Figure 1

The process of calculating myocardial extracellular volume (ECV). Step 1: Generation of subtraction image. Subtraction images are generated from pre-contrast and delayed-phase CT by using an automatic three-dimensional non-rigid image registration. Step 2: Determination of left ventricular (LV) axis and segmentation of LV myocardium (tracing of endocardial and epicardial border). This step is also automated in the software with function of manually correction. A region of interest is placed in the LV cavity on the subtraction image to obtain ΔHUb. Step 3: Generation of ECV polar map. Entering the hematocrit value gives the ECV values for each segment in a polar map. In the polar map, ECV values are displayed as fractions.