BackgroundFractionated stereotactic radiosurgery (fSRS) using LINAC‐based volumetric‐modulated arc therapy (VMAT) has become widely adopted and achieved favorable outcomes. However, this technique involves extremely small field sizes, making pre‐treatment quality assurance (QA) with high‐resolution detectors essential.PurposeThis study aimed to evaluate the error detection sensitivity and utility of EPID using 3D in vivo dosimetry based on dose‐volume histogram (DVH) analysis for brain fSRS pre‐treatment QA.MethodsVMAT plans were generated for spherical planning target volumes (PTVs) with diameters of 1–3 cm centered in SRS MapCHECK. A monitor unit (MU) output error was introduced in increments, and the leaf gap width was systematically opened and closed. Finally, multi‐leaf collimator (MLC) shift errors were applied. The error detection sensitivity was evaluated with these intentional errors. We compared this with the SRS MapCHECK 2D gamma analysis conventionally used in pre‐treatment QA. For in vivo dosimetry, 3D dose calculations were performed with PerFRACTION using cine‐mode electronic portal imaging device images and log files. DVH parameters such as D98%, D95%, D2%, and average doses of the PTV were compared between the base plan and the error plans. The 2D gamma analysis was performed using global gamma of 3%/2 mm, 3%/1 mm, 2%/2 mm, 2%/1 mm, and 1%/1 mm.ResultsThe 2D gamma analysis revealed no MU output errors for the 1 cm target across all criteria. The 2%/1 mm criterion effectively detected errors in leaf gap width and MLC shifts in some cases. Conversely, all error types were detected by 3D in vivo dosimetry using D95% of the target.ConclusionIn pre‐treatment QA for brain fSRS, 3D in vivo dosimetry based on DVH analysis demonstrated superior error detection sensitivity compared to conventional 2D gamma analysis. Our results suggest that 3D in vivo dosimetry is a useful tool for pre‐treatment QA in brain fSRS.

PurposeThis study aimed to compare the sensitivity of log file‐based quality assurance (LF‐QA) and measurement‐based quality assurance (MB‐QA) for detecting multileaf collimator (MLC) positional errors and to evaluate the dosimetric impacts of MLC mechanical drive train defects.MethodsMechanical degradation of the MLC was simulated on a TrueBeam STx system by inducing three defect types: T‐nut surface wear (0.5–1.2 mm), drive screw thread wear, and motor degradation. MLC positioning accuracy was assessed using a rotational Picket Fence (PF) test, and the dosimetric impacts were evaluated on clinical breast intensity‑modulated radiation therapy (IMRT) and prostate volumetric‑modulated arc therapy (VMAT) plans. LF‐QA and MB‐QA were performed concurrently under identical delivery conditions. Gamma passing rates (GPRs) and dose‐volume histogram (DVH) analyses were compared between baseline and defective deliveries.ResultsLF‐QA detected positional deviations between baseline and defective conditions (<0.14 mm; p < 0.05) but consistently underestimated the extent of the induced defects. Correspondingly, LF‐QA gamma analysis (GPRs ≈ 100%) and DVH metrics (∆D < 0.2%) showed no detectable dosimetric differences. MB‐QA exhibited higher sensitivity to specific MLC defects, identifying localized fluence variations for T‐nut surface wear, whereas no discernible differences were observed for drive screw thread wear or motor degradation. MB‐QA gamma analysis revealed localized dose differences of up to 15% in breast IMRT and 7.4% in prostate VMAT. DVH analysis further demonstrated clinically relevant dose variations in organs at risk (OARs), including the contralateral breast (ΔDmean: 5.52%) and right lung (ΔD1: 4.50%) in breast IMRT, and the penile bulb (ΔD99: 1.55%) in prostate VMAT.ConclusionLF‐QA showed limited sensitivity to sub‐millimeter MLC errors and did not capture clinically meaningful dosimetric deviations under mechanically degraded conditions. MB‐QA enabled superior error detection and clinically relevant dosimetric verification. These findings indicate that LF‐QA alone may be insufficient for patient‐specific QA and that incorporating MB‐QA is essential for ensuring reliable dosimetric verification.

