PURPOSE:CT-guided adaptive radiotherapy (CTgART) offers significant clinical benefits, but its utilization is often limited by resource demands and rigid workflows. This study presents a flexible and scalable "Adapt-on-Demand" (AOD) framework that integrates the adaptive capabilities of the Varian Ethos platform with the high-throughput IGRT delivery of the Varian Halcyon, supported by automated scripting. METHODS:We developed an end-to-end dual-platform workflow that dynamically transitions between ART and IGRT delivery based on patient needs. Key components include Eclipse Scripting API (ESAPI) automation to streamline adapted plan ingestion from the Ethos Treatment Planning and Management System (TPMS) export directory, compatibility conversion for Halcyon delivery, and ARIA chart setup. The framework was evaluated through time-efficiency analysis and longitudinal tracking of ART utilization and machine throughput. Multi-institutional deployment was also conducted to validate generalizability. RESULTS:Automation reduced plan setup time from 45 to 8 min (p < 0.001, unpaired t-test), and direct comparison of MLC leaf positions confirmed exact agreement between Ethos-native and converted plans across all control points. ART utilization on the Ethos platform increased from 17% to 77% following IGRT offloading to Halcyon. The workflow was successfully implemented at two external sites without code modification, demonstrating portability. CONCLUSION:This AOD framework enables flexible ART delivery without compromising workflow efficiency. By automating inter-platform transitions and alleviating adaptive system burden, it improves clinical throughput and broadens patient access to ART. This work also underscores the importance of system interoperability and provides a scalable model adaptable across diverse practice settings.

This study used X-ray Velocimetry (XV) to explore lung damage in a model of Acute Respiratory Distress Syndrome (ARDS). XV is a novel imaging technique that uses short X-ray videos recorded from 5 angles around the lung acquired with a fluoroscope during breathing to create detailed 3D maps showing how the lungs expand. Here, we introduced a lung injury in pigs to mimic damage from inhaling stomach contents, with XV images taken before and after a localised hydrochloric acid delivery. XV revealed localised ventilation changes at the injury site, as well as compensatory shifts in other lung regions. This pilot study provides a non-invasive, targeted approach to assess lung diseases, offering significant advantages over traditional methods. Our findings highlight the potential of XV to advance respiratory research and improve diagnostics and treatments for conditions like ARDS. This first demonstration of spatially resolved ventilation mapping in an ARDS model shows promise for both preclinical studies and clinical applications.

Cystic fibrosis (CF) is an inherited disorder associated with respiratory distress due to the muco-obstruction of the airways and compromised lipid composition of sputum. Altered pulmonary homeostasis results in people with CF experiencing chronic infections with treatment-resistant respiratory pathogens, such as multi-drug-resistant Pseudomonas aeruginosa . Changes in dietary fatty acids can alter respiratory function by altering mucus viscosity. However, the efficacy of such dietary approaches may be affected by the hepato-biliary complications commonly experienced by CF patients. Interestingly, bacterial infections in the lung can also influence lipid metabolism in the liver. In this study we sought to delineate the influence of infection and diets enriched with lard verses fish oil on lipid speciation and trafficking in distinct niches, and their influence on lung and liver function in a Sprague-Dawley rat model of CF. As expected, the dietary intervention induced distinct shifts in host lipid profiles, including higher abundances of ω-3 fatty acids in fish oil fed animals; however, the magnitude of these increases was greater in wild-type (WT) rats than in CF rats. Similarly, infection-induced lipid fluxes were prominent in WT animals, with fewer changes observed in CF mutant animals. Diet did not influence liver function in our study, but rather, even 3 weeks after P. aeruginosa challenge, infected animals demonstrated mild liver damage, which was at a similar level between WT and CF rats. Infection was associated with increased elastance and reduced compliance across groups. However, dietary fatty acid modification did not significantly alter baseline lung mechanics nor modify the mechanical response to infection in CF animals. This study advances our understanding of CF lipid biology in the context of diet and infection, which are core facets of CF disease complications.

