Magnetic Resonance Imaging of Hyperpolarized $^{3}{\hbox {He}}$ Detected With a High-${\hbox {T}}_{\rm c}$ SQUID in Microtesla Magnetic Field at Laboratory Environment Fields

Abstract

Nuclear magnetic resonance and imaging (NMR/MRI) of optically pumped (OP) hyperpolarized <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{3}{\hbox {He}}$</tex></formula> were studied by using a high- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${\hbox {T}}_{\rm c}$</tex></formula> SQUID magnetometer device in microtesla magnetic fields. The OP cell was filled with a few milligrams of Rb metal, 0.0798 bar <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\hbox {N}}_{2}$</tex></formula> gas and 0.705 bar <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$^{3}{\hbox {He}}$</tex></formula> gas. The <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$^{3}{\hbox {He}}$</tex></formula> cell had been hyperpolarized at an optical pumping system for 5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim$</tex> </formula> 6 hours first; then it was moved to the SQUID-detected nuclear magnetic resonance and imaging system to measure. An appropriate <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm B}_{1}$</tex></formula> pulse level and time duration generated a 5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}$</tex> </formula> low flip angle of polarization. The free induction decay NMR signals were measured. The spin-lattice relaxation time <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$({\hbox {T}}_{1})$</tex></formula> of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$^{3}{\hbox {He}}$</tex></formula> was 4.7 hours. We improved the line width of NMR spectrum to 0.8 Hz by compensating the inhomogeneous gradient field of environment. The filtered back projection image of hyperpolarized <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{3}{\hbox {He}}$</tex></formula> could show a clear image in one shot. The SQUID-detected NMR/MRI would be a great interest for biological imaging.