Towards optimal collimator design for the Pixelated Emission Detector for RadiOisotopes (PEDRO) hybrid imaging system

Dr Chuong V. Nguyen (Monash Centre for Synchrotron Science (MCSS))

CSIRO ICT

DATE: 2011-02-23
TIME: 14:00:00 - 15:00:00
LOCATION: Seminar Room S206 CSIRO ICTC Building 108
CONTACT: JavaScript must be enabled to display this email address.

ABSTRACT:
The Pixelated Emission Detector for RadiOisotopes (PEDRO) is a hybrid imaging system designed for the measurement of single photon emission from small animal models. The proof-of-principle device consists of a Compton-camera situated behind a mechanical collimator and is intended to provide optimal detection characteristics over a broad spectral range, from 30 keV to 511 keV. An automated routine has been developed for the optimisation of large-area slits in the outer regions of a collimator which has a central region allocated for pinholes. The optimisation technique allows the large-area slits to both sample fully and extend the primary field of view (FoV) determined by the pinholes. The slits were found to provide truncation of the back-projected cones of response and also an increase in the success rate of the interaction ordering algorithm. These factors resulted in an increase in the contrast and signal-to-noise ratio of the reconstructed image estimates. Of the two configurations tested, the cylindrical geometry outperformed the square geometry, primarily because of a decrease in artefacts. This was due to isotropic modulation of the cone surfaces, that can be achieved with a circular shape. Also, the cylindrical geometry provided increased sampling of the FoV due to more optimal positioning of the slits. The use of the cylindrical collimator and application of the transmission function in the reconstruction was found to improve the resolution of the system by a factor of 10, as compared to the uncollimated Compton camera.

BIO:
Dr Chuong V. Nguyen started working as a biomedical imaging researcher in the instrumentation group of the Monash Centre for Synchrotron Science (MCSS) in collaboration with CRC Biomedical Imaging Development from mid 2010. He obtained his PhD degree in Mechanical Engineering from Monash University, Clayton VIC, in 2010. Before entering Monash University, he obtained a Master's degree in Environmental Civil Engineering from Ritsumeikan University, Kyoto, in 2003 and a Bachelor's degree in Aeronautical Engineering from Ho Chi Minh City University of Technology in 2001. At MCSS, his research focus is nuclear imaging development, especially Single Photon Emission Tomography (SPECT). He has developed a new class of collimator designs optimised for a hybrid mechanical (pinhole) and electronic (Compton) collimation. The collimator development is aimed for a compact, high-resolution, high-sensitivity nuclear imaging system. He is currently working on Maximal Likelihood Expectation Maximisation (ML-EM) reconstruction and similar techniques for pinhole and truncated Compton reconstructions. The reconstructions are accelerated with Graphics Processing Units (GPU) using OpenCL. Dr Nguyen is an open-source advocate. He has been using open-source software tools for his research since 2005. From 2008, he actively contributed to open-source projects, including FreeMat and QDevelop.