Contrast-enhanced MR imaging of the breast at 3.0 and 1.5 T in the same patients: initial experience

Abstract

Purpose: To establish a pulse sequence for dynamic contrast material-enhanced magnetic resonance (MR) imaging of the breast at 3.0 T and to prospectively compare MR imaging at 3.0 T with MR imaging at 1.5 T in the same patients.

Materials and methods: A prospective intraindividual internal review board-approved study was performed in 37 women with 53 lesions (25 breast cancers, 28 benign focal lesions) who underwent contrast-enhanced dynamic bilateral subtraction MR imaging twice, once at 1.5 T with a standard technique (voxel size, 1.44 mm3) and once at 3.0 T (voxel size, 0.45-0.72 mm3) with variable repetition time and flip angle settings. Written informed consent was obtained. Sagittal single breast high-spatial-resolution MR imaging was performed with active fat suppression. Image quality, number and features of enhancing lesions, and Breast Imaging Reporting and Data System categories were compared by using the Wilcoxon matched-pairs signed rank test and Student t test for matched pairs. Diagnostic confidence was compared by using a receiver operating characteristic (ROC) analysis.

Results: With repetition time prolonged to account for longer T1 relaxation times at 3.0 T and a flip angle of 60 degrees, enhancement rates at 3.0 T were substantially below those at 1.5 T. In two patients with benign lesions, enhancement was rated as insufficient to establish diagnosis. When parameter settings were kept equivalent, equivalent enhancement rates were observed with both systems. With these settings, 3.0-T MR imaging yielded homogeneous signal intensity over the entire field of view. No dielectric resonance effects were observed. Overall image quality scores for the dynamic series were slightly higher at 3.0 T (P<.01). A total of 49 lesions were prospectively identified with both systems. Owing to substantial patient motion at 1.5 T, two malignant lesions in one patient were visualized at 3.0 T only. At 3.0 T, differential diagnosis of enhancing lesions was possible with higher diagnostic confidence, as reflected by a larger area under the ROC curve (P<.05).

Conclusion: Initial experiences indicate that contrast-enhanced MR imaging at 3.0 T is nearing readiness for clinical use.