Music-of-light stethoscope: a demonstration of the photoacoustic effect

Abstract

In this paper we present a system aimed at demonstrating the photoacoustic (PA) effect for educational purposes. PA imaging is a hybrid imaging modality that requires no contrast agent and has a great potential for spine and brain lesion characterisation, breast cancer and blood flow monitoring notably in the context of fetal surgery. It relies on combining light excitation with ultrasound reception. Our brief was to present and explain PA imaging in a public-friendly way suitable for a variety of ages and backgrounds.We developed a simple, accessible demonstration unit using readily available materials. We used a modulated light emitting diode (LED) torch and an electronic stethoscope. The output of a music player was used for light modulation and the chest piece of the stethoscope covered by a black tape was used as an absorbing target and an enclosed chamber.This demonstration unit was presented to the public at the Bloomsbury Festival On Light in October 2015. Our stall was visited by over 100 people of varying ages. Twenty families returned in-depth evaluation questionnaires, which show that our explanations of the photoacoustic effect were well understood. Their interest in biomedical engineering was increased.

Phasor representation for the nonlinear photoacoustic signal

“…It also shows the constant f form equation 3 The minimum of R T will be found when the phasors R T and R 2 are perpendicular. In this condition, the phase (θ m ) of phasor R T can be calculated using equation (5). This θ m can also be observed directly in figures 3(a), (b) and 4(a).…”

A Comprehensive Review on Photoacoustic-Based Devices for Biomedical Applications

“…The sound waves produced during the speech cause mirror vibrations, varying the intensity of the light detected in the receiver. In the telephone circuit, those variations in the light intensity give rise to a sound wave [ 12 , 55 , 67 , 68 , 69 , 70 , 71 ].…”

Self-Assembled Organic Nanomaterials for Drug Delivery, Bioimaging, and Cancer Therapy

“…Among different diagnostic modalities, PAI enables imaging that exceeds the optical diffusion limit by detecting phonons instead of photons, offering higher spatiotemporal resolution as well as deeper tissue penetration over conventional optical imaging techniques. , As above-illustrated in Figure , the nonradiative vibrational relaxation upon photoexcitation could be utilized for PAI. In a typical photoacoustic process, three essential steps are required: (1) light absorption; (2) ultrasound generation; and (3) ultrasound detection (Figure a) . To be specific, a nonionizing electromagnetic pulse (e.g., laser) is first applied to irradiate the PAI agents.…”

“…In a typical photoacoustic process, three essential steps are required: (1) light absorption; (2) ultrasound generation; and (3) ultrasound detection (Figure 12a). 131 To be specific, a nonionizing electromagnetic pulse (e.g., laser) is first applied to irradiate the PAI agents. Some of the delivered electromagnetic energy will be absorbed and converted into heat by the PAI agents, leading to transient thermoelastic expansion and thus generated ultrasound could eventually be detected by ultrasonic transducers to output photoacoustic images.…”

“…(a) Illustration of the photoacoustic effect. Reproduced with permission from ref . Copyright 2016 IOP Publishing Ltd.. (b) Absorption coefficient of endogenous tissue chromophores as a function of wavelength in the 400–1400 nm region.…”