Effect of collimator setting on the output of rectangular fields from linear accelerators.
The output (cGy/mu) of a rectangular field from a linear accelerator is not always the same as that of its equivalent square field. We have summarized output variations with upper and lower collimator setting for 4, 6, and 24 MV X-rays. It is concluded that an error in output on the order of a few percent is introduced for elongated fields if lower set of collimator jaws is used for setting the longer dimension of the field, and computing the output using equivalent square method. It is recommended that specific guidelines be developed regarding rectangular field setting on high energy linacs.
Jani
S K
SK
Division of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City 52242.
Pennington
E C
EC
Wacha
J E
JE
Anderson
K M
KM
D006801:Humans; D010315:Particle Accelerators; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000295:instrumentation*