compareStructures: Compare Axially-Defined Three-Dimensional Structures

In RadOnc: Analytical Tools for Radiation Oncology

Compare Axially-Defined Three-Dimensional Structures

Description

Three-dimensional structural comparison of a structure.list composed of two or more structure3D objects.

Usage

compareStructures(structures, method = NULL,
	hausdorff.method = NULL, verbose = TRUE, plot = TRUE, pixels = 100)

Arguments

structures	An object of class structure.list containing two or more structure3D objects.
method	One of "axial", "surface", "hausdorff", "DSC", or "EMD" specifying the comparison between structures. For the "axial" method (default), the volumetric region of comparison is divided into discrete evenly-spaced voxels and the degree of overlap is measured across each voxel in axial cross-sections. For the "surface" method, overlap is calculated for each point on each structure's surface. For the "hausdorff" method, Hausdorff distances are calculated for each pairwise combination of structures as the distance between two point clouds. The "EMD" method is currently not currently supported (in development), but will return a modified earth mover's distance between two structures, accounting for radiation dose.
hausdorff.method	One of "mean", "median", "95", or "absolute", specifying the method to use for Hausdorff distance measurement when method = "hausdorff". The "absolute" Hausdorff distance yields the maximum distance required to connect any point from one point cloud to its closest neighbor in the other. This metric is highly subject to outliers, thus an aggregate metric is implemented by selecting the average ("mean", equivalent to the mean surface distance) or median ("median") distance required to connect all points in one point cloud to their closest neighboring points in the other. When value is "95", the 95-percentile Hausdorff distance is calculated. Note that the Hausdorff distance between two completely superimposable point clouds is zero. This parameter is ignored for other values of method.
verbose	Logical value (default is TRUE) indicating whether or not to print status updates to the active command line interface or workspace.
plot	Logical value (default is TRUE) indicating whether or not to display graphical comparison of structures. This parameter is only relevant when method = "axial", as it is otherwise ignored.
pixels	Integer value (default is 100) specifying the number of pixels in the x- and y-directions used for comparative calculations when method = "axial".

Value

When method = "hausdorff", the function returns a NxN matrix of pairwise Hausdorff distances, where N is the number of structures in structures. When method = "axial" or method = "surface", the function returns a Mx(N+3) dimensional matrix representing a list of M points in three-dimensional space and a table of values denoting whether each point is internal or external to each structure (note that the first three columns in the matrix represent the xyz coordinates for each point and values of 1 and 0 represent internal and external points, respectively).

Author(s)

Reid F. Thompson ([e-mail])

See Also

structure.list, structure3D

Examples

data("RadOnc")
compareStructures(teeth, method="DSC")
# teeth.compare <- compareStructures(teeth, method="axial", plot=TRUE)
# compareStructures(teeth, method="hausdorff", hausdorff.method="mean")

RadOnc documentation built on April 3, 2025, 7:23 p.m.