Effects of freezing, fixation and dehydration on surface roughness properties of porcine left anterior descending coronary arteries.

Background: To allow measurements of surface roughness to be made of coronary arteries using various imaging techniques, chemical processing, such as fixation and dehydration, is commonly used. Standard protocols suggest storing fresh biological tissue at -40°C. The aim of this study was to quantify the changes caused by freezing and chemical processing to the surface roughness measurements of coronary arteries, and to determine whether correction factors are needed for surface roughness measurements of coronary arteries following chemical processes typically used before imaging these arteries.

Methods: Porcine left anterior descending coronary arteries were dissected ex vivo. Surface roughness was then calculated following three-dimensional reconstruction of surface images obtained using an optical microscope. Surface roughness was measured before and after a freeze cycle to assess changes during freezing, after chemical fixation, and again after dehydration, to determine changes during these steps of chemical processing.

Results: No significant difference was caused due to the freeze cycle (p>0.05). There was no significant difference in the longitudinally measured surface roughness (Ra=0.99±0.39μm; p>0.05) of coronary arteries following fixation and dehydration either. However, the circumferentially measured surface roughness increased significantly following a combined method of processing (Ra=1.36±0.40, compared 1.98±0.27μm, respectively; p<0.05). A correction factor can compensate for the change Ra=Ra1+0.46in Ra due to processing of tissue, Where Ra, the corrected Ra, had a mean of 1.31±0.21μm.

Conclusions: Independently, freezing, fixation and dehydration do not alter the surface roughness of coronary arteries. Combined, however, fixation and dehydration significantly increase the circumferential, but not longitudinal, surface roughness of coronary arteries.