Imaging the Intracranial Atherosclerotic Vessel Wall Using 7T MRI: Initial Comparison with Histopathology

Overview of histologic classification and the presence of vessel wall heterogeneity on MR imaging of the 44 samples of the CoW, including correlation scoring. “Artifact” indicates intima-media artifacts; F, fibrous plaque; FL, fibrolipid plaque; FS, fatty streak; Hom., vessel wall with homogeneous signal intensity; Hetero., vessel wall with heterogeneous signal intensity; IT, intimal thickening; NA, no anomaly (no atherosclerosis); Path.IT, pathologic intimal thickening.

Four examples of atherosclerotic plaques with corresponding signal heterogeneity on 7T MR images. Histologic sections (magnification ×10) with Van Gieson elastic (a) and H&E (b) staining, with corresponding 7T MR images of T1-weighted (c), PD-weighted (d), T2-weighted (e), and T2*-weighted (f) sequences. a1–f1, Cross-section of the left ICA of subject 3. Histologic examination shows fibrous plaque with proteoglycans (white arrow, a1–b1) and increased collagen (black arrow, a1–b1); a patch of foamy macrophages can also be appreciated (dashed white arrow, a1–b1). On the corresponding MR images, the rim of increased collagen can be seen as hyperintense on all sequences (black arrow, c1–f1), while the small patch of foamy macrophages corresponds with a hypointense area (dashed arrow, c1–f1). Due to the intima-media artifacts, a distinction between artifacts (arrowheads, a1–b1) and proteoglycans lining the artifacts within the hypointense area on MR imaging (white arrow, c1–f1) cannot be made. a2.1–f2.3, Cross-sections of the right vertebral artery (2.1), right ICA (2.2), and left ICA (2.3) of subject 2. a2.1–f2.1, Histologic examination shows fibrous plaque with increasing collagen from outside (white arrows, a2.1–b2.1) to inside (black arrows, a2.1–b2.1); on the corresponding MR images, the area with more strongly increased collagen appears as a mostly hyperintense inner area (dashed arrows, c2.1–f2.1), compared with the area with less collagen (white arrows, c2.1–f2.1). a2.2–f2.2, Histologic examination shows pathologic intimal thickening with proteoglycans and foamy macrophages (white arrow, a2.2–b2.2) and increased collagen (black arrow, a2.2–b2.2); again, the collagen-rich inner area appears isointense on the MR images (dashed white arrow, c2.2–f2.2), while the area with proteoglycans and foamy macrophages appears mostly hypointense (white arrow, c2.2–f2.2). a2.3–f2.3, Histologic examination shows fibrous plaque with a thick inner rim of increased collagen (black arrow, a2.3–b2.3) and a thick outer rim with foamy macrophages (white arrow, a2.3–b2.3); in this case, vessel wall thickening on MR imaging has a hypointense signal, corresponding with both foamy macrophages and increased collagen (white arrow, c2.3–f2.3).