Co-registered Cardiac ex vivo DT Images and Histological Images for Fibrosis Quantification

Cardiac magnetic resonance (MR) imaging can detect infarct scar, a major cause of lethal arrhythmia and heart failure. Here, we describe a robust image processing pipeline developed to quantitatively analyze collagen density and features in a pig model of chronic fibrosis. Specifically, we use ex vivo diffusion tensor imaging (DTI) (\(0.6 \times 0.6 \times 1.2\) mm resolution) to calculate fractional anisotropy maps in: healthy tissue, infarct core (IC) and gray zone (GZ) (i.e., a mixture of viable myocytes and collagen fibrils bordering IC and healthy zones). The 3 zones were validated using collagen-sensitive histological slides co-registered with MR images. Our results showed a significant (\(\mathrm{p}< 0.05\)) reduction in the mean FA values of GZ (by 17%) and IC (by 44%) compared to healthy areas; however, we found that these differences do not depend on the location of occluded coronary artery (LAD vs LCX). This work validates the utility of DTI-MR imaging for fibrosis quantification, with histological validation.