TH-EF-BRA-05: Investigation of Full Dose Reduction Potential of ASiRâ„¢ for Head CT Protocols in a Predominantly Pediatric Population

Authors


Abstract

Purpose:

To ascertain and implement the maximum level of adaptive statistical iterative reconstruction (ASiR) that can be used to establish dose reduced pediatric head CT protocols.

Methods:

Noise power spectrum (NPS), modulation transfer function (MTF), and qualitative visual assessment were used as image quality metrics to calculate image quality based on filtered back projection (FBP) and ASiR reconstruction. The effect on image quality as a function of level of ASiR implementation and tube current reduction was analyzed by comparing image noise magnitude and frequency, and spatial resolution with similar measured image quality for FBP. Relative patient dose reduction was estimated using both CTDIvol and effective dose calculated using pediatric sized physical anthropomorphic phantoms. Dose reduced protocols were investigated for CT head examinations (i.e. brain, orbits, sinus, maxillary and temporal bones) by implementing ASiR and lowering CT tube current.

Results:

An analysis of the effects on noise texture from implementation of statistical iterative reconstruction determined that the level of ASiR that correlated closest with FBP for the GE soft reconstruction kernel (for both 100 and 120 kVp) was determined to be 30%, and for the GE standard reconstruction kernel at 100 kVp was 20% ASiR. However, implementation of 60% ASiR (GE soft reconstruction kernel) and 30% ASiR (GE standard reconstruction kernel) led to an average relative reduction in CTDIvol by 40% (range: 30%-47%) and effective dose by 36% (range: 12%-54%) while maintaining the same overall noise magnitude and improving the CNR of the image as compared to FBP. A coarser noise texture was visualized at 60% ASiR.

Conclusion:

The data in this study are provided to allow customized selection of ASiR implementation relating to acceptable tolerance for change in noise texture appearance in reconstructed images, and level of relative dose reduction for a pediatric population undergoing head CT examination.

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