Fluorescence spectroscopy accurately detects irreversible cell damage during hepatic radiofrequency ablation

Abstract

A current limitation of hepatic radiofrequency ablation (RFA) is an inability to detect ablation margins in real time. Thermal injury from RFA alters the biochemical properties governing tissue fluorescence. We hypothesized that the changes in hepatic fluorescence measured during hepatic RFA could be used to detect irreversible hepatocyte damage accurately and to determine ablation margins in real time. RFA was performed on healthy pig livers and monitored in vivo simultaneously for fluorescence and temperature by a fiberoptic micro-interrogation probe connected to a spectroscopy system. Ablations were stopped based on previously established real-time fluorescence spectral data, not based on temperature or time. To determine where in the ablated tissue cell death occurred, biopsies for transmission electron microscopy were taken from 4 areas of 3 specimens: (1) nonablated liver, (2) hemorrhagic zone/normal liver interface, (3) hemorrhagic zone/coagulated zone interface, and (4) coagulated zone. In vitro fluorescence emission intensity was determined at each biopsy site. Peak hepatic fluorescence intensity occurred at 470 nm and decreased as RFA progressed. Transmission electron microscopy evidence of irreversible hepatocyte damage occurred at the interface of the coagulation zone and the hemorrhagic zone and correlated with a 87.5% +/- 9% decrease in fluorescence emission intensity. Tissue fluorescent changes from thermal injury were unaffected by tissue cooling. Fluorescence spectroscopy accurately detected hepatocellular thermal injury from RFA in real time and can detect irreversible cell damage during tissue thermal therapy.