Ratiometric Laser-Induced Fluorescence (LIF) Thermography of Radiofrequency Heated Tissue Phantoms

A ratiometric laser-induced fluorescence (LIF) thermographic method has been developed to quantify the temperature fields associated with radiofrequency (RF) heating probes used to treat joint instabilities associated with the shoulder, knee, and ankle. Accurate temperature field measurements in tissue phantoms represent invaluable data for the purpose of developing and verifying computer models of tissue heating. Measuring temperature fields associated with RF probe heating in physiological environments poses problems for traditional methods. Thermocouples, infrared thermometry and fluoroptic methods are limited due to inability of thermocouples to operate in an RF environment, the opaque nature of physiological solutions to IR wavelengths and the relatively large size of optical fibers used in fluoroptic thermometry respectively. Whole field temperature mapping and heat flux measurements around monopolar and bipolar radiofrequency (RF) probes have been performed in tissue phantoms using two-color laser induced fluorescence (LIF) and the ratio of the fluorescent emission intensities of Rhodamine B and Rhodamine 110. The method is described, the operating characteristics are defined and examples of the application of the method to radiofrequency (RF) heating in phantom tissues are included.