Development of a camera model and calibration procedure for oblique-viewing endoscopes

Area of Science:

• Medical Imaging
• Robotics
• Computer Vision

Background:

• Oblique-viewing endoscopes (oblique scopes) are crucial for minimally invasive surgeries like laparoscopy, arthroscopy, and sinus endoscopy.
• Current augmented reality (AR) applications in endoscopy are limited by the lack of calibration methods for oblique scopes.

Purpose of the Study:

• To develop and validate a novel camera calibration procedure specifically for oblique scopes.
• To enable the integration of augmented reality technologies into procedures utilizing oblique endoscopic visualization.

Main Methods:

• A camera model for oblique scopes was formulated.
• Tsai's calibration method was adapted, initially performed at zero rotation.
• External camera parameters were modeled and estimated as a function of scope cylinder rotation angle, incorporating accurate rotational axis estimation.

Main Results:

• The proposed calibration method achieved a projection error of approximately two pixels.
• Accurate estimation of the rotational axis significantly impacted overall calibration accuracy, especially at large rotation angles.
• Experimental evaluation demonstrated the clinical applicability of the developed calibration technique.

Conclusions:

• A robust camera calibration method for oblique scopes has been successfully developed.
• This method facilitates the use of augmented reality in various endoscopic procedures.
• The findings pave the way for enhanced visualization and guidance in minimally invasive surgery.