7 tesla breast MRI may improve assessment of suspicious masses

1. Among women with suspicious breast lesions, 7 tesla (T) magnetic resonance (MR) imaging with diffusion weighting and combined parallel and readout-segmented echo-planar imaging (rs-EPI) showed a high diagnostic accuracy with fewer technical issues than previously-described 7T techniques.

2. Total image acquisition was less than 4 minutes in length, significantly shorter than with other 7T techniques.

Evidence Rating Level: 3 (Average)       

Study Rundown: By characterizing the motion of water molecules, DW imaging provides a novel MR imaging contrast mechanism and has high sensitivity for the detection of breast cancer. A significant advantage of diffusion-weighted (DW) imaging over conventional contrast-enhanced MR imaging is its high sensitivity for changes in the cellular environment without the need for intravenous contrast material. Breast cancer assessment with DW imaging is currently in clinical use at an MR field strength of 3T, but its performance at 7T has been limited by technical problems such as long scan time and image distortion. In the present study, women with suspicious findings detected by screening mammography or breast ultrasound underwent 7T MR imaging with diffusion weighting and combined parallel and rs-EPI, a new technique used to reduce geometric distortions, image blurring, and total scan time. The results suggest that this 7T MR imaging protocol can significantly reduce artifacts such as blurring and distortions and enable radiologists to more accurately differentiate between benign and malignant breast tumors. Total scan time was less than four minutes in all patients. Though this study was limited by its small sample size, its findings set precedent for additional studies of 7T breast imaging. If these findings can be confirmed in larger trials, the technique may prove useful on a wider scale for the evaluation of suspicious breast lesions.

Click to read the study in Radiology

Relevant Reading: Diffusion-weighted MR for differentiation of breast lesions at 3.0 T: how does selection of diffusion protocols affect diagnosis?

In-Depth [prospective cohort]: Thirty-three patients (mean age, 58 years; range, 23–81 years) with suspicious breast findings on screening mammography or breath ultrasound  were imaged using combined rs-EPI and parallel imaging with diffusion-weighted MR imaging at a field strength of 7T. All images were evaluated by two independent readers for image properties such as signal-to-noise ratio and geometric distortion. Regions-of-interest for each suspicious breast lesions were evaluated on a 10-point scale for lesion conspicuity (1, lesion not visible; 10, excellent visibility) and assessed on overall image quality (1, unacceptable image quality severely deteriorated by artifacts; 10, artifact-free image without distortions and with high anatomic detail). The largest lesions from each patient and normal breast parenchyma were examined morphologically, and diagnostic accuracy was calculated by both readers on the basis of an ADC threshold of 1.25 × 10³ mm²/sec to differentiate between benign and malignant breast tumors. Breast lesions were then followed for 18 months or until intervention (biopsy or surgery). A total of 33 lesions were identified, of which 23 were malignant and 10 were benign. Overall image resolution was less than one millimeter, enabling very detailed morphologic assessment of all the lesions. DW MR imaging at 7T with combined parallel and rs-EPI produced images with very high quality, rated 8 of 10 by both readers. Imaging artifact was reduced by a factor of seven as compared to single-shot echo-planar imaging (ss-EPI). Using the aforementioned ADC threshold, only one false negative diagnosis was rendered, yielding a high diagnostic accuracy. All patients were imaged in under 4 minutes (range 3 minutes, 31 seconds to 3 minutes, 40 seconds).

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Image: PD

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