A comparative study of analytical models of diffuse reflectance in homogeneous biological tissues: Gelatin-based phantoms and Monte Carlo experiments.

Information about tissue oxygen saturation (StO2) and other related important physiological parameters can be extracted from diffuse reflectance spectra measured through non-contact imaging. Three analytical optical reflectance models for homogeneous, semi-infinite, tissue have been proposed (Modified Beer-Lambert, Jacques 1999, Yudovsky 2009) but these have not been directly compared for tissue parameter extraction purposes. We compare these analytical models using Monte Carlo (MC) simulated diffuse reflectance spectra and controlled gelatin-based phantoms with measured diffuse reflectance spectra and known ground truth composition parameters. The Yudovsky model performed best against MC simulations and measured spectra of tissue phantoms in terms of goodness of fit and parameter extraction accuracy followed closely by Jacques' model. In this study, Yudovsky's model appeared most robust; however, our results demonstrated that both Yudovsky and Jacques models are suitable for modeling tissue that can be approximated as a single, homogeneous, semi-infinite slab.

Carpal Tunnel Decompression Under Wide Awake Local Anaesthesia No Tourniquet Technique (WALANT): A Cost Effective and Outcome Analysis.

Introduction Wide-awake local anaesthesia with no tourniquet (WALANT) technique is cost-effective, resource-friendly, and safe. This can be used as an alternative to hand surgery procedures in outpatient units. It can be performed in clinics or operating rooms. Methods We retrospectively evaluated the outcomes of WALANT for carpal tunnel decompression (CTD) over two years. Measured results include wound infections, relief of symptoms, paraesthesia, haematoma, Visual Analogue Scale (VAS), hospital anxiety and depression scale score (HADS) and cost-effectiveness. Results Eighteen patients underwent CTD under the WALANT technique over two years. VAS score was recorded at 3.1 ± 1.2 during the procedure and 1.67 ± 0.933 at two weeks follow-up. Persistent paraesthesia was found in only one patient at follow-up. Minimal bleeding was recorded during the procedure. No wound infections, revision surgery or post-operative haematoma formation were found. Hospital Anxiety and Depression Scale (HADS) was reported as 4.77 ± 2.1 after surgery. WALANT was also cost-effective, with an overall amount of £20. Conclusion Performing carpal tunnel decompression under WALANT in one stop upper limb clinic is a safe and cost-effective technique with no significant patient-related complications.