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Claims  |
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Having described our invention, we claim:
1. A system for obtaining 3-dimensional ultrasonic images of an object
under study comprising:
an ultrasonic transducer assembly, said transducer assembly producing
ultrasonic pulses directed toward said object and producing 2-dimensional
data from a radio frequency output in response to ultrasonic echo pulses
received,
means to generate 2-dimensional data in sequential scan planes separated
from each other by an angular increment,
means to determine the angular increment between said sequential scan
planes and produce output position signals and,
signal processing means receiving said 2-dimensional data from said
ultrasonic transducer assembly and the output position signals from said
means to determine the angular increment and generating 3-dimensional
cross-sectional data of said object,
wherein said means to generate sequential scan planes comprises a handle
coupled to said transducer assembly, said handle manually movable to
rotate said ultrasonic transducer assembly about an axis perpendicular to
said scan plane.
2. The system of claim 1 wherein said means to generate sequential scan
planes comprises an electrical motor coupled to said transducer assembly
to rotate said ultrasonic transducer assembly about an axis perpendicular
to said scan plane.
3. The system of claim 2 wherein said motor is a stepper motor.
4. The system of claim 3 wherein said means to determine the angular
increment comprises means to provide a predetermined input voltage to said
stepper motor wherein said predetermined input voltage causes a known
rotation of said motor to produce a known angular rotation in said
transducer assembly.
5. The system of claim 4 wherein said means to generate sequential scan
planes comprises a handle coupled to said transducer assembly and manually
moved to rotate said ultrasonic transducer assembly about an axis
perpendicular to said scan plane.
6. The system of claim 1 wherein said means to determine the angular
position comprises an optical encoder mounted to said transducer to sense
rotation thereof and generate said output position signals.
7. The system of claim 1 wherein said means to determine the angular
position comprises a position encoding potentiometer.
8. The system of claim 1 wherein said transducer comprises piezoelectric
array and said means to generate sequential scan planes of ultrasonic echo
pulses comprises means for controlling excitation pulses to each element
in said array.
9. The system of claim 8 wherein said means to determine the angular
increment between said sequential scan planes comprises control means to
determine the order of excitation pulses to each element in said array.
10. The system of claim 1 further comprising a therapeutic transducer
assembly coupled to said ultrasonic transducer assembly, said therapeutic
transducer including means producing a high energy ultasonic beam focused
to converge at a focal point and wherein said scan planes of said
ultrasonic transducer overlap said high energy ultasonic beam and said
focal point.
11. The system of claim 10 further comprising means to excite said
therapeutic transducer assembly.
12. The system of claim 1 wherein said ultrasonic transducer assembly
comprises a piezoelectric transducer, and further comprising a real-time
B-scan module to excite said piezoelectric transducer and to process said
radio frequency output signals and a beam display module to produce a
B-scan output.
13. The system of claim 12 further comprising computer means to receive the
B-scan output for analysis of the object.
14. The system of claim 12 further comprising display means receiving said
B-scan output from one of said scan planes in real-time, said display
means having an overlay representing positioning data.
15. The system of claim 14 wherein said overlay contains an outline of a
therapeutic beam and its focal point.
16. The system of claim 12 further comprising means to rotate said
piezoelectric transducer about an axis perpendicular to a scan plane,
whereby a scan sector in said scan plane is shifted.
17. The system of claim 1 further comprising a therapeutic transducer,
means defining a feedback path from said signal processing means to said
therapeutic transducer to vary the output thereof in real-time based on
analysis of tissue by said signal processing means.
18. The system of claim 17 wherein said ultrasonic transducer is a B-scan
device and said signal processing means receives said radio frequency
output of said B-scan device for tissue analysis based on predetermined
operational parameters.
19. The system of claim 1 further comprising a plurality of therapeutic
transducers positioned at spaced locations, means to move any one of said
plurality of therapeutic transducers to a new position while another of
said plurality of therapeutic transducers is excited to produce a
therapeutic beam.
20. The system of claim 1 further comprising means to determine the volume
of said object based on said 3-dimensional cross-sectional data.
