+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Evaluation of TG-43 recommended 2D-anisotropy function for elongated brachytherapy sources



Evaluation of TG-43 recommended 2D-anisotropy function for elongated brachytherapy sources



Medical Physics 33(11): 4271-4279



The original and updated protocols recommended by Task Group 43 from the American Association of Physicists in Medicine (i.e., TG-43 and TG-43U1, respectively), have been introduced to unify brachytherapy source dosimetry around the world. Both of these protocols are based on experiences with sources less than 1.0 cm in length. TG-43U1 recommends that for 103Pd sources, 2D anisotropy function F(r, theta), should be tabulated at a minimum for radial distances of 0.5, 1.0, 2.0, 3.0, and 5.0 cm. Anisotropy functions defined in these protocols are only valid when the point of calculation does not fall on the active length of the source. However, for elongated brachytherapy sources (active length >1 cm), some of the calculation points with r < 1/2 active length and small theta may fall on the source itself and there is no clear recommendation to handle this situation. In addition, the linear interpolation technique recommended by TG-43U1 is found to be valid for seed types of sources as the difference between F(r, theta) for two consecutive radii is <10%. However, in the present investigations it has been found that values of F(r, 5 degrees) for a 5 cm long RadioCoil 103Pd source at radial distances of 2.5, 3.0, and 4.0 cm were 2.95, 1.74, and 1.19, respectively, with differences up to about a factor of 3. Therefore, the validity of the linear interpolation technique for an elongated brachytherapy source with such a large variation in F(r, theta) needs to be investigated. In this project, application of the TG-43U1 formalism for dose calculation around an elongated RadioCoil 103Pd brachytherapy source has been investigated. In addition, the linear interpolation techniques as described in TG-43U1 for seed type sources have been evaluated for a 5.0 cm long RadioCoil 103Pd brachytherapy source. Application of a polynomial fit to F(r, theta) has also been investigated as an alternate approach to the linear interpolation technique. The results of these investigations indicate that the TG-43U1 formalism can be extended for elongated brachytherapy sources, if the two-dimensional (2D) anisotropy function is tabulated at a minimum for radial distances of 0.2, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 cm, L/2, and L/2 +/- 0.2 cm. Moreover, with the addition of recommended radial distances for 2D anisotropy functions, the linear interpolation technique more closely replicates Monte Carlo simulated data than a polynomial fit.

Please choose payment method:






(PDF emailed within 0-6 h: $19.90)

Accession: 048993127

Download citation: RISBibTeXText

PMID: 17153405

DOI: 10.1118/1.2357024


Related references

Anisotropy function for 192Ir low-dose-rate brachytherapy sources: an EGS4 Monte Carlo study. Physics in Medicine and Biology 46(5): 1487-1499, 2001

TG-43U1 parameterization of elongated RadioCoil 103Pd brachytherapy sources. Journal of Applied Clinical Medical Physics 8(3): 2435, 2007

Feasibility of calibrating elongated brachytherapy sources using a well-type ionization chamber. Medical Physics 33(11): 4184-4189, 2006

Cylindrical coordinate based TG-43U1 parameters for dose calculation around elongated brachytherapy sources. Journal of Applied Clinical Medical Physics 9(2): 2760, 2008

Evaluation of Gafchromic EBT2 film for the measurement of anisotropy function for high-dose-rate (192)Ir brachytherapy source with respect to thermoluminescent dosimetry. Reports of Practical Oncology and RadioTherapy 16(1): 14-20, 2010

Accuracy assessment of the superposition principle for evaluating dose distributions of elongated and curved 103Pd and 192Ir brachytherapy sources. Medical Physics 38(6): 2957-2963, 2011

Anisotropy functions for 103Pd, 125I, and 192Ir interstitial brachytherapy sources. Medical Physics 20(5): 1465-1473, 1993

Age-appropriate compliance and completion of up to five doses of pertussis vaccine in US children. Human Vaccines and Immunotherapeutics 14(12): 2932-2939, 2018

Application of the Monte Carlo integration (MCI) method for calculation of the anisotropy of 192Ir brachytherapy sources. Physics in Medicine and Biology 43(6): 1783-1801, 1998

On the shape of the Task Group 43 anisotropy factor for linear brachytherapy sources at short distances. BrachyTherapy 13(4): 424-429, 2014

Anisotropy functions for low energy interstitial brachytherapy sources: An EGS4 Monte Carlo study. Physics in Medicine & Biology 46(1): 135-150, 2001

Radiochromic film measurement of anisotropy function for high-dose-rate Ir-192 brachytherapy source. Physics in Medicine and Biology 49(17): 4065-4072, 2004

Evaluation of a well-type ionization chamber for calibration of HDL and LDR brachytherapy sources. Medical Dosimetry 20(1): 31-34, 1995