Textural kinetics: a novel dynamic contrast-enhanced (DCE)-MRI feature for breast lesion classification.

Dynamic contrast-enhanced (DCE)-magnetic resonance imaging (MRI) of the breast has emerged as an adjunct imaging tool to conventional X-ray mammography due to its high detection sensitivity. Despite the increasing use of breast DCE-MRI, specificity in distinguishing malignant from benign breast lesions is low, and interobserver variability in lesion classification is high. The novel contribution of this paper is in the definition of a new DCE-MRI descriptor that we call textural kinetics, which attempts to capture spatiotemporal changes in breast lesion texture in order to distinguish malignant from benign lesions. We qualitatively and quantitatively demonstrated on 41 breast DCE-MRI studies that textural kinetic features outperform signal intensity kinetics and lesion morphology features in distinguishing benign from malignant lesions. A probabilistic boosting tree (PBT) classifier in conjunction with textural kinetic descriptors yielded an accuracy of 90%, sensitivity of 95%, specificity of 82%, and an area under the curve (AUC) of 0.92. Graph embedding, used for qualitative visualization of a low-dimensional representation of the data, showed the best separation between benign and malignant lesions when using textural kinetic features. The PBT classifier results and trends were also corroborated via a support vector machine classifier which showed that textural kinetic features outperformed the morphological, static texture, and signal intensity kinetics descriptors. When textural kinetic attributes were combined with morphologic descriptors, the resulting PBT classifier yielded 89% accuracy, 99% sensitivity, 76% specificity, and an AUC of 0.91.

Opposed-phase MRI for fat quantification in fat-water phantoms with 1H MR spectroscopy to resolve ambiguity of fat or water dominance.

OBJECTIVE: The purpose of the study was to quantify the fat fraction in nine fat-water phantoms containing 0-80% fat using opposed-phase imaging with the qualitative guidance of 1H MR spectroscopy (MRS), which was used by observer 1 to visually assess the sizes of the water and fat peaks to apply two alternative mathematic formulas for the calculation of the fat fraction. In addition, the fat fraction was also quantified directly with 1H MRS as an independent method by two observers (observers 2 and 3). CONCLUSION: The fat fraction calculated with opposed-phase imaging (FF(OPI)) and that calculated with 1H MRS (FF(MRS)) correlated well with the known fat fractions of the phantoms (FF(P)): r = 0.99 for FF(OPI); p < 0.0001 and r = 0.96-0.98 for FF(MRS); p < 0.001, for observers 2 and 3, respectively. Opposed-phase imaging should be combined with 1H MRS to ensure accurate quantification of the fat fraction.