Evaluation of 3D multi-contrast joint intra- and extracranial vessel wall cardiovascular magnetic resonance

Abstract

Background: Multi-contrast vessel wall cardiovascular magnetic resonance (CMR) has demonstrated its capability for atherosclerotic plaque morphology measurement and component characterization in different vasculatures. However, limited coverage and partial volume effect with conventional two-dimensional (2D) techniques might cause lesion underestimation. The aim of this work is to evaluate the performance in a) blood suppression and b) vessel wall delineation of three-dimensional (3D) multi-contrast joint intra- and extracranial vessel wall imaging at 3T.

Methods: Three multi-contrast 3D black blood (BB) sequences with T1, T2 and heavy T1 weighting and a custom designed 36-channel neurovascular coil covering the entire intra- and extracranial vasculature have been used and investigated in this study. Two healthy subjects were recruited for sequence parameter optimization and twenty-five patients were consecutively scanned for image quality and blood suppression assessment. Qualitative image scores of vessel wall delineation as well as quantitative Signal-to-Noise Ratio (SNR) and Contrast-to-Noise Ratio (CNR) were evaluated at five typical locations ranging from common carotid arteries to middle cerebral arteries.

Results: The 3D multi-contrast images acquired within 15mins allowed the vessel wall visualization with 0.8 mm isotropic spatial resolution covering intra- and extracranial segments. Quantitative wall and lumen SNR measurements for each sequence showed effective blood suppression at all selected locations (P < 0.0001). Although the wall-lumen CNR varied across measured locations, each sequence provided good or adequate image quality in both intra- and extracranial segments.

Conclusions: The proposed 3D multi-contrast vessel wall technique provides isotropic resolution and time efficient solution for joint intra- and extracranial vessel wall CMR.

Fig. 1

Sequence diagram of 3D-MERGE, T2-weighted VISTA and SNAP. (a - c) corresponds respectively to the pulse sequence diagram of 3D-MERGE, T2-weighted VISTA and SNAP. The fat saturation scheme used both for 3D-MERGE and T2-weighted VISTA is spectral presaturation inversion recovery (SPIR) and for SNAP is water selective excitation in practice but they are not shown in this schematic figure

Fig. 2

Illustration of 3D multi-contrast imaging coverage. Three stations of 3D time-of-flight coronal maximum intensity projection (MIP) fusion (d) and sagittal MIP fusion (e) are illustrated here only for a clear definition of imaging FOV. The curved multi-planar reconstruction (MPR) examples show the right (a - c) and left (f - h) sides arteries ranging from CCA through ICA to MCA, where (c, f), (b, g), and (a, h) correspond to the results of 3D-MERGE, T2-weighted VISTA and SNAP respectively. Note the plaques were detected at bilateral carotid bifurcations on all different contrast weighted images as shown by solid arrows

Fig. 3

Comparison of 3D-MERGE using different first order gradient moment (M₁) values. A representative comparison for M₁ values ranging from 500mT*ms²/m to 1500mT*ms²/m are illustrated in (a). Note that CSF can be better suppressed when using larger M₁ value (marked in yellow arrows). The vessel wall and lumen SNR are measured when different M₁ values are used and compared in (b)

Fig. 4

Optimization of T2-weighted VISTA echo train. Panel (a) shows the optimization of RFA scheme on echo train length and refocusing flip angle. The optimized RFA scheme (b, c) can further improve the sharpness of vessel wall boundary (marked in yellow arrows) but cause SNR loss compared to VFA scheme (d, e)

Fig. 5

Comparison of SNAP between selective and non-selective inversion pulse. The non-selective (b) inversion pulse can further improve the suppression of blood inflow artifacts in comparison to its selective counterpart (a)

Fig. 6

Performance comparison between different neurovascular coils. The optimized protocols are scanned using 16-channel commercialized and 36-channel developed neurovascular coil. The comparison results are shown in top and bottom row respectively

Fig. 7

Representative blood suppression and vessel wall delineation of the proposed 3D multi-contrast imaging. The curved MPR results in (a-c) show the overall blood suppression effect from 3D-MERGE, T2-weighted VISTA and SNAP sequence. The cross-sectional views at 11 locations were also provided with numbered subwindows in (a - c), including CCA, proximal and distal carotid bifurcation, ICA C1-C7 and MCA M1. The colored 5 locations were selected for quantitative analysis in this study. Note the plaque identified at location 3 illustrates different signal behaviors on different contrast weighted 3D sequences

Fig. 8

Example images showing the capability of arbitrary view for intra- and extracranial vessel wall delineation. An overview of vessel wall across multiple arteries can be provided using 3D isotropic VWI and curved MPR technique (a). Note that vessel wall thickening at the intracranial MCA M1 (b) and carotid bifurcation (c) can be clearly identified with 3D-MERGE, T2-weighted VISTA and SNAP sequences

Fig. 9

Visualization of one local plaque in 3D-MERGE, T2-weighted VISTA and SNAP images. Both curved longitudinal and cross-sectional views of the intracranial and carotid arterial walls can be observed using MPR on 3D-MERGE (a), T2-weighted VISTA (b) and SNAP (c) images. The locations of the 3 cross-sectional images in (d) are marked by the dashed lines on the curved longitudinal images. IPH component and severe wall thickening distributed around the carotid bulb can be confirmed based on the 3D multi-contrast images

Fig. 10

Quantitative SNR measurements of wall and lumen at five locations illustrating the blood suppression effectiveness. The five locations for SNR measurements are denoted by the dashed lines in one MPR result (a). (b - d) show the results of SNR measurement on wall and lumen at different locations for each 3D sequence. Note the lumen signal measured on SNAP images is actually in opposite polarity compared to the wall signal. Therefore the CNR of SNAP is SNR_w + SNR_l while the CNR of other two sequences are SNR_w-SNR_l. Marker "*" indicates the significant difference between wall and lumen signal were found by Wilcoxon signed rank sign test