title: Skin dose reduction by a clinically viable magnetic deflector.
abstract: A variable magnetic deflector which attaches onto the treatment head of a linear accelerator has reduced skin dose by as much as 65% for 6MV x-rays. The magnetic deflector is constructed from Neodymium Iron Boron (NdFeB) rare earth magnets. It weighs approximately 15 kg and is designed to easily fit onto the accessory mount of a clinical linear accelerator. All field sizes are attainable up to 35 cm x 35 cm at 100 cm SSD. The gap between the magnetic poles can be adjusted, providing the highest field strength for each field size. Magnetic field strengths up to 0.55 Tesla are attainable. For a 6MV x-ray beam with a 10 mm perspex block tray, surface dose is reduced from 29% to 14% and from 59% to 37% for a 20 cm x 20 cm and 35 cm x 35 cm field size, respectively. Results at varying SSD's have shown at least 10 cm of space must be allowed between the magnets and patient for adequate reduction of skin dose through removal of electron contaminants.
authors.affiliation: Illawarra Cancer Care Centre, Department of Radiotherapy, Wollongong NSW, Australia.
authors.forename: M J
authors.initials: MJ
authors.lastname: Butson
authors.forename: P
authors.initials: P
authors.lastname: Yu
authors.forename: M
authors.initials: M
authors.lastname: Kan
authors.forename: M
authors.initials: M
authors.lastname: Carolan
authors.forename: E
authors.initials: E
authors.lastname: Young
authors.forename: J N
authors.initials: JN
authors.lastname: Mathur
authors.forename: P E
authors.initials: PE
authors.lastname: Metcalfe
mesh_terms: D006801:Humans; D008280:Magnetics; D010315:Particle Accelerators / Q000295:instrumentation*; D011835:Radiation Protection / Q000295:instrumentation*; D012867:Skin / Q000528:radiation effects*