Medical Imaging
Mission
The mission of the UNH Center for Xenon Imaging is the development of hyperpolarized gas science and technology for fundamental and applied research in the physical, chemical, or biomedical sciences; demonstration of associated technologies for the purpose of medical imaging, especially by adapting or extending MRI techniques; utilization of numerical modeling to achieve a greater understanding of the fundamental capabilities and limitations of the methods; the dissemination of associated skills, understanding, and knowledge, including the commercialization of useful products for widespread benefit; and the expansion of practitioners within the field through education and training.
History
In 1992, Professor Bill Hersman began a program of polarizing helium for fundamental nuclear physics experiments with beams from particle accelerators. In 1997 he began thinking about applying this expertise to medical imaging applications. At that time, the polarization of xenon posed a particularly challenging problem. Spin-exchange polarization proceeds as a two-step process: the laser polarizes the rubidium through direct absorption, then the rubidium polarizes the xenon. The problem was that the presence of significant quantities of xenon depolarised the rubidium faster than the laser could repolarize it. Only very small quantities of xenon could be polarized to high percentages. Furthermore, using the significant gas pressures that were required to absorb the laser light caused the transfer rate of polarization from rubidium to xenon to be slow.
Prof. Hersman imagined a new regime of operation and identified key technologies that could enable this new method to work. The method was to flow the gas opposite to the laser beam through a long polarization cell. This allowed high utilization of the laser light. This could also be accomplished at low pressure allowing faster spin-exchange rates and commensurately faster flow rates. The rubidium saturation, however, had to be accomplished in a separate area to achieve precise densities and prevent non-linear runaway conditions. Finally, the rubidium condensation had to be accomplished while it was still in the presence of the polarizing laser light, to avoid depolarization.
The NIH-NHLBI awarded R21 funding to investigate this new technology in 1998. Using that funding we were able to prototype several subsystems and complete two independent numerical simulation programs. Bridge support from UNH and subsequent NIH funding through the R15 AREA program (together with equipment loans from other projects) allowed us to demonstrate the gains in efficiency of this approach. In May of 2003 using 100 W laser power, the UNH group polarized at a rate of one STP liter/hour xenon as high as 50% polarization and as much as six times that flow rate at 25% polarization.. The synergistic benefit of all these refinements allow a factor-of-ten improvement in polarizer performance over other approaches.
Facilities
- Ultra-Low Field Imaging Laboratory...
- Xenon Polarization Laboratory...more...
- Xenon Diagnostics Laboratory...
- Helium Polarization Laboratory...
- Helium Cell-Preparation Laboratory...
- Laser Development Laboratory...
- Small Business Incubation Center...
- Computer Farm...
Collaborators
The Center for Xenon Imaging at UNH collaborates with outside researchers and institutions:
- Dr. Sam Patz of Brigham and Women's Hospital (BWH) has participated in our gas imaging studies at low-field and is PI on the Bioengineering Research Partnership (BRP) to image lungs at 0.2T
- Dr. Mirko Hrovat of Mirtech (Brockton, MA) has participated in our gas imaging studies at low-field, and continues this collaboration with ongoing imaging development work
- Dr. Ron Walsworth of the Smithsonian Center for Astrophysics (CFA) led the initial effort for ultra-low field imaging of physical samples and biological samples in-vitro, and ititiated the effort for low-field imaging on a human scale
- Dr. Ross Mair of the CFA participated in our gas imaging of humans at low-field, with particularly valuable expertise in pulse-sequence optimization and image reconstruction. The collaboration continues at 0.2T at the Brigham and Women's Hospital.
- Dr. Matt Rosen of the CFA participated in our gas imaging of humans at low-field. His development of a practical helium polarizer with student Leo Tsai was a key contribution.
- Dr. George Topulos of BWH provides medically relevant guidance in the development of our noble gas breathing protocol, and supervised the breathing of inert gases.
- Dr. Jim Butler of Harvard Medical School provides physiologically relevant guidance in the development of our noble gas imaging investigations, and will serve as Co-PI on our BRP.
- Dr. Jack Myers of the Wentworth-Douglass Hospital (Dover, New Hampshire) provides medically relevant guidance in the development of our imaging investigations, and supervised the breathing of inert gases.
- Dr. Robert Oot of Southern NH Regional Medical Center, Parkland Medical Center and NH Imaging Service will provide guidance to the research program from the perspective of a clinical radiologist, assist in networking to the NH medical community and infrastructure, and interpret hyperpolarized xenon images.
- Dr. Thad Walker of the University of Wisconsin led the characterization of hybrid spin-exchange physics using our polarized helium cell samples. Our collaboration with his group continues with their consulting on the development of diagnostics to characterize our xenon spin-exchange polarizer.
Funding
The UNH Center for Xenon Imaging is funded by the National Institutes of Health through the National Heart, Lung, and Blood Institute and the National Institute of Biomedical Imaging and Bioengineering. The Center enjoys a synergistic relationship with the UNH Nuclear Physics group which is funded by the US Department of Energy. The Center also receives funding directly from internal sources within UNH.
Active grants:
- 1 R01 EB002443-01 . . Optimization of Novel Hyperpolarized Xenon Production
- 1 R01 HL073632-01 . . Hyperpolarized Gas Imaging of Lung Structure and Function
Completed grants:
- 1 R15 HL67784-01 . . Low-field MRI of Human Lungs with Hyperpolarized Gas
- 9 R21 HL62335-01 . . Novel Gas Polarization Method for Hyperpolarized Xe MRI