Third Generation Tactile Imaging System with New Interface, Calibration Method and Wear Indication

Abstract

During a clinical breast exam, a doctor palpates the breast and uses factors such as estimated size and stiffness of subcutaneous inclusions to determine whether they may be malignant tumors. The Tactile Imaging System (TIS) under development at the Control, Sensing, Networking and Perception Laboratory (CSNAP) is an effort to provide accurate and consistent characterization of inclusions. The sensing principle of the TIS is based on Total Internal Reflection (TIR) of light in a Polydimethylsiloxane (PDMS) optical waveguide positioned in front of a digital camera. When the PDMS is pressed against an object of greater stiffness it deforms, causing some light to escape the waveguide and be sensed by the camera. An algorithm maps the light pattern caused by the deformation and the force applied during the image acquisition to estimate the size, depth and stiffness of the inclusion based on a kernel model. The Third Generation Experimental TIS (TIS 3E) is an effort to improve the performance, repeatability, and usability of the system. Performance is increased through a new graphical user interface (GUI) allowing fine tuning of camera parameters, and interchangeable sensing probes for varying PDMS waveguides. Repeatability is improved with a digitally controlled lighting system, hardware triggered force sensing, and an online PDMS lighting and condition monitoring system, lowering the overall measurement error of the system. Usability is improved by a new chassis, reducing the device size and weight by 50 percent. Accuracy of the TIS 3E is comparable to the maximum accuracy TIS 1E, and exceeded the minimum accuracy of the TIS 1E. The measurement frequency was also increased from 10Hz to 50Hz. The TIS 3E will provide an accurate, consistent data acquisition platform for future Tactile Imaging Research efforts.