Post on 06-Aug-2015
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Effects of Temperature on Fluorescence in Human Tissue
D.B. Masters,1,* Alex Walsh,1 Ashley J. Welch,2 E. Duco Jansen,1 and Anita Mahadevan-Jansen1
1Department of Biomedical Engineering, Vanderbilt University, 5824 Stevenson
Center, Box 1631, Station B, Nashville, TN 37235 USA 2Biomedical Engineering Program, The University of Texas at Austin, 639
Engineering Science Building, Austin, TX, 78712-1084, USA
2
Disclosures
No disclosures.
Investigational research: not FDA approved.
No off label uses.
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Motivation
Applications• Fluorescence for therapy
guidance/ diagnosis─ Procedures with variable
temperature• RFA/microwave ablation• Electrocauterization• Laser ablation
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Background
• Fluorescence intensity and temperature – Usually inversely related– Depends on substance
• Tissue– Small temperature range– Very complex
• Optical property changes– Causes
• Coagulation• Dehydration• Denaturation
– Modulate fluorescence emission
• Other possible mechanisms− Loss of cell viability− Collisional quenching
Goal:Examine mechanism of fluorescence change due to temperature:1. Optical Properties2. Fluorophore
degradation
Materials & Methods: In vitro
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Materials• Human Tissue Samples:
– From liposuction and breast reduction surgeries– Skin
• Flash frozen samples
Passively warmed (to 23°C )
Actively heated (to 50°C or 70°C)
Allowed to cool (to 23°C)
Fluorescence and Temperature acquired every 2.5°C
Methods
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Materials and Methods
Data Processing
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Spectra (Fl., Rd.)
Spectral Processing
Inverse Monte Carlo1
µs’
µa
Max. Intensity
Rd
For every temperature, approximately every 2.5°C.
λ : 400-800 nm
Spectral AnalysisFl.
1Palmer, G.M. Appl. Opt., 2006. 45(5): p. 1062-1071.
• Reflectance data used in inverse Monte Carlo algorithm as input
• Output: µa, µs’
•Fluorescence max. intensity as a function of temperature
• Normalized so that peak intensity at 23°C was equal to 1.
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Results
• Consistent fluorescence decrease
•Optical property changes do not explain fluorescence decrease
Fl.
Pe
ak
He
igh
t (a
.u.)
0 20 40 60 800.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
s (cm
-1)
temperature C
Skin
0 20 40 60 8035
40
45
50
55
60
65
a (cm
-1)
0 20 40 60 801
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
Average (n=8)
St. Dev.
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Results: Reversibility
•All skin samples showed some reversibility
•Hysteresis expected
Fl.
Pe
ak
He
igh
t (a
.u.)
temperature C
Skin Reversibility
0 10 20 30 40 50 60 70 800.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
Average (n=8)
St. Dev.
Cooling: Max. Temp. 70C (n=4)
Cooling: Max. Temp. 50C (n=4)
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Conclusions: In Vitro
Fluorescence intensity decreases with increasing temperature in human tissue
Fluorophore degradation above a certain temperature
Optical properties do not explain fluorescence decrease at 20°C-50°C
Materials & Methods: In vivo
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Materials• Human lateral forearm• 7 volunteersMethods
Cooled Skin with Ice Pack
Skin Passively Warms to Body Temp.
Heated Skin with Heat Pack
Skin Passively Cools to Body Temp.
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Results: In Vivo
• Fluorescence decrease is reproduced in vivo– No damage– Completely
reversible
In Vivo Skin
Fl.
Pe
ak
He
igh
t (a
.u.)
temperature (C)
10 15 20 25 30 350.6
0.7
0.8
0.9
1
1.1
1.2
Average (n=7)
St. Dev.
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In Vivo: Conclusions
Fluorescence decrease can be reproduced in vivo
No damage or coagulation
Reversible
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Conclusions
In vitro•Fluorescence intensity decreases with increasing temperature in human tissue•Optical properties do not cause fluorescence decrease from 20°C to 50°C
In vivo•Fluorescence decrease can be reproduced in vivo
• No damage• Reversible
OverallIn human tissue, optical properties and tissue damage are not the only factors that cause a change in fluorescence due to temperature.
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Acknowledgements
•All the members of the Biomedical Optics Lab•Raiyan Zaman at the University of Texas at Austin•NIH R21 CA 133477•USAF Grant for Graduate Students and Post-Doctoral Fellows Currently Involved Full-
Time in Biomedical Laser Research travel grant