Abstract
This paper presents a novel intuitive targeting and tracking scheme that utilizes a common-path swept source optical coherence tomography (CP-SSOCT) distal sensor integrated handheld microsurgical tool. To achieve micron-order precision control, a reliable and accurate OCT distal sensing method is required; simultaneously, a prediction algorithm is necessary to compensate for the system delay associated with the computational, mechanical and electronic latencies. Due to the multi-layered structure of retina, it is necessary to develop effective surface detection methods rather than simple peak detection. To achieve this, a shifted cross-correlation method is applied for surface detection in order to increase robustness and accuracy in distal sensing. A predictor based on Kalman filter was implemented for more precise motion compensation. The performance was first evaluated using an established dry phantom consisting of stacked cellophane tape. This was followed by evaluation in an ex-vivo bovine retina model to assess system accuracy and precision. The results demonstrate highly accurate depth targeting with less than 5 μm RMSE depth locking.
Highlights
Accurate and precise tool tip manipulation is imperative when performing microsurgery
The parallel processing (CUDA, Nvidia) of the GPGPU can reduce the processing time considerably in fast Fourier transform (FFT), background noise subtraction and averaging, which is mainly responsible for the processing delay [24, 25]
The failure rate without the shifted cross-correlation method was 28 incidents/s and 0.3 incidents/s with the shifted cross-correlation method. These results clearly indicate that the addition of the shifted cross-correlation methodology can greatly improve the stability of the Optical coherence tomography (OCT) distal sensor
Summary
Accurate and precise tool tip manipulation is imperative when performing microsurgery. Retinal microsurgery is performed by passing microsurgical tools through trocars that provide access through the eye wall (sclera). The trocar provides safe access into the eye but it guides and stabilizes the surgical tools and acts as a remote center of motion (RCM). The freehand tool movements are guided predominantly by visual information acquired from the surgeon’s view in the operating microscope. Such tool tip visualization is limited in the axial direction by the ability to resolve small changes in position as well as by obstruction of the retinal surface by the tool shaft and tip. Diverse active tool-tips and sensors have been applied to the system to enhance its functionality [8,9]
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