Optical projection tomography permits efficient assessment of infarct volume in the murine heart postmyocardial infarction.
Bottom Line: Experimental studies therefore commonly assess injury by histological analysis of sections sampled from the infarcted heart, an approach that is labor intensive, can be subjective, and does not fully assess the extent of injury.Intact, perfusion-fixed, optically cleared hearts, collected from mice 7 days after induction of MI by coronary artery occlusion, were scanned by a tomograph for autofluorescence emission after UV excitation, generating >400 transaxial sections for reconstruction.Tissue processing for OPT did not compromise subsequent immunohistochemical detection of endothelial cell and inflammatory cell markers.
Affiliation: BHF/University Centre for Cardiovascular Science, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom;Show MeSH
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Mentions: For 3D quantification and comparison of infarct size, LGE-MRI image files were first converted to Digital Imaging and Communications in Medicine (DICOM) format, the international standard for medical images and related information. For LGE-MRI, infarct was identified by semiautomatic threshold setting with CAAS software (Pie Medical) to allow quantification of viable and infarcted myocardium (Fig. 2A). For OPT imaging, 3D volume quantification was performed using Analyze 11 (AnalyzeDirect, Overland Park, KS). In brief, reconstructed tomographic image files were imported into Analyze, then intensity thresholds were adjusted manually for one slice to achieve the optimum delineation between viable and infarcted tissue. A standard region growing algorithm within Analyze then allowed identification of regions of interest (ROIs) for infarct volume within that slice. Areas away from the infarcted ventricle that had similar pixel intensity e.g., the pericardium, were manually excluded (see Fig. 2B). This process was repeated at intervals of 10–20 slices throughout the infarct (260–340 slices), and then ROIs were propagated automatically for all slices in between the manually adjusted slices, forming an infarct ROI for the whole left ventricle (LV). Similarly, LV volume was determined by manually segmenting epicardial and endocardial contours at intervals of every 50 slices (360–450 slices), with automatic propagation of contours for all slices in between. LV volume was then calculated as the difference between epicardial and endocardial volumes. The pixel intensity threshold of the infarcted area was adjusted in both software packages so that only the lesion was selected. Infarct size was calculated as a proportion of LV volume (infarct volume/total LV volume × 100, LV volume includes viable myocardium above ligation). All OPT analyses were performed in a blinded manner and independently of MR images.
Affiliation: BHF/University Centre for Cardiovascular Science, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom;