ABSTRACT
X-ray diagnostic imaging is a major worldwide activity. In the United States, approximately 250 million x-ray examinations are performed annually, and in Europe, a similar level of radiological activity is undertaken. The photons emitted by the x-ray tube are collimated by a beam-limiting device. X-ray luminescence computed tomography (XLCT) is proposed as a new hybrid molecular imaging modality based on the selective excitation and optical detection of x-ray-excitable phosphor nanoparticles. X-ray fluorescent measurements of biological samples yield quantitative information about the spatial distribution of multiple elements simultaneously with high sensitivity and low background. The hybrid system consists of an x-ray source, x-ray detector, and a charge-coupled device (CCD) camera. The development of deep-tissue x-ray luminescence imaging will require the incorporation of optical tomographic models. Optical imaging methods can be broadly divided into two categories: linear and nonlinear imaging—based on the dependence of the signals on the incident light intensity.
