Variation of fluorescence in tissue with temperature.
OBJECTIVE
Previous studies demonstrated a decrease in fluorescence intensity as tissue temperature increased. In vitro samples were increased from room temperature and in vivo canine liver from body temperature. This study investigated variations in fluorescence intensity with temperatures starting at 14°C and compared in vivo and in vitro results for consistency.


METHODS
A fiber optic-based noninvasive system was used to characterize the temperature effect on tissue fluorescence in hamster dorsal skin in vivo, and in sclera and cornea of enucleated pig eyes in vitro. As tissue was allowed to progress through the temperature range of 14-42°C, the spectra of auto-fluorescence with respect to temperature was sampled every 1-2 minutes. A pulsed nitrogen laser was used to excite fluorescence through a fiber optic probe with a source-detector aperture separation of 370 µm.


RESULTS
Fluorescence intensity decreased as temperature increased from 14 to 42°C in a phantom containing Rhodamine B dye. Results from both in vivo and in vitro tissue followed the same trend of decreasing intensity as tissue temperature increased from 14°C. Spectral intensity lineshape changed around 450 nm due to absorption from tissue.


CONCLUSIONS
Cooling a tissue increased fluorescence intensity of skin in vivo, in all experiments. In vitro results were consistent with in vivo measurements.
Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712-0238, USA. raiyan_zaman@yahoo.com
Raiyan T
RT
Zaman
Narasimhan
N
Rajaram
Alex
A
Walsh
Jeffrey
J
Oliver
Henry G
HG
Rylander
James W
JW
Tunnell
Ashley J
AJ
Welch
Anita
A
Mahadevan-Jansen
D000818:Animals; D001831:Body Temperature; D006224:Cricetinae; D005123:Eye; D066298:In Vitro Techniques; D012881:Skin Temperature; D013050:Spectrometry, Fluorescence; D013552:Swine