  CT and MRI are the two most widely used imaging modalities in healthcare,
each with its own merits and drawbacks. Combining these techniques in one
machine could provide unprecedented resolution and sensitivity in a single
scan, and serve as an ideal platform to explore physical coupling of x-ray
excitation and magnetic resonance. Molecular probes such as functionalized
nanophosphors present an opportunity to demonstrate a synergy between these
modalities. However, a simultaneous CT-MRI scanner does not exist at this
moment. As a pilot study, here we propose a mechanism in which water solutions
containing LiGa5O8:Cr3+ nanophosphors can be excited with x-rays to store
energy, and these excited particles may subsequently influence the T2
relaxation times of the solutions so that a difference in T2 can be measured by
MRI before and after x-ray excitation. The trends seen in our study suggest
that a measurable effect may exist from x-ray excitation of the nanophosphors.
However, there are several experimental conditions that hinder the clarity of
the results to be statistically significant up to a commonly accepted level
(p=0.05), including insoluble nanoparticles and inter-scan variability.
Nevertheless, the initial results from our experiments seem a consistent and
inspiring story that x-rays modify MRI T2 values around nanophosphors. Upon
availability of soluble nanophosphors, we will repeat our experiments to
confirm these observations.
