Radiation imaging utilizing data reconstruction to provide transforms which accurately reflect wave propagation characteristics
First Claim
1. In a system for providing images derive from echo signals from a target in a region illuminated by multifrequency radiant energy, wherein the signals are transformed into data by two-dimensional (time (t) and position (u)) Fourier transformation into frequency domain (ω
- ) data and the spatial frequency domain (ku) data and then is inversely transformed into data from which images can be produced, the improvement comprising means utilizing phase of the signals in the form of a phase function to account for the receipt of said echo signals in the form of spherical wavefronts and reconstructing said frequency domain and spatial frequency domain data in response to said phase function, and means for operating upon said reconstructed data to provide inverse transforms containing said data from which images can be produced with high resolution.
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Abstract
A system for radiation imaging of an object in response to echo signals from a target area of the object, such as a region of the anatomy of a body. Data is obtained by time domain measurements at monostatic transducers which can be disposed in different locations. The data is processed by two-dimensional Fourier transformations reconstructed using a mapping function and which compensates for variation in the radiation pattern at the various detector locations by using a phase correction function which avoids the need for Fresnel or plane wave approximations.
60 Citations
5 Claims
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1. In a system for providing images derive from echo signals from a target in a region illuminated by multifrequency radiant energy, wherein the signals are transformed into data by two-dimensional (time (t) and position (u)) Fourier transformation into frequency domain (ω
- ) data and the spatial frequency domain (ku) data and then is inversely transformed into data from which images can be produced, the improvement comprising means utilizing phase of the signals in the form of a phase function to account for the receipt of said echo signals in the form of spherical wavefronts and reconstructing said frequency domain and spatial frequency domain data in response to said phase function, and means for operating upon said reconstructed data to provide inverse transforms containing said data from which images can be produced with high resolution.
- View Dependent Claims (2, 4, 5)
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3. In a system for providing images derived from echo signals from a target illuminated by multifrequency radiant energy, wherein the signals are transformed into data by two-dimensional (time (t) and position (u)) Fourier transformation into frequency domain (ω
- ) data and the spatial frequency domain (ku) data and then is inversely transformed into data from which images can be produced, the improvement comprising reconstructing means for translating said frequency and spatial frequency domain data into corresponding two-dimensional Fourier transform data in accordance with a phase function ##EQU9## where said signals are synthetic aperture data signals from transducer means at spatial location u1 to un and which are disposed at different distances yi along a first line perpendicular to a second line to the center of the target;
k=w/c is the wavenumber, c is the velocity of propagation in the medium surrounding the target, (Xi, Y1 +ui), i=1, . . . N are the coordinates of the i-th transmitting/receiving element (the transducers);
ui takes on values in a vertical line in the y direction along which the element is disposed at position ui, i=1, . . . N (synthesized aperture);
(X1, Y1) are the coordinates of the element at the center of the synthetic array (mid-point on the vertical line);
the target is center around the origin;
i.e., (0,0);
(X1 -x)2 +(Y1 +ui -y)2 is the distance from the reflector at the coordinates (x,y) in the target region to the element located at (X1, Y1 +ui); and
, wherein means are provided for mapping of said two-dimensional Fourier transform data into corresponding two-dimensional (Kx and Ky) data which is operated upon by means to provide inverse transforms from which images can be produced, where Kx =4K2 -ku2 and Ky =ku and ku is the spatial frequency domain data for each frequency of the multifrequency energy.
- ) data and the spatial frequency domain (ku) data and then is inversely transformed into data from which images can be produced, the improvement comprising reconstructing means for translating said frequency and spatial frequency domain data into corresponding two-dimensional Fourier transform data in accordance with a phase function ##EQU9## where said signals are synthetic aperture data signals from transducer means at spatial location u1 to un and which are disposed at different distances yi along a first line perpendicular to a second line to the center of the target;
Specification