Ultrasonic diagnostic and therapeutic transducer assembly and method for using

An ultrasonic transducer assembly is provided with transducers for both therapeutic and diagnostic ultrasonic radiation. A moveable seal permits adjustment and alignment of the two transducer units in a fluid medium. In addition, there is provided a light beam directed along the axis of the ultrasonic radiation. The transducer assembly is particularly useful for ophthalmic therapy.

BACKGROUND OF THE INVENTION 
This invention relates to the application of ultrasonic waves for 
diagnostic and therapeutic purposes. The invention particularly relates to 
the application of ultrasonic waves for purposes of diagnosing disorders 
of the eye and treating such disorders by non-invasive ultrasonic 
treatment. In particular this application relates to transducers for 
performing such diagnosis and treatment. 
It is an object of the present invention to provide a new and improved 
transducer assembly which provides for application of both therapeutic and 
diagnostic ultrasonic waves to a human or animal body. 
It is a further object of the invention to provide such a transducer 
assembly wherein the therapeutic and diagnostic waves are directed 
substantially along a single axis. 
It is a further object of the invention to provide such a transducer 
assembly which includes a source of a light beam directed along the axis 
with the therapeutic and diagnostic ultrasonic beams. 
SUMMARY OF THE INVENTION 
In accordance with the invention there is provided an ultrasonic transducer 
assembly, useful for non-invasive applications, comprising a housing and a 
transducer means mounted within the housing for radiating a converging 
beam of acoustic energy in response to supplied electrical signals. The 
beam of acoustic energy converges to a focal point. The transducer has a 
central bore and there is provided a light source mounted within the 
housing and through the central bore of the transducer for emitting the 
light beam toward the focal point. 
In one embodiment the transducer comprises a spherical shell portion having 
an inner radius originating at the focal point. The housing includes means 
for maintaining fluid in contact with the transducer thereby to conduct 
the beam of acoustic energy from the transducer into a body. 
In a particularly advantageous embodiment, the transducer assembly includes 
first and second housing portions, and first and second transducers 
coaxially mounted to the respective housing portions. The light source can 
be mounted through a central aperture in the inner one of the two 
transducers. The first and second housing portions can be pivotably 
mounted to each other thereby to adjust the direction of the beams from 
the first and second acoustic transducers to be along the same axis as the 
light beam. 
For a better understanding of the present invention, together with other 
and further objects, reference is made to the following description, taken 
in conjunction with the accompanying drawings, and its scope will be 
pointed out in the appended claims.

DESCRIPTION OF THE INVENTION 
The block diagram of FIG. 1 illustrates a system for applying diagnostic 
and therapeutic ultrasound to the eye of a human or an animal patient. The 
system of FIG. 1 includes a power control section 10, a diagnostic section 
12, a scan head assembly 16 and a light source 14. The power control 
section 10 functions to provide controlled, relatively high power, bursts 
of ultrasonic energy to the therapeutic transducer 28 which is included in 
the transducer assembly 18 of the scan head assembly 16. The diagnostic 
section 12 operates in conjunction with the diagnostic transducer unit 22 
of the transducer assembly 18. The light source 14 provides a light beam 
through a fiber optic conduit 34 to a central light tube and lens holder 
24 in the transducer assembly 18. 
The system of FIG. 1 functions to provide both diagnostic probing of an eye 
or other organ, visual indication by a light beam of the probe 
orientation, and a therapeutic ultrasonic radiation for performing 
noninvasive surgery, for example, in treating diseases of the human eye or 
an animal eye. 
The power control section 10 includes a frequency synthesizer 38 for 
generating a high frequency ultrasonic signal, for example, approximately 
4 to 10 Mhz. Illustrated in FIG. 1 is a General Radio Model 1164-A 
frequency synthesizer. The output from frequency synthesizer 38 is 
provided to variable attenuator 39, for example, Kay Electric Model 30-0. 
