaffected by collimator rotation. The 9-fields IMRT and 2-arcs VMAT (excluding the 90-degree collimator) had the lowest V35Gy and V45Gy. A 90-degree collimator rotation in 2-arcs VMAT significantly increased small bowel and bladder V45Gy, femoral head doses, and HI values. Radiobiologically, the 90-degree rotation had adverse effects on small bowel NTCP (normal tissue complication probability). No superiority was found for a 45-degree collimator rotation over 0 or 30 degrees in VMAT techniques. CONCLUSION: Collimator rotation had minimal impact on dosimetric parameters in IMRT planning but is significant in VMAT techniques. A 90-degree rotation in VMAT, particularly in a 2-full arc technique, adversely affects PTV homogeneity index, bladder dose, and small bowel NTCP. Other evaluated collimator angles did not significantly affect VMAT dosimetrical or radiobiological outcomes. [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]

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

Spatially fractionated radiotherapy (SFRT) techniques have undergone transformative evolution, encompassing physical GRID therapy, MLC-based grids, virtual TOMO GRIDs, and 3-dimensional high-dose lattices. Historical roots trace back to Alban Köhler's pioneering Spatially fractionated grid therapy (SFGRT), utilizing physical grids for dose modulation. Technological innovations introduced multi-leaf collimators (MLCs), enabling adaptable spatial fractionation and a shift to the broader term "SFRT." Physics and dosimetry-based studies have demonstrated the feasibility of computerized treatment planning and identified the potential to minimize the peripheral dose while using such high-dose therapy. Meanwhile, 3-dimensional high-dose lattices showed enhanced precision. The meticulous placement of high-dose volumetric spheres enables a reduction in the volume of high-dose spills. Advancements in 3-dimensional lattices through intensity-modulated radiotherapy and volumetric modulated arc therapy (VMAT) techniques offer enhanced therapeutic options. A database of SFRT studies identified 723 articles. This review shows the trajectory of SFRT from traditional grids to MLC-based approaches, virtual TOMO GRIDs, and innovative 3-dimensional lattices. Technological innovations, dosimetric advancements, and clinical feasibility have underscored the continual progress in refining spatially fractionated radiotherapy. The integration of MLCs and lattice techniques has demonstrated improved therapeutic outcomes, solidifying their relevance in modern radiation therapy protocols. Research has yet to reveal a clear correlation between treatment outcomes and dosimetric parameters. Additional investigations are necessary to assess the impact of various dosimetric parameters, such as EUD, peak-to-valley ratio (PVDR), D5%, D10%, D20%, D90%, etc., on the effectiveness of treatments. [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]

Kilovoltage computed tomography plays a crucial role in radiotherapy planning. However, the presence of high-density metallic objects can introduce streaking artifacts in CT scans, resulting in inaccurate dose calculations by the treatment planning software. Previous studies have explored manual density overrides and artifact reduction algorithms individually to enhance dose calculation accuracy, but their combined application on patient plans within a treatment planning system remains unexplored. This research aims to assess the necessity of manual density overrides when an artifact reduction algorithm is already employed to address dental artifacts in oropharyngeal cancer treatment plans. A total of 20 previously treated volumetric modulated arc therapy plans were collected, and manual density overrides were removed followed by plan recalculation. Dosimetric parameters were then compared between the original and modified plans. Statistical analysis revealed several dosimetric parameters for the planning target volume (PTV), clinical target volume (CTV), and oral cavity that exhibited statistically significant differences upon removing the manual density override. However, these differences were found to be small in absolute terms. No other organs evaluated demonstrated statistically significant differences in dose. The most significant disparity observed was an 8.26 cGy increase in mean dose to the CTV, which represents only 0.12% of the prescription dose. Based on these findings, it can be concluded that manual density overrides are likely unnecessary when an artifact reduction algorithm is employed in oropharyngeal cancer cases. [ABSTRACT FROM AUTHOR]