Intensity modulated radiation therapy (IMRT) is increasingly used for total body irradiation (TBI) due to its ability to deliver myeloablative doses while sparing radiosensitive organs. To enable consistent evaluation in future National Clinical Trials Network (NCTN) studies, the NRG Hematologic Malignancies Working Group (HMWG) convened IMRT-TBI experts and NCTN leaders to develop consensus recommendations for standardized multi-institutional implementation. A 47-question survey was distributed to NRG institutions utilizing total body irradiation treated with intensity modulated radiation therapy (IMRT-TBI) to characterize current planning and delivery practices. Responses were analyzed for commonalities and variations. A multidisciplinary working group reviewed survey findings, developed consensus-based technical and clinical recommendations, and created a standardized template for IMRT-TBI integration into NCTN protocols. Topics included simulation, contouring, planning, organ-at-risk (OAR) constraints, quality assurance (QA), image guided radiation therapy, commissioning, credentialing, and safeguards for clinical trial conduct. Eight institutions with collective experience treating more than 750 patients with IMRT-TBI responded. Most centers used volumetric modulated arc therapy (VMAT) to the upper body with anteroposterior/posteroanterior fields to the lower body, 3 to 9 isocenters, lower dose rates for lung fields (100-200 MU/min), and no physical bolus. Common OAR constraints included lungs mean dose <8 Gy, kidneys mean dose <6 to 8 Gy, and lenses maximum dose <90% of prescription. All respondents used auto-segmentation; 50% used auto-planning. QA practices varied, but patient-specific QA passing rates were high (>95% with 3%/2 mm gamma). Consensus recommendations for clinical trial use were established, including standardized planning target volume definitions, OAR sparing goals, dosimetric constraints, QA requirements, and credentialing processes. IMRT-TBI offers the potential for reduced toxicity and improved dose precision compared with total body irradiation treated with a 2-dimensional technique, but its complexity requires careful standardization in multi-institutional trials. The NRG HMWG and collaborating NCTN experts developed the consensus-based technical and clinical framework for incorporating IMRT-TBI into cooperative group protocols. Adoption of these recommendations will facilitate consistent implementation and enable rigorous evaluation of outcomes.

Functional lung imaging enables pulmonary parameters, including ventilation, perfusion, gas exchange, and biomechanics, to be mapped and quantified noninvasively throughout the lungs. Pulmonary function testing is generally more difficult to perform in a child in comparison to an adult, and so pulmonary functional imaging has the potential to significantly benefit pediatric cohorts, giving clinicians an additional tool in assessing and managing pediatric lung disease. This scoping review aims to (1) identify current and emerging functional lung imaging techniques that have been investigated in pediatric cohorts and (2) describe how they have been compared to pulmonary function tests. PubMed, EMBASE, and CINAHL were searched for studies comparing pulmonary functional imaging techniques with pulmonary function testing in pediatric cohorts ≤ 18 years old. A total of 54 studies were included. Techniques were grouped into magnetic resonance imaging (MRI), computed tomography (CT), electrical impedance tomography (EIT), X-ray, and nuclear medicine methods. Most studies compared spirometry, multiple breath nitrogen washout, or both. At present, hyperpolarized gas MRI studies are the most widely investigated modality in children. However, despite the multiple different modalities investigated, there are no methods that have entered standard clinical pediatric use. Further research into functional lung imaging in pediatrics is required to provide validation, standardization, and establishment of normal values prior to implementation of these modalities into routine clinical care.