BackgroundRadiotherapy workflows conventionally deliver one treatment plan multiple times throughout the treatment course. Non‐coplanar techniques with beam angle optimization or dosimetrically optimized pathfinding (DOP) exploit additional degrees of freedom to improve spatial conformality of the dose distribution compared to widely used techniques like volumetric‐modulated arc therapy (VMAT). The temporal dimension of dose delivery can be exploited using multiple plans (sub‐plans) within one treatment course. For instance, temporally feathered radiation therapy (TFRT) uses iso‐curative sub‐plans to deliver an alternance of higher and lower doses compared to a single plan to selected organs‐at‐risk (OARs), facilitating the dynamic recovery process of healthy tissues.PurposeThis study presents a simultaneous optimization framework based on direct aperture optimization with or without DOP to optimize multiple coplanar or non‐coplanar sub‐plans within one treatment course and demonstrates its use for TFRT planning.MethodsThe goal of the framework was to minimize an objective function consisting of weighted upper or lower dose‐volume, generalized equivalent uniform dose, and normal tissue objectives set on the dose distribution of each sub‐plan or the combined total plan. Reference VMAT and dynamic collimator trajectory radiotherapy (colli‐DTRT) single plans were created and used to derive the objectives for TFRT planning. The TFRT high‐to‐low dose modulation was integrated into the objective list and systematically investigated for a digital academic phantom using three variations (“soft”, “medium”, “hard”). Additionally, a “super‐soft” variation used the same objectives for all five sub‐plans (i.e., no high‐to‐low dose modulation). Furthermore, “medium” TFRT sub‐plans with colli‐DTRT were created for three more complex clinically motivated head and neck cases.ResultsFor the phantom, the sub‐plans were iso‐curative with target D98% within 1.6% of the reference plans. High‐to‐low OAR dose modulation was achieved with median Dmean differences between high and low dose fractions of 2.7% of the prescription dose (soft), 3.3% (medium), and 4.4% (hard) for VMAT. Median OAR Dmean differences were 2.8% of the prescription dose (soft), 6.3% (medium), and 6.1% (hard) for colli‐DTRT. The dose distributions of the total plans had higher homogeneity indices (HI = D98%/D2%) compared to the reference plans. Lower OAR Dmean were achieved for the soft, medium, and hard TFRT variation in the total plans compared to the reference plan. However, in the super‐soft variation only five of the 10 feathered OARs showed this reduction.For the three clinically motivated cases with colli‐DTRT, median OAR Dmean differences between the high and low dose fractions were 3.5%, 4.2%, and 7.5% of the prescription dose. The total plans’ dose distributions had higher HIs compared to their respective reference plans and lower or equal Dmean for all feathered OARs except for pharynx in one case.ConclusionA framework for the simultaneous optimization of multiple coplanar or non‐coplanar sub‐plans within one treatment course was developed. Simultaneous optimization was investigated with a phantom and three clinically motivated cases for TFRT planning. OAR dose modulation in the sub‐plans was achieved while increasing target homogeneity and reducing OAR doses in the dose distribution of the total plans compared to the reference plans.

PurposeThis study aimed to comprehensively compare the dosimetric characteristics of three different radiotherapy techniques—hybrid intensity‐modulated radiotherapy (hy‐IMRT), tangential volumetric‐modulated arc therapy (t‐VMAT), and continuous volumetric‐modulated arc therapy (c‐VMAT)—used after breast‐conserving surgery for left‐sided breast cancer in the target area and organs at risk (OARs) after breast‐conserving surgery for left‐sided breast cancer. This evaluation aims to provide a solid basis for individualized radiotherapy planning in clinical practice.MethodsTwenty female patients who underwent breast—conserving surgery for left—sided breast cancer were retrospectively selected. These patients were treated with hy‐IMRT, t‐VMAT, or c‐VMAT. The doses received by the target area and OARs were precisely evaluated. Additionally, the dose distribution in normal tissues and treatment time of the three radiotherapy plans were carefully compared.ResultsAll three techniques could meet the target zone dose requirements. In the planning gross tumor volume (PGTV), the average dose of hy‐IMRT was the highest. c‐VMAT demonstrated the best homogeneity index (HI) and conformity index (CI). For the planning target volume (PTV), c‐VMAT also showed outstanding performance in terms of homogeneity and conformity (p < 0.001). Regarding OAR doses, although there was no significant difference in the mean cardiac dose among the three techniques (p = 0.69), c‐VMAT had lower values in cardiac V10 dose volume, mean coronary left anterior descending (LAD) artery dose, and V20, V30, and V40 dose volumes, irradiating less of the cardiac low—dose and high—dose regions. c‐VMAT had lower left lung V30 and V40 doses, but its mean dose to the right lung was significantly higher than that of the other two groups. In terms of treatment time, t‐VMAT was significantly shorter than the other two groups, indicating the highest efficiency (p < 0.001).ConclusionC‐VMAT exhibits obvious advantages in target area uniformity, conformality, and protection of the heart and the affected lung. However, its significant dose impact on the right lung cannot be ignored and requires further attention. On the other hand, t‐VMAT has a remarkable advantage in treatment time. This study offers valuable references for clinicians to select the most suitable radiotherapy technique according to patients' specific conditions, such as tumor location, size, and OAR anatomical structures, aiming to optimize treatment outcomes and minimize adverse effects.

