[Impact of the correction of the attenuation in myocardial perfusion image with SPECT]

The aim of this study was to assess the effect of attenuation correction on gender differences in normals and to evaluate its effect on the size and severity of lateral wall perfusion defects in patients with circumflex artery disease.

Tomographic myocardial perfusion imaging with and without attenuation correction was performed on 32 patients with circumflex artery stenosis and compared with patients with less than 5% likelihood of coronary disease. Images were acquired with a triple headed scanner and reconstructed using an iterative algorithm and re-sliced in the short axis plane. Regional count densities were measured on selected short axis slices from the base to the apex in both patients and normals.

All attenuation corrected images were found to be more uniform than the non attenuation corrected images on the patients with less than 5% likelihood of coronary artery disease. The coefficient of variation was 12.5% for non attenuation corrected images versus 9.9% for attenuation corrected images (p < 0.0001). When female and male segmental count distributions were compared, significant differences were found which were resolved after attenuation correction. In patients with circumflex artery stenosis, the anterolateral and lateral count densities were lower at all levels with attenuation corrected images with an increasing difference from base to apex.

The use of attenuation correction results in a greater uniformity in normals and an improved estimation of extent and severity of perfusion defects in the territory of the circumflex artery.