Comparison of one vs two CTs for attenuation correction of both rest and stress SPECT data for myocardial perfusion imaging

Objectives To investigate whether radiation exposure could be minimized for patients undergoing nuclear myocardial perfusion imaging (MPI) by using only a single CT for attenuation correction (AC) vs. the standard acquisition of a CT for both rest and stress.

Methods 30 patients received a 1 day rest(R)/stress (S) MPI on 1 of 3 SPECT/CT scanners with CT at both R and S. Both R-CT & S-CT were used for AC of R & S MPI to produce 3 MPI R/S study sets: Category1, the standard with R-CT AC for R-MPI & S-CT AC for S-MPI; category 2, using R-CT AC for both S-MPI & R-MPI; category 3, using S-CT AC for both S-MPI & R-MPI. All MPI were analysed by 4D-MSPECT (SMS v4.2) to produce sum difference scores (SDS) between R & S MPI. Regression analysis was used to compare the difference between SDS of categories 1 & 2, and 1 & 3. A SDS of 4 was considered significant when analyzing single pts. 15 pts had normal & 15 pts had abnormal MPI.

Results Regression analysis did not show a significant differences between the SDS of categories 1 & 3 (y = 1.0x + 0.094; R = 0.97). For none of the 30 individual pts, comparison of SDS scores between category 1 & 3 did not differ by >3. Conversely, there were significant differences between category 1 & 2 SDS (y = 0.85x + 0.62, R=0.85, p<0.01). Additionally, for 6 of 30 pts (20%), individual pt comparison between category 1 & 2 SDS differed by >3.

Conclusions These results show that a single CT obtained during S-MPI may be used for attenuation correction of both R/S MPI without producing significant differences in SDS, thereby reducing exposure to ionizing radiation. Utilization of R-CT for attenuation correction of the S/R MPI may lead to significant differences in SDS