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A novel implementation of mARC treatment for non-dedicated planning systems using converted IMRT plans.

Dzierma Y, Nuesken F, Licht N, Ruebe C - Radiat Oncol (2013)

Bottom Line: For all plans, the treatment time was noticeably reduced by conversion to mARC.We present the feasibility test for converting IMRT step-and-shoot plans from the RTP-output of any treatment planning system (Philips Pinnacle and Prowess Panther, in our case) into mARC plans.The feasibility and dosimetric equivalence is demonstrated for the examples of a prostate and a head-and-neck patient.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Background: The modulated arc (mARC) technique has recently been introduced by Siemens as an analogue to VMAT treatment. However, up to now only one certified treatment planning system supports mARC planning. We therefore present a conversion algorithm capable of converting IMRT plans created by any treatment planning system into mARC plans, with the hope of expanding the availability of mARC to a larger range of clinical users and researchers. As additional advantages, our implementation offers improved functionality for planning hybrid arcs and provides an equivalent step-and-shoot plan for each mARC plan, which can be used as a back-up concept in institutions where only one linac is equipped with mARC.

Methods: We present a feasibility study to outline a practical implementation of mARC plan conversion using Philips Pinnacle and Prowess Panther. We present examples for three different kinds of prostate and head-and-neck plans, for 6 MV and flattening-filter-free (FFF) 7 MV photon energies, which are dosimetrically verified.

Results: It is generally more difficult to create good quality IMRT plans in Pinnacle using a large number of beams and few segments. We present different ways of optimization as examples. By careful choosing the beam and segment arrangement and inversion objectives, we achieve plan qualities similar to our usual IMRT plans. The conversion of the plans to mARC format yields functional plans, which can be irradiated without incidences. Absolute dosimetric verification of both the step-and-shoot and mARC plans by point dose measurements showed deviations below 5% local dose, mARC plans deviated from step-and-shoot plans by no more than 1%. The agreement between GafChromic film measurements of planar dose before and after mARC conversion is excellent. The comparison of the 3D dose distribution measured by PTW Octavius 729 2D-Array with the step-and-shoot plans and with the TPS is well above the pass criteria of 90% of the points falling within 5% local dose and 3 mm distance to agreement. For all plans, the treatment time was noticeably reduced by conversion to mARC.

Conclusions: We present the feasibility test for converting IMRT step-and-shoot plans from the RTP-output of any treatment planning system (Philips Pinnacle and Prowess Panther, in our case) into mARC plans. The feasibility and dosimetric equivalence is demonstrated for the examples of a prostate and a head-and-neck patient.

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Dosimetric verification of mARC vs. treatment planning system. Gamma distribution of Octavius 729 2D-Array measurement of the converted mARC plan (version c), compared with the dose distribution exported from the Pinnacle TPS. One transversal and one sagittal slice are shown. Pass criteria are 5% deviation in local dose and 3 mm distance to agreement, which are satisfied by over 95% of measurement points in all slices.
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Figure 8: Dosimetric verification of mARC vs. treatment planning system. Gamma distribution of Octavius 729 2D-Array measurement of the converted mARC plan (version c), compared with the dose distribution exported from the Pinnacle TPS. One transversal and one sagittal slice are shown. Pass criteria are 5% deviation in local dose and 3 mm distance to agreement, which are satisfied by over 95% of measurement points in all slices.

Mentions: In principle, validation of the treatment planning system is already proven by the fact that dosimetric verification for IMRT plans was checked in the commissioning phase [9] and in routine quality assurance, and since the deviation of the mARC plans from the step-and-shoot plans is negligible. However, we demonstrate these measurements for completeness. Besides, in the clinical routine it is more practical to perform routine mARC verification measurements directly (mARC plan vs. planning system) rather than the two-step approach of verifying the IMRT dose distribution and then comparing this with the converted plan. Verification of the mARC dose distribution before treatment is carried out using the PTW Octavius phantom with 729 2D-Array, which measured the irradiated mARC three-dimensional dose distribution with the treatment planning system. For all plans, over 95% of the points pass the criteria of 5% deviation in local dose and 3 mm distance-to-agreement (example shown in Figure 8), which provides an independent verification of the dose distribution of the mARC plan.


