@article{5676c2cad01a4721893c3d3f77490722,
title = "A compact SQUID-detected magnetic resonance imaging system under microtesla field in a magnetically unshielded environment",
abstract = "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.",
author = "Chen, {Hsin Hsien} and Yang, {Hong Chang} and Horng, {Herng Er} and Liao, {Shu Hsien} and Shieh Yueh and Wang, {Li Min}",
note = "Funding Information: This work was supported by the National Science Council of Taiwan under Grant No. NSC99-2112-M-002-017-MY3 and No. NSC100-2120-M-002-015. FIG. 1. (Color online) (a) Schematic of a high-T c SQUID-based NMR/MRI system in a magnetically shielded room, (b) aluminum shielded box. FIG. 2. (Color online) Sequences used in NMR detection for water phantoms. Time dependence of (a) measuring field B o,z , (b) pre-polarization field B p,y with a duration time T Bp of 6 s, (c) 90 o pulsed field B 1,x , (d) a compensation gradient field G z , and (e) the free induction decay NMR signal as a function of time t. FIG. 3. (Color online) (a) NMR spectrum of 10 ml tap water in single measurement and (b) its Fourier transform. FIG. 4. (Color online) (a) The SQUID-detected NMR signal after compensating the inhomogeneous field in magnetically unshielded environments and (b) its corresponding Fourier spectrum in one measurement. FIG. 5. (Color online) Sequences used in NMR detection for chili. Time dependence of (a) measuring field B o,z , (b) pre-polarization field B p,y , (c) 90 o and 180 o pulsed B 1,x , (d) gradient field G y , and (e) gradient fields G x and G z , and (f) detected FID and spin-echo signals as a function of time t. FIG. 6. (Color online) Selected slice of chili with images taken at (a) y = 6 cm and (b) y = 9 cm. FIG. 7. (Color online) SQUID-detected two-dimensional MRIs of a chili with slice selected at (a) y = 6 cm and (b) its corresponding image; SQUID-detected MRI with the slice selected at (c) at y = 9 cm, and (d) its corresponding images. ",
year = "2011",
month = nov,
day = "1",
doi = "10.1063/1.3656984",
language = "English",
volume = "110",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics Publising LLC",
number = "9",
}