21. A system for obtaining 3-dimensional ultrasonic images of an object
under study comprising:
an ultrasonic transducer assembly, said transducer assembly producing
ultrasonic pulses directed toward said object and producing 2-dimensional
data from a radio frequency output in response to ultrasonic echo pulses
received,
means to generate 2-dimensional data in sequential scan planes separated
from each other by an angular increment,
position encoding potentiometer means to determine the angular increment
between said sequential scan planes and produce output position signals
and,
signal processing means receiving said 2-dimensional data from said
ultrasonic transducer assembly and the output position signals from said
means to determine the angular increment and generating 3-dimensional
cross-sectional data of said object.
22. A system for obtaining 3-dimensional ultrasonic images of an object
under study comprising:
an ultrasonic transducer assembly, said transducer assembly producing
ultrasonic pulses directed toward said object and producing 2-dimensional
data from a radio frequency output in response to ultrasonic echo pulses
received,
means to generate 2-dimensional data in sequential scan planes separated
from each other by an angular increment,
means to determine the angular increment between said sequential scan
planes and produce output position signals,
signal processing means receiving said 2-dimensional data from said
ultrasonic transducer assembly and the output position signal from said
means to determine the angular increment and generating 3-dimensional
cross-sectional data of said object,
a plurality of therapeutic transducers positioned at spaced locations, and
means to move any one of said plurality of therapeutic transducers to a
new position while another of said plurality of therapeutic transducers is
excited to produce a therapeutic beam.
23. A system for obtaining 3-dimensional ultrasonic images of an object
under study comprising:
a piezoelectric ultrasonic transducer assembly, said transducer assembly
producing ultrasonic pulses directed toward said object and producing
2-dimensional data from a radio frequency output in response to ultrasonic
echo pulses received,
means to generate 2-dimensional data in sequential scan planes separated
from each other by an angular increment,
means to determine the angular increment between said sequential scan
planes and produce output position signals,
signal processing means receiving said 2-dimensional data from said
ultrasonic transducer assembly and the output position signals from said
means to determine the angular increment and generating 3-dimensional
cross-sectional data of said object,
a real-time B-scan module to excite said piezoelectric transducer and to
process said radio frequency output signals,
a beam display module to produce a B-scan output, and
display means receiving said B-scan output from one of said scan planes in
real-time, said display means having an overlay representing positioning
data.
24. A system for obtaining 3-dimensional ultrasonic images of an object
under study comprising:
a rotatable ultrasonic transducer assembly, said transducer assembly
producing ultrasonic pulses directed toward said object and producing
2-dimensional data from a radio frequency output in response to ultrasonic
echo pulses received,
means to generate 2-dimensional data in sequential scan planes separated
from each other by an angular increment,
optical encoder means mounted to said transducer assembly to determine the
angular increment between said sequential scan planes and produce output
position signals by sensing rotation of said assembly and,
signal processing means receiving said 2-dimensional data from said
ultrasonic transducer assembly and the output position signals from said
means to determine the angular increment and generating 3-dimensional
cross-sectional data of said object.
25. The system of claim 24, wherein said means to generate sequential scan
planes comprises a handle coupled to said transducer assembly which is
manually movable to rotate said ultrasonic transducer assembly about an
axis perpendicular to said scan plane.
26. The system of claim 23 further comprising a plurality of ultrasonic
transducers for diagnostic application.
27. The system of claim 22 wherein said means to determine the angular
position comprises an optical encoder mounted to said transducer to sense
rotation thereof and generate said output position signals.
28. The system of claim 22 wherein said means to determine the angular
position comprises a position encoding potentiometer.
29. The system of claim 21 wherein said means to generate sequential scan
planes comprises an electrical motor coupled to said transducer assembly
to rotate said ultrasonic transducer assembly about an axis perpendicular
to said scan plane.
30. The system of claim 29 wherein said motor is a stepper motor.
31. The system of claim 30 wherein said means to determine the angular
increment comprises means to provide a predetermined input voltage to said
stepper motor wherein said predetermined input voltage causes a known
rotation of said motor to produce a known angular rotation in said
transducer assembly.
