Harald Brodoefel MD, Presenter: Nothing to Disclose

Andreas Korn, Abstract Co-Author: Nothing to Disclose

Michael Christian Fenchel MD, Abstract Co-Author: Nothing to Disclose

Soeren Danz, Abstract Co-Author: Nothing to Disclose

Claus Detlef Claussen MD, Abstract Co-Author: Nothing to Disclose

Martin Heuschmid MD, Abstract Co-Author: Nothing to Disclose

Ulrike Ernemann, Abstract Co-Author: Nothing to Disclose

Iterative reconstruction (IR) has recently demonstrated its capacity to reduce noise and permit significant dose reduction in abdominal and thoracic CT applications. The purpose of our study was to assess the potential benefit of IR in Head-CT by comparing objective and subjective image quality to standard filtered back projection (FBP) at various dose levels.

Ninety consecutive patients were randomly assigned to undergo both non-enhanced and contrast enhanced Head-CT at standard dose (320 mAs) or 15% (275 mAs) and 30% (225 mAs) dose reduction. All acquisitions were reconstructed with IR and FBP and images assessed in terms of quantitative and qualitative image quality (IQ).

Compared with FBP, IR resulted in lower image noise (p≤0.02), higher contrast-to-noise ratio (CNR; p≤0.03) and improved subjective image quality (p≤0.002) at all dose levels. Whilst degradation of objective and subjective IQ at 15% dose reduction was fully compensated by IR (CNR 1.98±0.4 at 320 mAs, FBP v. 2.05±0.4 at 275 mAs, IR; IQ 1.8 v. 1.7), IQ was considerably poorer at 70% standard dose despite using the iterative approach (CNR 1.98±0.3 at 320 mAs, FBP v. 1.85±0.4 at 225 mAS, IR, p=0.18; IQ 1.8 versus 2.2, p=0.03). Linear regression analysis of CNR against tube current suggests that standard CNR may be obtained till about 20.4% dose reduction when IR is used.

Compared to conventional FBP, IR of Head-CT is associated with significant improvement of objective and subjective IQ and may allow dose reductions in the range of 20% without compromising standard image quality.

Our data support the use of IR in Head-CT as a valuable tool for significant dose reduction.

Brodoefel, H, Korn, A, Fenchel, M, Danz, S, Claussen, C, Heuschmid, M, Ernemann, U, Iterative Reconstruction in Head-CT: Image Quality of Routine and Low Dose Protocols in Comparison to Standard Filtered Back Projection.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11004109.html