3He spin exchange cells for magnetic resonance imaging

R. E. Jacob, S. W. Morgan, B. Saam

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

We present a protocol for the consistent fabrication of glass cells to provide hyperpolarized (HP) 3He for pulmonary magnetic resonance imaging. The method for producing HP 3He is spin-exchange optical pumping. The valved cells must hold of order 1 atmṡL of gas at up to 15 atm pressure. Because characteristic spin-exchange times are several hours, the longitudinal nuclear relaxation time T 1 for 3He must be several tens of hours and robust with respect to repeated refilling and repolarization. Collisions with the cell wall are a significant and often dominant cause of relaxation. Consistent control of wall relaxation through cell fabrication procedures has historically proven difficult. With the help of the discovery of an important mechanism for wall relaxation that involves magnetic surface sites in the glass, and with the further confirmation of the importance of Rb metal to long wall-relaxation times, we have developed a successful protocol for fabrication of 3He spin exchange cells from inexpensive and easily worked borosilicate (Pyrex) glass. The cells are prepared under vacuum using a high-vacuum oil-free turbomolecular pumping station, and they are sealed off under vacuum after ≥100 mg of distilled Rb metal is driven in. Filling of cells with the requisite 3He-N 2 mixture is done on an entirely separate gas-handling system. Our cells can be refilled and the gas repolarized indefinitely with no significant change in their wall properties. Relaxation data are presented for about 30 cells; the majority of these reach a "40/40" benchmark: T 1>40 h, and 3He polarizations reach or exceed 40%. Typical polarization times range from 12 to 20 h; 20% polarization can be achieved in 3-5 h.

Original languageEnglish (US)
Pages (from-to)1588-1597
Number of pages10
JournalJournal of Applied Physics
Volume92
Issue number3
DOIs
StatePublished - Aug 1 2002
Externally publishedYes

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