High-definition fibre tractography is new tool for brain imaging
19 September 2012
A technique called high-definition fibre tractography (HDFT)
can trace the course of nerve fibre connections within the brain with
more accuracy. It has the potential to improve the accuracy of
neurosurgical planning and to advance scientific understanding of the
brain's structural and functional networks.
the technique is reported in the August issue of Neurosurgery,
official journal of the Congress of Neurological Surgeons.
In the new report, Dr Juan C Fernandez-Miranda and colleagues of
University of Pittsburgh describe and illustrate the use of the HDFT
to track the course of the nerve fibres that make up the white
matter of the brain. The researchers write, "Our HDFT approach
provides an accurate reconstruction of white matter fibre tracts
with unprecedented detail in both the normal and pathological human
Seeing white matter tracts in living brain
Dr Fernandez-Miranda and coauthors report on the development and
evaluation of the HDFT technique, including initial findings in
healthy people and patients with various brain lesions. The new
technique adds advanced digital processing and reconstruction
techniques to current methods of tractography — a method used to
trace the course of bundles of white matter fibres, or "tracts", in
Tractography using a technique called diffusion tensor imaging
(DTI) has been available for more than a decade. However, DTI has
some important limitations: it can't show the complex course of
white matter fibre tracts as they cross each other, and it can't
accurately show the starting point and ending points of white matter
tracts. The researchers call these the "crossing problem" and the
"termination problem," respectively.
Over the past three years, Dr. Fernandez-Miranda and colleagues
have been working on refining new fibre mapping techniques — such as
high-angular resolution diffusion imaging and diffusion spectrum
imaging — to study the structural connections of the brain.
They write, "In an attempt to more effectively solve the crossing
and termination problems, we have focused on optimizing these
methods to obtain what we refer to as HDFT."
Through a combination of imaging processing and reconstruction
and tractography methods, HDFT can track white matter fibre tracts
from their origin, through complex fibre crossings, to their
termination point, with resolution of one millimetre or less.
For brain researchers, HDFT provides an unprecedented level of
detail to solve both the crossing and termination problems.
Colour-coded images show the complex architecture of white matter
fibres, as they cross each other in complex patterns. The HDFT
images accurately replicate known features of the brain anatomy,
including the folds and grooves (gyri and sulci) of the brain and
the characteristic shape of brain structures.
To evaluate how the new technique might be used for surgical
planning, the researchers analyzed HDFT images obtained in patients
with cancers and other brain lesions. In patients with brain
cancers, HDFT clearly showed the disruption of brain tissue caused
by rapid tumour growth. Importantly, it was able to show the absence
of white matter fibres within the tumour itself in two types of
In patients with brain blood vessel malformations, HDFT provided
information likely to be useful in planning the safest approach to
surgery. The ability to differentiate displacement versus disruption
of fibres may become a critical factor in determining whether or not
damage caused by brain lesions is reversible.
The researchers emphasize that much more research will be needed
to refine the HDFT technique and to evaluate its scientific and
clinical uses. "From a clinical perspective, we show that accurate
structural connectivity studies in patients facilitate white matter
damage assessment, aid in understanding lesional patterns of white
matter structural damage, and allow innovative neurosurgical
applications," the researchers write. They also believe that
structural connections shown by HDFT will provide a useful
complement to efforts to map the functional connections of brain
networks, such as the Human Connectome Project.