AbstractID: 7770 Title: Dose Stability for Low Monitor Unit Treatments
With the advent of low MU segments with IMRT treatments the beam stability at the initial beam on time becomes much more
critical. This beam stability is studied with respect to the time it takes to reach full dose and its effect on the beam profile. The control
electronics as well as the rf components contribute toward this buildup time. It is shown that by improving the automatic frequency
control (AFC) circuitry, as well as the rate at which the rf driver can change frequency, a significant improvement can be made with
beam stability at the onset of dose pulsing. Preliminary measured data indicate that an improvement from approximately 300 m-sec to
55 m-sec can be observed. This results in full dose stability in significantly less than 1 MU delivered dose. This has substantial impact
on the delivery of a fraction of a single monitor unit and will set the standard in dose stability for all linear accelerator manufacturers.
Research supported by Siemens Medical Solutions.