Selective Photothermolysis of Lipid-Rich Tissues: A Free Electron Laser Study

Background and Objectives: In theory, infrared vibrational bands could be used for selective photothermolysis of
lipid-rich tissues such as fat, sebaceous glands, or atherosclerotic plaques. Study Design/Materials and Methods: 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 mm thermal camera during exposure to the free electron laser (FEL) at Jefferson National Laboratory. Thermal damage to full-thickness samples exposed at 1,210 nm through a cold contact window, was assessed by nitrobluetetrazolium chloride staining in situ and by light microscopy. Results: 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.
 Conclusion: Selective photothermal targeting of fatty tissues is feasible using infrared lipid absorption bands. Potential clinical applications are suggested by this FEL study.