title: The 62 MeV proton beam for the treatment of ocular melanoma at Clatterbridge.
abstract: A second treatment room and beam line has been constructed at the Cyclotron Unit at Clatterbridge for the purpose of using 62 MeV protons for the treatment of ocular melanoma. A uniform beam is produced by a double foil scattering system. The initial Bragg peak is spread across the target volume by the use of beam modulators. These are rotating four-vaned stepped absorbers made from Perspex. Two beam lines can be configured with different positions of modulators and range limiters. The first has a maximum penetration of 31.9 +/- 0.2 mm in water and the second a penetration of 31.2 +/- 0.2 mm. The second configuration has the advantage of less variation in beam penumbra, with a typical value of 1.7 +/- 0.1 mm for the 90% to 10% decrement lines. The patients are treated with individually shaped collimators. Beam output varies by less than 2% over the range of collimator areas used. The resulting whole-body dose equivalent to patient has also been assessed. In the first three years of operation over 250 patients have been treated.
authors.affiliation: MRC Cyclotron Unit, Clatterbridge Hospital, Bebington, Merseyside, UK.
authors.forename: D E
authors.initials: DE
authors.lastname: Bonnett
authors.forename: A
authors.initials: A
authors.lastname: Kacperek
authors.forename: M A
authors.initials: MA
authors.lastname: Sheen
authors.forename: R
authors.initials: R
authors.lastname: Goodall
authors.forename: T E
authors.initials: TE
authors.lastname: Saxton
mesh_terms: D005134:Eye Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008545:Melanoma / Q000532:radiotherapy*; D011522:Protons; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy; D012542:Scattering, Radiation
chemical_list: D011522:Protons