<title>Image Noise And Smoothing In Computed Tomography (CT) Scanners</title>

Over the last decade, cardiac computed tomography (CT) technology has experienced revolutionary changes and gained broad clinical acceptance in the work-up of patients suffering from coronary artery disease (CAD). Since cardiac multidetector-row CT (MDCT) was introduced in 1998, acquisition time, number of detector rows and spatial and temporal resolution have improved tremendously. Current developments in cardiac CT are focusing on low-dose cardiac scanning at ultra-high temporal resolution. Technically, there are two major approaches to achieving these goals: rapid data acquisition using dual-source CT scanners with high temporal resolution or volumetric data acquisition with 256/320-slice CT scanners. While each approach has specific advantages and disadvantages, both technologies foster the extension of cardiac MDCT beyond morphological imaging towards the functional assessment of CAD. This article examines current trends in the development of cardiac MDCT.

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Liver density in routine and low-dose computed tomography: the effect of image noise on measurement accuracy

Medical Visualization ◽

10.24835/1607-0763-2020-1-39-47 ◽

2020 ◽

Vol 24 (1) ◽

pp. 39-47

Author(s):

A. P. Gonchar ◽

V. A. Gombolevskij ◽

A. B. Elizarov ◽

N. S. Kulberg ◽

V. G. Klyashtorny ◽

...

Keyword(s):

Computed Tomography ◽

Measurement Accuracy ◽

Low Dose ◽

Image Noise ◽

Low Dose Computed Tomography

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Image Quality Assessment of Low-Dose CT using Hybrid Iterative Reconstruction

Journal of Imaging Science and Technology ◽

10.2352/j.imagingsci.technol.2022.66.1.010504 ◽

2021 ◽

Author(s):

Qiao Zhang ◽

Jinhua Sheng ◽

Bin Chen

Keyword(s):

Computed Tomography ◽

Noise Reduction ◽

Iterative Reconstruction ◽

Low Dose ◽

Low Frequency ◽

Image Noise ◽

Observer Performance ◽

Human Observer ◽

X Ray ◽

Hybrid Iterative Reconstruction

Background: X-ray computed tomography is the first imaging technology that supports accurate nondestructive interior image reconstruction of an object from sufficient projection data. Low-dose computed tomography (LDCT) has been considered to relieve the harm to patients caused by X-ray radiation. However, LDCT images can be degraded by quantum noise and streak artifacts. Methods: The objective of the authors’ study is to evaluate the optimal level of the hybrid iterative reconstruction (HIR) that generates images with the best diagnostic quality on different dose and noise levels. HIR with optimizations is proposed to reduce image noise and provide better performance at a low dose. The Catphan R 504 phantom is employed to assess various image qualities (IQ). Results: For any given scanning protocols, there is linear noise reduction and linear increase of contrast-to- noise ratio (CNR) using optimal HIR. The evidence from various module tests demonstrates that the shape of the noise power spectrum is continuously shifted to low frequency with increasing HIR levels compared with that of filtered-back-projection (FBP). This may describe the difference between the human observer performance and features of the ideal low-contrast objects. Conclusion: Optimal HIR is clearly demonstrated to be a superior method for reducing image noise and improving CNR compared to FBP. Optimal HIR also inhibits texture change or spectrum shift compared with the pure IR method. Even though there are continuous noise reduction and CNR increase with HIR at increasing levels, the human observer performance does not seem to improve simultaneously due to coarser noise (low-frequency noise). HIR level 3 to 5 is optimal for their study. It is possible for the optimal HIR to offer equivalent diagnostic IQ at a lower dose compared with FBP at a routine dose.

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