BLADDER PDT WITH INTRAVESICAL CLEAR AND LIGHT-SCATTERING MEDIA - EFFECT OF AN ECCENTRIC ISOTROPIC LIGHT-SOURCE ON THE LIGHT-DISTRIBUTION

Background and Objective: Whole bladder wall photodynamic therapy (PDT ) is sometimes performed with a light scattering medium in the bladder , as it is assumed that this will promote a more uniform illumination of the bladder wall. The influence of eccentric placement of an isotro pic light emitting diffuser on the homogeneity of the light distributi on at the bladder wall is assessed. Study Design/Materials and Methods : Whole bladder wall irradiations were performed at approximate to 630 nm, and fluence rates were measured with and without controlled amoun ts of Intralipid(R) in an ex vivo pig bladder and in vitro in a bladde r phantom. Experimental values were compared to Monte Carlo simulation s using in vitro bladder optical properties. Results: An eccentric dif fuser in a clear intravesical medium produces a better uniform illumin ation than in a light scattering intravesical medium. Also, intravesic al light absorption, e.g., by urine, would lead to a substantial loss of the energy delivered in case of light scattering cavity contents. C onclusion: The use of a clear intravesical medium guarantees the highe st and most uniform fluence rate at the bladder wall during optical ir radiation with an isotropic light source in clinical PDT of nonspheric al bladders, whereas an intravesical light scattering medium reduces b oth the magnitude and the uniformity of the fluence rate. (C) 1997 Wil ey-Liss, Inc.