Scalable real-time ultrasound information processing system

Details Scalable real-time ultrasound information processing system Scalable real-time ultrasound information processing system

1999-11-24

2004-03-02

Alam, Hosain (Department: 2155)

Electrical computers and digital processing systems: multicomput

Miscellaneous

C709S200000, C709S241000, C709S241000, C709S201000, C709S205000, C128S915000, C128S916000, C600S437000, C600S442000, C600S447000, C600S453000, C600S345000, C600S502000, C600S553000, C600S348000

Reexamination Certificate

active

06701341

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of ultrasound information processing systems. In particular, the present invention relates to an architecture for a low-cost, flexible, and scalable ultrasound information processing system capable of performing computationally intensive image processing algorithms in real time on ultrasound data.
BACKGROUND OF THE INVENTION
Ultrasound imaging systems are advantageous for use in medical diagnosis as they are non-invasive, easy to use, and do not subject patients to the dangers of electromagnetic radiation. Instead of electromagnetic radiation, an ultrasound imaging system transmits sound waves of very high frequency (e.g., 2 MHz to 10 MHz) into the patient and processes echoes reflected from structures in the patient's body to form two dimensional or three dimensional images. Many ultrasound information processing algorithms are known in the art, e.g., echo mode (“B mode”) processing algorithms, motion mode (“M mode”) processing algorithms, Doppler shift echo processing algorithms, color flow mode processing algorithms, and others.
In the design and development of an ultrasound information processing architecture, there have historically been tradeoffs among features directed to high data throughput (to allow for real-time image display image), flexibility (to accommodate various ultrasound clinical applications), scalability (for adapting a given ultrasound hardware architectures to differing field capacity requirements), and low cost of manufacture and maintenance. Generally speaking, the prior art ultrasound hardware architectures directed to higher data throughputs have had shortcomings in the areas of flexibility, scalability, and cost, while other prior art architectures directed to increased flexibility have had shortcomings in real-time data throughput and scalability.
FIG. 1
shows a block diagram of a conventional ultrasound information processing system
100
similar to a system disclosed in U.S. Pat. No. 5,492,125, “Ultrasound Signal Processing Apparatus,” the contents of which are hereby incorporated by reference into the present disclosure. Ultrasound information processing system
100
comprises a system controller
102
for receiving and displaying user control information via a user interface
104
. During operation, system control signals are output to an ultrasound front end comprising a transducer
106
, a transmitter
108
, and a beam-former
110
. Transmitter
108
generates output signals to transducer
106
to define aperture, apodization, focus and steering of acoustic ultrasound signals into the target subject. Reflected signals from the subject being imaged are sensed by transducer
106
and captured as a patterned beam by beam-former
110
.
In the system of
FIG. 1
, the captured signals are sent to a back end signal processing subsystem
112
in the form of digital echo signals, flow signals and/or Doppler signals according to various modes of operation. For purposes of the present disclosure, the captured signals are referred to herein as digital samples, it being understood that the physical significance of the digital samples will vary according to the mode of operation. The function of the back end signal processing subsystem is to process the digital samples and generate image data for output device
114
.
FIG. 2
shows a diagram of a representative frame
200
of an ultrasound target with, respect to a transducer
202
for more particularly describing the digital samples being processed by the back end signal processing subsystem
112
. In the example of
FIG. 2
the transducer
202
, which corresponds generally to the transducer
106
of
FIG. 1
, is a convex probe transducer with a 90 degree span. As shown in
FIG. 2
, the frame
200
comprises a set of scan lines
204
and a set of zones
206
. In a typical ultrasound application, there may be up to 256 scan lines, and for each scan line there may be up to 1024 digital samples corresponding to ultrasound beam reflections. Each digital sample is typically 8 to 32 bits depending on the particular application. The scan lines
204
may be identified by their sequential position or by an angular position with respect to the center line of the transducer
202
. Importantly, it is to be understood that the dimensions, resolutions, and other parameters disclosed herein are presented by way of example only to more clearly describe the features and advantages of the preferred embodiments disclosed infra, and are not intended to limit the scope of the preferred embodiments.
As known in the art, the frame
200
may also be divided axially (i.e., depthwise) into zones
206
for applications such as multi-zone focusing. In multi-zone focusing, acoustic ultrasound pulses may be sent and received in gated time windows focused to a particular zone for greater resolution in that particular zone. The number of zones
206
may vary greatly, with typical numbers being between 4 and 20 zones.
FIG. 3
shows a diagram of a representative frame
300
of an ultrasound target with respect to a flat probe transducer
302
. The frame
300
also comprises scan lines
304
and zones
306
similar to the scan lines
204
and zones
206
of
FIG. 2
, respectively, except that the scan lines
304
may be indexed by distance offset (e.g., in centimeters) instead of angular offsets as in FIG.
2
.
A problem arises in practical ultrasound systems when real-time ultrasound imaging is required, due to the high throughput rate required in real-time ultrasound imaging. For real-time ultrasound imaging systems, based on the typical parameters recited above with respect to
FIGS. 2 and 3
, using a digital sample resolution of 24 bits per sample and a desired frame rate of approximately 60 frames per second, the data throughput rate for the back end signal processing subsystem
112
would need to be as great as (24)(1024)(256)(60)=368 Mbps to permit real-time results. However, as described in Zagzebski,
Essentials of Ultrasound Physics
(1996), the contents of which are hereby incorporated by reference into the present disclosure, unprocessed ultrasound images display a variety of undesirable characteristics such as speckle, blur, blockiness and other adverse artifacts. To reduce the undesirable characteristics, and also to obtain further useful information from the ultrasound data, it is desirable to perform a variety of image processing algorithms on the ultrasound data prior to display such as speckle reduction, histogram equalization, contrast limited adaptive histogram equalization, edge detection, boundary enhancement, 2-D graphics, 3-D volume visualization, tissue characterization, image segmentation, perfusion measurements, and other algorithms. Additionally, as shown in U.S. Pat. 5,885,218, the contents of which are hereby incorporated by reference into the present disclosure, new spatial signal processing algorithms are continually being introduced for obtaining further useful information from the ultrasound data. Accordingly, there is a need for an ultrasound processing hardware platform capable of performing complex signal processing algorithms on ultrasound data while also being capable of sustaining the above very high throughput rate for real-time imaging.
U.S. Pat. No. 5,492,125 (“the '125 patent”) is directed to the goal of an ultrasound signal processing apparatus having a back-end ultrasound processing subsystem that is more versatile and programmable. In contrast to prior systems presented therein containing multiple distinct special-purpose processor boards dedicated to a particular type of ultrasound processing (e.g., one processor board for Doppler processing, a different board for B-mode processing, etc.), the '125 patent discloses the use of a common pool of programmable multiprocessors such as multimedia video processors. However, in the '125 patent, the programmable multiprocessors access a shared memory through a crossbar switch. Although the apparatus of the '125 patent is adaptable to different image proc

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