A microfabricated device for the in vivo measurement of prostate stiffness

We have developed a device for the in vivo assessment of soft tissue quality in the prostate. An assessment of prostate tissue quality is one of the first steps taken in diagnosing prostate cancer, typically via a Digital Rectal Examination (DRE). Studies of the histology and mechanical properties of benign and malignant prostate tissue show that malignant tissue is stiffer than healthy tissue [1]. Our device uses a silicone membrane with an embedded strain gauge. It applies a hydraulically or pneumatically actuated sinusoidal strain at actuation frequencies between 5 and 30 Hz, the most sensitive frequency range for soft tissue analysis [2]. This is used to measure the cyclic force transmitted through the soft tissue specimen. The amplitude ratio (|E*|) and phase difference (tan δ) between applied and measured cyclic strain estimate the stiffness and damping of the tissue [3]. Previous work used a hydraulic palpation device using a piston encoder and displacement transducer [2]. This device was functional but difficult to manufacture reliably. Our new device is simple to fabricate and can be easily used inside a surgical glove for instrumented DRE. Our paper will present stiffness measurements from our device on model systems at physiological driving frequencies. Data collected from the device will be used to demonstrate a correlation between tissue morphology and its mechanical characteristics. It is our aim to use this device to measure differences between benign, malignant and smooth muscle tissue to aid the diagnosis of prostate cancer. We also plan to miniaturise it for other soft tissue stiffness measurement applications.