Following variable attenuator 39 there is provided an amplifier 40 which 
is a Hewlett Packard Model 461 A. By use of the frequency synthesizer 38, 
variable attenuator 39 and amplifier 40 it is possible to provide a 
controlled amplitude signal at a selected ultrasonic frequency. The output 
signal of amplifier 40 is provided to a gate or mixer 42, which is a 
Hewlett Packard Model 10514 A. Also provided to mixer 42 over lead 52 is a 
gating signal from a Tektronix oscilloscope Model 585. The gating signal 
is used to provide a controlled duration for the signal at the output of 
amplifier 40. Typically the controlled pulse would have a duration of 5 
seconds. A switch 44 is provided to alternately operate the power control 
section 10 as either a CW or pulsed power supply. When switch 44 is in the 
CW position the output of mixer 42 is provided directly to power amplifier 
56 which is an Electronic Navigation Industries Model 350 L. When pulsed 
power is desired, switch 44 is placed in the lower position so that the 
output of mixer 42 is provided to gate or mixer 46, which is also provided 
with pulse signals from a pulse generator 48, which is a General Radio 
Model 1217-C. The output from mixer 46 is a pulse modulated signal having 
a fundamental ultrasonic frequency determined by frequency synthesizer 38. 
Power amplifier 56 is provided to increase the power of the CW or pulsed 
signal provided thereto, and provide a high power signal over coaxial 
cable 26, which is RG 58/U cable, to the transducer assembly 18 through a 
matching network 58. The RF power provided to matching network 58 can be 
in the order of 20 watts and can achieve an acoustic power output from the 
transducer assembly 18 in the order of 5 to 10 watts. Matching network 58 
includes a lead 60, also RG 58/U cable to provide a portion of the RF 
signal to preamplifier 62 on oscilloscope 50 so that the power supplied to 
the transducer by the matching network can be monitored on the 
oscilloscope display. 
The output of matching network 58 is coupled to the therapeutic transducer 
20 in transducer assembly 18 which will be further described with respect 
to FIG. 2. 
The diagnostic section 12 of the system of FIG. 1 primarily consists of a 
Sonometrics Ophthalmoscan Model 200 unit. This unit 64 includes an A scan 
display 70 and a B scan display 68 which are coupled to position encoding 
units mounted on a scan head assembly by a 9 conductor wire 32 for 
providing angular positioning information relating to the orientation of 
diagnostic transducer unit 22. The Ophthalmoscan unit 64 is also connected 
to diagnostic transducer unit 22 by cable 30 which is a Belden type RG 
174/U coaxial cable. 
Transducer assembly 18 also includes a lens holder 24 which is connected to 
a light source 14 by a fiber optic cable 34. As is familiar to those in 
the art, the scan head assembly 16 includes position sensors which provide 
the signal over the 9 conductor wire to the Ophthalmoscan unit 64. A scan 
head assembly which includes the position sensors is made by Sonometric 
Systems. 
FIG. 2 is a side and partial cross section view of the transducer assembly 
18 of the system of FIG. 1. The assembly 18 of FIG. 2 includes three 
active components, which are the therapeutic transducer 20, the diagnostic 
transducer 22 and the light beam assembly and lens holder 24. Also 
illustrated in FIG. 2, attached to transducer assembly 18 is the matching 
network 58 which serves to provide an impedance match of the transducer 20 
to the impedance existing at the cable 26 through which signals are 
supplied from power amplifier 56. Those skilled in the art will recognize 
that the matching network 58 will have inductive and/or capacitive 
components for the purposes of impedance matching the transducer according 
to the frequency of operation. In one embodiment, the matching network 58 
includes a series inductor and a shunt capacitor. Therapeutic transducer 
20 comprises a spherical shell section having an inner radius which 
originates at a focal point 21. The inner and outer radial surfaces of 
transducer 20 are metal clad, and the transducer itself is made of 
piezoelectric material, typically a ceramic such as lead zirconate 
titanate. In one embodiment the thickness of the transducer is chosen to 
be resonant at 1.4 Mhz. The transducer may be operated at an odd harmonic, 
for example, the third or seventh harmonic, to provide a therapeutic 
ultrasonic signal at a frequency of 4.2 Mhz. for the third harmonic or 9.8 
Mhz for the seventh harmonic. 
The transducer 20 is mounted within a first housing portion 72 of the 
transducer assembly. The first housing portion 72 includes a housing 
member 76 of generally cylindrical configuration. Housing member 76 
engages transducer 20 at one cylindrical end and is sealed to the 
transducer by a bead of silicon rubber 78, which provides for physical 
attachment of the transducer as well. Transducer 20 has a central bore 
through which diagnostic transducer unit 22 passes. Transducer 20 is 
mounted around the central bore by a similar bead 88 of silicon rubber 
cement to a support member 80. Support member 80 is retained within 
housing member 76 by a cylindrical retaining ring 82 which is threaded 
into internal threads in housing member 76, as may be more easily seen in 
the view of the housing portion 72 shown in FIGS. 3 and 4. 
