Flexible elongate device having forward looking ultrasonic imaging

A flexible elongate device comprising a flexible elongate member having proximal and distal extremities, means mounted on the distal extremity and having a cavity therein, a transducer disposed in the cavity, support means for mounting the transducer so that energy omitted from the transducer is propagated in a forward direction, and oscillatory means connected to said support means for parting angular motion to the support means to repeatedly sweep that through an angle, said oscillatory means including at least one shape memory element and means for repeatedly energizing and deenergizing the shape memory element.

This invention relates to a flexible elongate device having forward looking 
ultrasonic imaging. 
Ultrasonic probes and catheters have heretofore been provided which are 
capable of ultrasonic imaging. However, in most of those prior art 
devices, the imaging was in a direction transverse to the longitudinal 
axis of the probe or catheter. In U.S. Pat. No. 4,895,158, there is 
disclosed an ultrasonic probe which looks in a forward direction or 
distally of the tip of the probe. However, the device is relatively large 
and bulky and is disclosed as being useful only for the coelom of a body. 
There is therefore need for a mechanism which can be used in connection 
with flexible elongate devices of a very small size and which is provided 
with forward looking capabilities. 
In general, it is an object of the present invention to provide a flexible 
elongate device of a relatively small size which has forward looking 
ultrasonic imaging capabilities. 
Another object of the invention is to provide a device of the above 
character which utilizes at least one shape memory element for the 
actuation mechanism. 
Another object of the invention is to provide a device of the above 
character which can be utilized for viewing forwardly in small vessels 
such as arteries and veins. 
Another object of the invention is to provide a device of the above 
character which can be utilized for imaging the walls of the chamber of 
the heart. 
Another object of the invention is to provide a flexible elongate device of 
the above character in which various types of transducers can be utilized.

In general, the flexible elongate device is comprised of a flexible 
elongate member having proximal and distal extremities. A transducer 
element is disposed in the distal extremity. Support means is provided for 
mounting the transducer element. Means is provided for supplying energy to 
the transducer element. Oscillatory means is connected to the support 
means for imparting angular motion to the support member to cause the 
transducer element to sweep through an angle. The oscillatory means 
includes at least one shape memory element. Means is provided for 
supplying energy to the shape memory element. 
More particularly, as shown in the drawings the flexible elongate device 11 
consists of a flexible elongate member 12 having proximal and distal 
extremities 13 and 14. The flexible elongate member 12 can have a size 
ranging from a diameter of 0.032 inches to 0.125 inches and preferably 
approximately 0.095 inches. It can have a suitable length, as for example 
ranging from 150 to 170 centimeters. A handle 16 adapted to be held by the 
human hand is provided on the proximal extremity 13. 
The flexible elongate member 12 can be formed in a conventional manner. For 
example, it can be formed of a suitable material such as a plastic with a 
stainless steel braid therein which can be utilized as a torque tube for 
supplying rotational motion from the proximal extremity to the distal 
extremity 14. To impart additional flexibility to the distal extremity, 
the distal extremity 14 can be formed of a coil spring in a manner well 
known to those skilled in the art. A tip 21 is secured to the distal 
extremity 14 and is formed of a material which will transmit the desired 
energy in a forward direction distally of the tip 21. The tip 21 encloses 
a cylindrical cavity 22 and has a hemispherical or a rounded forward 
extremity 23. A transducer 26 is disposed within the cavity 22 and is 
carried by a support member 27. The transducer 26 can be of any 
conventional type and size, as for example an ultrasonic transducer having 
a width of 0.005" and a length of 0.010" to 0.015". When this is the case, 
the tip 21 is formed of a material which is transparent to ultrasonic 
energy and has an impedance which matches the transducer and which also 
matches the body fluid, as for example blood in which the tip 21 may be 
disposed. 