A novel implementation of mARC treatment for non-dedicated planning systems using converted IMRT plans.

Dzierma Y, Nuesken F, Licht N, Ruebe C - Radiat Oncol (2013)

Dosimetric verification of mARC vs. treatment planning system. Gamma distribution of Octavius 729 2D-Array measurement of the converted mARC plan (version c), compared with the dose distribution exported from the Pinnacle TPS. One transversal and one sagittal slice are shown. Pass criteria are 5% deviation in local dose and 3 mm distance to agreement, which are satisfied by over 95% of measurement points in all slices.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750816&req=5

Figure 8: Dosimetric verification of mARC vs. treatment planning system. Gamma distribution of Octavius 729 2D-Array measurement of the converted mARC plan (version c), compared with the dose distribution exported from the Pinnacle TPS. One transversal and one sagittal slice are shown. Pass criteria are 5% deviation in local dose and 3 mm distance to agreement, which are satisfied by over 95% of measurement points in all slices.
Mentions: In principle, validation of the treatment planning system is already proven by the fact that dosimetric verification for IMRT plans was checked in the commissioning phase [9] and in routine quality assurance, and since the deviation of the mARC plans from the step-and-shoot plans is negligible. However, we demonstrate these measurements for completeness. Besides, in the clinical routine it is more practical to perform routine mARC verification measurements directly (mARC plan vs. planning system) rather than the two-step approach of verifying the IMRT dose distribution and then comparing this with the converted plan. Verification of the mARC dose distribution before treatment is carried out using the PTW Octavius phantom with 729 2D-Array, which measured the irradiated mARC three-dimensional dose distribution with the treatment planning system. For all plans, over 95% of the points pass the criteria of 5% deviation in local dose and 3 mm distance-to-agreement (example shown in Figure 8), which provides an independent verification of the dose distribution of the mARC plan.

Bottom Line: For all plans, the treatment time was noticeably reduced by conversion to mARC.We present the feasibility test for converting IMRT step-and-shoot plans from the RTP-output of any treatment planning system (Philips Pinnacle and Prowess Panther, in our case) into mARC plans.The feasibility and dosimetric equivalence is demonstrated for the examples of a prostate and a head-and-neck patient.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Background: The modulated arc (mARC) technique has recently been introduced by Siemens as an analogue to VMAT treatment. However, up to now only one certified treatment planning system supports mARC planning. We therefore present a conversion algorithm capable of converting IMRT plans created by any treatment planning system into mARC plans, with the hope of expanding the availability of mARC to a larger range of clinical users and researchers. As additional advantages, our implementation offers improved functionality for planning hybrid arcs and provides an equivalent step-and-shoot plan for each mARC plan, which can be used as a back-up concept in institutions where only one linac is equipped with mARC.

Methods: We present a feasibility study to outline a practical implementation of mARC plan conversion using Philips Pinnacle and Prowess Panther. We present examples for three different kinds of prostate and head-and-neck plans, for 6 MV and flattening-filter-free (FFF) 7 MV photon energies, which are dosimetrically verified.

Results: It is generally more difficult to create good quality IMRT plans in Pinnacle using a large number of beams and few segments. We present different ways of optimization as examples. By careful choosing the beam and segment arrangement and inversion objectives, we achieve plan qualities similar to our usual IMRT plans. The conversion of the plans to mARC format yields functional plans, which can be irradiated without incidences. Absolute dosimetric verification of both the step-and-shoot and mARC plans by point dose measurements showed deviations below 5% local dose, mARC plans deviated from step-and-shoot plans by no more than 1%. The agreement between GafChromic film measurements of planar dose before and after mARC conversion is excellent. The comparison of the 3D dose distribution measured by PTW Octavius 729 2D-Array with the step-and-shoot plans and with the TPS is well above the pass criteria of 90% of the points falling within 5% local dose and 3 mm distance to agreement. For all plans, the treatment time was noticeably reduced by conversion to mARC.

Conclusions: We present the feasibility test for converting IMRT step-and-shoot plans from the RTP-output of any treatment planning system (Philips Pinnacle and Prowess Panther, in our case) into mARC plans. The feasibility and dosimetric equivalence is demonstrated for the examples of a prostate and a head-and-neck patient.

Show MeSH
Related in: MedlinePlus