Application of radioactive isotopes is the treatment of choice around the globe for many cancer sites. In this technique, the accuracy of the radiation delivery is highly dependent on the accuracy of radiation dosimetry around individual brachytherapy sources. Moreover, in order to have compatible clinical results, an identical method of source dosimetry must be employed across the world. This problem has been recently addressed by Task Group 43 (TG43) from the American Association of Medical Physics (AAPM) with a protocol for dosimetric characterizatio n of brachytherapy sources. This new protocol has been further updated using published data from international sources, by a new Task Group from the AAPM. This has resulted in an
updated protocol known as TG43U1 that has been published in March 2004 issue of Medical Physics. The goal of this presentation is to review the original TG43 protocol and associated algorithms for brachytherapy source dosimetry. In addition, the shortcomings of the original protocol that has been resolved in the updated recommendation will be highlighted. I am sure that this is not the end of the line and more work is needed to complete this task. I invite the scientists to join this task and complete the project, with the hope of much better clinical results for cancer patients. Iran . J. Radiat. Res., 2004 2 (3): 97-105