Joint AAPM/IROC Houston Registry of Brachytherapy Sources Meeting
the AAPM Dosimetric Prerequisites

 

The AAPM dosimetric prerequisites for brachytherapy sources may be summarized as follows The vendor provides air-kerma strength calibrations that are directly or indirectly traceable to the air-kerma strength standards (S_K,N99 for low energy sources) for photon emitting brachytherapy sources maintained by NIST, or in the case of HDR ¹⁹²Ir, the standard developed by the University of Wisconsin and maintained by the ADCLs.

•    A full set of TG-43 dosimetric parameters is available, supporting both calculation of the 2-D dose-rate distribution and, for low-energy seed models, the 1-D isotropic point source approximation. This set of dosimetric parameters must be based upon at least one experimental study and at least one Monte Carlo study of the source model’s dosimetric parameters. These studies must be performed by investigators having independence from the manufacturer, and have been accepted for publication in a peer-reviewed journal.

•    The vendor has assured that the calibration from NIST has been transferred to the ADCLs.

•    The vendor has implemented a program that is compliant with the 2004 CLA Report for periodically comparing its air-kerma strength calibrations with the NIST primary standard and the secondary standards maintained by the ADCLs.

The complete text of the 2004 CLA report is available here.

The AAPM dosimetric prerequisites for high-energy sources may be summarized as follows:

•    The single-source dose distribution used for clinical treatment planning should be based upon two dose-rate determinations, one of which is a theoretical calculation method such as the Monte Carlo method, and the other an experimental measurement. Note that a single dosimetric study is acceptable for certain ¹³⁷Cs, ¹⁹²Ir, and ⁶⁰Co sources under specific circumstances (see the complete text.)

•    A full set of TG-43 dosimetric parameters is available, supporting calculation of the 2-D dose-rate distribution. In addition, a set of “along and away” tables must be provided.

•    The vendor provides air-kerma strength calibrations that are directly or indirectly traceable to the air-kerma strength standards for photon emitting brachytherapy sources maintained by NIST.

•    The vendor has implemented a program of periodically comparing its air-kerma strength calibrations with the NIST primary standard or the secondary standards maintained by the ADCLs that is compliant with the CLA Report. Note, however, that while the CLA Report specifically addresses low-energy sources, the AAPM has confirmed that manufacturers are expected to comply with its requirements for high-energy sources also. The CLA Report was dedicated to low-energy sources. Until a similar report is available for high-energy sources, vendors must apply these guidelines with appropriate variations. For example, it may be necessary to send a source or a measurement system to NIST or an ADCL.

•    In addition, the AAPM requires biennial comparisons for high-energy sources through Measurement Quality Assurance (MQA) tests.

•    In the case of experimental sources for which no ADCL interpolative or NIST primary standard exists, the end user institution is responsible for calibrating the sources with an ionization chamber of appropriate dimensions that has calibrations directly traceable to an appropriate NIST air-kerma standard.