Abstract:
A rotationally vibrating imaging catheter and method of utilization has an array of ultrasound or optical transducers and an actuator along with signal processing, display, and power subsystems. The actuator of the preferred embodiment is a solid-state nitinol actuator. The actuator causes the array to oscillate such that the tip of the catheter is rotated through an angle equal to or less than 360 degrees. The tip is then capable of rotating back the same amount. This action is repeated until the desired imaging information is acquired. The rotationally vibrating catheter produces more imaging points than a non-rotating imaging catheter and eliminates areas of missing information in the reconstructed image. 
     Rotationally vibrating catheters offer higher image resolution than stationary array catheters and greater flexibility and lower costs than mechanically rotating imaging catheters. 
     The rotationally vibrating array carried on a catheter is vibrated or rocked forward and backward to allow for acquisition of three-dimensional information within a region around the transducer array. 
     The addition of adjunctive therapies to the imaging catheter enhances the utility of the instrument. Examples of such therapies include atherectomy, stent placement, thrombectomy, embolic device placement, and irradiation.

Description:
PRIORITY CLAIM 
   This application is a continuation-in-part of U.S. patent application Ser. No. 09/690,795, filed on Oct. 17, 2000, now U.S. Pat. No. 6,592,526 which is a continuation-in-part of U.S. patent application Ser. No. 09/632,317, filed on Aug. 4, 2000, now abandoned, which is a continuation-in-part of U.S. patent application Ser. No. 09/236,936, filed on Jan. 25, 1999, now U.S. Pat. No. 6,110,121 the entirety of which are hereby incorporated herein by reference. 

   FIELD OF INVENTION 
   This invention relates to improvements in devices for intravascular ultrasound (IVUS) and optically guided catheter systems. 
   BACKGROUND OF INVENTION 
   Intravascular ultrasound is a rapidly evolving imaging technique most commonly employed in coronary and iliofemoral arteries. The technique has the potential to facilitate the study of aneurysm progression, atherosclerosis or dissection and to outline the effect of endovascular intervention in more detail than angiography. 
   The presently used intravascular ultrasound systems fall into two categories: stationary electronic systems and mechanically driven rotating transducer systems. In both systems, an acoustic element or transducer is used to transmit a signal, which impinges upon, and reflects from, surfaces of different acoustic densities, which the signal encounters. An acoustic transducer receives the reflected wave. These data are sent to a processing system via an electrical cable where they are manipulated and displayed as an image. The systems are mounted to catheters, or axially elongate structures, which are routed through body lumens such as arteries to reach the site of imaging. 
   The non-rotating or stationary catheter of the stationary electronic system houses an array of small acoustic elements, which are positioned cylindrically at the catheter tip. After positioning the catheter in a vessel, body lumen or cavity, subgroups of acoustic elements together generate an echo image. The spacing between the acoustic elements in the transducer array creates areas where the acoustic signal is neither transmitted nor received. When the data is processed, gaps of missing information occur, resulting in a poor quality image. The advantage of the stationary electronic system is that the catheter is very flexible and a central lumen is available for guidewire insertion. No distortion of the image, due to inhomogeneous mechanical rotation, is present. The stationary catheters are reliable and inexpensive but produce a poor quality image. 
   The mechanical intravascular ultrasound-imaging catheter comprises a mechanically rotating catheter shaft with a single ultrasound transducer. Either the acoustic element rotates or the acoustic element is stationary and a mirror rotates. In this manner, the acoustic signal is transmitted and received in a continuous 360-degree sweep. There are no gaps in the data and a higher quality image results. Realizing a driving mechanism while keeping the catheter fully flexible and steerable as well as miniature are challenging problems. Distortion of the image due to an unequal rotation of the element or mirror at the catheter tip is a limitation of these systems. Advantages of the mechanical probes include high-resolution imaging and absence of near field artifact. The mechanically rotating devices produce an acceptable image but are unreliable and expensive. 
   Both stationary electronic systems and mechanical systems typically operate with acoustic frequencies from 10 to 30 MHz. 
   Medical interventions are often performed using endovascular techniques. These interventions include balloon dilatation, atherectomy, stent or device placement and removal, drug delivery, thrombolytic therapy, thrombectomy, vessel irradiation, embolic device delivery and thermal therapy by radio waves or microwaves. Guidance of these endovascular interventions is preferably accomplished using intravascular ultrasound imaging. 
