Selective photothermolysis of lipid-rich tissues: A free electron laser study

Abstract

In theory, infrared vibrational bands could be used for selective photothermolysis of lipid-rich tissues such as fat, sebaceous glands, or atherosclerotic plaques. Absorption spectra of human fat were measured, identifying promising bands near 1,210 and 1,720 nm. Photothermal excitation of porcine fat and dermis were measured with a 3.5-5 microm thermal camera during exposure to the free electron laser (FEL) at Jefferson National Laboratory. Thermal damage to full-thickness samples exposed at approximately 1,210 nm through a cold contact window, was assessed by nitrobluetetrazolium chloride staining in situ and by light microscopy. Photothermal excitation of fat was twice that of dermis, at lipid absorption bands (1,210, 1,720 nm). At 1,210 nm, a subcutaneous fat layer several mm thick was damaged by FEL exposure, without apparent injury to overlying skin. Selective photothermal targeting of fatty tissues is feasible using infrared lipid absorption bands. Potential clinical applications are suggested by this FEL study.