Tomosynthesis-based localization of radioactive seeds in prostate brachytherapy

~Received 14 April 2003; revised 25 July 2003; accepted for publication 17 September 2003;published 19 November 2003!Accurately assessing the quality of prostate brachytherapy intraoperatively would be valuable forimproved clinical outcome by ensuring the delivery of a prescribed tumoricidal radiation dose to theentire prostate gland. One necessary step towards this goal is the robust and rapid localization ofimplanted seeds. Several methods have been developed to locate seeds from x-ray projectionimages, but they fail to detect completely-overlapping seeds, thus necessitating manual interven-tion. To overcome this limitation, we have developed a new method where ~1! a three-dimensionalvolume is reconstructed from x-ray projection images using a brachytherapy-specific tomosynthesisreconstruction algorithm with built-in blur compensation and ~2! the seeds are located in thisreconstructed volume. In contrast to other projection-based methods, our method can detect com-pletely overlapping seeds. Our simulation results indicate that we can locate all implanted seeds inthe prostate using a tomosynthesis angle of 30° and seven projection images. The mean localizationerror is 1.27 mm for a case with 100 seeds. We have also tested our method using a prostatephantom with 61 implanted seeds and succeeded in locating all seeds automatically. We believe thisnew method can be useful for the intraoperative quality assessment of prostate brachytherapy in thefuture. © 2003 American Association of Physicists in Medicine. @DOI: 10.1118/1.1624755#Key words: prostate brachytherapy, seed localization, intraoperative dosimetry, tomosynthesisI. INTRODUCTIONProstate cancer is the second leading cause of cancer death inmen in the United States, but it can be fully treated if de-tected early.