UCLA Brain Mapping Center

Overview

The ICBM DTI-81 Atlas is a stereotaxic probabilistic white matter atlas that fuses DTI-based white matter information with an anatomical template (ICBM-152). This atlas is based on probabilistic tensor maps obtained from 81 normal subjects acquired under an initiative of the International Consortium of Brain Mapping (ICBM). The subjects were normal right-handed adults ranging from 18 to 59 years of age. A hand-segmented white matter parcellation map was created from this averaged map. This map can be used for automated white matter parcellation. The precision of the affine-based image normalization and automated parcellation was measured for a group of normal subjects using manually defined anatomical landmarks.

Methods

All studies were obtained on 1.5T MR units (Siemens). DT imaging data were acquired by using a single-shot, echo-planar imaging sequence with sensitivity encoding and a parallel imaging factor of 2.0. Transverse sections of 2.5 mm thickness were acquired parallel to the anterior commissure-posterior commissure line.

The raw diffusion-weighted images (DWIs) were first co-registered to one of the least diffusion-weighted images and corrected for subject motion with 6-mode rigid transformation with Automated Image Registgration (AIR). The average of all DWIs (aDWI) was calculated and used for a DTI-based anatomic image. For anatomical images to drive the normalization process, aDWIs were used. These images were normalized to the template (ICBM-152) using a 12-mode affine or 4th order polynomial non-linear transformation of AIR. The transformation matrix was then applied to the calculated diffusion tensor field.

In the white matter parcellation map (WMPM), deep white matter regions were manually segmented into various anatomic structures based on fiber orientation information. In the WMPM, the following white matter structures are identified and partitioned:

Tracts in the brainstem:

• Corticospinal tracts (CST)
• Medial lemniscus (ML)
• Medial longitudinal fasciculus (MLF)
• Inferior cerebellar peduncle (ICP)
• Middle cerebellar peduncle (MCP)
• Superior cerebellar peduncle (SCP)

Projection fibers:

• Corona radiata
• Anterior limb of internal capsule (ALIC)
• Posterior limb of internal capsule (PLIC)
• Retrolenticular part of the internal capsule (RLIC)
• Cerebral peduncle (CP)

Association fibers:

• Superior longitudinal fasciculus (SLF)
• Superior fronto-occipital fasciculus (SFO)
• Uncinate fasciculus (UNC)
• Inferior fronto-occipital fasciculus (IFO) / Uncinate fasciculus (UNC)
• Inferior fronto-occipital fasciculus (IFO) / Inferior longitudinal fasciculus (ILF)
• Sagittal Stratum (SS)
• External capsule (EC)
• Cingulum (CG)
• Fornix (FX) and Stria terminalis (ST)

Commissural fibers:

• Anterior commissure (AC)
• Corpus callosum (CC)
• Tapetum (TAP)

Additional information about this atlas is available at the following resources:
http://dx.doi.org/10.1016/j.neuroimage.2007.12.035
http://dx.doi.org/10.1016/j.neuroimage.2008.07.009
http://dx.doi.org/10.1006/nimg.1995.1012
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1088516/
http://www.ncbi.nlm.nih.gov/pubmed/11522763
http://www.ncbi.nlm.nih.gov/pubmed/17266101