Toward virtual biopsy through an all fiber optic ultrasonic miniaturized transducer: a proposal

Abstract

The present generation of devices based on opto-acoustic and acousto-optic conversion lets us foresee the possibility of realizing complete miniaturized transmitting-receiving transducers, able to generate and detect wideband ultrasounds by laser light. In the present paper, a miniaturized ultrasonic transducer entirely based on fiber optic technology is proposed. Such a device springs from the conjunction between our research, which has produced a highly efficient fiber optic opto-acoustic source, with the results obtained by other researchers concerning the realization of an ultrasonic receiver based on optical interferometry. Making use of the thermo-elastic effect for ultrasound generation, a source of ultrasound can be obtained by coupling a fiber optic to pulsed laser, if a film capable of absorbing laser light is placed onto fiber end. Starting from these remarks, we propose an efficient opto-acoustic source, able to generate pressure pulses with amplitude of the order of 10 4 Pa and bandwidth extending up to 40 MHz and beyond by using graphite materials as absorbing film. This solution makes use of a low-power pulsed laser as optical source possible. An ultrasonic receiving element was realized placing a Fabry-Perot cavity over the tip of a fiber optic. The cavity thickness modulation induced by ultrasonic beam is detected by an interferometer optical technique. We have realized a prototype of a receiving device that exhibits a sensitivity comparable with that of piezoelectric devices (10-100 nV/Pa) and an almost flat bandwidth extending up to 20 MHz or more. The extreme miniaturization of the resulting ultrasonic transducer, together with its wide ultrasonic frequency bandwidth, is the first step toward ultrasonic tissue biopsy. In this paper, before discussing the problem of constructing a complete ultrasonic transducer composed by a transmitter and receiver, the results carried out in these fields during the last decade are reviewed.

Laser-generated ultrasound with optical fibres using functionalised carbon nanotube composite coatings

“…4 Composite media that include distinct elastomeric and absorbing components have emerged as particularly efficient optical transducers. Several absorbers have been considered, including gold nanostructures, 5 carbon black, 6 graphite, 7,8 graphene, 9 and carbon nanotubes (CNTs). 10 The use of polydimethylsiloxane (PDMS) as an elastic component with a large thermal expansion coefficient was highlighted in several studies.…”

Fabrication of fiber-optic broadband ultrasound emitters by micro-opto-mechanical technology

“…Such probes might contribute to the research work carried out by several groups worldwide and be directed to the achievement of virtual biopsy by ultrasound analysis. According to recent developments, in fact, wide-band ultrasonic transducers could be placed in close proximity of a tumour by using a catheter or a needle and provide the possibility of investigating the health conditions of small portions of living tissue in situ [21].…”

Fiber Optic Broadband Ultrasonic Probe for Virtual Biopsy: Technological Solutions

“…Such probes might make it possible to trace a path towards "virtual biopsy"; in fact, these wide band ultrasonic fiber optic probes could be placed in close proximity of a focal lesion by a catheter or a needle [11].…”