Ultrasonic imaging system and method using linear cancellation

Details Ultrasonic imaging system and method using linear cancellation Ultrasonic imaging system and method using linear cancellation

1999-06-29

2001-02-20

Lateef, Marvin M. (Department: 3737)

Surgery

Diagnostic testing

Detecting nuclear, electromagnetic, or ultrasonic radiation

C600S447000

Reexamination Certificate

active

06190322

ABSTRACT:

TECHNICAL FIELD
The present invention is generally related to the field of ultrasonic imaging, and, more particularly, is related to a system and method for ultrasonic imaging using linear cancellation.
BACKGROUND OF THE INVENTION
Ultrasonic imaging systems hold the promise of picturing the inner workings of a particular medium such as a human body without invasive surgical procedures, etc. Generally, such systems generate ultrasonic pulses that propagate through the body or other medium and the various structures therein generate echoes that are detected by the ultrasonic system. These echoes are used to generate an image of the interior structure of the medium.
In some cases, the medium may exhibit a nonlinear response to the ultrasonic pulses. At times, it is desirable to isolate the non-linearity in the medium to generate images of the medium in question. Among the techniques that have been developed to isolate the non-linearities is harmonic imaging. In harmonic imaging, a narrowband ultrasonic pulse is transmitted into the medium and the echo signals received are filtered to isolate the second harmonic that is believed to contain primarily non-linear echo information. However, this approach provides poor spatial resolution because it is a narrowband technique.
Another approach is to use phase inversion techniques to cancel out linearities. According to this approach, a relatively wideband, ultrasonic pulse is first transmitted into the medium. Shortly thereafter, the same pulse with an inverted polarity is transmitted as well. The received echo signals are added to each other, and presumably any linearities are canceled. Unfortunately, this approach suffers due to its susceptibility to motion artifact that results in unsatisfactory imaging.
SUMMARY OF THE INVENTION
The present invention provides a system and method for generating an ultrasound echo signal with reduced linear components. In one embodiment, the present system comprises an excitation signal source configured to generate a first excitation signal and a second excitation signal, and a transducer coupled to the excitation signal source, the transducer being configured to emit a first asymmetric ultrasonic pulse in response to the first excitation signal and a second asymmetric ultrasonic pulse in response to the second excitation signal, the first and second asymmetric ultrasonic pulses being emitted into a medium. The system also entails a beamformer coupled to the transducer, the beamformer configured to generate a first echo signal and a second echo signal received by the transducer from the medium in response to the first and second asymmetric ultrasonic pulses, and an envelope detector coupled to the beamformer, the envelope detector configured to generate a first echo envelope from the first echo signal and a second echo envelope from the second echo signal. The present system also includes an acoustic line memory coupled to the envelope detector configured to store the first echo envelope, and an arithmetic junction coupled to the envelope detector, the arithmetic junction configured to subtract the first echo envelope from the second echo envelope, thereby generating a nonlinear echo signal.
The present invention can also be viewed as providing a method for generating a nonlinear ultrasound echo signal with reduced linear components. In this regard, the method can be broadly summarized by the following steps: consecutively generating a first asymmetric ultrasonic pulse and a second asymmetric ultrasonic pulse, the first and second asymmetric ultrasonic pulses being emitted into a medium, thereby generating a first and second echo signals, respectively; generating a first envelope signal from the first echo signal and a second envelope signal from the second echo signal; and performing a subtraction between the first envelope signal and the second envelope signal, thereby generating the nonlinear ultrasound echo signal.
Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional features and advantages be included herein within the scope of the present invention.


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“Optical And Acoustical Observations Of The Effects Of Ultrasound On Contrast Agents”, Dayton, et al.; IEEE vol. 46. No. 1, Jan. 1999.

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