Non-Linear Image Distortions in Flexible Fiberoptic Endoscopes and their Effects on Calibrated Horizontal Measurements Using High-Speed Videoendoscopy.
Hamzeh Ghasemzadeh, Dimitar D Deliyski
PMID 32958427WHAT IT FOUND
Flexible endoscopes distort images, making pixel size vary across the screen.
Measurements taken from the edges are less accurate than the center. Tilting the scope worsens this error, so keeping the target in the center and perpendicular is essential for reliable size estimates.
Key findings
01Pixel size is smallest at the center of the image and increases toward the periphery, meaning spatial resolution is lower at the edges.
02Tilting the endoscope moves the point of highest resolution away from the center and increases measurement errors on the side moving away from the camera.
03Using a single average pixel size for the whole image can overestimate object length in the center by up to 8.1% and underestimate it in the periphery by up to 14%.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study used static benchtop grids, not live human tissue, so real-world movement or tissue properties were not tested. The findings apply specifically to the flexible fiberoptic endoscope tested; rigid or distal-chip scopes may have different distortion profiles. The study focused on horizontal measurements; vertical distortions were not the primary focus.
The easy way to misread this
Do not assume that pixel counts are directly comparable across different parts of the image or between patients with different scope angles. A structure at the edge of the image is not measured with the same precision as one in the center.