Dual Layer CT
Dual-energy CT enables improvement of material and possibly tissue separation when compared to regular CT. Philips Healthcare has been successfully operating a dual-layer detector system in a modified Brilliance 64 CT scanner installed since 2005 in Hadassah University Medical Center, Israel. The dual-layer detector acquires single x-ray source CT data using two scintillation layers on top of each other with which two energy datasets are acquired simultaneously. The results of the two reconstructions are mapped into a plane created from the Hounsfield units (HU) of the upper-layer image versus the HU of the lower-layer image. We find that different materials end up in different definable regions in the HU-plane, so material separation can be performed. Application of a special correction on the reconstructed images achieves stability on the HU-plane despite beam-hardening effects on this image-based dual energy CT. We describe the material separation capabilities and algorithms with such a configuration and conclude that the combination of the dual-layer CT with the classification analysis in the HU-plane is a practical and robust method that may improve clinical applications, in particular those involving Iodine-Calcium.
KeywordsMaterial Separation Vectorial Separation Identical Tube Spectral Compute Tomography Voxel Classification
I would like to thank my colleagues from Philips HealthCare: Raz Carmi from the Global Research and Advanced Development group, Galit Kafri from the Clinical Solutions group, Philippe Coulon and Leon de Vries from the Clinical Science and Applications group, for taking the time to assess this manuscript. Their advice for some final corrections were greatly appreciated.
Research studies with the dual-layer detector have been made possible under guidance of a clinical team led by Prof. Jacob Sosna, Director of CT and Director of Research and Imaging Laboratories at HUMC. All phantom and clinical images presented in this chapter are courtesy of HUMC.
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