CT Transit Time And Its Correlation To Cardiac Output Derived From Mr

ABSTRACT

Introduction: Pulmonary transit time (PTT), the time taken for contrast to travel from the left to right ventricle, can be used as a surrogate marker for cardiac output. There have been previous studies evaluating the prognostic significance of Magnetic Resonance (MR) and Computed Tomography (CT) PTT in heart failure patients. This study used dynamic CT images to determine the PTT and study its correlation with left and right ventricular ejection fraction and left and right cardiac output in COVID patients, with a known range of cardiac outputs. Method(s) 123 COVID-19 patients were retrospectively studied. A single contrast bolus timing scan was acquired with a 320-detector CT (Acquilion ONE, Canon). A single 2 mm slice was placed axially where left and right ventricle and descending aorta were visualised. Contrast administration and scan acquisition began at the same with 20 ml of Omnipaque with 40 ml saline flush at 5 ml/s. One image was acquired every second and the total scan time was 26 seconds. A circular ROI was placed in the centre left and right ventricle, the signal intensity was plotted over time for each of these regions. Matlab software was used to extract the peak contrast time between the right and left ventricles. MR cardiac images were acquired on a 3 T Prisma, which determined MR PTT, left and right ejection fraction (LVEF, RVEF) and left and right ventricle cardiac output (LVCO, RVCO). These values were already computed from a previous study where this data was taken from. Correlations were studied using the Pearson correlation method using Minitab software. Result(s) There was correlation between MR PTT and LVEF and RVEF, r = - 0.433 p<0.05 and r=-0.358 p<0.05 respectively. A correlation was also seen with CT PTT and LVEF (figure 1) and RVEF, r=-0.-345 p<0.05 and r=-0.2 p=0.029 respectively. A correlation was seen for MR PTT and LVCO and RVCO, r=-0.322 p<0.05 and r=-0.295 p<0.05 but not for CT PTT and LVCO and RVCO, r=-0.1 p=0.297 and r=-0.04 p=0.668 respectively. Conclusion(s) A correlation was seen between MR PTT and CT PTT for both LVEF and RVEF, but this was not seen for CT PTT and LVCO and RVCO. Further work is required to understand the limitations of the CT PTT and why it fails to correlate with these parameters. Limitations may include dynamic CT temporal resolution or due to poor image quality due to motion from breathing. Compared to previous studies there is agreement between the MR PTT and MR cardiac parameters. At this stage there is an indication that CT PTT could be a potential tool to estimate LVEF and RVEF. [Formula presented]Copyright © 2023