Imaging characterization of a multi-energy CT with quasi-monochromatic X-ray source

Abstract

A new multi-energy computer tomographic system for small animals was developed -and is now operative -with a quasi-monochromatic X-ray source. The system brings together two important features: the possibility to scan small animal with quasi-monochromatic X-ray The triple-energy radiography reconstructs the contrast medium mass-thicknessTriple-energy radiography is an important technique, able to provide accurate estimations about the investigated materials. These information are determined by acquiring images of the analyzed object at three different energies. The triple-energy algorithm is here applied to reconstruct quantitatively the distribution of a contrast medium (Iodine) into the sample. The technique permits to remove completely the background signal from the image: the result is an image that contains only the signal of the Iodine. With respect to dual-energy techniques, the use of three energies is essential when the background has an inhomogeneous composition. For instance, if the background contains soft tissue and a layer of bone, the dual energy reconstructed signal of Iodine is significantly distorted. Adding the third energy, the projection errors are drastically reduced, and the accuracy of the signal much increased also to low concentration of Iodine. Hence, the removal of the projection error enables the quantitative imaging of Iodine. If we take the logarithm of the transmitted to incident photon flux ratio T = ln(N/N0), for the same sample at three different energies, we can generalize the Beer-Lambert attenuation law to the case of multiple beams. We can write:Where T is the collection of the logarithmic attenuation of the three beams, L is the set of mass thicknesses (product of density and thickness) of the basis materials, and A is a 3×3 matrix whose elements are , namely the mass-attenuation coefficients of the i-th material at the k-th energy. Solving the system for L, we obtain the image of Iodine L contrast medium, and the background projection over the two basis materials L1 and L2:

Precise image-guided irradiation of small animals: a flexible non-profit platform

“…relative biological effectiveness) and optimization of small animal x-ray imaging (e.g. quasi-monochromatic x-rays, multi-energy CT) (Rossi et al 2011). For the specified irradiation beam quality (200 kV, 0.5 mm Cu added filtration, HVL: 1.25 mm Cu), the measured dose rate is >1 Gy min −1 .…”