BackgroundStereotactic radiosurgery (SRS) poses challenges in calculating dose volume histograms (DVHs) due to the inherent spatial discretization uncertainties.PurposeTo develop a procedure for quantifying discretization errors and assessing DVH accuracy in intracranial SRS applications.MethodsThe capability of Monaco Treatment Planning System (TPS) to calculate structure and isodose volumes using slice thickness (ST) and dose grid (DG) of 1 mm was validated against analytical values, and in‐house calculations performed for 15 patients with brain metastases diameters ranging from 6 to 30 mm treated with a VMAT technique. For these patients, STs of 1.5 and 2 mm, and DGs of 2 and 3 mm were also explored to establish clinically acceptable thresholds, using isodose volume calculations and clinically relevant DVH indices.ResultsMonaco TPS presented an excellent performance in calculating structure and isodose volumes for the 1‐mm ST and DG, with an average percentage difference compared to analytical and in‐house calculations within 2.1%. For the clinical treatment plans, switching to 2 and 3‐mm DGs led to statistically significant differences compared to 1‐mm DG across all the considered indices, yet the variations between the 1 and 2‐mm DGs remained under 5% when target diameters exceeded 20 mm. Although no statistical differences were observed between the calculated indices when different STs were considered, clinically significant differences were observed in selected cases with lesion diameters smaller than 20 mm.ConclusionMonaco TPS demonstrated excellent performance in calculating structure and isodose volumes pertinent to SRS applications using 1‐mm ST and DG, while adherence to 1‐mm ST and DG should be maintained in clinical cases, unless target diameters surpass 20 mm, where STs and DGs up to 2 mm could be also utilized. The method developed in this study could act as a quality assurance procedure in order to establish clinically relevant discretization thresholds for SRS platforms.

