Fast and quiet MRI using a swept radiofrequency

Idiyatullin, Djaudat; Corum, Curtis A.; Park, Jang Yeon; Garwood, Michael

doi:10.1016/j.jmr.2006.05.014

Cited by 316 publications

(350 citation statements)

References 31 publications

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“…It already has been applied in imaging of bone samples and thermoplastic objects. 15,16 Another approach without echo time spin evolution is zero echo time (ZTE) MR. [17][18][19][20] It is closely related to UTE and has been implemented on small animal MR systems. 21 A hard RF pulse is applied to accomplish spatially nonselective excitation that covers the full frequency bandwidth spanned by the readout gradient.…”

Section: Introductionmentioning

confidence: 99%

Zero Echo Time Magnetic Resonance Imaging of Contrast-Agent-Enhanced Calcium Phosphate Bone Defect Fillers

Sun

Ventura²,

Oosterwijk³

et al. 2013

Tissue Engineering Part C: Methods

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Calcium phosphate cements (CPCs) are widely used bone substitutes. However, CPCs have similar radiopacity as natural bone, rendering them difficult to be differentiated in classical X-ray and computed tomography imaging. As conventional magnetic resonance imaging (MRI) of bone is cumbersome, due to low water content and very short T 2 relaxation time, ultra-short echo time (UTE) and zero echo time (ZTE) MRI have been explored for bone visualization. This study examined the possibility to differentiate bone and CPC by MRI. T 1 and T 2 * values determined with UTE MRI showed little difference between bone and CPC; hence, these materials were difficult to separate based on T 1 or T 2 alone. Incorporation of ultra-small particles of iron oxide and gadopentetatedimeglumine (Gd-DTPA; 1 weight percentage [wt%] and 5 wt% respectively) into CPC resulted in visualization of CPC with decreased intensity on ZTE images in in vitro and ex vivo experiments. However, these additions had unfavorable effects on the solidification time and/or mechanical properties of the CPC, with the exception of 1% Gd-DTPA alone. Therefore, we tested this material in an in vivo experiment. The contrast of CPC was enhanced at an early stage postimplantation, and was significantly reduced in the 8 weeks thereafter. This indicates that ZTE imaging with Gd-DTPA as a contrast agent could be a valid radiation-free method to visualize CPC degradation and bone regeneration in preclinical experiments.

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Section: Introductionmentioning

confidence: 99%

Zero Echo Time Magnetic Resonance Imaging of Contrast-Agent-Enhanced Calcium Phosphate Bone Defect Fillers

Sun

Ventura²,

Oosterwijk³

et al. 2013

Tissue Engineering Part C: Methods

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“…When we attempted to image MNPs using MRI with a conventional transverse relaxation time ( * 2 T )-weighted imaging sequence, it was almost impossible due to large susceptibility-induced MR signal loss and image distortions in the regions near the MNPs. Recently, however, MRI pulse sequences capable of preserving the signal from spins with ultrashort * 2 T , such as ultrashort echo time (UTE) [17] and sweep imaging with Fourier transformation (SWIFT) sequences [18], have been developed. With these pulse sequences, MNPs can be detected and quantified based on the shortening of the longitudinal relaxation time of water (T 1 ) [18].…”

Section: Discussionmentioning

confidence: 99%

“…Recently, however, MRI pulse sequences capable of preserving the signal from spins with ultrashort * 2 T , such as ultrashort echo time (UTE) [17] and sweep imaging with Fourier transformation (SWIFT) sequences [18], have been developed. With these pulse sequences, MNPs can be detected and quantified based on the shortening of the longitudinal relaxation time of water (T 1 ) [18]. Zhang et al [19] reported that the reciprocal of T 1 measured using the SWIFT sequence combined with the Look-Locker method has a linear relationship with MNPs concentration up to 53.6 mM Fe.…”

