Critical temperature and heating time for coagulation damage: Implications for interstitial laser coagulation (ilc) of tumors

Abstract

Background Interstitial laser coagulation (ILC) is a method of local tissue destruction for solid tumors such as irresectable hepatic metastases from colorectal cancer. With the availability of new magnetic resonance (MR) techniques, which allow real time tissue temperature mapping, it is essential to know the critical temperature and exposure times leading to cell death. Materials and Methods/Study Design Samples (8 mm3) of solid rat tumor (CC-531, syngenic to the WAG/Rij rat strain), were warmed in tubes for four different temperatures (40, 50, 60 or 80°C) and four different exposure times (3, 6, 12, or 24 minutes). Combinations were replicated in five-fold. Cell viability was assessed with three methods: Trypan blue exclusion test in collagenase/dispase dissociated samples, NADH activity in snap frozen samples and outgrowth for 2 weeks under the renal capsule of WAG/Rij rats. Results Results of the three methods revealed that viability was not affected with heating at 40 and 50°C except for 24 minutes at 50°C. At higher temperatures cell death occurred at all exposure times. Conclusion The temperature range resulting in sufficient tissue coagulation for cell death is between 50°C and 60°C for a short duration (<3 minutes). These data can be used to achieve complete tumor destruction and minimal surrounding tissue damage during real-time MR-controlled ILC. Lasers Surg. Med. 25:257–262, 1999. © 1999 Wiley-Liss, Inc.