Abstract BackgroundConventional patient‐specific quality assurance (PSQA) methods rely on time‐consuming physical measurements. While previous studies have successfully employed machine learning (ML) models to predict gamma passing rates (GPRs), their clinical utility remains limited due to GPR's weak correlation with dose‐volume histogram (DVH) parameters. Thus, developing a novel PSQA framework that is non‐measured and DVH‐based (NMDB) presents a promising alternative.PurposeTo develop an NMDB PSQA framework incorporating ML to classify treatment plans susceptible to delivery errors.MethodsThis study analyzed 560 lung stereotactic body radiation therapy (SBRT) plans with volumetric‐modulated arc therapy (VMAT) delivered on a TrueBeam system (Varian Medical Systems), including 331 plans with saved trajectory log files. Log‐based analysis categorized delivery discrepancies in multileaf collimator (MLC) and gantry positions based on speed and gravity effect. Mean and standard deviation (STD) values for each category were calculated and predicted using linear regression. Additionally, physical variability was evaluated by analyzing periodic machine QA data to account for machine calibration uncertainty. Final discrepancies were calculated through error propagation, integrating speed, gravity, and physical variability. Gaussian noise was applied to control point values in all plans based on the estimated discrepancy means and STDs. Doses were recalculated for these perturbed plans, and the resulting DVH metrics were compared to the original plans. PTV F‐scores, combining coverage and conformality, were computed to quantify plan susceptibility to delivery errors, with a threshold set to classify the top 20% most vulnerable plans. ML models, including random forest (RF), support vector machine (SVM), and artificial neural network (ANN), were trained on features extracted from DICOM plans and doses, including basic plan parameters, planned DVH metrics, dosiomics, and histogram‐based features. The 80:20 train‐test split was implemented, with feature reduction based on statistical significance and collinearity. Models were optimized using hyperparameter tuning and recursive feature elimination. Their performance was assessed using the area under the receiver operating characteristic curve (ROC AUC) and average precision (AP) scores.ResultsHigh correlation coefficients (CCs) were noted between gantry error STDs and the gantry offsets (CC = ‐0.53), MLC error means and MLC speeds (CC = ‐0.99), and MLC error means and gravity vectors (CC = +0.77). Although DVH discrepancies for organs at risk (OARs) were minimal (&lt; 1%), PTV metrics showed more considerable variations, including average changes of 3.2% for V100% and 3.0% for conformity index. PTV F‐scores varied by 1.6% on average, with a 2.3% threshold identifying susceptible plans. ML models demonstrated strong classification performance on the testing dataset, achieving ROC AUC scores of 0.97 and AP scores of 0.90 (SVM, ANN) and 0.91 (RF).ConclusionThis study introduces a novel NMDB PSQA framework for lung SBRT VMAT plans, incorporating DVH metrics like the PTV F‐score and real‐time ML classification of susceptible plans. By eliminating the need for physical measurements, this framework enables online adaptive therapy and early feedback during planning, presenting substantial potential for clinical implementation and broader applications.

PurposeVolumetric‐modulated arc therapy (VMAT) treatment planning allows a compromise between a sufficient coverage of the planning target volume (PTV) and a simultaneous sparing of organs‐at‐risk (OARs). Particularly in the case of lung tumors, deciding whether it is possible or worth spending more time on further improvements of a treatment plan is difficult. Therefore, this work aims to develop a knowledge‐based, structure‐dependent, automated dose volume histogram (DVH) prediction module for lung tumors.MethodsThe module is based on comparing geometric relationships between the PTV and the surrounding OARs. Therefore, treatment plan and structure data of 106 lung cancer cases, each treated in 28 fractions and 180 cGy/fx, were collected. To access the spatial information, a two‐dimensional metric named overlap volume histogram (OVH) was used. Due to the rotational symmetry of the OVH and the typically coplanar setup of the VMAT technique, OVH is complemented by the so‐called overlap‐z‐histogram (OZH). A set of achievable DVHs is predicted by identifying plans in the database with similar OVH and OZH. By splitting the dataset into a test set of 22 patients and a training set of 84 patients, the prediction capability of the OVH‐OZH combination was evaluated. For comparison between the predicted and achieved DVH curves the coefficient of determination R2 was calculated.ResultsThe total lung showed strong linearity between predicted and achieved DVH curves for the OVH‐OZH combination, resulting in a R2 value close to 1 (0.975 ± 0.022). The heart benefits the most of the OZH resulting in a high prediction capability, with a higher R2 of 0.962 ± 0.036 compared to the prediction with OVH only (0.897 ± 0.087).ConclusionThe combination of OZH and OVH was suitable for building a knowledge‐based automated DVH prediction module. Implementing this method into the clinical workflow of treatment planning will contribute to advancing the quality of VMAT plans.

