MRI of fast-relaxing spins

Garwood, Michael

doi:10.1016/j.jmr.2013.01.011

Cited by 23 publications

(13 citation statements)

References 54 publications

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“…Three NMR pulse sequences were used to measure the saturation of the rock core: single‐pulse free induction decay (FID), zero echo time 1‐D imaging (ZTE), and Carr‐Purcell‐Meiboom‐Gill (CPMG) 1‐D T 2 relaxation [ Callaghan , ; Garwood , ; Weiger et al ., ]. The NMR signal is detected for the 1 H protons so is not sensitive to CO 2 , air, fluorine, or any solid parts of the sample.…”

Section: Experimental Methodsmentioning

confidence: 99%

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NMR study comparing capillary trapping in Berea sandstone of air, carbon dioxide, and supercritical carbon dioxide after imbibition of water

Prather

Bray

Seymour

et al. 2016

Water Resources Research

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Nuclear magnetic resonance (NMR) techniques were used to study the capillary trapping mechanisms relevant to carbon sequestration. Capillary trapping is an important mechanism in the initial trapping of supercritical CO2 in the pore structures of deep underground rock formations during the sequestration process. Capillary trapping is considered the most promising trapping option for carbon sequestration. NMR techniques noninvasively monitor the drainage and imbibition of air, CO2, and supercritical CO2 with DI H2O at low capillary numbers in a Berea sandstone rock core under conditions representative of a deep underground saline aquifer. Supercritical CO2 was found to have a lower residual nonwetting (NW) phase saturation than that of air and CO2. Supercritical CO2 behaves differently than gas phase air or CO2 and leads to a reduction in capillary trapping. NMR relaxometry data suggest that the NW phase, i.e., air, CO2, or supercritical CO2, is preferentially trapped in larger pores. This is consistent with snap‐off conditions being more favorable in macroscale pores, as NW fluids minimize their contact area with the solid and hence prefer larger pores.

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Section: Experimental Methodsmentioning

confidence: 99%

“…The ZTE imaging sequence [ Garwood , ; Weiger et al ., ], depicted in Figure , has been specifically designed to allow the imaging of fast relaxing NMR signals of short T 2 values. This is achieved by switching on a readout gradient before any RF pulse excitation.…”

Section: Experimental Methodsmentioning

confidence: 99%

NMR study comparing capillary trapping in Berea sandstone of air, carbon dioxide, and supercritical carbon dioxide after imbibition of water

Prather

Bray

Seymour

et al. 2016

Water Resources Research

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“…In interleaved sequences, signals decaying more rapidly than the system dead times cannot be detected, whereas CEA continuously monitors the MR signal even during RF excitation. Thus, tightly bounded water in bone, for example, is not visible with interleaved NMR approaches [13][14][15][16][17], and new contrast mechanisms and novel sequences may be developed with further research on CEA.…”

Section: Methodsmentioning

confidence: 99%

Active decoupling of RF coils using a transmit array system

Özen

Bock

Atalar

2015

Magn Reson Mater Phy

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“…In recent years, several techniques classified as zero and ultrashort echo time (ZTE and UTE, respectively) imaging as well as sweep imaging with Fourier transformation (SWIFT) methods have been developed to target short T 2 protons . Depending on the T 2 domain of the protons of interest different approaches are used.…”

Section: Introductionmentioning

confidence: 99%

Radiofrequency phase encoded half‐pulses in simultaneous multislice ultrashort echo time imaging

Rettenmeier

Stenger

2019

Magnetic Resonance in Med

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Purpose To describe a simultaneous multislice (SMS) ultrashort echo time (UTE) imaging method using radiofrequency phase encoded half‐pulses in combination with power independent of number of slices (PINS) inversion recovery (IR) pulses to generate multiple‐slice images with short T2* contrasts in less than 3 min with close to an eightfold acceleration compared with a standard 2D approach. Theory and Methods Radiofrequency phase encoding is applied in an SMS (NSMS = 4) excitation scheme using “sinc” half‐pulses. With the use of coil sensitivity encoding (SENSE) and controlled aliasing in parallel imaging (CAIPI) in combination with a gradient echo 2D spiral readout trajectory and IR PINS pulses for contrast enhancement a fast UTE sequence is developed. Images are obtained using a model‐based reconstruction method. Sequence details and performance tests on phantoms as well as the heads of healthy volunteers at 3T are presented. Results An SMS UTE sequence with an undersampling factor of 4 is developed using radiofrequency phase encoded half‐pulses and PINS IR pulses which enables the acquisition of 8 slices at 0.862 mm2 resolution in less than 3‐min scan time. UTE images of the head are obtained showing highlighted signal of cortical bone. Image quality and T2 contrast are comparable to the one obtained by corresponding single slice acquisitions with only minor deviations. Conclusions The method combining radiofrequency phase encoded SMS half‐pulses and PINS IR pulses presents a suitable approach to SMS UTE imaging. The usage of coil sensitivity information and increased sampling density by means of interleaved slice group acquisitions allows to reduce the total scan time by a factor close to 8.

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MRI of fast-relaxing spins

Cited by 23 publications

References 54 publications

NMR study comparing capillary trapping in Berea sandstone of air, carbon dioxide, and supercritical carbon dioxide after imbibition of water

NMR study comparing capillary trapping in Berea sandstone of air, carbon dioxide, and supercritical carbon dioxide after imbibition of water

Active decoupling of RF coils using a transmit array system

Radiofrequency phase encoded half‐pulses in simultaneous multislice ultrashort echo time imaging

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