32. The system of claim 21 wherein said transducer comprises piezoelectric
array and said means to generate sequential scan planes of ultrasonic echo
pulses comprises means for controlling excitation pulses to each element
in said array.
33. The system of claim 32 wherein said means to determine the angular
increment between said sequential scan planes comprises control means to
determine the order of excitation pulses to each element in said array.
34. The system of claim 21 further comprising a therapeutic transducer
assembly coupled to said ultrasonic transducer assembly, said therapeutic
transducer including means producing a high energy ultrasonic beam focused
to converge at a focal point and wherein said scan planes of said
ultrasonic transducer overlap said high energy ultrasonic beam and said
focal point.
35. The system of claim 34 further comprising means to excite said
therapeutic transducer assembly.
36. The system of claim 21 wherein said ultrasonic transducer assembly
comprises a piezoelectric transducer, and further comprising a real-time
B-scan module to excite said piezoelectric transducer and to process said
radio frequency output signals and a beam display module to produce a
B-scan output.
37. The system of claim 36 further comprising computer means to receive the
B-scan output for analysis of the object.
38. The system of claim 36 further comprising display means receiving said
B-scan output from one of said scan planes in real-time, said display
means having an overlay representing positioning data.
39. The system of claim 38 wherein said overlay contains an outline of a
therapeutic beam and its focal point.
40. The system of claim 36 further comprising means to rotate said
piezoelectric transducer about an axis perpendicular to a scan plane,
whereby a scan sector in said scan plane is shifted.
41. The system of claim 21 further comprising a therapeutic transducer,
means defining a feedback path from said signal processing means to said
therapeutic transducer to vary the output thereof in real-time based on
tissue analysis of said signal processing means.
42. The system of claim 41 wherein said ultrasonic transducer is a B-scan
device and said signal processing means receives said radio frequency
output of said B-scan device for tissue analysis based on predetermined
operational parameters.
43. The system of claim 21 further comprising a plurality of therapeutic
transducers positioned at spaced locations, means to move any one of said
plurality of therapeutic transducers to a new position while another of
said plurality of therapeutic transducers is excited to produce a
therapeutic beam.
44. The system of claim 21 further comprising means to determine the volume
of said object based on said 3-dimensional cross-sectional data. |
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Description |
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BACKGROUND OF THE INVENTION
This invention relates to a system of ultrasonic diagnosis and therapy. In
particular, this invention relates to the use of ultrasonics for providing
in real-time, cross-sectional and 3-D images of an organ for diagnosis and
utilizing the same system to treat disorders by non-invasive means. The
invention combines two components, a real-time ultrasonic piezoelectric
diagnosis unit and a high intensity, focussed therapeutic ultrasonic
sub-system.
Ultrasonic transducers used for non invasive therapeutic applications are
known in the art. Such ultrasonic transducer assemblies generally comprise
a housing and a transducer mounted within the housing for radiating a
converging beam of acoustic energy in response to an applied electrical
signal. The beam of acoustic energy converges to a focal point which is
usually the therapeutic point of application. Such devices have found
utilization in the treatment of disorders of the eye or other organs by
non-invasive means.
The applications of ultrasound in the field of ophthalmology is discussed,
for example, in Coleman et al. "Therapeutic Ultrasound in the Production
of Ocular Lesions", Amer. J. of Ophthal., Vol. 86, No. 2, pp. 185-192,
1978 and Coleman, et al. "Applications of Therapeutic Ultrasound in
Ophthalmology" Progress in Medical Ultrasound, pp. 263-270 (1981). The use
of a paraxial diagnostic transducer is disclosed to allow manual
positioning of the therapeutic focus within the targeted zone. The
position of the therapeutic focus within the targeted zone is monitored by
observation of a diagnostic B-scan or A-scan display. Once positioned, the
therapeutic transducer is actuated for the desired application of
ultrasound for example the production of lesions.
U.S. Pat. No. 3,735,755 discloses a complete ultrasonic system employing a
transducer assembly used by the operator for both display and treatment.
The complicated system disclosed therein is cumbersome and does not
provide the level of data needed to perform difficult procedures in
real-time in a simple clinical setting.
