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 can 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.