Assessment of X-Ray Crosstalk in a Computed Tomography Scanner with Small Detector Elements Using Monte Carlo Method

Document Type : Original Paper

Authors

1 Department of Biomedical Engineering, Faculty of Engineering, University of Isfahan, Isfahan, Iran

2 Department of Biomedical Engineering - Faculty of Engineering- University of Isfahan

3 Department of nuclear Engineering, Faculty of new science and technologies, University of Isfahan, Isfahan, Iran

Abstract

Introduction: Crosstalk is a leakage of X-ray or light produced in a matrix of X-ray detectors or array of photodiodes in one element to other elements affecting on image contrast and spatial resolution. In this study, we assessed X-ray crosstalk in a computed tomography (CT) scanner with small detector elements to estimate the effect of various parameters such as X-ray tube voltage, detector element sizes, scintillator material, impurities in the scintillator material, and the material of detector separators on X-ray crosstalk.
Materials and Methods: This study was performed using Monte Carlo simulation. In the first step, X-ray tube and its energy spectrum at the energies of 80, 100, 120, and 140 keV were simulated and validated by using SpekCalc and t-test. Then, other important parts of CT scanner, namely filters, detectors, and grids were simulated. X-ray crosstalk between CT detectors was calculated in air and in the presence of water phantom (as a simulator of human body) to compare the effect of scattered photons. Finally, the influence of some important parameters on X-ray crosstalk was evaluated.
Results: In CT scanner with small elements, when using phantom, crosstalk increases by 16-50%. Using the lowest possible energies of X-ray, decreases the crosstalk up to 43% of its initial amount. Furthermore coating a 10 or 20 µm layer of tungsten or lead on the detector separators, decreases the X-ray crosstalk significantly.
Conclusion: Choosing the proper high voltage, detectors’ material and its dimensions, scintillator impurities and septa material can decrease X-ray crosstalk.

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References

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History

  • Receive Date: 19 September 2017
  • Revise Date: 20 October 2017
  • Accept Date: 23 October 2017

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