Verification of the influence of the sampling aperture on the digital noise power spectrum

Congress:

ECR 2020

Poster Number:

C-04596

Type:

Scientific Exhibit

Keywords:

Image Quality, Radiation physics, Conventional radiography, Digital radiography, Experimental investigations, Physics, Image verification, Not applicable, Experimental, Performed at one institution

Authors:

S. Maruyama¹, M. Shimosegawa²; ¹Takasaki-shi, Gunma/JP, ²Maebashi-shi/JP

DOI:

10.26044/ecr2020/C-04596

DOI-Link:

https://dx.doi.org/10.26044/ecr2020/C-04596

Fig. 1: Definitions of measures used in this study.

Fig. 2: Geometry of the simulation used for calculating the NPS.

Fig. 3: Geometry of the experimental measurement used for calculating the NPS.

Fig. 4: Definitions of the correction factor used in this study.

Purpose

Various image quality characteristics are evaluated for digital imaging systems. Among them, the noise power spectrum (NPS) gauges granularity in the spatial frequency domain. It has been reported that digital NPS, measured using a direct-type FPD or photon-counting detector, is approximately flat with respect to frequency [1,2]. These findings contradict the established concept that digital NPS decreases in proportion to the square of the presampled modulation transfer function (MTF) [3,4]. Several studies based on the NPS measurement results have been conducted to better understand the...

Methods and materials

Simulation An image formation simulation was performed, assuming a direct-type FPD with ideal X-ray absorption characteristics, such that it has no unsharpness component other than the sampling aperture, and no noise factors other than quantum mottle [10,11]. In this study, we applied a Monte Carlo simulation: Electron Gamma Shower Ver.5 [12]. Figure 1 shows the definitions of measures used in this study. To verify the aperture size dependency of the NPSdigital(u),the sampling aperture was 0.02, 0.05, 0.1, and 0.2 mm, and X-ray photons were uniformly...

Results

To confirm the validity of the MTF calculated from the edge image obtained by the constructed simulation, the sinc function and the MTF were compared as shown in figure 6. It was possible to examine what factors cause the quantum mottle blurring in the detector, and the value for NPSdigital(u),by conducting the simulation with clear conditions concerning the quantum mottle and unsharpness component, without other noise factors. As a result, it was found that even if the aperture changes,NPSdigital(u)is a constant value, which corresponds toNPSquantum...

Conclusion

To clarify the factors influencing NPSdigital(u),we conducted verification using Monte Carlo simulation and experimental measurement. The simulation revealed the measuredNPSdigital(u)was in good agreement withNPSquantum mottle(u),but the NPS accounting for the unsharpness due to the sampling aperture showed different results. These results were verified by experimental measurement, which also supported the simulation result and clarify thatNPSdigital(u)is not affected by the sampling aperture. Although a detailed simulation was carried in this study, all types of detectors were not verified by the experimental measurement. Therefore, it should be...

Personal information and conflict of interest

S. Maruyama; Takasaki-shi, Gunma/JP - nothing to disclose M. Shimosegawa; Maebashi-shi/JP - nothing to disclose

References

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