Synchronous bilateral breast cancers (SBBC) present a considerable issue in external beam radiotherapy because of large fields size and large target volumes. Mono-isocentric volumetric modulated arc therapy (VMAT) appears as an appropriate irradiation technique for these types of tumors. The aim of this study was to demonstrate the utility of a 3D DVH pretreatment quality assurance program in VMAT of SBBC cases. Twenty SBBC patients who underwent radiation therapy in our department were retrospectively enrolled in this study. Fifteen patients were treated exclusively to the mammary glands. Five patients benefited from a dose boost on the tumor bed (60Gy). Nine patients were irradiated on the supraclavicular nodes (50Gy). This dose was delivered in 25 fractions and integrated boost was used when appropriate. Depending on the complexity of the treatment plans; 2 or 4 arcs VMAT plans were used in a mono-isocentric technique. The patient specific quality assurance (PSQA) was evaluated using COMPASS measured data, COMPASS reconstructed (CR) and COMPASS computed (CC) dose compared to treatment planning system (TPS) dose. Clinical evaluation was based on DVH metrics for target volumes and organ at risks. The maximum average dose deviation between TPS, CC, and CR was below 3%. The paired t-test between TPS, CC, and CR shows a strong agreement (p < 0.001). The 3DVH dose distribution comparison between TPS and COMPASS were also performed with good gamma score for global analysis. COMPASS was successfully evaluated as a 3DVH pretreatment system for SBBC despite the large fields size and complex target volumes. It allows the verification of the plan in 3D patient anatomy and the evaluation of dose discrepancies. [ABSTRACT FROM AUTHOR]

