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  • Open Access

Histological validation of carotid plaque characterization by in-vivo T2 mapping in patients with recent cerebrovascular events: preliminary results

  • 1,
  • 1,
  • 2,
  • 3,
  • 2,
  • 1 and
  • 1
Journal of Cardiovascular Magnetic Resonance201416 (Suppl 1) :P173

https://doi.org/10.1186/1532-429X-16-S1-P173

  • Published:

Keywords

  • Carotid Plaque
  • Plaque Component
  • Plaque Type
  • Intraplaque Haemorrhage
  • FFPE Section

Background

Multicontrast CMR is the conventional method for in-vivo characterization of carotid plaques. However, its non-quantitative nature and the need for extensive post-acquisition interpretation limit its clinical application. We have recently proposed using in-vivo quantitative T2 mapping for atherosclerotic plaque characterization [Biasiolli et al. JCMR 2013, 15:69]. T2 maps have the advantage of providing an absolute physical measure of plaque components that can be standardized among different MR systems and widely adopted in multi-centre studies. This pilot study investigates the agreement between T2 mapping and histology using AHA plaque type classification.

Methods

CMR: 19 symptomatic patients scheduled for endarterectomy (14 males, 73 ± 11 years, range 54-89 years, IRB approved, written consent obtained) were imaged at 3T (Siemens Verio) with a pair of 2-channel phased-array carotid coils (Machnet). In addition to the conventional multicontrast CMR protocol, a novel black-blood multi-slice DANTE-prepared [Li et al. MRM 2012, 68:1423-1438] multiecho-spin-echo sequence was used to acquire 5 slices with 14 echoes (TR = 2000 ms, TE = 9-127 ms) in <4 minutes (partial Fourier = 5/8, FOV = 128 × 128, matrix size = 384 × 384, slice thickness = 2 mm, slice gap = 2 mm). DANTE parameters: flip angle = 8°, number of pulses = 120, time duration between pulses = 0.5 ms, Gz = 18 mT/m and gradient duration = 0.4 ms. T2 maps were generated by mono-exponential fitting using non-linear least-squares regression. A reviewer (L.B.) classified plaque types following the CMR-modified AHA scheme using T2 maps + TOF only. Histology: Carotid plaques were freshly obtained at the time of endarterectomy, divided at the level of maximal stenosis into two 4 mm-segments and processed for formalin-fixed paraffin-embedded (FFPE) sections and cryosections, respectively. FFPE sections were stained for H&E, Masson's trichrome, while cryosections were used for Oil-Red-O/adipophilin (foam cells marker) staining to visualize lipid. AHA type of plaque histology was determined by a reviewer (J.T.C.) blinded to the T2 map results. CMR-histology slice location matching was performed for each 4 mm segments using the carotid bifurcation as the common anatomical landmark and cross-sectional T1-weighted images of the vessel wall.

Results

6 of the 19 patients scheduled for endarterectomy were excluded due to severe patient motion artefacts on CMR. The table 1 presents the AHA type classification of the remaining 13 plaques using T2 maps + TOF vs. histology. The 2 cases of misclassification were due to the difficulty of staging intraplaque haemorrhage (IPH) accurately. T2 maps were able to differentiate lipid-rich necrotic core, fibrous tissue, calcification and recent IPH, as illustrated in the Figure 1 for a type VI plaque.
Table 1

AHA plaque type classification by CMR (T2 maps +TOF) vs. histology

Histology

CMR (T2 maps + TOF)

 

IV-V

VI

total

IV

2

-

2

V

3

1

4

VI

1

6

7

total

6

7

13

Figure 1
Figure 1

T2 map, multicontrast MRI and histology of a type VI plaque with a large lipid-rich necrotic core (LRNC) separated from the lumen by a thick fibrous cap, clear signs of recent intraplaque-haemorrhage (IPH) and calcification.

Conclusions

These preliminary results show the potential of in-vivo T2 mapping for atherosclerotic plaque characterization. The ability of T2 maps to discriminate plaque components was confirmed by histology.

Funding

This study was supported by EPSRC and Oxford Biomedical Research Centre.

Authors’ Affiliations

(1)
Radcliffe Department of Medicine, University of Oxford, Oxford, UK
(2)
Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
(3)
Nuffield Department of Surgical Sciences, University of Oxford, Oxford, UK

Copyright

© Biasiolli et al.; licensee BioMed Central Ltd. 2014

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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