extract: Seed Growing for a 4D Array
In dcemriS4: A Package for Medical Image Analysis (S4 implementation)

Description Usage Arguments Details Value Author(s)

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.

1	extract.aif(img, x, y, z, thresh = 0.9)

`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.

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.

`coord`	is a matrix of the three-dimesional coordinates (x,y,z) for all voxels found by the algorithm.
`conc`	is 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).
`mask`	is an array of boolean values, where only voxels included by the algorithm are given a value greater than zero.
`cor`	is an array that mimics the `mask`, but contains the estimated correlation coefficients for all voxels included by the algorithm.