Seed Growing for a 4D Array: Seed Growing for a 4D Array
Description
Seed growing algorithm to find voxels in a three-dimensional array
according to their correlation to a seed voxel. The correlation is
measured according to the fourth dimension of the array.Usage
extract.aif(img, x, y, z, thresh = 0.9)
Arguments
img
is the four-dimensional array of medical imaging data.
x,y,z
are the coordinates of the seed voxel.
thresh
is the minimum correlation for inclusion in the region.
Value
- coordis a matrix of the three-dimesional coordinates
$(x,y,z)$ for all voxels found by the algorithm.
- concis a matrix whose rows correspond to the voxels found by
the algorithm and whose columns are the fourth dimension from the
input array (e.g., contrast agent concentration time curve).
- maskis an array of boolean values, where only voxels included
by the algorithm are given a value greater than zero.
- coris an array that mimics the
mask, but contains the
estimated correlation coefficients for all voxels included by the
algorithm.
Details
Correlation coefficients are computed for every voxel in the input
array. A recursive algorithm is then used to grow the region of
interest (ROI) from the seed voxel in three dimensions. All
adjacent voxels, where the correlation exceeds the threshold, are
included.