Transducer 20 has its radially outer conductive surface connected to inner 
conductor terminal 146 which leads to matching network 58. This connection 
is made by lead wires 144 which are conductively attached to the surface 
at points 148. 
The radially inner, and radiating surface of transducer 20 is connected to 
the outer conductor terminal 150 leading to matching network 58. This 
connection is made by lead wires 154, which are connected to a ring bus 
152 leading to terminal 150. The wires 154 and 144 pass through apertures 
138 and 140 in support member 80. The wires 154 which lead to the radially 
inner, and radiating surface of transducer 20 also pass through recesses 
78 formed in housing member 76. This connection is more easily seen in the 
cross sectional view of FIG. 2, which is taken through one of these 
recesses. 
Support member 80 is provided with a central bore, which is aligned with 
the central bore of transducer 20 and sealed thereto by the bead of 
silicon rubber 88. Diagnostic transducer unit 22 is cylindrical in shape 
and passes through the central bore in support member 80 and in transducer 
20. Diagnostic transducer 22 can project outwardly from therapeutic 
transducer 20 into a cavity formed by conical shell 128, which is provided 
to retain fluid, such as water, in the vicinity of transducers 20 and 22, 
in order to provide a medium for effective radiation of ultrasound from 
the transducers. Since conical member 128 and the cavity formed thereby is 
to be filled with fluid the front opening 130 is covered by a membrane 
132, preferably of thin rubber, and the rear portion is sealed by the 
beads 78 and 88 on transducer 20. To provide sealing where transducer 22 
passes through support member 80 there is provided a radially extending 
groove 84 in support member 80 within which there is provided an O-ring 86 
engaging transducer 22. Groove 84 is made substantially deeper than 
necessary to accomodate O-ring 86, and is filled with a viscous fluid, 
such as petroleum jelly, to allow for movement of O-ring 86 radially 
within groove 84. This provides a relatively moveable seal between 
transducer 22 and support member 80. This moveable seal is required 
because of the adjustable nature of the transducer orientation, as will be 
further described. Conical shell 128 is sealed to housing member 76 by a 
tightly fitting thread at the junction between these two parts. 
At the end of housing portion 72 opposite conical shell 128 there is 
provided a mounting member 90 for connecting the first housing portion 72 
to the second housing portion 74. Mounting member 90 may be made of 
aluminum or similar material, and includes an axially extending 
cylindrical section 92 which extends within housing portion 74. Mounted on 
cylindrical section 92 is a retaining ring 94. This retainer ring also 
loads the O-rings 96 and 98 under compression to permit pivotal adjustment 
of transducer 20 about transducer 122. The loading of said O-rings between 
100, 104 and 94 adds to the sensitivity of pivotal adjustment, and keeps 
the pivot adjusting screws under tension maintaining any adjustment that 
is made. Flange 104 is fixedly connected, for example, by screws to 
housing member 102 of housing portion 74. Also provided on housing portion 
74 is a retaining sleeve 105 which has a central cylindrical bore 108 
which is closely fitted around transducer unit 22 and secured thereto by 
means of one or more set screws 110. Sleeve 105 is mounted to housing 
member 102 by screws 112. As illustrated in FIG. 2, transducer unit 22 
extends from mounting sleeve 105 through a central bore 100 in mounting 
member 90 and thence through mounting member 80 and transducer 20 to 
project into the cavity which is fluid filled and enclosed by conical 
shell 128. Transducer 122 in unit 22 is held stationary in place. Pivotal 
adjustment is made to align the therapeutic transducer to transducer 122. 
Transducer unit 22 is axially adjustable to position the focal point of 
the radiating transducer 122 to have an axial location which corresponds 
to the location of focal point 21 of transducer 20. By reason of the 
pivotal connection between housing member 72 and housing member 74, there 
may be provided a pivoting adjustment between housing members and 
therefore between the axis of radiation from transducer 20 and transducer 
122. This adjustment is effected by the use of set screws 114 threaded 
into flange 104. Typically three such set screws may be arranged at 
90.degree. intervals around flange 104. As illustrated mounting member 90 
also includes hardened steel pads adjacent set screws 114 for preventing 
distortion of the mounting member by the action of the set screws. 
