Imagequality assessment method for digital phase

Authors: Satoru Matsuo Junji Morishita Tetsuro Katafuchi Chika Honda Hiroshi Fujita

Publish Date: 2011/11/10

Volume: 5, Issue: 1, Pages: 78-85

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Abstract

With use of the phase shift of Xrays that occurs when they pass through an object phasecontrast imaging herein referred to as “phase imaging” can produce images different from those of conventional contact imaging herein referred to as “conventional imaging” For this reason assessment of the image quality based on noiseequivalent quanta NEQ and detective quantum efficiency DQE which does not include objectbased information may not be appropriate for comparison of image quality between phase and conventional images As an alternative method we conceived a new imagequality assessment method with images that contain information about an object First we constructed images with an object and without an object under the same imaging parameters then we obtained twodimensional power spectra by Fourier transform of those images Second we calculated the radial direction distribution function with the power spectra and the distribution of signal intensity which we defined as a signal intensity distribution function SIDF In this way differences in image quality were evaluated relatively based on the SIDF of the imaged object In our study we first confirmed that phaseimaging evaluation was not appropriate by comparing NEQ and DQE of conventional magnification and phase imaging Further comparing the image quality of projected plant seeds by employing conventional magnification and phase imaging we found that the phaseimaging method provided a higher image quality regarding edge sharpness than did conventional and magnification imaging Therefore based on these results our image assessment method is considered useful for evaluation of images which include objectbased informationThe authors appreciate fruitful discussions with Mr Hiromu Ohara of Konica Minolta Medical and Graphic Inc We also thank Prof Kiyoshi Murata of the Shiga University of Medical Science and Mr Masatake Imai of the Shiga University of Medical Science Hospital for their permission to publish this work

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