Experimental derivation of the fluence non-uniformity correction for air kerma near brachytherapy linear sources
- Laboratorio de Ciencias Radiologicas, LCR-DBB-UERJ, Rua Sao Francisco Xavier 524, CEP 20 500-013, Rio de Janeiro (Brazil)
In brachytherapy, one of the elements to take into account for measurements free in air is the non-uniformity of the photon fluence due to the beam divergence that causes a steep dose gradient near the source. The correction factors for this phenomenon have been usually evaluated by two available theories by Kondo and Randolph [Radiat. Res. 13, 37-60 (1960)] and Bielajew [Phys. Med. Biol. 35, 517-538 (1990)], both conceived for point sources. This work presents the experimental validation of the Monte Carlo calculations made by Rodriguez and deAlmeida [Phys. Med. Biol. 49, 1705-1709 (2004)] for the non-uniformity correction specifically for a Cs-137 linear source measured using a Farmer type ionization chamber. The experimental values agree very well with the Monte Carlo calculations and differ from the results predicted by both theoretical models widely used. This result confirms that for linear sources there are some important differences at short distances from the source and emphasizes that those theories should not be used for linear sources. The data provided in this study confirm the limitations of the mentioned theories when linear sources are used. Considering the difficulties and uncertainties associated with the experimental measurements, it is recommended to use the Monte Carlo data to assess the non-uniformity factors for linear sources in situations that require this knowledge.
- OSTI ID:
- 21120860
- Journal Information:
- Medical Physics, Vol. 35, Issue 7; Other Information: DOI: 10.1118/1.2940160; (c) 2008 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-2405
- Country of Publication:
- United States
- Language:
- English
Similar Records
Simulation evaluation of NIST air-kerma rate calibration standard for electronic brachytherapy: Simulation of NIST air-kerma rate eBT calibration standard
Brachytherapy structural shielding calculations using Monte Carlo generated, monoenergetic data