Background/Objectives: Patients with early-stage non-small cell lung cancer (NSCLC) or limited lung metastases and compromised lung function, such as those with interstitial lung disease (ILD) or chronic obstructive pulmonary disease (COPD), or other factors rendering them high-risk for surgery or medically inoperable, face increased risks of treatment-related toxicity from stereotactic ablative radiation therapy (SABR). This study evaluated a novel treatment approach to mitigate these risks. Methods: We investigated Personalized Ultra-Fractionated Stereotactic Adaptive Radiotherapy (PULSAR), delivered as pulsed radiation every three weeks, in patients with <5 cm lung tumors and ILD, COPD, or prior therapy. Treatment occurred between 2022 and 2024. Online adaptive radiotherapy (o-ART) was employed in 20 patients (80%) to modify treatment plans when anatomical changes warranted replanning. Primary outcomes included volumetric tumor response, changes in dose to organs at risk (OARs) and acute events, while secondary outcomes included local and tumor control, and overall survival. Results: Twenty-three patients received PULSAR treatment at doses between 40 Gy and 60 Gy in 5 fractions and one patient received 54 Gy in 3 fractions, with a median follow-up time of 16.2 months. Approximately half of treated patients demonstrated volumetric tumor response, with median residual volume of 70% (range 36-100%) at maximal response. Among the 20 patients (80%) who underwent online adaptive replanning, significant reductions in OAR dosimetry were observed for all organs assessed including the Dmax for heart (p = 0.0053), bronchus (p = 0.0003), esophagus (p = 0.0005), spinal cord (p = 0.025), and the lung V20 Gy and V12.5 Gy (p < 0.0001). Treatment-related toxicity included two grade 1-2 adverse events and six grade 3 events consisting of pneumonitis, dyspnea or lung infection, with no grade 4 or 5 events. Median progression-free survival was 21.1 months, with 1-year overall survival of 74% and 1-year local control of 100%. Conclusions: PULSAR shows promise as a feasible treatment option for high-risk patients with NSCLC or lung metastases, demonstrating no grade 5 events and complete tumor control. Additional research is needed to fully evaluate the safety profile of PULSAR in the high-risk subgroups and whether PULSAR's treatment intervals and adaptive planning advantages lead to improved long-term outcomes compared to conventional, uninterrupted SABR regimens.

Almost all patients with mucopolysaccharidosis (MPS) develop respiratory dysfunction of varying severity during disease progression. While respiratory disease in MPS has traditionally been attributed to upper airway obstruction caused by glycosaminoglycan (GAG) accumulation in the trachea and bronchi, involvement of the intrapulmonary conducting airways and lung parenchyma remains poorly defined. Here, we characterised lung disease in a mouse model of MPS I using a combination of non-invasive X-ray Velocimetry (XV) functional lung imaging and gold-standard flexiVent respiratory mechanics testing, complemented by lung volume measurements and histological analysis. XV provides regional ventilation information across the entire lung during tidal breathing. MPS I mice demonstrated reduced mean specific ventilation (the average regional expansion of lung tissue across the respiratory cycle), driven predominantly by reduced ventilation in the inner (mediastinal-adjacent) lung regions, with evidence of spatially heterogeneous ventilation distribution. Lung mechanics testing showed increased conducting airway resistance, increased respiratory system compliance and reduced tissue elastance, consistent with impaired elastic recoil and expiratory flow limitation. Lung volume analysis revealed reduced opening pressure following degassing together with increased residual volume, functional residual capacity and vital capacity. Histological analysis demonstrated heterogeneous parenchymal architecture with regions of enlarged airspaces. Together, these findings demonstrate that respiratory dysfunction in MPS I is not limited to upper airway obstruction but also involves intrinsic abnormalities of the intrapulmonary conducting airways and lung parenchyma. This intrinsic pulmonary pathology likely contributes to obstructive lung disease and may underlie the susceptibility to respiratory failure observed in patients with MPS I.

