Non-contact methodology to detect surface displacements for photoacoustic imaging reconstruction

点击翻译按钮获取中文摘要

In commercial photoacoustic systems, a non-ionizing laser pulse propagates through media biomaterials or tissue and heats a target (i.e. optical absorbers in biomaterials, hemoglobin in tissue blood vessels). The absorbed heat by the target causes a transient thermal elastic expansion, which creates a pressure wave that propagates to the surface or skin through a coupling medium and that is detected by an ultrasound transducer to form an image of the target. There are many disadvantages of using such a coupling medium. First, the coupling medium can scatter and attenuate the light pulse and thereby reduce the pressure wave generated, decreasing the signal to noise ratio (SNR) of the system. Second, the coupling medium attenuates the pressure wave as it propagates through the coupling medium. Third, the use of a coupling medium is a step that can complicate an experimental set-up due to the low viscosity of the gel and the fact that it is hard to keep in stationary, which clinically, many patients find inconvenient, messy, and lengthens the imaging procedure. In this project, a more direct photoacoustic imaging system will be developed without using a coupling medium. A continuous laser beam will be focused on the surface. The surface's motion causes a Doppler shift in the reflected beam which can be detected using interferometry techniques. This technological development will also guide the subsequent design and construction of a laser interferometry photoacoustic system.