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Assessing Lumen Narrowing of Pediatric Vascular Stents

December 18, 2009
Written by: , Filed in: Pediatric Radiology
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A recent study was conducted to evaluate the effect of varying tube voltages and currents in CT scanning on the assessment of stent lumen diameter and simulated stenosis with comparison to digital radiographic angiography using an in vitro model.

The study results have concluded that at a wide range of tube settings, CT is feasible to assess lumen narrowing of pediatric vascular stents.

Methodology
10 commercially available peripheral vascular stainless steel stents were studied as phantoms. Three of these tubes were filled with wax to simulate luminal narrowing ranging from mild to moderate stenoses.

The tubes were then filled with contrast material. The prepared tubes were placed between 2 sponges to simulate surrounding lung.

The phantoms were imaged in the helical mode in a 64-MDCT scanner with setting variations only in the dose and tube current parameters.

Altogether, the phantoms were each scanned 10 times with 10 varying tube settings. They were then imaged using angled biplane fluoroscopy as would be performed in conventional digital angiography.

Software was utilized for 3D image display and analysis. Using electronic calipers, 2 observers independently measured the cross-sectional strut diameters. The measurements of the 2 observers were averaged for statistical analysis.

In comparing the results of a wide range of stent sizes and tube settings, a percent agreement between MDCT results and digital angiography measurements was statistically determined.

Pediatric Diagnostic Imaging

The Society for Pediatric Radiology
Pediatric Diagnostic Imaging program features the advances and diversity of pediatric imaging by reviewing state-of-the-art clinical material and advanced cutting-edge research presentations. This program presents a group of international experts who discuss state-of-the art diagnostic imaging and the outlook for the future direction of the specialty.
Read more or order:  Pediatric Diagnostic Imaging

Results
Interobserver variability was not statistically significant. The diameters measured by MDCT and digital angiography showed a high statistical correlation with a linear relationship.

The inner luminal diameters measured by MDCT were consistently and significantly smaller than those measured on digital angiography.

There was improvement in agreement between the 2 modalities as the diameter increased.

When comparing the different tube settings, there was an improvement in agreement with an increase of tube current above 120 mA and tube voltage of 100 kVp with no further improvement above 160 mA.

Conclusions
At a wide range of tube settings, CT is feasible to assess lumen narrowing of pediatric vascular stents.

This study supports the ability of using MDCT to image intravascular stents in children because of consistency among a wide range of tube currents, a variable important to the pediatric imager who is keen on limiting radiation dose without compromising diagnostic accuracy.

Using digital angiography as the reference standard, accuracies approached 99%. Findings suggest that it may be possible to lower radiation exposure without loss of image quality.

Reviewer’s Comments
This article is novel in its approach to modeling in vitro comparison between a wide range of stent sizes. The authors suggest the data’s utility in pediatric imaging is due to the consistent accuracy of MDCT at various tube currents.

Considering how many other studies a typical child with congenital heart disease may undergo that would further contribute to ionizing radiation exposure, data produced by this study are essential to designing protocols for CT scans in children.

Author: Basil Hubbi, MD

Reference:

Eichhorn JG, Jourdan C, et al. CT of Pediatric Vascular Stents Used to Treat Congenital Heart Disease. AJR; 2008; 190 (May): 1241-1246

Pediatric Diagnostic Imaging

The Society for Pediatric Radiology
Pediatric Diagnostic Imaging program features the advances and diversity of pediatric imaging by reviewing state-of-the-art clinical material and advanced cutting-edge research presentations. This program presents a group of international experts who discuss state-of-the art diagnostic imaging and the outlook for the future direction of the specialty.
Read more or order:  Pediatric Diagnostic Imaging
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