Chitosan-diaphragm based optical-fiber hydrophone for in-vivo ultrasound measurements

The purpose of this work is the development of a high sensitivity and biocompatibility Fiber-Optic hydrophone for in-vivo ultrasound measurements. The selected sensing element-chitosan diaphragm allows matched-load condition due to its relatively permeable property. Chitosan is a natural polysaccharide which considered as biocompatible and biodegradable material that can be safe in performing the in-vivo measurement. The configuration of the sensor is based on the fiber-optic Fabry-Perot interferometry which offers good spatial resolution in the tens of MHz range [1] and robust response. Significant applications of the proposed sensor are in vivo micro-imaging [2], in-vivo lithotripsy measurement [3] or event the laboratory characterization of medical ultrasound sources. In this paper, the performance of the sensor is characterized by comparison with a PVDF needle hydrophone in term of sensitivity, frequency response and directivity.