Jessica Lee Nute MS, Presenter: Nothing to Disclose

Lucia Le Roux PhD, Abstract Co-Author: Nothing to Disclose

Adam Grant Chandler PhD, Abstract Co-Author: Employee, General Electric Company

Dawid Schellingerhout MD, Abstract Co-Author: Nothing to Disclose

Dianna D. Cody PhD, Abstract Co-Author: Nothing to Disclose

Calcific and hemorrhagic foci of susceptibility are frequently encountered in the brains of patients undergoing routine brain MR studies and are difficult to distinguish using MR alone. Single-energy CT can be used to identify lesions with attenuation over 100 HU as calcific however those lesions with lower attenuation cannot be reliably identified. While calcific lesions are unlikely to cause harm, hemorrhagic lesions carry a risk of subsequent intracranial bleeding and contraindicate the use of medications that can reduce clotting. A methodology was developed using dual-energy Gemstone Spectral Imaging-CT (GSI-CT) to take advantage of the unique attenuation properties of calcium and iron to distinguish between these two etiologies.

Ferric oxide and hydroxyapatite were used to model hemorrhage and calcification respectively. A uniform distribution of these compounds was suspended in 1% agarose gels to model elemental concentrations of iron and calcium over a range of 0.005M to 0.25M. The gels were imaged in an anthropomorphic head phantom with a single-energy routine brain protocol. These scans were utilized to create HU matched gels of calcium and iron from 0 to 100HU which were verified using the single-energy routine brain protocol. The HU matched gels were imaged with a dual-energy protocol which matched the dose of the single-energy protocol to within 2 mGy and had similar imaging parameters to the single-energy protocol. Material decomposition was used to create water and calcium density images from the dual-energy data. Water/calcium scatterplots were created from measurements on the material density images. For each HU matched pair, the separation between the mean values along each axis was measured. The uncertainty in the separation was calculated as the quadrature sum of the standard deviations along both the water and calcium axes

Matched HU pairs yielded separation greater than the uncertainty for 50HU and above along the water axis and for 30HU and above along the calcium axis of the material decomposition scatterplot.

HU matched iron and calcium gels of 30HU and above could be distinguished using dual-energy GSI-CT.

The ability to distinguish between intracranial calcifications and hemorrhages using dual-energy GSI-CT will help advise on the correct prescription of anti-coagulant medications.

Nute, J, Le Roux, L, Chandler, A, Schellingerhout, D, Cody, D, Characterization of Brain Foci of Susceptibility into Hemorrhagic or Calcific Etiologies Using Gemstone Spectral Imaging-CT: Preliminary Work in a Phantom System.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12026972.html