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MATHEMATICAL SIMULATIONS OF PHOTON INTERACTIONS USING MONTE CARLO ANALYSIS TO EVALUATE THE UNCERTAINTY ASSOCIATED WITH IN VIVO K X-RAY FLUORESCENCE MEASUREMENTS OF STABLE LEAD IN BONE

LODWICK, CAMILLE JANAE
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1059400723

Abstract Details

2003, PhD, University of Cincinnati, Engineering : Nuclear and Radiological Engineering.
This research utilized Monte Carlo N-Particle version 4C (MCNP4C) to simulate K X-ray fluorescent (K XRF) measurements of stable lead in bone. Simulations were performed to investigate the effects that overlying tissue thickness, bone-calcium content, and shape of the calibration standard have on detector response in XRF measurements at the human tibia. Additional simulations of a knee phantom considered uncertainty associated with rotation about the patella during XRF measurements. Simulations tallied the distribution of energy deposited in a high-purity germanium detector originating from collimated 88 keV 109 Cd photons in backscatter geometry. Benchmark measurements were performed on simple and anthropometric XRF calibration phantoms of the human leg and knee developed at the University of Cincinnati with materials proven to exhibit radiological characteristics equivalent to human tissue and bone. Initial benchmark comparisons revealed that MCNP4C limits coherent scatter of photons to six inverse angstroms of momentum transfer and a Modified MCNP4C was developed to circumvent the limitation. Subsequent benchmark measurements demonstrated that Modified MCNP4C adequately models photon interactions associated with in vivo K XRF of lead in bone. Further simulations of a simple leg geometry possessing tissue thicknesses from 0 to 10 mm revealed increasing overlying tissue thickness from 5 to 10 mm reduced predicted lead concentrations an average 1.15% per 1 mm increase in tissue thickness (p<0.0001). An anthropometric leg phantom was mathematically defined in MCNP to more accurately reflect the human form. A simulated one percent increase in calcium content (by mass) of the anthropometric leg phantom’s cortical bone demonstrated to significantly reduce the K XRF normalized ratio by 4.5% (p<0.0001). Comparison of the simple and anthropometric calibration phantoms also suggested that cylindrical calibration standards can underestimate lead content of a human leg up to 4%. The patellar bone structure in which the fluorescent photons originate was found to vary dramatically with measurement angle. The relative contribution of lead signal from the patella declined from 65% to 27% when rotated 30°. However, rotation of the source-detector about the patella from 0 to 45° demonstrated no significant effect on the net K XRF response at the knee.
Dr. Henry B. Spitz (Advisor)
147 p.
x-ray fluorescence; Monte Carl simulations; lead exposure

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Citations

  • LODWICK, C. J. (2003). MATHEMATICAL SIMULATIONS OF PHOTON INTERACTIONS USING MONTE CARLO ANALYSIS TO EVALUATE THE UNCERTAINTY ASSOCIATED WITH IN VIVO K X-RAY FLUORESCENCE MEASUREMENTS OF STABLE LEAD IN BONE [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1059400723

    APA Style (7th edition)

  • LODWICK, CAMILLE. MATHEMATICAL SIMULATIONS OF PHOTON INTERACTIONS USING MONTE CARLO ANALYSIS TO EVALUATE THE UNCERTAINTY ASSOCIATED WITH IN VIVO K X-RAY FLUORESCENCE MEASUREMENTS OF STABLE LEAD IN BONE. 2003. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1059400723.

    MLA Style (8th edition)

  • LODWICK, CAMILLE. "MATHEMATICAL SIMULATIONS OF PHOTON INTERACTIONS USING MONTE CARLO ANALYSIS TO EVALUATE THE UNCERTAINTY ASSOCIATED WITH IN VIVO K X-RAY FLUORESCENCE MEASUREMENTS OF STABLE LEAD IN BONE." Doctoral dissertation, University of Cincinnati, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1059400723

    Chicago Manual of Style (17th edition)

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© 2003, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.