Tactile, Orientation, and Optical Sensor Fusion for Tactile Breast Image Mosaicking

Breast cancer screening using tactile imaging (TI) is an advancing field of low-cost noninvasive medical imaging. Utilizing arrays of capacitive pressure transducers to perform a differential stress measurement of suspicious tissue, TI has been shown to be effective in measuring lesion size and stiffness, and subsequent differentiation of malignant and benign conditions, in repeated clinical studies. In order to further improve the lesion classification accuracy of clinical TI, this article presents a novel method of mosaicking tactile images to form a large composite tactile map using the vein structure within the breast to spatially register tactile data. This article demonstrates practical nonrigid tactile image mosaicking, using probe contact force and relative orientation sensor fusion to correct for the tissue deformation during tactile scanning, miniaturized and applied to a pre-clinical TI prototype. Testing of the proposed TI prototype on representative, tissue-mimicking, and silicone breast phantoms, with varying baseline elasticity and internal vein structure, yields typical image registration accuracies of 0.33% +/- 0.15%. In similar testing, the proposed system measures the background elasticity of the samples with worst case error < 4.5% over the range of 9-60 kPa, required for accurate lesion characterization. This work will lead into further clinical validation of TI for measurement and classification of in situ phantom and breast lesions, utilizing the delivered metrics from this work to improve differentiation accuracy.