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Using Associated Particle Imaging and Time-Of-Flight Spectroscopy for Eliminating Tomographic Imaging for NSECT: A Simulation Study

A Price

A Price1*, W Harris1 , A Kapadia1,2 (1) Medical Physics Graduate Program, Duke University, Durham, NC (2) Department of Radiology, Duke University Medical Center, Durham, NC


TH-AB-204-6 (Thursday, July 16, 2015) 7:30 AM - 9:30 AM Room: 204

Purpose:To evaluate feasibility of associated particle time-of-flight (AP-TOF) neutron imaging with a fan beam source using simulations in GEANT4 and determine its effect on improving scan time in Neutron Stimulated Emission Computed Tomography (NSECT). Previous NSECT experiments have used a pencil-beam, raster-scanned through the entire volume of interest with long scan durations. A fan beam could reduce the scan duration substantially, improving the clinical feasibility of the technique.

Methods:A simulation of fast-neutron AP-TOF NSECT was developed in GEANT4. Fast neutrons that undergo inelastic scattering with elemental nuclei in the phantom lead to prompt gamma emission with energy specific to the emitting element used to identify the emitting elements. In the simulation, a 2-degree wide fan beam of 5 MeV neutrons was swept across a prone water breast phantom containing a cancerous lesion. For each neutron emitted, an alpha particle was coincidently emitted in the opposite direction and was used to determine the neutron’s flight path. The neutron’s time of flight was used to determine the depth of interaction along the flight path. Images were reconstructed for each element in the breast phantom to assess location accuracy with AP-TOF imaging.

Results:Images reconstructed from H and Fe showed strong agreement with the locations and geometry of the breast (H-2224 keV) and lesion (Fe-847 keV), with <3% error between the measured and actual locations. Uncertainties in the lateral and axial (i.e., along the beam) directions were determined to arise from uncertainty in the source aperture opening when determining alpha particle location (lateral: 1-2cm) and gamma detection time (axial: 1-2ns).

Conclusion:AP-TOF neutron imaging with a pseudo-fan beam is capable of generating clinically relevant images of biological objects without the need for tomographic rotation. With appropriate detection hardware, the ability to eliminate tomographic rotation could reduce NSECT acquisition time by a factor of 8-10.

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