title: Very-low-field MRI of laser polarized xenon-129.
abstract: We describe a homebuilt MRI system for imaging laser-polarized xenon-129 at a very low holding field of 2.2mT. A unique feature of this system was the use of Maxwell coils oriented at so-called "magic angles" to generate the transverse magnetic field gradients, which provided a simple alternative to Golay coils. We used this system to image a laser-polarized xenon-129 phantom with both a conventional gradient-echo and a fully phase-encoded pulse sequence. In other contexts, a fully phase-encoded acquisition, also known as single-point or constant-time imaging, has been used to enable distortion-free imaging of short-T2∗species. Here we used this technique to overcome imperfections associated with our homebuilt MRI system while also taking full advantage of the long T2∗available at very low field. Our results demonstrate that xenon-129 image quality can be dramatically improved at low field by combining a fully phase-encoded k-space acquisition with auxiliary measurements of system imperfections including B0field drift and gradient infidelity.
authors.affiliation: Department of Physics, University of Virginia, Charlottesville, VA 22904, USA.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Department of Physics, University of Virginia, Charlottesville, VA 22904, USA; Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Gordon D
authors.initials: GD
authors.lastname: Cates
authors.affiliation: Department of Physics, University of Virginia, Charlottesville, VA 22904, USA.
authors.forename: William A
authors.initials: WA
authors.lastname: Tobias
authors.affiliation: Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Mugler
authors.affiliation: Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA 22908, USA. Electronic address: Wilson.Miller@virginia.edu.
authors.forename: G Wilson
authors.initials: GW
authors.lastname: Miller
keywords: Gradient coils; Hyperpolarized xenon-129; Low field MRI; Pulse sequences