Effect of spatial direction and acquisition techniques on noise power spectra in x-ray CT

Kirsten Boedeker; Alexander A. Zamyatin; Xiaofei Wang

doi:10.1117/12.772960

3 April 2008 Effect of spatial direction and acquisition techniques on noise power spectra in x-ray CT

Kirsten Boedeker, Alexander A. Zamyatin, Xiaofei Wang

Proceedings Volume 6913, Medical Imaging 2008: Physics of Medical Imaging; 69134X (2008) https://doi.org/10.1117/12.772960
Event: Medical Imaging, 2008, San Diego, California, United States

Abstract

The spatial characteristics of noise in X-ray CT can influence object detectability. Now, as three dimensional image reformations become more clinically common, it has become vital to understand the structure of noise in the x, y, and z directions independently. The purpose of this paper is to study noise structure in the radial direction and tangential direction, under varying conditions, including a wedge filter and acquisition techniques (i.e. half scan vs full scan). Because the effect of the reconstruction algorithm on an image is highly dependent on spatial location within the field of view, the effect of off-center vs centered positioning in each direction is also examined. The noise spatial frequency distribution was investigated via calculation of the noise power spectrum (NPS) through Fourier methods on simulated water images. As expected, noise structure at center was equivalent in both the radial and tangential directions. Towards the periphery, overall noise power was muted. However, in the tangential direction high frequency noise power was preserved more than twice as much as in the radial direction. Towards the periphery noise becomes more low-frequency in the radial direction, while in the tangential direction it becomes more high-frequency. The half scan increased both noise magnitude and low-mid spatial correlation in the NPS compared to full scan. In conclusion, noise spatial structure is directionally dependent off-center and this may have an impact on object detectability in directional reformations.

Citation Download Citation

Kirsten Boedeker, Alexander A. Zamyatin, and Xiaofei Wang "Effect of spatial direction and acquisition techniques on noise power spectra in x-ray CT", Proc. SPIE 6913, Medical Imaging 2008: Physics of Medical Imaging, 69134X (3 April 2008); https://doi.org/10.1117/12.772960

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