Eddy current-shielded x-space relaxometer for sensitive magnetic nanoparticle characterization

Bauer, Lisa; Hensley, Daniel; Zheng, Bo; Tay, Zhi Wei; Goodwill, Patrick; Griswold, Mark A.; Conolly, Steven M.

doi:10.1063/1.4950779

Cited by 13 publications

(7 citation statements)

References 34 publications

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“…5 ), demonstrating the AWR is quantitative for SPIO amount. We observed the limit of detection (SNR = 1) to be ~20 ng, showing more than 10-fold improvement from prior relaxometers 48 76 .…”

Section: Resultsmentioning

confidence: 68%

A High-Throughput, Arbitrary-Waveform, MPI Spectrometer and Relaxometer for Comprehensive Magnetic Particle Optimization and Characterization

Tay

Goodwill

Hensley

et al. 2016

Sci Rep

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Magnetic Particle Imaging (MPI) is a promising new tracer modality with zero attenuation deep in tissue, high contrast and sensitivity, and an excellent safety profile. However, the spatial resolution of MPI is limited to around 1 mm currently and urgently needs to be improved for clinical applications such as angiography and brain perfusion. Although MPI resolution is highly dependent on tracer characteristics and the drive waveforms, optimization is limited to a small subset of possible excitation strategies by current MPI hardware that only does sinusoidal drive waveforms at very few frequencies. To enable a more comprehensive and rapid optimization of drive waveforms for multiple metrics like resolution and signal strength simultaneously, we demonstrate the first untuned MPI spectrometer/relaxometer with unprecedented 400 kHz excitation bandwidth and capable of high-throughput acquisition of harmonic spectra (100 different drive-field frequencies in only 500 ms). It is also capable of arbitrary drive-field waveforms which have not been experimentally evaluated in MPI to date. Its high-throughput capability, frequency-agility and tabletop size makes this Arbitrary Waveform Relaxometer/Spectrometer (AWR) a convenient yet powerfully flexible tool for nanoparticle experts seeking to characterize magnetic particles and optimize MPI drive waveforms for in vitro biosensing and in vivo imaging with MPI.

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Section: Resultsmentioning

confidence: 68%

A High-Throughput, Arbitrary-Waveform, MPI Spectrometer and Relaxometer for Comprehensive Magnetic Particle Optimization and Characterization

Tay

Goodwill

Hensley

et al. 2016

Sci Rep

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“…MPI relaxometry measurements were performed using a custom x -spaced magnetic particle relaxometer. − The MPI relaxometry measurements were analyzed for all core–shell (CS) NC samples (16, 18, 20, and 23 nm NCs, before and after thermal annealing) under sinusoidal magnetic field excitation at 16.8 kHz and 20 mT. The normalized point spread function (PSF) and signal-to-noise ratio (SNR) of the measured MPI signals were compared with a commercial MPI tracer, VivoTrax (Figure a,b).…”

Section: Resultsmentioning

confidence: 99%

“…MPI analyses were performed using a custom-made MPI relaxometer device at Case Western Reserve University. − A series of core–shell NCs of various sizes that were subjected to different thermal treatment methods were analyzed on an MPI relaxometer at a sample volume of 400 μL and 1.0 mg Fe /mL NC content. All MPI relaxometry measurements were performed in triplicate and conducted under a magnetic excitation field strength and frequency of 20 mT and 16.8 kHz, respectively.…”

Section: Experimental Sectionmentioning

confidence: 99%

From Core–Shell FeO/Fe₃O₄ to Magnetite Nanocubes: Enhancing Magnetic Hyperthermia and Imaging Performance by Thermal Annealing

Sojková,

Rizzo,

Di Girolamo

et al. 2023

Chem. Mater.

