Purpose: Calcific and hemorrhagic foci of susceptibility are frequently encountered in routine brain MR studies and are difficult to distinguish. 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 identified1. While calcific lesions are unlikely to cause harm, hemorrhagic lesions carry a risk of subsequent intracranial bleeding. 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. Methods: 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 had similar dose and 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 and plotted against the HU. The uncertainty in the separation was calculated as the quadrature sum of the standard deviations along both the water and calcium axes. Results: Matched HU pairs yielded separation greater than the uncertainty for 40HU and above along both the calcium and water axes of the material decomposition scatterplot. Conclusions: HU matched iron and calcium gels of 40HU and above could be distinguished using dual‐energy GSI‐CT.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging