Anisotropy of radiance in tissue phantoms and Dunning R3327 rat tumors: radiance measurements with flat cleaved fiber probes.
OBJECTIVE
The goal of this study is to determine if flat cleaved fiber probes are appropriate for interstitial measurements of radiance in tissue. Flat cleaved probes have the advantage of high responsivity, and they are easy to insert into tissue. Owing to the non-isotropic response of flat cleaved probes, a calibration function is required, taking the anisotropy in the radiance in tissue into account.


METHODS
The method used to determine this function consists of radiance measurements in tissue, performed with a flat cleaved fiber probe mounted on a stereotactic stage for insertion into the tissue from different directions. Interstitial irradiation at 630 nm was delivered by a spherical source.


RESULTS
We found that the degree of anisotropy in the radiance decreases with increasing distance from the interstitially implanted source in two different tissue phantoms and in the Dunning R3327-AT and R3327-H rat tumor models.


CONCLUSIONS
A position-dependent calibration function is required for interstitially implanted flat cleaved fiber probes. An anisotropy function is presented, which modifies the measurements of radiance with a flat cleaved probe, to account for the change in anisotropy in the radiance. The anisotropy functions for the two tumor models differ substantially.
Ballangrud
A M
AM
University of Alberta, Department of Electrical Engineering, Edmonton, Canada.
Wilson
P J
PJ
Brown
K
K
Miller
G G
GG
Moore
R B
RB
McPhee
M S
MS
Tulip
J
J
D000818:Animals; D008297:Male; D008433:Mathematics; D008954:Models, Biological; D008962:Models, Theoretical; D009374:Neoplasms, Experimental; D011827:Radiation; D051381:Rats