Section: Discussionmentioning

confidence: 99%

Visualization of Magnetic Nanofibers Using Magnetic Particle Imaging

Murase

Mimura²,

Banura³

et al. 2015

OJMI

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Purpose: Magnetic nanofibers (MNFs) are nanofibers impregnated with magnetic nanoparticles (MNPs). Magnetic particle imaging (MPI) is a recently introduced imaging method that allows imaging of the spatial distribution of MNPs. The purpose of this study was to develop MNFs and to investigate the feasibility of visualizing them using MPI and of heating them using an alternating magnetic field (AMF). Materials and Methods: First, chitosan nanofibers were cross-linked with glutaraldehyde vapor in a sealed vial for 24 hours. Next, they were mixed with various concentrations of MNPs and the mixture was stirred for 1 hour using a magnetic stirrer. After the mixture was refrigerated at -80˚C for 24 hours, it was freeze-dried for 24 hours. The morphology of the resultant MNFs was characterized by scanning electron microscopy, and the magnetic properties were measured using a vibrating sample magnetometer. After these measurements, we imaged the MNFs using our MPI scanner, and investigated the correlation between the pixel values of the MPI image and the concentration of MNPs or the number of MNF sheets. We also heated the MNFs using AMF, and measured the temperature rise using an infrared thermometer. Results: The MNFs were successfully visualized using our MPI scanner, and the pixel values of the MPI image showed excellent correlation with the concentration of MNPs (r = 0.992) and the number of MNF sheets (r = 0.997). A significant temperature rise was observed under AMF, and the initial slope of the time-dependent temperature rise showed excellent correlation with the concentration of MNPs (r = 0.994) and the number of MNF sheets (r = 0.979). Conclusion: The MNFs developed in this study can be visualized using MPI and can be applied to magnetic hyperthermia. They will be useful in biomedicine including cancer therapy and tissue regeneration.

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“…The ability to capture short T 2 * signals is limited by the acquisition (= excitation) bandwidth (sw), which is simply the reciprocal of the dwell time (dw). Bloch simulations have shown that approximately 50 % or more of the available signal is measurable when dw ≤ T 2 * [6].…”

Section: Principles Of Swiftmentioning

confidence: 99%

“…A newer approach uses frequency-swept excitation to excite a flat and wide band of frequencies using low peak power, and by acquiring signals in gaps in the RF pulse, near optimal ultra-short T 2 * imaging is possible. This method is called SWeep Imaging with Fourier Transformation (SWIFT) [6,7]. Recent progress with SWIFT, as it relates to porous media research, is presented in this work.…”

Section: Introductionmentioning

confidence: 99%

Detecting Fleeting MRI Signals with Frequency-Modulated Pulses

Kobayashi¹,

Idiyatullin²,

Corum³

et al. 2011

AIP Conference Proceedings

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We describe a fundamentally different approach to MRI referred to as SWIFT (sweep imaging with Fourier transformation). SWIFT exploits time-shared RF excitation and signal acquisition, allowing capture of signal from spins with extremely short transverse relaxation time, T 2 *. The MR signal is acquired in gaps inserted into a broadband frequency-swept excitation pulse, which results in acquisition delays of only 1 -2 microseconds. In SWIFT, 3D k-space is sampled in a radial manner, whereby one projection of the object is acquired in the gaps of each frequencyswept pulse, allowing a repetition time (TR) on the order of the pulse length (typically 1 -3 milliseconds). Since the orientation of consecutive projections varies in a smooth manner (i.e., only small increments in the values of the x, y, z gradients occur from view to view), SWIFT scanning is close to inaudible and is insensitive to gradient timing errors and eddy currents. SWIFT images can be acquired in scan times similar to and sometimes faster than conventional 3D gradient echo techniques. With its ability to capture signals from ultrashort T 2 * spins, SWIFT promises to expand the role of MRI in areas of research where MRI previously played no or negligible role. In this article, we show wood and tooth images obtained with SWIFT as examples of materials with ultrashort T 2 *. Early experience suggests SWIFT can play a role in materials science and porous media research.

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Fast and quiet MRI using a swept radiofrequency

Cited by 316 publications

References 31 publications

Zero Echo Time Magnetic Resonance Imaging of Contrast-Agent-Enhanced Calcium Phosphate Bone Defect Fillers

Zero Echo Time Magnetic Resonance Imaging of Contrast-Agent-Enhanced Calcium Phosphate Bone Defect Fillers

Visualization of Magnetic Nanofibers Using Magnetic Particle Imaging

Detecting Fleeting MRI Signals with Frequency-Modulated Pulses

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