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Han Wen, Ph.D.

Laboratory of Imaging Physics

Background

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 is a reviewer 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 International Society of Magnetic Resonance in Medicine. Dr. Wen holds 5 patents for inventions and methods generated from his work.

Research Interests

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. Nevertheless, currently available diagnostics suffer from several limiting factors. Dr. Wen’s primary research focus is the development of biomedical imaging and microscopy technologies. He applies his training in physics 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. military field hospitals), but the use of ionizing radiation can pose health risks. In the last decade, the number of computed tomography (CT) x-ray scans ordered yearly has nearly doubled, and there is a measurable increase in the risk of cancer associated with CT scans. Dr. Wen’s laboratory is developing phase-sensitive x-ray imaging to achieve the same image quality but at safer doses. 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 described a way to detect x-ray bending and scattering all in a single exposure, which allowed them to perform the first such phase-sensitive imaging studies in live animals.

Whereas the principles of phase-sensitive x-ray detection are similar to those already adopted for light microscopy, a key challenge lies in the design of the instrument, which relies heavily on nanofabrication to scale traditional optical components to the sizes required for manipulating much tinier electromagnetic wavelengths; such components would be used to split 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, and they have recently created absorption gratings with 200 nanometer intervals over centimeter areas, several-fold smaller than current designs.

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 explored the use of three-dimensional Hall-effect imaging, an ultrasonic method for noninvasively mapping the passive electrical properties of tissues. This research has recently been adopted for use 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. Dr. Wen is now exploring ways to develop very high resolution of x-ray imaging for use by biomedical researchers. His laboratory is currently working on a very general purpose technique to enhance the biological information in x-ray microscopy and achieve a 10-fold improvement in resolution over conventional light microscopes.

Selected Publications

Single-shot x-ray differential phase-contrast and diffraction imaging using two-dimensional transmission gratings. Wen HH, Bennett EE, Kopace R, Stein AF, Pai V. Optics Letters 2010; 35(12):1932-1934. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3091831/

Adaptive postprocessing techniques for myocardial tissue tracking with displacement-encoded MRI. Wen H, Marsolo KA, Bennett E, Kutten KS, Lewis RP, Epstein ND, Plehn JF, and Croisille P. Radiology 2008; 246:229-240.http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2881596/

Spatial harmonic imaging of x-ray scattering - initial results. Wen H, Bennett E, Hegedus MM, Carroll SC. IEEE Transactions on Medical Imaging 2008; 27(8):997-1002. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2882966/ 

Hall effect imaging. Wen H, Shah J, Balaban RS. IEEE Transactions on Biomedical Engineering 1998; 45(1):119-124. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2909135

The intrinsic signal-to-noise ratio in human cardiac imaging at 1.5, 3, and 4 T. Wen H, Denison TJ, Singerman RW, Balaban RS. Journal of Magnetic Resonance 1997; 125(1):65-71. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2896425

Han Wen's Full List of Publications