title: Improved signal-to-noise ratio for non-perpendicular detection angles in x-ray fluorescence computed tomography (XFCT).
abstract: The standard imaging setup in x-ray fluorescence computed tomography detects the fluorescence emission at a right angle with respect to the axis of the excitation beam. In this paper we have studied how the detection angle affects the signal-to-noise ratio (S/N), which is a major factor influencing the low-contrast sensitivity of the imaging system. This is done for an imaging setup using a collimated detector and a pencil beam of excitation x-rays. An ideal detection process is simulated for a generalized imaging case with gold/platinum tracers and experimental measurements are performed using a diagnostic x-ray tube. For monochromatic excitation, the results indicate that order-of-magnitude improvements of the S/N can be achieved by optimizing the detection angle. The maximal S/N, when exciting with an energy just above the K-edge, is achieved for large detection angles, i.e. with the detector close to the source. The improvements also transfer to polychromatic excitation sources and the experimental results show up to four-fold improvements of the S/N when changing the detection angle from 90° to 150°. Also, the changes of the S/N behavior when switching the fluorescent tracer is briefly demonstrated. These results suggest that the choice of detection angle should be taken seriously in the design of future XFCT imaging systems.
authors.affiliation: Department of Physics, Section for Medical Imaging, Royal Institute of Technology, AlbaNova University Center, SE-106 91 Stockholm, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Sjölin
authors.forename: Mats
authors.initials: M
authors.lastname: Danielsson
mesh_terms: D006046:Gold / Q000737:chemistry; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019047:Phantoms, Imaging; D010984:Platinum / Q000737:chemistry; D011849:Radioactive Tracers; D059629:Signal-To-Noise Ratio; D013052:Spectrometry, X-Ray Emission / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D011849:Radioactive Tracers; D010984:Platinum; D006046:Gold