Significant work has been done to develop nanoparticle contrast agents for computed tomography (CT), with a focus on identifying safer and more effective formulations. Contrast agents for spectral photon-counting computed tomography (SPCCT), a fast-growing imaging modality derived from conventional CT, have also recently gained considerable attention. In this study, we explored the synthesis of ultrasmall ytterbium nanoparticles (YbNP) and demonstrated that, potentially, they can be used as conventional CT and SPCCT contrast agents. These nanoparticles were tested in vitro for their cytotoxicity and contrast-generating properties with a variety of imaging systems. When scanned with conventional CT and SPCCT at clinically relevant energies, YbNP are significantly more attenuating than gold nanoparticles (AuNP), the contrast agents that have been most well studied. Furthermore, YbNP were studied for their potential application for labeling and monitoring hydrogels. The presence of the YbNP payload in hydrogels allowed for hydrogel localization and tracking in vivo. Additionally, the in vivo imaging results revealed that YbNP generate higher contrast when compared to AuNP used as a label. In summary, this is the first research study to examine ultrasmall YbNP as conventional CT and SPCCT contrast agents, as well as using them in a hydrogel system to make it radiopaque. These findings underscore YbNP’s utility as CT and SPCCT contrast agents, as well as their potential for tracking hydrogels in vivo.

Three children with drug-refractory epilepsy, normal magnetic resonance image (MRI), and a heterozygous SCN1A variant underwent 2-deoxy-2-[F]fluoro-d-glucose positron emission tomography (FDG-PET) scanning between age 6 months and 1 year and then at age 3 years 6 months to 5 years 5 months. Regional FDG uptake values were compared to those measured in age- and gender-matched pseudo-controls. At baseline, the brain glucose metabolic pattern in the SCN1A group was similar to that of the pseudo-controls. At follow-up, robust decreases of normalized FDG uptake was found in bilateral frontal, parietal and temporal cortex, with milder decreases in occipital cortex. Children with epilepsy and an SCN1A variant have a normal pattern of cerebral glucose metabolism at around 1 year of age but develop bilateral cortical glucose hypometabolism by age 4 years, with maximal decreases in frontal, parietal, and temporal cortex. This metabolic pattern may be characteristic of epilepsy associated with SCN1A variants and may serve as a biomarker to monitor disease progression and response to treatments.

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Purpose: To compare several methods for displaying DTI data in MRI for clinical use. Method and Materials: A diffusion tensor imaging (DTI) visualization tool was developed at our institution by graphically displaying the principal eigenvector as a headless arrow, using either regular or stereoscopic LCD monitors. This tool utilizes stereoscopic vision to represent diffusion tensor's spatio‐directional information, while allowing color, the traditional tool for displaying directional information, to be used for other diffusion characteristics, such as functional anisotropy (FA). In this tool, the principal eigenvector at each voxel, Vmax, is depicted as a headless arrow, while a color scale is used to encode the FA index. We compared: a) grayscale FA map (GSFM), b) coded orientation map (CCOM), c) Vmax maps using regular non‐stereoscopic display (VM), and d) Vmax maps using stereoscopic display (VMS). A survey of clinical utility was performed by eight board‐certified neuroradiologists, using a paired comparison questionnaire format with forced and graded choices. Five representative cases were selected based on the typical brain tumor patient population at our institution. Results: Vmax map was favored over traditional methods of display in most of the cases (80% vs. 10%, 10% no preference). However, when stereoscopic (VMS) and the non‐stereoscopic (VM) modes were compared, VMS was preferred in 45% of them while VM was 35% and 30% had no preference. The main reason given for the preference of the stereoscopic DTI visualization tool (VMS, VM) to the conventional DTI visualization methods (CCOM and GSFM) was better delineation of white matter tract and improved 3D anatomy effect. Conclusion: DTI data displayed by our Vmax based display methodology seems to be preferred over traditional display methods in tests of clinical utility.

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