Coaxial ultrasound-modulated optical spectroscopy in scattering medium

Abstract

Ultrasound-modulated optical spectroscopy within a coaxial system capable of attaining submillimeter spatial resolution has been developed to investigate scattering media spectroscopic properties at depths of several centimeters. By using stroboscopic illumination methods, a broad spectral bandwidth pulsed laser and a focused ultrasound pulse simultaneously irradiated a biological tissue phantom containing oxyhemoglobin and deoxyhemoglobin absorbers. The ultrasound-modulated optical spectroscopic images were synchronously acquired by a fiber optic spectrometer scanning in two dimensions. We have obtained the wavelength dependent ultrasound-modulated optical signals produced by the ultrasound interactions changing the distribution of scattered light through several different mechanisms and evaluated the proposed system.

Light Scattering Characteristics of Biological Tissues in Coaxial Ultrasound-Modulated Optical Tomography

“…In particular, ultrasound-modulated optical measurement techniques have the potential for observing optical tissue structures at depths of several centimeters, with spatial resolutions of a few submillimeters. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Visualization of internal structures from acoustically impedance-matched tissues is also possible, a capability unattainable in ultrasonography. Thus, a very important medical application of this technique is that cancerous lesions could be revealed at an earlier stage.…”

“…Several groups have examined this measurement with a single photodetector [1][2][3][4][11][12][13] as well as the parallel speckle measurement with a charge-coupled device (CCD) camera [5][6][7][8][9]13) for detecting the ensuing modulated optical signals. The modulation signals have been examined by coaxial systems [12][13][14] as well as with orthogonal systems, [1][2][3][4][5][6][7][8][9][10][11] where the optical axis is perpendicular to the propagation of the ultrasound wave. In addition, pulsed-ultrasound propagation technology [12][13][14] and ultrasound frequency sweep technology 4) have also been explored as ways of obtaining depth resolution in the sample.…”

“…The modulation signals have been examined by coaxial systems [12][13][14] as well as with orthogonal systems, [1][2][3][4][5][6][7][8][9][10][11] where the optical axis is perpendicular to the propagation of the ultrasound wave. In addition, pulsed-ultrasound propagation technology [12][13][14] and ultrasound frequency sweep technology 4) have also been explored as ways of obtaining depth resolution in the sample. For the aim of practical medical applications, our group developed a coaxial ultrasoundmodulated optical tomography system with parallel speckle detection that has the advantages of coaxial illumination generated from ultrasound waves and light photons, along with a reflection configuration, axial discrimination, and high signal to noise ratio detection.…”