An anterior appositional electron field technique with a hanging lens block in orbital radiotherapy: a dosimetric study.
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.
Borger
F
F
Department of Radiation and Cellular Oncology, Michael Reese/University of Chicago, IL.
Rosenberg
I
I
Vijayakumar
S
S
Virudachalam
R
R
Schneider
D
D
Langmuir
V
V
Chen
G T
GT
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
D013193:Stainless Steel