Purpose: To assess the practicality of employing a commercial knowledge‐based planning tool (RapidPlan) to generate adapted intact prostate and prostate bed volumetric modulated arc therapy (VMAT) plans on iterative cone‐beam computed tomography (iCBCT) datasets. Methods and materials: Intact prostate and prostate bed RapidPlan models were trained utilizing planning data from 50 and 44 clinical cases, respectively. To ensure that refined models were capable of producing adequate clinical plans with a single optimization, models were tested with 50 clinical planning CT datasets by comparing dose‐volume histogram (DVH) and plan quality metric (PQM) values between clinical and RapidPlan‐generated plans. The RapidPlan tool was then used to retrospectively generate adapted VMAT plans on daily iCBCT images for 20 intact prostate and 15 prostate bed cases. As before, DVH and PQM metrics were utilized to dosimetrically compare scheduled (iCBCT Verify) and adapted (iCBCT RapidPlan) plans. Timing data was collected to further evaluate the feasibility of integrating this approach within an online adaptive radiotherapy workflow. Results: Model testing results confirmed the models were capable of producing VMAT plans within a single optimization that were overall improved upon or dosimetrically comparable to original clinical plans. Direct application of RapidPlan on iCBCT datasets produced satisfactory intact prostate and prostate bed plans with generally improved target volume coverage/conformality and rectal sparing relative to iCBCT Verify plans as indicated by DVH values, though bladder metrics were marginally increased on average. Average PQM values for iCBCT RapidPlans were significantly improved compared to iCBCT Verify plans. The average time required [in mm:ss] to generate adapted plans was 06:09 ± 02:06 (intact) and 07:12 ± 01:04 (bed). Conclusion: This study demonstrated the feasibility of leveraging RapidPlan to expeditiously generate adapted VMAT intact prostate and prostate bed plans on iCBCT datasets. In general, adapted plans were dosimetrically improved relative to scheduled plans, emphasizing the practicality of the proposed approach. [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: The positional accuracy of MLC is an important element in establishing the exact dosimetry in VMAT. We comprehensively analyzed factors that may affect MLC positional accuracy in VMAT, and constructed a model to predict MLC positional deviation and estimate planning delivery quality according to the VMAT plans before delivery. Methods: A total of 744 "dynalog" files for 23 VMAT plans were extracted randomly from treatment database. Multi‐correlation was used to analyzed the potential influences on MLC positional accuracy, including the spatial characteristics and temporal variability of VMAT fluence, and the mechanical wear parameters of MLC. We developed a model to forecast the accuracy of MLC moving position utilizing the random forest (RF) ensemble learning method. Spearman correlation was used to further investigate the associations between MLC positional deviation and dosage deviations as well as gamma passing rates. Results: The MLC positional deviation and effective impact factors show a strong multi‐correlation (R = 0.701, p‐value < 0.05). This leads to the development of a highly accurate prediction model with average variables explained of 95.03% and average MSE of 0.059 in the 5‐fold cross‐validation, and MSE of 0.074 for the test data was obtained. The absolute dose deviations caused by MLC positional deviation ranging from 12.948 to 210.235 cGy, while the relative volume deviation remained small at 0.470%–5.161%. The average MLC positional deviation correlated substantially with gamma passing rates (with correlation coefficient of −0.506 to −0.720 and p‐value < 0.05) but marginally with dosage deviations (with correlation coefficient < 0.498 and p‐value > 0.05). Conclusions: The RF predictive model provides a prior tool for VMAT quality assurance. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the beam complexity of stereotactic Volumetric Modulated Arc Therapy (VMAT) plans quantitively and predict gamma passing rates (GPRs) using machine learning. Methods: The entire dataset is exclusively made of stereotactic VMAT plans (301 plans with 594 beams) from Varian Edge LINAC. The GPRs were analyzed using Varian's portal dosimetry with 2%/2 mm criteria. A total of 27 metrics were calculated to investigate the correlation between metrics and GPRs. Random forest and gradient boosting models were developed and trained to predict the GPRs based on the extracted complexity features. The threshold values of complexity metric were obtained to predict a given beam to pass or fail from ROC curve analysis. Results: The three moderately significant values of Spearman's rank correlation to GPRs were 0.508 (p < 0.001), 0.445 (p < 0.001), and −0.416 (p < 0.001) for proposed metric LAAM, the ratio of the average aperture area over jaw area (AAJA) and index of modulation, respectively. The random forest method achieved 98.74% prediction accuracy with mean absolute error of 1.23% using five‐fold cross‐validation, and 98.71% with 1.25% for gradient boosting regressor method, respectively. LAAM, leaf travelling distance (LT), AAJA, LT modulation complexity score (LTMCS) and index of modulation, were the top five most important complexity features. The LAAM metric showed the best performance with AUC value of 0.801, and threshold value of 0.365. Conclusions: The calculated metrics were effective in quantifying the complexity of stereotactic VMAT plans. We have demonstrated that the GPRs could be accurately predicted using machine learning methods based on extracted complexity metrics. The quantification of complexity and machine learning methods have the potential to improve stereotactic treatment planning and identify the failure of QA results promptly. [ABSTRACT FROM AUTHOR]

Background: Intracranial stereotactic radiosurgery (SRS) aims at achieving highly conformal dose distribution and, at the same time, attaining rapid dose falloff outside the treatment target. SRS is performed using different techniques including dynamic conformal arcs (DCA) and volumetric modulated arc therapy (VMAT). Purpose: In this study, we compare dose conformity and falloff in DCA and VMAT plans for SRS with a single target. Methods: To compare dose conformity in SRS plans, we employ a novel conformity index CIdexp$C{I}_{{d}_{exp}}$, RTOG conformity index (CIRTOG$C{I}_{RTOG}$), and Riet‐Paddick conformity index (CIRP$C{I}_{RP}$). In addition, we use indices R50%$R50\% $, V10Gy${V}_{10Gy}$, and V12Gy${V}_{12Gy}$ to evaluate dose falloff. For each of the considered 118 cases of SRS, two plans were created using DCA and VMAT. A two‐tailed Student's t‐test was used to evaluate the difference between the employed indices for the DCA and VMAT plans. Results: The studied VMAT plans were characterized by higher dose conformity than the DCA plans. The differences between the conformity indices for the DCA plans and VMAT plans were statistically significant. The DCA plans had a smaller number of monitor units (MUs) and smaller indices R50%, V10Gy, and V12Gy than the VMAT plans. However, the differences between R50%, V10Gy, and V12Gy for the DCA and VMAT plans were not statistically significant. Conclusions: Although the studied VMAT plans had higher dose conformity, they also had larger MUs than the DCA plans. In terms of dose falloff characterized by parameters R50%, V10Gy, and V12Gy, DCA serves as a reasonable alternative to VMAT in the case of a single brain metastasis. [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]

