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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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Dose volume histogram (DVH) of head-and-neck patient plans. The thick dashed line shows the DVH for a standard IMRT plan generally used at our institution. The thick line corresponds to the FFF 7 MV plan version c, displayed in Figure 6. Thin lines correspond to the other plan versions a,b,c (6 MV and 7 MV) – these plans are not analyzed in detail here and are therefore not distinguished in the figure.
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Figure 5: Dose volume histogram (DVH) of head-and-neck patient plans. The thick dashed line shows the DVH for a standard IMRT plan generally used at our institution. The thick line corresponds to the FFF 7 MV plan version c, displayed in Figure 6. Thin lines correspond to the other plan versions a,b,c (6 MV and 7 MV) – these plans are not analyzed in detail here and are therefore not distinguished in the figure.

Mentions: In the head-and-neck case, plan versions a and c had acceptable qualities. Version b, with 50 segments distributed over 36 beam directions, gave worse quality than both version a (50 segments with 18 beam directions, giving more opportunity of modulation for each beam) and version c (36 beams with 72 segments), even though the DVH is similar for all six plans (both 6 MV and FFF 7 MV, Figure 5). Version c had best coverage and least extension of the 80% isodose outside the PTV, which is why we chose to present this plan (FFF 7 MV, which has comparable quality to the 6 MV version c plan, compared with a “standard” IMRT plan using 7 beams and 50 segments (Figure 6, Table 2)).


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)

Dose volume histogram (DVH) of head-and-neck patient plans. The thick dashed line shows the DVH for a standard IMRT plan generally used at our institution. The thick line corresponds to the FFF 7 MV plan version c, displayed in Figure 6. Thin lines correspond to the other plan versions a,b,c (6 MV and 7 MV) – these plans are not analyzed in detail here and are therefore not distinguished in the figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Dose volume histogram (DVH) of head-and-neck patient plans. The thick dashed line shows the DVH for a standard IMRT plan generally used at our institution. The thick line corresponds to the FFF 7 MV plan version c, displayed in Figure 6. Thin lines correspond to the other plan versions a,b,c (6 MV and 7 MV) – these plans are not analyzed in detail here and are therefore not distinguished in the figure.
Mentions: In the head-and-neck case, plan versions a and c had acceptable qualities. Version b, with 50 segments distributed over 36 beam directions, gave worse quality than both version a (50 segments with 18 beam directions, giving more opportunity of modulation for each beam) and version c (36 beams with 72 segments), even though the DVH is similar for all six plans (both 6 MV and FFF 7 MV, Figure 5). Version c had best coverage and least extension of the 80% isodose outside the PTV, which is why we chose to present this plan (FFF 7 MV, which has comparable quality to the 6 MV version c plan, compared with a “standard” IMRT plan using 7 beams and 50 segments (Figure 6, Table 2)).

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