J Korean Soc Radiol.  2016 Mar;74(3):160-168. 10.3348/jksr.2016.74.3.160.

Assessment of Carotid Diffusion-Weighted Imaging for Detection of Lipid-Rich Necrotic Core in Symptomatic Carotid Atheroma

• Lee KJ
• Kwak HS
• Chung GH
• Hwang SB
• Song JS

• KMID: 2155275
• DOI: http://doi.org/10.3348/jksr.2016.74.3.160

Abstract

PURPOSE
To evaluate the diagnostic usefulness of diffusion-weighted MR imaging (DWI) compared with contrast-enhanced MR imaging for the detection of the lipid-rich necrotic core (LRNC) of symptomatic carotid atherosclerotic plaques.
MATERIALS AND METHODS
Twenty-five patients (median age: 66 years; range: 45-78 years) with moderate-to-severe symptomatic carotid stenosis confirmed with contrast-enhanced carotid MR angiography who underwent carotid plaque MR imaging were retrospectively reviewed. An echo-planner DWI with b0, b200, b400, b800, and b1000 was performed along with carotid plaque MR imaging. Plaque visualization on DWI was analyzed by 2 reviewers on consensus. The contrast-to-noise ratio between the lumen and plaque was analyzed between variable b-values.
RESULTS
Carotid atherosclerotic plaques were identified on carotid DWI in 8 patients. Confirmed carotid atherosclerotic plaques were not identified on carotid DWI in 16 patients. The DWI-identified group had plaques with significantly greater maximal wall thickness and longitudinal length, as compared with the non-identified group. DWI with b200 had a higher contrast-to-noise ratio between the lumen and LRNC (p < 0.001). The mean apparent diffusion coefficient value from DWI with b200 for the LRNC was 0.51 +/- 1.55 x 10(-3) mm2/s.
CONCLUSION
There was less frequent identification of carotid atherosclerotic plaques with carotid DWI, as compared with contrast-enhanced MR imaging. This study suggested that carotid DWI cannot replace contrast-enhanced MR imaging for the detection of carotid plaques, including LRNC.

MeSH Terms

Angiography
Carotid Artery Diseases
Carotid Stenosis
Consensus
Diffusion
Diffusion Magnetic Resonance Imaging
Humans
Magnetic Resonance Angiography
Magnetic Resonance Imaging
Plaque, Atherosclerotic*
Retrospective Studies

Figure

• 

  Fig. 1 A 76-year-old man with left symptomatic carotid stenosis (case 4). A. TOF MR angiography shows an eccentric plaque of the left proximal internal carotid artery (arrow). B. Axial T1-weighted imaging shows a circumferential plaque (arrows). Maximal wall thickness is 8.2 mm and the longitudinal length of plaque is 26 mm. C. Black-blood contrast-enhanced MR imaging shows large LRNC (arrows) with thin/ruptured fibrous cap (arrowhead). D. DWI with b 200 s/mm2 shows high signal intensity with similar area of contrast-enhanced MR imaging (arrows). Contrast-to-noise ratio: 34.31 mm2/s. E. DWI with b 1000 s/mm2 shows low signal intensity, as compared with b 200 s/mm2. DWI = diffusion-weighted imaging, LRNC = lipid-rich necrotic core, TOF = time of flight

• 

  Fig. 2 A 78-year-old man with right symptomatic carotid stenosis. A. TOF MR angiography shows an eccentric plaque of the right proximal internal carotid artery (arrow). Maximal wall thickness is 5.2 mm and the longitudinal length of the plaque is 16 mm. B. Black-blood contrast-enhanced MR imaging shows large LRNC (arrows) with thin/ruptured fibrous cap (arrowhead). C. DWI with b 200 s/mm2 shows an ill-defined margin of carotid plaque due to partial volume artifact (arrow). DWI = diffusion-weighted imaging, LRNC = lipid-rich necrotic core, TOF = time of flight

• 

  Fig. 3 Contrast-noise ratio of each b-value in the DWI-identified group. DWI = diffusion-weighted imaging

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