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Background and purpose Neurocognitive decline in brain tumor patients treated with radiotherapy (RT) may be linked to cortical atrophy. We developed models to determine radiation treatment-planning objectives for cortex, which were tested on a sample population to identify the dosimetric cost of cortical sparing. Material and methods The relationship between the probability of cortical atrophy in fifteen high-grade glioma patients at 1-year post-RT and radiation dose was fit using logistic mixed effects modeling. Cortical sparing was implemented using two strategies: region-specific sparing using model parameters, and non-specific sparing of all normal brain tissue. Results A dose threshold of 28.6 Gy was found to result in a 20% probability of severe atrophy. Average cortical sparing at 30 Gy was greater for region-specific dose avoidance (4.6%) compared to non-specific (3.6%). Cortical sparing resulted in an increase in heterogeneity index of the planning target volume (PTV) with an average increase of 1.9% (region-specific) and 0.9% (non-specific). Conclusions We found RT doses above 28.6 Gy resulted in a greater than 20% probability of cortical atrophy. Cortical sparing can be achieved using region-specific or non-specific dose avoidance strategies at the cost of an increase in the dose heterogeneity of the PTV. [ABSTRACT FROM AUTHOR]

Abstract Background and purpose Auto-segmentation represents an efficient tool to segment organs on CT imaging. Primarily used in clinical setting, auto-segmentation plays an increasing role in research, particularly when analyzing thousands of images in the "big data" era. In this study we evaluate the accuracy of cardiac dosimetric endpoints derived from atlas based auto-segmentation compared to gold standard manual segmentation. Material and methods Heart and cardiac substructures were manually delineated on 54 breast cancer patients. Twenty-seven patients were used to build the auto-segmentation atlas, the other 27 to validate performance. We evaluated accuracy of the auto-segmented contours with standard geometric indices and assessed dosimetric endpoints. Results Auto-segmented contours overlapped geometrically with manual contours of the heart and chambers with Dice-similarity coefficients of 0.93 ± 0.02 (mean ± standard deviation) and 0.79 ± 0.07 respectively. Similarly, there was a strong link between dosimetric parameters derived from auto-segmented and manual contours (R 2 = 0.955–1.000). On the other hand, the left anterior descending artery had little geometric overlap (Dice-similarity coefficient 0.09 ± 0.07), though acceptable representation of dosimetric parameters (R 2 = 0.646–0.992). Conclusions The atlas based auto-segmentation approach delineates heart structures with sufficient accuracy for research purposes. Our results indicate that quality of auto-segmented contours cannot be determined by geometric values only. [ABSTRACT FROM AUTHOR]

Background To test the hypothesis that atlas-based active bone marrow (ABM)-sparing intensity modulated radiation therapy (IMRT) yields similar dosimetric results compared to custom ABM-sparing IMRT for cervical cancer patients. Methods We sampled 62 cervical cancer patients with pre-treatment FDG-PET/CT in training ( n = 32) or test ( n = 30) sets. ABM was defined as the subvolume of the pelvic bone marrow (PBM) with standardized uptake value (SUV) above the mean on the average FDG-PET image (ABM Atlas ) vs. the individual’s PET (ABM Custom ). Both were deformed to the planning CT. Overlap between the two subvolumes was measured using the Dice coefficient. Three IMRT plans designed to spare PBM, ABM Atlas , or ABM Custom were compared for 30 test patients. Dosimetric parameters were used to evaluate plan quality. Results ABM Atlas and ABM Custom volumes were not significantly different ( p = 0.90), with a mean Dice coefficient of 0.75, indicating good agreement. Compared to IMRT plans designed to spare PBM and ABM Custom , ABM Atlas -sparing IMRT plans achieved excellent target coverage and normal tissue sparing, without reducing dose to ABM Custom (mean ABM Custom dose 29.4 Gy vs. 27.1 Gy vs. 26.9 Gy, respectively; p = 0.10); however, PTV coverage and bowel sparing were slightly reduced. Conclusions Atlas-based ABM sparing IMRT is clinically feasible and may obviate the need for customized ABM-sparing as a strategy to reduce hematologic toxicity. [ABSTRACT FROM AUTHOR]