N Tsuda¹*, K Mitsui², S Oda³, N Tanaka⁴, H Aibe⁵, (1) Division of Radiology, Saga-ken Medical Centre Koseikan, Saga-shi, ,JP, (2) Division of Radiology, Saga-ken Medical Centre Koseikan, Saga-shi, ,JP, (3) Division of Radiology, Saga-ken Medical Centre Koseikan, Saga-shi, ,JP, (4) Department of Health Sciences, Faculty of Medical Sciences, Kyushu University, Fukuoka-shi, ,JP, (5) Department of Radiology, Saga-ken Medical Centre Koseikan, Saga-shi, ,JP

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  N Tsuda

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose:
To investigate the image quality of the half-reconstruction computed tomography (CT) images with a differently positioned X-ray tube and detector of projection dataset using filtered back projection (FBP) and model-based iterative reconstruction (MBIR) methods.

Methods:
All CT images (Aquilion One, Canon Medical Systems) were acquired with scanning conditions of 120 kV, 1.0 sec/rotation, and non-helical scanning. Half- and full-reconstruction algorithms for the FBP and the MBIR methods were employed, respectively. The resolution property was evaluated by a two-dimensional (multi-directional) modulation transfer function (2D-MTF) at a 100-mm off-center position using a wire method. The noise property was evaluated by measurements of the noise power spectrum (NPS) at a 100-mm off-center area (50×50 mm²) under two different exposure levels (50 and 250 mAs). The MTFs and NPSs of half-reconstruction CT image were measured with various X-ray tube and detector positions of the projection dataset.

Results:
The MTFs of the half- and full-reconstruction algorithms with the MBIR method were higher than those of the FBP method. The MTF of the tangential direction in the X-ray tube side was higher than that in the detector side for both methods. The effect of the measurement direction of the MBIR method on the change of 2D-MTF was smaller than that of the FBP method for both the half- and full-reconstruction algorithms. The NPSs of the half-reconstruction measured at the X-ray tube side were higher than those measured at the detector side in high spatial frequencies for both the FBP and MBIR methods at each exposure level.

Conclusion:
The effect of the measurement area on the image quality evaluation was smaller in the MBIR method than in the FBP method. The half-reconstruction algorithm indicated higher resolution and more noise at the X-ray tube side and lower resolution and lesser noise at the detector side, respectively.

Keywords

Noise Power Spectrum, MTF, Image Analysis

Taxonomy

IM- CT: Quality control

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