Medical-grade Sterilizable Target for Fluid-immersed Fetoscope Optical Distortion Calibration

Abstract

We have developed a calibration target for use with fluid-immersed endoscopes within the context of the GIFT-Surg (Guided Instrumentation for Fetal Therapy and Surgery) project. One of the aims of this project is to engineer novel, real-time image processing methods for intra-operative use in the treatment of congenital birth defects, such as spina bifida and the twin-to-twin transfusion syndrome. The developed target allows for the sterility-preserving optical distortion calibration of endoscopes within a few minutes. Good optical distortion calibration and compensation are important for mitigating undesirable effects like radial distortions, which not only hamper accurate imaging using existing endoscopic technology during fetal surgery, but also make acquired images less suitable for potentially very useful image computing applications, like real-time mosaicing. In this paper proposes a novel fabrication method to create an affordable, sterilizable calibration target suitable for use in a clinical setup. This method involves etching a calibration pattern by laser cutting a sandblasted stainless steel sheet. This target was validated using the camera calibration module provided by OpenCV, a state-of-the-art software library popular in the computer vision community.

Computer‐assisted fetal laser surgery in the treatment of twin‐to‐twin transfusion syndrome: Recent trends and prospects

“…In addition, a relocalization module, multimapping, or dynamic method will help if tracking is lost due to rapid fetoscopic movements or fetal parts moving to the field of view. Finally, it was remarkable that most researchers did not take the fetoscopic camera's optical distortions into account, while approaches for fluid‐immersed fetoscopic camera calibration have been proposed 43,44 …”

“…Finally, it was remarkable that most researchers did not take the fetoscopic camera's optical distortions into account, while approaches for fluid-immersed fetoscopic camera calibration have been proposed. 43,44 Difficulties arise, however, when an attempt is made to implement the techniques in clinical practice. In addition, a lack of ground truth and big datasets may hinder the fast development of deep learning techniques.…”

Refractive Two-View Reconstruction for Underwater 3D Vision

“…We then followed the same procedure to calibrate the stereo-endoscope under water considering as such the adapted pinhole camera model (Nikitichev et al. 2017 ). We used the same set of underwater images to calibrate the orientation and distance of the flat refractive plane considering the flat refractive camera model (Agrawal et al.…”

“…We used a planar checkerboard and estimated both internal camera parameters and rigid pose between the cameras pair (Zhang 2000). We then followed the same procedure to calibrate the stereo-endoscope under water considering as such the adapted pinhole camera model (Nikitichev et al 2017). We Fig.…”