Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-03-11
2001-01-09
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06171245
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to ultrasound imaging in general, and in particular to methods of imaging slowly moving blood flow using contrast agents.
BACKGROUND OF THE INVENTION
Many diseases in the human body can be detected by analyzing the flow of blood through tissue. For example, tumors are often characterized by tissue having little or no blood flowing into them.
One commonly used technique to analyze the blood flow is ultrasound imaging. While this technique works well for producing images of fast moving blood flow, such as that found in arteries or major veins, it is difficult to produce images of blood moving in capillaries or small vessels because the echo signals produced by the individual blood cells are small in relation to the echoes produced by surrounding tissue and because the blood is moving too slow to accurately image using Doppler techniques.
To enhance the ability of slowly moving or stationary blood to produce strong echo signals, it is often advantageous to introduce a contrast agent into the patient. Typically, contrast agents are liquids containing small gas bubbles that are surrounded by a coating or shell. These bubbles produce stronger echo signals when subjected to ultrasound pulses than the blood cells do. While the use of a contrast agent increases the ability of an ultrasound machine to produce images of blood, it is still difficult to resolve blood in capillaries due to the small amount of contrast agent present at a particular location in the body. In addition, the current techniques for detecting the contrast agent are sensitive to motion artifacts caused by movement of the body or of the ultrasound probe.
Given the above shortcomings in the art, there is a need for a new ultrasound imaging mode that can accurately capture images of slowly moving blood flow or stationary blood.
SUMMARY OF THE INVENTION
The present invention is a technique for producing ultrasound images of slowly moving blood flow or stationary blood by isolating echo signals produced by a contrast agent from those produced by surrounding tissue. To produce an ultrasound image, a series or ensemble of ultrasound pulses are directed into the body along a single beam line. Echo signals created in response to each of the pulses are received and analyzed to separate those echo signals produced by the contrast agent from those produced by surrounding tissue.
To separate the echo signals, the echo signals are preferably analyzed for characteristic changes in their amplitude or centroid frequency. An image is then created wherein that portion of the body that produces the echo signals exhibiting the expected changes are highlighted while those areas of the body that produce substantially constant echo signals are not.
The present invention allows blood flow to be imaged in a manner that is less sensitive to tissue or probe movement.
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Lazenby John
Wilkening Wilko
Jaworski Francis J.
Siemens Medical Systems Inc.
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