PMID: 8587526Nov 1, 1995Paper

Dynamic universal wedge

Medical Physics
H ShackfordP Vadash

Abstract

A computer-controlled equivalent of the universal wedge was designed by moving one collimator with step-wise constant velocity to produce the same primary-dose profile as a 20x20-cm2 conventional 58-deg wedge. It was used for smaller fields without changing the profile and combined with open beams to alter the wedge angle. Output factors in air and wedge factors in air and water were determined experimentally for the dynamic wedge and compared to predictions based on the assumption that the primary dose is proportional to the number of monitor units that the point of interest is in the open portion of the beam. This model was found to be accurate within about 2% and the deviations caused by head-scatter changes and collimator transmission after the moving collimator has passed. Measurements of the wedge factor in water indicated that the scatter factors for large wedged beams slightly exceeded those for open beams.

Citations

Feb 13, 2001·Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology·T KnöösP Nilsson
Oct 10, 2008·Medical Physics·Indra J DasUNKNOWN TG-106 of the Therapy Physics Committee of the AAPM
Sep 2, 1998·Medical Physics·B D MillikenJ W Wong
Aug 18, 2000·Medical Physics·M H PhillipsP S Cho
Jan 1, 2000·Physics in Medicine and Biology·F Verhaegen, I J Das
Jan 24, 2003·Journal of Applied Clinical Medical Physics·Nzhde AgazaryanJohn J DeMarco

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