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

Bahreyni Toossi MT, Ghorbani M, Mowlavi AA, Meigooni AS - Radiol Oncol (2012)

Bottom Line: These parameters of this source are compared with the available data for Ralstron (60)Co and microSelectron(192)Ir sources.The results of these investigations show that the dosimetric parameters of GZP6 source are comparable to those for the Ralstron source.The calculated dosimetric quantities of this new source can be introduced as input data to the GZP6 treatment planning system (TPS) and to validate the performance of the TPS.

View Article: PubMed Central - PubMed

Affiliation: Medical Physics Research Center, Medical Physics Department, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.

ABSTRACT

Background: Dosimetric characteristics of a high dose rate (HDR) GZP6 Co-60 brachytherapy source have been evaluated following American Association of Physicists in MedicineTask Group 43U1 (AAPM TG-43U1) recommendations for their clinical applications.

Materials and methods: MCNP-4C and MCNPX Monte Carlo codes were utilized to calculate dose rate constant, two dimensional (2D) dose distribution, radial dose function and 2D anisotropy function of the source. These parameters of this source are compared with the available data for Ralstron (60)Co and microSelectron(192)Ir sources. Besides, a superimposition method was developed to extend the obtained results for the GZP6 source No. 3 to other GZP6 sources.

Results: The simulated value for dose rate constant for GZP6 source was 1.104±0.03 cGyh-1U-1. The graphical and tabulated radial dose function and 2D anisotropy function of this source are presented here. The results of these investigations show that the dosimetric parameters of GZP6 source are comparable to those for the Ralstron source. While dose rate constant for the two (60)Co sources are similar to that for the microSelectron(192)Ir source, there are differences between radial dose function and anisotropy functions. Radial dose function of the (192)Ir source is less steep than both (60)Co source models. In addition, the (60)Co sources are showing more isotropic dose distribution than the (192)Ir source.

Conclusions: The superimposition method is applicable to produce dose distributions for other source arrangements from the dose distribution of a single source. The calculated dosimetric quantities of this new source can be introduced as input data to the GZP6 treatment planning system (TPS) and to validate the performance of the TPS.

No MeSH data available.


Schematic diagram illustrating six GZP6 source braids, containing active and nonactive pellets. Each source is allocated to one separate channel. The sources 1–5 are stationary while the source No. 6 is stepper.
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f1-rado-46-02-170: Schematic diagram illustrating six GZP6 source braids, containing active and nonactive pellets. Each source is allocated to one separate channel. The sources 1–5 are stationary while the source No. 6 is stepper.

Mentions: The newly designed GZP6 HDR 60Co brachytherapy unit has been recently employed for the clinical practice in Iran. Unlike the HDR 192Ir systems, which contain one source, the GZP6 unit includes six different sources (Figure 1). Each source is designated to a separate channel in the HDR unit. Five of these six sources are stationary, and the 6th source (i.e. source number 6) has stepping (dwelling) capability that could be used for treatment of patients with longer active length. As shown in Figure 1, each source is composed of a source-braid or packing, consist of 1, 2, 3 or 4 radioactive source pellets as well as a number of non active steel pellets. In order to make these source geometries reproducible, at the same time flexible as it moves within the transfer tube and applicator, the active and non-active pellets are fitted within a steel spring cover. Dimensions and components of the active and non-active pellets of these sources are provided in the schematic diagram of source number 3 (Figure 2). In their first publication on this system, Mesbahi et al. measured the air kerma strengthsof source numbers 1, 2 and 5.11 In a separate investigation, Mesbahi has also calculated radial dose function for these three sources.12 Naseri et al. have examined the accuracy of the dose distributions calculated by the GZP6 treatment planning system by Monte Carlo simulation of these sources.13 Monte Carlo simulation is widely used in radiophysics14, however, to our knowledge the GZP6 unit has not been studied before, based on a comprehensive determination of TG-43U1 dosimetric parameters.15 Since the GZP6 unit has six sources with different fixed configurations, each source has been individually evaluated for their clinical applications.


