Camera-Based Bipedal Plantar Pulse Transit Time Difference Measurement for Lower Limb Arterial Stenosis Detection

Area of Science:

• Biomedical Engineering
• Cardiovascular Diagnostics
• Medical Imaging

Background:

• Peripheral arterial disease (PAD) causes severe foot complications, including claudication and amputation.
• Current diagnostic methods like spectral Doppler ultrasound and Ankle-Brachial Index (ABI) are costly and inconvenient.
• A low-cost, convenient screening method for PAD is urgently needed.

Purpose of the Study:

• To propose and validate a novel, low-cost screening method for PAD using bipedal plantar pulse transit time difference (PTTD).
• To assess the accuracy of PTTD in detecting and grading simulated PAD conditions.
• To evaluate the clinical feasibility of PTTD in real-world settings.

Main Methods:

• A novel PAD screening method, PTTD, was developed, calculating the time difference between photoplethysmographic (PPG) signals from RGB videos of the feet.
• A simulation experiment involved 19 healthy subjects with induced vascular obstruction (simulating PAD) via calf pressure.
• Plantar video recordings were also collected from 10 PAD patients in a clinical setting.

Main Results:

• PTTD achieved 90.53% accuracy in detecting simulated PAD and 80.00% in grading five classes of simulated PAD.
• These results represent significant improvements over the baseline perfusion index (PI)-based models.
• The method demonstrated feasibility in real clinical settings with PAD patients.

Conclusions:

• Bipedal plantar pulse transit time difference (PTTD) is a sensitive indicator of vascular obstruction.
• PTTD shows promise as an efficient, low-cost, and convenient tool for peripheral arterial disease screening.
• The findings support the potential of PTTD for early detection and management of PAD.