Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-12-14
2003-04-08
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06544179
ABSTRACT:
TECHNICAL FIELD
This invention relates to diagnostic ultrasound imaging, and, more particularly, to a system and method for automatically selecting the position of one or more focal positions of a transmitted ultrasound beam.
BACKGROUND OF THE INVENTION
Ultrasound can be used to image tissues and vessels using a variety of imaging modalities. For example, B-mode scanning can be used to image tissues by portraying the tissues in a gray scale in which the brightness of each region of the image is a function of the intensity of ultrasound returns from corresponding regions of the tissues. B-mode scanning can be used to visualize the shapes of organs and vessels, and to detect the presence of masses, such as tumors, in tissues. Doppler scanning can be used to provide images showing the velocity of moving sound reflectors, such as blood flowing through an artery or vein. Using Doppler scanning to image the flow pattern of blood through a vessel allows the internal shape of the vessel to be inferred. As a result, partial obstructions in blood vessels can be detected.
A conventional diagnostic ultrasound imaging system
10
is shown in FIG.
1
. The ultrasound imaging system
10
includes a scanhead
20
having a transducer face that is placed in contact with a target area containing tissues, organs or blood vessels of interest. As explained below, the scanhead
20
includes an array of transducer elements
24
each of which transforms a transmit signal into a component of an ultrasound beam and transforms an ultrasound reflection into a respective receive signal. These signals are coupled between the scanhead
20
and an imaging unit
30
through a cable
26
. The imaging unit
30
is shown mounted on a cart
34
. The imaging system also includes a control panel
38
for allowing a user to interface with the system
10
. A display monitor
40
having a viewing screen
44
is placed on an upper surface of the imaging unit
30
.
In operation, the transducer elements
24
in the scanhead
20
collectively transmit a beam
50
of ultrasound energy as shown in FIG.
2
. Respective electrical signals, typically at a frequency of 1-20 MHz, are applied to all or some of the transducer elements
24
. The number of transducer elements
24
to which electrical signals are applied determines the size of the transmit aperture. The size of the aperture affects the size of the imaging field and resolution, as explained below. In practice, the phases of the electrical signals applied to the transducer elements
24
are adjusted so that the beam
50
is focused in a focal position
52
. The depth to the focal position
52
beneath the transducer face is controlled by the magnitude of the differences in phase of the electrical signals applied to the transducer elements
24
. The focal length, which corresponds to the effective length of the focal position
52
, is determined by the size and gain of the transmit aperture, i.e., the number of transducer elements
24
used to form the beam
50
. The focal position
52
should ideally be positioned where features of maximum interest are located so that these features will be in the best attainable focus. The focal position
52
is shown for illustrative purposes in
FIG. 2
as being considerably “sharper” than typical in practice. The ultrasound from the individual transducer elements
24
is normally diffracted by tissues so that the effective length of the focal position
52
is actually more of an area where the beam
50
is narrowed rather than a location where the beam
50
comes to a point.
As previously mentioned, the transducer elements
24
are also used to receive ultrasound reflections and generate corresponding electrical signals. As shown in
FIG. 3
, the phase and gain of the received signals are also adjusted to effectively generate a receive beam
56
that is focused to a focal position
58
corresponding to the phase differences between the signals coupled from the transducer elements
24
. (In the interest of clarity, beam components for only two transducer elements
24
are shown, although it will be understood that beam components would exist for all active transducer elements). The receive beam
56
can also be “steered,” i.e., offset from an axis that is perpendicular to the transducer face, by adjusting the phase differences between the signals coupled from the transducer elements
24
. In practice, the phase differences between these signals are adjusted as a function of time delay from each ultrasound transmission so that the focal position
58
dynamically varies with depth from a relatively deep position
60
to a relatively shallow position
62
from where the ultrasound is reflected. Thus, in contrast to the constant position of focal position
52
for the transmit beam
50
, the focal position
58
for the receive beam
56
varies dynamically with the depth from where the ultrasound is reflected. As explained below, the disclosed invention relates to the locations of the focal position
52
for the transmit beam
50
rather than the locations of the focal position
58
for the receive beam
56
.
A typical B-mode ultrasound image
64
is displayed on the viewing screen
44
as shown in FIG.
4
. The ultrasound image
64
shows a number of anatomical features, such as tissues
66
and a blood vessel
68
. In the specific case shown in
FIG. 4
, the area of interest to the medical practitioner is the vessel
68
. As a result, the focal position of the transmit beam should ideally be located at the depth of the vessel
68
. The conventional ultrasound imaging system
10
(
FIG. 1
) has the ability to adjust the location of the transmit beam focal position. As shown in
FIG. 4
, the location of the focal position along the depth axis of the image
64
is indicated by a cursor
70
on the right hand side of the viewing screen
44
. The location of the focal position is adjusted by suitable means, such as by manipulating a control on the control panel
38
(FIG.
1
). As a result, a medical practitioner can place the focal position of the transmit beam at the area of greatest interest in the ultrasound image
64
.
It is possible for objects of interest to be larger than can be effectively focused by a single focus position, or that there are multiple objects at different depths of field, which cannot be adequately focused by a single focus position. One solution to this problem is provided by the conventional ultrasound imaging system
10
generating an image using two or more transmit focal positions, as shown in FIG.
5
. The viewing screen
44
shows a B-mode image
80
showing tissues
82
containing a relatively large blood vessel
84
. A single focal region may be too small to optimally image the vessel
84
. For this reason, a medical practitioner has the option of selecting a number of transmit focal positions, e.g., two focal positions as indicated by the cursors
86
,
88
on the right hand side of the viewing screen
44
, as shown in FIG.
5
. The positions of the focal positions are adjusted by suitable means, such as by manipulating a control of the control panel
38
.
The two transmit focal positions are used by first transmitting a beam of ultrasound focused at the first focal position. Ultrasound reflections are then obtained as explained above, and a first set of data corresponding thereto are stored by suitable means. A second beam of ultrasound focused at the second focal position is then transmitted, and ultrasound reflections are then also obtained and a second set of data corresponding thereto are stored. The image
80
is then formed using both sets of stored data, with the portion of the image in the first focal position predominantly derived from the first set of data and the portion of the image in the second focal position predominantly derived from the second set of data. A preferred way to employ multiple transmit focal regions is described in U.S. Pat. No. 6,315,723.
The operation of the system
10
has been explained with reference to the B-mode images shown in
FIGS. 4 and 5
. However, it will be un
Chenal Cedric
Olsson Lars Jonas
Schmiesing Daniel C.
Dorsey & Whitney LLP
Jaworski Francis J.
Koninklijke Philips Electronics NV
LandOfFree
Ultrasound imaging system and method having automatically... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ultrasound imaging system and method having automatically..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ultrasound imaging system and method having automatically... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3054108