J Korean Soc Radiol.  2011 Nov;65(5):479-485.

The Image Quality of a Digital Chest X-Ray Radiography System: Comparison of Quantitative Image Quality Analysis and Radiologists' Visual Scoring

• Jeon H
• Nam JH
• Chung MJ
• Park D
• Kim WT
• Kim YH
• Ki YK
• Kim DH
• Lee JH
• Kim DW

Abstract

PURPOSE
To evaluate the performance of imaging devices, which should be periodically monitored to maintain high quality images to the radiologists. Additionally, this evaluation may prevent patients from radiation over-exposure. The most suitable engineering standard for imaging performance evaluation of digital X-ray thoracic imagers was determined.
MATERIALS AND METHODS
IEC 62220-1 standards were used to evaluate the performance of the imagers. In succession, the visibilities of overall image, pneumothorax, and humerus head in anthropomorphic thoracic phantom images were used to evaluate the image qualities by radiologists.
RESULTS
The rank correlation coefficient (p) of visual scoring by radiologists with system spatial resolution is not meaningful (p-value, p = 0.295), but is significant with image noise (p-value, p = -0.9267). Finally, the noise equivalent quanta (NEQ) presents a high rank correlation for visual scoring of radiologists (p-value, p = 0.9320).
CONCLUSION
Image quality evaluation of radiologists were mainly affected by imaging noise. Hence, the engineered standard for evaluating image noise is the most important index to effectively monitor the performance of X-ray imagers. Additionally, the NEQ can be used to evaluate the performance of radiographic systems, because it theoretically corresponds to the synthetic image quality of systems.

MeSH Terms

Head
Humans
Humerus
Noise
Organothiophosphorus Compounds
Pneumothorax
Thorax
Organothiophosphorus Compounds

Figure

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  Fig. 1 An example of acquired images for MTF and NNPS measurements. Note.-MTF = modulation transfer function, NNPS = normalized noise power spectrum

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  Fig. 2 (A) An anthropomorphic phantom and (B) its radiographic image.

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  Fig. 3 Relationships between exposures and (A) iMTFs, (B) iNNPSs and (C) iNEQs. Note.-iMTF = integrated modulation transfer function, iNEQ = integrated noise equivalent quanta, iNNPS = integrated normalized noise power spectrum

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  Fig. 4 Relationships between mean scores by radiologists and (A) exposures, (B) iMTFs, (C) iNNPSs, and (D) iNEQs. Note.-iMTF = integrated modulation transfer function, iNEQ = integrated noise equivalent quanta, iNNPS = integrated normalized noise power spectrum

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