Loss of fine structure and edge sharpness in fast‐spin‐echo carotid wall imaging: Measurements and comparison with multiple‐spin‐echo in normal and atherosclerotic subjects

Purpose: To test whether the k ‐space acquisition strategy used by fast‐spin‐echo (FSE) is a major source of blurring in carotid wall and plaque imaging, and investigate an alternative acquisition approach. Materials and Methods: The effect of echo train length (ETL) and T 2 on the amount of blurring was studied in FSE simulations of vessel images. Edge sharpness was measured in black‐blood T 1 and proton‐density weighted (T 1 W and PDW) carotid images acquired from 5 normal volunteers and 19 asymptomatic patients using both FSE and multiple‐spin‐echo (Multi‐SE) sequences at 3 Tesla. Plaque images were classified and divided in group α (tissues' average T 2 ∼40–70 ms) and group β (plaque components with shorter T 2 ). Results: Simulations predicted 26.9% reduction of vessel edge sharpness from Multi‐SE to FSE images (ETL = 9, T 2 = 60 ms). This agreed with in vivo measurements in normal volunteers (27.4%) and in patient group α (26.2%), while in group β the loss was higher (31.6%). Conclusion: FSE significantly reduced vessel edge sharpness along the phase‐encoding direction in T 1 W and PDW images. Blurring was stronger in the presence of plaque components with short T 2 times. This study shows a limitation of FSE and the potential of Multi‐SE to improve the quality of carotid imaging. J. Magn. Reson. Imaging 2011;33:1136–1143. © 2011 Wiley‐Liss, Inc.