Article

X-space MPI: magnetic nanoparticles for safe medical imaging.

Department of Bioengineering, University of California Berkeley, Berkeley, CA 94720-1762, USA.
Advanced Materials (Impact Factor: 15.41). 07/2012; 24(28):3870-7. DOI: 10.1002/adma.201200221
Source: PubMed

ABSTRACT One quarter of all iodinated contrast X-ray clinical imaging studies are now performed on Chronic Kidney Disease (CKD) patients. Unfortunately, the iodine contrast agent used in X-ray is often toxic to CKD patients' weak kidneys, leading to significant morbidity and mortality. Hence, we are pioneering a new medical imaging method, called Magnetic Particle Imaging (MPI), to replace X-ray and CT iodinated angiography, especially for CKD patients. MPI uses magnetic nanoparticle contrast agents that are much safer than iodine for CKD patients. MPI already offers superb contrast and extraordinary sensitivity. The iron oxide nanoparticle tracers required for MPI are also used in MRI, and some are already approved for human use, but the contrast agents are far more effective at illuminating blood vessels when used in the MPI modality. We have recently developed a systems theoretic framework for MPI called x-space MPI, which has already dramatically improved the speed and robustness of MPI image reconstruction. X-space MPI has allowed us to optimize the hardware for fi ve MPI scanners. Moreover, x-space MPI provides a powerful framework for optimizing the size and magnetic properties of the iron oxide nanoparticle tracers used in MPI. Currently MPI nanoparticles have diameters in the 10-20 nanometer range, enabling millimeter-scale resolution in small animals. X-space MPI theory predicts that larger nanoparticles could enable up to 250 micrometer resolution imaging, which would represent a major breakthrough in safe imaging for CKD patients.

0 Bookmarks
 · 
114 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Magnetic Particle Imaging (MPI) shows promise for medical imaging, particularly in angiography of patients with chronic kidney disease. As the first biomedical imaging technique that truly depends on nanoscale materials properties, MPI requires highly optimized magnetic nanoparticle tracers to generate quality images. Until now, researchers have relied on tracers optimized for MRI T2*-weighted imaging that are suboptimal for MPI. Here, we describe new tracers tailored to MPI's unique physics, synthesized using an organic-phase process and functionalized to ensure biocompatibility and adequate in vivo circulation time. Tailored tracers showed up to 3x greater SNR and better spatial resolution than existing commercial tracers in MPI images of phantoms.
    IEEE Transactions on Medical Imaging 11/2014; DOI:10.1109/TMI.2014.2375065 · 3.80 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A synthetic process for constructing an organo-metal nanohybrid is described. This process uses polyaniline as a ligand in order to fabricate magnetic nanoparticles. This nanohybrid shows imaging potential uses as a magnetic resonance imaging contrast agent and a redox-sensing probe simultaneously both in vitro and in vivo.
    Nanoscale 11/2014; 7(5). DOI:10.1039/C4NR06340F · 6.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A novel technique is presented for obtaining a single in-vivo image containing both functional and anatomical information in a small animal model such as a mouse. This technique, which incorporates appropriate image neutron-scatter rejection and uses a neutron opaque contrast agent, is based on neutron radiographic technology and was demonstrated through a series of Monte Carlo simulations. With respect to functional imaging, this technique can be useful in biomedical and biological research because it could achieve a spatial resolution orders of magnitude better than what presently can be achieved with current functional imaging technologies such as nuclear medicine (PET, SPECT) and fMRI. For these studies, Monte Carlo simulations were performed with thermal (0.025 eV) neutrons in a 3 cm thick phantom using the MCNP5 simulations software. The goals of these studies were to determine: 1) the extent that scattered neutrons degrade image contrast; 2) the contrasts of various normal and diseased tissues under conditions of complete scatter rejection; 3) the concentrations of Boron-10 and Gadolinium-157 required for contrast differentiation in functional imaging; and 4) the efficacy of collimation for neutron scatter image rejection. Results demonstrate that with proper neutron-scatter rejection, a neutron fluence of $2 times {10^7}~hbox{n/cm}^{2}$ will provide a signal to noise ratio of at least one ( ${rm S}/{rm N} geq 1$ ) when attempting to image various $300~mu hbox{m}$ thick tissues placed in a 3 cm thick phantom. Similarly, a neutron fluence of only $1 times {10^7}~hbox{n/cm}^{2}$ is required to differentiate a <formula formulatype="inline"- $300~mu hbox{m}$ thick diseased tissue relative to its normal tissue counterpart. The utility of a B-10 contrast agent was demonstrated at a concentration of $50~muhbox{g/g}$ to achieve ${rm S}/{rm N} geq 1$ in 0.3 mm thick tissues while Gd-157 requires only slightly more than $10~muhbox{g/g}$ to achieve the same level of differentiation. Lastly, neutron collimator with an L/D ratio from 50 to 200 were calculated to provide appropriate scatter rejection for thick tissue biological imaging with neutrons.
    IEEE Transactions on Nuclear Science 10/2014; 61(5-5):2480-2488. DOI:10.1109/TNS.2014.2334593 · 1.46 Impact Factor