Time-of-Flight Flow Imaging Using NMR Remote Detection

Granwehr, Josef; Harel, Elad; Han, Songi; García, Sandra G.; Pines, Ayala Malach; Sen, Parongama; Song, Yi‐Qiao

doi:10.1103/physrevlett.95.075503

Cited by 71 publications

(81 citation statements)

References 27 publications

(22 reference statements)

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“…23,24 By decoupling the excitation and detection of the MR experiment, it is possible to obtain high sensitivity across the entire microfluidic device irrespective of the coil filling factor.…”

Section: Remote Detectionmentioning

confidence: 99%

Magnetic resonance detection: spectroscopy and imaging of lab-on-a-chip

Harel

2009

Lab Chip

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This mini-review is focused on the use of nuclear magnetic resonance (NMR) spectroscopy and imaging to study processes on lab-on-a-chip devices. NMR as an analytical tool is unmatched in its impact across nearly every area of science, from biochemistry and medicine to fundamental chemistry and physics. The controls available to the NMR spectroscopist or imager are vast, allowing for everything from high level structural determination of proteins in solution to detailed contrast imaging of organs in-vivo. Unfortunately, the weak nuclear magnetic moment of the nucleus requires that a very large number of spins be present for an inductively detectable signal, making the use of magnetic resonance as a detection modality for microfluidic devices especially challenging. Here we present recent efforts to combat the inherent sensitivity limitation of magnetic resonance for lab-on-a-chip applications. Principles and examples of different approaches are presented that highlight the flexibility and advantages of this type of detection modality.

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Section: Remote Detectionmentioning

confidence: 99%

Magnetic resonance detection: spectroscopy and imaging of lab-on-a-chip

Harel

2009

Lab Chip

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“…Furthermore, remote detection uniquely provides the possibility of obtaining the axial dispersion of the fluid as an additional experimental dimension by recording the time of flight (TOF) between encoding and detection of individual spin packets. Thereby, the encoded signal is read out in a time-dependent manner (13), showing how fluid spreads as it travels through the device. The NMR-pulse sequence for the acquisition of these dispersion-resolved images is based on phase-encoded imaging (18) in the encoding coil, and a stroboscopic signal-detection scheme is applied on the microcoil to read out the axial dispersion (Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Here we show profiles of microfluidic gas flow in capillaries and chip devices obtained by NMR in the remote-detection modality (11,12). Through the transient measurement of dispersion (13), NMR is well adaptable for noninvasive yet sensitive determination of the flow field and provides a potentially more powerful tool to profile flow in capillaries and miniaturized flow devices.…”

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confidence: 99%

Microfluidic gas-flow profiling using remote-detection NMR

Hilty

McDonnell

Granwehr

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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We have used nuclear magnetic resonance (NMR) to obtain spatially and temporally resolved profiles of gas flow in microfluidic devices. Remote detection of the NMR signal both overcomes the sensitivity limitation of NMR and enables time-of-flight measurement in addition to spatially resolved imaging. Thus, detailed insight is gained into the effects of flow, diffusion, and mixing in specific geometries. The ability for noninvasive measurement of microfluidic flow, without the introduction of foreign tracer particles, is unique to this approach and is important for the design and operation of microfluidic devices. Although here we demonstrate an application to gas flow, extension to liquids, which have higher density, is implicit.hyperpolarization ͉ xenon ͉ magnetic resonance imaging M iniaturized fluid-handling devices have attracted considerable interest recently in many areas of science (1). Such microfluidic chips perform a variety of functions ranging from analysis of biological macromolecules (2, 3) to catalysis of reactions and sensing in the gas phase (4,5). To enable precise fluid handling, accurate knowledge of the flow properties within these devices is important. Because of low Reynolds numbers, laminar flow is usually assumed. However, either by design or unintentionally, the flow characteristic in small channels is often altered (e.g., by surface interactions, viscous and diffusional effects, or electrical potentials). Therefore, its prediction is not always straightforward (6-8). Currently, most microfluidic flow measurements rely on optical detection of markers (9, 10), requiring the injection of tracers and transparent devices. Here we show profiles of microfluidic gas flow in capillaries and chip devices obtained by NMR in the remote-detection modality (11,12). Through the transient measurement of dispersion (13), NMR is well adaptable for noninvasive yet sensitive determination of the flow field and provides a potentially more powerful tool to profile flow in capillaries and miniaturized flow devices.NMR remote detection separates the encoding of NMR information from the detection of the actual signal. Information about a stationary object of interest is encoded into spin polarization of a mobile sensor by using radiofrequency (rf) pulses and field gradients. The spin sensor is then physically transferred to a different location for detection, which leads to a decisive enhancement of signal whenever geometrical constraints prevent the use of a sensitive NMR coil for detection directly at the sample site (11,12). In the present work, we studied gas flow in model microfluidic devices by using hyperpolarized 129 Xe as a spin-carrying nucleus (14). Experimental ProceduresImage information was encoded with an rf coil that completely encompassed the microfluidic device (Fig. 1). Such a coil arrangement ideally allows NMR-image information to be obtained from the entire microfluidic device. For measuring flow, it provides a decisive advantage over localized detection, which is achievable, for example,...

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“…When the nuclear spins are spread out over a large volume, detection becomes less sensitive. For fluidic analytes, the spins can be concentrated in a detection region and the problem can be circumvented by remote detection (15)(16)(17): a sample is first prepolarized; then it enters an encoding region where large radio frequency coils that cover the whole sample area store spectroscopic or spatial information as nuclear magnetization along the longitudinal axis; downstream the sample is concentrated and its magnetization is measured with improved filling factor.…”

Section: Agnetic Resonance Imaging (Mri) Is Used In Fields Asmentioning

confidence: 99%

Magnetic resonance imaging with an optical atomic magnetometer

Yashchuk

Donaldson

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

156

140

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We report an approach for the detection of magnetic resonance imaging without superconducting magnets and cryogenics: optical atomic magnetometry. This technique possesses a high sensitivity independent of the strength of the static magnetic field, extending the applicability of magnetic resonance imaging to low magnetic fields and eliminating imaging artifacts associated with high fields. By coupling with a remote-detection scheme, thereby improving the filling factor of the sample, we obtained time-resolved flow images of water with a temporal resolution of 0.1 s and spatial resolutions of 1.6 mm perpendicular to the flow and 4.5 mm along the flow. Potentially inexpensive, compact, and mobile, our technique provides a viable alternative for MRI detection with substantially enhanced sensitivity and time resolution for various situations where traditional MRI is not optimal.low field ͉ remote detection

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Time-of-Flight Flow Imaging Using NMR Remote Detection

Cited by 71 publications

References 27 publications

Magnetic resonance detection: spectroscopy and imaging of lab-on-a-chip

Magnetic resonance detection: spectroscopy and imaging of lab-on-a-chip

Microfluidic gas-flow profiling using remote-detection NMR

Magnetic resonance imaging with an optical atomic magnetometer

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