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Magnetic particle imaging (MPI) is a novel biomedical imaging modality that allows non-invasive, tomographic, and quantitative tracking of the distribution of superparamagnetic iron oxide nanoparticle (SPION) tracers. While MPI possesses high sensitivity, detecting nanograms of iron, it does not provide anatomical information. Computed tomography (CT) is a widely used biomedical imaging modality that yields anatomical information at high resolution. A multimodal imaging agent combining the benefits of MPI and CT imaging would be of interest. Here we combine MPI-tailored SPIONs with CT-contrast hafnium oxide (hafnia) nanoparticles using flash nanoprecipitation to obtain dual-imaging MPI/CT agents. Co-encapsulation of iron oxide and hafnia in the composite nanoparticles was confirmed via transmission electron microscopy and elemental mapping. Equilibrium and dynamic magnetic characterization show a reduction in effective magnetic diameter and changes in dynamic magnetic susceptibility spectra at high oscillating field frequencies, suggesting magnetic interactions within the composite dual imaging tracers. The MPI performance of the dual imaging agent was evaluated and compared to the commercial tracer ferucarbotran. The dual-imaging agent has MPI sensitivity that is ∼3× better than this commercial tracer. However, worsening of MPI resolution was observed in the composite tracer when compared to individually coated SPIONs. This worsening resolution could result from magnetic dipolar interactions within the composite dual imaging tracer. The CT performance of the dual imaging agent was evaluated in a pre-clinical animal scanner and a clinical scanner, revealing better contrast compared to a commercial iodine-based contrast agent. We demonstrate that the dual imaging agent can be differentiated from the commercial iodine contrast agent using dual energy CT (DECT) imaging. Furthermore, the dual imaging agent displayed energy-dependent CT contrast arising from the combination of SPION and hafnia, making it potentially suitable for virtual monochromatic imaging of the contrast agent distribution using DECT.
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Structure and Tracer Kinetics-Driven Dynamic PET Reconstruction
Dynamic positron emission tomography (dPET) is a nuclear medical imaging technology that shows the changes in radioactivity over time. In this article, we propose a structure and tracer kinetics-constrained reconstruction framework for dPET imaging. Given the Poisson nature of PET imaging, we integrate the sparse penalty on a dual dictionary into a Poisson-likelihood estimator. Explicit anatomical constraints with a structural dictionary constructed from magnetic resonance or computed tomography images are employed to take advantage of the anatomical imaging modalities. In the kinetic dictionary, we treat tracer kinetics as random variables in a physiologically plausible range based on a compartmental model. We demonstrate the performance of our proposed framework with a direct simulated data set and real patient data.
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- Award ID(s):
- 1719932
- PAR ID:
- 10189000
- Date Published:
- Journal Name:
- IEEE transactions on radiation and plasma medical sciences
- Volume:
- 4
- Issue:
- 4
- ISSN:
- 2469-7303
- Page Range / eLocation ID:
- 400 - 409
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/TRPMS.2019.2947860
