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In this paper, a high-T c SQUID-based nuclear magnetic resonance (NMR) spectrometer was set up in National Taiwan University Hospital to discriminate liver tumor. In order to overcome the surrounding noise, a four-layer Al shielded box and a cylindrical magnetic shield were employed to avoid the electromagnetic noise in the coils part and the SQUID part, respectively. For NMR measurement, the larmor frequency is varying with time due to the variation of static field in hospital. Therefore, the time-domain frequency adjusted average method guided by a fluxgate was used to correct the frequency variation and average the NMR signal in the time domain. For tumor discrimination, the T 1 relaxation times of normal tissue and tumor tissue were demonstrated. Our high-T c SQUID-based low-field MRI system shows the feasibility for biomedical application in a clinic environment.

The fabrication processes for step-edge high- Tc superconducting-quantum-interference-device (SQUID) magnetometers have been developed. A magnetometer consists of three SQUIDs, which can be activated either individually or in series. Thus, the transfer function can be manipulated by activating a single SQUID or multiple SQUIDs in series. Furthermore, such a SQUID magnetometer is benefited by that if one of the three SQUIDs is broken, the other two SQUIDs are still workable. In addition to characterizing the SQUID magnetometer, the application of the SQUID magnetometer in the low-field nuclear magnetic resonance (NMR) has also been investigated. The results has shown a clear NMR signal of 4230 Hz for the water under 99.3 μT.

In this study, we report the spin-lattice relaxation rate of hepatocellular carcinoma (HCC) and normal liver tissue in rats using a high-T(c) superconducting quantum interference device (SQUID) based nuclear magnetic resonance (NMR) spectrometer. The resonance spectrometer used for discriminating liver tumors in rats via the difference in longitudinal relaxation time in low magnetic fields was set up in a compact and portable magnetic shielding box. The frequency-domain NMR signals of HCC tissues and normal liver tissues were analyzed to study their respective longitudinal relaxation rate T(1) (-1). The T(1) (-1) of liver tissues for ten normal rats and ten cancerous rats were investigated respectively. The averaged T(1) (-1) value of normal liver tissue was (6.41±0.66) s(-1), and the averaged T(1) (-1) value of cancerous tissue was (3.38±0.15) s(-1). The ratio of T(1) (-1) for normal liver tissues and cancerous liver tissues of the rats investigated is estimated to be 1.9. Since this significant statistical difference, the T(1) (-1) value can be used to distinguish the HCC tissues from normal liver tissues. This method of examining liver and tumor tissues has the advantages of being convenient, easy to operate, and stable.

This work reports an enhanced polarization and mechanisms in optically pumped (OP) hyperpolarized $^{3}\mathrm{He}$ in the presence of $^{4}\mathrm{He}$. The cells contain Rb metal, 60-torr ${\mathrm{N}}_{2}$, and different pressures of $^{3}\mathrm{He}$ and $^{4}\mathrm{He}$. In the absence of $^{4}\mathrm{He}$, the polarization of $^{3}\mathrm{He}$ increases monotonically from 4.5% to 8% when the pressure of $^{3}\mathrm{He}$ is increased from 300 to 1500 torr. In the presence of 1850-torr $^{4}\mathrm{He}$ gas, the polarization of $^{3}\mathrm{He}$ is enhanced from 7% to 30% for a cell containing 600-torr $^{3}\mathrm{He}$ and 60-torr ${\mathrm{N}}_{2}$. The wall relaxation factors $X$ for OP cells with and without buffering $^{4}\mathrm{He}$ gas were derived. It was found that the $^{4}\mathrm{He}$ gas confines the $^{3}\mathrm{He}$ atoms to a diffusion-limited region which effectively reduces the wall relaxation factor $X$. Mechanisms contributed to relaxation are addressed and discussed.

