Slope Chain Code-based scale-independent tortuosity measurement on retinal vessels

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Medical Imaging

Background:

• Retinal vascular tortuosity is a key biomarker for systemic and vascular diseases.
• Accurate measurement of tortuosity is crucial for clinical applications.
• Existing metrics may lack scale invariance, limiting their reliability across different imaging settings.

Purpose of the Study:

• To introduce a novel, scale-invariant metric for measuring retinal blood vessel tortuosity.
• To develop and present the SCALE-TORT database for evaluating scale invariance on real retinal vessel data.
• To compare the proposed metric against existing tortuosity measurement methods.

Main Methods:

• Developed a scale-invariant tortuosity metric based on the Extended Slope Chain Code.
• Created the SCALE-TORT database using semi-automated methods from paired retinal images (fundus camera and scanning laser ophthalmoscope).
• Evaluated ten tortuosity metrics, including the proposed one, through three experiments using synthetic and real retinal data.

Main Results:

• The Extended Slope Chain Code metric demonstrated optimal scale invariance and sensitivity to tortuosity changes.
• The SCALE-TORT database provides a valuable resource for assessing scale invariance in retinal imaging.
• The proposed metric offers easy implementation and reliable performance compared to other methods.

Conclusions:

• The novel Extended Slope Chain Code metric is a robust tool for assessing retinal vascular tortuosity.
• The SCALE-TORT database facilitates the validation of scale-invariant tortuosity metrics.
• This work advances the use of retinal vascular tortuosity as a reliable clinical biomarker.