   SUMMARY OF INVENTION 
   An embodiment of the invention comprises a catheter comprising an array of ultrasound transducers and actuators along with signal processing, display, and power subsystems. The actuators on the catheter cause the array to oscillate. This allows the array to produce more imaging points of the object to be viewed than a non-rotating or a stationary array. Additional computer processing of the ultrasound data produces an image with a higher resolution than images produced from data from a non-oscillating transducer array. 
   An embodiment of the invention comprises a catheter, or axially elongate structure, which has a distal tip and a proximal end. The catheter optionally comprises a central lumen or a guidewire tip. The central lumen is often used for guidewire passage. It optionally also comprises additional lumens for purposes such as balloon inflation and deflation, stent or embolic device deployment, device retrieval, contrast media or material injection, electromagnetic emissions and drug injection or removal. The distal tip comprises an array of at least one transducer for transmitting ultrasound energy radially outward, an array of at least one transducer for receiving ultrasound signals, and one or more actuators. The transmitting and receiving transducers is optionally the same physical entity. The transmitting and receiving transducers are electrically connected to the proximal end of the catheter by a transmission line, cable or wire bundle, which is electrically connected to a decoder, a power generator, and a display instrument. The actuators are also electrically connected to the proximal end of the catheter with a transmission line, cable or wire bundle, which is electrically connected to a power supply. The ultrasound transducer array on the distal tip of the catheter transmits and receives ultrasound signals, which are processed by a computer to create an image of the object subjected to the ultrasound signals. 
   The transducer array, located near the distal tip of the catheter, rotates clockwise and then counterclockwise either with the rest of the catheter or, preferably independent of the catheter. The array is rotated through an angle equal to or less than 360 degrees. Most advantageously, the array is rotated sufficiently to fill in the information gaps but not more than required to minimize the requirements of the actuator and linkages. The array is then capable of rotating backwards the same amount. The net motion is a rotating oscillation or a vibration. The oscillating array is optionally covered with a non-oscillating shield. Preferentially, the array will be rotated much less than 360 degrees so multiple transducers are required in the array to maintain a full field of view. 
   In one embodiment, the distal tip of the catheter comprises an imaging array that is directed forward as well as the imaging array that is directed radially outward. The forward directed array allows for acquisition of additional information on the vessel distal to the catheter. This is especially useful when the radially outwardly directed array elements are oscillated through too small an angle to gain useful forward-looking information. 
   An embodiment of the invention does not continually rotate. It vibrates rotationally in the same manner as an agitator to gather data to fill in the missing information between array elements. The rotating array allows for imaging of a two-dimensional “slice of pie”—or wedge-shaped segment of the lumen and surrounding tissue. This two-dimensional imaging region is orthogonal to the axis of the array and generally orthogonal to the axis of the catheter. By circumferentially vibrating, the array is caused to move to fill in any gaps in information that exist between adjacent array elements. Lost information between array elements is the reason stationary array systems offer less resolution than rotating transducer systems. 
   Since the movement of the array occurs only near the tip of the catheter, the catheter can be made very flexible up to the point of the array and, thus, able to negotiate tortuous vasculature. Stiff drive cables used for rotational systems would not pass through tight curves and could not function distal to serpentine or highly tortuous vascular pathways. The actuators and array of the present invention can be made very small to accommodate high flexibility requirements of catheters needed to navigate tortuous vasculature and still function. 
   In one embodiment of the present invention, the transducer array is oscillated circumferentially, and in addition, rocked back and forth along the axis of the catheter to provide imaging information in three-dimensional space around at least a portion the tip. Actuators rotate the array circumferentially as well as axially, with respect to the axis of the catheter, to create a pyramidal-shaped imaging volume with a spherical exterior around each transducer of the array. The three-dimensional information is also obtainable in a spherical volume around the transducer array when it is designed with overlapping fields of view. 
   The motion of the imaging transducer array is substantially independent of the motion of the catheter. It is preferable that the catheter remains stationary when the imaging transducer array is in motion so that a point of reference or baseline is established. The stationary catheter is generally preferable for therapeutic methodologies accomplished under the guidance of the imaging system. 
   In one embodiment of the invention, the transducer array is oscillated circumferentially at a different rate than the rate at which it is rocked back and forth along the plane including the longitudinal axis of the catheter. Different oscillation rates ensure that, in the embodiment where the two rocking motions are uncoordinated, the transducers image the entire potential field rather than just one region. Uncoordinated movement is preferable when control and positioning of the transducer array along one or more axis is difficult or expensive. 
