Abstract
Treatment planning for ultrasound-guided transperitoneal 1-125 permanent prostatic implants is a time consuming task, because this treatment uses many seeds (e. g.50-80) and there are many solutions (seed positions) for optimizing the dose distribution. In conventional treatment planning for brachytherapy the locations of sources are usually input into a computer manually with reference to two X-ray films. We use so many sources in this treatment that we can hardly obtain accurate location of each source. That is, the identification of each seed with two X-ray films is very difficult. Even though we can use X-ray CT images for deciding on the source position, there are artifacts due to the high attenuation material. This paper proposes a method for obtaining accurate locations of radioactive sources from some projection data (e. g. RPO 60,40,20, LPO 60,40,20 and 0 deg. ) with a reconstruction method. In our method for obtaining actual source positions we use an iterative image reconstruction technique. The results obtained by experiments with a simple prostate phantom and the RANDO phantom showed that the locations of dummy seeds were accurately decided with a reconstructed image by six or seven projection data.
