Objective To evaluate the impact of CT attenuation correction (CTAC) on intelligence quotient (IQ)-SPECT/CT and low energy high resolution (LEHR)- SPECT/CT myocardial perfusion imaging (MPI).

Methods Thirty-one patients (21 males and 10 females, aged 49.4 ± 12.01 years) with confirmed or suspected coronary heart disease were subjected to resting MPI from May 2018 to Octorber 2018 in the First Hospital of Shanxi Medical University. All patients were subjected to IQ-SPECT/CT+CTAC and LEHR-SPECT/CT+CTAC on the same day. The visual analysis and myocardial uptake of five myocardial segments (apical, anterior, lateral, inferior, and septal walls) were compared before and after IQ-SPECT/CT CTAC and after manual coordination, as well as before and after LEHR-SPECT/CT CTAC. Paired t test was used for comparison between the two groups. Chi-square test was used to compare the rate. Kappa test was used for consistency analysis.

Results (1) Visual analysis results were as follows. The IQ group was compared with the LEHR group without CTAC. Two nuclear medicine physicians were double blind and had high agreement (Kappa value = 0.795, P<0.001). The sparse rate of myocardial segments of the IQ group was 77% (24/31), which was much higher than that of the LEHR group by 23% (7/31) ( χ²=16.52, P<0.001). Owing to the high sparse rate myocardial segments of IQ, the original image and manual reregistration the MPI and CT images were analyzed. After re-coordination, the distribution of apical in the IQ group was found to be sparse (16%, 5/31), and the difference between the LEHR group (23%, 7/31) was not statistically significant (χ²=0.103, P=0.748). (2) Results of myocardial uptake were as follows. Compared with the previous IQ-CTAC, the myocardial uptake values of the apical wall (65.71±25.69)% vs.(58.68±20.39)%, anterior wall (204.23±43.24)% vs.(184.66±41.22)%, and septal wall (316.19±47.43)% vs. (270.03±65.33)% significantly decreased after CTAC(t=4.014, 4.232, and 5.473, respectively; all P<0.05). Meanwhile, myocardial uptake increased in anterior wall (204.68±41.14) % vs. (211.81±35.04)%, septal wall (319.13±44.90)% vs.( 350.87±44.24)%, and inferior wall (185.48±31.06)% vs.( 228.67±29.45)% of the LEHR group after CTAC(t=−2.471, P=0.019; t=−5.968, P<0.001; and t=−11.311, P<0.001, respectively). After IQ registration, compared with previous CTAC, the myocardial uptake values of anterior wall (212.06±33.59)% vs. (204.23±43.24)%, lateral wall (372.84±39.37)% vs. (355.81±46.79)%, inferior wall (219.13±25.10)% vs. (191.58±33.06)%, and septal wall (335.00±36.84)% vs. (316.19±47.43)% obviously increased (t=−2.497, P=0.018; t=2.672, P=0.012; t=−7.632, P<0.001 and t=−3.557, P<0.001, respectively).

Conclusions The distribution of inferior and inferior walls of LEHR-SPECT/CT CTAC was compensated, whereas the distribution of apical, anterior, and septal walls became sparse after IQ-SPECT/CT CTAC. In the IQ-SPECT/CT acquisition mode, overcorrection likely occurred after CTAC, and this situation was significantly improved after re-coordination.