Method and apparatus for determining the alignment of an object
AssigneeBoard of Regents, The University of Texas System
InventorArthur L. Boyer
Life of this patent
Estimating the term…
Abstract
A method and apparatus are provided for quickly determining misalignment between two images. Patient misalignment calculations can performed on-line using Fourier correlation analysis to compare the location of a portal field of radiation with a previously stored portal reference field. Fourier comparisons are done in both hardware and software which rapidly computes misalignment of a patient relative to the portal field and can also rapidly reposition the patient with respect to that field.
Claims7
A method for quantifying the similarity between two images, comprising:
- providing a portal field of view;
- positioning a portion of an object within said portal field of view;
- radiating said object to create a portal image corresponding to said portal field of view with respect to said object;
- generating an FFT array of the image by fast Fourier transforming said portal image;
- performing a Fourier correlation of said FFT array with a previously stored reference array to yield a correlation array;
- preparing an inverse FFT of said correlation array;
- calculating a universal scale as a function of said inverse FFT;
- setting alignment tolerances using said universal scale;
- comparing said alignment tolerances with the normalized Fourier correlation of each said array with a previously stored reference array to determine an alignment criteria between each said image array and said reference array;
- and
- repositioning said object with respect to said portal image if said alignment criteria exceeds said alignment tolerances.
An apparatus for on-line alignment and treatment of a patient with radiation, comprising:
- means for emitting collimated radiation;
- a detector aligned to receive said collimated radiation after having passed through said patient, and to produce signals indicative of said received radiation;
- means for storing said signals in the form of a portal image;
- means for Fourier converting said portal image into an FFT image array;
- a memory device coupled to said Fourier converting means and adapted to stored a Fourier converted reference array;
- an array processor means connected to the output of said Fourier converting means for correlating said FFT image array and said reference array to produce a correlation array, for calculating an inverse FFT of said correlation array, for calculating a universal scale as a function of said inverse FFT to measure a degree of patient alignment, and for comparing alignment criteria with predetermined alignment tolerances on the universal scale;
- and
- means for repositioning said patient with respect to said radiation portal in response to input from said array processor.
Dependencies are inferred from the claim text.