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Dose-volume histogram quality assurance for linac-based treatment planning systems.

Gossman MS, Bank MI - J Med Phys (2010)

Bottom Line: In this article we present the first quality assurance routine involving a direct comparison of planning system results with the results obtained from independent hand calculations.The average accuracy was within 0.6% for 6 MV and 0.4% for 18 MV for all depth-dose results.A 2% disagreement was observed with the treatment planning system DVH from defined volume comparison to the known structure dimensions.

View Article: PubMed Central - PubMed

Affiliation: Tri-State Regional Cancer Center, Medical Physics Section, 706, 23 Street, Ashland, Kentucky, USA.

ABSTRACT
Dose-volume histograms provide key information to radiation oncologists when they assess the adequacy of a patient treatment plan in radiation therapy. It is important therefore that all clinically relevant data be accurate. In this article we present the first quality assurance routine involving a direct comparison of planning system results with the results obtained from independent hand calculations. Given a known three-dimensional (3-D) structure such as a parallelepiped, a simple beam arrangement, and known physics beam data, a time-efficient and reproducible method for verifying the accuracy of volumetric statistics (DVH) from a radiation therapy treatment planning system (TPS) can be employed rapidly, satisfying the QA requirements for (TPS) commissioning, upgrades, and annual checks. Using this method, the maximum disagreement was only 1.7% for 6 MV and 1.3% for 18 MV photon energies. The average accuracy was within 0.6% for 6 MV and 0.4% for 18 MV for all depth-dose results. A 2% disagreement was observed with the treatment planning system DVH from defined volume comparison to the known structure dimensions.

No MeSH data available.


Axial view isodose distribution indicating the position of the rectangular volume within the water phantom. The isodose levels represent the percentage of dose, relative to 100 cGy at 10 cm phantom depth (5 cm structure depth), for an 18 MV beam having normal geometry and a field size of 30 × 30 cm2 at the SAD.
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Figure 0001: Axial view isodose distribution indicating the position of the rectangular volume within the water phantom. The isodose levels represent the percentage of dose, relative to 100 cGy at 10 cm phantom depth (5 cm structure depth), for an 18 MV beam having normal geometry and a field size of 30 × 30 cm2 at the SAD.

Mentions: The resulting computation of dose is qualitatively exhibited in Figure 1. It is again shown in the following illustration with a focus on the region comprising the contoured structural volume [Figure 2]. Isodose lines ranging from 75% to 125% (in 5% increments) are displayed in the Figures 1 and 2 as seen from the planning software for 18 MV photons. The depth of dose occurrence is analyzed for accuracy against the known dose data commissioned for the planning system. The accuracy of the analysis is strictly a function of knowing the depth-dose for that point. Further knowledge of the precise volume of the contour receiving such dose at each depth permits taking into account field edge horn effects created by the flattening filter of the accelerator. The calculation of the number of monitor units necessary to arrive at this prescription dose is shown in Equation 1.


Dose-volume histogram quality assurance for linac-based treatment planning systems.

Gossman MS, Bank MI - J Med Phys (2010)

Axial view isodose distribution indicating the position of the rectangular volume within the water phantom. The isodose levels represent the percentage of dose, relative to 100 cGy at 10 cm phantom depth (5 cm structure depth), for an 18 MV beam having normal geometry and a field size of 30 × 30 cm2 at the SAD.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2990113&req=5

Figure 0001: Axial view isodose distribution indicating the position of the rectangular volume within the water phantom. The isodose levels represent the percentage of dose, relative to 100 cGy at 10 cm phantom depth (5 cm structure depth), for an 18 MV beam having normal geometry and a field size of 30 × 30 cm2 at the SAD.
Mentions: The resulting computation of dose is qualitatively exhibited in Figure 1. It is again shown in the following illustration with a focus on the region comprising the contoured structural volume [Figure 2]. Isodose lines ranging from 75% to 125% (in 5% increments) are displayed in the Figures 1 and 2 as seen from the planning software for 18 MV photons. The depth of dose occurrence is analyzed for accuracy against the known dose data commissioned for the planning system. The accuracy of the analysis is strictly a function of knowing the depth-dose for that point. Further knowledge of the precise volume of the contour receiving such dose at each depth permits taking into account field edge horn effects created by the flattening filter of the accelerator. The calculation of the number of monitor units necessary to arrive at this prescription dose is shown in Equation 1.

Bottom Line: In this article we present the first quality assurance routine involving a direct comparison of planning system results with the results obtained from independent hand calculations.The average accuracy was within 0.6% for 6 MV and 0.4% for 18 MV for all depth-dose results.A 2% disagreement was observed with the treatment planning system DVH from defined volume comparison to the known structure dimensions.

View Article: PubMed Central - PubMed

Affiliation: Tri-State Regional Cancer Center, Medical Physics Section, 706, 23 Street, Ashland, Kentucky, USA.

ABSTRACT
Dose-volume histograms provide key information to radiation oncologists when they assess the adequacy of a patient treatment plan in radiation therapy. It is important therefore that all clinically relevant data be accurate. In this article we present the first quality assurance routine involving a direct comparison of planning system results with the results obtained from independent hand calculations. Given a known three-dimensional (3-D) structure such as a parallelepiped, a simple beam arrangement, and known physics beam data, a time-efficient and reproducible method for verifying the accuracy of volumetric statistics (DVH) from a radiation therapy treatment planning system (TPS) can be employed rapidly, satisfying the QA requirements for (TPS) commissioning, upgrades, and annual checks. Using this method, the maximum disagreement was only 1.7% for 6 MV and 1.3% for 18 MV photon energies. The average accuracy was within 0.6% for 6 MV and 0.4% for 18 MV for all depth-dose results. A 2% disagreement was observed with the treatment planning system DVH from defined volume comparison to the known structure dimensions.

No MeSH data available.