Clinical validation of attenuation corrected cardiac imaging with IQ-SPECT SPECT/CT

Objectives The objective of this study was to compared attenuation corrected (AC) SPECT performed in four min with IQ-SPECT with AC SPECT performed in 15-20 min with a standard commercial SPECT/CT.

Methods Fifty four pts referred for indicated SPECT perfusion imaging with Tc-99m tracers were evaluated with AC SPECT. Imaging was performed with both standard 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° contoured 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 attenuation corrected using CT images acquired immediately 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 with the same CT scan used for the standard study. 37 pts were low likelihood normals and 7 pts underwent coronary angiography. Images from the two methods were compared for quality, normalcy and correlation with angiography. Standard 17 segment scoring was employed.

Results Images were scored from 0 - unacceptable to 4 - excellent. Image quality was similar for the two methods with an average score of 3.11 for the standard method and 3.21 for IQ-SPECT, p=ns. 33 studies were rated of good or excellent quality with the standard method and 36 studies with IQ-SPECT, p=ns. Assessments of normalcy were very similar with values of 91% for the standard method and 97% with IQ-SPECT, p=ns. Angiographic correlations were again almost identical. Studies in pts without significant stenoses (<50%) were similarly normal. Summed stress scores were consistently higher in pts with more severe stenoses with IQ-SPECT.

Conclusions Four min cardiac AC perfusion imaging with IQ-SPECT provides images of comparable quality and normalcy compared to standard SPECT/CT imaging method.

Research Support Grant support from Siemens Healthcar