ADVANCEMENTS IN INTERSTITIAL BRACHYTHERAPY

Abstract

In recent years, interstitial brachytherapy implantation has become the treatment of choice for early stage prostate cancer patients. The popularity of this modality is due to the fact that five-and ten-year disease control rates using brachytherapy are equal to those of surgery, whereas, the toxicity and side-effects are perceived to be lower. Recently, a true linear source model RadioCoilTM103Pd has been introduced to overcome the shortcomings of traditional ―seed‖ type interstitial prostate brachytherapy implants, such as migration and clumping of the seeds. However, the existing prostate treatment planning systems and TG-43U1 have not been updated to perform dose calculation and parameterization respectively, for implant with linear sources greater than 1.0cm in length. Due to these limitations, the innovative design of RadioCoilTM103Pd could not be fully implemented for clinical applications. In this research, treatment planning aspect of elongated RadioCoilTM103Pd sources is investigated. In addition, accuracy of existing TG-43U1 recommended dosimetric parameters in polar coordinate systems, a modification in radial increment to improve the accuracy and modification of TG-43U1 parameterization in to cylindrical coordinate systems is also investigated. This work resulted in a calculational method and modification in TG-43U1 parameters for accurate dose calculation around elongated sources. Experimental, Thermolumenance Dosimetry TLD and Monte Carlo simulation techniques were employed in this investigation. This work was successfully completed and led to a new Task Group, TG-143 from American Association of Medical Phyicists in Medicine, AAPM, to provide guidelines for clinical application of elongated sources and extend our findings for other elongated sources.