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Fluorescence measurement of 805 nm laser‐induced release of 5,6‐CF from DSPC liposomes for real‐time monitoring of temperature: An in vivo study in rat liver using indocyanine green potentiation
Author(s) -
Mordon Serge,
Desmettre Thomas,
Devoisselle Jean Marie,
Soulie Sylvie
Publication year - 1996
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/(sici)1096-9101(1996)18:3<265::aid-lsm8>3.0.co;2-q
Subject(s) - indocyanine green , in vivo , fluorescence , liposome , laser , biomedical engineering , biophysics , chemistry , materials science , pathology , optics , medicine , biology , nanotechnology , physics , microbiology and biotechnology
Background and Objective This in vivo study examines the validity of using fluorescence measurements of laser‐induced release of temperature‐sensitive, liposome‐encapsulated dye for real‐time monitoring of temperature and for prediction of tissue thermal damage. Study Design/Materials and Methods An in vivo study is performed in rat liver after i.v. injection of liposomes loaded with a fluorescent dye and i.v. injection of indocyanine green (ICG) for diode laser potentiation. Temperature‐sensitive liposomes (DSPC: Di‐Stearoyl‐Phosphatidyl‐Choline) are loaded with 5,6‐carboxyfluorescein (5,6‐CF). These liposomes (1.5 ml solution) and ICG (1.5 ml solution‐5mg/kg) are injected in adult male wistar rats. Two hours later, the liver is exposed and irradiated with a 0.8 W diode laser using pulses lasting from 1–6s (fluence ranging from 16–98 J/cm 2 ). Simultaneously, the fluorescence emission is analysed with an ultrahigh sensitivity intensified camera. Results The fluorescence intensity I F increases linearly from 18 J/cm 2 up to 75 J/cm 2 . These fluences correspond to surface temperatures between 42°C and 65°C. The measurements appear to be highly reproducible. In this temperature range, the accuracy is +/−3°C. The maximum intensity is observed immediately after the laser is switched off. A decrease of the fluorescence intensity (27% in 20 minutes) is observed due to the 5,6‐CF clearance. However, the ratio I F /I BCK (I BCK : background fluorescence intensity) remains almost stable over this period of time and the determination of the temperature is still possible with good accuracy even 20 minutes after laser irradiation. Conclusion Real‐time temperature monitoring by using fluorescence measurement of laser‐induced release of liposome‐encapsulated dye is clearly demonstrated. This procedure could conceivably prove useful for controlling the thermal coagulation of biological tissues. © 1996 Wiley‐Liss, Inc.