Static and rotational output variation of a tomotherapy unit.

A simple device to check the machine output in rotational mode is described. Integral and instantaneous beam output in absolute dose can be measured and analyzed in a very simple manner. A method to correlate the results with the value obtained during the machine calibration in static beam and the reference value used by the treatment planning system for dose calculation in rotation beam is also described. Using this method and device, the daily output can be performed in rotational conditions which are closer to the treatment conditions. Measurement results using this device show differences in the beam output between static and rotational delivery which have to be considered carefully during the calibration process.