Large production system for hyperpolarized 129Xe for human lung imaging studies.
OBJECTIVE
Hyperpolarized gases such as (129)Xe and (3)He have high potential as imaging agents for functional lung magnetic resonance imaging (MRI). We present new technology offering (129)Xe production rates with order-of-magnitude improvement over existing systems, to liter per hour at 50% polarization. Human lung imaging studies with xenon, initially limited by the modest quantity and quality of hyperpolarized gas available, can now be performed with multiliter quantities several times daily.


METHODS
The polarizer is a continuous-flow system capable of producing large quantities of highly-polarized (129)Xe through rubidium spin-exchange optical pumping. The low-pressure, high-velocity operating regime takes advantage of the enhancement in the spin exchange rate provided by van der Waals molecules dominating the atomic interactions. The long polarizing column moves the flow of the gas opposite to the laser direction, allowing efficient extraction of the laser light. Separate sections of the system assure full rubidium vapor saturation and removal.


RESULTS
The system is capable of producing 64% polarization at 0.3 L/hour Xe production rate. Increasing xenon flow reduces output polarization. Xenon polarization was studied as a function of different system operating parameters. A novel xenon trapping design was demonstrated to allow full recovery of the xenon polarization after the freeze-thaw cycle. Delivery methods of the gas to an offsite MRI facility were demonstrated in both frozen and gas states.


CONCLUSIONS
We demonstrated a new concept for producing large quantities of highly polarized xenon. The system is operating in an MRI facility producing liters of hyperpolarized gas for human lung imaging studies.
Hersman
F William
FW
Department of Physics, University of New Hampshire, 131 Main Street, Nesmith Hall, Durham, NH 03824, USA. herman@unh.edu
Ruset
Iulian C
IC
Ketel
Stephen
S
Muradian
Iga
I
Covrig
Silviu D
SD
Distelbrink
Jan
J
Porter
Walter
W
Watt
David
D
Ketel
Jeffrey
J
Brackett
John
J
Hope
Aaron
A
Patz
Samuel
S
D004867:Equipment Design; D006801:Humans; D007834:Lasers; D008171:Lung Diseases / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging; D055095:Optics and Photonics; D014979:Xenon Isotopes / Q000737:chemistry*
D014979:Xenon Isotopes