Premium
LIGHT DOSIMETRY FOR PHOTODYNAMIC THERAPY BY WHOLE BLADDER WALL IRRADIATION
Author(s) -
Star Willem M.,
Marijnissen Hans P. A.,
Jansen Harald,
Keijzer Marleen,
VAN Gemert Martin J. C.
Publication year - 1987
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1987.tb04822.x
Subject(s) - fluence , optics , dosimetry , irradiation , materials science , photodynamic therapy , spheres , wavelength , isotropy , light scattering , beam (structure) , percentage depth dose curve , scattering , nuclear medicine , chemistry , laser , physics , medicine , ionization chamber , ion , astronomy , ionization , organic chemistry , nuclear physics
In Photodynamic Therapy (PDT) there is a need for accurate quantitative light dosimetry. This has become particularly apparent in the treatment of superficial bladder cancer, either by focal or by whole bladder wall irradiation. We have studied this problem using a spherical model of the bladder, consisting of two concentric thin‐walled plastic spheres, 8 and 10 cm in diameter. The inner sphere was filled with water or with a light‐scattering medium. The space between the spheres was filled with an optically tissue equivalent liquid. An isotropic light source was placed at the center of the spheres. Light energy fluence rates (light “dose rates”) during PDT of the bladder simulated in this manner, were measured using a specially developed miniature light detector and were also calculated using a mathematical model. These data were confirmed by measurements in vivo (dog bladder). In the case of focal irradiation at a wavelength of 630 nm, the ratio (R) between the true light fluence rate at the bladder surface and the fluence rate due to the primary light beam is somewhat larger than 1, depending on the diameter of the primary beam. The maximum ratio is 2, for a beam diameter of several centimeters. In the case of whole bladder wall PDT, R is larger than 5. This is due to the strong scattering of (red) light by tissue and indicates that the intensity of the primary beam, which is usually reported, is not a good measure of the true fluence rate for whole bladder wall PDT. When the light source is moved away from the center of the spheres, the rate of change of the fluence rate at the bladder wall is more than a factor of 2 larger when the bladder cavity is filled with a light‐scattering suspension, as compared with water. The use of a light‐scattering medium may therefore not be advantageous to achieve a uniform light distribution across the bladder wall.