Clinical Brachytherapy With Neutron Emitting Cf-252 Sources And Adherence To Aapm Tg-43 Dosimetry Protocol

Using Monte Carlo methods, neutron dosimetry for Cf-252 Applicator Tube (AT) type medical sources available from Oak Ridge National Laboratory (ORNL) has for the first time been determined in terms of TG-43 formalism. This approach, as compared to previous "along-away" formalisms, demonstrates the relative angular independence of dose rate data, when the geometry factor has been removed. As the ORNL-made Cf-252 AT type sources are considerably physically larger than most clinical sources used today, the radial dose function increases for radii less than 3.0 mm due to breakdown of the line source model. A comparison of the Cf-252 neutron radial dose function with those for other medical sources revealed similarities with that from Cs-137. Differences with respect to previous Cf-252 AT source neutron dosimetry data generally increased at increasing distances. This was attributed to differences in the various Cf-252 AT source models and phantom compositions. The current status of Cf-252 medical source fabrication and calibration procedures at ORNL is presented. (C) 1999 American Association of Physicists in Medicine. [S0094-2405(99)00501-5].