Purpose: CT Hounsfield Units (HUs) are converted to electron density using a calibration curve obtained from physical measurements of an electron density phantom. HU values assigned to an MRI‐derived synthetic computed tomography (sCT) may present a different relationship with electron density compared to CT HU. Correct assignment of sCT HU values is critical for accurate dose calculation and delivery. The goals of this work were to develop a sCT calibration curve using patient data acquired on a clinically commissioned CT scanner and assess for CyberKnife‐ and volumetric modulated arc therapy (VMAT)‐based MR‐only treatment planning of prostate SBRT. Methods: Same‐day CT and MRI simulation in the treatment position were performed on 10 patients treated with SBRT to the prostate. Dixon in‐phase and out‐of‐phase MRIs were acquired on a 3T scanner using a 3D T1‐weighted gradient‐echo sequence to generate sCTs using a commercial sCT algorithm. CT and sCT datasets were co‐registered and HU values compared using mean absolute error (MAE). An optimized HU‐to‐density calibration curve was created based on average HU values across an institutional patient database for each of the four sCT tissue types. Clinical CyberKnife and VMAT treatment plans were generated on each patient CT and recomputed onto corresponding sCTs. Dose distributions computed using CT and sCT were compared using gamma criteria and dose‐volume‐histograms. Results: For the optimized calibration curve, HU values were −96, 37, 204, and 1170 and relative electron densities were 0.95, 1.04, 1.1, and 1.7 for adipose, soft tissue, inner bone, and outer bone, respectively. The proposed sCT protocol produced total MAE of 94 ± 20HU. Gamma values mean ± std (min‐max) were 98.9% ± 0.9% (97.1%–100%) and 97.7% ± 1.3% (95.3%–99.3%) for VMAT and CyberKnife plans, respectively. Conclusion: MRI‐derived sCT using the proposed approach shows excellent dosimetric agreement with conventional CT simulation, demonstrating the feasibility of MRI‐derived sCT for prostate SBRT treatment planning. [ABSTRACT FROM AUTHOR]

Background: To investigate the effect of the Increment of gantry angle (Inc) parameter setting of the Monaco Treatment planning system (Monaco TPS) on the dosimetry and quality parameters of the volumetric modulated arc therapy (VMAT) program for rectal cancer. Methods: A retrospective analysis was conducted on 50 patients with rectal cancer who underwent intensity modulated radiation therapy using the Monaco TPS system from 2020 to 2021. Under the same optimization function configuration and other parameter settings, the Inc parameters in the VMAT radiotherapy plan were set to 10°, 20°, 30°, and 40°. The dose‐volume histogram (DVH) was used to evaluate the dose distribution of the target area and the radiation dose of the organs at risk (OAR). The differences in the dosimetry of the planning target volume (PTV) and OAR, as well as the gamma pass rate (GPR) were compared. Results: In terms of target dose, D98, Dmin, HI, and conformity index (CI) of Inc10 group was significantly lower than those of Inc20, 30, and 40 groups (P < 0.05), and D2 of Inc10 group was significantly higher than that of Inc20 group (P = 0.009). We also found CI of Inc20 and 30 were significantly better than that of Inc40 (both P < 0.05). In terms of OAR dose, the study found that the Dmean, Dmin, V50%, V45%, and V40% for the bladder of the Inc10 group were lower than those of the other groups (all P < 0.05), the Dmean for femoral head of the Inc20 group was lower than that of the Inc30 group (P < 0.05), and Inc20 showed a better protective effect on the femoral head. The MUs tend to decrease as the Inc parameter setting is increased. The monitor unit (MU) in Inc10 group were significantly higher than those in Inc20, Inc30, and Inc40 groups, and the MU of Inc20 group was significantly higher than that of Inc40 group (both P < 0.05). We found that for the 3%/3 mm and 2%/2 mm standards, the GPRs of each plan were > 90%, which met clinical requirements. Conclusions: Different settings of Inc parameters have varying degrees of impact on target dose, OAR dose, and machine MU. It is important for doctors to choose different Inc parameters according to different clinical needs. [ABSTRACT FROM AUTHOR]

