Open-source, partially 3D-printed, high-pressure (50-bar) liquid-nitrogen-cooled parahydrogen generator

Abstract

Abstract. The signal of magnetic resonance imaging (MRI) can be enhanced by several orders of magnitude using hyperpolarization. In comparison to a broadly used dynamic nuclear polarization (DNP) technique that is already used in clinical trials, the parahydrogen (pH2)-based hyperpolarization approaches are less cost-intensive, are scalable, and offer high throughput. However, a pH2 generator is necessary. Available commercial pH2 generators are relatively expensive (EUR 10 000–150 000). To facilitate the spread of pH2-based hyperpolarization studies, here we provide the blueprints and 3D models as open-source for a low-cost (EUR <3000) 50-bar liquid-nitrogen-cooled pH2 generator.

Parahydrogen‐Induced Polarization of Amino Acids

“…25 K (c). [ 33 , 59 ] To use the NMR‐invisible para order, p H 2 is added either permanently to an unsaturated molecule (d,e), or brought into temporary contact through reversible exchange (f). Next, the spin order is converted spontaneously (free evolution) into observable polarization (pol) induced by RF pulses or variations of the magnetic field.…”

“…By cooling the H 2 ,the equilibriumiss hifted toward the para state and almost pure pH 2 is obtained at ca. 25 K(c) [33,59]. To use the NMR-invisible para order, pH 2 is added either permanently to an unsaturatedm olecule (d,e), or brought into temporaryc ontact through reversible exchange (f).…”

Symmetry Constraints on Spin Order Transfer in Parahydrogen-Induced Polarization (PHIP)

“…This is in strong contrast to non-symmetric molecules where the energy of spin flips is comparable to the strength of nuclear spin interactions. The large gap between H 2 rotational energies helps to enrich the pH 2 state at low temperatures and is responsible for its long lifetime [3,5].…”

“…Thus, pH 2 takes the lowest rotational energy state, which is symmetric, and oH 2 takes the next rotational energy state, which is asymmetric. The gap between the lowest two rotational energy levels, i.e., pH 2 and oH 2 , is significant (170.5 K) and can be used to enrich the para-state: 50% pH 2 is obtained by cooling H 2 to liquid nitrogen temperatures [3] and 99% at about 25 K (e.g., using a two-stage Helium cryo-cooler or liquid Helium) [4,5]. Because pH 2 and oH 2 can be separated, they are also referred to as nuclear spin isomers (NSIM).…”

Parawasserstoff‐induzierte Polarisation von Aminosäuren

“…B. mit Hochfrequenz(HF)-Pulsen [48] oder Va riationen des Magnetfelds (Feldzyklen) herbeigeführt werden. [40,[49][50][51] Während das 1 H-Signal fürd ie In-vitro-Analyse ausreichend sein mag, [52,53] erfordert die In-vivo-Anwendung normalerweise die Übertragung auf langsam relaxierende X-Kerne wie 13 Co der 15 N. [40,54,55] [33,59] Um die NMR-unsichtbare Para-Ordnung zu nutzen, wird pH 2 entweder permanentan ein ungesättigtes Molekülangelagert (d,e) oder durch reversiblen Austausch damit in temporären Kontakt gebracht (f). Als nächstes wird die Spinordnung in eine beobachtbare Polarisation (pol) umgewandelt, entweder durch spontane Zeitentwicklung (freie Evolution der Quantenzustände) oder durch gezielte Manipulationen (durch HF-Pulse oder Variationen des Magnetfelds).…”