Wenjin Zhou
Research

Wenjin Zhou

I have developed new computational approaches toward the virtual histology of white-matter microstructure and new visualization and interaction techniques for understanding white-matter anatomy using diffusion magnetic resonance imaging (diffusion MRI). Using these new computational approaches, we extract specific microstructural measures of the underlying tissue properties using clinically feasible acquisition in order to provide reliable and sensitive biomarkers for anatomical changes in the brain due to disease. The new visualization and interaction interfaces help brain scientists identify and segment white-matter tracts more confidently and efficiently forquantitative pathological analysis. I collaborate closely with neuropsychologists Stephen Correia at Butler Hospital and David Tate at Harvard Medical School.

Quantitative Microstructure Measurements: Virtual Histology

Motivation: Complex brain microstructure changes are observed in early stages of various neurological diseases. Traditional methods of analyzing these microstructures use histological procedures such as electron microscopy, but these are invasive and often introduce artifacts, and also cannot be used to analyze disease stages and monitor progression.

Goal: Replace this invasive histological process with a non-invasive in-vivo computational process in order to find reliable and sensitive biomarkers for disease-induced microstructure changes using diffusion MRI.

microstructure_histology

With my new computational approaches through analytical modeling and analysis, I was able to extract specific microstructural measures of the underlying tissue including axon sizes, distribution and volume fraction. I thus obviated some of the limitations of earlier work by (1) improving sensitivity to small axons (radius < 3 micrometer) that are more vulnerable to disease and studying the full range of axon sizes in the human brain, (2) providing more realistic model that takes into account axon radii variation, (3) making the approach applicable to low-gradient clinical scanners and whole-brain mapping by mathematically modeling the water diffusion using a new diffusion MRI protocol. My results have been presented at various peer-reviewed international conferences and my recent submission to NeuroImage is a complete validation study on the feasibility and reliability of these computational approaches. My future work in brain science will build more sophisticated computational models in order to extract other tissue compartments including neurons, glial cells and dendrites as well as microstructural properties of gray matter.

extraction_pipeline

results

Related Publications:

  • DoubleAx: estimating axonal properties using angular double-pulsed gradient-spin-echo MRI in tissue of unknown orientation. Wenjin Zhou, Matt G. Hal and David H. Laidlaw. NeuroImage , 2001. (In review)
  • Measurement of axon radii distribution in orientationally unknown tissue using angular double-pulsed gradient spin echo (double-PGSE) NMR. Wenjin Zhou and David H. Laidlaw. In International Society for Magnetic Resonance in Medicine - ISMRM , 19:3938, 2011. (Montreal, QC, Canada)
  • Inferring Microstructural Properties Using Angular Double Pulsed Gradient Spin Echo NMR in Orientationally Unknown Tissue. Wenjin Zhou, Matt G. Hall, and David H. Laidlaw. In computational Diffusion MRI (CDMRI) Workshop at International Conference on Medical Image Computing and Computer-Assisted Intervention - MICCAI, 2010. (Beijing, China)
  • Inferring Axon Properties with double-PGSE MRI using Analytical Water Diffusion Model. Wenjin Zhou and David H. Laidlaw. In International Society for Magnetic Resonance in Medicine - ISMRM, chosen for podium talk, 18:677, 2010. (Stockholm, Sweden)
  • An Analytical Model of Diffusion and Exchange of Water in White Matter from Diffusion-MRI and its Application in Measuring Axon Radii. Wenjin Zhou and David H. Laidlaw. In International Society for Magnetic Resonance in Medicine - ISMRM, chosen for podium talk, 17:263, 2009. (Hawaii, USA)

Qualitative Interactive Visualization

Motivation: Understand and identify the neuroanatomy and connectivity for pathological analysis.

I have developed visualization techniques for brain white-matter tracts to encode their spatial relationships based on similarity measures from diffusion MRI. I demonstrated the benefits of visualization in disentangling the complex neural tractography data and in helping brain scientists understand and identify the underlying neuroanatomy and its connectivity. My ACM SIGGRAPH 2006 BEST POSTER which won FIRST PLACE in the ACM student research competition demonstrated a smooth-perceptual coloring scheme to map similar tracts to similar colors in order to help the users visually identify meaningful anatomical structures without imposing a rigid segmentation. In later work in VIS 2007, I mapped this similarity measure into stripe texture patterns and improved the visualization of subtle differences within large white-matter structures.

coloring

We then study the design principles related to the TOI selection techniques to analyze their utility, usability, accuracy and reliability. Most clinical MRI studies to date have employed a TOI analysis. We develop taxonomy and design guidelines for the selection task as a framework for exploring and categorizing the design space of the techniques. Using these design guidelines, we implement two selection techniques to enhance user performance in TOI selection tasks. The 2D-sketching selection tool combines expers' neuroanatomy training on 2D anatomical planes of the brain model and provides the user a flexible interface for selecting and grouping TOI into bundles by drawing free-form lassos, rather than rigid boxes as in traditional methods. We illustrate the benefits of 3D stereo virtual reality (VR) with higher-input-bandwidth devices in TOI selection tasks with a new haptics-assisted 3D lasso-drawing interface. The 3D VR interface allow users to gain more confidence in identifying neural bundles, and avoids the problem of visual flattening of fiber structures. The navigation time for the TOI selection task, a key challenge in TOI selection tools, was greatly reduced with the higher-input-bandwidth device in the VR environment.

interface

Related Publications:

  • Quantitative diffusion tensor imaging tractography metrics are associated with cognitive performance among HIV-infected patients. David F. Tate, Jared Conley, Robert H. Paul, Kathryn Coop, Song Zhang, Wenjin Zhou, David H. Laidlaw, Lynn E. Taylor, Timothy Flanigan, Bradford Navia, Ronald Cohen and Karen Tashima. Brain Imaging and Behavior, 4:68-79, 2010.
  • Haptics-Assisted 3D Lasso Drawing for Tracts-of-interest Selection in DTI Visualization. Wenjin Zhou, Stephen Correia, and David H. Laidlaw. In IEEE Visualization Poster Compendium, 2008. (Columbus, OH, USA)
  • Evaluation of Design Features in Interactive 3D Tracts-of-interest Selection Tools in DTI. Wenjin Zhou, Stephen Correia, and David H. Laidlaw. In IEEE Visualization Poster Compendium, 2008. (Columbus, OH, USA)
  • Visualizing Spatial Relations Between 3D-DTI Integral Curves Using Texture Patterns, Doria Jianu, Wenjin Zhou, Cagatay Demiralp, and David H. Laidlaw, in IEEE Visualization Poster Compendium, 2007. (Sacramento, CA, USA)
  • Perceptual Coloring and 2D Sketching for Segmentation of Neural Pathways. Wenjin Zhou, Peter G. Sibley, Song Zhang, David F. Tate, and David H. Laidlaw, In SIGGRAPH Poster Session, 2006. (Boston, MA, USA)