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

Bahreyni Toossi MT, Ghorbani M, Mowlavi AA, Meigooni AS - Radiol Oncol (2012)

Schematic diagram illustrating six GZP6 source braids, containing active and nonactive pellets. Each source is allocated to one separate channel. The sources 1–5 are stationary while the source No. 6 is stepper.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3472933&req=5

f1-rado-46-02-170: Schematic diagram illustrating six GZP6 source braids, containing active and nonactive pellets. Each source is allocated to one separate channel. The sources 1–5 are stationary while the source No. 6 is stepper.
Mentions: The newly designed GZP6 HDR 60Co brachytherapy unit has been recently employed for the clinical practice in Iran. Unlike the HDR 192Ir systems, which contain one source, the GZP6 unit includes six different sources (Figure 1). Each source is designated to a separate channel in the HDR unit. Five of these six sources are stationary, and the 6th source (i.e. source number 6) has stepping (dwelling) capability that could be used for treatment of patients with longer active length. As shown in Figure 1, each source is composed of a source-braid or packing, consist of 1, 2, 3 or 4 radioactive source pellets as well as a number of non active steel pellets. In order to make these source geometries reproducible, at the same time flexible as it moves within the transfer tube and applicator, the active and non-active pellets are fitted within a steel spring cover. Dimensions and components of the active and non-active pellets of these sources are provided in the schematic diagram of source number 3 (Figure 2). In their first publication on this system, Mesbahi et al. measured the air kerma strengthsof source numbers 1, 2 and 5.11 In a separate investigation, Mesbahi has also calculated radial dose function for these three sources.12 Naseri et al. have examined the accuracy of the dose distributions calculated by the GZP6 treatment planning system by Monte Carlo simulation of these sources.13 Monte Carlo simulation is widely used in radiophysics14, however, to our knowledge the GZP6 unit has not been studied before, based on a comprehensive determination of TG-43U1 dosimetric parameters.15 Since the GZP6 unit has six sources with different fixed configurations, each source has been individually evaluated for their clinical applications.

Bottom Line: These parameters of this source are compared with the available data for Ralstron (60)Co and microSelectron(192)Ir sources.The results of these investigations show that the dosimetric parameters of GZP6 source are comparable to those for the Ralstron source.The calculated dosimetric quantities of this new source can be introduced as input data to the GZP6 treatment planning system (TPS) and to validate the performance of the TPS.

View Article: PubMed Central - PubMed

Affiliation: Medical Physics Research Center, Medical Physics Department, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.

ABSTRACT

Background: Dosimetric characteristics of a high dose rate (HDR) GZP6 Co-60 brachytherapy source have been evaluated following American Association of Physicists in MedicineTask Group 43U1 (AAPM TG-43U1) recommendations for their clinical applications.

Materials and methods: MCNP-4C and MCNPX Monte Carlo codes were utilized to calculate dose rate constant, two dimensional (2D) dose distribution, radial dose function and 2D anisotropy function of the source. These parameters of this source are compared with the available data for Ralstron (60)Co and microSelectron(192)Ir sources. Besides, a superimposition method was developed to extend the obtained results for the GZP6 source No. 3 to other GZP6 sources.

Results: The simulated value for dose rate constant for GZP6 source was 1.104±0.03 cGyh-1U-1. The graphical and tabulated radial dose function and 2D anisotropy function of this source are presented here. The results of these investigations show that the dosimetric parameters of GZP6 source are comparable to those for the Ralstron source. While dose rate constant for the two (60)Co sources are similar to that for the microSelectron(192)Ir source, there are differences between radial dose function and anisotropy functions. Radial dose function of the (192)Ir source is less steep than both (60)Co source models. In addition, the (60)Co sources are showing more isotropic dose distribution than the (192)Ir source.

Conclusions: The superimposition method is applicable to produce dose distributions for other source arrangements from the dose distribution of a single source. The calculated dosimetric quantities of this new source can be introduced as input data to the GZP6 treatment planning system (TPS) and to validate the performance of the TPS.

No MeSH data available.