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. 2012 Aug;85(1016):1112-7.
doi: 10.1259/bjr/99567374. Epub 2012 Jan 3.

Investigating the relationship between virtual cystoscopy image quality and CT slice thickness

S Lalondrelle  1 , S A Sohaib, I A Castellano, D Mears, R Huddart, V Khoo
Affiliations

Investigating the relationship between virtual cystoscopy image quality and CT slice thickness

S Lalondrelle et al. Br J Radiol. 2012 Aug.

Abstract

Objective: To investigate the effect of reconstruction slice thickness on image quality at CT virtual cystoscopy (VC).

Methods: Pelvic CT examinations in bladder cancer patients were reconstructed at different slice thicknesses (0.6-5 mm) and intervals, and resulting VC images assessed. Quality indicators were ridging, holes, floaters and dimpling artefacts, tumour definition, and an overall score, ranked 1 (best) to 7 (worst). CT number and standard deviation (SD) for bladder contents and bladder wall were recorded. The mean SD was used as a measure of noise, and the contrast-to-noise ratio (CNR) was calculated as the CT number difference between them divided by the average image noise. The mean CNR across the three levels was used for analysis. Each qualitative image quality measure was compared with CT number, noise and CNR measurements.

Results: Dimpling artefacts increased with thinner slice reconstruction and correlated with increased noise, often resulting in poor tumour definition. The best overall image quality score was seen for VC images reconstructed at 1.2 mm slice thickness, probably because of the competing effects of spatial resolution and CNR.

Conclusion: A slice thickness reconstruction <1.2 mm does not provide for better image quality at VC owing to the presence of increased noise.

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Figures

Figure 1
Figure 1
Virtual cystoscopy artefacts and parameters assessed: (a) ridging, (b) dimpling, (c) holes and floaters, and (d) tumour definition.
Figure 2
Figure 2
Assessment of CT quantitative parameters, CT number and standard deviation recorded for contents (1) and bladder wall (2) at three levels through the bladder [region of interest (ROI) 1, ROI 2, ROI 3].
Figure 3
Figure 3
Effect of slice thickness on image quality variables.
Figure 4
Figure 4
Dimpling artefact on thinner slices results in loss of tumour definition.
Figure 5
Figure 5
Slice thickness and overall score (a minimum value is seen for 1.2 mm slice thickness, indicating the optimum value).
Figure 6
Figure 6
The relationship of image quality and noise: (a) noise increases with reducing slice thickness; (b) dimple score increases (worsens) as noise increases.
See this image and copyright information in PMC

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