Implementation of enhanced dynamic wedge in the focus rtp system

Miften, Moyed; Wiesmeyer, Mark; Beavis, A W; Takahashi, Kaz; Broad, Steve

doi:10.1016/s0958-3947(00)00033-9

Cited by 16 publications

(17 citation statements)

References 12 publications

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“…Prado et al 96 used an empirical formula to determine the dose to arbitrary points within the field. Miften et al 97 determined a scatter dose correction determined from the differences between measured and calculated WF for a 60…”

Section: B1ii Physical Wedges a Number Of Investigatorsmentioning

confidence: 99%

Monitor unit calculations for external photon and electron beams: Report of the AAPM Therapy Physics Committee Task Group No. 71

et al. 2014

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A protocol is presented for the calculation of monitor units (MU) for photon and electron beams, delivered with and without beam modifiers, for constant source-surface distance (SSD) and source-axis distance (SAD) setups. This protocol was written by Task Group 71 of the Therapy Physics Committee of the American Association of Physicists in Medicine (AAPM) and has been formally approved by the AAPM for clinical use. The protocol defines the nomenclature for the dosimetric quantities used in these calculations, along with instructions for their determination and measurement. Calculations are made using the dose per MU under normalization conditions, D 0 , that is determined for each user's photon and electron beams. For electron beams, the depth of normalization is taken to be the depth of maximum dose along the central axis for the same field incident on a water phantom at the same SSD, where D 0 = 1 cGy/MU. For photon beams, this task group recommends that a normalization depth of 10 cm be selected, where an energy-dependent D 0 ≤ 1 cGy/MU is required. This recommendation differs from the more common approach of a normalization depth of d m , with D 0 = 1 cGy/MU, although both systems are acceptable within the current protocol. For photon beams, the formalism includes the use of blocked fields, physical or dynamic wedges, and (static) multileaf collimation. No formalism is provided for intensity modulated radiation therapy calculations, although some general considerations and a review of current calculation techniques are included. For electron beams, the formalism provides for calculations at the standard and extended SSDs using either an effective SSD or an air-gap correction factor. Example tables and problems are included to illustrate the basic concepts within the presented formalism.

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Section: B1ii Physical Wedges a Number Of Investigatorsmentioning

confidence: 99%

Monitor unit calculations for external photon and electron beams: Report of the AAPM Therapy Physics Committee Task Group No. 71

et al. 2014

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“…The advantage of the EDW versus the dynamic wedge ͑the previous version of EDW͒ is that only a single ''golden'' segmented treatment table ͑GSTT͒ is used, which simplifies the implementation of the EDW. The implementation of the EDW to a treatment planning system has been discussed by several authors, [1][2][3][4][5][6] whose main focus was on symmetric fields in the verification of output factor calculations by treatment planning systems. Gibbons 7 and Papatheodorou et al 8 discussed and modeled the wedge factor at the center of the field for asymmetric fields, and the agreement of calculated with measured values was within 2%.…”

Section: Introductionmentioning

confidence: 99%

Generalized monitor unit calculation for the Varian enhanced dynamic wedge field

et al. 2003

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The generalized monitor unit (MU) calculation equation for the Varian enhanced dynamic wedge (EDW) is derived. The assumption of this MU calculation method is that the wedge factor of the EDW at the center of the field is a function of field size, the position of the center of the field in the wedge direction, and the final position of the moving jaw. The wedge factors at the center of the field in both symmetric and asymmetric fields are examined. The difference between calculated and measured wedge factors is within 1.0%. The method developed here is easy to implement. The only datum required in addition to the standard set of conventional physical wedge implementation data is the off-axis output factor for the open field in the reference condition. The off-center point calculation is also examined. For the off-center point calculation, the dose profile in the wedge direction for the largest EDW field is used to obtain the relative off-center ratio in any smaller wedge field. The accuracy of the off-center point calculation decreases when the point of calculation is too close to the field edge.

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“…In Table 1, 1VW and 2VW indicate that the wedge orientation is formed by making y 1 or y 2 dynamic jaws. However, similar to the Varian EDW, Moued ( 11 ) and Miften ( 12 ) point out there may be a difference of up to 6% in the toe region on larger fields and larger wedge angles. This may be caused by overestimation by the VM model of the dose in the toe region for these field and wedge combinations.…”

Section: Resultsmentioning

confidence: 60%

The accuracy of dynamic wedge dose computation in the ADAC Pinnacle RTP system

Shao

Chengji

et al. 2004

J Applied Clin Med Phys

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The nonphysical wedge is a modality that uses computer‐controlled jaw motion to generate wedge‐shaped dose distributions. There are Varian enhanced dynamic wedges (EDWs) and Siemens virtual wedges (VWs). We recently commissioned dynamic wedges on both Varian and Siemens LINACs. The beam data, acquired with a Wellhöfer chamber array and a Sun Nuclear profiler, are used for modeling in the ADAC Pinnacle system. As recommended by ADAC, only a limited number of beam data is measured and used for beam modeling. Therefore, the dose distributions of dynamic wedges generated by Pinnacle must be examined. Following the commissioning of the dynamic wedges, we used Pinnacle to generate a number of dose distributions with different energies, wedge angles, field sizes, and depths. The computed data from Pinnacle are then compared with the measured data.The deviations of the output factor in all square and rectangular fields are mostly within 2.0% for both EDW and VW. For asymmetric fields, the deviations are within 3%. However, exceptions of differences more than 3% have been found in a larger field and large wedge combinations. The precision of the beam profiles generated by Pinnacle is also evaluated. As a result of this investigation, we present a scope of quality assurance tests that are necessary to ensure acceptable consistency between the delivered dose and the associated treatment plan when dynamic wedges are applied.PACS numbers: 8753 Dq, 87.53.Xd

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Implementation of enhanced dynamic wedge in the focus rtp system

Cited by 16 publications

References 12 publications

Monitor unit calculations for external photon and electron beams: Report of the AAPM Therapy Physics Committee Task Group No. 71

Monitor unit calculations for external photon and electron beams: Report of the AAPM Therapy Physics Committee Task Group No. 71

Generalized monitor unit calculation for the Varian enhanced dynamic wedge field

The accuracy of dynamic wedge dose computation in the ADAC Pinnacle RTP system

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