A new metric to measure shape differences in fMRI activity

Siddharth Khullar, Andrew M. Michael, Nicolle Correa, Tulay Adali, Nathan Cahill, Stefi A. Baum, Vince D. Calhoun

Research output: Chapter in Book/Report/Conference proceedingConference contribution


We present a novel shape metric for quantification of shape differences between the spatial components obtained from independent component analysis (ICA) of group functional magnetic resonance imaging (fMRI) data. This metric is utilized to measure the difference in shapes of the activation regions obtained from different subjects within a group (healthy controls or patients). The parameters comprising the metric are computed for each pixel on the outermost contour (edge) of an activation region for each slice. These parameters are in the form of (r, θ) pairs that may be interpreted as the length and orientation of a vector originating from the centroid of the activation region to the pixel belonging to the boundary contour. Using this information we extract three features that quantify the shape difference between the two shapes under observation. The reference and observation shapes may be selected in two ways: (a) activation maps from two different subjects or (b) mean activation map compared against subject-wise activations, as obtained from group ICA. We present different methods to visualize the shape differences, thus providing a tool to observe the spatial differences within a group or across groups. In addition to the above results, we also address a few special cases where two or more activation contours are present in a single slice and present potential solutions for accounting for these regions as special measures. Our results show that this metric has utility in creating a better understanding of the variability in brain activity among different groups of subjects performing the same task.

Original languageEnglish (US)
Title of host publicationMedical Imaging 2011
Subtitle of host publicationImage Processing
StatePublished - Jun 9 2011
Externally publishedYes
EventMedical Imaging 2011: Image Processing - Lake Buena Vista, FL, United States
Duration: Feb 14 2011Feb 16 2011

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


OtherMedical Imaging 2011: Image Processing
Country/TerritoryUnited States
CityLake Buena Vista, FL


  • fMRI
  • group ICA
  • shape metrics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging


Dive into the research topics of 'A new metric to measure shape differences in fMRI activity'. Together they form a unique fingerprint.

Cite this