Room: Room 202
Purpose: To develop a graphical user interface-based calculation tool to effectively estimate organ dose for pediatric and adult patients with variable body sizes in CT exams and to evaluate its performance by comparing organ doses with ten CT patients
Methods: A comprehensive set of organ dose coefficients, which convert CTDIvol to organ dose, were established for a total of 351 pediatric and adult computational phantoms of various body sizes (BMI: 15 - 44 kg/m2). CT exams were simulated using a reference CT scanner model, previously validated by measurements, in a Monte Carlo code, MCNPX. A graphical user interface was developed to obtain the input data from a user and show resulting organ doses. To evaluate the performance of the program, we contoured the liver, left and right kidneys, spleen, pancreas, lungs, and skeleton on ten patient CT sets collected from the NIH Clinical Center under an IRB-exempt study protocol, and calculated patient-specific organ doses. We selected phantoms by matching the effective diameter of the ten patients and compared phantom-based dose with those of the patients.
Results: It took about two months to finish 400,000 MCNPX runs for the 351 phantoms by using high performance computers. Dose comparison of the liver, kidneys, spleen, and pancreas between the patients and the phantoms built in our program showed the average absolute differences of 13%, 18%, 24%, and 6%, respectively. We also found that using the reference size phantom (176 cm and 73 kg) instead of body size-dependent phantoms would underestimate the lowest BMI patient's dose and overestimate the highest BMI patient's dose by up to 15% and 86%, respectively.
Conclusion: We developed and evaluated a computer program, titled the National Cancer Institute dosimetry system for CT eXtended (NCICTX), that estimates body size-specific organ doses. NCICTX is available free of charge for research purposes.
Funding Support, Disclosures, and Conflict of Interest: This work was funded by the intramural program of the National Institutes of Health, National Cancer Institute, Division of Cancer Epidemiology and Genetics. The use of MATLAB within this abstract does not necessarily imply recommendation by the National Institutes of Health.