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 isotropic light emitting diffuser on the homogeneity of the light distribution at the bladder wall is assessed.

STUDY DESIGN/MATERIALS AND METHODS: Whole bladder wall irradiations were performed at approximately 630 nm, and fluence rates were measured with and without controlled amounts of Intralipid in an ex vivo pig bladder and in vitro in a bladder phantom. Experimental values were compared to Monte Carlo simulations using in vitro bladder optical properties.

RESULTS

An eccentric diffuser in a clear intravesical medium produces a better uniform illumination than in a light scattering intravesical medium. Also, intravesical light absorption, e.g., by urine, would lead to a substantial loss of the energy delivered in case of light scattering cavity contents.

CONCLUSION

The use of a clear intravesical medium guarantees the highest and most uniform fluence rate at the bladder wall during optical irradiation with an isotropic light source in clinical PDT of nonspherical bladders, whereas an intravesical light scattering medium reduces both the magnitude and the uniformity of the fluence rate.