800-5 Improving Accuracy of Ultrafast Computed Tomography in the Detection of Angiographically Significant Coronary Artery Disease

In differentiating coronary calcium from artifact by ultrafast computed tomography (UFCT), many different thresholds have been proposed. UFCT has demonstrated a high sensitivity and only modest specificity to detect coronary calcifications when compared to angiography. The Agatston method is most widely used today, utilizing a minimum CT number of 130 Hounsfield units (HU). In an attempt to improve specificity without markedly reducing sensitivity, we evaluated 272 coronary vessels from 68 patients with angiography and UFCT coronary scanning. All patients underwent coronary angiography for clinical indications, and had UFCT scanning done within three months of the angiogram. A blinded reader evaluated all the UFCT scans. We then varied the minimum CT number to assess whether 130 HU was truly the best threshold. Sensitivity, specificity and accuracy for different thresholds are listed. Threshold 130 HU 150 HU 170 HU 200 HU Sensitivity 95% 92% 89% 87% Specificity 65% 72% 75% 78% Accuracy 72% 77% 78% 79% The results above indicate that 130 HU is too low a threshold to maximize accuracy of this test when compared with angiography. Sensitivity is reduced as the threshold is improved, however this result is not significant (p = 0.61). The improved specificity from 130 to 150 represents a significant improvement (p l 0.0001), although a larger study must be performed before widespread use of this new threshold is employed.