title: Elongation effects on the Therac 6 linear accelerator.
abstract: The effects of field elongation on the central-axis output at dmax and on the depth-dose curves for the 6-MV x rays from the Therac 6 linear accelerator are considered. These parameters are independent of the collimator angle for both square and elongated fields. The exchange of collimator pairs results in significant output differences but has a negligible effect on the depth-dose curves. Both the central-axis output at dmax and the depth-dose curves agree satisfactorily with the predictions of the equivalent-square technique. An alternative method of greater accuracy is also indicated for the prediction of central-axis outputs at dmax for elongated fields.
mesh_terms: D006801:Humans; D010315:Particle Accelerators; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000295:instrumentation*