Background and Purpose:Direct-to-Unit (simulation-omitted) adaptive radiotherapy (ART) enables same-day treatment by generating treatment plans from diagnostic images, eliminating the need for computed tomography (CT) simulation. These workflows rely on online plan re-optimization to account for anatomical, CT-number, and setup variations. However, no standardized end-to-end (E2E) credentialing protocol currently exists to validate the accuracy of Direct-to-Unit ART. Although customized ART phantoms are available, they are often costly, and impractical for one-time commissioning. To address this gap, we developed a low-cost E2E commissioning framework using a commercially available CIRS ZEUS phantom to verify workflow accuracy while minimizing financial burden. Materials and Methods:E2E commissioning tests were performed on Varian Ethos and Elekta Unity systems using a CIRS ZEUS phantom (Model 008Z) equipped with inserts for ionization chamber point-dose and planar film measurements. The ionization chamber and Gafchromic EBT4 films were independently cross-calibrated on an Elekta Versa linear accelerator. Pseudo-diagnostic CT datasets were generated and deformed to simulate anatomical variation. Pre-plans (2 Gy × 30 fractions) were created and delivered across three ART fractionation schemes. Point-dose measurements were compared with system-reported values, and planar dose distributions were evaluated using global gamma analysis. Results:All point-dose differences were within 3% (for high-dose regions) or 3 cGy (for low-dose regions) of the system-reported values. All planar film measurements achieved gamma pass rates exceeding 90% using 3%/3 mm criterion. Conclusion:This cost-effective E2E approach provides a practical commissioning solution for Direct-to-Unit ART, supporting safe clinical implementation and facilitating cross-institutional standardization.

Recurrent bacterial infections with Pseudomonas aeruginosa result in chronic airway inflammation, lung damage and eventual respiratory failure, and are the major cause of morbidity and mortality in people with cystic fibrosis (CF). Animal models are essential for understanding disease progression and assessing potential treatments in the presence of infection. Previously reported P. aeruginosa lung infection rodent models for CF research have weaknesses that include being acute rather than chronic infections, high levels of associated mortality, use laboratory strains of P. aeruginosa, or do not utilise CF rodents. The aim of this study was to create a localised single-lung P. aeruginosa infection in wildtype and two CF rat models, by using a miniature bronchoscope to deliver bacteria embedded in agar beads generated from a clinical CF bacterial isolate. Cohorts of animals were assessed at days 7, 14, 21 and 63. The number of colony forming units were measured, along with bronchoalveolar lavage, flexiVent mechanics, X-ray Velocimetry (XV) ventilation analysis, and histopathology. The resulting infection was well tolerated by all animals of all genotypes with no mortality associated with the procedure or infection. The right-lung exhibited localised acute bronchopneumonia and lymphocytic vasculitis early, progressing to chronic interstitial pneumonia with fibrosis and emphysema. Bacteria persisted for 9 weeks (63 days) in all genotypes, with lung mechanics changes observed by day 63 of the infection. The precise delivery of bacterial laden beads using a miniature bronchoscope generated a controlled and reproducible infection that persisted for up to nine weeks, with minimal impact on animal health.

Single-cell RNA sequencing (scRNA-Seq) studies identified a novel subpopulation of epithelial cells along the rostrocaudal axis of human intestine, specifically marked by bestrophin 4 (BEST4), that are enriched for genes regulating pH, GPCR acid-sensing receptors, satiety, cGMP signaling, [Formula: see text] secretion, ion transport, neuropeptides, and paracrine hormones. Interestingly, BEST4+ cells in the proximal small intestine express CFTR but have not been widely linked to the previously described CFTR high-expresser cell (CHE) subpopulation in rat and human intestine. ScRNA-Seq studies in rat jejunum identified CHEs and a gene expression profile consistent with human small intestinal BEST4+ and neuropod cells. Protein immunolocalization confirmed that CHEs express CFTR, BEST4, neuropod proteins, high levels of intracellular uroguanylin (UGN), guanylyl cyclase-C (GC-C), and the proton channel otopetrin 2 (OTOP2), and display long basal processes connecting to neurons, confirming that Best4+ cells in the proximal small intestine are CHEs. OTOP2, GC-C, and CFTR traffic robustly into the apical domain of CHEs in response to acidic luminal conditions, indicating their roles in luminal pH regulation. In the ΔF508 cystic fibrosis (CF) rat jejunum, the loss of apical CFTR did not affect BEST4 protein expression in CHEs. However, there was an increased abundance of CHE cells in the ΔF508 rat jejunum compared with wild-type animals. Furthermore, ΔF508 rat CHEs expressed higher levels of GC-C at the apical domain compared with wild-type. These data implicate CHEs in intestinal CF disease pathogenesis.NEW & NOTEWORTHY This is the first study to identify CFTR high-expresser cells in the rat small intestine as neuropod cells capable of sensing and responding to luminal pH, and confirms that Best4+ cells are CHEs in the proximal small intestine. This study also provides the first characterization of CFTR and relevant mRNA and proteins in CHEs in CF rat models that provide insights into the significance of CHEs to CF intestinal disease.

