Tsvi Katchalski PhD, Presenter: Employee, Koninklijke Philips Electronics NV

Yoad Yagil PhD, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Igor Uman, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Eyal Kohn, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Kevin M. Brown MS, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Richard Thompson, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Morton Thomas, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Rahul Patel, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Matthias Bertram, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Jens Wiegert PhD, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

As the need for quantitative CT in single and multi-energy applications increases, both hardware and algorithmic solutions are introduced to account for scatter artifacts. We investigated the effectiveness of a first principle scatter correction employing a Monte-Carlo based water sphere model also termed Clear Ray© at regions of thick bone structures such as the femur bone of the thigh.

Measurements of wide and narrow coverage scans were used to generate SPR (scatter to primary ratio) plots, sinogram analysis and reconstructed image differences which were compared to scatter model correction values.

Uniform scatter free soft-tissue regions in the presence of thick bone structures was observed. Experimentally measured scatter matched model generated scatter correction values very well. Observable image artifacts in soft-tissue are due to bone beam hardening, as they are equally evident in both wide and narrow coverage images. Small HU differences in cortical and trabecular bone and also at the soft-tissue/air interface were measured. The fact that these occur at interfaces indicates that are likely to be due to residual scatter originating from the “bow tie” filter. 

The scatter correction investigated has previously shown to give good IQ in routine abdomen clinical scans and improve renal cyst diagnosis and liver uniformity. In this study, we show that the scatter model gives very good correction in soft-tissue near thick bone structures. Additional improvement in current “bow tie” scatter correction is expected to achieve even higher accuracy in bone regions.  

Quantitative CT applications such as renal cyst diagnosis, Osteoporosis bone mapping or plaque/iodine separation require accurate CT values. Scatter correction is essential to avoid inaccuracies.

Katchalski, T, Yagil, Y, Uman, I, Kohn, E, Brown, K, Thompson, R, Thomas, M, Patel, R, Bertram, M, Wiegert, J, Experimental Effectiveness of First Principle Scatter Correction in Clinical MDCT.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11014715.html