Development of a computational simulation tool to design a protocol for treating prostate tumours using transurethral laser photothermal therapy

Objectives: The objective of this study was to design laser treatment protocols to induce sufficient thermal damage to a tumour embedded in a prostate model, while protecting the surrounding healthy tissue. Methods: A computational Monte Carlo simulation algorithm of light transport in a spherical prostatic tumour containing gold nanorods was developed to determine laser energy deposition. The laser energy absorption was then used to simulate temperature elevations in the tumour embedded in an elliptical human prostate model. The Arrhenius integral was coupled with the heat transfer model to identify heating protocols to induce 100% damage to the tumour, while resulting in less than 5% damage to the surrounding sensitive prostatic tissue. Results: Heating time to achieve 100% damage to the tumour was identified to be approximately 630 s when using a laser irradiance of 7 W/cm(2) incident on the prostatic urethral surface. Parametric studies were conducted to show how the local blood perfusion rate and urethral surface cooling affect the heating time to achieve the same thermal dosage. The heating time was shorter when cooling at the urethra was not applied and/or with heat-induced vasculature damage. The identified treatment protocols were acceptable since the calculated percentages of the damaged healthy tissue volume to the healthy prostatic volume were approximately 2%, less than the threshold of 5%. The approach and results from this study can be used to design individualised treatment protocols for patients suffering from prostatic cancer.