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Assessment of PCXMC for Epidemiological Studies: A Monte Carlo Simulation Study
D Borrego*, C Lee , National Cancer Institute, Rockville, MD
Presentations
SU-J-CAMPUS-IT-2 (Sunday, July 30, 2017) 4:00 PM - 5:00 PM Room: Imaging ePoster Theater
Purpose: A PC Program for X-ray Monte Carlo (PCXMC) was used to calculate organ doses to patients undergoing diagnostic x-ray examinations. The program allows for simplified modifications of the outer body. We evaluated body size-dependent organ doses from PCXMC by using newer methods which include more anatomically realistic models of the human anatomy with a variety of body sizes.
Methods: We simulated chest and abdominal x-ray projections for 78 computational phantoms with different combinations of height (125-180 cm) and weight (20-140 kg) using PCXMC version 2.0.1.4 and the Monte Carlo N-Particle eXtended transport code 2.7 (MCNPX). We adjusted height and weight of the built-in stylized phantoms in PCXMC. In MCNPX calculations, we used a library of body size-dependent hybrid phantoms coupled with the x-ray simulations. Equivalent spectra to standard radiation qualities were generated with the tungsten anode spectral model by interpolating polynomials (TASMIP) and per the theory of Birch and Marshal for use in MCNPX and PCXMC, respectively. We compared 13 organ doses to evaluate differences between the stylized phantoms used in PCXMC and our hybrid phantoms.
Results: No significant differences were observed between spectra generated from TASMIP when compared to PCXMC spectra. The ratio of mean dose across all organs for the PCXMC to hybrid phantoms for chest and abdominal projections was 1.2 and 2.5, respectively. For abdominal projections, this ratio strongly correlated with an increase in body-mass index of the phantom (r=0.74).
Conclusion: PCXMX, due to its ease of use, is often selected to support dosimetry in epidemiological studies; however, it uses simplified models of the human anatomy that fail to account for variations in body morphometry for increasing weight. We found that PCXMC overestimates organ doses for chest and abdominal x-ray examinations when compared to advanced dosimetry methods based on realistic body size-dependent computational phantoms.
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