The O-arm system is a mobile intraoperative imaging system that is comprised of fluoroscopy and cone beam CT. The
configuration of the O-arm system with absence of patient table and a broad beam width (165 mm in isocenter) brings
new practical and physical requirements on how to perform dose measurements. The purpose of this study was to
describe a method that overcomes this and makes it possible to characterize the radiation output from the O-arm system.
A holder with a clamp and a flexible ball joint that can orientate the radiation detector support and the Mover that can be
adjusted to hold the dose detector in a horizontal position was used. Evaluation of the dose response for three different
dose detectors of different active length (0.3, 23.1 and 100 mm) was made for three different beam qualities.
Furthermore the dose profile free in air to control the possible heel effect and width of the x-ray field during rotation was
measured and the dose rate waveform was analyzed. The FWHM of the dose profile was 162 mm. The dose response of
the three detectors is reported. The average dose response was lower for the detector with longer active length due to the
influence of the dose profile shape. From dynamic measurement total exposure time, pulse width, and the number of
pulses were verified. In conclusion, an external horizontal hanging holder with mover option helps to assist to make dose
measurement easier and enables characterize the radiation output from the O-arm system.