Abstract
The unique ability of photoacoustic (PA) sensing to provide optical absorption information of biomolecules deep inside turbid tissues with high sensitivity has recently enabled the development of various novel diagnostic systems for biomedical applications. In many cases, PA setups can be bulky, complex, and costly, as they typically require the integration of expensive Q-switched nanosecond lasers, and also presents limited wavelength availability. This article presents a compact, cost-efficient, multiwavelength PA sensing system for quantitative measurements, by utilizing two high-power LED sources emitting at central wavelengths of 444 and 628 nm, respectively, and a single-element ultrasonic transducer at 3.5 MHz for signal detection. We investigate the performance of LEDs in pulsed mode and explore the dependence of PA responses on absorber’s concentration and applied energy fluence using tissue-mimicking phantoms demonstrating both optical absorption and scattering properties. Finally, we apply the developed system on the spectral unmixing of two absorbers contained at various relative concentrations in the phantoms, to provide accurate estimations with absolute deviations ranging between 0.4 and 12.3%. An upgraded version of the PA system may provide valuable in-vivo multiparametric measurements of important biomarkers, such as hemoglobin oxygenation, melanin concentration, local lipid content, and glucose levels.
Highlights
Even though PA systems present a rich potential for diagnostic biomedical applications, they are usually developed in the form of sensitive, complex, and bulky laboratory setups utilizing light pulses emitted by high-cost Q-switched nanosecond lasers, with limited wavelength availability
We had initially characterized the optical performance of light emitting diodes (LED) sources when overdriven with the diode laser driver (DLD) and attempted to determine the optimum parameters for maximizing
It was observed that current pulses with an optimum Full Width at Half Maximum (FWHM) of 175 and 260 ns could provide approximately equal duration optical pulses of ~560 ns, when overdriving SST90B (Blue) (Figure 2a) and SST90R (Red) (Figure 2b) LEDs, respectively
Summary
The ability of PA sensing to provide molecular absorption specificity [3], and the low attenuation of PA waves [4], provide unique advantages towards developing novel systems for biomedical imaging and sensing applications that can obtain valuable diagnostic information deeper in highly scattering tissues when compared to pure optical imaging approaches [5] In this direction, special emphasis has been given to developing reconstruction-based PA tomography (PAT) [6], PA microscopy (PAM) [7], or even hybrid imaging systems integrating both PA and optical [8,9,10], or ultrasound [11] techniques into a single instrument. High pulse repetition rates (PRR) of several KHz can be achieved, providing sufficient signal averaging at reasonable times for a substantial
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