Intraoperative zoom lens calibration for high magnification surgical microscope

Area of Science:

• Medical Imaging
• Surgical Technology
• Computer-Assisted Surgery

Background:

• Augmented reality (AR) surgical guidance systems require precise calibration for high-magnification microscopy.
• Conventional calibration methods fail with surgical microscopes due to narrow depth of focus at high magnifications.

Purpose of the Study:

• To develop a novel calibration method for AR surgical guidance compatible with high-magnification surgical microscopes.
• To achieve accurate intrinsic and hand-eye parameters for microscopes at all magnification levels.

Main Methods:

• Proposed a method establishing a constant relationship between focal length and hand-eye parameters, independent of magnification.
• Developed a dedicated calibration tool with a prism for focused pattern imaging.
• Recalculated parameters quickly and accurately using one or two pattern images.

Main Results:

• Achieved an augmented reality (AR) error of less than 1 mm across all magnification levels.
• Demonstrated a focal length variation within 1% regardless of magnification.
• Conventional methods showed over 20% variation at high magnifications.

Conclusions:

• The proposed calibration method offers superior accuracy and reproducibility for high-magnification surgical microscopes.
• This method is adaptable for various zoom lens-equipped endoscope and microscope systems.