Speaker
Mr
Nam Young Kim
(Chung-Ang University)
Description
We are currently developing a Compton camera for applications in nuclear medical
and molecular imaging. A Compton camera uses two sets of radiation detectors for
which incident gamma rays are Compton-scattered in the first detector and the
scattered gamma rays are then fully stopped via the photoelectric effect in the
second detector. Interaction points in both detectors provide the scattered gamma-
ray direction. According to Compton-scattering kinematics, a gamma-ray source can
be fixed to a surface of a cone with an apex at the interaction point in the first
detector, an opening Compton-scattering angle and an axis along the scattered gamma-
ray track. The intersections of such cones are defined to be the three-dimensional
distribution of the gamma-ray source.
Our Compton camera consists of a double-sided silicon strip detector (DSSD) as a
scatterer for the first detector and a 25-segmented germanium detector (25-SEGD) as
an absorber for the second detector. The DSSD, operated at the room temperature,
was a planar-type, high-purity, n-type silicon with active areas of 5 cm x 5 cm and
thicknesses of 1.5 mm, consisting of 16 x 16 orthogonal strips on both faces. The
25-SEGD was a planar-type, high-purity, p-type germanium crystal with dimensions of
5 cm x 5 cm x 2 cm. It was segmented into twenty-five segments on the front face of
a germanium crystal. Each segment, with areal dimensions of 1 cm x 1 cm, acts as an
individual gamma-ray detector. The unsegmented electrode on the rear face provided
energy spectra with better energy resolutions.
In order to improve the energy resolution of scatterer, we have developed a
prototype 32-channel preamplifier module for the low-noise performance of the DSSD.
The energy uncertainty of the recoiled electron in the DSSD is attributed to the
energy resolution of a detector which affects not only the resolution of the
Compton scattering angle but also the threshold setting for background rejection.
Performance of the DSSD was tested with 241Am (60 keV), 133Ba (356 keV) and 137Cs
(662 keV) standard gamma-ray sources in a self-triggering mode and also in
coincidence with the 25-SEGD. Gamma-ray images reconstructed by a simple back
projection method will be presented.
Author
Mr
Nam Young Kim
(Chung-Ang University)
Co-authors
Prof.
Chun Sik Lee
(Chung-Ang University)
Mr
Ju Hahn Lee
(Chung-Ang University)