Water flow elastography - A promising tool to measure tissue stiffness during minimally invasive surgery

Mechanical properties are important markers for pathological processes in tissue. Elastography techniques are therefore becoming more and more useful for diagnostics. In minimally invasive surgery (MIS), however, the probe size is limited and the handling is restricted, thereby excluding the application of most established elastography techniques. In this paper we introduce water flow elastography (WaFE) as a new technique that benefits from a small and inexpensive probe. This probe flows pressurized water against the sample surface to locally indent it. The volume of the indentation is measured with a flow meter. We use finite element simulations to find the relation between the indentation volume, the water pressure, and the Young's modulus of the sample. We used WaFE to measure the Young's modulus of silicone samples and porcine organs, finding agreement within 10% to measurements with a commercial material testing machine. Our results show that WaFE is a promising technique for providing local elastography in MIS.