VCTSELECT

VisionX V4

NAME

vctselect − extract simple intensity features from CT images

SYNOPSIS

vctselect [if=infile] [of=ofile] [th=] [lo=] [hi=] [-nd] [-n] [-a] [-v]

DESCRIPTION

vctselect accepts a CT integer image as input and outputs a byte binary-valued output image. The -nd option uses an automatic alogrithm to identify any "no-data" regions of the CT image. This algorithm examins the axial image corners to identify a conistent low intensity "no-data" pixel value that is less than -1000 HU. DIfferent manufactures use different values.

This utility may be used for simple image thresholding and other basic functions. With no options specified a zero valued byte image with the same dimesnions as the input image is created. If -n is specifed then the image output is inverted. If th= is specified then the CT image is thresholded at that value.

CONSTRAINTS

The no-data algortihm assumes a conventional axial slice data orientation. Only short integer images are accepted for input. Slope values other than 1.0 are currently not supported

OPTIONS

	if=		Input file, must be a short interger CT image preferabley with valid DICOM scale information.
	of=		Output image is always a byte binay-valued image
	th=		specify the threshold value for an image threshold operation. The thersold should be specified in Houndsfield units (HU) for valid DICOM images.
	lo=		set the low (false) value for the output image (default 0 )
	hi=		set the high (true) value for the output image (default 255)
	-n		negate the values of the output image
	-a		absolute thresholding, the threshold value is applied direclty to pixel values (the DICOM intercept value if available is ignored)
	-v		selects the verbose mode and prints some information about its action.

EXAMPLES

Compute a binary image of the no-data regions in a CT image

vctselect -nd if=im of=out

Threshold an image at -600 HU

vctselect th=-600 if=im of=out

Create a zero-valued byte image with the same dimensions
as a CT image

vctselect if=im of=out

AUTHOR

A. P. Reeves