Affiliations: Nuclear Engineering, Missouri University of Science
and Technology, Rolla, MO, USA
Note: [] Corresponding author: Xin Liu, Nuclear Engineering, Missouri
University of Science and Technology, 301 W14th Street Rolla, MO 65401, USA.
Tel.: +1 573 341 4693; Fax: +1 573 341 4720; E-mail: [email protected]
Abstract: BACKGROUND: While spectral CT using single photon counting detector
has shown a number of advantages in diagnostic imaging, knowledge of the
detector response function of an energy-resolved detector is needed to correct
the signal bias and reconstruct the image more accurately. OBJECTIVE: The objective of this paper is to study the photo
counting detector response function using laboratory sources, and investigate
the signal bias correction method. METHODS: Our approach is to model the detector response function
over the entire diagnostic energy range (20 keV <E< 140 keV) using a
semi-analytical method with 12 parameters. The model includes a primary photo
peak, an exponential tail, and four escape peaks. Four radioactive isotopes
including Cdmium-109, Barium-133, Americium-241 and Cobalt-57 are used to
generate the detector response function at six photon energies. The 12
parameters are obtained by non-linear least-square fitting with the measured
detector response functions at the six energies. The correlations of the 12
parameters with energy are also investigated with the measured data. RESULTS: The analytical model generally describes the detector
response function and is in good agreement with the measured data. The trend
lines of the 12 parameters indicate higher energies tend to cause grater
spectrum distortion. The spectrum distortion caused by the detector response
function on spectral CT reconstruction is analyzed theoretically, and a
solution to correct this spectrum distortion is also proposed. CONCLUSION: In spectral and fluorescence CT, the spectrum distortion
caused by detector response function poses a problem and cannot be ignored in
any quantitative analysis. The detector response function of a CdTe detector
can be obtained by a semi-analytical method.
