title: An anterior appositional electron field technique with a hanging lens block in orbital radiotherapy: a dosimetric study.
abstract: A technique for orbital radiotherapy is presented consisting of an anterior, appositional electron beam with a hanging lens block. The beam was modified by introducing two 1.6 mm thick plastic spoilers, at about 3 cm and 15 cm from the lens, to boost in-scattering of electrons under the block. The 9 mm diameter, 2 cm long stainless steel cylindrical block was suspended 0.5-1.0 cm above the eye. We performed film, TLD (Thermo Luminescent Dosimetry), and diode dosimetry to determine the dose fill-in behind the lens. The introduction of the spoilers dramatically changed the dose distribution. The maximum dose under the block increased from 66% to 85% of the open field dose. Moreover, the dose to the posterior surface of the globe directly underneath the block, at a depth of 3 cm, increased from 48% to 76% of maximum dose, while the dose to the lens was still below 20%. This is a simple and easily reproducible treatment and is an improvement on a previously described technique. The dose distribution is adequate for cases where the target volume surrounds and is posterior to the globe.
authors.affiliation: Department of Radiation and Cellular Oncology, Michael Reese/University of Chicago, IL.
authors.forename: F
authors.initials: F
authors.lastname: Borger
authors.forename: I
authors.initials: I
authors.lastname: Rosenberg
authors.forename: S
authors.initials: S
authors.lastname: Vijayakumar
authors.forename: R
authors.initials: R
authors.lastname: Virudachalam
authors.forename: D
authors.initials: D
authors.lastname: Schneider
authors.forename: V
authors.initials: V
authors.lastname: Langmuir
authors.forename: G T
authors.initials: GT
authors.lastname: Chen
mesh_terms: D004583:Electrons; D006801:Humans; D007908:Lens, Crystalline; D009918:Orbital Neoplasms / Q000532:radiotherapy*; D011835:Radiation Protection / Q000295:instrumentation*; D011882:Radiotherapy, High-Energy / Q000379:methods*; D013193:Stainless Steel
chemical_list: D013193:Stainless Steel