Endoscopic inspection of the bladder is called cystoscopy, and over 1 million are performed annually in the USA.1 Robotic assistance of the procedure is being considered to overcome healthcare disparities due to geographic distances. To ensure safety, real-time navigation by simultaneous localization and mapping (SLAM) of the cystoscope in the bladder is desired. However, the near-featureless bladder wall and irregular movement of the monocular cystoscope by manual operation has made SLAM-based navigation a difficult challenge. In this work we develop a robot-assisted approach in a bladder phantom using a commercial flexible cystoscope. With this simple remote-controlled robot, we have succeeded in creating a series of real-time 2.5D reconstructions of the bladder interior wall. In post-processing, we combine those 2.5D results and achieve a 3D reconstruction. We compared SLAM performance using the robot and manual control under different scanning speeds. In comparison to manual control using the same cystoscope at 1x, 2x and 3x speeds, the robotic-assistance provides significantly more robust and accurate reconstructions of the camera trajectories and bladder wall locations in real-time.
Purpose: Handling low-quality and few-feature medical images is a challenging task in automatic panorama mosaicking. Current mosaicking methods for disordered input images are based on feature point matching, whereas in this case intensity-based registration achieves better performance than feature-point registration methods. We propose a mosaicking method that enables the use of mutual information (MI) registration for mosaicking randomly ordered input images with insufficient features.
Approach: Dimensionality reduction is used to map disordered input images into a low dimensional space. Based on the low dimensional representation, the image global correspondence can be recognized efficiently. For adjacent image pairs, we optimize the MI metric for registration. The panorama is then created after image blending. We demonstrate our method on relatively lower-cost handheld devices that acquire images from the retina in vivo, kidney ex vivo, and bladder phantom, all of which contain sparse features.
Results: Our method is compared with three baselines: AutoStitch, “dimension reduction + SIFT,” and “MI-Only.” Our method compared to the first two feature-point based methods exhibits 1.25 (ex vivo microscope dataset) to two times (in vivo retina dataset) rate of mosaic completion, and MI-Only has the lowest complete rate among three datasets. When comparing the subsequent complete mosaics, our target registration errors can be 2.2 and 3.8 times reduced when using the microscopy and bladder phantom datasets.
Conclusions: Using dimensional reduction increases the success rate of detecting adjacent images, which makes MI-based registration feasible and narrows the search range of MI optimization. To the best of our knowledge, this is the first mosaicking method that allows automatic stitching of disordered images with intensity-based alignment, which provides more robust and accurate results when there are insufficient features for classic mosaicking methods.
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