A continuous-flow, high-throughput, high-pressure parahydrogen converter for hyperpolarization in a clinical setting

TLDR: This article presents the safety concept, design and installation of a pH2 converter, operated in a clinical setting, and a dependence of line width on pH2 enrichment is observed.

Abstract: Pure parahydrogen (pH2) is the prerequisite for optimal pH2-based hyperpolarization experiments, promising approaches to access the hidden orders of magnitude of MR signals. pH2 production on-site in medical research centers is vital for the proliferation of these technologies in the life sciences. However, previously suggested designs do not meet our requirements for safety or production performance (flow rate, pressure or enrichment). In this article, we present the safety concept, design and installation of a pH2 converter, operated in a clinical setting. The apparatus produces a continuous flow of four standard liters per minute of ≈98% enriched pH2 at a pressure maximum of 50 bar. The entire production cycle, including cleaning and cooling to 25 K, takes less than 5 h, only ≈45 min of which are required for actual pH2 conversion. A fast and simple quantification procedure is described. The lifetimes of pH2 in a glass vial and aluminum storage cylinder are measured to be T1C(glass vial) = 822 ± 29 min and T1C(Al cylinder) = 129 ± 36 days, thus providing sufficiently long storage intervals and allowing the application of pH2 on demand. A dependence of line width on pH2 enrichment is observed. As examples, 1H hyperpolarization of pyridine and 13C hyperpolarization of hydroxyethylpropionate are presented. Copyright © 2012 John Wiley & Sons, Ltd.