Purpose: In online cone beam computed tomography (CBCT)-based adaptive radiation therapy (ART), nodal recontouring ensures sufficient nodal coverage by accounting for anatomic change but is uniquely challenging due to small target size and time pressure. This study evaluates the accuracy of rigid propagation versus artificial intelligence-guided deformation (AID) for nodal autosegmentation via comparison to nodal recontours delineated with unlimited time (ie, benchmark contours). Methods and Materials: We analyzed 25 nodal structures from 16 patients receiving pelvic online CBCT-based ART with nodal boost. Nodal structure sampling was informed by an initial power analysis. For each structure, we obtained rigidly propagated and AID-generated contours in addition to 2 benchmark contours and the clinical contour used in adapted plan generation. We calculated dice similarity coefficient (DSC), false-positive dice, false-negative dice, and 95% Hausdorff distance (HD95) between clinical, propagated, and AID contours against benchmark pairs and DSC and HD95 between benchmark pairs. The failure rate of nonbenchmark contours relative to benchmark pairs was calculated as the proportion of contours with an HD95 > 5 mm. We calculated the normalized D100, normalized D95, V100, and V95 of the adapted plan dose over all contours. Clinical tumor volume contours were used for all comparisons. Results: Median DSC versus benchmark contours were 0.68 for rigidly propagated and 0.58 for AID contours. A significant difference in false-negative dice (P = .01, Cohen’s d 0.806) was identified in benchmark-to-propagated versus benchmark-to-AID comparison. The failure rate of rigidly propagated, AID, and clinical contours was 20%, 48%, and 28% respectively. The median DSC between benchmark contours was 0.75. No significant differences across dose metrics were identified between contour types. Conclusions: Rigid propagation is superior to AID for initial contour generation in pelvic CBCT-based ART. Increased contouring time and image quality may improve contour quality and reduce interobserver variability but may be limited by the influence of individual contouring preferences.

Background and purpose In online cone beam CT (CBCT) based adaptive radiotherapy (ART), nodal re-contouring ensures sufficient nodal coverage by accounting for anatomic change but is uniquely challenging due to small target size and time pressure. This study evaluates the accuracy of rigid propagation vs. artificial-intelligence-guided deformation (AID) for nodal auto-segmentation via comparison to nodal re-contours delineated with unlimited time (i.e. benchmark contours). Materials and Methods We analyzed 25 nodal structures from 16 patients receiving pelvic online CBCT-based ART with nodal boost. Nodal structure sampling was informed by an initial power analysis. For each structure, we obtained rigidly propagated and AID-generated contours in addition to two benchmark contours and the clinical contour used in adapted plan generation. We calculated dice similarity coefficient (DSC), false positive dice (FPD), false negative dice (FND), and 95% Hausdorff distance (HD95) between clinical, propagated, and AID contours against benchmark pairs and DSC and HD95 between benchmark pairs. The failure rate of non-benchmark contours relative to benchmark pairs was calculated as the proportion of contours with a HD95 > 5 mm. We calculated the normalized D100, normalized D95, V100 and V95 of adapted plan dose over all contours. Clinical tumor volume (CTV) contours were used for all comparisons. Results Median DSC vs. benchmark contours was 0.68 for rigidly propagated and 0.58 for AID contours. A significant difference in FND (p = 0.01, Cohen’s d 0.806) was identified in benchmark-to-propagated vs. benchmark-to-AID comparison. The failure rate of rigidly propagated, AID, and clinical contours were 20%, 48%, and 28% respectively. The median DSC between benchmark contours was 0.75. No significant differences across dose metrics were identified between contour types. Conclusion Rigid propagation is superior to AID for initial contour generation in pelvic CBCT-based ART. Increased contouring time and image quality may improve contour quality and reduce inter-observer variability but may be limited by the influence of individual contouring preferences.

