Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
1999-02-09
2001-08-21
Chapman, John E. (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
C600S447000
Reexamination Certificate
active
06276211
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of imaging in general and more particularly to ultrasound imaging.
BACKGROUND OF THE INVENTION
One of the challenges in generating Three Dimensional (3D) ultrasound images may be the high data acquisition rate needed to scan tissue at a desired rate (such as 22 scans per second (sps)). The data acquisition rate may be a function of the size of the volume scanned, including depth, and the desired frame rate. For example, the data acquisition rate of a 3D ultrasound imaging system that performs 22 sps may need to increase as the size of the volume scanned increases. It is known to increase the data acquisition rate of 3D ultrasound imaging systems by using parallel receive processing. Parallel receive processing for a conventional 3D ultrasound imaging system is discussed in U.S. Pat. No. 4,694,434 entitled “Three-Dimensional Imaging System” to von Ramm and Smith which is incorporated herein by reference.
As shown in
FIG. 1
, a volume
100
may be scanned by steering ultrasound beams
115
into the volume
100
over an azimuth angle
110
and an elevation angle
120
using a two dimensional (2D) array of ultrasound transducer elements
130
. For example, the volume
100
may be scanned by steering 256 ultrasound beams into the volume
100
(16 transmit ultrasound beams through an azimuth angle of 65 degrees combined with 16 transmit ultrasound beams through an elevation angle of 65 degrees). The 256 ultrasound beams may be processed using parallel receive processing to form 4096 ultrasound scan lines (16 ultrasound scan lines formed for each transmit ultrasound beam transmitted). Accordingly, parallel receive processing may be used to increase the data acquisition rate by a factor of 16. However, increasing the data acquisition rate further using parallel receive processing may be prohibitively expensive to implement and may adversely affect the quality of images generated by conventional 3D ultrasound imaging systems.
The ultrasound scan lines may be used to provide a three dimensional (3D) data set that represents the volume
100
. Conventionally, the 3D data set may be manipulated by a user to view selected portions of the volume. For example, the user may select slices of the volume for viewing. Accordingly, the 3D data set may be accessed to provide the data which corresponds to the selected slices of the volume
100
which is then displayed.
As described in U.S. Pat. No. 5,546,807 entitled “High Speed Volumetric Ultrasound Imaging System” to Oxaal et al., which is incorporated herein by reference, a volume is scanned to provide a representative 3D data set which is stored in a memory. Subsequently, slices of the volume
100
may be selected by the user. The data which corresponds to the selected slices of the volume
100
is retrieved from the memory and displayed. The selected slices may be B-mode (B) slices, Constant Depth (C) slices, and Inclined (I) slices as shown in
FIGS. 2-4
respectively.
FIGS. 2-4
illustrate slices of the volume
100
selected for viewing as described in Oxaal et al. As shown in
FIG. 2
, the volume
100
is scanned to a range
205
and B slices
200
,
210
are selected for viewing, whereupon the data which corresponds to the selected B slices is retrieved from the 3D data set to provide views of the B slices
200
,
210
. As shown in
FIG. 3
, a C-slice
300
may also be selected from the 3D data set for viewing. Accordingly, the data which corresponds to the C slice
300
is selected from the 3D data set and displayed. As shown in
FIG. 4
, first and second I slices
400
,
401
are selected from the 3D data set for viewing. In particular, the first I slice
400
is tilted in the volume
100
so that the top of the first I slice
400
is closer to the 2D array of ultrasound transducer elements than the bottom of the first I slice 400. Similarly, the second I slice
401
is tilted in the volume
100
so that the top of the second I slice
401
is closer to the 2D array of ultrasound transducer elements than the bottom of the second I slice
401
.
Unfortunately, the time needed to scan the volume
100
in each of the cases shown in
FIGS. 2-4
may limit the data acquisition rate of conventional 3D ultrasound imaging systems. For example, a conventional 3D ultrasound imaging system may need to complete a first scan of the volume
100
before starting a second scan. Therefore, the size of the volume
100
may limit the data acquisition rate of the conventional 3D ultrasound imaging system.
It is also known to use two orthogonal linear arrays to produce two orthogonal B slices as described in “Real-Time Orthogonal Mode Scanning of the Heart. I. System Design,” J. Amer. Coll. Cardiol., Vol. 7, 1986, pp. 1279-1285 by Snyder et al., which is incorporated herein by reference. Unfortunately, the system discussed by Snyder et al. may not be capable of scanning B slices which are oriented at a non-orthogonal angle with respect to each other and the two dimensional array of ultrasound transducer elements.
As described above, the data acquisition rate of conventional 3D ultrasound imaging systems may need to be increased as the size of the volume scanned is increased or as the desired frame rate is increased. The size of the volume scanned may be increased by increasing the depth of the scan or increasing the angle over which the scan is performed. For example, increasing the data acquisition rate may allow an increase in the azimuth angle from 60° to 80°. Alternatively, increasing the data acquisition rate may be used to provide deeper scans while maintaining a desired fame rate. Accordingly, there is a need to further increase the data acquisition rate of 3D ultrasound imaging systems.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to allow an improvement in 3D ultrasound imaging systems.
It is a further object of the present invention to allow an increase in the data acquisition rate of 3D ultrasound imaging systems.
These and other objects of the present invention are provided by selecting a configuration of slices of a volume which is to be scanned from a plurality of configurations. Subsequently, the volume is scanned based on the selected configuration of slices. In particular, B slices, I slices, and/or C slices may be selected as the configuration of slices of the volume to be scanned. The volume is then scanned based on which slice configuration was selected. For example, if an I slice is selected as the slice configuration the volume is scanned based on the I slice configuration which provides a 3D data set that represents the portion of the volume located upstream from the I slice. The portion of the volume located downstream from the I slice is not scanned.
Consequently, a 3D ultrasound imaging system which operates according to the present invention may be capable of reducing the time needed to provide a view of the selected slice compared to conventional systems. For example, the time saved by not tracking a transmit ultrasound beam downstream from a selected slice may allow the next transmit ultrasound beam to be transmitted sooner, thereby reducing the time needed to scan the volume. The time reduction may allow an increase in the data acquisition rate which may allow the volume to be scanned more times per a unit of time. Scanning the volume more times may increase the signal-to-noise ratio of the images produced by a system according to the present invention. In general, scanning the volume more times may allow noise in the scans to be reduced by averaging the noise over time. The reduction in time may be estimated by comparing the respective sizes of the entire volume and the portion of the volume through which the transmit ultrasound beams are tracked.
In one embodiment of the present invention, transmit ultrasound beams are transmitted downstream from an ultrasound transducer through a selected slice to a scan range. The transmit ultrasound beams are tracked downstream in the volume until the transmit ultrasound beams reach respective po
Chapman John E.
Duke University
Myers Bigel & Sibley & Sajovec
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