A "hybrid" method for measuring myocardial wall thickening from gated PET/SPECT images.

UNLABELLED We introduce a hybrid index, HYB, which combines counts with geometric information to measure wall thickening from PET/SPECT gated images. Its accuracy is compared with that of a count-based index (MAX) and a geometric index (FWHM). METHODS For each index, the index values versus thickness and the estimated thickening values versus true thickening were investigated using theoretical analyses, realistic simulated data obtained from clinical gated MR scans, phantom measurements and preliminary gated MRI and PET patient studies. Each index was studied for different spatial resolutions and noise and background conditions. The performance of each index was quantified using a parameter "Q" reflecting bias and variability of thickening estimates. RESULTS HYB varied more linearly with thickness than MAX and FWHM, resulting in a better Q value than with MAX and FWHM for all noise, background and spatial resolutions. ROC analysis confirmed that HYB significantly increases the sensitivity and specificity for detection of wall thickening abnormalities (sensitivity = 100%; specificity = 85% for HYB, 95% and 50% for MAX and 100% and 0% for FWHM, respectively). CONCLUSION Use of the hybrid index instead of conventional count-based or geometric indices should improve the classification of normal/abnormal wall thickening values in gated SPECT and PET.