Attenuation correction for dedicated cardiac SPECT imaging without using transmission data

INTRODUCTION: Attenuation correction (AC) using transmission scanning like CT is the standard method to increase the accuracy of cardiac SPECT images. Recently developed dedicated cardiac SPECT do not support CT and thus, scans on these systems are vulnerable to attenuation artifacts. This study aimed to present a new method for generating attenuation map directly from emission data by segmentation of precisely nonrigid registration XCAT-digital phantom with cardiac SPECT image.
METHODS: In-house developed nonrigid registration algorithm automatically aligns the XCAT- phantom with cardiac SPECT image to precisely segment the contour of organs. Pre-defined attenuation coefficients for given photon energies were assigned to generate attenuation maps. The CT-based attenuation maps were used for validation with which cardiac SPECT/CT data of 38 patients were included. Segmental myocardial counts of a 17-segment model from these databases were compared on the basis of the paired t-test.
RESULTS: The mean, and STD (standard deviation) of the MSE (mean square error) and SSIM (structural similarity index) measure of female stress phase between proposed attenuation maps and the CT attenuation maps were 6.99 ± 1.23% and 92 ± 2.0%, of the male stress were 6.87 ± 3.8% and 96 ± 1.0%. ProAC and CTAC average myocardial perfusion count were significantly higher than that in non-AC in the mid- inferior, mid-lateral, basal-inferior and lateral regions (P<0.001).
DISCUSSION AND CONCLUSION: The proposed attenuation maps showed good agreement with the CT-based attenuation map. Therefore, it is feasible to enable AC for dedicated cardiac SPECT or SPECT standalone scanner.