Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-05-06
2001-08-28
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C128S916000
Reexamination Certificate
active
06280387
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to ultrasound imaging systems in general, and in particular to ultrasound systems for producing three-dimensional tissue/flow images.
BACKGROUND OF THE INVENTION
As the processing power of microprocessors and digital signal processors increases, it has now become possible to produce substantially real-time three-dimensional images of a patient's tissue and moving blood flow using non-invasive ultrasound. With a three-dimensional image, a physician or sonographer is able to more accurately detect diseases or abnormalities in the patient.
The traditional method of producing a three-dimensional image, involves obtaining ultrasound data representative of echo intensity and Doppler shift from a number of planes in the body. A series of images containing both tissue and flow data is created and stored in memory. A three-dimensional reconstruction algorithm then analyzes the combined data in the series of tissue/flow images to create a set three-dimensional data, called a volume, that represents the tissue and blood flow in the patient. Because the reconstruction algorithm is applied to both combined tissue and flow data, tissue structure or flow deep within the image is often obscured when a rendering or two-dimensional representation of the volume data is produced. While this artifact can be reduced by decreasing the opacity curves used to render the data, this has the effect of decreasing the dynamic range of the image whereby faint tissue or flow cannot be seen.
Other problems associated with prior techniques of producing three-dimensional ultrasound images include compensating for the movement of the ultrasound transducer between each of the two-dimensional images used to create volume. Such movement can result in a rendered image looking jagged or blotchy. In addition, there are no mechanisms to alert a sonographer to the quality of a three-dimensional image they are creating prior to its final completion. Therefore, a user must wait until a scan is completed before seeing the results, and must repeat the entire scan if there is a problem.
Given the above problems associated with traditional methods of producing three-dimensional tissue/flow images, there is a need for an ultrasound imaging system that can produce three-dimensional tissue/flow images wherein data is not lost as a result of the rendering process and the quality of resulting images is improved.
SUMMARY OF THE INVENTION
To improve the quality of three-dimensional ultrasound images, the present invention comprises a method of producing three-dimensional ultrasound images by creating a series of separate two-dimensional tissue and flow images. The data in each of the two-dimensional tissue and flow images are separately analyzed to produce a volume of the tissue data and a volume of the flow data. Separate renderings of the tissue volume and flow volume are created and combined in a predetermined or user selected proportion.
In addition, the present invention also improves the appearance of a combined tissue/flow rendering by locating and filtering the edge of a flow rendering prior to combining it with a tissue rendering in order to produce a smooth transition between the tissue and flow renderings.
The present invention also includes a reduced size memory to determine the particular red, green, and blue color values used to display the combined tissue/flow rendering. The memory maps different intensity values of the tissue rendering to the same red, green, and blue color values in a manner that is determined by a histogram of pixel intensity values for the tissue rendering.
A further aspect of the present invention includes a method of aligning a series of two-dimensional images. A comparison algorithm such as a correlation function or sum absolute difference compares the pixels of one image to the pixels of a subsequent image. From the comparison, an estimate of the relative position in two directions, &Dgr;X and &Dgr;Y can be determined. For simplicity, each image is assumed to be taken at equal distances apart in the &Dgr;Z direction.
The present invention also includes a visual display that allows a user to gauge where they should be in completing a scan. A user enters a rate at which they desire to move the ultrasound transducer in either mm/sec for a linear scan or degrees/sec for a rocked or rotational scan. In addition, a user enters the total length of the scan in cm or in degrees. The ultrasound system therefore computes the total duration of the scan and a visual display is created that shows how much time has passed since the beginning of a scan, compared to its computed duration.
In addition, the present invention creates and displays a partial image that is created from the tissue and flow volumes as they are being completed in order to alert a user to the quality of the three-dimensional data as it is being created. The partial image is shown simultaneously with the real-time two-dimensional images on a display screen. Finally, the present invention improves the selection of flow data during different portions of a cardiac cycle. To avoid selecting data from a two-dimensional flow image that may be misleading, the present invention selects the largest flow data from a series of two-dimensional images for use in creating a flow volume provided that the images are obtained from nearly the same position in the body.
REFERENCES:
patent: 5720291 (1998-02-01), Schwartz
patent: 5860924 (1999-01-01), Quistgaard
Czenszak Stephen P.
Deforge Christian
Liu Dong-Chyuan
Robinson Craig
Sutcliffe Patrick
Imam Ali M.
Lateef Marvin M.
Siemens Medical Systems Inc.
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