Multileaf collimator interleaf transmission

Balog, John; Mackie, T; Wenman, D; Glass, M.; Fang, Guang; Pearson, D.W.

doi:10.1118/1.598501

Cited by 39 publications

(28 citation statements)

References 18 publications

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“…Note also that the tongue‐and‐groove width used in the model is not physically real, as the accelerator has defocused leaves without a physical tongue and groove. ( 9 , 10 ) This approximated behavior in

{Pinnacle}^{3}

and other treatment planning systems is well known. ( 5 ) The physical speeds of the gantry, collimators, and MLC leaves are also chosen to be slightly conservative so as not to stress the delivery system, in accord with our clinical VMAT procedure.…”

Section: Discussionmentioning

confidence: 77%

Beam modeling and VMAT performance with the Agility 160‐leaf multileaf collimator

Bedford

Thomas

Smyth

2013

J Applied Clin Med Phys

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The Agility multileaf collimator (Elekta AB, Stockholm, Sweden) has 160 leaves of projected width 0.5 cm at the isocenter, with maximum leaf speed 3.5cms−1. These characteristics promise to facilitate fast and accurate delivery of radiotherapy, particularly volumetric‐modulated arc therapy (VMAT). The aim of this study is therefore to create a beam model for the Pinnacle3 treatment planning system (Philips Radiation Oncology Systems, Fitchburg, WI), and to use this beam model to explore the performance of the Agility MLC in delivery of VMAT. A 6 MV beam model was created and verified by measuring doses under irregularly shaped fields. VMAT treatment plans for five typical head‐and‐neck patients were created using the beam model and delivered using both binned and continuously variable dose rate (CVDR). Results were compared with those for an MLCi unit without CVDR. The beam model has similar parameters to those of an MLCi model, with interleaf leakage of only 0.2%. The verification of irregular fields shows a mean agreement between measured and planned dose of 1.3% (planned dose higher). The Agility VMAT head‐and‐neck plans show equivalent plan quality and delivery accuracy to those for an MLCi unit, with 95% of verification measurements within 3% and 3 mm of planned dose. Mean delivery time is 133 s with the Agility head and CVDR, 171 s without CVDR, and 282 s with an MLCi unit. Pinnacle3 has therefore been shown to model the Agility MLC accurately, and to provide accurate VMAT treatment plans which can be delivered significantly faster with Agility than with an MLCi.PACS number: 87.55kd, 87.55km, 87.56bd, 87.56jk

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{Pinnacle}^{3}

Section: Discussionmentioning

confidence: 77%

Beam modeling and VMAT performance with the Agility 160‐leaf multileaf collimator

Bedford

Thomas

Smyth

2013

J Applied Clin Med Phys

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“…1-4 Over time, many new MLCs have been developed, tested, and compared. [5][6][7][8][9][10][11][12][13][14][15][16][17][18] Various articles have also been concerned with the theoretical investigation of design principles. [19][20][21][22][23] Initially handled manually but now computer controlled, the MLC allows a precise automatic shaping of the treatment field according to the target outline specified in the treatment planning system.…”

Section: Introductionmentioning

confidence: 99%

6 MV dosimetric characterization of the 160 MLC™, the new Siemens multileaf collimator

et al. 2008

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New technical developments constantly aim at improving the outcome of radiation therapy. With the use of a computer-controlled multileaf collimator (MLC), the quality of the treatment and the efficiency in patient throughput is significantly increased. New MLC designs aim to further enhance the advantages. In this article, we present the first detailed experimental investigation of the new 160 MLC, Siemens Medical Solutions. The assessment included the experimental investigation of typical MLC characteristics such as leakage, tongue-and-groove effect, penumbra, leaf speed, and leaf positioning accuracy with a 6 MV treatment beam. The leakage is remarkably low with an average of 0.37% due to a new design principle of slightly tilted leaves instead of the common tongue-and-groove design. But due to the tilt, the triangular tongue-and-groove effect occurs. Its magnitude of approximately 19% is similar to the dose defect measured for MLCs with the common tongue-and-groove design. The average longitudinal penumbra measured at depth d(max) = 15 mm with standard 100 x 100 mm2 fields is 4.1 +/- 0.5 mm for the central range and increases to 4.9 +/- 1.3 mm for the entire field range of 400 x 400 mm2. The increase is partly due to the single-focusing design and the large distance between the MLC and the isocenter enabling a large patient clearance. Regarding the leaf speed, different velocity tests were performed. The positions of the moving leaves were continuously recorded with the kilovoltage-imaging panel. The maximum leaf velocities measured were 42.9 +/- 0.6 mm/s. In addition, several typical intensity-modulated radiation therapy treatments were performed and the delivery times compared to the Siemens OPTIFOCUS MLC. An average decrease of 11% in delivery time was observed. The experimental results presented in this article indicate that the dosimetric characteristics of the 160 MLC are capable of improving the quality of dose delivery with respect to precision and dose conformity.

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“…20,21 In addition, the planning system needs dosimetric information of beam size as small as 0.5ϫ 0.5 cm 2 -which is more refined than the typical non-IMRT commissioning beam data such as relative dose outputs and ratios measured from 4 ϫ 4 cm 2 to the maximum field size-because the small beamlets in the range of 0.5 ϫ 0.5 cm 2 in the general MLC-based IMRT 21 are usually used. Although many people have focused on different MLC dosimetric characteristics such as leaf leakage, transmission and penumbra, [22][23][24][25][26] the effects of the jaw coverage to the leaf-end on the beam characteristics of a small MLC field have not yet been systematically measured.…”

Section: Introductionmentioning

confidence: 99%

Dosimetric effect of collimating jaws for small multileaf collimated fields

2005

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The dosimetric effects from the jaw positioned close to the small field (0.5 x 0.5, 1 x 1, and 2 x 2 cm2) side-edge generated by a single-focused multileaf collimator (MLC) were measured and studied. The measurement is important in intensity modulated radiotherapy (IMRT) because generally the jaw cannot perfectly cover all the leaf-ends in a segment of irregular field. This leads to additional dose contributed by (1) the end surface of the jaw, (2) the leaf-end, and (3) the inter- and intraleaf leakage/transmissions during the dosimetric measurement. Moreover, most of the conventional treatment planning systems ignore these effects in the dose calculation. In this study, measurements were made using a Varian 21 EX linear accelerator with 6 MV photon beam through a MLC containing 120 leaves. Percentage depth dose, beam profile, and output for small fields were measured by varying the jaw at different positions away from the leaf-ends in the field side-edge. Moving the jaw away from the leaf-ends increases the output and penumbra width for the small fields. Such increase is particularly significant when the field size is small (0.5 x 0.5 cm2) and the degree of increase changes quickly when the jaw-end is at about 1-2 cm from the leaf-end. It is suggested that measurements should be carried out in the IMRT commissioning to provide information to physicists in reviewing the treatment planning system's accuracy regarding leaf leakage/transmission and jaw effects.

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Multileaf collimator interleaf transmission

Cited by 39 publications

References 18 publications

Beam modeling and VMAT performance with the Agility 160‐leaf multileaf collimator

Beam modeling and VMAT performance with the Agility 160‐leaf multileaf collimator

6 MV dosimetric characterization of the 160 MLC™, the new Siemens multileaf collimator

Dosimetric effect of collimating jaws for small multileaf collimated fields

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