The `equivalent wedge' implementation of the Varian Enhanced Dynamic Wedge (EDW) into a treatment planning system

Papatheodorou, S.; Zefkili, S.; Rosenwald, Jean-Claude

doi:10.1088/0031-9155/44/2/016

Cited by 15 publications

(20 citation statements)

References 19 publications

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“…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: 83%

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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Section: Introductionmentioning

confidence: 83%

Generalized monitor unit calculation for the Varian enhanced dynamic wedge field

et al. 2003

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“…The EDW has been studied by many authors. [5][6][7][8][9][10][11][12][13][14][15][16] It presents many advantages over the physical wedge. However, in order to calculate MUs necessary to deliver a certain dose at a certain point, EDW factors need to be determined.…”

Section: Introductionmentioning

confidence: 99%

“…However, this formula is not short, and the procedures for the determination of the fitting parameters are not simple. In the same year, Papatheodorou et al 15 also put forward an algorithm to calculate EDWFs, and their algorithm basically was a straightforward MU fraction model. In general, calculated EDWFs from their formula agreed with corresponding measured values quite well for symmetric and asymmetric fields, but discrepancies in the order of 3% were found for some large 6 MV asymmetric fields.…”

Section: Introductionmentioning

confidence: 99%

Analytical representation of enhanced dynamic wedge factors for symmetric and asymmetric photon fields

2002

Medical Physics

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The Enhanced Dynamic Wedge (EDW) presents many advantages over the physical wedge. However, in order to calculate monitor units (MUs) necessary to deliver a certain dose at a certain point, EDW factors (EDWFs) need to be determined. In this work, based on analysis of the golden segmented treatment table (GSTT) and the MU fraction model, an empirical analytic formula has been developed to calculate EDW factors for symmetric and asymmetric fields. This formalism is an extension of the MU fraction model. However in comparison with previous studies [J. P. Gibbons, Med. Phys. 25, 1411-1418 (1998) and M. Miften et al., Med. Dosim. 25, 81-86 (2000)], this formula is simpler, and easier to use. It is applicable to EDW fields of different sizes, wedge angles and different photon energies. For 6 and 18 MV beams from a Varian 21EX accelerator with 7 EDW angles (Varian Oncology Systems, Palo Alto, CA), more than 250 measured EDWFs for symmetric and asymmetric fields with different off-axis distances and field sizes were compared with model calculations. Results show that 80% and 98% of calculated EDWFs match corresponding measured values to within 0.5% and 1.0%, respectively, the maximum deviation being 1.3%.

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“…The question is whether the current linear accelerator technology is compatible with the simultaneous operations of BSRT and IMRT, i.e., do the gated operations of a linear accelerator maintain the intended IMRT dose delivery? Similarly, do the gated operations of a linear accelerator maintain the enhanced dynamic wedge [17][18][19][20][21] dose profiles?…”

Section: Introductionmentioning

confidence: 99%

Compatibility of Varian 2100C gated operations with enhanced dynamic wedge and IMRT dose delivery

Kubo

Wang

2000

Medical Physics

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An enhanced dynamic wedge (EDW) is one of the latest technical innovations frequently used in the radiotherapy department. Its usage is enthusiastically supported by radiation therapists. Intensity modulated radiotherapy (IMRT) is the other, which has become popular within the past several years. Its usage is not as straightforward as the EDW. However, its ability to further increase dose conformity to the target and to spare the surrounding normal tissues has been evidenced. Both of these treatment modalities demand sophisticated software, which controls precision motion and speed of jaws or multileaf collimators as well as dose rate. This paper deals with the question of how accurately the EDW profiles and IMRT dose distributions be maintained when the additional constraint of linear accelerator gating is invoked. For this, square pulses mimicking breathing were used in gated and nongated modes for film dosimetry and ion chamber measurements using the Varian 2100C linear accelerator. The results show no observable difference between gated and nongated EDW profiles and IMRT dose distribution regardless of the machine repetition rate. Also studied in this paper are the "fuzzy" dose distributions caused by realistic finite gate window settings.

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The `equivalent wedge' implementation of the Varian Enhanced Dynamic Wedge (EDW) into a treatment planning system

Cited by 15 publications

References 19 publications

Generalized monitor unit calculation for the Varian enhanced dynamic wedge field

Generalized monitor unit calculation for the Varian enhanced dynamic wedge field

Analytical representation of enhanced dynamic wedge factors for symmetric and asymmetric photon fields

Compatibility of Varian 2100C gated operations with enhanced dynamic wedge and IMRT dose delivery

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