Magnetic Particle Imaging for functional brain imaging; rodent and human-scale devices
ORAL · Invited
Abstract
Magnetic Particle Imaging (MPI) forms images of the cerebral blood pool by detecting the non-linear magnetization of injected superparamagnetic iron oxide nanoparticles (SPIONs). Its lack of biological background, fast imaging, and high sensitivity make it an attractive potential modality for human functional neuroimaging. In this talk, I review the MPI method and report the first use of MPI for imaging hemodynamic modulation of Cerebral Blood Volume (CBV) in a study of rats undergoing a hypercapnia CBV modulation paradigm and show that fMPI has up to 6-fold higher CNR than 9.4T BOLD fMRI in the same hypercapnic paradigm. We also report the first phantom and non-human primate images and sensitivity measures in an MPI scanner we constructed for human functional brain imaging. We detect changes in the local SPION concentration associated with the CBV modulation in the NHP brain during three 10-minute periods of alternating hypercapnia and normocapnia with a CNR of 5.7 in a 7mm x 7mm region in the brain.
Our human-capable MPI scanner uses a 1.13 T/m permanent magnet (PM) FFL shifted across the head at 2.84 Hz. The FFL and shift assembly rotates at 0.1 Hz, yielding an 5 s resolution for time series imaging. The resonant drive coil is powered a 50 A peak, 26.3 kHz sinusoidal waveform producing an 8 mT peak drive field. Signal is detected with a solenoidal two-part gradiometer connected to a transformer and preamplifier before digitization at 1 MHz. We acquire 1D projections at 27 angles per 180-degree image.
A human neuroimaging modality offering an order-of-magnitude improvement in our ability to detect CBV changes associated with brain activation offers the promise of identifying subtle functional differences in individuals that would have previously required a large group average. This could potentially facilitate the transition of functional neuroimaging from its current role as a neuro-scientific tool into a more widely used clinical tool.
Our human-capable MPI scanner uses a 1.13 T/m permanent magnet (PM) FFL shifted across the head at 2.84 Hz. The FFL and shift assembly rotates at 0.1 Hz, yielding an 5 s resolution for time series imaging. The resonant drive coil is powered a 50 A peak, 26.3 kHz sinusoidal waveform producing an 8 mT peak drive field. Signal is detected with a solenoidal two-part gradiometer connected to a transformer and preamplifier before digitization at 1 MHz. We acquire 1D projections at 27 angles per 180-degree image.
A human neuroimaging modality offering an order-of-magnitude improvement in our ability to detect CBV changes associated with brain activation offers the promise of identifying subtle functional differences in individuals that would have previously required a large group average. This could potentially facilitate the transition of functional neuroimaging from its current role as a neuro-scientific tool into a more widely used clinical tool.
*This work was supported by the National Institute of Biomedical Imaging and Bioengineering (NIBIB), of the National Institutes ofHealth (NIH) under award numbers U01EB025121.
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Publication: AC Barksdale, FH Niebel, et al International Journal on Magnetic Particle Imaging IJMPI 11 (1 Suppl 1)
E Mattingly, M Śliwiak, E Mason, et al Physics in Medicine & Biology 70 (1), 015019.
Presenters
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Lawrence L Wald
- Harvard Medical School