Single CT for attenuation correction of rest/stress cardiac SPECT perfusion imaging.

Common practice is to use separate CT scans acquired during rest and stress for attenuation correction of SPECT myocardial perfusion imaging (MPI). We evaluated using a single CT scan to correct both rest and stress SPECT scans. Studies from 154 patients were reprocessed using one CT acquired at stress to correct both rest and stress scans (1CT) and compared to correction of each scan with its own CT (2CT). Two expert readers independently read the images and determined summed stress (SSS), rest (SRS), and difference (SDS) scores. The correlation in SRS between 2CT and 1CT was r ≥ 0.88. The concordance in SDS was ≥0.84 (kappa ≥ 0.62). The mean SDS difference between 2CT and 1CT for the averaged observer was not significantly different from zero (p > 0.31). 1CT images had a small but significant increase in SRS and an increase in SDS variability. However, the mean SDS difference was similar to the mean inter-observer SDS difference for the 2CT approach (-0.08 vs -0.23, p = 0.46) and had less uncertainty (1.02 vs 2.05, p < 0.001). Thus, the differences between 1CT and 2CT are unlikely to be clinically significant, and the 1CT approach is feasible for SPECT MPI.

Scatter correction improves concordance in SPECT MPI with a dedicated cardiac SPECT solid-state camera.

PURPOSE: Correction for photon attenuation and scatter improves image quality with conventional NaI-based gamma cameras but evaluation of these corrections for novel solid-state dedicated cardiac cameras is limited. In this study, we assess the accuracy of dual-energy-window (DEW) scatter correction (SC) applied to clinically acquired (99m)Tc-tetrofosmin myocardial perfusion images obtained on a dedicated multi-pinhole camera with cadmium-zinc-telluride (CZT) detectors (GE Discovery NM530) compared to DEW scatter-corrected images from our conventional SPECT camera (GE Infinia Hawkeye 4; INF). METHODS: A modified DEW SC method was formulated to account for the detection of primary photons in the lower energy window (120 keV ± 5%) with CZT detectors, in addition to estimating the scattered photons detected in the photopeak window (140 keV ± 10%). Phantom experiments were used to estimate the DEW correction parameters. Data from 108 patients, acquired using a standard rest/stress Tc-99m-tetrofosmin SPECT/CT protocol on both cameras, were reconstructed with no correction (NC), attenuation correction (AC), and AC with DEW-SC. Images were compared based on the summed stress/rest/difference scores (SSS/SRS/SDS) calculated by clinical software. RESULTS: The correlation between SSS/SRS for the two cameras was excellent (r ≥ 0.94). The mean difference between cameras was <0.4 for SSS/SRS/SDS scores. Since datasets did not follow a normal distribution, non-parametric tests were used to show significant differences between datasets. Classification of disease (SSS) was highly correlated, as ranked by the two cameras (kendall's tau = 0.72, P < .001). AC significantly reduced the mean difference between the two cameras for SSS/SRS compared to NC. AC without SC on the CZT introduced a bias towards higher scores when compared to the INF, which was reduced after applying SC. Although SC increased noise, the scores for the AC/SC images were not significantly different between the two cameras (P > .1). CONCLUSIONS: DEW-SC on the CZT camera was feasible and produced images that are not significantly different from those acquired on the INF camera. Although use of SC on CZT images does increase noise, the resultant noise does not introduce bias relative to the INF camera.

Comparing slow- versus high-speed CT for attenuation correction of cardiac SPECT perfusion studies.

BACKGROUND: For SPECT, CT-based attenuation correction is preferred. Many different models of CT are available with SPECT/CT systems. Our study compares clinical cardiac SPECT images that were attenuation corrected using slow-rotation CT and high-speed CT transmission scans. METHODS: We evaluated 59 rest/stress perfusion studies from patients who had undergone both a SPECT/CT with a slow-rotation CT and a perfusion study on a PET/CT camera equipped with a high-speed CT scanner. Each SPECT study was reconstructed with transmission maps from both CT scans and the relative perfusion was assessed using semi-automated software. The summed stress/rest/and difference scores (SSS/SRS/SDS) were compared as well as the test classification. RESULTS: The intraclass correlation coefficients for the SSS, SRS, and SDS were 0.97, 0.96, and 0.80 respectively. There were no significant differences in the mean SSS, SRS, or SDS with the use of either CT for attenuation corrections. Classifying SSS > 3 as abnormal, there was 97% concordance (κ = 0.88). Classifying SDS > 1 as abnormal, there was 95% concordance (κ = 0.54). A McNemar's test showed no significant differences. CONCLUSIONS: There were no significant differences between using a high-speed CT and using a slow-rotation CT for attenuation correction of SPECT myocardial perfusion images.