An evaluation of the effect of scatter and attenuation correction of gamma photons on the reconstructed radionuclide distribution in the myocardial wall during spect imaging
Loading...
Date
2000-11
Authors
Mdletshe, Nhlakanipho
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
The purpose of this study was firstly to evaluate the selection of reconstruction
parameters (i.e. the number of subsets and the number of iterations) based on phantom
studies. The second aim was to evaluate the effect of the non-uniform attenuation and
scatter correction on myocardial perfusion studies performed on healthy volunteers as
well as patients with proven inferior wall perfusion defects.
The quality of the images from the phantom studies showed that 16 subsets with 2
iterations gave the best results if considering image noise and image resolution. These
number of subsets and iterations were therefore used as reconstruction parameters in
the patient studies
The application of an attenuation correction to the emission data required that
attenuation coefficient maps of the subjects were obtained from transmission images.
I39Ce was chosen as the transmission source and used in conjunction with 99mTcas the
emission source. The emission data were corrected for scatter according to the triple
energy window method. In the healthy male and female volunteers, the attenuation and scatter corrected
myocardial SPECT images showed an improvement in the homogeneity of the counts
distribution compared to the uncorrected images. The counts distribution in the
inferior region improved after the attenuation correction was applied, however it
exceeded the counts in the anterior region. After applying a scatter as well as an
attenuation correction to the emission data, the counts in the inferior region of the
myocardium were slightly reduced. This was a result of the scatter correction eliminating scattered counts in the inferior region originating mainly from the liver.
The apparent lower counts in the anterior region could be a result of too little
compensation for scatter in the inferior wall, and needs to be investigated further.
The defects in the three unhealthy patients, were not obscured after applying the
scatter and attenuation correction to the emission data. The correction technique did
not introduce false negative results in these patients.
The application of scatter and attenuation correction techniques shows promising
results for the interpretation of myocardial perfusion studies. These correction
algorithms however need to be investigated thoroughly before being used in the
routine clinical practice to avoid the introduction of artefacts.
Description
Keywords
SPECT, Nuclear cardiology, Attenuation correction, Scatter correction, Transmission imaging;, Scanning line source, Iterative reconstruction;, Myocardial perfusion, Coronary artery disease, 99rnTcMISI, Diagnostic imaging, Tomography, Emission -- Quality control, Dissertation (M.Med.Sc. (Medical Physics))--University of the Free State, 2000