High dynamic range x-ray flux monitoring system

In this paper we present a mono pixel detector with a very high dynamic range for measuring the X-ray flux. The flux monitor system is mainly designed for supplementing and improving existing X-ray systems. When using such monitor devices additionally to other X-ray detectors, the monitor signal has to be calibrated versus the detector signal. A suitable calibration routine and its results are shown. The linearity (signal vs. dose) of the monitor was investigated and a highly linear behavior can be observed. In contrast to that, the used X-ray flat panel detector shows a lager non-linear behavior; therefore a non-linear calibration function has to be applied. The monitor was tested in typical computed tomography (CT) applications. Firstly we monitored the primary X-ray flux during a CT measurement close to the X-ray tube. This results in a very high dose rate, but has the benefit that the signal is not distorted by scattered radiation and that the whole detector area ca n be used for imaging (as e.g. in region-of-interest CT). We also monitored the scattered radiation during a CT measurement. In this case it is necessary to measure very low dose rates. The acquired measurements can be used to correct the projection data of the CT scan to improve CT quality.