Identification and Quantitative Assessment of Different Components of Intracranial Atherosclerotic Plaque by Ex Vivo 3T High-Resolution Multicontrast MRI

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Fifty-three intracranial arterial specimens with atherosclerotic plaques from 20 cadavers were imaged by 3T MR with T1, T2, and proton-density–weighted FSE and STIR sequences. The signal characteristics and areas of fibrous cap, lipid core, calcification, fibrous tissue, and healthy vessel wall were recorded on MR images and compared with histology. The signal intensity of the lipid core was significantly lower than that of the fibrous cap on T2-weighted, proton-density, and STIR sequences and was comparable on T1-weighted sequences. Optimal contrast between the lipid core and fibrous cap was found on T2-weighted images. Ex vivo 3T MR imaging can accurately identify and quantitatively assess intracranial atherosclerotic plaque components, providing a direct reference for in vivo intracranial plaque imaging.

Abstract

Figure 2 from paper
Vertebral artery plaque with fibrous tissue and calcification was identified on multicontrast MR imaging and matched histology (20× magnification). Contours have been drawn for lumen (red), outer vessel wall (green), and calcification (black) on T2-weighted imaging and a hematoxylin-eosin-stained section. The lumen, total vessel, and calcification areas were 4.99, 12.97, and 0.53 mm2 on MR imaging and 4.86, 9.02, and 0.24 mm2 on histology. The vessel wall areas calculated by total vessel area minus lumen area were 7.98 and 4.16 mm2. The fibrous component area calculated by vessel wall area minus the calcification area was 7.45 and 3.93 mm2. The percentages of components (Specific Component Area / Vessel Wall Area × 100%) were 6.64% versus 5.73% for calcification and 93.36% versus 94.27% for fibrous tissue. Plaque burden (Vessel Wall Area / Total Vessel Area × 100%) was 61.52% versus 46.09%.

BACKGROUND AND PURPOSE

High-resolution 3T MR imaging can visualize intracranial atherosclerotic plaque. However, histologic validation is still lacking. This study aimed to evaluate the ability of 3T MR imaging to identify and quantitatively assess intracranial atherosclerotic plaque components ex vivo with histologic validation.

MATERIALS AND METHODS

Fifty-three intracranial arterial specimens with atherosclerotic plaques from 20 cadavers were imaged by 3T MR imaging with T1, T2, and proton-density-weighted FSE and STIR sequences. The signal characteristics and areas of fibrous cap, lipid core, calcification, fibrous tissue, and healthy vessel wall were recorded on MR images and compared with histology. Fibrous cap thickness and maximum wall thickness were also quantified. The percentage of areas of the main plaque components, the ratio of fibrous cap thickness to maximum wall thickness, and plaque burden were calculated and compared.

RESULTS

The signal intensity of the lipid core was significantly lower than that of the fibrous cap on T2-weighted, proton-density, and STIR sequences (P < .01) and was comparable on T1-weighted sequences (P = 1.00). Optimal contrast between the lipid core and fibrous cap was found on T2-weighted images. Plaque component mean percentages were comparable between MR imaging and histology: fibrous component (81.86% ± 10.59% versus 81.87% ± 11.59%, P = .999), lipid core (19.51% ± 10.76% versus 19.86% ± 11.56%, P = .863), and fibrous cap (31.10% ± 11.28% versus 30.83% ± 8.51%, P = .463). However, MR imaging overestimated mean calcification (9.68% ± 5.21% versus 8.83% ± 5.67%, P = .030) and plaque burden (65.18% ± 9.01% versus 52.71% ± 14.58%, P < .001).

CONCLUSIONS

Ex vivo 3T MR imaging can accurately identify and quantitatively assess intracranial atherosclerotic plaque components, providing a direct reference for in vivo intracranial plaque imaging.

 

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Identification and Quantitative Assessment of Different Components of Intracranial Atherosclerotic Plaque by Ex Vivo 3T High-Resolution Multicontrast MRI
jross
Jeffrey Ross • Mayo Clinic, Phoenix

Dr. Jeffrey S. Ross is a Professor of Radiology at the Mayo Clinic College of Medicine, and practices neuroradiology at the Mayo Clinic in Phoenix, Arizona. His publications include over 100 peer-reviewed articles, nearly 60 non-refereed articles, 33 book chapters, and 10 books. He was an AJNR Senior Editor from 2006-2015, is a member of the editorial board for 3 other journals, and a manuscript reviewer for 10 journals. He became Editor-in-Chief of the AJNR in July 2015. He received the Gold Medal Award from the ASSR in 2013.

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