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UBC Theses and Dissertations

Towards photoacoustic tomography for robot-assisted prostate imaging Moradi Kashkouli, Hamid


During prostate surgeries, there are critical structures around the prostate that should be preserved. Therefore, an additional intra-operative prostate cancer (PCa) imaging method is needed to help the surgeon localize the cancer. Photoacoustic (PA) imaging as an emerging imaging modality shows great potential to detect cancerous tissue. In this thesis, we focus on intra-operative PA imaging of the prostate using the da Vinci robotic system. Towards this objective, we developed a PA reconstruction technique that works in the presence of the challenges of the linear transducers. These challenges include the directivity effect of the transducer and limited-view PA imaging that cause the rank deficiency of the reconstruction system. Therefore, a sparse representation of the PA absorber distribution using the Discrete Cosine Transform was proposed. This sparse representation helps improve the numerical conditioning of the system of equations and reduces the computation time of the approach. In addition, we evaluated the feasible scanning configurations for intra-operative PA tomography (PAT) of the prostate. There are two ultrasound transducers that can be used in prostate PAT: a transrectal ultrasound (TRUS) transducer located posterior to the prostate, and a pick-up ultrasound transducer carried by the da Vinci robotic system and located anterior to the prostate. We proposed a PAT acquisition system that includes a da Vinci system controlled by the da Vinci Research Kit. The configurations using the pick-up and the TRUS transducers to perform intra-operative prostate PAT were investigated. Finally, we developed intra-operative prostate PA imaging using the da Vinci robotic system and a pick-up ultrasound transducer. We proposed a new approach in which the da Vinci robot is programmed to acquire trajectories in a shared control configuration with virtual fixtures; the pick-up transducer is manually controlled but virtual fixtures keep it parallel to a single tomography axis, and keep its translation fixed to a single plane normal to this axis. The surgeon controls the transducer motion on the tissue along this virtual fixture. This thesis confirms that intra-operative da Vinci robot-assisted PA imaging with a pick-up transducer is feasible.

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