Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-04-04
2003-03-25
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06537219
ABSTRACT:
BACKGROUND OF THE INVENTION
Ultrasound transducer assemblies emit ultrasound pulses and receive echoes. In general an ultrasound assembly emits pulses through a plurality of paths and uses the received echoes from the plurality of paths to generate a cross-sectional or volumetric image. Such operation is typically termed “scanning”, “sweeping”, or “steering” a beam. In most ultrasound systems, scanning is rapidly repeated so that many images (“frames”) are acquired within a second of time.
Real-time sonography refers to the presentation of ultrasound images in a rapid sequential format as the scanning is being performed. Scanning is either performed mechanically (by physically oscillating one or more transducer elements) or electronically. By far, the most common type of scanning in modern ultrasound systems is electronic wherein a group of transducer elements (termed an “array”) are arranged in a line and excited by a set of electrical pulses, one pulse per element, timed to construct a sweeping action.
In a linear sequenced array, an aperture is swept across the array by exciting sequential (and overlapping) sub-groups of transducer elements. In a linear phased array, all (or almost all) the elements are excited by a single pulse, but with small (typically less than 1 microsecond) time difference (“phasing”) between adjacent elements, so that the resulting sound pulses pile up along a specific direction (termed “steering”). In addition to steering the beam, the phased array can focus the beam, along the depth direction, by putting curvature in the phase delay pattern. More curvature places the focus closer to the transducer array, while less curvature moves the focus deeper. Delay can also be used with a linear sequenced array to provide focusing.
When an array is receiving echoes, the electric outputs of the elements can be delayed so that the array is sensitive in a particular direction, with a listening focus at a particular depth. This reception focus depth may be increased continually as the transmitted pulses travel through the tissue of the subject being imaged, focusing along the entire depth of the beam. This continual changing reception focus is called dynamic focusing. The combination of transmission focus and dynamic reception focusing greatly improves detail resolution over large depth ranges in images.
The apparatus that creates the various delays is called a beamformer. Known beamformers have traditionally operated in the analog domain employing expensive beamforming circuits capable of delivering a new point of data (dynamically delayed) every nano-second. More recently, digital beamformers, that provide delay by varying read times out of a digital memory, have been developed. While digital beamformers require extensive memory, exact clock devices and large timing tables, these components are cheaper and smaller than their analog counterparts. Such digital beamformers hold out the hope of cost effective portable ultrasound devices nearly as powerful as their stationary brethren.
Known portable ultrasound devices use a 1-D transducer assembly (known available devices use linear sequenced arrays) in the probe to produce an image taken on a plane that extends from the face of the probe. Currently, there are two classes of portable ultrasound devices: ultrasound specific devices and PC add-on devices.
Ultrasound specific devices are simply miniaturized ultrasound devices, typically with digital beamformers, that replicate larger stand alone units. One example of such a device is the SONOSITE device marketed by SONOSITE, INC. Unlike laptop computers, much of the circuitry and software in large top-of-the-line ultrasound systems is not suitable for miniaturization. Larger traditional components, such as beamformers, lose functionality when miniaturized. PC add-on devices attempt to integrate a transducer assembly and a beamformer in a probe housing. The probe is then connected to a PC, typically a well equipped laptop, to perform image creation from the beamformed data. One example of such a device is the TERASON 2000 by TERASON.
Another area of ultrasound technology receiving significant attention are probes having a transducer assembly comprising a matrix of elements (for example a 56×56 array of 3,136 elements), sometimes referred to a 2-D or matrix probe. Because matrix probes allow beam steering in 2 dimensions as well as the aforementioned focus in the depth direction, current efforts are related to using matrix transducer assemblies for the capture of a volume of ultrasound data to be used to render 3-D images. Unfortunately, the commercialization of large real-time full bandwidth 3-D images is probably a couple of years off due to lack of affordable image processing resources capable of acting on the volume of data produced by matrix transducers in real-time. To date no known available portable ultrasound devices utilize a matric transducer assembly, probably due to the expense involved with the implementation of a traditional dynamic focusing beamformers multiplied by the number of elements in a matrix probe that must be sampled.
Ultrasound imaging has always involved a tradeoff between image quality and the image processing resources required to process the data from the transducer to obtain the results desired by the user. While the rate at which data can be acquired is limited by physics (sound only travels so fast in the human body), the types of image processing that can be performed on the data is limited by the amount and quality of image processing resources that can be brought to bear upon the data. If real time imaging is desired, as it usually is, another limiting factor is the rate of data acquisition of the processing system.
Ultrasound data is typically acquired in frames, each frame representing a sweep of ultrasound beams emanating from the face of a transducer. 1-D transducers produce a 2-D rectangular or pie-shaped sweep. 2-D transducers are capable of producing sweeps forming a pre-defined 3-D shape, or volume. It is estimated that to fully process a relatively large volume (60°×60°) of ultrasound data in real time, a beamformer capable with 16×parallelism is required. Such a beamformer would be prohibitively expensive, especially in a market where the acceptable cost of ultrasound systems is rapidly decreasing. Current efforts are focused on ways to short cut full processing while bringing to market a 3-D ultrasound system capable of producing acceptable images at a price point competitive with current 2-D systems. No known portable 3-D solutions are currently available.
FIG. 1
is a block diagram of a known 3-D ultrasound imaging system
100
described in co-pending U.S. patent application Ser. No. 09/633,480 assigned to the assignee of the present application. The apparatus described in the Ser. No. 09/633,480 application uses interleaving to render a 3-D image with the appearance of a real-time image from data produced by a matrix transducer assembly. This allows the use of relatively standard components to minimize cost while providing a state of the art display. The system shown in
FIG. 1
is, at the present time, is not available in a portable package.
The ultrasound system
100
utilizes a standard personal computer (“PC”)
102
, to act as a 3-D image processor and preferably produces an image using interpolated data. The ultrasound system
100
has a matrix transducer assembly
104
and utilizes the concept of sub-group beamforming. In the Example shown in
FIG. 1
, only elements
106
a
through
106
f
are illustrated, but those of ordinary skill in the art will recognize that any number of elements can be utilized. The transducer
104
is preferably configured for sub-group beamforming using a series of ASICs
108
n
. The use of sub-groups in beamforming is described in U.S. Pat. Nos. 5,997,479 and 6,126,602, both assigned to the assignee of the present application, the subject matter of each being incorporated herein by reference.
Two ASICs
108
a
and
108
b
are illustrated, corresponding to elements
10
Poland Mckee D
Savord Bernard J
Jaworski Francis J.
Koninklijke Philips Electronics , N.V.
Vodopia John
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