A study of the dependence of protocol optimization on the left ventricular ejection fraction (LVEF) in coronary CT angiography (CCTA) examination

Abstract

The purpose of this study is to obtain a good quality image and to minimize patient doses and re-examination rates through an optimization of the protocol for coronary computed tomography angiography (CCTA) examination based on a comparison and an analysis of the heart rates (HRs) of patients who had left ventricular ejection fraction (LVEF) values of less than 40% and the HRs of ordinary patients. This study targeted 16 patients who received thallium single-photon emission computed tomography (SPECT) or echocardiography simultaneously among the patients who took the CCTA examinations. Depending on the LVEF value (30 ∼ 39, 40 ∼ 49, 50 ∼ 59, and 60% or above), the patients were divided into groups of four based on HR (50 ∼ 59, 60 ∼ 69, 70 ∼ 79, and 80 or above). DynEva software was used to set the region of interest (ROI) on the ascending aorta and for a measurement of the threshold value. Comparisons and analyses were made based on the LVEF values and the HRs, after which the results were compared with the ones from the existing examination protocols and contrast medium protocols. According to the study results, the relation between the HR and the LVEF demonstrated that it took a long time to reach the true 100 hounsfield unit (HU) when the LVEF was 40% or below. Contrasting media showed significant differences, except in the case where the HR was 80 or above, and/or the LVEF was less than 40%. Moreover, for an LVEF of less than 40%, time differences were significant when contrasting media reached the true 100 HU to begin the scanning process. Therefore, it was possible to predict that the contrasting media were already being washed out from the left ventricle.