UNASSIGNED: Ratio of @entity92 ( @entity92 ) at two depths, @entity92 at a depth of 10  cm (PDD10), and beam @entity12318 are monitored regularly for radiotherapy beams for quality assurance. The purpose of this study is to understand the effects of changes in one of these parameters on the other. Is it possible to monitor only the beam @entity12318 and not @entity92 ? The investigation has two components. Naturally occurring i.e., unintended changes in @entity92 ratio and in-plane @entity12318 for 6 and 10 MV photon beams for one particular @entity5377 Artiste Linac are monitored for a period of about 4  years. Secondly, deliberate changes in the beam parameters are induced by changing the bending magnet current (BMI). Relationships between various beam parameters for unintended changes as well as deliberate changes are characterized. Long term unintentional changes of @entity92 ratio are found to have no systematic trend. The @entity12318 in the inplane direction for 6 and 10 MV beams show slow increase of 0.43 and 0.75  % respectively in about 4  years while the changes in the @entity92 ratio show no such trend. Over 10  % changes in BMI are required to induce changes in the beam quality indices at 2  % level. @entity92 ratio for the 10 MV beam is found to be less sensitive, while the depth of maximum dose, dmax, is more sensitive to the changes in BMI compared to the 6 MV beam. Tolerances are more stringent for PDD10 than @entity92 ratio for the 10 MV beam. @entity92 ratio, PDD10, and @entity12318 must be monitored independently. Furthermore, off axis ratio alone cannot be used to monitor @entity12318 . The effect of beam quality change in the absolute dose is clinically insignificant.

On beam quality and XXXX of radiotherapy megavoltage photon beams.

@entity5377 :: ('MESH:D053560', 'Disease') :: ['Siemens'] @entity92 :: ('MESH:D007222', 'Disease') :: ['PDD', 'percentage depth dose'] @entity12318 :: ('MESH:D005413', 'Disease') :: ['flatness']
@entity12318 :: (MESH:D005413,Disease) :: ['flatness']
