Detection of significant stenosis in the Left Anterior Descending Artery by ‘Virtual Myocardial Perfusion’ Bolus Tracking, 320 Slice Computed Tomography

Abstract

PurposeWe used bolus-tracking CT-images, which are usually used only to detect contrast-material in target organs for optimal-starting of acquisition, as virtual first pass myocardial perfusion images. MethodsRetrospective-analysis of 14 patients (10 male, 63±10years) diagnosed with ≥75% stenosis confined to left-anterior-descending-artery (LAD) (7 patients, Group-1) or insignificant stenosis of any coronary artery (7 patients Group-2) diagnosed using invasive-coronary-angiograms (ICA) and enhanced 320-slice-CT within 3-months and without incident between examinations. Bolus-tracking CT-images were acquired at mid-level left-ventricle (LV) until CT-attenuation of descending-aorta increased to 200HU. We measured CT-attenuation (HU) in the LV anterior-wall (AW), the basal inter-ventricular-septum (BIVS), and LV basal lateral-wall (BLW) in end-systole using both bolus-tracking images and routine, enhanced, early-phase CT-images. ResultsIn the bolus-tracking images, the Group-1 LV AW, BIVS, BLW CT-attenuation and ratio of LV AW CT attenuation to the average of BIVS and BLW were 36±7HU, 62±11HU, 58±25HU, and 0.6±0.1 respectively. In Group-2, they were 53±14HU, 56±9HU, 54±15HU, and 1.0±0.3 respectively. LV AW CT attenuation and the ratio of LV AW CT values to the average of BIVS and BLW, were significantly lower in Group-1 (both P<0.05). These values were not significant using routine, enhanced, early-phase CT-images. ConclusionsBolus-tracking CT-images may be useful to detect the LAD-confined stenosis that cannot be detected using routine, enhanced, early-phase CT-images. This can be achieved by measuring the local-reduction in CT-attenuation of the LV AW compared with the average of those of the BIVS and BLW and without the need for drugs, exercise or additional radiation-exposure.