Abstract
Objective:Prone positioning, iterative reconstruction (IR-OSEM) and electrocardiography (ECG) gating have been demonstrated to improve the specificity of myocardial perfusion SPECT (MPS) in the diagnosis of coronary artery disease.Methods:The gated supine and prone MPS images of 45 patients were reconstructed with both IR-OSEM [supine (SIR) and prone (PIR)] FBPs [supine (SFBP), prone (PFBP)] for comparison. Perfusion, wall motion (WM) and wall thickening were also interpreted semi-quantitatively. Two groups were generated as those with normal or abnormal findings. Segmental myocardial tracer uptake values were noted from four of the reconstructed images from 17 segment model of bullseye.Results:The difference between mean values and the standard deviations of the % tracer uptakes of inferior wall segments were statistically significant in all images. The normalcy rates were highest in PIR images, followed by PFBP and SIR images. The number of patients with any perfusion abnormality were 42, 12, 32, and 6, in SFBP, PFBP, SIR and PIR images, respectively. The six patients with perfusion abnormality in PIR images were re-evaluated with rest images and were diagnosed with a fixed perfusion defect. There was positive correlation between WM and either PFBP or PIR images. Sixteen patients’ WM were evaluated as abnormal while only 6 patients’ perfusions were abnormal in PIR.Conclusion:Prone imaging in addition to a supine perfusion SPECT improves imaging quality of the inferior wall, especially when reconstructed with iterative methods. If prone imaging can not be performed, ECG-gating can also be used as a beneficial method.
Highlights
Myocardial perfusion SPECT (MPS) imaging is accepted as the method of choice to evaluate coronary artery disease (CAD), tissue attenuation and reconstruction artifacts reduce the test’s specificity
In the anterior and septal wall segments the difference between PFBP and SIR in terms of % tracer uptakes was not significant similar to the apex, except segment 14 that indicates the septum in the short axis image of the apical section
Within the lateral wall segments, there were no differences between SFBP and SIR, PFB and PIR in terms of % tracer uptakes, except segment that indicates the lateral wall in the short axis image of the apical section and in segment that indicates the apex in only SFBP and SIR (p=0.404)
Summary
Myocardial perfusion SPECT (MPS) imaging is accepted as the method of choice to evaluate coronary artery disease (CAD), tissue attenuation and reconstruction artifacts reduce the test’s specificity. Intense sub-diaphragmatic activity in the neighborhood of the heart may produce artifacts [1,2] It can either mask a true perfusion defect [1,3], or cause false perfusion defects [3,4] due to filtered back projection (FBP) reconstruction that suppresses inferior wall counts adjacent to intense sub-diaphragmatic activity [5]. Various methods have been used to reduce artifacts in MPS, such as gated imaging and prone imaging. Prone imaging has been demonstrated to decrease inferior wall attenuation as well as improving the specificity rate [6,7]. Our primary aim in this study was to compare the effectiveness of the methods performed to increase the specificity of the exam [gatedprone scans and iterative reconstruction (IR)] especially on artifact correction
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