Eddy current compensation for delta relaxation enhanced MR by dynamic reference phase modulation

Hoelscher, Uvo Christoph; Jakob, Peter M.

doi:10.1007/s10334-012-0335-6

Cited by 7 publications

(17 citation statements)

References 10 publications

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“…FFC‐MRI can be implemented with a variety of pulse sequences, where there is a specific time allotted during the sequence to allow the appropriate magnetic field shift. However, this obviously increases image acquisition time and design of the field‐cycling system must be optimized to mitigate potential eddy currents, which could cause imaging artefacts and reduced SNR …”

Section: Discussionmentioning

confidence: 99%

“…FFC‐MRI requires modulation of the magnetic field, B 0 , prior to image acquisition . The basis of field‐cycling MR is the ability to rapidly switch between magnetic field strengths for varying durations of relaxation prior to signal acquisition without causing field‐cycling‐induced image artefacts . Implementation of FFC‐MRI has several technical challenges.…”

Section: Introductionmentioning

confidence: 99%

“…Since the enhancement of MR contrast is non‐negligible for inactive agents, it is highly desirable to suppress signal from tissues that are enhanced by nearby unbound contrast agent as well as signal arising simply from unenhanced tissue. This can be accomplished using magnetic field‐cycling methods with MRI . This increased target specificity is particularly useful for situations where pre‐injection images are not available for subtraction from those acquired post‐injection.…”

Section: Introductionmentioning

confidence: 99%

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Nuclear magnetic relaxation dispersion of murine tissue for development of T₁ (R₁) dispersion contrast imaging

Araya

Martinez-Santiesteban

Handler

et al. 2017

NMR in Biomedicine

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This study quantified the spin-lattice relaxation rate (R 1 ) dispersion of murine tissues from 0.24 mT to 3 T. A combination of ex vivo and in vivo spin-lattice relaxation rate measurements were acquired for murine tissue. Selected brain, liver, kidney, muscle, and fat tissues were excised and R 1 dispersion profiles were acquired from 0.24 mT to 1.0 T at 37°C, using a fast field-cycling MR (FFC-MR) relaxometer. In vivo R 1 dispersion profiles of mice were acquired from 1.26 T to 1.74 T at 37°C, using FFC-MRI on a 1.5 T scanner outfitted with a field-cycling insert electromagnet to dynamically control B 0 prior to imaging. Images at five field strengths (1.26, 1.39, 1.5, 1.61, 1.74 T) were acquired using a field-cycling pulse sequence, where B 0 was modulated for varying relaxation durations prior to imaging. R 1 maps and R 1 dispersion (ΔR 1 /ΔB 0 ) were calculated at 1.5 T on a pixel-by-pixel basis. In addition, in vivo R 1 maps of mice were acquired at 3 T. At fields less than 1 T, a large R 1 magnetic field dependence was observed for tissues. ROI analysis of the tissues showed little relaxation dispersion for magnetic fields from 1.26 T to 3 T. Our tissue measurements show strong R 1 dispersion at field strengths less than 1 T and limited R 1 dispersion at field strengths greater than 1 T. These findings emphasize the inherent weak R 1 magnetic field dependence of healthy tissues at clinical field strengths. This characteristic of tissues can be exploited by a combination of FFC-MRI and T 1 contrast agents that exhibit strong relaxivity magnetic field dependences (inherent or by binding to a protein), thereby increasing the agents' specificity and sensitivity. This development can provide potential insights into protein-based biomarkers using FFC-MRI to assess early changes in tumour development, which are not easily measureable with conventional MRI. MRI has a history of constant technical progress towards higher magnetic field strengths for imaging. 1 The progressive increases in magnetic field strength have been spurred by significant gains in the signal-to-noise ratio (SNR), and spectral and spatial resolution exploited in imaging of anatomy and brain function. [2][3][4][5] While high and ultra-high magnetic field strengths are attractive for producing exquisite images of internal structures with unprecedented detail that aid in tissue characterization, imaging at these magnetic field strengths results in very little difference in the relaxation times of different tissues, thereby losing the variability of an important intrinsic tissue property that leads to image contrast. 6,7 Differences in Abbreviations used: B P , polarization magnetic field; B R , relaxation magnetic field; dreMR, delta relaxation enhanced MR; FFC-MR, fast field-cycling MR; FFC-MRI, fast field-cycling MRI; FID, free induction decay; FSE, fast spin-echo; NMRD, nuclear magnetic relaxation dispersion; NP, non-polarized; PP, pre-polarized; ROI, region of interest; SNR, signal-to-noise ratio

