Investigation of Accuracy of Peak-power Compensation in Fiber-Guided Acoustic-Resolution Photoacoustic Microscopy

Abstract

The photoacoustic imaging (PAI) technique has been gaining a lot of attention in the past two decades due to its high contrast, scalable resolution, and relatively high imaging depth. PAI can be used for structural and functional imaging as well as for investigating tissue hemodynamics. There are multiple categories of PAI, one of which is acoustic resolution photoacoustic microscopy (AR-PAM). This type of imaging system uses focused transducers to capture generated photoacoustic signals in depth from a focused line. Multimode optical fibers (MMF) are extensively used to transfer light to AR-PAM imaging scan-head due to the feasibility and the capability of carrying high-energy light pulses. Typically, peak-power-compensation (PPC) is used to reduce the effect of pulse-to-pulse peak-power variation which exists in most of the light sources. In MMF, the output intensity profile fluctuates due to the mode exchange caused by variations in the bending of the fibers. Also, the coherent nature of light produces a speckle pattern at the output of the fiber. Therefore, using a photodiode to capture the total power of pulses as a measure of illuminated light in acoustic focus is not appropriate for PPC. In this study, we have investigated the accuracy of PPC in fiber-guided systems under different conditions including the degree of focusing light in the clear and scattering medium. Based on obtained results, in order to apply the PPC method to the pulse variation problem, tightly focused light must be used. PPC method has shown to be more accurate in a clear medium than in a highly scattering medium.

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Speaker

Amir Asadollahi
Laser and Plasma Research Institute, Shahid Beheshti University, Tehran, Iran
Iran

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