Technical Note: Compact three‐tesla magnetic resonance imager with high‐performance gradients passes ACR image quality and acoustic noise tests

Weavers, Paul T.; Shu, Yunhong; Tao, Shengzhen; Huston, John; Lee, Seung Kyun; Graziani, Dominic; Mathieu, Jean Baptiste; Trzasko, Joshua D.; Foo, Thomas K.F.; Bernstein, Matt A.

doi:10.1118/1.4941362

Cited by 24 publications

(30 citation statements)

References 25 publications

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“…For example, when imaging the head, body GCs still produce a high amplitude of time-varying magnetic fields over the entire torso cross-section, which causes PNS without improving imaging quality. The advantage of smaller-sized GCs with a reduced linearity region diameter is that fields are limited primarily to the head, decreasing the amplitudes of time-varying electric fields and induced currents significantly, thereby increasing PNS thresholds substantially (Wade et al, 2016; Tan et al, 2016; Weavers et al, 2016). This permits even higher useable gradient performance than expected from hardware specifications alone, compared to body-sized gradient coils.…”

Section: Dedicated Gradient Concepts Suitable For Uhfmentioning

confidence: 99%

Gradient and shim technologies for ultra high field MRI

Winkler

Schmitt

Landes³

et al. 2018

NeuroImage

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Ultra High Field (UHF) MRI requires improved gradient and shim performance to fully realize the promised gains (SNR as well as spatial, spectral, diffusion resolution) that higher main magnetic fields offer. Both the more challenging UHF environment by itself, as well as the higher currents used in high performance coils, require a deeper understanding combined with sophisticated engineering modeling and construction, to optimize gradient and shim hardware for safe operation and for highest image quality. This review summarizes the basics of gradient and shim technologies, and outlines a number of UHF-related challenges and solutions. In particular, Lorentz forces, vibroacoustics, eddy currents, and peripheral nerve stimulation are discussed. Several promising UHF-relevant gradient concepts are described, including insertable gradient coils aimed at higher performance neuroimaging.

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Section: Dedicated Gradient Concepts Suitable For Uhfmentioning

confidence: 99%

Gradient and shim technologies for ultra high field MRI

Winkler

Schmitt

Landes³

et al. 2018

NeuroImage

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show abstract

“…Systems assessments of gradient linearity, PNS, and acoustic sound pressure levels were performed and the results were reported previously . To summarize, the results indicated that the 10th‐order spherical harmonic correction with both even and odd terms resulted in a residual RMS error of less than 0.36 mm .…”

Section: Resultsmentioning

confidence: 71%

Lightweight, compact, and high‐performance 3T MR system for imaging the brain and extremities

Foo

Laskaris

Vermilyea

et al. 2018

Magnetic Resonance in Med

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“…A novel, compact 3T MR scanner (C3T) was developed as a technology demonstrator under a National Institutes of Health (NIH)‐funded program. The motivation behind the C3T was to demonstrate the advantages offered by a lightweight, low‐cost, and high‐performance MR system.…”

mentioning

confidence: 99%

“…The C3T was designed with a high‐performance gradient system with a 42‐cm inner diameter. Due to its relatively small size, the gradient system can achieve 80 mT/m amplitude and 700 T/m/s slew rate simultaneously, while remaining below the peripheral nerve stimulation limit . To facilitate patient access, it was necessary to shift the imaging volume towards the patient end of the bore to accommodate both the head and shoulder.…”

mentioning

confidence: 99%

Improving apparent diffusion coefficient accuracy on a compact 3T MRI scanner using gradient nonlinearity correction

Tao

Shu

Tan

et al. 2018

Magnetic Resonance Imaging

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BACKGROUND Gradient non-linearity (GNL) leads to biased apparent diffusion coefficients (ADCs) in diffusion weighted imaging. A gradient non-linearity correction (GNLC) method has been developed for whole body systems, but yet to be tested for the new compact 3T (C3T) scanner which exhibits more complex GNL due to its asymmetrical design. PURPOSE To assess the improvement of ADC quantification with GNLC for the C3T scanner. STUDY TYPE Phantom measurements and retrospective analysis of patient data. PHANTOM/SUBJECTS A diffusion quality control phantom with vials containing 0-30% polyvinylpyrrolidone in water was used. For in-vivo data, 12 patient exams were analyzed (median age =33). FIELD STRENGTH/SEQUENCE Imaging was performed on the C3T and two commercial 3T scanners. A clinical DWI (TR = 10000 ms, TE = min, b = 1000 s/mm2) sequence was used for phantom imaging and 10 patient cases and a clinical DTI (TR = 6000-10000 ms, TE = min, b = 1000s/mm2) sequence was used for two patient cases. ASSESSMENT The 0% vial was measured along three orthogonal axes, and at two different temperatures. The ADC for each concentration was compared between the C3T and two whole body scanners. Cerebrospinal fluid and white matter ADCs were quantified for patient and compared to values in literature. STATISTICAL TEST Paired t-test and two-way ANOVA RESULTS For all PVP concentrations, the corrected ADC was within 2.5% of the reference ADC. On average, the ADC of cerebrospinal fluid and white matter post-GNLC were within 1% and 6% of values reported in literature respectively and were significantly different from the uncorrected data (p<0.05). DATA CONCLUSION This study demonstrated that GNL effects were more severe for the C3T due to the asymmetric gradient design, but our implementation of a GNLC compensated for these effects, resulting in ADC values that are in good agreement with values from literature.

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Technical Note: Compact three‐tesla magnetic resonance imager with high‐performance gradients passes ACR image quality and acoustic noise tests

Abstract: The compact system simultaneously allows for high gradient amplitude and high slew rate. Geometric distortion concerns have been mitigated by extending the spherical harmonic correction to higher orders. Acoustic noise is within the FDA limits.

Cited by 24 publications

References 25 publications

Gradient and shim technologies for ultra high field MRI

Gradient and shim technologies for ultra high field MRI

Lightweight, compact, and high‐performance 3T MR system for imaging the brain and extremities

Improving apparent diffusion coefficient accuracy on a compact 3T MRI scanner using gradient nonlinearity correction

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