Spectroscopic issues in optical polarization of 3He gas for Magnetic Resonance Imaging of human lungs

• Published in: The European physical journal. ST, Special topics Vol. 222; no. 9; pp. 2103 - 2118
• Main Authors: Dohnalik, T., Głowacz, B., Olejniczak, Z., Pałasz, T., Suchanek, M., Wojna, A.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.10.2013; EDP Sciences
• Subjects: Atomic; Biological and medical sciences; Classical and Continuum Physics; Condensed Matter Physics; Materials Science; Measurement Science and Instrumentation; Medical sciences; Molecular; Optical and Plasma Physics; Physics; Physics and Astronomy; Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects); Review; Technology. Biomaterials. Equipments. Material. Instrumentation; Ground State Atom; European Physical Journal Special Topic; Helium Plasma; Nuclear Polarization; Polarize Beam Splitter; Magnetic field effect; Human; Optical polarization; Pressure effect; Metastable state; Resonance frequency; Helium 3; Lung; Optical pumping; Nuclear magnetic resonance imaging
• ISSN: 1951-6355; 1951-6401
• DOI: 10.1140/epjst/e2013-01989-5

The Magnetic Resonance Imaging (MRI) of human lungs for diagnostic purposes became possible by using nuclear spin hyperpolarized noble gases, such as 3 He. One of the methods to polarize 3 He is the Metastability Exchange Optical Pumping (MEOP), which up to now has been performed at low pressure of about 1 mbar and in low magnetic field below 0.1 T (standard conditions). The equilibrium nuclear polarization can reach up to 80%, but it is dramatically reduced during the subsequent gas compression to the atmospheric pressure that is necessary for the lungs examination. Further polarization losses occur during the transportation of the gas to the hospital scanner. It was shown recently that up to 50% polarization can be obtained at elevated pressure exceeding 20 mbar, by using magnetic field higher than 0.1 T (nonstandard conditions). Therefore, following the construction of the low-field MEOP polarizer located in the lab, a dedicated portable unit was developed, which uses the magnetic field of the 1.5 T MR medical scanner and works in the continuous-flow regime. The first in Poland MRI images of human lungs in vivo were obtained on the upgraded to 3 He resonance frequency Siemens Sonata medical scanner. An evident improvement in the image quality was achieved when using the new technique. The paper shows how spectroscopic measurements of 3 He carried out in various experimental conditions led both to useful practical results and to significant progress in understanding fundamental processes taking place during MEOP.