An oscillatory linkage mechanism 31 is provided for moving the support 
member 27 with the transducer 26 thereon through an angle across the 
rounded extremity 23. This mechanism consists of a support arm 32 which is 
pivotally mounted on a shaft 33 extending transversely of the tip 21. The 
arm 32 is provided with an extension 34 which extends at a suitable angle 
with respect to the arm 32. This angle is substantially equal to the angle 
through which the transducer 26 is to be moved, as for example an angle of 
70.degree. from a line parallel to the arm 32. This extension arm or 
rocker arm 34 is pivotally connected to a link 36 at 37 which has its 
other end pivotally connected by a pin 38 to a circular movable member or 
disk 39 slidably mounted for longitudinal or axial movement within the 
cavity 22. 
Means is provided on opposite sides of the movable disk 39 for moving the 
same axially in the cavity 22 and consists of at least one shape memory 
element and means for activating and deactivating the shape memory 
element. In this embodiment of the invention the means consists of first 
and second coil springs 41 and 42 disposed within the cavity 42 on 
opposite sides of the disk 39 and having one end of each of the same 
engaging the respective side of the slidable disk 39. The springs 41 and 
42 are formed of a suitable shape memory alloy such as Nitinol which have 
been programmed whereby when they become activated, as for example by the 
application of heat thereto as hereinafter described, they expand and 
conversely when energy is no longer supplied to the same, they become soft 
and easy to compress. 
The other end of the first spring 41 engages a disk 46 which is mounted in 
a fixed position within the cavity 22 whereas the other end of the second 
spring 42 engages another disk 47 mounted in a fixed position in the 
cavity 22 on the other side of the slidable disk 39. A hole 48 is provided 
in the disk 46 to accommodate the movement of the link 36. Conductors 51 
are provided which extend from the handle 16 through the proximal 
extremity 13 of the flexible elongate member 12 up through a hole 52 
provided in the fixed disk 47 and then through a hole 53 provided in the 
slidable disk 39 and extend along the link 36, the extension arm 34 and 
the arm 32 to both sides of the transducer 26 so that electrical energy 
can be supplied to the transducer 26 and removed from the transducer 26. 
An additional group of conductors 56 is provided for making electrical 
connections to opposite ends of the first and second springs 41 and 42 as 
shown in FIG. 2 and extend from the handle 16 and through the flexible 
elongate member 12 through the hole 57 provided in the fixed disk 47 and a 
hole 58 in the slidable disk 39. The conductors 51 and 56 are connected 
into a cable 61 which is connected into a connector 62. The connector 62 
is connected to a mating connector 63 which is connected to a cable 64 
connected to a controller 66. 
The controller 66 can include circuitry of the type as shown in FIG. 4 for 
supplying energy to the first and second springs 41 and 42 so that these 
small springs 41 and 42 can be activated and deactivated in short periods 
of time in the range of a millisecond to obtain oscillatory movement 
within the range of 100 to 200 Hz but which range could be extended from 
10 to 1,000 Hz. Thus there is provided an oscillator 71 that provides an 
oscillatory output of the desired frequency range from 10 to 1,000 Hz in 
the form of a square wave on an output 72. This output is connected 
through a resistive divider 73 consisting of a series resistors R1 
connected to a junction 74 and an adjustable resistor R2 connected between 
the junction and ground and connected to the input of an operational 
amplifier 76 which has its output connected to the base of a transistor Q1 
having the collector connected to a source of a suitable voltage, as for 
example five volts as indicated by V+ and its emitter connected to the 
minus input of the amplifier 76. The emitter is also connected to one side 
of the spring 41 and the other side of the spring 41 is connected to 
ground as shown. Similarly, the output 72 from the oscillator 71 is 
connected through an inverter 81 to invert the square wave by 180.degree. 
and supplies the same through a resistive network 82 similar to the 
resistive network 73 consisting of a series resistor 83 connected to a 
junction 84 through an adjustable resistor R4 to ground. The junction 84 
is also connected to the plus terminal of an operational amplifier 86 
which has its output connected to the base of a transistor Q2 which is 
connected to a suitable V+ voltage as in Q1 and has it emitter connected 
to the minus terminal of the operational amplifier 86. The emitter is also 
connected to one end of the spring 42 and the other end of the spring 42 
is connected to ground as shown. Thus it can be seen that an inverted 
output is supplied to the spring 42 whereas a noninverted output from the 
oscillator 71 is supplied to the spring 41. Controls (not shown) can be 
provided in the controller 66 or in the handle 16 for controlling the 
output frequency from the oscillator 71 and for also for controlling the 
two currents supplied to the springs 41 and 42 to cause the rapid 
oscillation of the transducer 26 across the face of the rounded extremity 
23. 
