Nuclear magnetic resonance in the nanoTesla range

Burghoff, M.; Hartwig, Stefan; Trahms, Lutz; Bernarding, Johannes

doi:10.1063/1.2006981

Cited by 96 publications

(67 citation statements)

References 11 publications

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“…To overcome the sensitivity loss of Faraday detection at low frequencies, ultrasensitive magnetometers based on the Superconducting QUantum Interference Device (SQUID) (16) are used to detect NMR and MRI signals (17)(18)(19)(20)(21)(22)(23)(24). Recently, SQUID-based MRI systems capable of acquiring in vivo images have appeared.…”

Section: Introductionmentioning

confidence: 99%

SQUID-Detected Magnetic Resonance Imaging in Microtesla Fields

Clarke

Hatridge

Mößle

2007

Annu. Rev. Biomed. Eng.

197

121

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The use of very low noise magnetometers based on Superconducting QUantum Interference Devices (SQUIDs) enables nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) in microtesla magnetic fields. An untuned superconducting flux transformer coupled to a SQUID achieves a magnetic field noise of 10−15 T Hz−1/2. The frequency-independent response of this magnetometer combined with prepolarization of the nuclear spins yields an NMR signal that is independent of the Larmor frequency ω0. An MRI system operating in a field of 132 μT, corresponding to a proton frequency of 5.6 kHz, achieves an in-plane resolution of 0.7 × 0.7 mm2 in phantoms. Measurements of the longitudinal relaxation time T1 in different concentrations of agarose gel over five decades of frequency reveal much greater T1-differentiation at fields below a few millitesla. Microtesla MRI has the potential to image tumors with substantially greater T1-weighted contrast than is achievable in high fields in the absence of a contrast agent.

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Section: Introductionmentioning

confidence: 99%

SQUID-Detected Magnetic Resonance Imaging in Microtesla Fields

Clarke

Hatridge

Mößle

2007

Annu. Rev. Biomed. Eng.

197

121

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“…The measurements were performed using the SQUID (superconducting quantum interference device) system described in Ref. [21]. Polarizing and detection fields were generated by two Helmholtz coils oriented perpendicular to each other.…”

Section: Experimental Implementationmentioning

confidence: 99%

“…[21] was applied. The method utilizes the increase of the sample magnetization with the duration of a polarizing field.…”

Section: Experimental Implementationmentioning

confidence: 99%

Improved Contrast in Ultra-Low-Field MRI with Time-Dependent Bipolar Prepolarizing Fields: Theory and NMR Demonstrations

Nieminen¹,

Voigt²,

Hartwig³

et al. 2013

Metrology and Measurement Systems

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The spin lattice (T 1 ) relaxation rates of materials depend on the strength of the external magnetic field in which the relaxation occurs. This T 1 dispersion has been suggested to offer a means to discriminate between healthy and cancerous tissue by performing magnetic resonance imaging (MRI) at low magnetic fields. In prepolarized ultra-low-field (ULF) MRI, spin precession is detected in fields of the order of 10-100 μT. To increase the signal strength, the sample is first magnetized with a relatively strong polarizing field. Typically, the polarizing field is kept constant during the polarization period. However, in ULF MRI, the polarizing field strength can be easily varied to produce a desired time course. This paper describes how a novel variation of the polarizing field strength and duration can optimize the contrast between two types of tissue having different T 1 relaxation dispersions. In addition, NMR experiments showing that the principle works in practice are presented. The described procedure may become a key component for a promising new approach of MRI at ultra-low fields.

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“…The ULF-SQUID-MRI system was constructed in an electromagnetic shield room of 2.2D×2.2W× 2.2H m 3 . The system consists of a polarizing magnet, HTS rf SQUID, SQUID driving electronics, input coil, Helmholtz-type measurement field coil, pick up coil, Maxwell gradient coil, two Golay gradient coils [6], delay pulse generator, function generators, power suppliers, mixer with filters, digital multi channel oscilloscope, and spectrum analyzer.…”

Section: System Configurationmentioning

confidence: 99%

“…The ultra low field (ULF) magnetic resonance imaging (MRI) systems using high sensitive and frequency independent low-T C SQUID sensors, which feature small-sized system, lower cost, higher frequency-resolution and shorter measurement time due to less averaging number with narrow bandwidth, have attracted attention in recent years [1][2][3]. The use of high-T C (HTS) SQUIDs for ULF MRI may enhance these advantages further due to much easier handling with cryoliquid or cryocooler.…”

Section: Introductionmentioning

confidence: 99%