Quantitative Intracranial Atherosclerotic Plaque Characterization at 7T MRI: An Ex Vivo Study with Histologic Validation

Histologic sections (Van Gieson elastic stain) of 2 different samples from the CoW specimens classified as fibrous plaques: (A) right middle cerebral artery and (B) left intracranial internal carotid artery (arrowhead indicates fibrous tissue). The corresponding T1-weighted image (DESPOT1 acquired with a flip angle of 44°) and the calculated parametric maps (T1, T2, T2*, and PD) are shown. ROIs were drawn at the location of tissue components identified in the histologic section (blue ROI indicates fibrous tissue; green + red ROI, vessel wall) to calculate the mean T1, T2, T2*, and PD values for these regions. Here, fibrous tissue can be distinguished from the vessel wall in the T1 and T2 maps (partly) and, to a lesser extent, in the T2* map.

Histologic sections (H&E stain) of 2 different samples from the CoW specimens containing calcifications (A) and an intraplaque hemorrhage (B): right intracranial internal carotid artery (A), classified as fibrocalcified plaque, and middle part of the basilar artery (B), classified as fibrous plaque with an old hemorrhage (arrow indicates fibrous tissue, arrowhead: calcification, A, and hemorrhage, B). The corresponding T1-weighted image (DESPOT1 acquired with a flip angle of 44°) and the calculated parametric maps (T1, T2, T2*, and PD) are shown. ROIs were drawn at the location of tissue components identified in the histologic section (yellow ROI indicates calcification, A, or intraplaque hemorrhage, B; blue ROI, fibrous tissue; green + red ROI, vessel wall) to calculate the mean T1, T2, T2*, and PD values for those regions. Here, the tissue area containing calcifications can be well distinguished in both the PD and T1 maps and, to a lesser extent, in the T2 and T2* maps. The intraplaque hemorrhage can be distinguished from the surrounding fibrous tissue in the T1 and PD maps.