The feasibility of simulation-free radiation therapy (SFRT) has been demonstrated but information regarding its routine care impact and scalability is lacking. In this single-institution, retrospective cohort study, all patients receiving palliative radiation therapy at an Australian tertiary cancer center were eligible for consideration of SFRT unless mask immobilization, a stereotactic technique, or a definitive dose was indicated. Coprimary endpoints were SFRT utilization, impact on consultation-to-RT time, and on-couch treatment duration. Timing metrics were compared with a contemporary local cohort that received simulation-based palliative radiation therapy using unadjusted Wilcoxon rank-sum tests and a propensity score-matched regression. Electronic patient-reported outcomes captured 2-week toxicity and pain response. Between April 2018 and February 2024, 2849 palliative radiation courses were delivered, of which 1904 were eligible. Of the 1904 courses, 1000 (52.5% SFRT utilization) received SFRT, including 668 using intensity-modulated radiation therapy/volumetric-modulated arc therapy. A total of 788 individual patients received SFRT and the median age was 71 years (IQR, 61-80) with 59% being male and 42% being Eastern Collaborative Oncology Group 2-4. SFRT utilization increased from 41% to 54% between years 2018-2019 and 2022-2024. SFRT reduced median consultation-to-RT time from 7.0 to 5.1 days (P < .0001) corresponding to an adjusted average treatment effect in the treated of -2.1 days (95% CI, -2.8 to -1.3). SFRT increased median on-couch treatment duration from 17.8 to 20.5 minutes (P < .0001; adjusted average treatment effect in the treated 2.6 minutes, 95% CI, 1.3-3.9). Patient-Reported Outcomes Version of the Common Terminology Criteria for Adverse Events grade 3 acute toxicity was 9% and at 4 weeks after RT, patients with moderate/severe pain at baseline (≥5/10) had a mean pain reduction of 3.5 points (7.1-3.6; P < .0001). Using widely available technologies, the SFRT-1000 cohort demonstrates routine care scalability with patient-centered and workflow benefits. SFRT is an attractive new paradigm implementable in most settings following adaptation to local requirements. Thus, SFRT opens new avenues to potentially improve access to palliative RT, which remains a global area of need.

Despite decades of experience with definitive chemo-radiotherapy (CRT) in cervical oesophageal cancer (CEC), the loco-regional control and survival outcomes are dismal. This review evaluated the outcomes of various treatment strategies being commonly utilized. A literature review was conducted to identify relevant articles on CEC published from years 2000-2023 addressing the predefined key questions. These questions focussed on the comparative outcomes of various primary treatment approaches (surgery, CRT, or trimodality treatment) and the radiation dose schedules, volumes, and techniques. CRT is the standard approach for treatment for CEC so far. The potential role of surgery and trimodality approach in settings of evolving surgical approaches needs to be validated. The high dose schedules that are preferentially practiced in CEC have not shown any benefit in improving the disease outcomes over the standard dose schedule of 50.4 Gy. The target volume delineation practice of elective nodal irradiation (ENI) does not have a proven benefit over the involved field irradiation (IFI). The limited evidence on radiation techniques suggests that intensity-modulated radiotherapy/volumetric-modulated arc therapy (IMRT/VMAT) techniques can improve toxicity profile over three-dimensional conformal radiotherapy (3DCRT), but no advantage proven in disease outcomes so far. This review will guide clinicians in decision-making for the management of this relatively rare entity and the directions for future research in these areas. Future large-scale multicentre prospective studies are needed for validating and standardizing our current practices and exploring potential options to improve the outcomes.

BackgroundLimited data are available to examine the effects of intensity‐modulated proton therapy (IMPT) on patient‐reported outcomes in patients with nasopharyngeal carcinoma (NPC). Thus, we assessed whether patients receiving IMPT reported a better short‐term quality of life (QoL) than those receiving volumetric‐modulated arc therapy (VMAT).MethodsWe consecutively invited newly diagnosed NPC patients who had undergone standard treatment protocol within 2 years post‐radiotherapy at our institute between 2021 and 2023 to participate in the observational study. All participants completed the EuroQol five‐dimension, World Health Organization Quality‐of‐Life—Brief, Sinonasal Outcome Test 22, Eustachian Tube Dysfunction Questionnaire‐7, and Eating Assessment Tool‐10 (EAT‐10) questionnaires. QoL functions were estimated using a kernel‐smoothing method. A linear mixed model introducing the inverse probability of treatment weighting was constructed to estimate the effect of IMPT versus VMAT.ResultsWe identified 94 patients who completed 120 QoL assessments. Participants receiving IMPT were younger and had higher levels of education and higher household income. QoL functions showed that post‐treatment EAT‐10 scores consistently appeared significantly lower for IMPT than VMAT. After adjusting for factors including age, gender, education, household income, and cancer stages, patients receiving IMPT consistently showed significantly better QoL scores in EAT‐10, indicative of a medium effect. Additionally, factors such as age, household income level, and treatment regimen might influence either generic or condition‐specific QoL.ConclusionsPatients receiving IMPT demonstrated potentially improved eating‐related QoL compared to those receiving VMAT within a 2‐year post‐radiotherapy period. However, larger head‐to‐head comparison studies are warranted to confirm these findings.

