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dc.contributor.authorBudgell, Geoff J
dc.contributor.authorMott, Judith
dc.contributor.authorWilliams, Peter C
dc.contributor.authorBrown, K J
dc.date.accessioned2009-11-18T12:24:22Z
dc.date.available2009-11-18T12:24:22Z
dc.date.issued2000-05
dc.identifier.citationRequirements for leaf position accuracy for dynamic multileaf collimation. 2000, 45 (5):1211-27 Phys Med Biolen
dc.identifier.issn0031-9155
dc.identifier.pmid10843101
dc.identifier.doi10.1088/0031-9155/45/5/310
dc.identifier.urihttp://hdl.handle.net/10541/86387
dc.description.abstractIntensity modulated radiation therapy can be achieved by driving the leaves of a multileaf collimator (MLC) across an x-ray therapy beam. Algorithms to generate the required leaf trajectories assume that the leaf positions are exactly known to the MLC controller. In practice, leaf positions depend upon calibration accuracy and stability and may vary within set tolerances. The purpose of this study was to determine the effects of potential leaf position inaccuracies on intensity modulated beams. Equations are derived which quantify the absolute error in delivered monitor units given a known error in leaf position. The equations have been verified by ionization chamber measurements in dynamically delivered flat fields, comparing deliveries in which known displacements have been applied to the defined leaf positions with deliveries without displacements applied. The equations are then applied to two clinical intensity modulations: an inverse planned prostate field and a breast compensating field. It is shown that leaf position accuracy is more critical for a highly modulated low-dose intensity profile than a moderately modulated high-dose intensity profile. Suggestions are given regarding the implications for quality control of dynamic MLC treatments.
dc.language.isoenen
dc.subjectBreast Canceren
dc.subjectProstatic Canceren
dc.subject.meshAlgorithms
dc.subject.meshBiophysical Phenomena
dc.subject.meshBiophysics
dc.subject.meshBreast Neoplasms
dc.subject.meshFemale
dc.subject.meshHumans
dc.subject.meshMale
dc.subject.meshModels, Theoretical
dc.subject.meshProstatic Neoplasms
dc.subject.meshRadiotherapy, Conformal
dc.titleRequirements for leaf position accuracy for dynamic multileaf collimation.en
dc.typeArticleen
dc.contributor.departmentNorth Western Medical Physics, Christie Hospital NHS Trust, Manchester, UK. Geoff.Budgell@physics.cr.man.ac.uken
dc.identifier.journalPhysics in Medicine and Biologyen
html.description.abstractIntensity modulated radiation therapy can be achieved by driving the leaves of a multileaf collimator (MLC) across an x-ray therapy beam. Algorithms to generate the required leaf trajectories assume that the leaf positions are exactly known to the MLC controller. In practice, leaf positions depend upon calibration accuracy and stability and may vary within set tolerances. The purpose of this study was to determine the effects of potential leaf position inaccuracies on intensity modulated beams. Equations are derived which quantify the absolute error in delivered monitor units given a known error in leaf position. The equations have been verified by ionization chamber measurements in dynamically delivered flat fields, comparing deliveries in which known displacements have been applied to the defined leaf positions with deliveries without displacements applied. The equations are then applied to two clinical intensity modulations: an inverse planned prostate field and a breast compensating field. It is shown that leaf position accuracy is more critical for a highly modulated low-dose intensity profile than a moderately modulated high-dose intensity profile. Suggestions are given regarding the implications for quality control of dynamic MLC treatments.


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