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nuclear magnetic relaxation dispersion of murine tissue for development of T₁ (R₁) dispersion contrast imaging

Araya

Martinez-Santiesteban

Handler

et al. 2017

NMR in Biomedicine

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“…During the acquisition of FFC-MRI images, eddy currents then are compensated by dynamic reference phase modulation (eDREAM) as proposed in [7]. This method can be directly implemented into the MRI pulse sequence and does not require any additional hardware adaptations.…”

Section: Eddy Current Characterization and Compensationmentioning

confidence: 99%

R 1 dispersion contrast at high field with fast field-cycling MRI

Bödenler

Basini

Casula

et al. 2018

Journal of Magnetic Resonance

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Contrast agents with a strong R dispersion have been shown to be effective in generating target-specific contrast in MRI. The utilization of this R field dependence requires the adaptation of an MRI scanner for fast field-cycling (FFC). Here, we present the first implementation and validation of FFC-MRI at a clinical field strength of 3 T. A field-cycling range of ±100 mT around the nominal B field was realized by inserting an additional insert coil into an otherwise conventional MRI system. System validation was successfully performed with selected iron oxide magnetic nanoparticles and comparison to FFC-NMR relaxometry measurements. Furthermore, we show proof-of-principle R dispersion imaging and demonstrate the capability of generating R dispersion contrast at high field with suppressed background signal. With the presented ready-to-use hardware setup it is possible to investigate MRI contrast agents with a strong R dispersion at a field strength of 3 T.

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“…Groups from the USA and Canada have also contributed with technological developments in this area [19][20][21][22]. All these FFC-MRI examples (and subsequent work, see for example [23][24][25][26][27]) were mainly thought from an MRI perspective. Even the concept of relaxometric imaging was originally approached from a pure MRI point of view, using a whole-body magnetic resonance imager [28,29].…”

Section: Introductionmentioning

confidence: 99%

A fast field-cycling MRI relaxometer for physical contrasts design and pre-clinical studies in small animals

Romero

Rodriguez

Anoardo

2020

Journal of Magnetic Resonance

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We present a fast field-cycling NMR relaxometer with added magnetic resonance imaging capabilities. The instrument operates at a maximum proton Larmor frequency of 5 MHz for a sample volume of 35 mL. The magnetic field homogeneity across the sample is 1400 ppm. The main field is generated with a notch-coil electromagnet of own design, fed with a current whose stability is 220 ppm. We show that images of reasonable quality can still be produced under such conditions. The machine is being designed for concept testing of the involved instrumentation and specific contrast agents aimed for field-cycling magnetic resonance imaging applications. The general performance of the prototype was tested through localized relaxometry experiments, T 1 -dispersion weighted images, temperature maps and T 1 -weighted images at different magnetic field intensities. We introduce the concept of positive and negative contrast depending on the use of pre-polarized or nonpolarized sequences. The system is being improved for pre-clinical studies in small animals.

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Eddy current compensation for delta relaxation enhanced MR by dynamic reference phase modulation

Abstract: eDREAM is a flexible eddy current compensation for dreMR. It is capable of completely removing the influence of eddy currents such that the dreMR images do not suffer from artifacts.

Cited by 7 publications

References 10 publications

Nuclear magnetic relaxation dispersion of murine tissue for development of T₁ (R₁) dispersion contrast imaging

Nuclear magnetic relaxation dispersion of murine tissue for development of T₁ (R₁) dispersion contrast imaging

R 1 dispersion contrast at high field with fast field-cycling MRI

A fast field-cycling MRI relaxometer for physical contrasts design and pre-clinical studies in small animals

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Eddy current compensation for delta relaxation enhanced MR by dynamic reference phase modulation

Abstract: eDREAM is a flexible eddy current compensation for dreMR. It is capable of completely removing the influence of eddy currents such that the dreMR images do not suffer from artifacts.

Cited by 7 publications

References 10 publications

Nuclear magnetic relaxation dispersion of murine tissue for development of T1 (R1) dispersion contrast imaging

Nuclear magnetic relaxation dispersion of murine tissue for development of T1 (R1) dispersion contrast imaging

R 1 dispersion contrast at high field with fast field-cycling MRI

A fast field-cycling MRI relaxometer for physical contrasts design and pre-clinical studies in small animals

Contact Info

Product

Resources

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Nuclear magnetic relaxation dispersion of murine tissue for development of T₁ (R₁) dispersion contrast imaging

Nuclear magnetic relaxation dispersion of murine tissue for development of T₁ (R₁) dispersion contrast imaging