Random Walk Imaging

Methods & Software

Methods

isoRWI – Cell and tissue morphology

The microscopic structure of tissue is imprinted in how water molecules can move within different compartments. These movements determine size, shape, and orientation of cellular geometry and organization within the tissue, and can be measured with MRI. Conventional methods gives averaged information about size, shape, and orientation within a millimeter-size imaging voxel. Since cell size and tissue structures normally are within the micrometer range, current methods are not sensitive enough to map these structures. Random Walk Imaging have designed new types of MRI diffusion encoding, capable of giving the information on a micrometer-scale. Therefor, our methods of measuring structure have simple and intuitive relations to tissue properties such as average cell size, shape, and orientation, and variability of cell density.

exRWI – Cell membrane permeability

The cell membrane is an efficient water barrier towards its surroundings, but its permeability can be affected for different reasons, such as its chemical composition and presence of channels. Our exchange method is able to quantify the rate of exchange between microscopic tissue environments, such as the inside and outside of cells, based on water movement differences. This rate is affected by the properties of the cell membrane, and is thus possible to be converted to a quantitative measure of its permeability. The method has been applied in healthy brain and in brain tumors.

floRWI – Capillary flow

Water movements in tissue compartments and of that flowing in the capillary network display distinctly different patterns. Random Walk Imaging have designed a method to measure perfusion, which is able to quantify the density of blood capillaries, due to its variable sensitivity to water flow and movements. The perfusion method has been applied in healthy brain.

Software

How do I get access to these methods on my scanner?

First, contact your vendor representative/clinical scientist or contact us directly.
Second, contact groups with existing implementations and inquire about research collaborations.

Below is a list of sites that independently implemented our methods.

  • Universitätsklinikum Erlangen, Erlangen, Germany
    Prof. Frederik Laun
    ; structure (tensor encoding); Siemens
  • University of Lübeck, Lübeck, Germany
    Prof. Martin Koch; exchange (filter-exchange imaging); Bruker, Philips
  • King’s College London, London, UK
    Dr. Jana Hutter; structure (tensor encoding); Philips
  • Medical College of Wisconsin, Wisconsin, USA
    Dr. Matthew Budde; structure (tensor encoding); Bruker
  • Champalimaud Centre for the Unknown, Lisbon, Portugal
    Dr. Noam Shemesh; structure (tensor encoding); Bruker
  • University of Oslo, Oslo, Norway
    Dr. Ivan Maximov; structure (tensor encoding); Varian, Siemens
  • Technische Universität München, München, Germany
    Dr. Franz Schilling; exchange (filter-exchange imaging); Agilent, Bruker

Analysis tools associated with post-processing and parameter estimation and waveform optimisation, as well as example data, are available through GitHub (see links below).