Dosimetric results of whole body irradiation with MOSFET dose tracking to eliminate interfractional variations

Total body irradiation (TBI) is an essential component of conditioning regimens prior to hematopoietic stem cell transplantation (HSCT), particularly in paediatric patients. However, achieving dose homogeneity throughout the treatment course remains a major challenge due to large treatment fields, tissue heterogeneity, and inter-fraction variations. The aim of this study was to investigate the feasibility and impact on dose homogeneity of fraction-based adaptive dose modulation supported by dynamically adjusted rice bag compensators, based on real time metal oxide semiconductor field-effect transistor (MOSFET) feedback, using in vivo dosimetry (IVD) in bilateral TBI. In this context, IVD measurements were performed using MOSFET detectors at the brain, neck, lung, umbilical, and pelvic regions during each treatment fraction in patients undergoing bilateral TBI. Based on these measurements, the thickness of the rice-bag compensators was dynamically adjusted between fractions. Calculated dose values were compared with MOSFET measured doses for each anatomical region. Statistical analysis revealed no significant differences between calculated and MOSFET-measured doses across all anatomical regions (p > 0.05), indicating a high level of agreement between planned and delivered doses. The highest dose differences were observed in the lung region (up to 106.9%), whereas the lowest differences were observed in the neck region (up to 100.8%). In conclusion, fraction-based IVD monitoring using MOSFET dosimetry enables adaptive dose modulation in bilateral TBI, reduces inter-fraction dosimetric uncertainties, and provides an effective quality assurance strategy to improve dose homogeneity and treatment safety, particularly in paediatric patients.