Evaluation of influence of scattered x rays on signal sharpness of radiographs produced by using a CR system

Kouji Maeda; Hidetaka Arimura; Ikuo Kawashita; Kaoru Morikawa; Takayuki Ishida; Masao Matsumoto; Hitoshi Kanamori

doi:10.1117/12.465613

3 May 2002 Evaluation of influence of scattered x rays on signal sharpness of radiographs produced by using a CR system

Kouji Maeda, Hidetaka Arimura, Ikuo Kawashita, Kaoru Morikawa, Takayuki Ishida, Masao Matsumoto, Hitoshi Kanamori

Proceedings Volume 4682, Medical Imaging 2002: Physics of Medical Imaging; (2002) https://doi.org/10.1117/12.465613
Event: Medical Imaging 2002, 2002, San Diego, California, United States

Abstract

The purpose of this study is to investigate the influence of the scattered x rays on the signal sharpness on the radiographs produced by using a computed radiography (CR) system by measuring the spatial frequency spectra of the signal image. By using a 0.1 mm slit on the polymethyl methacrylate (PMMA) for thicknesses of 0.5 cm to 20.5 cm, the slit images were acquired as a signal by use of imaging plates at tube voltages of 50 kV to 120 kV. The relative exposure profiles for the slit images were Fourier transformed to obtain the spatial frequency spectra. For comparison of the frequency spectra with and without the scattered x rays, we defined the scattered x-ray influence factor (SIF) representing the magnitude of the influence of the scattered x rays on the spatial frequency spectra of the signal image. To investigate the contribution of the primary and scatter components to the degradation of the signal sharpness, we proposed a method for separating the spatial frequency spectrum of the signal image into the primary and scatter components. By obtaining the SIF, we found that, for very lower frequencies (less than about 0.3 mm^-1), the shape of the spatial frequency spectra of the signal image depends on the scattered x rays, but, for higher frequencies, hardly depends. As a result of the separation of the frequency spectra of the signal image, we found that the contribution of the scatter component for very lower frequencies (less than about 0.2 mm^-1) to the total spectrum of the signal image was not negligible and became greater as the scattering material thickness and the tube voltage increased. On the contrary, for higher frequencies, the primary component was dominant compared with the scatter component for all thicknesses and tube voltages.

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Kouji Maeda, Hidetaka Arimura, Ikuo Kawashita, Kaoru Morikawa, Takayuki Ishida, Masao Matsumoto, and Hitoshi Kanamori "Evaluation of influence of scattered x rays on signal sharpness of radiographs produced by using a CR system", Proc. SPIE 4682, Medical Imaging 2002: Physics of Medical Imaging, (3 May 2002); https://doi.org/10.1117/12.465613

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KEYWORDS

Spatial frequencies

Scattering

Radiography

X-rays

Polymethylmethacrylate

Chromium

Image sensors

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