Transducer unit 22 includes a radiating transducer 122 which consists of a 
spherical shell portion of piezoelectric material having inner and outer 
radial surfaces coated with conductive material and connected to the inner 
and outer conductors of the diagnostic signal input connector 116. The 
transducer 122 may alternatively comprise a flat disk, possibly with an 
acoustically focusing lens. The diagnostic transducer is within a metallic 
tube 120 within which there may be provided an ultrasonic dampening 
material 123 to provide for broadband operation of the transducer. 
Typically, the transducer operates at a nominal frequency of 7.5 Mhz. to 
accommodate the Sonometrics Ophthalmoscan unit, which has a broadband of 
operation by reason of relatively short pulses of about 0.25 microseconds. 
The transducer 22 has a central bore including a stepped portion which 
receives the lens mounting metallic tube 24 and a front portion 124 which 
allows light to pass through the diagnostic transducer 122. Tube 24 
includes at its forwrd end adjacent to the radiating portion of transducer 
122 a lens 126 which is designed to focus light, provided through optical 
coupling member 118 from a fiber optic light path 34 connected thereto, 
into a light beam which passes in a fluid medium in the direction of the 
radiated ultrasonic beam from diagnostic transducer unit 22. As 
illustrated in FIG. 2 there is provided a connector 116 for connecting the 
diagnostic transducer to the Ophthalmoscan unit 64. There is also provided 
a connector 136 on matching network 58 for connecting the power amplifier 
56 to the matching network and therapeutic transducer. Also provided is a 
connector 134 for sampling the power provided by the matching network to 
the therapeutic transducer and providing that sample over lead 60 to 
oscilloscope 50. 
As becomes evident from the foregoing description the transducer assembly 
18 includes apparatus for providing three radiations, the therapeutic 
ultrasonic beam from transducer 20, the diagnostic ultrasonic beam from 
transducer unit 22 and a light beam provided through lens 126 which is 
supplied over the fiber optic conduit 34. Ideally all of these radiations 
are along the same axis, which is the axis of the transducer assembly 18, 
in particular, the circular and conical parts thereof. 
Prior to use of the transducer assembly 18, the two housing portions 72 and 
74 are adjusted so that the beams from transducers 20 and 22 will be along 
a common axis. In particular, using a conventional beam detecting system, 
the direction of radiation from each of the transducers is measured and 
set screws 114 are adjusted so that the beams have a common axis. This 
adjustment causes the pivoting of housing portions 72 and 74 with respect 
to each other at the junction between the housing portions which is 
bridged by O-rings 96 and 98. Housing member 72 has an enlarged central 
bore 100 at the rear mounting member 90 and has a special adjustable 
sealing member formed by O-ring 86 and toroidal groove 84 to permit the 
pivoting of transducer unit 22 within housing member 72. 
An additional adjustment may be performed to provide for a common focal 
point of therapeutic transducer 20 and diagnostic transducer unit 22. In 
particular, the axial location of diagnostic transducer unit 22 can be 
adjusted by loosening set screws 110 and axially sliding transducer unit 
22 to a position such that it has a common focal point with therapeutic 
transducer 20, for example, focal point 21. 
Following adjustment of the axial positions and orientations of the housing 
members to achieve coincidence of the radiated beams on a common focal 
point and along a common axis, the assembly may be prepared for use by 
placing a membrane 132 over the opening 130 at the end of conical shell 
128 after the cavity formed within shell 128 is appropriately filled with 
fluid to efficiently conduct ultrasonic radiation from transducers 20 and 
22. 
When used in connection with eye treatment, the patient is prepared by 
adhesively attaching a drape having a central aperture to the skin around 
the eye to be examined and treated. The drape is filled with a fluid and 
the transducer assembly, in particular, end 130 is placed within the fluid 
so that there is a continuous fluid path through the fluid filled cavity 
formed by conical shell 128, through the fluid within the drape, and into 
the patient's eye. When the transducer assembly is so arranged, and the 
transducer assembly is mounted on a conventional scanning apparatus, it 
becomes possible for the practitioner to adjust the position and 
orientation of the transducer for purposes of generating A scan and B scan 
images on the Ophthalmoscan unit 64 thereby to explore the tissue 
structure of the eye of the patient being treated. Once the tissue 
structure has been so explored and images displayed to the practitioner, 
it may be desirable to use ultrasonic beams to perform noninvasive 
treatment for the eye. 