B-scan diagnosis devices and transducers are also discussed in U.S. Pat.
Nos. 4,141,347 and 4,237,901.
Ultrasonic techniques have also been employed successfully in lithotropsy.
In systems using acoustic shock wave generation the transducer may be
employed together with an ultrasonic positioning unit. The extent of
therapeutic action is determined by subsequent X-ray. Alternatively, a
separate ultrasonic scanner may be employed in a paraxial arrangement for
positioning.
Reference is made to U.S. Pat. No. 4,617,931 which relates to a transducer
for producing shock waves and an auxiliary ultrasonic transducer disposed
paraxially and mechanically swept. Use of the piezoelectric transducer
itself for positioning is disclosed in Ziegler et al, "Extracorporeal
Piezoelectric Lithotropsy". A commercial system employing B-scan and a
lithotropic transducer is the Piezolith 2200 manufactured by Richard Wolf
GMBH and described in Riedlinger et al, "Die Zertrummerung von
Hierensteinen durch piezoelektrisch erzengte Hochonergie-Schallpulse",
urologe [A] (1986) 25:188-192. Reference is also made DE 27 22 252 Al and
a Dornier system technical description entitled "Entwicklung eines
Verfahrens zur beruhrungsfreien Zerkleinerung von Hierensteinen durch
StoBwellen" (1976).
Reference is made to U.S. Pat. No. 4,484,569, entitled "Ultrasonic
Diagnostic and Therapeutic Transducer Assembly and Method for Using",
commonly assigned, which is expressly incorporated herein by reference.
The system described therein allows the use of the single transducer
assembly to generate acoustic energy for purposes of either diagnosis by
generating A-scan images or, to use ultrasonic beams for non-invasive
treatment.
Using the technology of the '569 patent, with the patient properly
prepared, the transducer assembly that houses the therapeutic and
diagnostic transducers is first used for diagnostic purposes to allow
displays for the practitioner so that the organ under scrutiny may be
explored. Once this diagnostic phase is completed, ultrasonic energy from
the same transducer assembly may be used to perform non-invasive treatment
of the organ. The power to the therapeutic transducer produces a burst of
high energy acoustic radiation applied to the site requiring treatment.
Following the application of a therapeutic beam, the initial diagnostic
transducer may be used to provide A-scan and ultrasonic echoes to
determine changes in tissue characteristics. The process is then repeated
on an iterative basis until the treatment has been completed.
The '569 patent also allows for visual positioning of the therapy beam by
the use of a light beam radiated through the transducer by means of a
fiber optic conduit.
While this system offers important advantages in the treatment of tissue
disorders, especially those of the eye, a need exists to provide viewing
and data collection of diagnostic information for 2- and 3-dimensional
positioning, i.e., aiming and for information concurrent with therapeutic
application of ultrasound. Concurrent monitoring would allow the
practitioner to apply intense ultrasound to tissue on a real-time basis,
and judge the condition of the insonified tissue during irradiation. This
in turn would permit a determination of whether further treatments are
called for and the precise location for such treatment.
It is therefore an object of this invention to provide for a new and
improved ultrasonic system which allows for the concurrent diagnosis and
therapeutic application of ultrasonic waves to tissue.
An important object of this invention is to provide a system of three
dimensional ultrasonic echo image generation.
Yet another object of this invention is to provide a system of real-time
monitoring of ultrasound therapy to assess the dynamic response within
tissue during and immediately after insonification.
A further object of this invention is to provide for an ultrasonic system
wherein viewing and data collection of diagnostic information occur
concurrently with therapeutic applications.
A still further object of this invention is to provide a system of visual
image display depicting tissue regions that are likely to be modified by
selecting specific exposure conditions such as time, intensity, beam
profile, frequency and the like.
