Conception et caractérisation d’un système d'imagerie photoacoustique pour application biomédicale

The biomedical imaging domain is still looking for an imaging modality which will be able to visualize the human body’s anatomy as well as specific metabolic markers. Photoacoustic imaging attempts to respond to this demand by capitalizing on the advantages of both optical and ultrasound imaging, which are good spatial resolution and excellent contrast. Photoacoustic brings functional information through its sensitivity to exogenous contrast agents and structural information through coregistration with ultrasound images. Consequently, a photoacoustic imaging system was developed herein. This master’s project has proposed itself to contribute to the conception, characterization and optimization of such a system. The physical bases of the signal creation phenomenon were explored in detail to retrieve the equations which govern the image reconstructions. A preexisting photoacoustic imaging system consisting of a focalized single element transducer was improved. A second version using a VeraSonics data acquisition system architecture and medical ultrasound probes was elaborated. Numerical simulations modeling both systems were implemented and tested. These simulations testified the accuracy of the pre-derived mathematical equations. These reconstruction algorithms were utilized to visualize human hairs imbedded in an almost opaque biological phantom at more than one centimeter of depth and thus validating the imaging system. The problem of the retrieval of quantitative measures from experimental data was exposed. A method to resolve this difficulty was proposed and results were obtained. In vivo measures on mice demonstrated the ability to identify structures at depths of more than 2 cm.