Abstract
BackgroundT2-weighted (T2w) intracranial vessel wall imaging (IVWI) provides good contrast to differentiate intracranial vasculopathies and discriminate various important plaque components. However, the strong cerebrospinal fluid (CSF) signal in T2w images interferes with depicting the intracranial vessel wall. In this study, we propose a T2-prepared sequence for whole-brain IVWI at 3T with CSF suppression.MethodsA preparation module that combines T2 preparation and inversion recovery (T2IR) was used to suppress the CSF signal and was incorporated into the commercial three-dimensional (3D) turbo spin echo sequence-Sampling Perfection with Application optimized Contrast using different flip angle Evolution (SPACE). This new technique (hereafter called T2IR-SPACE) was evaluated on nine healthy volunteers and compared with two other commonly used 3D T2-weighted sequences: T2w-SPACE and FLAIR-SPACE (FLAIR: fluid-attenuated inversion recovery). The signal-to-noise ratios (SNRs) of the vessel wall (VW) and CSF and contrast-to-noise ratios (CNRs) between them were measured and compared among these three T2-weighted sequences. Subjective wall visualization of the three T2-weighted sequences was scored blindly and independently by two radiologists using a four-point scale followed by inter-rater reproducibility analysis. A pilot study of four stroke patients was performed to preliminarily evaluate the diagnostic value of this new sequence, which was compared with two conventional T2-weighted sequences.ResultsT2IR-SPACE had the highest CNR (11.01 ± 6.75) compared with FLAIR-SPACE (4.49 ± 3.15; p < 0.001) and T2w-SPACE (−56.16 ± 18.58; p < 0.001). The subjective wall visualization score of T2IR-SPACE was higher than those of FLAIR-SPACE and T2w-SPACE (T2IR-SPACE: 2.35 ± 0.59; FLAIR-SPACE: 0.52 ± 0.54; T2w-SPACE: 1.67 ± 0.58); the two radiologists’ scores showed excellent agreement (ICC = 0.883).ConclusionThe T2IR preparation module markedly suppressed the CSF signal without much SNR loss of the other tissues (i.e., vessel wall, white matter, and gray matter) compared with the IR pulse. Our results suggest that T2IR-SPACE is a potential alternative T2-weighted sequence for assessing intracranial vascular diseases.
Highlights
Intracranial atherosclerotic disease is a leading cause of ischemic stroke worldwide, in the Asian population (Kim and Johnston, 2011; Qureshi and Caplan, 2014)
The signal evolution for T2IR-SPACE (Figure 2A) comprises four parts: (I) transverse magnetization (Mxy) modulated by T2 decay during the T2IR module, in which, the Mxy of cerebrospinal fluid (CSF) decreases slightly because of its long T2 value and the Mxy of vessel wall is close to zero at the end of the T2IR module; (II) a second 90ox pulse tipping the transverse magnetization to the negative longitudinal axis, and the Mz recovering from the −z axis during time of inversion (TI); (III) Mxy during the SPACE acquisition that performs around the null point of CSF; and (IV) recovery of the Mz during Trec
The subjective mean scores of T2IR-SPACE were significantly higher than those of Fluid-attenuated inversion recovery (FLAIR)-SPACE in all segments. This is because the IR pulse significantly reduced the signal-to-noise ratio (SNR) of the overall image and most parts of the intracranial vessel wall were missing in FLAIRSPACE images, as demonstrated in both volunteer subjects and patient subjects (Figures 3, 4)
Summary
Intracranial atherosclerotic disease is a leading cause of ischemic stroke worldwide, in the Asian population (Kim and Johnston, 2011; Qureshi and Caplan, 2014). Studies mainly focused on T1-weighted IVWI because of its ability to reveal vessel wall abnormalities with (i.e., atherosclerotic plaque) or without contrast agents (i.e., intraplaque hemorrhage), and it can help classify intracranial vasculopathy (i.e., vasculitis) (Qiao et al, 2011; van der Kolk et al, 2013; Dieleman et al, 2014; Zhang et al, 2015; Mandell et al, 2017; Young et al, 2019; Jia et al, 2020). We propose a T2prepared sequence for whole-brain IVWI at 3T with CSF suppression
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