Dependence of Photothermal Responses on Wavelengths

Abstract

The goal of the current research is to identify dependence of photothermal responses on wavelengths for diffuser-assisted treatment of liver tumor. For interstitial photothermal treatment, four commercially available wavelengths were tested: 532, 808, 980, and 1470 nm. A thermal camera was employed to record spatio-temporal development of temperature in porcine liver tissue. Spatial distribution of temperature and coagulation was quantitatively evaluated at various irradiation times. Both 808 and 980 nm presented a comparable maximum temperature after delivery of 200 J. On the other hand, both 532 and 1470 nm induced the higher maximum temperatures of over 90 °C along with a wider thermal distribution. The degree of the coagulation for both 532 and 1470 nm was quite consistent along the diffusing tip as various distances showed the comparable coagulation thickness. Both 808 and 980 nm presented the varying degree of the coagulation (1 ~ 2 mm in thickness). The largest volume along the thickest radial coagulation was observed after 1470 nm laser irradiation (606.9 ± 21.0 mm³) whereas the smallest volume was created by 980 nm (77.1 ± 13.3 mm³). The current results demonstrated that due to strong light absorption, both 532 and 1470 nm could be the feasible wavelengths for the treatment of liver tumor.