Changes in In Vivo Optical Properties and Light Distributions in Normal Canine Prostate during Photodynamic Therapy

Abstract

The optical absorption and transport scattering coefficients of normal prostate tissue have been measured in vivo in dogs. The measurements were made at 630 nm before and during treatment by Photofin photodynamic therapy using interstitial optical fiber fluence-rate detectors. Corresponding measurements were made ex vivo, at 1 week after treatment, in the contralateral lobe. The optical properties were derived by applying a diffusion theory model to the fluence rates measured at two different source-detector fiber distances. While the in vivo pretreatment and in vivo contralateral post-treatment absorption and scattering values are self-consistent and in agreement with published data, significant changes were observed in the light fluence rates, and hence in the derived optical properties, during light irradiation. The possible causes of such changes are considered, and the implications for light dosimetry in photodynamic therapy are discussed.

Optimized interstitial PDT prostate treatment planning with the Cimmino feasibility algorithm

“…The mean values of μ eff and δ were 2.9 ± 0.8 cm −1 and 0.4 ± 0.1 cm, respectively. This penetration depth was substantially larger than that of 0.1-0.25 cm reported for 630 nm 6 but was smaller than the 0.5-3 cm observed in normal canine prostate at 732 nm. 7 The most probable explanation is that canine prostate has a different glandular/structure content than that of the human prostate.…”

“…2 Several preclinical studies have evaluated the feasibility of delivering PDT to the prostate via this interstitial approach. [3][4][5][6][7] The development of an interstitial light delivery technique required improved understanding of light dosimetry, critical in planning the configuration of multiple fibers within the organ or tumor. Based on the results of a preclinical study in canines, 8 we have initiated a protocol for motexafin lutetium (MLu)-mediated PDT of the prostate in patients at the University of Pennsylvania.…”

Studies of a vascular‐acting photosensitizer, Pd‐bacteriopheophorbide (Tookad), in normal canine prostate and spontaneous canine prostate cancer

“…This was not the case with Photofrin or other previously-tested photosensitizers [8,[13][14][15]18,19], and may be related to the mechanisms of vascularly-targeted damage. The apparent resistance of prostatic urethra to Tookad-PDT and the feasibility of transurethral PDT need to be further investigated.…”

“…PDT procedures can usually be done in an outpatient or day-case setting, it is convenient for the patient and has few side effects [6,7]. The feasibility of using PDT to treat prostate cancer in animal models has been investigated by our research team and several other groups [8,9]. Because of the difficulty in finding and recruiting spontaneous prostate cancer bearing animals, normal canine prostate has been used as the animal model, due to its resemblance in size and anatomical structure to human prostate.…”

Treatment planning using tailored and standard cylindrical light diffusers for photodynamic therapy of the prostate

“…Reports coincide to find sizable variations of the optical properties within the prostate and among different subjects (see for example (Muschter 2003), (Martin and Hahn 2004) and references therein). Furthermore, light delivery has been shown to affect the optical properties at some wavelengths (630 nm (Chen et al 1997) and 670 nm (Ballangrud et al 1997)), but not at longer ones (732 nm (Zhu et al 2003) and 763 nm (Chen et al 2002)). These data suggest that oxygen consumption plays a big role in this phenomenon since haemoglobin displays strong absorption in the 600 to 700 nm region.…”