PurposeThis study aimed to improve the safety and accuracy of radiotherapy by establishing tolerance (TL) and action (AL) limits for the gamma index in patient‐specific quality assurance (PSQA) for intensity‐modulated radiation therapy (IMRT) and volumetric‐modulated arc therapy (VMAT) using SunCHECK software, as per AAPM TG‐218 report recommendations.MethodsThe study included 125 patients divided into six groups by treatment regions (H&N, thoracic and pelvic) and techniques (VMAT, IMRT). SunCHECK was used to calculate the gamma passing rate (%GP) and dose error (%DE) for each patient, for the planning target volume and organs at risk (OARs). The TL and AL were then determined for each group according to TG‐218 recommendations. We conducted a comprehensive analysis to compare %DE among different groups and examined the relationship between %GP and %DE.ResultsThe TL and AL of all groups were more stringent than the common standard as defined by the TG218 report. The TL and AL values of the groups differed significantly, and the values for the thoracic groups were lower for both VMAT and IMRT. The %DE of the parameters D95%, D90%, and Dmean in the planning target volume, and Dmean and Dmax in OARs were significantly different. The dose deviation of VMAT was larger than IMRT, especially in the thoracic group. A %GP and %DE correlation analysis showed a strong correlation for the planning target volume, but a weak correlation for the OARs. Additionally, a significant correlation existed between %GP of SunCHECK and Delta4.ConclusionThe study established TL and AL values tailored to various anatomical regions and treatment techniques at our institution. Establishing PSQA workflows for VMAT and IMRT offers valuable clinical insights and guidance. We also suggest developing a standard combining clinically relevant metrics with %GP to evaluate PSQA results comprehensively.

We evaluated the incidence of radiation-induced hypothyroidism and its risk factors in patients with head and neck cancer who underwent radiotherapy using simultaneous integrated boost-volumetric-modulated arc therapy (SIB-VMAT). This retrospective study included 86 patients who received definitive radiotherapy using SIB-VMAT for head and neck cancer. The incidence of ≥ grade 2 hypothyroidism was evaluated. We also evaluated the relationships between hypothyroidism development and clinical factors and thyroid dose-volume parameters. During a median follow-up period of 17 months (range=3-65 months), 31 patients (36.0%, 31/86) developed grade 2 hypothyroidism requiring hormone replacement therapy. No patients experienced ≥ grade 3 hypothyroidism. The cumulative incidences of hypothyroidism at 1 and 2 years after radiation therapy were 24.5% and 38.7%, respectively, with a median onset time of 10.0 months (range=3.0-35.0 months). Thyroid volume (p=0.003), volume of the thyroid spared at 60 Gy (VS60; cut-off value, 5.16 ml; p=0.009), VS70 (cut-off value, 8.0 ml; p=0.007), VS60 equivalent dose in 2 Gy fraction (EQD2; cut-off value, 7.78 ml; p=0.001), and VS70EQD2 (cut-off value, 10.59 ml; p=0.008) were significantly associated with the development of radiation-induced hypothyroidism. Radiation-induced hypothyroidism is not rare in patients with head and neck cancer undergoing radiotherapy using SIB-VMAT. Radiation dose-volume parameters detected in this study may be useful indicators to prevent this complication.

