Palpation has been routinely used by physicians to diagnose diseases for centuries. In Clinical Breast Examination (CBE), medical personnel screen for suspect lesions (that are 10- to 20-fold stiffer than surrounding tissue) by palpation using two or three fingers followed by precession about a fixed 1-2 in2 contact area. Typical pressure to avoid discomfort and also feel deeper palpable objects ranges from 40-90 KPa. However, palpation is highly qualitative and subjective; and it is not possible to follow progression in the morphological changes. The goal of the proof-of-concept study is to develop an ergonomic, low cost (less than $5) stethoscope-like probe to capture tactile images during palpation. The probe will be pressed at 30-90 KPa pressure and a series of images will be recorded in real time by pivoting the probe over a fixed contact area of about 1-2 in2 in a precession motion similar to CBE. The studies will be performed over a well-characterized physical model, an artificial breast, and a clinical test on humans. The tactile image would be at a resolution of ~100 µm to image ≥5 mm features at 20-30 mm depth from the surface with relative hardness of ≥10-fold compared to the surrounding matrix. Two key drivers for developing the technology are: (i) digitizing CBE will offer a screening record between biannual mammogram exams, for women below 40, and in low-income countries where accessibility to a mammogram is limited; and (ii) the current digital CBE instruments (with array of 1 mm size sensors compared to proposed 100 μm size pixels) require rubbing the device on the skin at constant pressure and speed to create an image by stitching together the frames, potentially causing distortions/smearing due to dynamics of the palpable features. The grayscale of the image for the proposed device will be linear making the analysis quantitative to detect local hardness and score and track the palpation over time. The low power of the device will allow connectivity to a USB port for power, signal, and imaging on a laptop computer or smart phone. To image more complex body topography, such as axillary and cervical lymph nodes, the design will allow for interchangeable device heads of different sizes. At the heart of the proposed device is a ~100 nm thick nanostructured film that converts pressure to electrical signal to form the tactile image. The film is a stratified structure of a monolayer of Au nanoparticles interposed by ~5 nm thick polymer layers. On pressing the film, the electron tunneling current between the particles modulates to measure the local pressure. There are two specific aims: (i) develop an unpackaged device to prove the principle in terms of resolution, sensitivity, power requirement for USB connectivity, and ability to image 10-fold harder structures 3-10 mm in size at depths of 3-30 mm using a physical model; and (ii) develop a handheld device for testing on artificial breast model and limited clinical study with ~50 de-identified patients with breast- pain complaints or who are scheduled for mammograms. The preliminary and published results (by PI) indicate that the specified resolution, sensitivity, and performance are possible. A US Patent was issued in 2010.

Project Narrative Vajra Instruments will design and build an ergonomic, stethoscope-like device that will obtain tactile images in real time during palpation using a procedure similar to that used in manual CBE. The tool will be a low-power device that may be interfaced with a laptop computer or smart phone to save and process the images. The nanodevice is scalable for mass production using standard manufacturing processes and materials used in the microelectronics industry.