Classification of small lesions in dynamic breast MRI: Eliminating the need for precise lesion segmentation through spatio-temporal analysis of contrast enhancement over time.
Characterizing the dignity of breast lesions as benign or malignant is specifically difficult forsmalllesions; they don't exhibit typical characteristics of malignancy and are harder to segment since margins are harder to visualize. Previous attempts at using dynamic or morphologic criteria to classify small lesions (mean lesion diameter of about 1 cm) have not yielded satisfactory results. The goal of this work was to improve the classification performance in such small diagnostically challenging lesions while concurrently eliminating the need for precise lesion segmentation. To this end, we introduce a method for topological characterization of lesion enhancement patterns over time. Three Minkowski Functionals were extracted from all five post-contrast images of sixty annotated lesions on dynamic breast MRI exams. For each Minkowski Functional, topological features extracted from each post-contrast image of the lesions were combined into a high-dimensional texture feature vector. These feature vectors were classified in a machine learning task with support vector regression. For comparison, conventional Haralick texture features derived from gray-level co-occurrence matrices (GLCM) were also used. A new method for extracting thresholded GLCM features was also introduced and investigated here. The best classification performance was observed with Minkowski Functionalsareaandperimeter, thresholded GLCM features f8 and f9, and conventional GLCM features f4 and f6. However, both Minkowski Functionals and thresholded GLCM achieved such resultswithout lesion segmentationwhile the performance of GLCM features significantly deteriorated when lesions were not segmented (p< 0.05). This suggests that such advanced spatio-temporal characterization can improve the classification performance achieved in such small lesions, while simultaneously eliminating the need for precise segmentation.
Department of Imaging Sciences and Biomedical Engineering, University of Rochester, 207 Robert B. Goergen Hall, Rochester NY 14627, USA.
Mahesh B
MB
Nagarajan
Markus B
MB
Huber
Thomas
T
Schlossbauer
Gerda
G
Leinsinger
Andrzej
A
Krol
Axel
A
Wismüller
Minkowski Functionals; dynamic breast MRI; mutual information; support vector regression; topological texture features