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

[摘要] The purpose of this study was firstly to evaluate the selection of reconstructionparameters (i.e. the number of subsets and the number of iterations) based on phantomstudies. The second aim was to evaluate the effect of the non-uniform attenuation andscatter correction on myocardial perfusion studies performed on healthy volunteers aswell as patients with proven inferior wall perfusion defects.The quality of the images from the phantom studies showed that 16 subsets with 2iterations gave the best results if considering image noise and image resolution. Thesenumber of subsets and iterations were therefore used as reconstruction parameters inthe patient studiesThe application of an attenuation correction to the emission data required thatattenuation coefficient maps of the subjects were obtained from transmission images.I39Ce was chosen as the transmission source and used in conjunction with 99mTcas theemission source. The emission data were corrected for scatter according to the tripleenergy window method. In the healthy male and female volunteers, the attenuation and scatter correctedmyocardial SPECT images showed an improvement in the homogeneity of the countsdistribution compared to the uncorrected images. The counts distribution in theinferior region improved after the attenuation correction was applied, however itexceeded the counts in the anterior region. After applying a scatter as well as anattenuation correction to the emission data, the counts in the inferior region of themyocardium 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 littlecompensation for scatter in the inferior wall, and needs to be investigated further.The defects in the three unhealthy patients, were not obscured after applying thescatter and attenuation correction to the emission data. The correction technique didnot introduce false negative results in these patients.The application of scatter and attenuation correction techniques shows promisingresults for the interpretation of myocardial perfusion studies. These correctionalgorithms however need to be investigated thoroughly before being used in theroutine clinical practice to avoid the introduction of artefacts.

[发布机构] University of the Free State

[效力级别] ","Scanning line source","Iterative reconstruction