Cylindrical coordinate‐based TG‐43U1 parameters for dose calculation around elongated brachytherapy sources

Abstract

In 2001, the use of cylindrical coordinates was demonstrated to be more suitable than was the use of polar coordinates for accurate computer calculations during treatment planning for normalI192r intravascular brachytherapy sources. In the present work, we investigated the applicability of cylindrical coordinate–based TG‐43U1 parameters for dosimetric evaluation and dose calculations for RadioCoil 103Pd sources (RadioMed Corporation, Tyngsboro, MA) 1.0‐cm to 6.0‐cm long. For brevity, only the results for sources 1.0‐cm, 3.0‐cm, and 5.0‐cm long are presented here. Dosimetric characteristics of RadioCoil 103Pd sources were calculated in liquid water using the Monte Carlo simulation technique. To demonstrate the suitability of this methodology, the Monte Carlo–simulated dose profiles for a RadioCoil 103Pd source 5.0‐cm long at radial distances of 0.5 cm, 0.9 cm, and 1.25 cm were compared with calculated data using TG‐43U1 parameters in the polar and cylindrical coordinate systems. In addition, we also used a source 1.0‐cm long parameterized using cylindrical coordinates to investigate the application of a linear segmented source (LSS) model originally introduced by our group. The results indicate that, for dose calculation around elongated brachytherapy sources, cylindrical coordinate–based TG‐43U1 parameters more accurately represent the dose distribution around an elongated source than the polar coordinate–based parameters. In addition, the LSS model, in conjunction with the cylindrical coordinate–based parameters for a source 1.0‐cm long, can be used to replicate the dose distribution around any integral source length. This process eliminates the need to collect and enter data for multiple source lengths into treatment planning systems.PACS number: 87.66.Jj

103Pd strings: Monte Carlo assessment of a new approach to brachytherapy source design

“…To evaluate the validity of approximating longer length CivaStrings as combinations of shorter length CivaStrings, dose was calculated in water with a rectilinear mesh in a cylindrical coordinate system. 29 The mesh geometry for each source was toroidal and covered a range of 12.70 cm in the Y and Z directions from the source origin with each voxel having a (0.05 cm) 2 square cross section as rotated about the source long axis. Upon calculation of all six CivaString dose distributions, quantitative comparisons of some possible combinations were made to determine if summation of MC-based simulations for a brachytherapy source component would be representative of the total dose distribution.…”

“…This may be accomplished using either the polar coordinate system common in most modern TPS with TG-43 parameters, 5 or with a cylindrical coordinate system as examined with a rectilinear mesh in the current study and considered by Meigooni and colleagues. 29,51 Accurate dosimetric characterization of the CivaString and CivaThin sources may require data with higher resolution than for sources having a simpler design and a uniform radionuclide distribution as a function of source length, such as for 192 Ir wires and the 103 Pd RadioCoil sources.…”

An approach to using conventional brachytherapy software for clinical treatment planning of complex, Monte Carlo‐based brachytherapy dose distributionsa)

“…Using conventional brachytherapy TPS, the Tufts technique allows one to replicate dose distributions obtained by Monte Carlo methods for complex multi-source applicators containing high-Z shielding for bounded phantom configurations with a "virtual source" using a modified TG-43 formalism ͑using either the standard polar or the cylindrical coordinates systems͒. [10][11][12] Clinical implementation of the Tufts technique for three brachytherapy treatment modalities is described where conventional TPS calculations ͑based on single-source input data͒ are inadequate. 11,12…”

Dosimetric characterizations of GZP6 60Co high dose rate brachytherapy sources: application of superimposition method

“…As denoted by Awan et al 17, considering the source active length L, the radial distance r and the angles θ and ß as showed in the Figure 2, equation [5] can be resulted from the above equation: $\text{G}(r,\theta )=\frac{{\text{tan}}^{-1}[(r\text{cos}\theta +L/2)/r\text{sin}\theta ]-{\text{tan}}^{-1}[(r\text{cos}\theta -L/2)/r\text{sin}\theta ]}{Lr\text{sin}\theta }$…”