SUMMARY OF THE INVENTION
In accordance with this invention, a system is provided that integrates a
rapid scan, real-time diagnostic ultrasonic system with a therapeutic
ultrasonic system. The real-time diagnostic portion of the system provides
three-dimensional and/or cross-sectional images of the tissue under
scrutiny in real-time. Preferably, in the case of the eye the diagnostic
transducer is a broad band B-mode device with a 1O MHz center frequency
housed in an assembly that is physically attached to the therapeutic
transducer assembly. The diagnostic transducer may be a single element or
an array of elements in one or two dimensions. The therapeutic transducer
assembly contains a high-intensity piezoelectric transducer and a coupling
cone filled with degassed, distilled water held in place with a thin,
acoustically transparent rubber membrane. The therapeutic transducer
assembly may also contain a central diagnostic transducer for axial
positioning and a central fiber optic system whose projected light beam
specifies the central axis of the therapeutic beam. This subcomponent is
described in U.S. Pat. No. 4,484,569, previously incorporated herein by
reference.
In order to obtain 3-dimensional images, the real-time diagnostic
transducer is rotated to obtain sequential scan planes. This rotation can
take place by either physically rotating the real-time transducer assembly
or electrically scanning with a transducer array. In the case of
physically rotating the position of the transducer assembly would be
determined by a shaft encoder or by using a stepper motor to move the
transducer in a known manner. If the real-time transducer comprises an
array, scanning can occur by sequential excitation of the array elements
to obtain a series of output pulses indicative of data from each scan
plane. In this mode of implementation the array is fixed in a known
orientation so that a predetermined angular separation exists between scan
planes. In both cases, the signals can be appropriatly gated to select an
area for data acquisition within each scan plane.
In a preferred embodiment of the system, the diagnostic transducer assembly
is attached to the cone of the therapeutic transducer assembly. This
attachment allows the practitioner to adjust the rotation, angulation and
position of the scanning diagnostic transducer and to lock the two
transducer assemblies in place, so that the position and orientation of
the therapeutic beam can be fully specified within the set of B-scan
planes.
This invention will be described in greater detail by reference to the
accompanying drawings and the description of the preferred embodiment
which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the system of this invention for carrying out
concurrent, real-time ultrasonic diagnosis and therapeutic application;
FIG. 2 is a schematic drawing illustrating the scanning mechanisms for
serial plane examinations;
FIG. 3 is a schematic view of the real-time B-scan transducer and
therapeutic transducer assembly for the presentation of cross sectional
data;
FIG. 4 is a diagram illustrating the display format of the therapeutic beam
superimposed on the B-mode image;
FIG. 5A and FIG. 5B are B-scan images of a liver sample before and after
ultrasonic exposure in a lesion placement experiment;
FIG. 6A and FIG. 6B are B-scan images of a liver sample before and after
ultrasonic exposure in a second lesion placement experiment.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, a block diagram of the system in accordance with
this invention is depicted.
The block diagram of FIG. 1 depicts a complete proposed clinical system
which employs both a therapeutic transducer and a real-time B-scan unit to
obtain pseudo 3 dimensional displays of reflective structures in a human
organ or, of other material objects. The therapeutic transducer 50 and its
associated electronics are described and discussed in detail in U.S. Pat.
No. 4,484,569 which is expressly incorporated herein by reference. The
therapeutic transducer 50 also includes a fixed diagnostic transducer 51
and is attached to a coupling cone 54. The therapeutic transducer 50 is
actuated by a therapeutic excitation unit 53 and the diagnostic transducer
51 is coupled to a biometric A-scan and M-mode unit 55. A computerized
tissue analysis system is employed for the purpose of diagnosing tissues
prior to application of the therapeutic beam and to closely monitor subtle
changes which may be induced by therapy. That computerized tissue analysis
system is discussed in detail in copending patent application Ser. No.
641,015 filed on Aug. 15, 1984, and entitled A Method for Enhancement of
Ultrasonic Image Data.
The diagnostic transducer 51 may have a fiber optic source used for precise
lateral positioning of the therapeutic transducer as disclosed in the '569
patent.
An important aspect of this invention is the use of a B-scan unit coupled
to the therapeutic transducer coupling cone 54 but either mechanically
rotated or electrically swept to obtain data for 3-dimensional
presentation. The scan outline 71, 73 defines the angular limits of B-scan
sector 75. As illustrated in FIG. 1, one such sector defines a scan plane.