During the time this oscillation is occurring, signals are supplied from 
the signal generator 91 through a cable 92 through mature connectors 93 
and 94 connected to a cable 96 connected to the handle 16 and thence 
through the conductors 51 to the transducer 26 which converts the 
electrical signals to ultrasonic signals. The ultrasonic signals are 
directed forwardly or axially in a scanning motion through the rounded 
extremity 23 to see what is being encountered as the flexible elongate 
device 11 is advanced into a vessel, as for example an artery or a vein. 
Reflections or echoes which are produced will be picked up by the 
transducer 26 and converted to electrical signals which are returned to 
the signal processor 91 and displayed on a video display 92. 
Because the springs 41 and 42 have such a low mass, they can be energized 
and deenergized to cause expansion by one of these springs and relaxation 
of the other spring and thereafter expansion of the other spring and 
relaxation of the one spring to cause rapid oscillatory movement of the 
slidable disk 39 within the tip 21. This rapid oscillatory sliding 
movement of the disk is translated through the lever arm linkage to cause 
rapid oscillatory or harmonic motion of the transducer 26 across the face 
of the rounded extremity 23. It should be appreciated that other waveforms 
such as a substantially linear ramp or triangular wave may be used to 
drive the springs to cause the angular velocity of the transducer to vary 
during each cycle. 
The flexible elongate device can be introduced into a body cavity, as for 
example a vessel in a patient such as an artery or a vein in a 
conventional manner and advanced therein by use of the handle 16. It 
should be appreciated that in connection with the present invention 
steering capabilities can be provided for the distal extremity 14 to 
facilitate navigation of tortuous vessel such as that described in U.S. 
Pat. No. 5,238,005. 
Although the present invention has been described principally in connection 
with the use of ultrasound, it should be appreciated that the principles 
of the present invention can be utilized in other flexible elongate 
devices in which it is desired to provide diagnostic and therapeutic 
procedures forward of the distal extremity of the device. For example such 
rapid oscillatory motion can be utilized in connection with an optical 
device to provide diffuse heating forward of the distal extremity rather 
than pin point heating. 
Another embodiment of a mechanism for causing rapid oscillatory or harmonic 
motion of a transducer at the distal extremity of a flexible elongate 
device 11 is shown in FIG. 5. It in many respects is similar to the 
mechanism shown in FIG. 2 but the linkage provided in FIG. 2 has been 
replaced by a rack and pinion assembly 96 consisting of a rack 97 carried 
by a rod 98 extending through a hole 99 in the fixed disk 46 and secured 
at 100 to the movable disk 39 and the rack 97 has its teeth engaging a 
pinion 101 rotatably mounted on a shaft 102 extending transversely of the 
tip 21. The pinion 101 has a support arm 103 mounted therein which 
corresponds to the support arm 32 and is connected to the support member 
27 carrying the transducer 26. 
The operation of the embodiment of the invention shown in FIG. 5 is very 
similar to that shown in FIG. 2 in that the oscillatory motion of the 
movable disk 39 is translated to the transducer 26 by rack and pinion 
assembly 96 rather than the linkage mechanism 31 shown in FIG. 2. It can 
be seen as the springs 41 and 42 are energized and deenergized in 
accordance with the circuitry shown in FIG. 4, that the rack 97 will be 
reciprocated back and forth to cause a reciprocatory movement of the 
pinion 101 to cause the arm 103 carried thereby to move the transducer 26 
across the face of the rounded extremity 23 in a manner substantially 
identical to that described in conjunction with the embodiment shown in 
FIG. 2. 
