C Lee¹*, S Streitmatter², J Shin³, (1) National Cancer Institute, Bethesda, MD, (2) University of Utah Hospitals, Salt Lake City, UT, (3) National Cancer Institute, Bethesda, MD

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  C Lee

SU-K-201-5 (Sunday, 7/10/2022) 5:00 PM - 6:00 PM [Eastern Time (GMT-4)]

Room 201

Purpose: Although advances in medical imaging have had a substantial impact on medical practice, it is critical to accurately estimate and monitor the radiation doses of patients undergoing radiologic imaging procedures to avoid potential long-term adverse health effects. We report the updates to an existing organ dose calculator, National Cancer Institute dosimetry system for Radiography and Fluoroscopy (NCIRF): the new phantoms with the arms raised and lowered for realistic simulation of the arm structure in radiology exams and multithreading capability for faster dose calculation.

Methods: We created two libraries of pediatric and adult computational phantoms with the arms raised and lowered and replaced the existing arm-removed phantoms in NCIRF 1.0 with them. We then evaluated the impact of the arms in lateral projection exams on major organ doses. Next, we embedded the GEANT4 libraries compiled for multithreading into NCIRF to speed up dose calculations. We simulated illustrative cardiac catheterization fluoroscopy of an adult male patient to evaluate the calculation time for 1e8 histories using different thread numbers and the Monte Carlo errors to the heart, lungs, and thyroid for different particle histories.

Results: With the arms raised, the dose to the lungs and active marrow was about 30% greater and 10% smaller, respectively, than those from the phantoms with the arms lowered in lateral projection exams. In an illustrative cardiac catheterization fluoroscopy procedure, the calculation time decreased by 1/4 when the number of threads increased from 1 to 3. A particle history of 1e6 was required to reduce the Monte Carlo errors for the heart and lungs to less than 1%.

Conclusion: We upgraded NCIRF by implementing two phantom libraries to more accurately simulate a patient's arm posture in radiology exams. The multithreading feature should be useful to reach reasonable statistical errors on personal computers without parallel computing capability.

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