The transducer assembly 18 shown in FIG. 2 is particularly useful by reason 
of the fact that the therapeutic transducer 20 radiates a converging beam 
of acoustical energy which has a high energy density only in the vicinity 
of the focal point 21 of the beam. Accordingly, the transducer radiation 
from transducer 20 will pass with relatively low radiation power density 
through the fluid within shell 128, the fluid within the drape, and 
portions of tissue between focal point 21 and opening 130. Energy will be 
highly concentrated only at the focal point 21, and can develop at that 
point a localized heating or other physical effect, to provide tissue 
modification at the focal point and thereby provide noninvasive ultrasonic 
treatment to portions of the eye or other organ to which the radiation is 
applied. During the radiation of a therapeutic ultrasonic beam, the 
transducer assembly 18 is held stationary and oriented toward the point at 
which tissue modification is to be made. The power control section 10 
shown in FIG. 1 provides a controlled, for example 5 second, burst of high 
energy acoustic radiation which provides the therapeutic effect. The A 
scan display on the Ophthalmoscan unit can be used by the physician for 
purposes of locating focal point 21 precisely at the tissue to be treated 
by the therapeutic radiation beam. 
During the surgical procedures, the light beam provided through lens holder 
24 and lens 126 can be radiated into an eye being treated and provide an 
additional means for the physician to observe the point at which the 
surgical radiation is to impinge. Thus, the physician can not only see the 
A scan and B scan ultrasonic display of the eye tissue, but can also 
observe, from the side of transducer assembly 18, the point of orientation 
of the light beam provided through lens 126. 
The arrangement for the transducer, which is shown in FIG. 2, facilitates 
surgical procedures including observation of surgical effects during the 
process of ultrasonic surgery. The effects of the therapeutic ultrasonic 
radiation from transducer 20 can be visually observed with the assistance 
of the light beam radiated through tube 24 and focused by lens 126. In 
addition to the visual observation, changes in tissue characteristics can 
be observed by observation of the displays of A scan and B scan ultrasonic 
echoes which are radiated and received through diagnostic transducer 
assembly 22. As an alternative to projection of light through optical 
channel 24, it is also possible to provide another separate light source 
and arrange for optical observation of tissue structure changes by 
modifying lens 126 to allow visual observation of tissue structure through 
optical channel 24. 
An alternate surgical procedure using the transducer assembly 18 of FIG. 2 
is to have the surgeon hold the transducer assembly 18 in his hand during 
examination and treatment. In this case, the physician can use the A scan 
display for purposes of tissue examination and for positioning and 
orienting transducer assembly 18. 
FIG. 5 is a cross sectional view of an alternate conical shell 160, which 
can be used instead of conical shell 128 on the transducer assembly 18 of 
FIG. 2. Conical shell 160 is adapted to thread onto housing member 76 in 
the same way as conical shell 128. Shell 160 is provided with a membrane 
172 which is stretched across the conical surface and retained by O-rings 
174 and 168 in circular grooves 170 and 166. The cavity within conical 
shell 160 is filled with fluid to surround transducer 20 and provide an 
efficient conductive medium for ultrasonic radiation. Shell 160 is 
provided with a fluid coupling 176 through which the cavity within the 
shell may be filled with fluid, for example, sterile distilled or saline 
water. In operation fluid under pressure may be supplied to shell 160 
through a control valve or stopcock 177. The pressure of the fluid will 
cause the end of membrane 172 to bulge from the opening 164 at the apex of 
conical shell 160 as shown at 172' and 172". Stopcock 177 serves to 
stabilize the pressure and hold the bulge constant. This bulging of the 
membrane enables the direct application of conical shell 160 to the 
surface of an eye without the interposition of a fluid bath in a surgical 
fluid retaining drape surrounding the eye as described above. Accordingly, 
the draping process is unnecessary, and by direct application of a 
hand-held transducer assembly with conical shell 160 to an eye the 
physician may perform both diagnostic and therapeutic ultrasonic radiation 
operations. As illustrated, the shell 160 has a relatively small aperture 
164 which is located close to the focal point 162 of the radiation from 
transducer 20. This arrangement is particularly useful for treating areas 
close to the surface of the eye, for example, in the vicinity of the lens. 
It will be recognized, however, that by providing a larger aperture 164 
which is further spaced from the focal point 162 of the transducer 20 it 
is possible to provide a greater spacing of the focal point of transducer 
operation from the end of shell 160 and therefore from the surface of the 
eye, for example, for surgery on the retina of the eye. 
While there have been described what are believed to be the preferred 
embodiments of the present invention, those skilled in the art will 
recognize that other and further modifications may be made thereto without 
departing from the spirit of the invention and it is intended to claim all 
such changes and modifications as fall within the true scope of the 
invention.