Electronics for the B-scan transducer are contained in a real-time B-scan
unit 77 which provides an output to a beam display module 79. The beam
outline for each scan plane is stored in a digital memory contained in the
beam display module 79. FIG. 1 also illustrates that the output from the
real-time B-scan unit 77 and the beam display module 79 are used to
provide inputs to the computer tissue analysis system 57.
Referring now to FIGS. 1 and 2, the scheme for obtaining ultrasonic echo
data from a sequence of scan planes with known orientations is depicted.
The B-scan unit is schematically depicted in FIG. 2 in a housing 70. As
illustrated therein, ultrasonic echo data from a sequence of scan planes
with a known orientation describes a 3 dimensional position of reflective
structures in a human organ or a material object. If those images from
each plane are displayed in rapid succession, in real-time, the impression
of 3 dimensional geometry is obtained. The data may also be entered into a
digital image processing system such as an ADAGE 3000 to produce pseudo
three dimensional displays.
As illustrated in FIGS. 1 and 2 this system preferably incorporates a
real-time B-scan diagnostic transducer assembly. In the case of ophthalmic
use, a typical assembly would have a small piezoelectric transducer to
send ultrasonic pulses toward the eye and receive echo pulses returned by
structures in the eye. In each scan plane 75, the transducer would be
scanned in a sector format to obtain 2-dimensional cross-sectional data.
In many instruments the transducer would be rotated by means of a small
motor housed in the assembly 70. The motor, 87, pivots the transducer
about an axis which is perpendicular to the scan plane defined by element
75. FIG. 2 illustrates schematically the electrical connections required
to excite the transducer, drive the motor and convey rf voltage signals
generated by the transducer in response to each ultrasonic echo pulse.
Such are coupled to the real-time B-scan unit 77.
The above paragraph describes operations within a single scan plane. To
obtain 3-dimensional data a plurality of scan planes are examined by
rotating the real-time transducer assembly about an axis 81 perpendicular
to one or the other each scan plane (illustrated by arrow in FIG. 2).
The orientation of the entire transducer assembly 70 at each instant in
time may be determined by using a small stepper motor (not illustrated).
In such a system, control of the transducer motion would be effectuated by
using appropriately configured voltage pulses so that each pulse would
cause a known angular shift in transducer assembly position.
Alternatively, a position encoder such as a potentiometer illustrated in
FIGS. 1 and 2 as element 83 can be used to sense transducer orientation
and generate appropriate output voltages as position signals to the beam
display module 79 and the computer 57. Instead of the motor, a handle 85
may be used to achieve manual rotation of the transducer assembly 70.
A preferred technique of determining the angular position of the transducer
is to use an optical encoder. Such an encoder utilizes a grid of clear and
opaque radial lines which alternate in a sector pattern rotating with the
shaft. The encoder employs a light source on one side of the encoder and a
light detector on the other side. As the light beam traverses the grid,
the detector generates a voltage output changing as the light beam is
interrupted by the opaque grid lines. Since the angular separation of the
radial grid lines is known, the occurrence of each voltage pulse is
indicative of an angular increment of movement of the shaft. Such optical
shaft encoders are well known. Another technique could be the use of a
position encoder such as a sine-cosine potentiometer.
As illustrated in FIGS. 1 and 2, angular position outputs generated by the
encoder 83 specify the orientation of the scan sector with respect to the
axis of rotation. Thus, those output signals can be used to determine the
orientation of each scan plane. As illustrated in FIG. 2 sequential scan
planes are generated and the relative 3-dimensional location of each
reflective object in the organ under scrutiny can thus be specified by its
2-dimensional relationship within a B-scan obtained at a known scan plane
orientation. This information can thus be used to determine 3-dimensional
coordinates for a computer driven graphics display.
