Coulter

Meet the Faculty

Robert Thomen

Robert Thomen, Ph.D.


Assistant Professor
Bioengineering
Radiology

Education

  • Ph.D. in Physics, Washington University in St Louis
  • M.S. in Physics, Creighton University
  • B.S. in Physics, Creighton University

Research Summary

Thomen's research interests involve hyperpolarized gas MRI of lungs and novel MRI pulse sequences. An MRI typically uses a very large magnetic field to produce a very slight magnetization of atomic nuclei (hydrogen nuclei in particular) which can be detected by the scanner using rf pulses and magnetic field gradients. The fraction of nuclei in a sample which participate in the nuclear magnetic resonance (NMR) phenomenon, and thus MRI, is called its polarization, and at field strengths used in conventional clinical MRI this fraction is on order of parts per million (ppm) - in other words only a few out of every million nuclei contribute to the detected signal of MRI. Hyperpolarization is a process whereby polarization is dramatically increased to a few percent (a 100,000x increase) using laser light rather than a strong magnet. This huge increase in signal is so high that a gas can be imaged in an MRI. Because hyperpolarized gases (3He and 129Xe) are noble gases, they are chemically inert and can be safely inhaled by a subject so the gas can be imaged as it fills the lungs. Subjects with healthy lungs show relatively homogeneous gas distribution whereas those with lung disease often show regions of defective ventilation. Thomen's studies investigate the nature of lung disease using these hyperpolarized gases and other MRI sequences which can quantify regional pulmonary structure and function.