Resection is not a viable treatment option for the majority of liver cancer patients. Alternatives to resection include thermotherapies such as radio-frequency ablation; however, these therapies lack adequate intraoperative feedback regarding the degree and margins of tissue thermal damage. In this proof of principle study, we test the ability of fluorescence and diffuse reflectance spectroscopy to assess local thermal damage in vivo. Spectra were acquired in vivo from healthy canine liver tissue undergoing radio-frequency ablation using a portable fiber-optic-based spectroscopic system. The major observed spectral alterations on thermal coagulation were a red shift in the fluorescence emission peak at 480 nm, a decrease in the overall fluorescence intensity, and an increase in the diffuse reflectance from 450 to 750 nm. Spectral changes were quantified and correlated to tissue histology. We found a good correlation between the proposed spectral correlates of thermal damage and histology. The results of this study suggest that fluorescence and diffuse reflectance spectroscopy show strong potential as tools to monitor liver tissue thermal damage intraoperatively.
Thermotherapies such as radio-frequency ablation achieve necrosis of liver tumors through thermal coagulation and are frequently employed when surgical resection is impossible. Currently, thermotherapy procedures suffer from the lack of an adequate feedback control system, making it difficult to know precisely when to terminate therapy. In vitro and in vivo studies were performed on canine liver tissue to determine the feasibility of using fluorescence and diffuse reflectance spectroscopy to provide an objective endpoint for these procedures. The fluorescence and diffuse reflectance spectra of liver tissue exhibited consistent changes over the coagulation process. In vitro results showed a shift in the primary fluorescence peak from 490 nm in the native state to 510 nm in the fully coagulated state; in addition, a three- to four-fold increase in the absolute intensity of the diffuse reflectance spectra was observed upon complete coagulation. Similar spectral alterations were obtained in vivo. Based on our results, fluorescence and diffuse reflectance spectroscopy provide a direct way to assess the biochemical and structural changes associated with tissue thermal damage; hence, they can be developed into a feedback system for thermotherapies.