Averaging of diffusion tensor imaging direction-encoded color maps for localizing substantia nigra

• Published in: Computers in biology and medicine Vol. 51; pp. 104 - 110
• Main Authors: Ellmore, Timothy M., Murphy, Sara M., Cruz, Katarina, Castriotta, Richard J., Schiess, Mya C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.08.2014; Elsevier Limited
• Subjects: Algorithms; Anisotropy; Basal ganglia; Brain Mapping - methods; Brain research; Diffusion; Diffusion tensor imaging; Diffusion Tensor Imaging - methods; Female; Humans; Image Interpretation, Computer-Assisted - methods; Internal Medicine; Male; Midbrain; NMR; Nuclear magnetic resonance; Other; Parkinson's disease; Red nucleus; Studies; Substantia nigra; Substantia Nigra - physiology; Basal ganglia; MRI; Substantia nigra; MNI; SNc; Midbrain; RGB; STN; Diffusion tensor imaging; fMRI; VOI; Red nucleus; DECM; ANOVA; SNr; DTI; FA; SN; RN; AFNI; magnetic resonance imaging; volume of interest; pars compacta; direction-encoded color map; analysis of variance; red, green, and blue; substantia nigra; red nucleus; pars reticulata; analysis of functional neuroimages; Montreal Neurological Institute; subthalamic nucleus; signal-to-noise ratio; diffusion tensor imaging; fractional anisotropy; functional magnetic resonance imaging
• ISSN: 0010-4825; 1879-0534; 1879-0534
• DOI: 10.1016/j.compbiomed.2014.05.004

Diffusion tensor imaging (DTI) is a form of MRI that has been used extensively to map in vivo the white matter architecture of the human brain. It is also used for mapping subcortical nuclei because of its general sensitivity to tissue orientation differences and effects of iron accumulation on the diffusion signal. While DTI provides excellent spatial resolution in individual subjects, a challenge is visualizing consistent patterns of diffusion orientation across subjects. Here we present a simple method for averaging direction-encoded color anisotropy maps in standard space, explore this technique for visualizing the substantia nigra (SN) in relation to other midbrain structures, and show with signal-to-noise analysis that averaging improves the direction-encoded color signature. SN is distinguished on averaged maps from neighboring structures, including red nucleus (RN) and cerebral crus, and is proximal to SN location from existing brain atlases and volume of interest (VOI) delineation on individual scans using two blinded raters. •A method for averaging diffusion direction-encoded color maps is presented.•Application in a large sample of healthy controls shows improved signal-to-noise.•Averaging in standard space helps distinguish substantia nigra from neighboring nuclei.•Substantia nigra on average maps agrees with atlas locations and individual raters.