Date(s) - 02/28/2014
Due to the rapid growth of computed tomography (CT) examinations in the United States, there is a need for accurate CT size-specific organ dosimetry that accounts for tube current modulation (TCM). Past studies validate the use of a slice-by-slice CT dosimetry methodology for the Toshiba Aquilion ONE scanner that can accurately account for TCM, and can be implemented for a multitude of exam types. Physical anthropomorphic phantom dosimetry data was used a basis to further validate this algorithm for different size reference phantoms. The average magnitude of percent error in the computed dose to all in-field organs of torso exams when compared to measured values was 8.5%. For head exams, the average magnitude in percent error of in-field organ doses was 6.9%. This methodology was then applied to The University of Florida’s Family of Reference Hybrid Phantoms across a wide range of clinically relevant scan protocols. This data provides age and gender-specific organ dose calculations that can be scaled by average effective mAs to calculate absolute organ dose. Additionally, dosimetric effective dose coefficients which have units of microsievert per milligray-centimeter were calculated for each phantom, as well as a reference dose coefficient. These coefficients, when applied to the physical phantom data show a relative error in effective dose of 16.0% and 12.0% for the phantom-specific and reference coefficients, respectively. Calculating effective dose using the millisievert per average effective mAs for each phantom yielded an average dosimetry error of 7.9%.