Purpose/objective(s)The GammaPod™ (GP) system, a contemporary platform dedicated to breast cancer (BC) radiotherapy, facilitates the delivery of accelerated partial breast irradiation (APBI) via the Co-60 prone-based stereotactic partial breast irradiation (CP-sPBI) technique. The precise CP-sPBI configuration permits reduced planning target volume (PTV) margins compared to other APBI techniques, creating an increased separation between PTV and organs at risk (OARs). This study explores the variability of heart-to-PTV distance and its effects on cardiac dosimetry.Materials/methodsAn APBI database of 102 consecutive patients treated with CP-sPBI between March 2019 and February 2023 was queried for retrospective analysis. Statistical analyses were performed to evaluate the mean and maximum (max) heart and left anterior descending artery (LAD) doses based on two parameters: 1) D-H, the minimum distance between the heart and the lumpectomy cavity PTV, and 2) D-LAD, the minimum distance between the LAD and the lumpectomy cavity PTV. The median values of D-H and D-LAD, measured on either axial or sagittal planes, were employed to categorize patients based on cardiac dose levels.ResultsThe analysis revealed a statistically significant difference in the mean and max heart dose between patients with left-sided and right-sided breast cancer. Specifically, in left-sided breast cancer patients, median D-H and D-LAD cutoffs were identified as 2.67 and 3.22 cm, respectively. Patients with D-H less than 2.67 cm exhibited significantly higher mean (1.77 vs. 0.75 Gy; p < 0.01) and max heart doses (15.21 vs. 4.38 Gy; p < 0.01) compared to those with D-H greater than or equal to 2.67 cm. Similarly, lower D-LAD values (<3.22 cm) demonstrated a statistically significant association with increased arterial dose compared to higher D-LAD values (≥3.22 cm).ConclusionsLeveraging its sharp dose fall-off characteristic, the GP treatment delivery system facilitates the delivery of five-fraction APBI while maintaining acceptable cardiac dosimetry parameters. This is particularly advantageous for tumors situated further from the heart because heart doses dissipate with distance. The estimates of heart dose based on the distance to the heart and LAD from PTV have the potential to serve as a valuable tool for clinicians, aiding in more refined risk evaluation and patient selection for CP-sPBI.

Objective:This scoping review aims to identify current and emerging functional lung imaging techniques that have been used in pediatric cohorts and how these techniques have been compared to pulmonary function tests.Introduction:Functional lung imaging enables the assessment of distribution of pulmonary parameters-including ventilation, perfusion, gas exchange, and biomechanics-to be mapped and quantified non-invasively throughout the lungs. In comparison to pulmonary function testing, functional lung imaging can provide additional clinically relevant information on the regional and spatial localization of lung disease. Pulmonary functional imaging has the potential to significantly benefit a pediatric cohort, giving clinicians an additional tool in assessing and managing pediatric lung disease.Eligibility criteria:Functional lung imaging techniques that have been investigated and compared or correlated with a pulmonary function test in pediatric cohorts will be identified and reviewed. Quantitative study designs and functional lung imaging techniques used in reviews and conference abstracts will be included if there is a comparative pulmonary function test. Gray literature will be screened for evidence of new and emerging technologies. Established author opinion will also be sought on new and emerging technologies in pediatric functional lung imaging.Methods:Key sources to be searched include MEDLINE, Embase, and CINAHL. Two reviewers will independently screen titles and abstracts against eligibility criteria. Extracted data will include details about the concept, context, study methods, and key information relevant to the study question. Data will be presented in tabular format, accompanied by a narrative synthesis.Review registration:OSF https://osf.io/snuc6

