A Novel Associated Particle Neutron Elemental Imaging (APNEI) Technology for 3-D Noninvasive In Vivo Quantification of Trace Elements in Animal and Human Tissue

摘要

Trace elements play a crucial role in living organisms. The distribution of trace elements in these organisms provides valuable information about their biological function. In this project, a novel APNEI technology was studied for noninvasive quantification of trace elements in vivo at high 3-D resolution required for disease diagnose or metal toxicology research. The APNEI technology uses fast neutrons produced by a compact neutron generator to extract elemental information from an animal or a human tissue. The technology has two unique features: 1) the penetration of the neutrons and γ-rays to get into the animal or human tissue and to bring the elemental information out of the tissue; and 2) the associated particles to locate the position of the element. In this project, a deuterium-deuterium (D-D) APNEI model was built using Monte Carlo (MC) simulation method. MC simulations for the interaction between a D-D neutron source and a series of elements were performed. The resulting characteristic gamma-rays of interested elements were collected by high-purity germanium (HPGe) detectors simulated in the program. Assuming a 5 mm ~* 5 mm ~* 5 mm voxel in soft tissue (about 15 cm away from the neutron source) with iron (Fe) concentration of 1300 ppm, the Fe gamma-ray signals collected by the HPGe detectors is about 120 in 10 minutes with a radiation dose of 0.3 mSv to the irradiated tissue at neutron flux of 10~∧8 n/s. The number for phosphorus gamma-ray is about 60 counts for a 1 cm~∧3 voxel in soft tissue with P concentration of 500 ppm. These results show that the technology is sensitive enough to image some trace elements in animal or human tissue with image resolution of mm order at the biologically meaningful concentrations. This technology can be used to investigate metal exposure and alteration of the elemental distributions in animal or human body.