Spatial resolution and sensitivity of magnetic susceptibility imaging

Thomas, Ian M.; Ma, Yanxue; Tan, S.; Wikswo, John P.

doi:10.1109/77.233581

Cited by 21 publications

(8 citation statements)

References 4 publications

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“…The magnetic inverse problem has been described in detail [40]. Two-dimensional magnetic susceptibility tomography (MST) methods have been developed for use on samples of uniform thickness [41]. Three-dimensional methods of MST have not been implemented, but the analytical groundwork for the method has been developed [42, 43].…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic AC susceptibility imaging (sASI) of magnetic nanoparticles

Ficko

Nadar

Diamond

2015

Journal of Magnetism and Magnetic Materials

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This study demonstrates a method for alternating current (AC) susceptibility imaging (ASI) of magnetic nanoparticles (mNPs) using low cost instrumentation. The ASI method uses AC magnetic susceptibility measurement to create tomographic images using an array of drive coils, compensation coils and fluxgate magnetometers. Using a spectroscopic approach in conjunction with ASI, a series of tomographic images can be created for each frequency measurement and is termed sASI. The advantage of sASI is that mNPs can be simultaneously characterized and imaged in a biological medium. System calibration was performed by fitting the in-phase and out-of-phase susceptibility measurements of an mNP sample with a hydrodynamic diameter of 100 nm to a Brownian relaxation model (R2 = 0.96). Samples of mNPs with core diameters of 10 and 40 nm and a sample of 100 nm hydrodynamic diameter were prepared in 0.5 ml tubes. Three mNP samples were arranged in a randomized array and then scanned using sASI with six frequencies between 425 and 925 Hz. The sASI scans showed the location and quantity of the mNP samples (R2 = 0.97). Biological compatibility of the sASI method was demonstrated by scanning mNPs that were injected into a pork sausage. The mNP response in the biological medium was found to correlate with a calibration sample (R2 = 0.97, p <0.001). These results demonstrate the concept of ASI and advantages of sASI.

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Section: Introductionmentioning

confidence: 99%

Spectroscopic AC susceptibility imaging (sASI) of magnetic nanoparticles

Ficko

Nadar

Diamond

2015

Journal of Magnetism and Magnetic Materials

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“…Imaging the resolution phantom with EPI resulted in substantial distortion in the phase encode direction, regardless of whether the PET insert was present in the MRI bore. This distortion is the result of low effective bandwidth of EPI imaging, together with the large susceptibility‐induced off‐resonance in the small plastic phantom . As the B 0 homogeneity was not affected by the PET insert, single‐shot EPI imaging of humans should not be a concern .…”

Section: Discussionmentioning

confidence: 99%

Simultaneous PET/MR imaging with a radio frequency‐penetrable PET insert

et al. 2017

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Purpose A brain sized radio-frequency (RF)-penetrable PET insert has been designed for simultaneous operation with MRI systems. This system takes advantage of electro-optical coupling and battery power to electrically float the PET insert relative to the MRI ground, permitting RF signals to be transmitted through small gaps between the modules that form the PET ring. This design facilitates the use of the built-in body coil for RF transmission, and thus could be inserted into any existing MR site wishing to achieve simultaneous PET/MR imaging. The PET detectors employ non-magnetic silicon photomultipliers in conjunction with a compressed sensing signal multiplexing scheme, and optical fibers to transmit analog PET detector signals out of the MRI room for decoding, processing, and image reconstruction. Methods The PET insert was first constructed and tested in a laboratory benchtop setting, where tomographic images of a custom resolution phantom were successfully acquired. The PET insert was then placed within a 3T body MRI system, and tomographic resolution/contrast phantom images were acquired both with only the B0 field present, and under continuous pulsing from different MR imaging sequences. Results The resulting PET images have comparable contrast-to-noise ratios (CNR) under all MR pulsing conditions: the maximum percent CNR relative difference for each rod type among all four PET images acquired in the MRI system has a mean of 14.0±7.7%. MR images were successfully acquired through the RF-penetrable PET shielding using only the built-in MR body coil, suggesting that simultaneous imaging is possible without significant mutual interference. Conclusions These results show promise for this technology as an alternative to costly integrated PET/MR scanners; a PET insert that is compatible with any existing clinical MRI system could greatly increase the availability, accessibility, and dissemination of PET/MR.

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“…the field map corresponding to the magn in an applied field of 285 pT. Other objects that have been scanned with the susceptometer system include high temperature superconducting films [6], samples of diamagnetic plexiglass [8] and superparamagnetic microspheres for imaging surface cracks [9] and blood circulation in animal models.…”

Section: Experimental Resumentioning

confidence: 99%

“…In this paper, we describe the design and development of our susceptometer and present preliminary data. Further experiments with the susceptometer are reported elsewhere [6,8,9]. (1) where B'M is the field due to the magnet tion 1.…”

Section: Introductionmentioning

confidence: 99%

A high resolution imaging susceptometer

Thomas

Lauder

et al. 1993

IEEE Trans. Appl. Supercond.

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High resolution magnetic susceptibility imaging is a new technique for investigating the composition of diamagnetic and paramagnetic objects. It might contribute to the nondestructive evaluation of critical components by identifying both surface and internal defects. In order to demonstrate the technique, we have attached magnetizing coils to our high resolution MicroSQUID magnetometer. With our present system, we can apply a nearly uniform field of 0.3 mT, 2.0-2.5 mm below the 3 mm diameter sensing coils. By placing a sample in this applied field and scanning, MicroSQUID measures the local magnetic field variations caused by the spatial distribution of magnetic susceptibility in the sample. The system has sufficient sensitivity to image susceptibility-induced field changes equal to 3 x of the applied field, in a 100 Hz bandwidth. We describe the concept of susceptibility imaging and present preliminary data.

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Spatial resolution and sensitivity of magnetic susceptibility imaging

Cited by 21 publications

References 4 publications

Spectroscopic AC susceptibility imaging (sASI) of magnetic nanoparticles

Spectroscopic AC susceptibility imaging (sASI) of magnetic nanoparticles

Simultaneous PET/MR imaging with a radio frequency‐penetrable PET insert

A high resolution imaging susceptometer

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