Dept. of Radiology, Mie University School of Medicine, Mie, Japan Comparison of 3D T1-TSE BB MRI and iMSDE prepared 3D T1-TSE BB MRI in patients with cervical carotid stenosis confirmed by DSA Masayuki Maeda, Katsuhiro Inoue, Tsunehiro Yamahata, Maki Umino, Hajime Sakuma Dept. of Radiology, Mie University School of Medicine, Mie, Japan

1). Wang J et al. J Magn Reson Imaging 31(5): 1256-63, 2010 Background For accurate morphology assessments of vessel wall diseases, efficiently flowing blood signal suppression is important. Nevertheless, because of the complicated flow patterns of cervical carotid artery bifurcation, current black-blood (BB) imaging techniques are frequently degraded by plaque-mimicking artifacts (Fig. 1A). The improved motion-sensitization driven equilibrium (iMSDE) sequence has been proposed to improve blood suppression1) (Fig. 1B) . A B Fig. 1 Normal Volunteer. BB MRI without iMSDE shows substantial blood signal (arrowhead). BB MRI with iMSDE efficiently suppresses carotid blood signal (arrowhead). 1). Wang J et al. J Magn Reson Imaging 31(5): 1256-63, 2010

Purpose To compare the clinical significance of iMSDE prepared 3D T1-TSE BB MRI with that of 3D T1-TSE BB MRI in patients with cervical carotid stenosis confirmed by digital subtraction angiography (DSA)

Materials and Methods 45 patients with cervical carotid artery stenosis (NASCET mean 64.2％) confirmed by DSA 3T MRI (Achieva, Quasar Dual; Philips) with a 16 channel NV array coil 3D T1-TSE BB MRI sequences with and without iMSDE Voxel sizes for 3D T1-TSE BB MRI and iMSDE were 0.9 × 0.9 × 0.9 mm and 0.93 × 0.93 × 1 mm, respectively. Scanning times for 3D T1-TSE BB MRI and iMSDE were 3 min and 48 s and 4 min and 7 s, respectively.

Wilcoxon signed-rank tests were used for statistical analysis. Image Analysis Visual assessment The border between the vessel wall and blood lumen was rated for stenotic vessels using four-point scoring to differentiate between the lumen and wall because of the flow artifact or other artifacts. 4 = no artifact (clear), 3 = partial or mild artifact (obscure), 2 = substantial artifact (obscure), and 1 = impossible. Quantitative assessment Contrast ratios of the plaque and adjacent lumen were obtained, as were signal ratios of the plaque to the sternocleidomastoid muscle. Wilcoxon signed-rank tests were used for statistical analysis.

BB without iMSDE is better than that with iMSDE in visual assessment. Result The border between the vessel wall and blood lumen Visual assessment Quantitative assessment P<0.01 Not significant Score Contrast Ratio iMSDE (+) iMSDE (-) iMSDE (+) iMSDE (-) BB without iMSDE is better than that with iMSDE in visual assessment.

Case 1 The iMSDE prepared 3D T1-weighted BB MRI occasionally shows slightly blurred images. This is a potential disadvantage of the iMSDE. iMSDE (+) iMSDE (-) DSA

Case 2 The iMSDE was particularly effective for blood signal suppression in a few cases. Note that blood signal of ulcer is completely suppressed in iMSDE (red arrowhead). iMSDE (+) iMSDE (-) DSA

Result Signal intensity ratio (SIR) of plaque to adjacent muscle Not significant SIR　1.77 iMSDE (+) SIR SIR　1.82 iMSDE (-) iMSDE (+) iMSDE (-) No significant difference is found between the two.

Conclusion These preliminary results suggest that the iMSDE prepared 3D T1-TSE BB MRI is not as good as the 3D T1-TSE BB MRI for the assessment of plaque morphology for patients with cervical carotid arteries. Apparently, the iMSDE tends to show blurring of wall images in clinical cases, possibly because of the susceptibility to the physiological pulsation of vessels or subtle motion of patients. This blurring might be disadvantageous when the method is used for diseased cervical vessels in a clinical setting. However, the iMSDE demonstrated dramatic blood suppression in a few cases with complicated flow patterns in diseased vessels, suggesting its potential as a useful method. Further investigation must be undertaken to evaluate the appropriate application of this method in a clinical setting.