We performed scalp-avoidance whole-brain irradiation with volumetric-modulated arc therapy (SAWB-VMAT) as a component of craniospinal irradiation. In SAWB-VMAT with two coplanar arcs, radiation oncologists and medical physicists sometimes experience difficulty in reducing the dose to the scalp to below the cut-off equivalent dose in 2Gy per fraction (assuming α/β=2) to 50% (EQD50%scalp ). To investigate the advantage of adding coplanar or non-coplanar arcs in reducing the dose to the scalp in SAWB-VMAT, we conducted a planning study to compare the EQD50%scalp , the dose to other organs at risk (OARs), and target coverage in VMAT with two coplanar arcs (Co2arcVMAT), VMAT with three coplanar arcs (Co3arcVMAT), and VMAT with two coplanar and two non-coplanar arcs (NcVMAT). Co2arcVMAT, Co3arcVMAT, and NcVMAT plans were created for 10 pediatric patients with medulloblastoma. The planned target volume (PTV) included the regions of the whole brain, cervical spinal cord, cerebrospinal fluid space, and intervertebral foramen. The EQD50%scalp was evaluated separately for four areas (top, back, left, and right) in each case. The prescribed dose for the PTV was 35.2Gy in 22 fractions. The median EQD50%scalp of the top area was 21.9, 22.1, and 18.3Gy for Co2arcVMAT, Co3arcVMAT, and NcVMAT, respectively. The EQD50%scalp of the top area was significantly reduced in NcVMAT compared to those in Co2arcVMAT and Co3arcVMAT (p<0.05). The median EQD50%scalp of the top area for NcVMAT was<19.9Gy, which is the cut-off dose for severe permanent alopecia. There were no significant differences in EQD50%scalp in the three other areas, the dose to other OARs, or the dose coverage of PTV among the three techniques. NcVMAT could reduce the EQD50%scalp of the top area below the cut-off dose of 19.9Gy. NcVMAT appears to be a promising treatment technique for SAWB-VMAT.

Arc therapy allows for better dose deposition conformation, but the radiotherapy plans (RT plans) are more complex, requiring patient-specific pre-treatment quality assurance (QA). In turn, pre-treatment QA adds to the workload. The objective of this study was to develop a predictive model of Delta4-QA results based on RT-plan complexity indices to reduce QA workload. Six complexity indices were extracted from 1632 RT VMAT plans. A machine learning (ML) model was developed for classification purpose (two classes: compliance with the QA plan or not). For more complex locations (breast, pelvis and head and neck), innovative deep hybrid learning (DHL) was trained to achieve better performance. For not complex RT plans (with brain and thorax tumor locations), the ML model achieved 100% specificity and 98.9% sensitivity. However, for more complex RT plans, specificity falls to 87%. For these complex RT plans, an innovative QA classification method using DHL was developed and achieved a sensitivity of 100% and a specificity of 97.72%. The ML and DHL models predicted QA results with a high degree of accuracy. Our predictive QA online platform is offering substantial time savings in terms of accelerator occupancy and working time.

PurposeStereotactic ablative body radiotherapy (SABR) in the liver, RTOG‐1112 guides the treatment modalities including the dose constraints for this technique but not the plan parameters. This study is not only analyzing the plan quality by utilizing the plan parameters and indexes but also compares treatment modalities from the protocol implementation.Method and materialTwenty‐five patients treated in the period from February 2020 to September 2022 were recruited in this analysis. Two planners randomly selected the patients and modalities. The modalities employed were Volumetric‐Modulated Arc Therapy (VMAT) and Helical Tomotherapy (HT). Various parameters and indexes were used to access not only the plan quality but also to compare each modality. The parameters and indexes studied were the homogeneity index (HI), conformity index (CI), gradient distance (GD), and the dose received by the organs at risk.ResultThe data reveals that the mean volume of PTV is 60.8 ± 53.9 cc where these targets exhibit no significant difference between each modality. The HI shows a consistent value for both modalities. Between each modality, the CI value shows less deviation, but the HT shows slightly higher performance than VMAT. The value of GD is 1.5 ± 0.3 cm where the HT provides a shorter distance compared to VMAT as well.ConclusionThe parameters and indexes should be utilized for the plan evaluation although in the guidelines this was not required. Various modalities were employed for treatment. Both can achieve the treatment criteria with slightly low performance of VMAT.

Novel platform for subcutaneous tumor irradiation in mice.

The purpose of this article is to share the excitement of the science of proton therapy, told by two physicists, who started their career in this area at different times. The authors' journey spans the evolution of proton therapy over the past 30 years, taking the reader from the time when it was an extremely exotic treatment modality until its more common use today. Over this time period, the authors' research and development aimed at an improved understanding of the physical benefits of intensity-modulated proton therapy and arc therapy, treatment planning and optimization to take proton-specific uncertainties into account, and imaging to measure the proton range in the patient. The final section focuses on emerging themes to democratize proton therapy by substantially reducing its size and price, for much greater affordability and global availability of this treatment modality.

