Suitability of intravascular imaging for assessment of cerebrovascular diseases

Purpose
Arteriosclerosis of the vascular system is associated with many accompanying diseases. Especially cerebral arteriosclerosis is a main risk factor for ischemic strokes. We want to verify the practicability of intravascular imaging like intravascular ultrasound and optical coherence tomography for the assessment of cerebral vessel walls and plaques.

Methods
We examined 18 Circuli arteriosi willisii postmortem. The data contained 48 plaques from 48 different vessel parts. The samples underwent intravascular and histological imaging to conduct a quantitative assessment of vessel wall parameters (healthy vessel wall, thinnest vessel wall, plaque thickness and vessel diameter) as well as to qualitatively evaluate the healthy vessel wall, fibrotic plaques, calcifications and cholesterol deposits in diseased vessels.

Results
The comparison showed statistically significant smaller measurements for thinnest vessel walls, normal vessel walls and vessel diameters in histology than in imaging. No statistically significant difference was reached for plaque diameters. Fibrotic plaques were characterized as hyper-intense with dorsal attenuation and calcifications as hypo-intense with dorsal attenuation in optical coherence tomography. In intravascular ultrasound, fibrotic plaques showed a homogeneous echogenicity without distal attenuation and calcifications were depicted as hyperechoic with dorsal sound shadows. Cholesterol deposits were hyper-intense in optical coherence tomography with strongly attenuated signals and in intravascular ultrasound; the deposits were hyper-intense with almost no attenuation.

Conclusion
Both intravascular methods allow for plaque characterization and quantification of plaque diameter in cerebral vessel walls. When compared with histology, a statistically significant bias was obtained for the ex vivo measurements of the normal vessel wall diameters.