Tissue optical properties correction of multispectral singlet oxygen luminescent dosimetry (MSOLD) for BPD-mediated Photodynamic Therapy

Direct detection of singlet-state oxygen (¹O₂) is vital for type II PDT and achievable through multispectral singlet oxygen dosimetry (MSOLD). However, tissue scattering and absorption variations impact signal accuracy, necessitating correction factors. A 690 nm CW laser (500 mW/cm²) excited Benzoporphyrin derivative (BPD) in methanol. The singlet oxygen spectrum was decomposed into ¹O₂ signal, BPD luminescence, and laser background using Singular Value Decomposition (SVD). Measurements were conducted in phantoms with varying optical properties: ink (= 0.1 – 1 cm⁻¹) and intralipid (= 5 – 40 cm⁻¹). Monte Carlo simulations validated the results. The ¹O₂ signal decreased nearly linearly with, while effects were influenced by detection fiber positioning. Experimental and simulated results showed strong agreement. This study provides correction factors to enhance MSOLD accuracy under varying optical conditions, advancing its clinical application in PDT.