The Utility of Intracranial Plaque Imaging Using 3-Tesla Magnetic Resonance Imaging for Middle Cerebral Artery Atherosclerosis

Research Article

Austin J Cerebrovasc Dis & Stroke. 2014;1(2): 1007.

The Utility of Intracranial Plaque Imaging Using 3-Tesla Magnetic Resonance Imaging for Middle Cerebral Artery Atherosclerosis

Kurisu K1, Shichinohe H1*, Abumiya T1, Kazumata K1, Nakayama N1, Terae S2 and Houkin K1

1Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Japan

2Department of Radiology, Hokkaido University Graduate School of Medicine, Japan

*Corresponding author: Shichinohe H, Department of Neurosurgery, Hokkaido University Graduate School of Medicine, North 15, West 7, Kita-ku, Sapporo, Japan

Received: July 07, 2014; Accepted: July 14, 2014; Published: July 16, 2014


Middle cerebral artery atherosclerosis often causes severe ischemic stroke. Plaque imaging techniques for extracranial carotid lesions with conventional magnetic resonance imaging are widely used to prevent subsequent stroke. However, the plaque imaging for intracranial atherosclerosis with the conventional magnetic resonance imaging is limited because of the poor imaging quality. We hypothesized that the use of high resolution magnetic resonance imaging might resolve the problem and the acquired image might be useful to estimate intra-cranial plaque component. Therefore, the aim of this study is to clarify the utility of a plaque imaging technique using high-resolution magnetic resonance imaging in patients with middle cerebral artery atherosclerosis. In 6 patients (mean, 62; range, 36-75), plaque imaging using T1- and T2-weighted black blood (BB) methods were performed with a 3 tesla scanner without a contrast medium. In each patient, the ability to identify any plaque characteristic was assessed, and the plaques were evaluated on the basis of their signal intensity. For result, plaque images were obtained with enough quality to evaluate plaque components in 5 patients. In a symptomatic case, the plaque included a high-intensity lesion in the T1-weighted black blood method, and this was considered a vulnerable plaque. The plaques in the other cases were iso-intensity and were considered non vulnerable plaques. In a representative case, sudden cardiac arrest occurred 6 months after the stroke. Unfortunately, transient global ischemia caused a severe cerebral infarction on the side of the untreated MCA stenosis. Our results showed that intracranial plaque imaging is useful to estimate plaque histology. In future, this method will be helpful to determine the optimal treatment, including endovascular surgery, for these patients.

Keywords: Intracranial plaque imaging; Middle cerebral artery stenosis; Middle cerebral artery atherosclerosis; High-resolution magnetic resonance imaging; Black blood methods


MCA: Middle Cerebral Artery; MRI: Magnetic Resonance Imaging; HR: High-resolution; TOF: Time-of-flight; BB: Black-blood; TSE: Turbo Spin Echo; TR: Repetition Time; TE: Echo Time; FOV: Field of View; ETL: Echo Train Length; NEX: Number of Excitations


It is well known that middle cerebral artery (MCA) atherosclerosis is an important cause of cerebral ischemic stroke [1-3]. It has been reported that subsequent strokes occurred in 1 or 2 years in approximately 25% cases of severe MCA stenosis [4,5]. Thus, the prevention of cerebral ischemic events is important for patients with MCA atherosclerosis.

Plaque imaging techniques that use magnetic resonance imaging (MRI) for imaging extracranial carotid lesions are widely used for subsequent stroke prophylaxis. It is known that plaque characteristics are closely related to clinical presentations and subsequent ischemic events [6-9]. On the basis of these facts, plaque imaging has been the standard for assessing plaque characteristics and for choosing the optimal therapeutic strategy for carotid artery lesions [8,10]. In patients with MCA stenosis, however, plaque evaluations with conventional MRI have been of limited utility because of the low resolution of the vessel walls of small arteries. Although high-resolution imaging with high-field MRI scanners may be expected to enable detailed visualization of the atherosclerotic plaques that are located in intracranial arteries, there have been only a few studies regarding the feasibility of high-resolution MRI (HR-MRI) for the examination of MCA atherosclerosis [11-16]. In the present study, we aimed to clarify the utility of intracranial plaque imaging using HR-MRI in patients with MCA atherosclerosis.

