Robert Splinter,1
Serguei Y. Semenov,2
Glenn A. Nanney,3
Laszlo Littmann,1
Jan R. Tuntelder,1
Robert H. Svenson,1
Chi Hui Chuang,1
and George P. Tatsis1
1Carolinas Medical Center, Charlotte, North Carolina 28203
2Biophysical Laboratory, Kurchatov Institute of Atomic Energy, 142092 Troitsk, Moscow region, Russia
3Transform Systems Design Ltd., Charlotte, North Carolina 28205
Robert Splinter, Serguei Y. Semenov, Glenn A. Nanney, Laszlo Littmann, Jan R. Tuntelder, Robert H. Svenson, Chi Hui Chuang, and George P. Tatsis, "Myocardial temperature distribution under cw Nd:YAG laser irradiation in in vitro and in vivo situations: theory and experiment," Appl. Opt. 34, 391-399 (1995)
Tissue samples ranging from 2 to 16 mm in thickness were irradiated at 1064 nm with energies ranging from 40 to 2400 J. Coagulation lesions of in vitro and in vivo experiments were subjected to temperature profiling and submitted for histology. Irreversible damage was calculated with the damage integral formalism, following the bioheat equation solved with Monte Carlo computer light-distribution simulations. Numerical temperature rise and coagulation depth compared well with the in vitro results. The in vivo data required a change in the optical properties based on integrating sphere measurements for high irradiance to make the experimental and numerical data converge. The computer model has successfully solved several light–tissue interaction situations in which scattering dominates over absorption.
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Optical Parameters of Tissues Used in the Illustrations for Monte Carlo Simulations for the Determination of the Heat-Source Function
Sample Thickness (mm) 2
μa (mm−1) 0.04
μs (mm−1) 17.5
g (−) 0.975
Spot Size (mm) 2.5
Experimental Conditions In vitro
Irradiance (W/cm2) <2000
6
0.04
17.5
0.975
2.5
In vitro
<2000
13
0.04
17.5
0.975
0.4
In vivo
<2000
13
0.04
17.5
0.975
0.9
In vivo
<2000
13
0.04
14.0
0.999
0.4
In vivo
≥2000
Table 2
Lasing Parameters, Endocardial (Tprox) and Subendocardial (Tdist) Temperatures, Epicardial Maximum Temperatures (Tepi), Lesion Dimensions, and Epicardial Temperature Rise to an Arbitrary 57°C (t57) during Endocardial Lasing with 400-μm Fiber in Contacta
Lasing Parameters, Endocardial (Tprox) and Subendocardial (Tdist) Temperatures, Epicardial Maximum Temperatures (Tepi), Lesion Dimensions, and Epicardial Temperature Rise to an Arbitrary 57°C (t57) during Endocardial Lasing with 1-mm Spot Sizea
Myocardial In Vitro Tissue-Temperature Rise Recorded with Thermography as a Result of Laser Irradiation at 20 W with a 2.5-mm Spot Size in a Saline Environment on the Backside of a Thin Tissue Sample for Short Irradiation Times and In Vivo Tissue-Temperature Recordings for Irradiation with a 400-μm Bare Fiber in Close Contact Determined from the Maximum Temperature Recorded with Thermography (Te) Minus Baseline Temperature (Tb), (ΔTexp = Te − Tb)a
In addition to the theoretical temperature rise (ΔTexp), experimental depth of coagulation were measured with histological examination (Depth) and depth of irreversible damage was calculated with the bioheat equation and the damage integral (D).
Mean ± standard deviation.
Numerical values for the low- and high-power-density light-distribution models, respectively.
Tables (4)
Table 1
Optical Parameters of Tissues Used in the Illustrations for Monte Carlo Simulations for the Determination of the Heat-Source Function
Sample Thickness (mm) 2
μa (mm−1) 0.04
μs (mm−1) 17.5
g (−) 0.975
Spot Size (mm) 2.5
Experimental Conditions In vitro
Irradiance (W/cm2) <2000
6
0.04
17.5
0.975
2.5
In vitro
<2000
13
0.04
17.5
0.975
0.4
In vivo
<2000
13
0.04
17.5
0.975
0.9
In vivo
<2000
13
0.04
14.0
0.999
0.4
In vivo
≥2000
Table 2
Lasing Parameters, Endocardial (Tprox) and Subendocardial (Tdist) Temperatures, Epicardial Maximum Temperatures (Tepi), Lesion Dimensions, and Epicardial Temperature Rise to an Arbitrary 57°C (t57) during Endocardial Lasing with 400-μm Fiber in Contacta
Lasing Parameters, Endocardial (Tprox) and Subendocardial (Tdist) Temperatures, Epicardial Maximum Temperatures (Tepi), Lesion Dimensions, and Epicardial Temperature Rise to an Arbitrary 57°C (t57) during Endocardial Lasing with 1-mm Spot Sizea
Myocardial In Vitro Tissue-Temperature Rise Recorded with Thermography as a Result of Laser Irradiation at 20 W with a 2.5-mm Spot Size in a Saline Environment on the Backside of a Thin Tissue Sample for Short Irradiation Times and In Vivo Tissue-Temperature Recordings for Irradiation with a 400-μm Bare Fiber in Close Contact Determined from the Maximum Temperature Recorded with Thermography (Te) Minus Baseline Temperature (Tb), (ΔTexp = Te − Tb)a
In addition to the theoretical temperature rise (ΔTexp), experimental depth of coagulation were measured with histological examination (Depth) and depth of irreversible damage was calculated with the bioheat equation and the damage integral (D).
Mean ± standard deviation.
Numerical values for the low- and high-power-density light-distribution models, respectively.