BackgroundHippocampal avoidance (HA) has been shown to preserve cognitive function in adult patients with cancer treated with whole‐brain radiation therapy for brain metastases. However, the feasibility of HA in pediatric patients with brain tumors has not been explored because of concerns of increased risk of relapse in the peri‐hippocampal region. Our aim was to determine patterns of recurrence and incidence of peri‐hippocampal relapse in pediatric patients with medulloblastoma (MB).Methods and materialsWe identified pediatric patients with MB treated with protons between 2002 and 2016 and who had recurrent disease. To estimate the risk of peri‐hippocampal recurrence, three hippocampal zones (HZs) were delineated corresponding to ≤5 mm (HZ‐1), 6 to 10 mm (HZ‐2), and >10 mm (HZ‐3) distance of the recurrence from the contoured hippocampi. To determine the feasibility of HA, three standard‐risk patients with MB were planned using either volumetric‐modulated arc therapy (VMAT) or intensity‐modulated proton therapy (IMPT) plans.ResultsThirty‐eight patients developed a recurrence at a median of 1.6 years. Of the 25 patients who had magnetic resonance imaging of the recurrence, no patients failed within the hippocampus and only two patients failed within HZ‐1. The crude incidence of peri‐hippocampal failure was 8%. Both HA‐VMAT and HA‐IMPT plans were associated with significantly reduced mean dose to the hippocampi (p < .05). HA‐VMAT and HA‐IMPT plans were associated with decreased percentage of the third and lateral ventricles receiving the prescription craniospinal dose of 23.4 Gy.ConclusionsPeri‐hippocampal failures are uncommon in pediatric patients with MB. Hippocampal avoidance should be evaluated in a prospective cohort of pediatric patients with MB.Plain Language SummaryIn this study, the patterns of disease recurrence in patients with a pediatric brain tumor known as medulloblastoma treated with proton radiotherapy were examined. The majority of failures occur outside of an important structure related to memory formation called the hippocampus. Hippocampal sparing radiation plans using proton radiotherapy were generated and showed that dose to the hippocampus was able to be significantly reduced. The study provides the rationale to explore hippocampal sparing in pediatric medulloblastoma in a prospective clinical trial.

A novel and clinically useful weight-optimized dynamic conformal arc in stereotactic radiation therapy of non-small cell lung cancer: Dosimetric comparison of treatment plans with volumetric‐modulated arc therapy

PurposeThe purpose of this study was to demonstrate the potential utility of cone‐beam computed tomography (CBCT)‐guided online adaptive radiotherapy (ART) under end‐exhalation breath‐hold (EE‐BH) conditions for pancreatic cancer (PC).MethodsEleven PC patients who underwent 15‐fraction volumetric‐modulated arc therapy under EE‐BH conditions were included. Planning CT images and daily 165 CBCT images were imported into a dedicated treatment planning system. The prescription dose was set to 48 Gy in 15 fractions. The reference plan was automatically generated along with predefined clinical goals. After segmentation was completed on CBCT images, two different plans were generated: One was an adapted (ADP) plan in which re‐optimization was performed on the anatomy of the day, and the other was a scheduled (SCH) plan, which was the same as the reference plan. The dose distributions calculated using the synthetic CT created from both planning CT and CBCT were compared between the two plans. Independent calculation‐based quality assurance was also performed for the ADP plans, with a gamma passing rate of 3%/3 mm.ResultsAll clinical goals were successfully achieved during the reference plan generation. Of the 165 sessions, gross tumor volume D98% and clinical target volume D98% were higher in 100 (60.1%) and 122 (74.0%) ADP fractions. In each fraction, the V3 Gy < 1 cm3 of the stomach and duodenum was violated in 47 (28.5%) and 48 (29.1%), respectively, of the SCH fractions, whereas no violations were observed in the ADP fractions. There were statistically significant differences in the dose–volume indices between the SCH and ADP fractions (p < 0.05). The gamma passing rates were above 95% in all ADP fractions.ConclusionsThe CBCT‐guided online ART under EE‐BH conditions successfully reduced the dose to the stomach and duodenum while maintaining target coverage.