Clinical comparison of four minute IQ-SPECT imaging with conventional parallel hole collimated SPECT/CT

Objectives The objective of this study was to quantitatively compare attenuation corrected (AC) SPECT using IQ-SPECT performed in four min with conventional parallel hole collimated SPECT/CT performed in 15-20 min.

Methods 110 pts referred for indicated SPECT perfusion imaging with Tc-99m tracers were evaluated with AC SPECT. Imaging was performed with both parallel hole collimation using a Siemens Symbia T16 SPECT/CT and the same system with the IQ-SPECT modification employing SMARTZOOM collimators and cardio-centric orbits. Standard SPECT/CT was performed over 180° orbits at 3° increments for 15-20 sec per view into 128x128 matrices and 4.8 mm pixels. Study time was 15-20 min and images were AC using CT images acquired before SPECT with the integrated CT. IQ-SPECT images were acquired over 208° cardio-centric orbits with 17 views per detector for 9 sec per view to 128x128 matrices and 4.80 mm pixels, total study time of 4 min, and corrected for AC. Normal databases were created from 30 low likelihood normal males and 22 low likelihood females. Standard 17 segment scoring and blackout polarmap analyses were employed (Corridor4DM).

Results Images were scored from 0 - unacceptable to 4 - excellent. Image quality was similar for the two methods, p=NS. Among 13 low likelihood normals not included in the normal databases, 11 were normal with IQ-SPECT and 12 were normal with standard SPECT/CT (p=NS). There were 14 pts with document coronary heart disease (CHD). The summed stress scores were similar with IQ-SPECT and standard SPECT/CT (13.9±10.2 as 12.4±11.4 respectively, p=NS). Blackout polarmap analysis demonstrated similar results for IQ-SPECT and standard SPECT/CT (27.8±18.7 as 23.9±22.5 respectively, p=NS). Angiographic correlations were similar with a trend to increased sensitivity with IQ-SPECT, 12 versus 8 true positives, p=NS by SSS and 13 versus 9 true positives, p=NS by blackout analyses.

Conclusions Quantitative analyses of IQ-SPECT and standard parallel hole collimated SPECT/CT provides images of comparable quality, normalcy and sensitivity