Technical Note: Output and energy fluctuations of the tomotherapy Hi-Art helical tomotherapy system

The output and energy calibrations for the first clinical Hi-Art 2.0 helical tomotherapy system have been reviewed. Fixed-gantry/fixed-couch and rotational-gantry/fixed-couch measurements were made on a daily basis over a period of 20 weeks to investigate system stability. Static gantry measurements were taken at 10 cm depth in a rectangular stack of Virtual Water at an SSD distance of 90 cm and a field size of 5×40 cm . Rotational gantry measurements were taken in a cylindrical phantom Virtual Water phantom for a field size of 5×40 cm . The Hi-Art 2.0 system has maintained its calibration to within ±2% and energy to within ±1.5% over the initial 20 week period.