Elastic property attributes to photoacoustic signals: an experimental phantom study

Abstract

We report an experimental study that shows the attribution of the elastic property of light absorbing targets to the generation of ultrasound signals induced due to the photoacoustic effect. We investigated the variation in strength of the detected photoacoustic signals for various targets embedded in a background phantom with: (1) different elastic coefficients (94-346 kPa) and (2) various sizes (0.25-1.5 mm²). The results show that photoacoustic signals increase with an increase in elastic coefficient (i.e., showing to contrast in elastic property) while it is independent of variation in target sizes. Quantitative (analysis) study, and 2D and 3D reconstructed images are also presented. This study demonstrates the feasibility of imaging elastic property using photoacoustic technique.

Photoacoustic elastography imaging: a review

“…[76][77][78][79][80][81][82][83] Recently, research studies were reported for possible recovery of the elastic property of soft biological tissue with PA imaging technology. [84][85][86][87][88][89][90][91][92] This innovative study enhances the horizon of potential applications of PA imaging extending to diagnosis and therapeutic treatment of life-threatening diseases (such as breast and prostate cancer, 4 brain tumor, 93 and Alzheimer's diseases 94 ) that induce contrast in elasticity relative to normal tissues. Currently, PA elastography (PAE) imaging is limited only to qualitative study, and it is in the nurture stage of development.…”

“…84 In this study, a phase-resolved technique was employed. Singh and Jiang 85 reported an experimental study that demonstrates attribution of elastic properties of light absorbing targets to the generation of ultrasound signals induced due to PA effect, i.e., generation of acoustic waves upon illumination of a sample material by a short duration (ns) pulse optical beam. The study investigated variation in the strength of PA signals for various targets, with different elastic coefficients and various sizes, embedded in a background phantom.…”

“…PA imaging is, fundamentally, based on PA effect, which is the generation of mechanical (sound) waves in a sample material associated with illumination of electromagnetic (EM) radiation for a short duration, [132][133][134] i.e., it is a phenomenon of the generation of acoustic waves due to transient absorption of EM energy and the subsequent rapid heating in a material sample irradiated with EM waves. 85 The entire process of the effect can be subgrouped into three distinct stages: (1) transient irradiation of tissue sample of interest with EM (light) waves, (2) generation of mechanical (acoustic) waves in a wide range of frequency (Hz to GHz), 132,135 and 3propagation of PA waves.…”

“…This absorbed energy is converted into heat energy through vibrational and oscillational relaxation of constituent particles/molecules of the medium, therefore resulting in a localized rise of temperature over the radiation-irradiated tissue region. 85 For a given intensity of the incident optical (laser) beam, initial rise of temperature [ΔTðrÞ] is dependent on μ a ðrÞ. Due to rapid heating, associated with transient illumination of radiation under the constraint of illumination duration to be less than time scales of thermal and stress confinements, irradiated tissue undergoes thermoelastic expansion 99 inducing a transient rise in pressure.…”

Interstitial photoacoustic technique and computational simulation for temperature distribution and tissue optical properties in interstitial laser photothermal interaction

“…18,19 PA tomography has been applied for noninvasive temperature measurement, since the PA signal amplitude is linearly dependent on temperature in the range from 10 C-55 C. 18,20,21 In addition, a dual-wavelength PA technique has been developed to monitor tissue optical properties during thermal treatment, based on the observation that the ratio of PA signals generated by the two wavelengths is independent of temperature. 23 However, most studies focus only on measured PA signals in the sample boundary 24 with enhanced light absorption in target tissue. 18 The PA response from tissues far from the boundary or without photoabsorbers often has low signal intensity.…”