How to segment epicardial adipose tissue accurately?

Hello everyone,
I’m going to use cardiac enhanced CT to measure the volume of epicardial adipose tissue (between the myocardium and the visceral pericardium), and when I use the Threshold tool, the extra-pericardial adipose tissue is also included(shown in Figure 1). Is there a way to differentiate the paracardial tissue only from the adipose tissue within the visceral pericardium of segment? which tool or extension should I use to achieve this purpose? In addition, whether there is an extension to automatically achieve this purpose (automatically identify the boundary of the pericardium) as shown in figure 2, which is obtained by QFAT software (version 2.0; Cedars-Sinai Medical Center)

Thanks a lot.