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Accuracy Evaluation of Oncentra™ TPS in HDR Brachytherapy of Nasopharynx Cancer Using EGSnrc Monte Carlo Code.

Hadad K, Zohrevand M, Faghihi R, Sedighi Pashaki A - J Biomed Phys Eng (2015)

Bottom Line: Dose distribution was plotted by DOSXYZnrc and compared with TPS one.The results from calculations were compared with data from Oncentra™ treatment planning system and it was observed that TPS calculation predicts lower dose in areas near the source, and higher dose in areas far from the source relative to MC code.This protocol may results in errors such as neglecting tissue heterogeneity, scattered radiation as well as applicator attenuation.

View Article: PubMed Central - PubMed

Affiliation: Nuclear Engineering Department, Faculty of Mechanical Engineering, Shiraz University, Shiraz, Iran;

ABSTRACT

Background: HDR brachytherapy is one of the commonest methods of nasopharyngeal cancer treatment. In this method, depending on how advanced one tumor is, 2 to 6 Gy dose as intracavitary brachytherapy is prescribed. Due to high dose rate and tumor location, accuracy evaluation of treatment planning system (TPS) is particularly important. Common methods used in TPS dosimetry are based on computations in a homogeneous phantom. Heterogeneous phantoms, especially patient-specific voxel phantoms can increase dosimetric accuracy.

Materials and methods: In this study, using CT images taken from a patient and ctcreate-which is a part of the DOSXYZnrc computational code, patient-specific phantom was made. Dose distribution was plotted by DOSXYZnrc and compared with TPS one. Also, by extracting the voxels absorbed dose in treatment volume, dose-volume histograms (DVH) was plotted and compared with Oncentra™ TPS DVHs.

Results: The results from calculations were compared with data from Oncentra™ treatment planning system and it was observed that TPS calculation predicts lower dose in areas near the source, and higher dose in areas far from the source relative to MC code. Absorbed dose values in the voxels also showed that TPS reports D90 value is 40% higher than the Monte Carlo method.

Conclusion: Today, most treatment planning systems use TG-43 protocol. This protocol may results in errors such as neglecting tissue heterogeneity, scattered radiation as well as applicator attenuation. Due to these errors, AAPM emphasized departing from TG-43 protocol and approaching new brachytherapy protocol TG-186 in which patient-specific phantom is used and heterogeneities are affected in dosimetry.

No MeSH data available.


Related in: MedlinePlus

Comparison of Radial Dose Function for Ir-192 Version mHDR-v2 and Source 6 DOSXYZnrc
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Figure 1: Comparison of Radial Dose Function for Ir-192 Version mHDR-v2 and Source 6 DOSXYZnrc

Mentions: Data of radial dose function for Ir-192 model mHDR-v2 was taken from Papagianis et al.[7], and was compared with source 6 DOSXYZnrc radial dose function. Results indicate a good agreement of radial dose functions for these two sources in low distance as given in Figure 1.


Accuracy Evaluation of Oncentra™ TPS in HDR Brachytherapy of Nasopharynx Cancer Using EGSnrc Monte Carlo Code.

Hadad K, Zohrevand M, Faghihi R, Sedighi Pashaki A - J Biomed Phys Eng (2015)

Comparison of Radial Dose Function for Ir-192 Version mHDR-v2 and Source 6 DOSXYZnrc
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4417616&req=5

Figure 1: Comparison of Radial Dose Function for Ir-192 Version mHDR-v2 and Source 6 DOSXYZnrc
Mentions: Data of radial dose function for Ir-192 model mHDR-v2 was taken from Papagianis et al.[7], and was compared with source 6 DOSXYZnrc radial dose function. Results indicate a good agreement of radial dose functions for these two sources in low distance as given in Figure 1.

Bottom Line: Dose distribution was plotted by DOSXYZnrc and compared with TPS one.The results from calculations were compared with data from Oncentra™ treatment planning system and it was observed that TPS calculation predicts lower dose in areas near the source, and higher dose in areas far from the source relative to MC code.This protocol may results in errors such as neglecting tissue heterogeneity, scattered radiation as well as applicator attenuation.

View Article: PubMed Central - PubMed

Affiliation: Nuclear Engineering Department, Faculty of Mechanical Engineering, Shiraz University, Shiraz, Iran;

ABSTRACT

Background: HDR brachytherapy is one of the commonest methods of nasopharyngeal cancer treatment. In this method, depending on how advanced one tumor is, 2 to 6 Gy dose as intracavitary brachytherapy is prescribed. Due to high dose rate and tumor location, accuracy evaluation of treatment planning system (TPS) is particularly important. Common methods used in TPS dosimetry are based on computations in a homogeneous phantom. Heterogeneous phantoms, especially patient-specific voxel phantoms can increase dosimetric accuracy.

Materials and methods: In this study, using CT images taken from a patient and ctcreate-which is a part of the DOSXYZnrc computational code, patient-specific phantom was made. Dose distribution was plotted by DOSXYZnrc and compared with TPS one. Also, by extracting the voxels absorbed dose in treatment volume, dose-volume histograms (DVH) was plotted and compared with Oncentra™ TPS DVHs.

Results: The results from calculations were compared with data from Oncentra™ treatment planning system and it was observed that TPS calculation predicts lower dose in areas near the source, and higher dose in areas far from the source relative to MC code. Absorbed dose values in the voxels also showed that TPS reports D90 value is 40% higher than the Monte Carlo method.

Conclusion: Today, most treatment planning systems use TG-43 protocol. This protocol may results in errors such as neglecting tissue heterogeneity, scattered radiation as well as applicator attenuation. Due to these errors, AAPM emphasized departing from TG-43 protocol and approaching new brachytherapy protocol TG-186 in which patient-specific phantom is used and heterogeneities are affected in dosimetry.

No MeSH data available.


Related in: MedlinePlus