X-Ray Fluorescence Computed Tomography With Polycapillary Focusing

Liposomal iodine nanoparticles (LINPs) have a long half-life and provide an excellent intravascular contrast. The nanoparticles can be functionalized as molecular probes for biological targets to facilitate numerous preclinical studies for translation toward diagnosis and therapy of various human diseases. Iodine has a K-edge at 33 keV due to the photoelectric absorption of photons, which emit X-ray fluorescence at 28 keV with a fluorescence yield of 0.88. Detections of the characteristic X-rays can be used for the imaging of iodine concentration distribution in an object. In this paper, we propose an X-ray fluorescence computed tomography method for reconstruction of a LINPs distribution over a region of interest (ROI) in a small animal. X-rays are focused onto a submillimeter focal spot utilizing a polycapillary lens, generating a pair of X-ray cones in the animal. This focused beam irradiates LINPs, the most strongly at the focal spot. Then, the focal spot can be scanned over an ROI in the object to produce X-ray fluorescence signals. From measured fluorescence data, a reliable image reconstruction can be achieved with a high spatial resolution. Numerical simulation studies are performed to demonstrate the superior imaging performance of this methodology.