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  • MRI Technique Differentiates Benign Breast Lesions from Malignancies

    False-positives reduced by 70 percent in BI-RADS- 4 lesions.

    February 20, 2018


    An MRI breast imaging technique that requires no contrast agent, combined with sophisticated data analysis, could reduce the number of unnecessary breast biopsies, according to a new study in Radiology.

    Researchers recently studied an alternative approach to breast MRI with gadolinium-based contrast agents, which is used to screen women at high risk of breast cancer. The alternative eliminates the need for contrast agents in some cases by using diffusion-weighted imaging (DWI) measurements derived from MRI. The technique, known as diffusion kurtosis imaging, provides a picture of breast tissue on a microstructural level.

    “Diffusion kurtosis imaging has been introduced in DWI to provide important information on tissue structures at a microscopic level,” said study lead author Sebastian Bickelhaupt, MD, from the German Cancer Research Center, Heidelberg, Germany. “Since malignant lesions disrupt the tissue structures at this level, diffusion kurtosis might serve as a relevant marker of changes.”

    Dr. Bickelhaupt, co-lead author Paul Jaeger, MSc, and colleagues evaluated a retrospective analysis of data collected from 222 women at two independent study sites. The women had suspicious findings on mammography that were classified under the Breast Imaging Reporting and Data System (BI-RADS) as BI-RADS 4 and 5 breast lesions.

    Before biopsy, diffusion-weighted MRI was performed and lesions were segmented. Voxel-based kurtosis fitting was performed, with adaptions to account for fat signal contamination. A radiomics feature model was developed by using a random forest regressor. Conventional interpretations of MRI were also assessed for comparison. To prevent new false-negative results and decrease the number of false-positive decisions, the sensitivity of at least 98 percent was retained since that is comparable to core-needle biopsy, which has a sensitivity between 87 and more than 97 percent.

    In an independent test set of 127 women, the radiomics analysis reduced false-positive findings by 70 percent, while detecting 60 of 61 malignant lesions, or 98 percent in BI-RADS-defined 4a and 4b lesions. Those women with BI-RADS-defined 5 lesions had no added diagnosis benefit through the radiomics feature model.

    “The model might help to lower the number of BI-RADS 4 lesions suspected of being cancer on the basis of screening mammography while retaining a high sensitivity similar to the sensitivity reported for biopsies themselves,” Jaeger said.

    Should the results hold in larger trials, the model has potential advantages in the clinic for women with BI-RADS 4 lesions.

    “The new approach is not intended to replace current contrast-enhanced breast MRI protocols in general,” Dr. Bickelhaupt said, “but to expand the spectrum of options available to differentiate between malignant and benign breast lesions.”



    Bickelhaupt Figure 1
    Two-dimensional sections of a three-dimensional acquisition of images of a malignant tumor. Diffusion weighted imaging (DWI) with b values of (a) 0, (b) 100, (c) 750, and (d) 1500 sec/mm2. Apparent diffusion coefficient (ADC) map and apparent kurtosis coefficient (AKC) map show the resulting pixel values after Kurtosis fitting. Notably, white pixels inside lesion constitute background after exclusion for not matching the fit criteria.

    Bickelhaupt Figure 2
    Receiver operating characteristic plot for the radiomics model, apparent kurtosis coefficient (AKC) median and apparent diffusion coefficient (ADC) median. Dots illustrate the resulting thresholds.

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