Digital phantom versus individualized radiation dosimetry in CT examination protocols of children and adults.

The aim of this study was to compare the organ doses estimated through individual model-based and digital phantom-based Monte Carlo (MC) methods in radiation treatment plan oriented CT examination protocols. Methods. Six physical anthropomorphic phantoms that simulate the average pediatric individual as a neonate, 1-year-old, 5-year-old, 10-year-old child and the average adult individual as a male and female adult were used. Organ dose was assessed using two MC-powered dosimetry tools. These were an individual model-based (ImpactMC, CT Imaging GmbH, Germany) and a digital phantom-based dosimetry tool (NCICT, National Cancer Institute, USA). Normalized to volume CT dose index (CTDIvol) organ dose (nOD) was assessed for primarily exposed radiosensitive organs using radiation treatment plan intended head, thorax and abdomen/pelvis CT examination protocols. nOD were compared to measurements performed using thermoluminescent detectors (TLDs) and the physical anthropomorphic phantoms. Results. The average percent differences of ImpactMC to TLD measurements across all organs and phantoms were 8%, 20% and 16% for head, thorax and abdomen/pelvis, respectively, whereas the corresponding differences of NCICT to TLD measurements were 64%, 48% and 34%. The differences between estimated and measured normalized organ dose values were higher in pediatric compared to adult phantoms. Conclusions. Compared to NCICT, organ doses estimated with ImpactMC were in closer agreement with TLD measurements. This is owing to the methodology employed by ImpactMC to create phantoms that mimic the anatomical characteristics of the examined patient. .