Development and validation of an age-scalable cardiac model with substructures for dosimetry in late-effects studies of childhood cancer survivors

Abstract

Background and Purpose: Radiation therapy is a risk factor for late cardiac disease in childhood cancer survivors. Several pediatric cohort studies have established whole heart dose and dose–volume response models. Emerging data suggest that dose to cardiac substructures may be more predictive than whole heart metrics. In order to develop substructure dose-response models, the heart model previously used for pediatric cohort dosimetry needed enhancement and substructure delineation. Methods: To enhance our heart model, we combined the age-scalable capability of our computational phantom with the anatomically-delineated (with substructures) heart models from an international humanoid phantom series. We examined cardiac volume similarity/overlap between registered age-scaled phantoms (1, 5, 10, and 15 years) with the enhanced heart model and the reference phantoms of the same age; dice similarity coefficient (DSC) and overlap coefficient (OC) were calculated for each matched pair. To assess the accuracy of our enhanced heart model, we compared doses from computed tomography-based planning (ground truth) with reconstructed heart doses. We also compared doses calculated with the prior and enhanced heart models for a cohort of nearly 5000 childhood cancer survivors. Results: We developed a realistic cardiac model with 14-substructures, scalable across a broad age range (1–15 years); average DSC and OC were 0.84 ± 0.05 and 0.90 ± 0.05, respectively. The average percent difference between reconstructed and ground truth mean heart doses was 4.2%. In the cohort dosimetry analysis, dose and dose-volume metrics were approximately 10% lower on average when the enhanced heart model was used for dose reconstructions. Conclusion: We successfully developed and validated an anatomically realistic age-scalable cardiac model that can be used to establish substructure dose-response models for late cardiac disease in childhood cancer survivor cohorts.

Radiation therapy related cardiac disease risk in childhood cancer survivors: Updated dosimetry analysis from the Childhood Cancer Survivor Study

“…Specifically, the systematic underestimation of dose for chest-directed radiation therapy was due to our H Atlas model being laterally smaller compared to the anatomically more realistic H Hybrid model. In future, any new organs that are added to our phantom will be developed following the H Hybrid model development methodology [ 10 ], i.e., organ models will be developed using 3D anatomy, e.g., reference phantoms or patients’ anatomies.…”

“…We previously reported RT-related late cardiac disease risk in the CCSS using H Atlas [ 4 ]. Here, we recomputed the heart doses for the CCSS cohort using the same age-scaled computational phantom, but with an updated CT-based anatomically realistic and validated heart model (H Hybrid ) [ 10 ]. For comparison H Atlas and H Hybrid are illustrated in Supplementary Fig.…”

“…1 . Our general methodology for RT record abstraction, dose reconstruction [ 9 , 11 , 12 ], and heart dose calculations [ 10 ], which include dose from direct and stray radiation, has been described elsewhere. To study the impact of updated cardiac model on RT-dosimetry, differences in D m , V 5 and V 20 were calculated for each individual in the CCSS cohort who received RT.…”

“…The cardiac model (H Atlas ) in our computational phantom at the time of that study was based on manual translation of the size, shape, and placement of the heart from a cross-sectional anatomy atlas to our phantom [ 8 , 9 ]. Recently, we developed an enhanced high-resolution CT-based anatomically realistic age-scalable cardiac model (H Hybrid ) [ 10 ]. We previously demonstrated that our enhanced cardiac model is valid from infant to adolescent (and superior to H Atlas ) when compared to the gold standard CT based voxelized pediatric phantoms [ 10 ].…”

“…Recently, we developed an enhanced high-resolution CT-based anatomically realistic age-scalable cardiac model (H Hybrid ) [ 10 ]. We previously demonstrated that our enhanced cardiac model is valid from infant to adolescent (and superior to H Atlas ) when compared to the gold standard CT based voxelized pediatric phantoms [ 10 ]. The purpose of this study was to update our previously reported RT-related late cardiac disease risk for the CCSS using doses calculated with the enhanced heart model, H Hybrid (as opposed to H Atlas ).…”