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Sampling density for the quantitative evaluation of air trapping

Pediatric Radiology Aims and scope Submit manuscript

Abstract

Background

Concerns have been expressed recently about the radiation burden on patient populations, especially children, undergoing serial radiological testing. To reduce the dose one can change the CT acquisition settings or decrease the sampling density.

Objective

In this study we determined the minimum desirable sampling density to ascertain the degree of air trapping in children with cystic fibrosis.

Materials and methods

Ten children with cystic fibrosis in stable condition underwent a volumetric spiral CT scan. The degree of air trapping was determined by an automated algorithm for all slices in the volume, and then for 1/2, 1/4, to 1/128 of all slices, or a sampling density ranging from 100% to 1% of the total volume. The variation around the true value derived from 100% sampling was determined for all other sampling densities.

Results

The precision of the measurement remained stable down to a 10% sampling density, but decreased markedly below 3.4%.

Conclusion

For a disease marker with the regional variability of air trapping in cystic fibrosis, regardless of observer variability, a sampling density below 10% and even more so, below 3.4%, apparently decreases the precision of the evaluation.

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Correspondence to Michael L. Goris.

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Goris, M.L., Robinson, T.E. Sampling density for the quantitative evaluation of air trapping. Pediatr Radiol 39, 221–225 (2009). https://doi.org/10.1007/s00247-008-1076-6

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  • DOI: https://doi.org/10.1007/s00247-008-1076-6

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