SU-E-T-207: In Vivo Verification of Local Hyperthermia in the Liver

Purpose: We performed invasive thermometry to verify the elevation of local temperature in the liver during extracorporeal hyperthermia. Methods: Three 40 kg weighted-pigs were used for the experiments after approval by the Institutional Animal Care and Use Committee. Under general anesthesia, two glass fibre-optic sensors were placed in the liver and one was placed in the peritoneal cavity in front of the liver with ultrasonography guidance. 4th sensor was at the skin surface to assess superficial cooling. Six sessions of hyperthermia were delivered by using the Celsius TCS electro-hyperthermia system. The energy delivered was elevated from 240 kJ at the first session to 500 kJ at the 6th session for 60 minute treatment session. Inter-session cooling was at least 30 minutes. The temperatures of the sensors were recorded every 5 minutes during hyperthermia and every 10 minutes during inter-session break. Thermal-infrared images were also taken. The elevated temperatures during the consecutive sessions were analyzed. Results: As the animals were anesthetized, the baseline temperature at the start of the each session decreased 1.3 to 2.8 degrees Celsius (median, 2.1 degrees). The mean elevated temperature measured by the intrahepatic sensors was 2.4 degrees (95% confidence interval [CI], 1.7–3.1) and 2.7 degrees Celsius (95% CI, 2.0–3.3) during the fifth and sixth session, respectively. The corresponding values for the intraperitoneal sensors were 2.1 (95% CI, 0.7–3.5) and 2.9 degrees Celsius (1.3–4.4), respectively. While temperatures at the liver and peritoneal cavity were elevated, skin temperature was not elevated but decreased according to application of cooling system. Conclusion: We observed mean temperature increase of 2.7 and 2.9 degrees Celsius at the liver and peritoneal cavity during hyperthermia. Although this experiment has potential limitations from long-time general anesthesia, in vivo real-time thermometry using living body is worth pursuing in terms of direct measurement of internal temperature during extracorporeal hyperthermia.