Background and Objectives: Conventional radiotherapies used in the current management of rectal cancer commonly cause iatrogenic radiotoxicity. Proton beam therapy has emerged as an alternative to conventional radiotherapy with the aim of improving tumour control and reducing off-set radiation exposure to surrounding tissue. However, the real-world treatment and oncological outcomes associated with the use of proton beam therapy in rectal cancer remain poorly characterised. This systematic review seeks to evaluate the radiation dosages and safety of proton beam therapy compared to conventional radiotherapy in patients with non-metastatic rectal cancer. Materials and Methods: A computer-assisted search was performed on the Medline, Embase and Cochrane Central databases. Studies that evaluated the adverse effects and oncological outcomes of proton beam therapy and conventional radiotherapy in adult patients with non-metastatic rectal cancer were included. Results: Eight studies were included in this review. There was insufficient evidence to determine the adverse treatment outcomes of proton beam therapy versus conventional radiotherapy. No current studies assessed radiotoxicities nor oncological outcomes. Pooled dosimetric comparisons between proton beam therapy and various conventional radiotherapies were associated with reduced radiation exposure to the pelvis, bowel and bladder. Conclusions: This systematic review demonstrates a significant paucity of evidence in the current literature surrounding adverse effects and oncological outcomes related to proton beam therapy compared to conventional radiotherapy for non-metastatic rectal cancer. Pooled analyses of dosimetric studies highlight greater predicted radiation-sparing effects with proton beam therapy in this setting. This evidence, however, is based on evidence at a moderate risk of bias and clinical heterogeneity. Overall, more robust, prospective clinical trials are required. [ABSTRACT FROM AUTHOR]

The article presents a case study of a fair-skinned, elderly woman experiencing a sudden increase in skin malignancies after a long period of stability. Topics discussed include the management of skin lesions through shave and curettage, the impact of ruxolitinib on skin cancer progression, and factors contributing to the rapid rise in skin malignancies.

The article presents case studies addressing various clinical challenges related to melanoma and skin cancer management. Topics discussed include the initial approval of immune checkpoint inhibitors, the prevalence of genetic mutations in melanoma, and the impact of artificial intelligence on skin cancer diagnostics.

Abstract Thoracic bulky esophageal cancer shrinks during radiotherapy, changing the location and shape of the surrounding heart and lungs. The current study aimed to explore how replanning by volumetric-modulated arc radiotherapy (VMAT) and three-dimensional conformal radiotherapy (3DCRT) influences the target coverage and dose to organs at risk in locally advanced unresectable middle to lower thoracic esophageal cancer. We retrospectively collected CT simulation images of initial and boost radiotherapy plans for locally advanced unresectable thoracic esophageal cancer in 17 consecutive patients. First, we created boost plans of 20 Gy using 3DCRT and VMAT on the initially acquired CT images. Second, we replicated the process on CT images acquired after 20–40 Gy of radiotherapy. We then compared non-replanned boost radiotherapy plans with replanned boost plans. Replanned radiotherapy delivered more conformal doses to the target and reduced heart and lung doses. VMAT reduced more irradiated mean doses to the heart than 3DCRT in the case of replanning (1.7 and 1.1 Gy, p