X-ray fluorescence computed tomography (XFCT) imaging with a superfine pencil beam x-ray source

TL;DR

This paper introduces a benchtop XFCT imaging system using a superfine pencil beam x-ray source and spectrometers, demonstrating effective target localization and concentration proportionality through simulation and advanced reconstruction algorithms.

Contribution

It presents a novel XFCT system design with a superfine pencil beam source and compares reconstruction algorithms, advancing molecular imaging capabilities.

Findings

Achieved 83.68% DICE coefficient for target localization.

Reconstructed signal intensity correlates with target concentration.

MM algorithm outperforms ML-EM and FBP in simulations.

Abstract

X-ray fluorescence computed tomography (XFCT) is a molecular imaging technique of x-ray photons, which can be used to sense different elements or nanoparticle (NP) agents inside deep samples or tissues. XFCT has been an active research topic for many years. However, XFCT has not been a popular molecular imaging tool because it has limited molecular sensitivity and spatial resolution. To further investigate XFCT imaging, we present a benchtop XFCT imaging system, in in which a unique pencil beam x-ray source and a ring of x-ray spectrometers were simulated using GATE (Geant4 Application for Tomographic Emission) software. An accelerated majorization minimization (MM) algorithm with an L1 regularization scheme was used to reconstruct the XRF image of Molybdenum (Mo) NP targets from the numerical measurements of GATE simulations. With a low x-ray source output rate, good target localization was achieved with a DICE coefficient of 83.681%. The reconstructed signal intensity of the targets was found to be relatively proportional to the target concentrations if detector number and placement is optimized. The MM algorithm performance was compared with maximum likelihood expectation maximization (ML-EM) and filtered back projection (FBP) algorithms. In the future, the benchtop XFCT imaging system will be tested experimentally