Assessment of thermal coagulation in ex-vivo tissues using Raman spectroscopy

Raman spectroscopy is used to study the effects of heating on specific molecular bonds present in albumen-based coagulation phantoms and ex-vivo tissues. Thermal coagulation is induced by submerging albumen-based phantoms in a 75°C water bath to achieve target temperatures of 45, 55, 65, and 75°C. Laser photocoagulation is performed on ex-vivo bovine muscle samples, yielding induced temperatures between 46 and 90°C, as reported by implanted microthermocouples. All phantoms and tissue samples are cooled to room temperature, and Raman spectra are acquired at the microthermocouple locations. Shifts in major Raman bands are observed with laser heating in bovine muscle, specifically from the amide-1 α-helix group (∼1655 cm(-1)), the CH(2)/CH(3) group (∼1446 cm(-1)), the Cα-H stretch group (∼1312 cm(-1)), and the CN stretch group (∼1121cm(-1)). Raman bands at 1334 cm(-1) (tryptophan), 1317 cm(-1) [ν(Cα-H)], and 1655 cm(-1) (amide-1 α-helix) also show a decrease in intensity following heating. The results suggest that Raman band locations and relative intensities are affected by thermal denaturation of proteins, and hence, may be a useful tool for monitoring the onset and progression of coagulation during thermal therapies.