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 ap proach, as compared to previous "along-away" formalisms, demonstrates the r elative angular independence of dose rate data, when the geometry factor ha s been removed. As the ORNL-made Cf-252 AT type sources are considerably ph ysically larger than most clinical sources used today, the radial dose func tion increases for radii less than 3.0 mm due to breakdown of the line sour ce model. A comparison of the Cf-252 neutron radial dose function with thos e for other medical sources revealed similarities with that from Cs-137. Di fferences with respect to previous Cf-252 AT source neutron dosimetry data generally increased at increasing distances. This was attributed to differe nces in the various Cf-252 AT source models and phantom compositions. The c urrent status of Cf-252 medical source fabrication and calibration procedur es at ORNL is presented. (C) 1999 American Association of Physicists in Med icine. [S0094-2405(99)00501-5].