Korean J Radiol.  2002 Mar;3(1):49-56. 10.3348/kjr.2002.3.1.49.

The Quality of Reconstructed 3D Images in Multidetector-Row Helical CT: Experimental Study Involving Scan Parameters

• Shin JH
• Lee HK
• Choi CG
• Suh DC
• Lim TH
• Kang W

• KMID: 1758447
• DOI: http://doi.org/10.3348/kjr.2002.3.1.49

Abstract

OBJECTIVE
To determine which multidetector-row helical CT scanning technique provides the best-quality reconstructed 3D images, and to assess differences in image quality according to the levels of the scanning parameters used.
MATERIALS AND METHODS
Four objects with different surfaces and contours were scanned using multidetector-row helical CT at three detector-row collimations (1.25, 2.50, 5.00 mm), two pitches (3.0, 6.0), and three different degrees of overlap between the reconstructed slices (0%, 25%, 50%). Reconstructed 3D images of the resulting 72 sets of data were produced using volumetric rendering. The 72 images were graded on a scale from 1 (worst) to 5 (best) for each of four rating criteria, giving a mean score for each criterion and an overall mean score. Statistical analysis was used to assess differences in image quality according to scanning parameter levels.
RESULTS
The mean score for each rating criterion, and the overall mean score, varied significantly according to the scanning parameter levels used. With regard to detector-row collimation and pitch, all levels of scanning parameters gave rise to significant differences, while in the degree of overlap of reconstructed slices, there were significant differences between overlap of 0% and of 50% in all levels of scanning parameters, and between overlap of 25% and of 50% in overall accuracy and overall mean score. Among the 18 scanning sequences, the highest score (4.94) was achieved with 1.25 mm detector-row collimation, 3.0 pitch, and 50% overlap between reconstructed slices.
CONCLUSION
Comparison of the quality of reconstructed 3D images obtained using multidetector-row helical CT and various scanning techniques indicated that the 1.25 mm, 3.0, 50% scanning sequence was best. Quality improved as detector-row collimation decreased; as pitch was reduced from 6.0 to 3.0; and as overlap between reconstructed slices increased.

Keyword

Computed tomography (CT), helical; Computed tomography (CT), three-dimensional; Computed tomography (CT), experimental study

MeSH Terms

Human
*Image Processing, Computer-Assisted
*Imaging, Three-Dimensional
Support, Non-U.S. Gov't
*Tomography, X-Ray Computed

Figure

• 

  Fig. 1 The four objects used in this study. A. Mandible B. Calvarium C. Cup D. Billiard ball

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  Fig. 2 Mean score and 95% confidence intervals of scanning sequences for definition.

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  Fig. 3 Mean score and 95% confidence intervals of scanning sequences for smoothness.

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  Fig. 4 Mean score and 95% confidence intervals of scanning sequences for overall accuracy.

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  Fig. 5 Mean score and 95% confidence intervals of scanning sequences for overall mean score.

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  Fig. 6 Image quality of the mandible according to the level of detector-row collimation. Image quality improved as detector-row collimation decreased. A. 1.25 mm, 3.0, 50% B. 2.50 mm, 3.0, 50% C. 5.00 mm, 3.0, 50%

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  Fig. 7 Image quality of the cup according to the level of pitch. Image quality, i.e. definition of the outer margin or smoothness of the curved area, is better at a pitch of 3.0 than at one of 6.0. A. 2.50 mm, 3.0, 50% B. 2.50 mm, 6.0, 50%

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  Fig. 8 Image quality of the mandible according to the degree of overlap between reconstructed slices. Image quality improved as overlap increased. A. 2.50 mm, 3.0, 0% B. 2.50 mm, 3.0, 25% C. 2.50 mm, 3.0, 50%

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