Korean J Radiol.  2009 Oct;10(5):490-495. 10.3348/kjr.2009.10.5.490.

The Relationship between Subjective and Objective Parameters in CT Phantom Image Evaluation

• Park HJ
• Jung SE
• Lee YJ
• Cho WI
• Do KH
• Kim SH
• Kim KH

• KMID: 1093964
• DOI: http://doi.org/10.3348/kjr.2009.10.5.490

Abstract

OBJECTIVE
To evaluate whether there is a relationship between subjective parameters determined by a reviewer (spatial resolution, low contrast resolution, and artifacts) and objective parameters (the CT number of water, noise, and image uniformity) in CT phantom image evaluations. MATERIALS AND METHODS: We reviewed the CT results of phantom image evaluations conducted by Korean Institute for Accreditation of Medical Image (KIAMI) from May 2007 to June 2007. We compared the objective parameters against the pass or fail groups for the subjective parameters. We also evaluated whether there is a relationship between the artifact types and the other subjective parameters. RESULTS: The mean noise value was significantly higher in the fail groups for the subjective parameters compared to the pass groups (p = 0.006). Specifically, noise and low contrast resolution were found to have a statistically significant positive correlation (r = 0.183, p < 0.001). In the fail group for low contrast resolution, the failure due to artifacts was significantly higher than the pass group (p < 0.001). In contrast, no statistically significant differences were found for the mean CT number of water, noise, or image uniformity based on the types of artifacts. CONCLUSION: Subjective CT image parameters evaluated by a reviewer correlate with objectively measured parameters, especially noise. Therefore, a stricter noise standard might be able to improve the subjective parameters results, such as low contrast resolution.

Keyword

Computed tomography (CT), image quality; Phantoms

MeSH Terms

Artifacts
Korea
*Phantoms, Imaging
*Tomography, X-Ray Computed

Figure

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  Fig. 1 AAPM CT performance phantom model 76-410. This photograph includes each phantom for evaluation of parameters and scanned images.A. Phantom for evaluation of low contrast resolutionB. Phantom for evaluation of spatial resoluationC. Phantom for evaluation of slice thicknessD. Phantom for evaluation of CT number of water, noise, and image uniformity

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  Fig. 2 Correlation between noise level and low contrast resolution. Correlation between noise and low contrast resolution showed statistically significant positive correlation (r = 0.183, p < 0.001, r = correlation coefficient).

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