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Monte Carlo Model of a Prototype 2D Detector Array for Fast Backscatter X-Ray Imaging (BSX)

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L Rolison

L Rolison*, K Jordan , J Baciak , S Samant , University of Florida, Gainesville, FL


TH-AB-708-7 (Thursday, August 3, 2017) 7:30 AM - 9:30 AM Room: 708

Purpose: To use Monte Carlo N-Particle (MCNP) to design a mobile, field-deployable, prototype backscatter imaging system that utilizes 2D detector array, enabling x-ray imaging for scenarios where transmitted radiography is not permissible.

Methods: Backscatter x-ray imaging (BSX) provides an alternative to conventional computed tomography (CT) and projective digital radiography (DR). It employs detectors located on the same side as the incident photon source, making use of backscatter and avoiding ring geometry to enclose the imaging object. Prior investigations of BSX systems utilized x-ray pencil beams surrounded by individual detectors. Though image resolution is easier to control with such a design, it is inherently slow due to the need to raster scan across an object. A new design is investigated that utilizes 2D pixelated detector arrays, combined with collimators and fan beam source, that enables faster image acquisition. A Python code package was developed, enabling fast system design and MCNP modeling, to investigate system capabilities through simulation.

Results: Optimization parameters included x-ray energy, detector pixel dimensions, fan beam specifications, and collimation length, allowing for rapid exploration of parameter space. A test phantom was imaged in MCNP using a partially optimized system to demonstrate design feasibility. The system consisted of 6x40 grid of detector pixels, each 2.5x1mm in dimension. A tungsten collimation grid was placed over the detector, with a thickness of 0.4mm and 15mm in length. Image resolution was 2mm in the cross-sectional plane and 20mm in depth direction.

Conclusion: Python/MCNP package was developed to prototype new BSX imager as part of a project to build field-deployable, x-ray imager where transmission imaging is not permissible. Initial images show feasibility for such design to acquire 2D radiographs (2mm resolution), with the possibility for 3D (or at least depth sensitive) imaging for situations where the patient must be medically assessed before moving.

Funding Support, Disclosures, and Conflict of Interest: This material is based upon work supported under an Integrated University Program Graduate Fellowship.

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