title: Observations regarding the x-ray beams from the Philips RT-305 therapy machine.
abstract: A Philips RT-305 X-ray therapy unit was found to produce beams of considerable asymmetry. This has been corrected by use of a small wedge-shaped symmetry filter, placed close to the X-ray tube. The symmetry filter has only a small effect on depth doses and half-value layers.
mesh_terms: D005374:Filtration; D006801:Humans; D011879:Radiotherapy Dosage; D013679:Technology, Radiologic; D014965:X-Rays