Method and apparatus for determining the alignment of an object
First Claim
Patent Images
1. 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.
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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.
67 Citations
7 Claims
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1. A method for quantifying the similarity between two images, comprising:
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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. - View Dependent Claims (2, 3)
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4. An apparatus for on-line alignment and treatment of a patient with radiation, comprising:
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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. - View Dependent Claims (5, 6, 7)
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Specification