Show simple item record

dc.contributor.authorHounsell, Alan R
dc.contributor.authorWilkinson, John M
dc.date.accessioned2010-03-24T15:29:51Z
dc.date.available2010-03-24T15:29:51Z
dc.date.issued1997-09
dc.identifier.citationHead scatter modelling for irregular field shaping and beam intensity modulation. 1997, 42 (9):1737-49 Phys Med Biolen
dc.identifier.issn0031-9155
dc.identifier.pmid9308080
dc.identifier.doi10.1088/0031-9155/42/9/006
dc.identifier.urihttp://hdl.handle.net/10541/94922
dc.description.abstractScattered radiation from within the treatment head can contribute significant dose to all parts of a radiotherapy treatment field. A multileaf collimator may be used to create an arbitrarily shaped field, and may also be used, under dynamic control, to modulate the beam intensity over the field. This method of intensity modulation is effectively a superposition of a large number of fields which have the same beam direction, but different shapes, and some of these shapes may have unusually small dimensions, particularly in the direction of the leaf movement. Two models for predicting the head scatter under these conditions have been investigated. These are a first-order Compton scatter approximation from the flattening filter, and an empirical fit to measured data using an exponential function. The first model only considers scatter from the flattening filter and has been applied to field sizes between 2 cm by 2 cm and 10 cm by 10 cm, where agreements are all within 1%. However it is not satisfactory at larger field sizes where small scatter contributions, from scattering sources other than the flattening filter, are integrated over large areas. The second model uses measured data between 4 cm by 4 cm and 30 cm by 30 cm to optimize the exponential function and is used to calculate the head scatter contribution for all field sizes. In this case good agreement is achieved over the full field size range, and hence this is a more generally applicable model. Results are presented for static irregularly shaped fields and intensity modulated beams created using a Philips multileaf collimator.
dc.language.isoenen
dc.subject.meshBiophysical Phenomena
dc.subject.meshBiophysics
dc.subject.meshEquipment Design
dc.subject.meshHumans
dc.subject.meshModels, Theoretical
dc.subject.meshParticle Accelerators
dc.subject.meshRadiometry
dc.subject.meshRadiotherapy, High-Energy
dc.subject.meshScattering, Radiation
dc.titleHead scatter modelling for irregular field shaping and beam intensity modulation.en
dc.typeArticleen
dc.contributor.departmentNorth Western Medical Physics, Christie Hospital NHS Trust, Manchester, UK. phyarh@picr.cr.man.ac.uken
dc.identifier.journalPhysics in Medicine and Biologyen
html.description.abstractScattered radiation from within the treatment head can contribute significant dose to all parts of a radiotherapy treatment field. A multileaf collimator may be used to create an arbitrarily shaped field, and may also be used, under dynamic control, to modulate the beam intensity over the field. This method of intensity modulation is effectively a superposition of a large number of fields which have the same beam direction, but different shapes, and some of these shapes may have unusually small dimensions, particularly in the direction of the leaf movement. Two models for predicting the head scatter under these conditions have been investigated. These are a first-order Compton scatter approximation from the flattening filter, and an empirical fit to measured data using an exponential function. The first model only considers scatter from the flattening filter and has been applied to field sizes between 2 cm by 2 cm and 10 cm by 10 cm, where agreements are all within 1%. However it is not satisfactory at larger field sizes where small scatter contributions, from scattering sources other than the flattening filter, are integrated over large areas. The second model uses measured data between 4 cm by 4 cm and 30 cm by 30 cm to optimize the exponential function and is used to calculate the head scatter contribution for all field sizes. In this case good agreement is achieved over the full field size range, and hence this is a more generally applicable model. Results are presented for static irregularly shaped fields and intensity modulated beams created using a Philips multileaf collimator.


This item appears in the following Collection(s)

Show simple item record