In this paper, we investigate the field-dependent T1-relaxation and T1-contrast imaging of ferrofluids using high-Tc superconducting quantum interference device (SQUID)-detected nuclear magnetic resonance and imaging in low magnetic fields, where T1 is the spin-lattice relaxation time. It was found that the 1/T1 of ferrofluids increases when the prepolarization field increases. We attribute this to the enhanced magnetic-field gradients generated from the induced magnetization that accelerates the T1-relaxation more in a high strength of fields in comparison to a low strength of fields. Using phantoms with different relaxation times, the T1-contrast images are demonstrated in low magnetic fields, which can be promising for discriminating tumors.

In this study, we present a compact and sensitive SQUID-detected nuclear magnetic resonance spectrometer and imager (NMR/MRI) using flux coupling in microtesla fields. The pre-polarization coil, measuring coil, pulsed coil, and gradient coils were set up inside a three-layer aluminum box while the SQUID-detector was shielded with a high-Tc superconducting vessel. A compensation field was applied to improve the field homogeneity in magnetically unshielded environments. The spin precession of protons was inductively coupled to the SQUID magnetometer via a resonant flux transformer. We obtained a signal-to-noise ratio of 120 in one measurement, a spectral resolution better than 1 Hz, and a spatial resolution of 1.3 mm in the images.

In this paper, an instrumentation of the Earth's field nuclear magnetic resonance (EFNMR) inside a laboratory is presented. A lock-in analysis (LIA) technique was proposed to enhance the signal-to-noise ratio (SNR). A SNR of 137.8 was achieved in a single measurement for 9 ml tap water, and the LIA technique significantly enhanced the SNR to 188 after a 10-average in a noisy laboratory environment. The proton-phosphorus coupling in trimethyl phosphate ((CH(3)O)(3)PO) with J-coupling J[H,F]=(10.99±0.013) Hz has been demonstrated. The LIA technique improves the SNR, and a 2.6-fold improvement in SNR over that of the frequency-adjusted averaging is achieved. To reduce the noise in EFNMR, it was suggested that the LIA technique and the first order gradient shim be used to achieve a subhertz linewidth.

In this work we present a sensitive J-coupling spectroscopy in one shot using high-Tc superconducting quantum interference devices and a flux transformer in microtesla fields. In the proposed NMR detection scheme the precession of proton spin was inductively coupled to the SQUID magnetometer. We enhanced the SNR signal and the spectral resolution significantly by applying a pre-polarization field of 0.045 T. In microtesla fields where chemical shifts are absent, we demonstrate proton–phosphate coupling J3[H,P] = (10.94 ± 0.08) Hz in trimethyl phosphate. The sensitive NMR spectrometer will be of great interest for diagnosis information of molecular structure and biological applications.

In this work, we present a design that improves signals produced by nuclear magnetic resonance (NMR) and magnetic resonance imaging by using optical pumping and a high-Tc superconducting quantum interference device (SQUID) magnetometer. In our design for a NMR detection system, a pickup coil is coupled to the spin procession of a H3e nucleus; the input coil is coupled to a high-Tc SQUID magnetometer; and the capacitor is connected in series to form a tank circuit resonating at the Larmor frequency of the H3e nucleus in the measuring field. A signal-to-noise ratio gain of 2.67 over a conventional Faraday detection coil was obtained with the high-Tc SQUID detection system in a measuring magnetic field equaling 0.1128 mT, at which the central frequency was 3.66 kHz for H3e nucleus. The improvement in the NMR signal for large-size, hyperpolarized H3e coupled to a high-Tc SQUID-based spectrometer in low magnetic fields at room temperature is significant compared to that without flux coupling. This result may b...

We applied prepolarization field and high-Tc superconducting quantum interference device (SQUID) detector to enhance nuclear magnetic resonance signal in a microtesla magnetic field. The minimum measuring magnetic field is 8.9μT at which the proton resonance frequency is 380Hz. The specificity instrumentation and the difficulty of using a high-Tc SQUID with prepolarization field were investigated. We applied gradient field to perform one-dimensional proton imaging in a microtesla magnetic field. Additionally, low field high-Tc SQUID-based NMR systems are promising in biomagnetic research due to its use, for example, in imaging with hyperpolarized noble gas.