Dynamic contrast breast MRI is becoming an important adjunct in screening women at high risk for breast cancer,
determining extent of disease (staging) and monitoring response to therapy. In dynamic contrast breast MRI,
regions of rapid contrast uptake indicate increases in vascularity which can be associated with abnormal tissue,
sometimes significant for malignant disease. To show these areas of enhancement, subtractions between the pre and
post contrast images and maximum intensity projections (MIPs) are computed. Many projections are obscured by
normally enhancing anatomy (heart, aorta, pulmonary vessels). Identification of these structures allows their
removal from MIPs, which improves image quality, diagnostic utility and the conspicuity of the enhancing regions.
In this study, a fully automated classifier is presented which uses the spatial location of enhancing regions to
separate those that occur inside the chest wall from those occurring in the tissue of interest (breast, axilla, chest
wall). The classifier was trained on 21 studies each acquired at a different institution (699 clusters of pixels), and
tested on 7 studies (231 clusters of pixels) that were not part of the training set. Multiple cost functions for training
were examined. The measurements for the peak performance of the classifier were sensitivity 97.0%, specificity
99.4%, PPV 99.9%, NPV 78.8%.
Breast MR is being employed to detect, diagnose, and stage breast cancer. With a breast MR study, areas that exhibit
rapid uptake of contrast followed by washout behavior have been shown to be indicative of malignant tissue. The most
common way to display this temporal information is with a time versus percent enhancement curve that plots the
enhancement of the tissue for each series relative to a baseline or pre contrast series. The generation of time curves is
commonly done using manual methods, but could easily be automated by a computer to reduce user variability. The
information obtained by the time curve can then be used for computer assisted analysis of suspicious areas. We
compare two methods for the automated detection of such time curves for 42 malignant lesions. The first method is a
previously published technique which finds the highest enhancing 3x3 area of a lesion to generate a curve. The second
method is a new hierarchical search that examines end time point behavior in combination with enhancement to find an
optimal curve location. The two methods for curve generation are examined in their ability to produce a washout type
curve, which has a greater likelihood of being malignant than curves that continue to enhance. The time curves found
using highest percent enhancement method showed washout in 52 percent (22/42) of lesions. Using the hierarchical
search algorithm, 90 percent (38/42) of lesions showed washout type curves
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