The transducer 26 can have a suitable size, as for example a width of 0.005 
inches and a length of 0.010 to 0.015 inches. 
Still another embodiment of a mechanism for achieving oscillatory motion of 
a transducer at the distal extremity of a flexible elongate element is 
shown in FIG. 6 in which a flexible elongate element 106 is provided which 
has a distal extremity 107 having a rounded hemispherical lens 108 mounted 
thereon which is transparent to ultrasonic energy and which is formed of a 
material which is impedance matched to the ultrasonic energy and to a 
liquid, as for example blood in which it is immersed. A cylindrical cavity 
111 is provided proximal of the lens 108. A support member 112 is 
pivotally mounted on a shaft 113 mounted transversely of the distal 
extremity 107 and carries a transducer 116 of a suitable type such as an 
ultrasonic transducer which faces in a direction towards the hemispherical 
lens 108. Conductors 117 and 118 are connected to the front and back sides 
of the transducer and extend to the proximal extremity (not shown). 
Means is provided for imparting rocking or oscillatory motion of the 
support member 112 so it rotates through a suitable angle, as for example 
an angle of 60.degree. to 90.degree. and consists of a tension spring 121 
which has one end 122 connected to one end of the support member 112 and 
has the other end 123 secured to a stationary disk 124 mounted in the 
cavity 111 and secured to the flexible elongate member 106 in a suitable 
member such as by an adhesive (not shown). 
A shape memory element 126 formed of a suitable material such as Nitinol 
and having a negative coefficient of expansion has one end 127 secured to 
the support member 112 opposite the end where the end 122 of the spring 
121 is secured. The element 126 extends through a flexible sleeve 128 
which extends to the disk 124 and is mounted thereon. It should be 
appreciated that if desired, the sleeve 128 can be omitted. The other end 
129 of the shape memory element 126 is secured to the fixed disk 124 by 
suitable means such as an adhesive and is connected to a conductor 131 
which extends to the proximal extremity of the flexible elongate member 
106. The other end 127 is also connected to a conductor 132 extending 
through a hole 133 in the disk 124 and also extends to the proximal 
extremity (not shown) of the flexible elongate member 106 where it can be 
connected to the power supply and controller so that oscillatory current 
can be supplied to the shape memory element 126. The conductors 117 and 
118 can extend through the same hole 133 as shown. The application of 
electrical energy to the element 126 will cause the element 126 to shrink 
to pull that end of the support member to which it is attached in a 
proximal direction against the yieldable force supplied by the spring 121 
to cause the transducer 116 to be moved through a desired angle, as for 
example 60.degree. to 70.degree.. As soon as the element 126 is 
deenergized, it will cool and relax and permit the transducer 116 to be 
returned to its initial position shown in FIG. 6 under the force of the 
spring 121. Thus, it can be seen that repeated energization and 
deenergization of the shape memory element 126 will cause oscillatory or 
harmonic motion of the transducer 116 to cause ultrasonic energy to be 
transmitted through the hemispherical lens 108 in a sweeping motion to 
sweep the space immediately in front of the hemispherical lens 108 so that 
it echos or reflections which are created can be received by the 
transducer 116 and supplied to a signal processor and generator 91 of the 
type hereinbefore described and the results displayed on a video display 
92. 
From the foregoing it can be seen that there has been provided a flexible 
elongate device 11 which can be made in very small sizes so that it can be 
introduced into small vessels, as for example the arterial and venus 
vessels of the heart to permit forward looking imaging in the vessel. Such 
forward looking imaging will give the conformation of the stenosis 
occurring in the vessel. It should be appreciated that the flexible 
elongate device of the present invention can be utilized in conjunction 
with other instruments or devices. For example it could be used with a 
laser angioplasty catheter to ensure that the laser beam be properly 
directed within the vessel. The mechanisms which are provided to achieve 
the oscillatory motion are of the type which are very compact and can be 
utilized in applications having very little space, as for example the 
distal extremity of small flexible elongate devices such as catheters and 
guide wires.