Comparison of 4 MV photon surface dose among Varian, Siemens, and Elekta linear accelerators for tangential breast treatment: a phantom study.
OBJECTIVE
We have compared the differences in a 4-MV photon surface dose among Varian, Siemens, and Elekta linear accelerators (linacs) with wedges for tangential breast treatment.


METHODS
The wedge factor and the surface dose were measured using a solid water phantom and an ion chamber for each linear accelerator with various field sizes and wedge angles. A tangential treatment plan was applied to an elliptical hollow cylinder water phantom with a radiochromic film placed thereon. A dose was delivered to a simulated target in the phantom, and the resulting dose distribution was analyzed using a film scanner.


RESULTS
Varian's wedges resulted in the highest wedge factors, ranging from 0.37 to 0.75 depending on the wedge angles. Varian's wedges led to the highest normalized skin doses, ranging between 0.40 and 0.73 depending on the wedge angles and field sizes. In the cylinder phantom test with two tangential beams, the Varian linac provided a nearly 20% higher maximum dose than the Siemens and Elekta linacs.


CONCLUSIONS
The Varian linac resulted in the highest surface doses, and the Elekta linac led to the lowest for nearly all the measurement conditions we employed, including open beams.
Yamaguchi
Satoshi
S
Department of Radiology, Graduate School of Medicine, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan. syama@med.juntendo.ac.jp
Karasawa
Kumiko
K
Furuya
Tomohisa
T
Fujita
Takayuki
T
Tutumi
Yutaka
Y
Miura
Kohei
K
Takada
Takahiro
T
Ito
Kana
K
Ozawa
Shuichi
S
D001941:Breast Diseases / Q000532:radiotherapy*; D006801:Humans; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D017785:Photons; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000295:instrumentation*