Influence of tube potential on quantitative coronary plaque analyses by low radiation dose computed tomography: a phantom study.

Abstract

Previous studies have shown that employing the low dose computed tomography (CT) technique based on low tube potential reduces the radiation dose required for the coronary artery examination protocol. However, low tube potential may adversely influence the CT number of plaque composition. Therefore, we aimed to determine whether quantitative atherosclerotic plaque analysis by a multi-slice, low radiation dose CT protocol using 80 kilovolts (kV) yields results comparable to those of the standard 120kV protocol. Artificial plaque samples (n = 17) composed of three kinds of plaque were scanned at 120 and 80kV. Relative low-density and medium-density plaque component volumes obtained by three protocols (80kV, 60 Hounsfield units [HU] threshold; 120kV, 60 HU threshold; and 80kV, 82 HU threshold) were compared. Using the 60 HU threshold, relative volume of the low-density plaque component obtained at 80kV was lower than that obtained at 120kV (27 ± 3% vs. 51 ± 5%, P < 0.001), whereas relative volume of the medium-density plaque component obtained at 80kV was higher than that obtained at 120kV (73 ± 3% vs. 48 ± 5%, P < 0.001). By contrast, no significant difference in relative volume obtained at 80kV (82 HU threshold) versus 120kV (60 HU threshold) was observed for either low-density (52 ± 5% vs. 51 ± 5%) or medium-density (48 ± 5% vs. 48 ± 5%) plaque component. Low tube potential may affect the accuracy of quantitative atherosclerotic plaque analysis. For our phantom test, 82 HU was the optimal threshold for scanning at 80kV.