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ORAL PRESENTATION

Open Access

High resolution 3D diffusion MRI of carotid
plaque on 3T

Yibin Xie<sup>1,2*</sup>, Wei Yu<sup>3</sup>, Zhaoyang Fan<sup>1</sup>, Christopher T Nguyen<sup>1,2</sup>, Jing An<sup>4</sup>, Zhaoqi Zhang<sup>3</sup>, Debiao Li<sup>1,2</sup>

From 17th Annual SCMR Scientific Sessions
New Orleans, LA, USA. 16-19 January 2014

Background

Diffusion MRI (DWI and ADC) has been shown to pro-
vide excellent contrast for characterizing carotid plaque
components such as necrotic lipid core and intraplaque
hemorrhage ex vivo [1] and in vivo [2]. However, con-
ventional 2D EPI-based methods have suboptimal image
quality and limited spatial resolution leading to difficulties
in ADC calculation, limiting the clinical utility of this
technique. The purpose of this work is to develop a new
diffusion imaging method for carotid plaque characteri-
zation that (1) allows 3D imaging; (2) improves spatial
resolution (0.6 × 0.6 × 2 mm3); and (3) provides consistent
and high image quality.

Methods

Diffusion weighting was introduced with a separate dif-
fusion preparation module from readout, allowing
multi-shot high resolution 3D imaging. Readout was
designed based on 3D TSE for good and consistent
image quality at 3T. Reduced field-of-view with inner-
volume refocusing was developed to reduce TSE scan
time by 67%. Bipolar diffusion sensitizing gradients were
used to compensate first-order motion and minimize
eddy currents. Arterial blood was suppressed with
DIR for better vessel wall delineation. Six healthy and
two atherosclerosis subjects were scanned on a 3T scan-
ner (Siemens Verio) with the following parameters:
pulse-triggered; 3D transverse slab with in-plane resolu-
tion = 0.6 × 0.6 mm2; slice thickness = 2 mm; b = 30

and 300 s/mm2 along the slice direction; total scan
time = 5.5' ± 0.6'.

Results

High resolution DWI of carotid wall with excellent image quality has been achieved at 3T on both healthy and atherosclerosis subjects. Images at both b-values and ADC map showed clear delineation of vessel wall with successful motion compensation (Figure 1a). Quantification by region-of-interest analysis showed satisfactory mean SNR of 15.1 and 11.1 for the vessel wall at the two b-values, respectively. Effective blood suppression throughout the slices resulted wall-to-lumen CNR in the range of 9.4 to 13.4 (Figure 2a). Healthy arterial wall ADC value averaged 1.64 ± 0.23 × 10-3 mm2/s, which is comparable with previous studies (Figure 2b). Plaque areas in DWI were compared with those in post contrast T1 weighted images and lipid-rich necrotic core findings were consistent (Figure 1b).

Conclusions

Diffusion-prepared TSE allows, for the first time, 3D
diffusion imaging of the carotid arterial wall in vivo with
high spatial resolution and excellent image quality.
It has the potential to detect vulnerable carotid plaque
components such as lipid-rich necrotic core in vivo
without the use of the contrast media.

<footnote n="1">¹Biomedical Imaging Research Institute, Cedars Sinai Medical Center, Los Angeles, California, USA
Full list of author information is available at the end of the article</footnote>
**1a) Healthy Volunteer**

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**1b) Atherosclerosis Patient**

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**Figure 1 a (healthy subject):** Diffusion weighted image (DWI) at low b-value (30 mm²/s), high b-value (300 mm²/s) and calculated ADC map. The vessel walls are clearly visible with blood suppression. 1b (atherosclerosis patient): DWI at high b-value compared with post-contrast T1 weighted image and pre-contrast T2 weighted image. Note that part of the plaque area (pointed by arrow) is hyper-intense in DWI signifying lower diffusion in that area. The same area is hypo-intense in the post-contrast T1 weighted image suggesting lipid-rich necrotic core.

**2a)**

<table><thead><tr><th>Image Quantification</th><th>b = 30</th><th>b = 300</th></tr></thead><tbody><tr><td>Mean SNR: W/N</td><td>15.1±2.4</td><td>11.1±1.7</td></tr><tr><td>Mean CNR: (W-L)/N</td><td>13.4±2.2</td><td>9.4±1.6</td></tr></tbody></table>

W=Vessel Wall; L=Lumen; N=Noise

**2b)**

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**Figure 2 a:** Vessel wall SNR, CNR at both b-values measured respectively by region-of-interest analysis (vessel wall, lumen, remote area).

2b: Apparent diffusion coefficient (ADC) measurement of healthy carotid vessel wall compared with previous in vivo and ex vivo studies.

## Funding

NIH/NHLBI R01HL096119.

### Authors' details

¹Biomedical Imaging Research Institute, Cedars Sinai Medical Center, Los Angeles, California, USA. ²Bioengineering, University of California, Los Angeles, Los Angeles, California, USA. ³Anzhen Hospital, Beijing, China. ⁴Siemens Healthcare, Beijing, China.

Published: 16 January 2014

### References

1. Shinner: *ATVB* 1999, 27.

2. Kim: *JMRI* 2011, 30.

doi:10.1186/1532-429X-16-S1-O28

**Cite this article as:** Xie *et al*. High resolution 3D diffusion MRI of carotid plaque on 3T. *Journal of Cardiovascular Magnetic Resonance* 2014 16(Suppl 1):O28.

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