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ESTRO SBRT course Sept 2015
21
Recently… New identical Linac…
Why did QART fail?
•
Full tests from CT scanning to irradiation of phantoms have been
performed. The measurements were performed on the right linac. The
calculations were performed using the existing Linac model in the TPS.
•
Routinely EPID patient dosimetry QA is performed at this institution. This
is a relative measurement (scaled to coincide with calculations in
normalisation point). Occasionally Matrix-measurements are performed at
a linac, e.g., if beams do not fit on the EPID. However, on the new linac
only small fields were used. (HD 2.5 mm MLC)
•
Also weekly Matrix measurements are performed. However, a different
algoritm is used for this.
•
MU-check accepts 10% deviations. In general, for the existing HD MLC with
2.5 mm leaves the deviations were already a bit bigger than for other
linacs with other MLCs.