Apparatus and method for acoustic imaging using inverse scattering techniques
First Claim
1. A method of producing an image of an object from acoustic energy that has been transmitted through and scattered by the object, said image comprising a high and acoustic absorption at all points within the object, and said method comprising the steps of:
- electronically transmitting an electric signal at multiple frequencies and transducing said electric signal at each said frequency into acoustic energy propagated toward said object from a plurality of transducer transmitter positions;
electronically processing said electrical signal to determine from said transmitter positions an incident field corresponding to said propagated acoustic energy, said incident field being stored in the memory of a central processing unit (CPU) in the form of digitized electric signals;
detecting at a plurality of transducer receiver positions said acoustic energy transmitted through and scattered by said object;
electronically processing said detected acoustic energy so as to transform said detected energy into a plurality of digitized electric signals stored in said memory of said CPU and corresponding to a scattered field detected at said transducer receiver positions;
said CPU preparing an initial estimate of the scattering potential for said object and an initial estimate of the internal field of said object at each pixel of a display screen on which said acoustic image is to be displayed and storing each said estimate in said memory;
said CPU determining at each said frequency and storing in said memory a scattered field derived at said frequency from said initial estimates of the scattering potential and internal field, and thereafter comparing at said frequency said scattered field detected at said receiver positions to said scattered field determined by said CPU;
said CPU determining at each said frequency and storing in said memory a new estimate of said internal field at each said pixel derived from said incident field, the last estimate of the internal field at each said pixel, and the last estimate of said scattering potential at each said pixel, said new estimate of the internal field at said frequency comprising all orders of scattering;
said CPU determining and storing in said memory a new estimate of said scattering potential derived from said new estimate of said internal field and said scattered field detected at said receiver positions;
said CPU continuing to update the estimate for said internal field and scattering potential until said scattered field determined by said CPU approximates said scattered field detected at said receiver positions within a selected range of tolerance; and
said CPU thereafter using the determined scattering potential to reconstruct and store said image in said CPU memory.
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Abstract
An apparatus and method for reconstructing an acoustic image of an object using a central processing unit programmed to process data derived from acoustic energy that has been transmitted at multiple frequencies and scattered by the object. Electronic signals are propagated at multiple frequencies and transduced into acoustic energy waves which are propagated toward an object. Transducer receivers detect the acoustic energy waves after they have been scattered by the object and the detected acoustic energy waves are then electronically processed and input into a high-speed digital computer which may comprise a central processing unit and/or a central processing unit in combination with an array processor. Data is also prepared and input to the computer representing the incident field and the computer then reconstructs a high-quality image of the scanned object so as to produce an image having high spacial resolution and including actual internal viscous and elastic properties of the object through the use of new inverse scattering techniques used in the data processing steps.
207 Citations
38 Claims
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1. A method of producing an image of an object from acoustic energy that has been transmitted through and scattered by the object, said image comprising a high and acoustic absorption at all points within the object, and said method comprising the steps of:
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electronically transmitting an electric signal at multiple frequencies and transducing said electric signal at each said frequency into acoustic energy propagated toward said object from a plurality of transducer transmitter positions; electronically processing said electrical signal to determine from said transmitter positions an incident field corresponding to said propagated acoustic energy, said incident field being stored in the memory of a central processing unit (CPU) in the form of digitized electric signals; detecting at a plurality of transducer receiver positions said acoustic energy transmitted through and scattered by said object; electronically processing said detected acoustic energy so as to transform said detected energy into a plurality of digitized electric signals stored in said memory of said CPU and corresponding to a scattered field detected at said transducer receiver positions; said CPU preparing an initial estimate of the scattering potential for said object and an initial estimate of the internal field of said object at each pixel of a display screen on which said acoustic image is to be displayed and storing each said estimate in said memory; said CPU determining at each said frequency and storing in said memory a scattered field derived at said frequency from said initial estimates of the scattering potential and internal field, and thereafter comparing at said frequency said scattered field detected at said receiver positions to said scattered field determined by said CPU; said CPU determining at each said frequency and storing in said memory a new estimate of said internal field at each said pixel derived from said incident field, the last estimate of the internal field at each said pixel, and the last estimate of said scattering potential at each said pixel, said new estimate of the internal field at said frequency comprising all orders of scattering; said CPU determining and storing in said memory a new estimate of said scattering potential derived from said new estimate of said internal field and said scattered field detected at said receiver positions; said CPU continuing to update the estimate for said internal field and scattering potential until said scattered field determined by said CPU approximates said scattered field detected at said receiver positions within a selected range of tolerance; and said CPU thereafter using the determined scattering potential to reconstruct and store said image in said CPU memory. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of reconstructing an acoustic image of an object using a central processing unit (CPU) programmed to process data derived from acoustic energy that has been transmitted at multiple frequencies and scattered by said object, said method comprising the steps of:
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propagating multiple frequency acoustic energy waves toward said object from a plurality of transmitters positions; electronically storing a plurality of digitized electronic signals derived by said CPU from said propagated acoustic energy and said transmitter positions, said digitized electronic signals representing an incident field obtained at each said frequency detecting at a plurality of receivers multiple frequency acoustic energy waves scattered by said object; electronically storing a plurality of digitized electronic signals representing all orders of a scattered field obtained at each said frequency and derived by said CPU from the scattered acoustic energy waves detected at said receivers; said CPU determining (a) an estimate of an internal field at each said frequency and at each scattering point within said object, and (b) an estimate of a scattering potential characterized by density, acoustic speed and acoustic absorption at each said frequency and at each scattering point within said object, and said CPU electronically storing a plurality of digitized electronic signals representing said estimates of said internal field and said scattering potential; said CPU determining from said estimated internal field and scattering potential a predicted scattered field at all orders of scattering and at each said frequency, and said CPU comparing said predicted scattered field to said scattered field derived from the scattered acoustic energy waves detected at said receivers; said CPU updating said estimates of said internal field and said scattering potential until said comparison results in a predicted scattered field which approximates said scattered field derived from the scattered acoustic energy waves detected at said receivers within a selected range of tolerance; and said CPU thereafter reconstructing from said estimated scattering potential an acoustic image of said object, and outputting a visually perceptible display of said image. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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Specification