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Study On the CT Radiation Attenuation Characteristics of Human Body for Phantom Design Using Monte Carlo Simulations

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h liu

h liu1,2*, Y Gao2, W Zhuo1, J Wu1, X Xu2, (1) Institute of radiation medicine, Fudan University, Shanghai, Shanghai, (2)Rensselaer Polytechnic Inst., Troy, NY

SU-E-I-41 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: The CTDI values measured with standard PMMA phantoms were now being challenged due to the clinical application of new technologies such as automatic tube current modulation(TCM), the aim of this study is to simulate the CT radiation attenuation characteristics of human body along Z-axis which were the basic data of developing new phantoms used to evaluate TCM.

Methods:The CT model used in this study has been modeled including the source energy spectrum, the bow-tie filter as well and the beam shape. The voxel phantoms RPI Adult Male designed to match the ICRP anatomical references for average individuals were also selected in this study. MCNPX 2.5.0 was used to simulate the 120 kVp CT X-ray attenuation of voxel phantom along the z-axis. Averaged photon flux was tallied before and after it passed though the phantom separately, simulations were also carried out using different thickness of PMMA plates instead of the voxel phantom.

Results:The CT X-ray attenuation of PMMA and its thickness presents a significant negative exponential relationship with the r2=0.9975. The CT X-ray attenuation data of every 2cm along Z-axis direction of voxel phantom were obtained, combined with characteristics of CT X-ray attenuation of PMMA, the PMMA equivalent thickness of the voxel phantom torso along the Z-axis direction in terms of CT X-ray attenuation were calculated. The PMMA equivalent thickness ranges from 5.5cm to 30.1cm. The liver and spleen plane, which contents substantive organs such as the liver and spleen, and bone structure as ribs and the lumbar, was the maximum attenuation plane.

Conclusion:The trend of the overall attenuation characteristics of the human body in terms of CT X-ray was in accord with the anatomical structure, these results could be used to develop new dose phantoms which were used to evaluate automatic tube current modulation with further study.

Funding Support, Disclosures, and Conflict of Interest: This project was partially funded by National Institutes of Health (National Library of Medicine R01LM009362 and National Institute of Biomedical Imaging and Bioengineering R42EB010404)

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