Simplified block diagrams of (a) the DPP system and (b) an analog detection system.
(a) An overview of the LAX facility. (b) The detector chamber located at 10.5 m from the x-ray tube; the detection system was mounted on a XYZ microtranslator system.
The experimental set-up for the Mo-target x-ray spectrum measurements under clinical conditions.
The measured spectra at (a) low and (b) high photon counting rate. The events between 40 and 50 keV are due to peak pile-up. The counts were normalized to the total number of detected events.
The distribution of the peaking times of the detected events at 512 kcps and the selected peaking time regions (PTRs).
The energy spectra for the selected PTRs. It is evident that the peak-pile events are characterized by longer peaking times than the correct events.
The measured spectrum at high photon counting rate after applying the pulse shape discrimination (PSD) technique. The number of the peak pile-up events is less than 2.5%. The counts were normalized to the total number of detected events.
Estimated true photon counting rate versus the tube current at 28 and 32 kV. Non-linearity is less than 0.6% up to 358 kcps. Errors are too small to be visible in the figure (statistical errors with a confidence level of 68%).
The Mo-target x-ray spectra measured with the analog system with a peaking time of 630 ns (a) at 9852 cps and (c) 358 kcps; the measured spectra with the DPP system (b) at 9852 cps and (d) 358 kcps. The counts were normalized to the total number of detected events.
Calculated tube voltage values vs. photon counting rate. Statistical errors with a confidence level of 68% were associated.
The Mo-target x-ray spectra measured with the DPP system under clinical conditions; (a) at 26 kV, (b) at 28 kV and (c) at 30 kV. The counts were normalized to the total number of detected events.
Attenuation curves obtained from measured and simulated spectra and from direct exposure measurements. The tube settings were: 28 kV and 20 mAs. Errors of ionization chamber measurements are too small to be visible in the figure.
Spectroscopic results for the CdTe detection system.
Results for the clinical Mo-target x-ray spectrum measurements. Tube settings: 26, 28, 30 KV and 20 mAs. The acquisition time is equal to 0.8 s.
Results for the HVL measurements. The tube settings were 28 kV and 20 mAs. Statistical errors with a confidence level of 68% were associated.
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