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We report the synthesis of mostly magnetite nanocubes (NCs) in the size range of 16−23 nm starting from FeO/Fe 3 O 4 core−shell NCs and employing a thermal decomposition method, followed by thermal treatment. To induce the phase transformation, the as-prepared NCs were thermally annealed either directly in an organic solvent before their transfer into water or by a thermal process in an aqueous solution after coating the NCs with an amphiphilic polymer shell to render them soluble in water. The effects of NCs' size and type of post-synthesis annealing on improving their magnetic properties were investigated. The specific absorption rate (SAR) values, which measure the magnetic hyperthermia heating efficiency, were compared directly in water or in a viscous medium of glycerol/water mixtures to mimic the intratumoral dense environment. Among all samples, the 20 nm NCs annealed in organic solvent show the best heating capabilities. The 24 nm NCs exposed to the water annealing process are also able to achieve very high SAR values. Remarkably, all NC samples subjected to annealing exhibit heating efficiency values which are negligibly affected by the viscous media, thus demonstrating their unique SAR performance in a viscous-independent manner. For 20 nm NCs, a threefold higher magnetic particle imaging signal compared to the commercial tracer VivoTrax, and, at the same time, good magnetic resonance imaging contrast were measured.

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“…In addition, insufficient shielding may cause eddy currents on the selection field permanent magnets, which in turn can induce signal on the receive coil [32], [33]. Likewise, ambient interferences may also become problematic due to insufficient shielding of the receive coil and/or transmit/receive filter chains [34]. Under low signal conditions, such as in vivo cases, these harmonic interferences can become a problem even for well-tuned systems.…”

Section: Discussionmentioning

confidence: 99%

Partial FOV Center Imaging (PCI): A Robust X-Space Image Reconstruction for Magnetic Particle Imaging

Kurt

Muslu

Sarıtaş

2020

IEEE Trans. Med. Imaging

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Magnetic Particle Imaging (MPI) is an emerging medical imaging modality that images the spatial distribution of superparamagnetic iron oxide (SPIO) nanoparticles using their nonlinear response to applied magnetic fields. In standard x-space approach to MPI, the image is reconstructed by gridding the speed-compensated nanoparticle signal to the instantaneous position of the field free point (FFP). However, due to safety limits on the drive field, the field-of-view (FOV) needs to be covered by multiple relatively small partial field-of-views (pFOVs). The image of the entire FOV is then pieced together from individually processed pFOVs. These processing steps can be sensitive to non-ideal signal conditions such as harmonic interference, noise, and relaxation effects. In this work, we propose a robust x-space reconstruction technique, Partial FOV Center Imaging (PCI), with substantially simplified pFOV processing. PCI first forms a raw image of the entire FOV by mapping MPI signal directly to pFOV center locations. The corresponding MPI image is then obtained by deconvolving this raw image by a compact kernel, whose fully-known shape solely depends on the pFOV size. We analyze the performance of the proposed reconstruction via extensive simulations, as well as imaging experiments on our in-house FFP MPI scanner. The results show that PCI offers a trade-off between noise robustness and interference robustness,

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Eddy current-shielded x-space relaxometer for sensitive magnetic nanoparticle characterization

Cited by 13 publications

References 34 publications

A High-Throughput, Arbitrary-Waveform, MPI Spectrometer and Relaxometer for Comprehensive Magnetic Particle Optimization and Characterization

A High-Throughput, Arbitrary-Waveform, MPI Spectrometer and Relaxometer for Comprehensive Magnetic Particle Optimization and Characterization

From Core–Shell FeO/Fe₃O₄ to Magnetite Nanocubes: Enhancing Magnetic Hyperthermia and Imaging Performance by Thermal Annealing

Partial FOV Center Imaging (PCI): A Robust X-Space Image Reconstruction for Magnetic Particle Imaging

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Eddy current-shielded x-space relaxometer for sensitive magnetic nanoparticle characterization

Cited by 13 publications

References 34 publications

A High-Throughput, Arbitrary-Waveform, MPI Spectrometer and Relaxometer for Comprehensive Magnetic Particle Optimization and Characterization

A High-Throughput, Arbitrary-Waveform, MPI Spectrometer and Relaxometer for Comprehensive Magnetic Particle Optimization and Characterization

From Core–Shell FeO/Fe3O4 to Magnetite Nanocubes: Enhancing Magnetic Hyperthermia and Imaging Performance by Thermal Annealing

Partial FOV Center Imaging (PCI): A Robust X-Space Image Reconstruction for Magnetic Particle Imaging

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From Core–Shell FeO/Fe₃O₄ to Magnetite Nanocubes: Enhancing Magnetic Hyperthermia and Imaging Performance by Thermal Annealing