Linearity and Shift Invariance for Quantitative Magnetic Particle Imaging

Lu, Kuan; Goodwill, Patrick; Sarıtaş, Emine Ülkü; Zheng, Bo; Conolly, Steven M.

doi:10.1109/tmi.2013.2257177

Cited by 95 publications

(135 citation statements)

References 29 publications

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“…4). 19,43,[46][47][48] A large full FOV ensures that the sample reaches full saturation at the edges of the FOV. The partial FOVs are similar in concept to imaging stations described elsewhere.…”

Section: C Partial Fov Scanning To Measure Spatial Resolutionmentioning

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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Section: C Partial Fov Scanning To Measure Spatial Resolutionmentioning

confidence: 99%

“…The partial FOVs are velocity compensated, DC offset corrected, and then stitched to form the full FOV. 43 Positive-and negative-velocity scans are reconstructed separately.…”

Section: C Partial Fov Scanning To Measure Spatial Resolutionmentioning

confidence: 99%

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

et al. 2015

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“…This would require little additional hardware, but would necessitate employing a more complicated reconstruction scheme, based on partial FOVs. 12 For most users, a high-amplitude excitation field alone should be sufficient and has the added benefit of keeping relaxometer construction and signal processing simple. It should be noted that the relaxometer may also be used as a spectrometer.…”

Section: Discussionmentioning

confidence: 99%

“…To recover the lost signal at the fundamental frequency, which corresponds to image DC signal, we can pin the edges of the reconstructed PSF to zero. 12 Here we are making the assumption that at these large magnitudes in applied field, the particles are fully saturated and cannot yield a signal. For excitation waveforms with amplitudes much larger than the characteristic saturation of the tracer, this is well justified.…”

Section: Signal Reconstructionmentioning

confidence: 99%

“…[9][10][11] Furthermore, x-space MPI requires no prior knowledge about the tracer and has been proven to be a linear and shift-invariant (LSI) imaging system. 12 An alternative MPI reconstruction approach is known as harmonic-space MPI or system matrix reconstruction. While the governing physical principles are the same, the two techniques differ in both data acquisition and image reconstruction methods.…”

Section: Introductionmentioning

confidence: 99%

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

Bauer

Hensley

Zheng

et al. 2016

Review of Scientific Instruments

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The development of magnetic particle imaging (MPI) has created a need for optimized magnetic nanoparticles. Magnetic particle relaxometry is an excellent tool for characterizing potential tracers for MPI. In this paper, we describe the design and construction of a high-throughput tabletop relaxometer that is able to make sensitive measurements of MPI tracers without the need for a dedicated shield room. Published by AIP Publishing. [http://dx

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An anatomically correct 3D‐printed mouse phantom for magnetic particle imaging studies

Sarna

Marrero-Morales

DeGroff

et al. 2022

Bioengineering & Transla Med

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We report anatomically correct 3D‐printed mouse phantoms that can be used to plan experiments and evaluate analysis protocols for magnetic particle imaging (MPI) studies. The 3D‐printed phantoms were based on the Digimouse 3D whole body mouse atlas and incorporate cavities representative of a liver, brain tumor, and orthotopic breast cancer tumor placed in anatomically correct locations, allowing evaluation of the effect of precise doses of MPI tracer. To illustrate their use, a constant tracer iron mass was present in the liver for the breast (200 μgFe) and brain tumor (10 μgFe) model, respectively, while a series of decreasing tracer iron mass was placed in the tumor region. MPI scans were acquired in 2D and 3D high sensitivity and high sensitivity/high resolution (HSHR) modes using a MOMENTUM imager. A thresholding algorithm was used to define regions of interest (ROIs) in the scans and the tracer mass in the liver and tumors was calculated by comparison of the signal in their respective ROI against that of known mass fiducials that were included in each scan. The results demonstrate that this approach to image analysis provides accurate estimates of tracer mass. Additionally, the results show how the limit of detection in MPI is sensitive to the details of tracer distribution in the subject, as we found that a greater tracer mass in the liver cavity resulted in poorer sensitivity in tumor regions. These experiments illustrate the utility of the reported 3D‐printed anatomically correct mouse phantoms in evaluating methods to analyze MPI scans and plan in vivo experiments.

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Linearity and Shift Invariance for Quantitative Magnetic Particle Imaging

Cited by 95 publications

References 29 publications

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

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

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

An anatomically correct 3D‐printed mouse phantom for magnetic particle imaging studies

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