Tactile resonant sensors for the measurement of human soft tissue stiffness
Professor Olof A Lindahl
Department of Radiation Sciences/ Biomedical Engineering, Center for Biomedical Engineering and Physics, Umeå University, S-901 87 UMEÅ, Sweden
Resonant sensors consist usually of piezoelectric transducers made from PZT (Lead Zirconate, Titanium). They have a mechanical resonance frequency or relative phase of oscillation that is dependent on the measured parameter of interest. The sensors are used to develop measurement systems in industry as well as in medicine. Sensor systems in medicine include for example detection of prostate and breast cancer, measurement of muscular elasticity, measuring stiffness of human ovum and also for modelling micturition characteristics based on prostate stiffness. In other studies it has been shown that pitting oedema and elasticity or spring constant of human skin could be estimated with a tactile resonant sensor combined with measurement of force and position. Resonant sensors may also be used in tele-surgery to give haptic feedback to the surgeon.
An instrument has been developed based on resonant sensors for measuring the intraocular pressure (IOP) in the human eye that is today a clinical product (BR Good Eye Co Ltd). Ongoing research concerns the use of resonant sensors to detect stiffness of human prostate with the aim to detect prostate cancer in in-vitro preparations of prostate tissue and thereby aid in the surgical procedure of safe removal of prostate. For the purpose there is also developed a Micro Tactile Sensor (MTS) system, based on the same resonant principle, which can detect stiffness differences on thin slices of prostate tissue. Those measurements are compared with Raman spectroscopy and morphometry (histology). The use of resonant sensors in health care applications is challenging and of great interest, e.g. when biomechanical parameters like contact area and/or stiffness of human organs are to be estimated for clinical diagnosis. The presentation will give an overview of current methods and applications in medicine.