After conception and implementation of any new medical image processing
algorithm, validation is an important step to ensure that the procedure
fulfills all requirements set forth at the initial design stage.
Although the algorithm must be evaluated on real data, a comprehensive
validation requires the additional use of simulated data since it is
impossible to establish ground truth with in-vivo data. Experiments with
simulated data permit controlled evaluation over a wide range of
conditions (e.g., different levels of noise, contrast, intensity
artefacts or geometric distortion). Such considerations have become
increasingly important with the rapid growth of neuroimaging, i.e.,
computational analysis of brain structure and function using brain
scanning methods such as PET and MRI.
Since simple objects such as ellipsoids or parallelepipedes do not
reflect the complexity of natural brain anatomy, we present the design
and creation of a realistic, high resolution, digital, volumetric phantom
of the human brain. This 3D digital brain phantom is made up of ten
volumetric data sets that define the spatial distribution for different
tissues (e.g., grey matter, white matter, muscle, skin, ...) where voxel
intensity is proportional to the fraction of tissue within the voxel.
The digital brain phantom be used to simulate tomographic images of the
head. Since the contribution of each tissue type to each voxel in the
brain phantom is known, it can be used as the gold standard to test
analysis algorithms such as classification procedures which seek to
identify the tissue ``type'' of each image voxel. Furthermore, since the
same anatomical phantom may be used to drive simulators for different
modalities, it is the ideal tool to test inter-modality registration
algorithms. The brain phantom and simulated MR images have been made
publicly available on the internet
(http://www.bic.mni.mcgill.ca/brainweb).
Key words: brain phantom, simulation, validation, testing, magnetic
resonance imaging, positron emission tomography.