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Dynamic Contrast-Enhanced Magnetic Resonance Imaging of Breast Tumors at 3 and 7 T: A Comparison

Gruber, Stephan PhD*; Pinker, Katja MD*†; Zaric, Olgica MSc*†; Minarikova, Lenka MSc*; Chmelik, Marek PhD*; Baltzer, Pascal MD; Boubela, Roland N. MSc; Helbich, Thomas MD; Bogner, Wolfgang PhD*; Trattnig, Siegfried MD*

doi: 10.1097/RLI.0000000000000034
Original Articles
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Objectives The objective of this study was to compare the image quality, contrast enhancement behavior, and diagnostic value of bilateral 3-dimensional dynamic contrast-enhanced breast magnetic resonance imaging (MRI), with high spatial and temporal resolution, at 3 and 7 T, in the same patient group.

Materials and Methods Twenty-four consecutive patients (mean [SD] age, 57 [17] years) were included in this prospective institutional review board–approved study. Written informed consent was obtained from all patients. T1-weighted 3-dimensional sequences (time-resolved angiography with stochastic trajectories) were optimized at 3 and 7 T, with high temporal (both 14 seconds) and spatial resolution (1.1 × 1.1 × 1.1 mm3 [3 T], 0.7 × 0.7 × 0.7 mm3 [7 T]): echo time/repetition time, 2.84/6.01 milliseconds (3 T) and 2.5/4.75 milliseconds (7 T); acquisition time, 9 minutes (3 T/7 T). Dotarem® (gadoterate meglumine, Guerbet, Roissy CdG, France) contrast agent was injected intravenously as a bolus (0.2 mL/kg of body weight) after 3 baseline images. The images were rated according to breast imaging-reporting and data system by 2 radiologists in consensus. Signal-to-noise ratio and average enhancement ratios were measured quantitatively by means of region of interest analysis. In addition, B1 mapping was done in the same 5 healthy subjects at both field strengths.

Results Twenty-eight enhancing lesions were detected in the 24 patients at both field strengths (16 malignant, 12 benign). At 7 T, higher contrast than that at 3 T and good image quality were achieved. With the high spatial isotropic resolution of 0.7 mm at 7 T, images with more detailed information could be acquired when compared with those acquired at 3 T. Sensitivity was 93.75% and 100%, at 3 and 7 T, respectively. Specificity was 91.67% at both field strengths. The signal-to-noise ratio at both field strengths was comparable, but at 7 T, the spatial resolution was 3.2-times higher than that at 3 T. A signal-to-noise ratio decrease toward prepectoral breast regions due to B1 inhomogeneities was observed at both field strengths but was stronger at 7 T (51%) than at 3 T (19%)(P = 0.0002). At 7 T, B1+ dropped by 20.7% and 32.8% in the prepectoral and lateral region of the breast in healthy subjects.

Conclusions Our comparison study shows that 7-T DCE-MRI provides simultaneous high temporal and spatial resolution that is significantly improved compared with lower field strengths, but further technical improvements are necessary to overcome B1 inhomogeneity problems at 7 T to fully unfold the potential of breast MRI at 7 T.

From the *High Field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, †Department of Biomedical Imaging and Image-guided Therapy, Division of Molecular and Gender Imaging, Medical University of Vienna, and ‡High Field MR Centre, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.

Received for publication July 31, 2013; and accepted for publication, after revision, December 3, 2013.

Conflicts of interest and sources of funding: Supported by Austrian National Bank’s Jubiläumsfond Project nos. 13418, 13834, and 15082.

The authors report no conflicts of interest.

Reprints: Wolgang Bogner, PhD, MRCE, Department of Radiology, Medical University Vienna, Lazarettgasse 14, 1090 Vienna, Austria. E-mail: wolfgang@nmr.at.

© 2014 by Lippincott Williams & Wilkins