Reconstruction Enhancement by Denoising the Magnetic Particle Imaging System Matrix Using Frequency Domain Filter

Weber, Alexander; Weizenecker, J.; Heinen, Ulrich; Heidenreich, Michael; Buzug, Thorsten M.

doi:10.1109/tmag.2014.2332612

Cited by 10 publications

(4 citation statements)

References 10 publications

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“…Assuming the gradient field from ( 5), the fine system matrix ŜHR , that is used to constitute the phantom spectrum, accounts for an image resolution of 0.5 mT/pixel • (1.25 T/m) −1 = 0.4 mm/pixel. System matrices are denoised to reduce the impact of system matrix noise on the reconstructed image [37].…”

Section: E Image Reconstructionmentioning

confidence: 99%

System Matrix Based Reconstruction for Pulsed Sequences in Magnetic Particle Imaging

Mohn

Knopp

Boberg

et al. 2022

IEEE Trans. Med. Imaging

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Improving resolution and sensitivity will widen possible medical applications of magnetic particle imaging. Pulsed excitation promises such benefits, at the cost of more complex hardware solutions and restrictions on drive field amplitude and frequency. State-of-the-art systems utilize a sinusoidal excitation to drive superparamagnetic nanoparticles into the non-linear part of their magnetization curve, which creates a spectrum with a clear separation of direct feed-through and higher harmonics caused by the particles response. One challenge for rectangular excitation is the discrimination of particle and excitation signals, both broad-band. Another is the drive-field sequence itself, as particles that are not placed at the same spatial position, may react simultaneously and are not separable by their signal phase or shape. To overcome this potential loss of information in spatial encoding for high amplitudes, a superposition of shifting fields and drive-field rotations is proposed in this work. Upon close view, a system matrix approach is capable to maintain resolution, independent of the sequence, if the response to pulsed sequences still encodes information within the phase. Data from an Arbitrary Waveform Magnetic Particle Spectrometer with offsets in two spatial dimensions is measured and calibrated to guarantee device independence. Multiple sequence types and waveforms are compared, based on frequency space image reconstruction from emulated signals, that are derived from measured particle responses. A resolution of 1.0 mT (0.8 mm for a gradient of Manuscript

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Section: E Image Reconstructionmentioning

confidence: 99%

System Matrix Based Reconstruction for Pulsed Sequences in Magnetic Particle Imaging

Mohn

Knopp

Boberg

et al. 2022

IEEE Trans. Med. Imaging

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“…Prior to image reconstruction, SM denoising was applied with a frequency domain filter based on a discrete cosine transform (Weber et al 2015). 'Soft' thresholding with the threshold value of 0.03 was used.…”

Section: System Matrix Acquisitionsmentioning

confidence: 99%

Frequency-selective signal enhancement by a passive dual coil resonator for magnetic particle imaging

et al. 2022

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Objective. Magnetic particle imaging (MPI) visualizes the spatial distribution of magnetic nanoparticles. MPI already provides excellent temporal and good spatial resolution, however, to achieve translation into clinics, further advances in the fields of sensitivity, image reconstruction and tracer performance are needed. In this work, we propose a novel concept to enhance the MPI signal and image resolution by a purely passive receive coil insert for a preclinical MPI system. Approach. The passive dual coil resonator (pDCR) provides frequency-selective signal enhancement. This is enabled by the adaptable resonance frequency of the pDCR network, which is galvanically isolated from the MPI system and composed of two coaxial solenoids connected via a capacitor. The pDCR aims to enhance frequency components related to high mixing orders, which are crucial to achieve high spatial resolution. Main Results. In this study, system matrix measurements and image acquisitions of a resolution phantom are carried out to evaluate the performance of the pDCR compared to the integrated receive unit of the preclinical MPI and a dedicated rat-sized receive coil. Frequency-selective signal increase and spatial resolution enhancement are demonstrated. Significance. Common dedicated receive coils come along with noise-matched receive networks, which makes them costly and difficult to reproduce. The presented pDCR is a purely passive coil insert that gets along without any additional receive electronics. Therefore, it is cost-efficient, easy-to-handle and adaptable to other MPI scanners and potentially other applications providing the basis for a new breed of passive MPI receiver systems.

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“…( 5), the fine system matrix ŜHR , that is used to constitute the phantom spectrum, accounts for an image resolution of 0.5 mT/pixel • (1.25 T m −1 ) −1 = 0.4 mm/pixel. System matrices are denoised to reduce the impact of system matrix noise on the reconstructed image [32].…”

Section: Image Reconstructionmentioning

confidence: 99%

System Matrix based Reconstruction for Pulsed Sequences in Magnetic Particle Imaging

Mohn,

Knopp,

Boberg

et al. 2021

Preprint

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Improving resolution and sensitivity will widen possible medical applications of magnetic particle imaging in its clinical application. Pulsed excitation promises such benefits, at the cost of more complex hardware solutions and restrictions on drive field amplitude and frequency. In this work, a sequence is proposed, that combines high drive-field amplitudes and high frequency rectangular excitation. State of the art systems utilize a sinusoidal excitation to drive superparamagnetic nanoparticles into the non-linear part of their magnetization curve, which creates a spectrum with a clear separation of direct feed-through and higher harmonics caused by the particles response. One challenge for rectangular excitation is the discrimination of particle and excitation signals, both broad-band. Another is the drive-field sequence itself, as particles that are not placed at the same spatial position, may react simultaneously and are not separable by their signals phase or signal shape. This loss of information in spatial encoding is overcome in this work by utilizing a superposition of shifting fields and drive-field rotations. The software framework developed for this work processes measured data from an Arbitrary Waveform Magnetic Particle Spectrometer, which is calibrated to guarantee device independence. Multiple sequence types and waveforms are compared, based on frequency space image reconstruction from emulated signals, that are derived from these measured particle responses. A resolution of 1.0 mT (0.8 mm for a gradient of (-1.25, -1.25, 2.5) T m −1 ) in x-and y-direction was achieved and a superior sensitivity was detected on the basis of reference phantoms for the proposed sequence in this work.

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Reconstruction Enhancement by Denoising the Magnetic Particle Imaging System Matrix Using Frequency Domain Filter

Cited by 10 publications

References 10 publications

System Matrix Based Reconstruction for Pulsed Sequences in Magnetic Particle Imaging

System Matrix Based Reconstruction for Pulsed Sequences in Magnetic Particle Imaging

Frequency-selective signal enhancement by a passive dual coil resonator for magnetic particle imaging

System Matrix based Reconstruction for Pulsed Sequences in Magnetic Particle Imaging

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