A comparison study of photothermal effect between moxibustion therapy and laser irradiation on biological tissue

Moxibustion and laser irradiation are perceived to achieve satisfactory therapeutic effects by inducing photothermal effects on biological tissue. Understanding the photon transport and heat transfer process is an effective way to reveal their underlying mechanism. The temperature distribution of in-vitro tissue under gentle moxibustion and 808 nm laser irradiation were measured experimentally. Photon transport was simulated by Monte Carlo models. Heat transfer models on in-vitro tissue with convolved Monte Carlo results as heat sources were developed. During moxibustion, photons emitted from burning moxa stick with long-wavelength deposited in skin layer, which induced a maximum temperature on tissue surface. While for 808 nm laser irradiation, most photons penetrated through skin, which resulted in the highest temperature in fat tissue. Laser irradiation with big beam radius could induce a wide and relatively uniform thermal effect. During moxibustion and laser irradiation, the wavelength and beam radius have a significant influence on photons distribution as well as temperature profile in biological tissue. Laser irradiation with suitable parameters can be proposed as a substitution of moxibustion in terms of photothermal effect. This work would provide valuable guidance for understanding the photothermal mechanism of moxibustion and laser irradiation in the combined view of photon transport and heat transfer.