Comparison of 3 D T 1 TSE BB

Comparison of 3 D T 1 -TSE BB MRI and i. MSDE prepared 3 D T 1 -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

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. 1 A). • The improved motion-sensitization driven equilibrium (i. MSDE) sequence has been proposed to improve blood suppression 1) (Fig. 1 B). A Fig. 1 Normal Volunteer. A. 1). Wang J et al. J Magn Reson Imaging 31(5): 1256 -63, 2010 B B. BB MRI without i. MSDE shows substantial blood signal (arrowhead). BB MRI with i. MSDE efficiently suppresses carotid blood signal (arrowhead).

Purpose • To compare the clinical significance of i. MSDE prepared 3 D T 1 -TSE BB MRI with that of 3 D T 1 -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 • 3 T MRI (Achieva, Quasar Dual; Philips) with a 16 channel NV array coil • 3 D T 1 -TSE BB MRI sequences with and without i. MSDE • Voxel sizes for 3 D T 1 -TSE BB MRI and i. MSDE were 0. 9 × 0. 9 mm and 0. 93 × 1 mm, respectively. • Scanning times for 3 D T 1 -TSE BB MRI and i. MSDE were 3 min and 48 s and 4 min and 7 s, respectively.

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.

Result The border between the vessel wall and blood lumen Quantitative assessment P<0. 01 Not significant Score Contrast Ratio Visual assessment i. MSDE (+) i. MSDE (-) BB without i. MSDE is better than that with i. MSDE in visual assessment.

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

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

Result Signal intensity ratio (SIR) of plaque to adjacent muscle SIR i. MSDE (+) Not significant SIR　1. 77 i. MSDE (-) SIR　1. 82 i. MSDE (+) i. MSDE (-) No significant difference is found between the two.

Conclusion • These preliminary results suggest that the i. MSDE prepared 3 D T 1 -TSE BB MRI is not as good as the 3 D T 1 -TSE BB MRI for the assessment of plaque morphology for patients with cervical carotid arteries. Apparently, the i. MSDE 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 i. MSDE 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.