Purpose: Daily online adaptive radiation therapy (oART) opens the opportunity to treat gastric mucosa-associated lymphoid tissue (MALT) lymphoma with a reduced margin. This study reports our early experience of cone beam computed tomography (CBCT)based daily oART treating gastric MALT lymphoma with breath-hold and reduced margins. Methods and Materials: Ten patients were treated on a CBCT-based oART system. Organs at risk (OARs) and the clinical target volume (CTV) were adjusted based on the daily CBCT. Planning target volume (PTV) was derived from the CTV with a 0.5 to 0.7 cm margin with breath-hold. Multiple beam arrangements were compared during the preplanning phase to ensure minimal monitor unit (MU) for patient comfort and breath-hold reproducibility. For 108 fractions from the 10 patients, the PTV, CTV coverage, and Paddick conformity index (CI) were compared between the adapted and scheduled plans. The MU, Paddick CI, and gradient index were compared using relative percentage differences between the adapted plans and preplans. The OAR doses from 106 fractions across 9 patients were reported for the preplans, adapted plans, and scheduled plans. The time statistics for each step of the clinical workflow were recorded and reported for 93 treatment fractions from 9 patients. Results: The PTV volume varied from- 37.1% to 90.5% (11.7% f 18.5%) throughout treatments across all patients. The adapted plan was chosen as the treatment plan for each fraction because of superior PTV and CTV coverage while maintaining a similar OAR dose. The PTV and CTV coverage for the adapted and scheduled plans was V Rx = 95.0% f 0.3% versus 64.1 f 19.6% and V Rx = 99.9 f 0.1% versus 74.0% f 22.2%, respectively. The adapted plans' MU, Paddick CI, and gradient index were, on average, 4.1%, 0.4%, and 4.2% of the preplan values, respectively. The console's adaptive workflow and physician time were 25 f 7 and 19 f 6 minutes, respectively. Conclusion: A CBCT-based oART system with the proposed workflow is feasible for treating patients with gastric MALT lymphoma using a reduced PTV margin while maintaining excellent target coverage within a reasonable time, resulting in consistent adapted plan quality. This approach can be expanded to a larger cohort of gastrointestinal patients. (c) 2024 The Authors. Published by Elsevier Inc. on behalf of American Society for Radiation Oncology. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Online adaptive radiotherapy (ART) is rapidly transforming clinical radiation oncology by enabling adaptation of treatment plans based on patient-specific anatomical and biological changes. However, most medical physics training programs lack structured education in ART. To address this critical gap, the Medical Physics Adaptive Radiotherapy (MPART) Fellowship was established at our center to train post-residency or practicing physicists in advanced adaptive technologies and workflows. The MPART Fellowship is a two-year program that provides immersive, platform-specific training in CBCT-guided (Varian Ethos), MR-guided (Elekta Unity), and PET-guided (RefleXion X1) radiotherapy. Fellows undergo modular clinical rotations, hands-on training, and dedicated research projects. The curriculum incorporates competencies in imaging, contouring, online planning, quality assurance, and team-based decision-making. Evaluation is based on the Accreditation Council for Graduate Medical Education competency domains and includes milestone tracking, mentor reviews, and structured presentations. The fellowship attracted applicants from both domestic and international institutions, reflecting strong demand for formal ART training. Out of 22 applications, two fellows have been successfully recruited into the program since 2024. Fellows actively participate in all phases of adaptive workflows and are expected to function at near-attending levels by the second year of their training. Each fellow also leads at least one translational or operational research project aimed at improving ART delivery. Fellows contribute to clinical coverage and lead developmental projects, resulting in presentations and publications at the national and international levels. The MPART Fellowship addresses a vital educational need by equipping medical physicists with the advanced competencies necessary for implementing and leading ART. This program offers a replicable framework for other institutions seeking to advance precision radiation therapy through structured post-residency training in adaptive radiotherapy. As this fellowship program is still in its early phase of establishment, the primary goal of this paper is to introduce the structure, framework, and implementation model of the program. Comprehensive outcome analyses-such as quantitative assessments, fellow feedback, and longitudinal competency evaluations-will be incorporated in future work as additional cohorts complete training.