Improved black-blood imaging using DANTE-SPACE for simultaneous carotid and intracranial vessel wall evaluation

Abstract

Purpose: The purpose of this study was to develop a three-dimensional black blood imaging method for simultaneously evaluating the carotid and intracranial arterial vessel walls with high spatial resolution and excellent blood suppression with and without contrast enhancement.

Methods: The delay alternating with nutation for tailored excitation (DANTE) preparation module was incorporated into three-dimensional variable flip angle turbo spin echo (SPACE) sequence to improve blood signal suppression. Simulations and phantom studies were performed to quantify image contrast variations induced by DANTE. DANTE-SPACE, SPACE, and two-dimensional turbo spin echo were compared for apparent signal-to-noise ratio, contrast-to-noise ratio, and morphometric measurements in 14 healthy subjects. Preliminary clinical validation was performed in six symptomatic patients.

Results: Apparent residual luminal blood was observed in five (pre-contrast) and nine (post-contrast) subjects with SPACE and only two (post-contrast) subjects with DANTE-SPACE. DANTE-SPACE showed 31% (pre-contrast) and 100% (post-contrast) improvement in wall-to-blood contrast-to-noise ratio over SPACE. Vessel wall area measured from SPACE was significantly larger than that from DANTE-SPACE due to possible residual blood signal contamination. DANTE-SPACE showed the potential to detect vessel wall dissection and identify plaque components in patients.

Conclusion: DANTE-SPACE significantly improved arterial and venous blood suppression compared with SPACE. Simultaneous high-resolution carotid and intracranial vessel wall imaging to potentially identify plaque components was feasible with a scan time under 6 min. Magn Reson Med 75:2286-2294, 2016. © 2015 Wiley Periodicals, Inc.

Keywords: DANTE; SPACE; black-blood imaging; carotid artery imaging; intracranial artery imaging; vessel wall imaging.

© 2015 Wiley Periodicals, Inc.

Figures

Figure 1

Sequence diagram of DANTE-SPACE. A DANTE preparation module, an optional anti-aliasing regional saturation module (R-sat) and a fat saturation module (F-sat) are played out immediately before SPACE readout module. DANTE preparation module consists of a series of small flip-angle RF pulses interleaved with dephasing gradients as described by Li et al (15). DANTE module is played out immediately before F-sat when R-sat is not needed. DANTE parameters include: flip angle = 10°, phase increment = 0°, number of pulses = 100; inter-pulse repeat time= 1ms; Gxyz = 25mT/m.

Figure 2

Combined imaging of carotid and intracranial vessel wall with DANTE-SPACE. (A) Anatomical coverage of the proposed protocol demonstrated on a sagittal MIP image of TOF MRA. A coronal imaging slab was rotated slightly (yellow box) to cover both carotid and vertibrobasilar arterial systems. (B) Reformatted pre- and post-CE DANTE-SPACE images of carotid arteries and major branches from 2 inches below the bifurcation up to the 2nd segment of middle cerebral artery. (C) Reformatted pre- and post-CE DANTE-SPACE images of vertebral arteries, basilar arteries and major braches up to anterior/posterior cerebral arteries.

Figure 3

(A) Simulated results for the percentage relative signal differences between DANTE-SPACE and SPACE across a range of physiologically relevant T1 (400~1550ms) and T2 (20~300ms) values. DANTE-SPACE parameters included: echo train length = 100; echo spacing = 1ms; TR/TE = 770/22ms. SI = signal intensity. (B) Comparison between DANTE-SPACE and SPACE for image contrast ratios of normal wall, recent hemorrhage, lipid core, and fibrous tissue (each versus skeletal muscle as reference). (C) Images of a T1 phantom consisting of multiple water tubes with different Gd concentration. T1/T2 values of the tubes measured by a basic spin-echo sequence are (in msec): #1:1276/885; #2:261/200; #3:1038/674; #4:1223/813; #5:1845/898; #6:368/291; #7:428/339, and #8:1144/757, respectively. Images were acquired by DANTE-SPACE, SPACE and 2D TSE with the same imaging parameters as the in vivo studies.

Figure 4

Two representative examples of improved arterial blood suppression by DANTE-SPACE. (A) Reformatted post-CE images at the carotid bifurcation from a healthy subject acquired using both SPACE and DANTE-SPACE. On the SPACE images significant residual blood was observed at the origin of internal carotid artery. It obscured the boundary between lumen and vessel wall and may be misidentified as a plaque (yellow arrow). On the DANTE-SPACE images lumen was clean and vessel wall appeared thin. (B) Reformatted post-CE images at internal carotid artery from a symptomatic patient suspected of stroke. Similar findings were observed in comparing SPACE and DANTE-SPACE.

Figure 5

A representative example of improved venous blood suppression by DANTE-SPACE. (A) On the post-CE SPACE images the venous blood was largely not suppressed causing visible flow artifacts along the PE direction (left to right). (B) On the post-CE DANTE-SPACE images the venous blood was well suppressed and the venous lumen appeared dark (arrows). Also note the reduced level of flow artifacts compared to SPACE images.

Figure 6

A representative example of improved CSF suppression by DANTE-SPACE from a healthy subject. The CSF surrounding the basilar arteries and its branches was further suppressed by DANTE-SPACE compared with SPACE, which helped better visualize the outer vessel boundaries.

Figure 7

Reformatted pre- and post-CE DANTE-SPACE images from a patient suspected of internal carotid artery dissection. The patient was a 43 y/o male with stroke symptoms. (A) Curved MPR images of both the dissected carotid arterial wall (left) and the normal carotid arterial wall (right). Note the thrombus near the bifurcation of the left ICA (single red arrow), and diffused arterial wall thickening along the middle segment (triple yellow arrows). (B) In-plane and cross-sectional images showing double lumen sign (single yellow arrow) of intracranial carotid artery which confirmed the diagnosis of dissection. Also note the enhancement of brain infarct in the post-CE image (double red arrows).

Figure 8

Reformatted pre- and post-CE DANTE-SPACE images of a vulnerable plaque. The patient was a 41 y/o male with stroke symptoms. Slice-matched T1w 2D TSE images were acquired as reference. (A) Pre-CE DANTE-SPACE images at the bifurcation showed hyperintensive plaque component suggesting intraplaque hemorrhage (yellow arrows). Also note the hypointense plaque component suggesting calcification (blue arrows). (B) Post-CE DANTE-SPACE images showed enhanced plaque component next to the lumen suggesting thin fibrous cap (red arrows).