Dual Energy Computed Tomography

Abstract

Dual layer CT is a new medical imaging technique, working with two layers of standard scintillator detectors laying on top of each other. The two layers give separate measurements of X-rays with different energies. With these extra information mono-energetic images can be reconstructed. These images are reconstructed as if they were made with a monochromatic bundle. The aim of this research project is to prove if the images gained by this new technique are at least equally useful as the conventional CT images, with the same radiation dose for the patient. A conventional CT scan is made with an X-ray bundle with a certain effective energy. To compare the conventional images with the reconstructed monoE images, the right monoE setting needs to be determined for the effective energy used. This is done by phantom measurements. The phantom measurements are done in the conventional way and for different reconstructed monoE values. The minimum difference between the regular and the monoE image is determined. For a 120 kV scan the right monoE is 68 keV. Data from the brain and abdomen protocol from real patients is used to reconstruct the images. These scans are interpreted by a radiologist in training, who rate them at medical diagnosability. A one-proportion non inferiority test is done on the results. This shows that the brain and the abdomen both satisfy the requirements to be a good CT image. The images gained by the dual energy CT are equally useful to the image of the regular CT, for the same radiation dose for the patient.