Euromedim 2006 :1st European Conference on Molecular Imaging Technology

Gamma-ray Tracking Method Using a Digital Pulse Shape Analysis for Improving the Imaging Sensitivity of a Compton Camera

9 May 2006, 14:00

1h

Palais du Pharo, Marseille

poster • System simulation, design and implementation Poster Session :Simulation, Modeling, Reconstruction

Speaker

Mr Nam Young Kim (Department of Physics, Chung-Ang University, Seoul 156-756, Republic of Korea)

Description

A Compton camera has excellent imaging and spectroscopic characteristics which can fulfill the requirements in various fields such as biomedical research, nuclear medicine, astrophysics, and national security. Especially its high imaging sensitivity is the most fascinating aspect to nuclear medical imaging fields. According to our previous works related to the performance of a proof-of-principle Compton camera based on a double-sided silicon strip detector (DSSD) and a 25- segmented germanium detector (25-SEGD), however, the imaging sensitivity was not sufficient to our expectation. The primary factor which makes it difficult to achieve the high imaging sensitivity is the rejection of multi-site events that are fired for two or more electrodes of the detectors due to multiple scattering of gamma rays. In order to improve the imaging sensitivity of our Compton camera by accepting the multi-site events in the image reconstruction, we have investigated a gamma-ray tracking method using a digital pulse shape analysis for the 25-SEGD. The method is to determine the most probable scattering sequence restricted by the Compton- scattering kinematics considering the interaction positions and energies for multi- site events. The interaction position and the energy of each scattering are determined by fitting a measured pulse shape with a calculated one by the weighting field method. We performed the test of our gamma-ray tracking method with a 137Cs (662 keV) standard gamma-ray source which was collimated by a lead block. The collimated gamma ray was incident on the center segment of the 25-SEGD. Pulse shapes of the central and three adjacent segments were measured by the DGF-4C pulse analyzer, manufactured by XIA. Experimental results will be compared to the Monte Carlo simulation. Contribution of the multi-site events to the improvement of the imaging sensitivity will be discussed.