John Paul Ronaldson, Presenter: Grant, Mars Bioimaging Ltd

Rafidah Zainon, Abstract Co-Author: Nothing to Disclose

Anas Sedayo, Abstract Co-Author: Nothing to Disclose

Nicola Scott BSc, PhD, Abstract Co-Author: Nothing to Disclose

Anthony P.H. Butler MBChB, Abstract Co-Author: Director, MARS Bioimaging Ltd

Phil Butler BSc, PhD, Abstract Co-Author: Director, MARS Bioimaging Ltd

Nigel Graeme Anderson MBBCh, FRANZCR, Abstract Co-Author: Nothing to Disclose

To determine if spectral CT can quantify fat, calcium and iron in soft tissues within small animal models and surgical specimens of diseases such as fatty-liver (metabolic syndrome) and unstable atherosclerosis.

The work was planned in 4 phases. 1. A standalone x-ray tube and Medipix3 photon counting x-ray detector with silicon sensor layer were used to investigate the potential to distinguish and quantify fat composition from 0-40% by weight by analysing x-ray transmission spectra. A linear algebraic model of the transmission spectra was used to assess the feasibility of the spectroscopic method for quantifying the composition of soft tissues using CT. 2. The spectroscopic method was applied to tomographic data acquired using a micro-CT system incorporating a Medipix3 detector and micro-focus x-ray tube operating at 50 kVp. A 10 mm diameter perspex phantom containing discrete solutions of sunflower oil (fat surrogate), ferric nitrate and calcium chloride was imaged. We used the spectroscopic characteristics of the CT number to establish a linear basis for quantifying the soft tissue components. 3. The measurement performance was evaluated using mouse and atheroma equivalent phantoms designed to simulate beam-hardening artefacts from low and high contrast materials. 4. The quantification method was validated in biological specimens and a mouse model.

Phase 1. Projection measurements of the x-ray transmission spectra provided a linear measure of the fat content of the surrogates over the range 0-40% by weight with standard uncertainties better than 10% by weight. Phase 2. Graphical analysis of spectral CT measurements of a phantom containing soft-tissue surrogates confirmed the ability to distinguish these materials by the spectroscopic characteristics of their CT number. Phase 3 and 4. Results not available at 31 March.

Spectral CT can quantify fat, water, and calcium composition in phantom equivalents of fatty-liver and atheroma.

Accurate quantification of liver fat, and lipid, iron and calcium in plaque to determine if it is stable or unstable, would allow treatments to be tested and monitored in vivo in animal models.

Ronaldson, J, Zainon, R, Sedayo, A, Scott, N, Butler, A, Butler, P, Anderson, N, Towards Quantifying the Composition of Soft-tissues by Spectral CT Imaging with Medipix3.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11008277.html