Simultaneous noncontrast angiography and intraplaque hemorrhage (SNAP) imaging: Comparison with contrast-enhanced MR angiography for measuring carotid stenosis

J Magn Reson Imaging. 2017 Oct;46(4):1045-1052. doi: 10.1002/jmri.25653. Epub 2017 Feb 6.

Abstract

Purpose: To evaluate in a proof-of-concept study the feasibility of Simultaneous Noncontrast Angiography and intraPlaque hemorrhage (SNAP) imaging as a clinical magnetic resonance angiography (MRA) technique for measuring carotid stenosis. There is a growing interest in detecting intraplaque hemorrhage (IPH) during the clinical management of carotid disease, yet luminal stenosis has remained indispensable during clinical decision-making. SNAP imaging has been proposed as a novel IPH imaging technique that provides carotid MRA with no added scan time. Flowing blood shows negative signal on SNAP because of phase-sensitive inversion recovery.

Materials and methods: In all, 58 asymptomatic subjects with 16-79% stenosis on ultrasound were scanned at 3T by SNAP with 0.8 mm isotropic resolution and 16 cm longitudinal coverage. Two readers measured luminal stenosis of bilateral carotid arteries (n = 116) on minimum intensity projections of SNAP using the NASCET criteria. In the subset (48 arteries) with contrast-enhanced (CE) MRA available for comparison, luminal stenosis was also measured on maximum intensity projections of CE-MRA.

Results: Intraclass correlation coefficients (ICCs) with 95% confidence intervals were 0.94 (0.90-0.96) and 0.93 (0.88-0.96) for intra- and interreader agreement on stenosis measurements, respectively. Corresponding kappas for grading stenosis (0-29%, 30-69%, 70-99%, and 100%) were 0.79 (0.67-0.89) and 0.80 (0.68-0.90). Agreement between SNAP and CE-MRA was high (ICC: 0.95 [0.90-0.98]; kappa: 0.82 [0.71-0.93]).

Conclusion: As a dedicated IPH-imaging sequence, SNAP also provided carotid stenosis measurement that showed high intra- and interreader consistency and excellent agreement with CE-MRA. Further comparisons with digital subtraction angiography and other noninvasive techniques are warranted.

Level of evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1045-1052.

Keywords: NASCET; carotid disease; intraplaque hemorrhage; magnetic resonance angiography.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Angiography / methods
  • Carotid Arteries / diagnostic imaging
  • Carotid Arteries / physiopathology
  • Carotid Stenosis / diagnostic imaging*
  • Carotid Stenosis / physiopathology
  • Contrast Media*
  • Feasibility Studies
  • Female
  • Hemorrhage / diagnostic imaging*
  • Hemorrhage / physiopathology
  • Humans
  • Image Enhancement / methods*
  • Image Processing, Computer-Assisted / methods*
  • Magnetic Resonance Angiography / methods*
  • Male
  • Middle Aged
  • Reproducibility of Results
  • Sensitivity and Specificity

Substances

  • Contrast Media