  In this paper, we propose an x-ray fluorescence imaging system for elemental
analysis. The key idea is what we call "x-ray fluorescence sectioning".
Specifically, a slit collimator in front of an x-ray tube is used to shape
x-rays into a fan-beam to illuminate a planar section of an object. Then,
relevant elements such as gold nanoparticles on the fan-beam plane are excited
to generate x-ray fluorescence signals. One or more 2D spectral detectors are
placed to face the fan-beam plane and directly measure x-ray fluorescence data.
Detector elements are so collimated that each element only sees a unique area
element on the fan-beam plane and records the x-ray fluorescence signal
accordingly. The measured 2D x-ray fluorescence data can be refined in
reference to the attenuation characteristics of the object and the divergence
of the beam for accurate elemental mapping. This x-ray fluorescence sectioning
system promises fast fluorescence tomographic imaging without a complex inverse
procedure. The design can be adapted in various ways, such as with the use of a
larger detector size to improve the signal to noise ratio. In this case, the
detector(s) can be shifted multiple times for image deblurring.