Materials and Methods


Intracranial plaque imaging for MCA atherosclerosis was performed in patients who had been diagnosed with MCA stenosis using time-of-flight magnetic resonance angiography (TOF-MRA). For all patients, CTA was also performed to diagnose MCA atherosclerosis and to evaluate degree of stenosis. The subjects in the present study included patients with symptomatic MCAatherosclerosis as well as those with asymptomatic lesions. Routine MRI (T1-, T2-, and diffusion-weighted imaging), MRA, and plaque imaging were performed in all patients who gave informed consent.

Imaging protocol

MRI examinations were performed with a 3T MRI system (Achieva 3.0-T TX series; Philips Medical Systems, Best, The Netherlands) and an 8-channel phased array coil. Both the raw TOF-MRA data and reconstructed blood vessel data were used for determining the position of the subsequent black-blood MRI (BB-MRI) scans. The BB technique with pre-regional saturation pulses of 80-mm thickness was used to saturate incoming arterial flow for all BB-MRI scans. Sagittal and coronal images were acquired in each patient. T1-weighted BB-MRI was acquired with a 2-dimensional turbo spin echo (TSE) sequence with the following imaging parameters: repetition time (TR)/echo time (TE), 500/16 ms; field of view (FOV), 100 × 100 mm; matrix size, 256 × 241; echo train length (ETL), 7; slice thickness, 3 mm; interslice gap, 0.3 mm; number of excitations (NEX), 8; and acquisition time, 2 min 19 s. For T2-weighted BB-MRI scans, the TSE sequence with a TR/TE of 3,000/80 ms was used. Scans were performed with the following parameters: FOV, 100 × 100 mm; matrix size, 256 × 230; ETL, 23; slice thickness, 3 mm; interslice gap, 0.3 mm; and NEX, 8. The scan time was 3 min 6 s for sagittal images and 1 min 33 s for coronal images.

Evaluation of plaque imaging

In each patient, the BB-MRI imaging quality was evaluated on the basis of the method reported by Ryu et al. that used the conspicuity of the vessel margins and lumen as well as the wall architecture [14]. The degree of imaging quality was assessed as follows: good, architecture was visualized in detail and the lumen and outer boundary of the artery were clearly defined; moderate, outer boundary and/or lumen partially obscured; and poor, outer boundary and lumen not identifiable [14].

For images with good or moderate imaging quality, the plaque signal intensity was characterized. Interpretation of the plaque signal intensity was made with reference to the adjacent gray matter of the brain parenchyma. The scans were evaluated by mutual agreement between 2 neurosurgeons (K. K., H. S.) [14,17]. When intraplaque high-intensity was observed in a T1-weighted image, we estimated the lesion to be a vulnerable plaque, including those with a lipid-rich necrotic core or intraplaque hemorrhage, similar to that observed in carotid plaques [10,18,19].


Clinical data

A summary of the clinical data for each case is illustrated in Table 1. The intracranial plaque imaging was performed in 6 patients with MCA atherosclerotic occlusive disease (mean age, 62 years; range, 36-75 years). Three of the 6 patients (50%) had been diagnosed with symptomatic MCA atherosclerosis, and the other patients (50%) had asymptomatic lesions. In the symptomatic cases, 2 patients (Cases 4 and 6) suffered from cerebral infarction, whereas the third patient (Case 3) developed transient ischemic attacks due to stenosis in the horizontal portion of MCA (M1). The lesions were located on M1 in 5 cases and on the insular portion of MCA (M2) in the sixth (asymptomatic) case.