Han Wen, Ph.D.
Laboratory of Imaging Physics
Building 10, Room B1D523
10 Center Drive
Bethesda, MD 20814
Whether through ultrasound, x-rays, or magnetic resonance imaging (MRI), the ability to peer noninvasively into the human body has been an enormous boon to medicine. New technological advances provide an expanding horizon of better diagnostics through imaging. Dr. Wen’s primary research focus is the development of biomedical imaging and microscopy technologies. He applies physics discoveries to engineer novel solutions to challenges in medical imaging.
Dr. Wen and his colleagues focus on improving the information available in x-ray images at much lower levels of radiation than currently applied. X-ray imaging is relatively inexpensive, robust, and adaptable to almost any environment (e.g. mobile imaging stations), but the use of ionizing radiation can pose health risks. Dr. Wen’s laboratory is developing phase-sensitive x-ray imaging to enrich the information from x-ray scans while reducing the doses to safer levels. Whereas conventional x-ray imaging technologies rely on the “shadow” left by x-rays that have been absorbed by high-density tissues in the body, phase-sensitive imaging detects and takes advantage of x-rays that have been bent and scattered. He and his colleagues tackled the question of how to detect the subtle x-ray bending and scattering accurately within the typical time and space of diagnostic imaging. They created solutions that allowed them to perform the first such phase-sensitive imaging studies in live animals. They discovered a basic physics effect that lead to highly sensitive imaging devices at low radiation doses.
Whereas the principles of phase-sensitive x-ray detection are similar to those already adopted for light microscopy, a key challenge lies in the much shorter wavelengths and penetrating power of x-rays. Dr. Wen and colleagues approach the challenge by creating suitable imaging methods from the basic physics level up. They discovered a universal moiré effect between transparent phase masks which allows a sensitive imaging method using only phase-shifting elements with compact sources and cameras. At the same time they work on nanofabrication to scale traditional optical components to the sizes required for manipulating x-ray beams with wavelengths of a fraction of an angstrom. Dr. Wen is working with collaborators including experts in nanofabrication at the National Institute of Standards and Technology to develop the necessary components. They created phase gratings with 200 - 400 nanometer intervals. Putting these components into the new imaging method allowed his team to measure the bending of an x-ray beam by biological specimens down to several nano radian angles at a fraction of clinical dose levels. Such sensitivity was only possible at much higher doses for x-ray beams of synchrotron facilities.
Dr. Wen also has a longstanding interest in MRI. He and his colleagues previously developed a protocol to measure the function of the myocardium at very high spatial resolution. This technology has since been licensed and used in clinical laboratories. The sensitivity of the technology has allowed his clinical collaborators to detect early signs of weakening myocardial function in patients with type II diabetes. Dr. Wen’s laboratory also worked on a technique to improve diffusion MRI to eliminate motion artifacts introduced by breathing and heartbeat. Diffusion MRI is being studied for its ability to detect edema or swelling of the heart muscle following an injury or heart attack. However, because diffusion MRI relies on microscopic Brownian motion of water molecules, the signal is obscured by large motions of the body. Dr. Wen and his colleagues have developed an image processing protocol that provides enhanced images of the liver and heart. They are now supporting the efforts of their collaborators in its clinical application and further study.
In addition to his interest in diagnostic applications, Dr. Wen is also interested in basic discovery research with broad potential. In the 1990s, he and his colleagues invented Hall-effect imaging and explored its 3D capabilities, an ultrasonic method for noninvasively sensing the passive electrical properties of tissues. This work opened a field of research now called magneto-acoustic imaging, which are actively pursued by several laboratories as technological advances have made it more feasible in application. He studied extensively the behavior of electromagnetic wave propagation in the human body in the context of high field MRI and contributed to our understanding of the benefit and challenges of high field MRI today.
Han Wen graduated from Peking University in Beijing with a B.S. in physics in 1989 and earned his Ph.D. in physics from the University of Maryland in 1994 through the CUSPEA Scholarship. He joined the NIH in 1995 as a staff fellow. He has been an Investigator since 1997 and a Senior Investigator since 2006. Dr. Wen has contributed to more than 60 papers and book chapters. He has served as reviewer and associate editor for numerous journals and was on the editorial board of Magnetic Resonance in Medicine from 2005 to 2011. He is also a member of the Optical Society of America. Some of his honors include National Heart, Lung and Blood Institute Director’s Award, the Orloff Science Award and Distinguished Service Award to the ISMRM Society as a Reviewer for MRM. Dr. Wen holds 5 patents for inventions and methods generated from his work.
Miao H, Chen L, Bennett EE, Adamo NM, Gomella AA, DeLuca AM, Patel A, Morgan NY, Wen H. Motionless phase stepping in X-ray phase contrast imaging with a compact source. Proc Natl Acad Sci U S A. 2013;110(48):19268-72.
Wen H, Bennett EE, Hegedus MM, Rapacchi S. Fourier X-ray scattering radiography yields bone structural information. Radiology. 2009;251(3):910-8.
Wen H, Bennett EE, Hegedus MM, Carroll SC. Spatial harmonic imaging of X-ray scattering--initial results. IEEE Trans Med Imaging. 2008;27(8):997-1002.
Wen H, Denison TJ, Singerman RW, Balaban RS. The intrinsic signal-to-noise ratio in human cardiac imaging at 1.5, 3, and 4 T. J Magn Reson. 1997;125(1):65-71.
Miao H, Panna A, Gomella AA, Bennett EE, Znati S, Chen L, Wen H. A Universal Moiré Effect and Application in X-Ray Phase-Contrast Imaging. Nat Phys. 2016;12:830-834.
Related Scientific Focus Areas
Biomedical Engineering and Biophysics
This page was last updated on September 18th, 2017