Electronic Field Free Line Rotation and Relaxation Deconvolution in Magnetic Particle Imaging

Bente, Klaas; Weber, Matthias; Graeser, Matthias; Sattel, Timo F.; Erbe, Marlitt; Buzug, Thorsten M.

doi:10.1109/tmi.2014.2364891

Cited by 59 publications

(49 citation statements)

References 35 publications

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“…Both MPI and V/Q have relatively lower spatial resolution – roughtly 1.5 mm and 3 mm respectively – compared to the <0.5 mm spatial resolution available for the latest CT scanners, but V/Q and CTPA have similar diagnostic power for PE because nuclear medicine provides superior contrast (Goodwill and Conolly 2010; Cecchin et al 2015; Leblanc and Paul 2010). Regardless, MPI resolution can and is being improved rapidly with the continued development of MPI-optimized SPIOs, higher gradient scanners, and computational approaches such as frequency based MPI and deconvolution (Bente et al 2015; Goodwill and Conolly 2010; Goodwill, Croft, and Konkle 2013; Ferguson, Khandhar, Kemp, et al 2015; Grüttner et al 2013; J. Rahmer, J. Weizenecker, et al 2012).…”

Section: Discussionmentioning

confidence: 99%

Firstin vivomagnetic particle imaging of lung perfusion in rats

Zhou¹,

Jeffris²,

Yu³

et al. 2017

Phys. Med. Biol.

102

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Pulmonary embolism (PE), along with the closely related condition of deep vein thrombosis, affect an estimated 600,000 patients in the US per year. Untreated, PE carries a mortality rate of 30%. Because many patients experience mild or non-specific symptoms, imaging studies are necessary for definitive diagnosis of PE. Iodinated CT pulmonary angiography (CTPA) is recommended for most patients, while nuclear medicine-based ventilation/perfusion (V/Q) scans are reserved for patients in whom the use of iodine is contraindicated. Magnetic particle imaging (MPI) is an emerging tracer imaging modality with high image contrast (no tissue background signal) and sensitivity to superparamagnetic iron oxide (SPIO) tracer. Importantly, unlike CT or nuclear medicine, MPI uses no ionizing radiation. Further, MPI is not derived from magnetic resonance imaging (MRI); MPI directly images SPIO tracers via their strong electronic magnetization, enabling deep imaging of anatomy including within the lungs, which is very challenging with MRI. Here, the first high-contrast in vivo MPI lung perfusion images of rats are shown using a novel lung perfusion agent, MAA-SPIOs.

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Section: Discussionmentioning

confidence: 99%

Firstin vivomagnetic particle imaging of lung perfusion in rats

Zhou¹,

Jeffris²,

Yu³

et al. 2017

Phys. Med. Biol.

102

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“…We have found that we can accurately model MPI image data by incorporating a firstorder Debye relaxation term. 4,19,20 This provides powerful intuition and accurately predictive experimental MPI imaging results.…”

Section: Spio Relaxation Physicsmentioning

confidence: 99%

“…We have also experimentally seen that the Debye model accurately predicts images in the imager 19 and the experimentally measured PSFs of other groups. 20 …”

Section: A Resolution Improvement With Lower Drive Field Strengthsmentioning

confidence: 99%

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Low drive field amplitude for improved image resolution in magnetic particle imaging

et al. 2015

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Purpose: Magnetic particle imaging (MPI) is a new imaging technology that directly detects superparamagnetic iron oxide nanoparticles. The technique has potential medical applications in angiography, cell tracking, and cancer detection. In this paper, the authors explore how nanoparticle relaxation affects image resolution. Historically, researchers have analyzed nanoparticle behavior by studying the time constant of the nanoparticle physical rotation. In contrast, in this paper, the authors focus instead on how the time constant of nanoparticle rotation affects the final image resolution, and this reveals nonobvious conclusions for tailoring MPI imaging parameters for optimal spatial resolution. Methods: The authors first extend x-space systems theory to include nanoparticle relaxation. The authors then measure the spatial resolution and relative signal levels in an MPI relaxometer and a 3D MPI imager at multiple drive field amplitudes and frequencies. Finally, these image measurements are used to estimate relaxation times and nanoparticle phase lags.Results: The authors demonstrate that spatial resolution, as measured by full-width at half-maximum, improves at lower drive field amplitudes. The authors further determine that relaxation in MPI can be approximated as a frequency-independent phase lag. These results enable the authors to accurately predict MPI resolution and sensitivity across a wide range of drive field amplitudes and frequencies. Conclusions: To balance resolution, signal-to-noise ratio, specific absorption rate, and magnetostimulation requirements, the drive field can be a low amplitude and high frequency. Continued research into how the MPI drive field affects relaxation and its adverse effects will be crucial for developing new nanoparticles tailored to the unique physics of MPI. Moreover, this theory informs researchers how to design scanning sequences to minimize relaxation-induced blurring for better spatial resolution or to exploit relaxation-induced blurring for MPI with molecular contrast. C 2016 American Association of Physicists in Medicine. [http://dx

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“…Due to the small magnitude of higher harmonics of the particle signal, the decisive advantage of an FFL is a higher signal-to-noise ratio (SNR) at equal bore size and gradient strength. As a drawback, while a selection field which yields an FFP only requires a coil pair in Maxwell configuration the necessary coil topology to generate and move an FFL fully electronically [4] is more complex and energy consuming. A reasonable setup for an FFL imaging-device contains two electromagnetic quadrupoles each one consisting of two orthogonally arranged Maxwell coil-pairs and furthermore, another Maxwell coil-pair aligned along the bore axis.…”

Section: Field-free Line Imagingmentioning

confidence: 99%

Magnetic-field measurement and simulation of a field-free line magnetic-particle scanner

Stelzner¹,

Buzug²

2017

Current Directions in Biomedical Engineering

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Abstract:In 2005, B. Gleich and J. Weizenecker initially presented the tracer based medical imaging modality Magnetic Particle Imaging (MPI). It uses the nonlinear magnetization behavior of super paramagnetic iron oxide nanoparticles (SPIONs). MPI has the potential to perform real-time imaging in the sub millimeter-range without the use of harmful radiation. To acquire a particle signal from the tracer, an alternating homogenous magnetic field (drive field) is applied. Due to the nonlinearity of the particle magnetization, the magnetic field is distorted and higher harmonics are generated that indicate a particle concentration within the field of view (FOV). For the spatial distribution, another magnetic field that exhibits a high gradient (selection field) is applied simultaneously. Basically, there are two different types of selection fields containing either a fieldfree point (FFP) or a field-free line (FFL). Because of magnetic saturation, only SPIONs within the close vicinity of the FFP or FFL contribute to the particle signal. As the FFP is moved by the drive field through the FOV a spatial distribution of the SPIONs can be obtained. In the other encoding concept, the FFL rotates and is additionally translated by the drive field to obtain one dimensional projections for various angles. In this work, the currently world's largest FFL MPI Scanner is investigated. Single components of the generated magnetic field are measured precisely to accomplish an accurate simulation of a translating and rotating FFL.

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Electronic Field Free Line Rotation and Relaxation Deconvolution in Magnetic Particle Imaging

Cited by 59 publications

References 35 publications

Firstin vivomagnetic particle imaging of lung perfusion in rats

Firstin vivomagnetic particle imaging of lung perfusion in rats

Low drive field amplitude for improved image resolution in magnetic particle imaging

Magnetic-field measurement and simulation of a field-free line magnetic-particle scanner

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