Bilateral Diffusion-weighted MR Imaging of Breast Tumors with Submillimeter Resolution Using Readout-segmented Echoplanar Imaging at 7 T

Purpose: To evaluate the image quality, robustness, and diagnostic performance of submillimeter in-plane resolution diffusion- weighted (DW) magnetic resonance (MR) imaging at 7 T in the assessment of breast tumors. Materials and Methods: Institutional review board approval and written informed consent of five volunteers and 33 patients with 33 breast lesions (31 with histopathologic confirmation, two with confirmation at follow-up) were obtained. Image quality optimization and comparisons of readout-segmented echo-planar imaging (rs-EPI) and single-shot echo-planar imaging (ss-EPI) with or without parallel imaging were performed in volunteers. In all patients, bilateral DW imaging was performed in 3 minutes 35 seconds by using combined rs-EPI and parallel imaging with 0.9 x 0.9 mm in-plane resolution with a 7-T whole-body MR imager. Image quality, lesion conspicuity, and image properties (ie, signal-to-noise ratio, contrast-to-noise ratio) were assessed. Regions of interest were drawn in the largest lesion in each patient (23 malignant lesions, 10 benign lesions) by two independent readers. Apparent diffusion coefficient (ADC) values were used to differentiate between benign and malignant breast tumors. Results: DW imaging with combined parallel imaging and rs-EPI reduced artifacts (ie, blurring and geometric distortions) by a calculated factor of seven when compared with DW imaging with ss-EPI, and it improved image quality from a score of 1 of 10 to a score of 8 of 10. The rs-EPI sequence with a b value of 0 sec/mm(2) yielded high-spatial-resolution T2-weighted MR images. An ADC threshold of 1.275 x 10(-3) mm(2)/sec enabled differentiation between benign and malignant breast lesions, with sensitivity and specificity of 96% and 100%, respectively, for both independent readers. Conclusion: At 7 T, one DW imaging examination of less than 4 minutes yielded high-quality ADC maps and high-spatial-resolution T2-weighted MR images that were used to assess tumor and breast morphology. ADC quantification alone enabled excellent differentiation of benign and malignant breast lesions. (C) RSNA, 2014