In FIG. 2, the angular increment .DELTA..theta. between the scan planes is
illustrated as the increment between scan planes 2 and 3. This can be
controlled by signals from the angular position encoder 83, that is the
output signals. For example data can be gated so that it is accepted only
when .theta. is 5.degree.. Additionally, control signals from the
real-time B-scan scanner 77 may be used to determine when a new scan
begins. Thus, using these options a single, complete scan can be displayed
or acquired for digital analysis for each scan plane angular increment,
i.e., 5.degree. or the like. Additionally, as illustrated in FIG. 2, the
area of the scan sector may itself be gated for purposes of digital data
acquisition. The rf signals which are thus acquired from the real-time
B-scan unit 77 and beam display module 79 are used as input to the
computer analysis system. Such a system is described in "Theoretical
Framework for Spectrum Analysis in Ultrasonic Tissue Characterization",
Lizzi et al, J. Acoust. Soc. AM, Vol. 73, pp. 1366-73 (1983).
FIG. 3 illustrates the side-looking coupling of the real-time B-scan unit
with high-intensity focus therapeutic ultrasonic transducer. The
therapeutic transducer assembly 52 comprises a high-intensity
piezoelectric transducer 50 and a coupling cone 54 which is filled with
degassed, distilled water held in place by a thin, acoustically
transparent rubber membrane. (not shown). The specifics of the therapeutic
transducer and its associated electronics are found in U.S. Pat.
4,484,569. The therapy beam produced by the therapeutic transducer 50 has
a focal point (f) with the central axis of the therapy beam illustrated as
dotted line 56. The edges of the therapy beam are defined by the lines 58,
60 converging to the focal point (f) and then diverging.
Referring now to FIGS. 3 and 4, another aspect of this invention is
depicted. In accordance with this aspect, the B-scan unit is employed for
real-time aiming and monitoring. The diagnostic scanning transducer
assembly 70 is a real-time 1OMHz B-mode system coupled to the therapeutic
transducer assembly 52 in a side-looking arrangement. Coupling of the
diagnostic transducer assembly 70 to the therapeutic transducer assembly
52 is via the coupling 72. This coupling allows the transducer assembly 70
to pivot around point 74 and rotate at coupling point 76. The region
covered by the diagnostic scanner beam is defined by lines 78, 80. As
illustrated in FIG. 3, the real-time scan plane of the diagnostic
transducer assembly 70 contains the central axis 56 of the therapeutic
transducer. The attachment mount thus permits the practitioner to adjust
the rotation, angulation, and position of the diagnostic transducer
assembly 70. Once positioned, the transducer assembly 70 is locked into
place.
One technique of achieving proper alignment of the diagnostic transducer
assembly 70 is with a target comprising small, e.g. 1 mm diameter
acoustically reflective spheres mounted on a straight wire. The target is
aligned with the central axis 56 of the therapeutic transducer. The aiming
light and the A-scan transducer associated with the therapeutic unit are
focused on the top ball to adjust the vertical standoff distance. The
therapeutic assembly is moved so that it's A-scan transducer (not shown)
displays echoes from all of the spheres. That is, the axis of the beam is
made coincident with the balls by adjusting the therapy transducer housing
until all balls are centered in the light beam and generate A-scan echoes.
The position and orientation of the B-scan transducer are then adjusted so
that the chain of balls appears at maximum brightness in the B-scan
display. Thus, the central axis 56 and the focal point (f) of the
therapeutic transducer 50 is defined on the B-mode real-time display. In
the B-scan display, the top ball specifies the location of therapy beam's
focal point and the line of balls specifies the beam's axis. The
separation between balls is known by measurement so that their B-scan echo
locations can be used for proper spatial scaling of B-scan images. This
information then is then used with beam calibration data to specify and
position the beam overlay shown in FIG. 4. Beam calibration data can also
comprise schlieren photographs and scans made with small piezoelectric
probes. The diagnostic scanning transducer assembly is now aligned in a
fixed relationship to the therapeutic focal point (f).
The scanning diagnostic transducer assembly 70 employs a mechanically
scanned transducer that is rapidly scanned in a repetitive sector pattern
that includes the path of the therapeutic transducer beam. This scanning
obtains echoes from the tissue under evaluation which are displayed as
cross-sectional images on the monitor of the real-time unit 77. Such a
unit is the Coopervision Ultrasonic Digital-B System IV.
It is apparent that other scanning systems such as the piezoelectric arrays
may be used.
Once the tranducer assembly 70 is aligned and locke | | |
