Impact of formalin fixation on biventricular parameters in cardiac diffusion tensor imaging: A pilot study in a miniature swine model.

Purpose To examine the impact of formalin fixation on biventricular cardiac diffusion tensor imaging (cDTI) parameters in a miniature swine model, using histological findings as the reference standard. Methods High-resolution ex-vivo cDTI data of one healthy miniature swine were acquired at baseline and on days 5 and 9 after formalin fixation. Histology with hematoxylin and eosin staining was employed to assess helix angle (HA) and HA transmurality on day 10 following fixation. In total, 64 myocardial segments, including 48 left ventricular (LV) and 16 right ventricular (RV) segments, were analyzed in head-to-head comparison. Results For this heart, subepicardial HA became more negative after formalin fixation on cDTI, and subendocardial HA showed a positive increase, which led to a significant elevation in HA transmurality (all P < .05). Mean diffusivity decreased in LV and RV walls during the first 5 days of fixation (P < .05 and P < .01, respectively), with a further marked decrease in the LV wall over the next 4 days (P < .001) but no significant change in the RV wall. HAs derived from cDTI at baseline and on days 5 and 9 following fixation exhibited excellent consistencies in the LV wall and poor-to-good consistencies in the RV wall with those assessed with histology, among which baseline HA yielded the highest interclass correlation coefficient of 0.968 in the LV wall and 0.812 in the RV wall. Conclusion In this pilot study, formalin fixation had an impact on both cardiomyocyte orientations and diffusion properties derived from cDTI.