Improved carotid lumen delineation on non-contrast MR angiography using SNAP (Simultaneous Non-Contrast Angiography and Intraplaque Hemorrhage) imaging

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via Magnetic Resonance Imaging

Publication date: Available online 24 June 2019
Source: Magnetic Resonance Imaging
Author(s): Haining Liu, Jie Sun, Daniel S. Hippe, Wei Wu, Baocheng Chu, Niranjan Balu, Thomas Hatsukami, Chun Yuan

Abstract

Purpose

Simultaneous Non-Contrast Angiography and Intraplaque Hemorrhage (SNAP) was developed for improved imaging of intraplaque hemorrhage (IPH). Its signal polarity also allows for non-contrast time-of-flight MR angiography (TOF). This study sought to compare SNAP and TOF in delineating carotid lumen using contrast-enhanced MRA (CE-MRA) as the reference standard.

Materials and methods

Two hundred and eighty-nine matched slices from 15 arteries among 11 subjects (9 males and 2 females, mean age of 72.1 ± 8.6 years) with luminal stenosis on CE-MRA were studied. Cross-sectional slices centered around the carotid bifurcation were matched between the three MRA techniques (SNAP, TOF, and CE-MRA) and classified as slices with or without plaque (focal wall thickness ≥ 1.5 mm) by additional black-blood vessel wall MRI. Lumen area was measured using a Sobel gradient map for TOF and CE-MRA (magnitude images) and a polarity map for SNAP. Agreement between techniques for measuring lumen area and percent stenosis was evaluated using intraclass correlation coefficient (ICC) and paired t-test.

Results

Among the 289 matched slices, SNAP showed a higher agreement with CE-MRA than TOF for measuring lumen area (ICC: 0.93 vs. 0.83; p = 0.03). Agreement with CE-MRA was high for both SNAP and TOF in slices without plaque (ICC: 0.91 vs. 0.89; p > 0.05) but favored SNAP over TOF in slices with plaque (ICC: 0.93 vs. 0.80; p = 0.02).

Conclusion

SNAP, assisted by signal polarity information, demonstrated a higher agreement with CE-MRA in delineating carotid lumen compared to TOF, particularly in slices with plaque where flow conditions may be more complex.