Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2002-09-27
2004-04-06
Ruhl, Dennis W. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06716174
ABSTRACT:
BACKGROUND
This invention relates to ultrasonic diagnostic imaging systems and, in particular, to increasing the volume or frame rate of volume acquisition in ultrasonic diagnostic imaging systems for applications in volume imaging.
The image quality of medical ultrasound has made it indispensable in diagnosis and management of many diseases. To that end, the development of 3-D ultrasound imaging, for example, 3-D, B-mode, color Doppler and power Doppler, as applied to acquisition, reconstruction and rendering techniques is moving ahead quite steadily with valuable results to the field of diagnostic imaging.
One of the goals of 3-D ultrasound imaging, as stated by Aaron Fenster and Donal B. Downey, 3-
D Ultrasound Imaging: A Review,
IEEE ENGINEERING IN MEDICINE AND BIOLOGY, pages 41-49, November-December 1996, is to reduce to variability of conventional acquisition techniques in order to allow ultrasound diagnosticians an ability to better view patient organs in 3-D. Fenster and Downey support the position of the inventors herein that the relative position and angulation (acquisition geometry) must be accurately known to avoid geometric distortion, and artifacts and distortion due to respiratory, cardiac and involuntary motion. The latter requires rapid and appropriately gated acquisition. To this end, the present invention focuses on electronic 2-D scanning, using a 2-D transducer array.
FIG. 1
illustrates an ultrasonic diagnostic imaging system which may be used in accordance with the principles of the present invention. A scanhead (or transducer, as used interchangeably herein)
26
, including a transducer array
10
, is connected by a cable
11
to a beamformer
36
. The beamformer
36
controls the timing of actuation signals applied to the elements of the transducer array
10
for the transmission of steered and focused transmit beams, and appropriately delays and combines signals received from the transducer elements to form coherent echo signals along the scanlines delineated by the transmit beams. The timing of the beamformer transmission is also responsive to an electrocardiograph (ECG) signal when it is desired to synchronize or gate image acquisition with a particular phase of the heart cycle. The beamformer
36
is further responsive to a scanhead position signal when the transducer is being mechanically moved to sweep ultrasonic beams over a volumetric region, thereby enabling beams to be transmitted when the transducer is properly oriented with respect to the volumetric region.
The output of the beamformer
36
is coupled to a pulse inversion processor
38
for the separation of fundamental and harmonic frequency signals. Pulse inversion processors are well known in the art and are described in U.S. Pat. Nos. 5,706,819 and 5,951,478. These patents describe how echoes from alternately phased pulses can be used to separate harmonic contrast signals from fundamental signals. The fundamental and/or harmonic signals may be B mode processed or Doppler processed, depending upon the desired information to be displayed. For Doppler processing, the signals are coupled to a wall filter
22
which can distinguish between flow, stationary tissue, and moving tissue. A preferred wall filter for contrast imaging is described in U.S. patent application Ser. No. 09/156,097, which is also capable of performing harmonic contrast signal separation. The filtered signals are applied to a Doppler processor
42
, which produces Doppler power, velocity, or variance estimation.
A preferred Doppler processor for harmonic Doppler signal estimation is described in U.S. Pat. No. 6,036,643. Artifacts from scanhead motion which can contaminate Doppler imaging are removed by a flash suppressor
44
. Various techniques may be used to remove flash artifacts prior to or subsequent to image formation, including the notch filter technique described in U.S. Pat. No. 5,197,477 and the min-max filter technique described in U.S. Pat. No. 5,782,769. The processed Doppler signals are stored in a Doppler image memory
40
′. Signals which are to be B mode processed are applied to a B mode processor
24
which detects the signal amplitude. B mode processed signals are stored in a tissue image memory
40
.
The B mode and Doppler signals are applied to a coordinate transformation processor
46
. For conventional two dimensional imaging, the coordinate transformation processor will function as a scan converter, converting polar coordinates to Cartesian coordinates as necessary and filling spaces between received lines with interpolated image data. The scan converted images are coupled to a video processor
70
which puts the image information into a video format for display of the images on a display
100
. The images are also coupled to a Cineloop® memory
56
for storage in a loop if that function is invoked by the user.
When 3D imaging is being performed by the ultrasound system, the coordinate transformation processor may be used to scan convert the tissue and Doppler signals in planes of image information over the scanned volume, or may be used to transform the coordinates of the image data into a three-dimensional data matrix. Preferably the coordinate transformation processor operates in cooperation with a volume rendering processor
50
, which can render a three-dimensional presentation of the image data which has be processed by the coordinate transformation processor.
Three-dimensional images of tissue are rendered in accordance with tissue rendering parameters
54
which are selected by the user through a control panel or user interface (UIF). Three-dimensional images of Doppler information are rendered in accordance with blood flow rendering parameters
52
. These parameters control aspects of the rendering process such as the degree of transparency of tissue in the three-dimensional image, so that the viewer can see the vasculature inside the tissue. This capability is important when 3D images of both tissue and flow are being rendered, as described in U.S. Pat. No. 5,720,291. Three-dimensional images can be stored in the Cineloop® memory
56
and replayed to display the scanned volume in a dynamic parallax presentation, for instance. A three-dimensional rendering of flow without the surrounding tissue, as described in U.S. Pat. No. Re. 36,564, can reveal the continuity of flow of blood vessels and obstructions in those vessels and is useful for coronary artery diagnosis in accordance with the present invention.
Different transducers can be used to scan a volumetric region of the heart which includes the coronary arteries Either a 1D array (azimuth steered) or a 1.5D or 1.75D array (azimuth steered and elevation focused) may be moved mechanically to sweep beams over the three-dimensional volume. For electronic steering either a 1.75D array (minimally electronically steered in azimuth and elevation) or a 2D array (fully electronically steered in azimuth and elevation) may be used. An embodiment which uses a 2D transducer array
10
″ is shown in FIG.
2
. An important consideration in the use of two dimensional arrays is the number of cable wires used to connect the probe to the ultrasound system. Various approaches can be used to reduce the number of cable conductors and thus the size of the cable, including wireless links to the ultrasound system, micro-beamforming in the probe, digital or analog time multiplexing, the use of sparse arrays, and the use of transmit/receive multiplexers. One solution is a radio frequency (RF) probe which transmits echo signals wirelessly to the ultrasound system as described in U.S. Pat. No. 6,142,946.
Another solution, when a cable connection is used, is to partition the beamformer between the scanhead and the ultrasound system as described in U.S. Pat. No. 6,102,869. The
FIG. 2
example implements this approach wherein elevation beamforming in the transducer
26
and azimuth beamforming in the ultrasound system
101
is performed. For example, suppose that the two dimensional array has 128 columns of elements extending in the azimuth direction (indic
Jain Ruby
Koninklijke Philips Electronics , N.V.
Ruhl Dennis W.
Vodopia John
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