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Measurement of the coagulation dynamics of bovine liver using the modified microscopic Beer–Lambert law
Author(s) -
Terenji Albert,
Willmann Stefan,
Osterholz Jens,
Hering Peter,
Schwarzmaier HansJoachim
Publication year - 2005
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/lsm.20178
Subject(s) - coagulation , chemistry , absorption (acoustics) , dynamic light scattering , scattering , arrhenius equation , liver tissue , analytical chemistry (journal) , spectrometer , materials science , optics , activation energy , chromatography , nanoparticle , physics , nanotechnology , medicine , psychology , organic chemistry , psychiatry
Background and Objectives During heating, the optical properties of biological tissues change with the coagulation state. In this study, we propose a technique, which uses these changes to monitor the coagulation process during laser‐induced interstitial thermotherapy (LITT). Study Design/Materials and Methods Untreated and coagulated (water bath, temperatures between 35°C and 90°C for 20 minutes.) samples of bovine liver tissue were examined using a Nd:YAG (λ = 1064 nm) frequency‐domain reflectance spectrometer. We determined the time integrated intensities ( I DC ) and the phase shifts (Φ) of the photon density waves after migration through the tissue. From these measured quantities, the time of flight ( TOF ) of the photons and the absorption coefficients of the samples were derived using the modified microscopic Beer–Lambert law. Results The absorption coefficients of the liver samples decreased significantly with the temperature in the range between 50°C and 70°C. At the same time, the TOF of the investigated photos was found increased indicating an increased scattering. The coagulation dynamics could be well described using the Arrhenius formalism with the activation energy of 106 kJ/mol and the frequency factor of 1.59×10 13 /second. Conclusions Frequency‐domain reflectance spectroscopy in combination with the modified microscopic Beer–Lambert (MBL) is suitable to measure heat induced changes in the absorption and scattering properties of bovine liver in vitro. The technique may be used to monitor the coagulation dynamics during local thermo‐coagulation in vivo. © 2005 Wiley‐Liss, Inc.