Investigating Transducer-Tissue Interface Pressure for Soft Tissue Stress-Strain Behavior and the Effects on Echoic Intensities in Ultrasound Imaging of Periodontium

Diagnostic ultrasound (US) is a major imaging modality to visualize soft tissues and blood flow with the advantages of real-time imaging, high acceptability to patients, and absence of ionizing radiation. US imaging provides important clinical measurements, e.g., thickness of gingiva for treatment planning in orthodontics, periodontics, and implantology; or thickness of subcutaneous adipose for optimizing insulin injection. However, the image quality and measurements of anatomical structures can be inconsistent, i.e., due to varying pressure exerted by an US transducer. Herein, a simple device is developed to real-time measure the interface pressure applied on tissues by the US transducer. A thin-film piezo-resistive sensor with a small footprint is integrated to sense the pressure. A theoretical model, based on hyperelastic material behavior, is verified using the pressure measured by the thin film sensor and the thickness determined on ultrasonograms. The device is also tested on porcine samples in the pressure range of 50-300 kPa for imaging gingiva boundaries, identifying tissue thickness, and probing tissue biomenchanical properties. The device enables the understanding on the optimal range of applied pressure for higher contrast imaging. The information of the on-tissue pressure and the tissue deformation determined on the US images help to derive the biomechanical stress-strain behavior of the tissues. A device simultaneously acquires ultrasound images and measures interface pressure between the transducer and tissues. The measured pressure in couple with the ultrasonography-derived thickness is used to study the biomechanical properties of the soft tissue. The effects of pressure on the echoic intensity of the tissue boundary are investigated for image quality. image