   In yet another embodiment where the circumferential and axial rocking motions are coordinated, it is preferable to minimize the total amount of motion of the transducer array to minimize inertial effects and energy requirements. Thus, it is preferable to rotate in one direction (circumferential for example) fully, increment the position of the second direction (axial plane for example) and rotate the circumferential plane back to its initial position. By repeating this motion, a zig-zag or serpentine pattern is established throughout the potential imaging region to provide total or maximal coverage. Once the axial movement has reached its maximum, the axial actuator moves the transducer array back to its starting position. 
   General medical or endovascular use of the vibrating imaging array permits three-dimensional imaging to occur without the need to move the catheter or array as is required for 3-D pullback techniques. The events that are being monitored are, in some cases, generally static, as in a peripheral blood vessel, or the events are more dynamic such as valve and wall motion in the heart, itself. Static imaging, or that used to guide therapy, can use a slower image refresh rate. Thus, for example, an image created by 256 circumferential lines of resolution by 256 axial planar lines of resolution would want to refresh quickly enough to record the event being monitored. For the generally static system, the system might cycle back and forth circumferentially at 100 Hz, thus making a complete axial planar traverse in 1.28 seconds. Refresh rates as slow as one every five or ten seconds are also useful in certain applications. Such image refresh rates are appropriate for many medical applications. In the heart or during device deployment, however, it is generally appropriate to oscillate more quickly so that a full image is obtained in time frames ranging from less than 0.10 second to around 1.0 second. 
   The preferred embodiment for vibrating or agitating the distal tip of the catheter is a nitinol actuator or sets of nitinol actuators mounted to cause movement of the transducer array. When the nitinol is exposed to electrical current, it changes dimensions due to resistive heating. When the electric current is removed, the nitinol returns to its original dimensions. Allowance for hysteresis should be made to account for differences in the heating and cooling curves of the nitinol. By counter-attaching the actuators, they can be alternately activated and deactivated causing the transducer array to alternately vibrate clockwise and then counterclockwise or to pivot forward and backward axially. This type of actuator is used for back and forth motion of the array along the axis of the catheter as well as circumferential motion. The actuator set, in one embodiment, is built with separate actuators or as a single system capable of moving the array through two-dimensions to create the three-dimensional image. Counter-attached actuators could also be replaced with a single actuator using a spring return or other mechanism to ensure correct reverse motion when the power is turned off to the single actuator. 
   In another embodiment, the invention includes apparatus for cutting or excising atheroma, thrombus or other tissue from the interior of the body vessel or lumen. This apparatus comprises an actuator, which may or may not be the same as that which drives the imaging array, and cutting elements that act to cut tissue. The cutting elements are disposed within a window on the side of the catheter to perform directional atherectomy or thrombectomy. The cutting elements, in another embodiment, are also disposed in the forward direction to allow for channeling when the catheter is advanced. The invention also comprises catheter lumen structures and systems to provide suction to assist in the removal of the excised material. 
   In yet another embodiment, the invention comprises apparatus for illuminating the body vessel or lumen with electromagnetic radiation at wavelengths from gamma rays to radio waves. Electromagnetic radiation imaging including that using visible light delivery is accomplished using fiber-optic channels to transmit light in the visible, infrared or ultraviolet range. Ionizing radiation is, in one embodiment, generated from a radioactive source, such as Iridium 192, Iodine 131, Iodine 125, Palladium 109, Strontium 90, Cobalt 57 and Cobalt 60, mounted to the tip of the catheter. Examples of ionizing radiation are electrons, positrons, beta particles, gamma rays and X-rays. A removable shield is optionally provided to allow irradiation only at the desired site. A microwave, X-ray or radio frequency (RF) wave source is also mounted to the tip of the catheter. Power for the X-ray source, microwave or RF transducer is carried through the catheter by an electrical cable, wires or group of wires. 
   In another embodiment, the invention comprises a catheter capable of deploying or retrieving a device such as a stent, balloon dilator or vaso-occlusive material while monitoring the deployment or its result with the imaging array. In this embodiment, the array might be internal to the catheter or external to the catheter. The catheter is optionally placed through the lumen of one or more guiding catheters to facilitate maneuvering of the catheter tip through the vasculature or other body lumen. 
   The two-dimensional image is processed and displayed, preferentially in real time, on a two-dimensional monitor or visual output device. The three-dimensional image is processed using standard techniques and displayed, preferentially in real time, by mapping the image to a two-dimensional monitor. Three-dimensional systems such as holographic projectors or a three-dimensional visual output device allow for full three-dimensional modeling. The key to processing of the image is coordination of instant array element position with its one-dimensional ultrasound mapping information. Moving the transducer in one dimension makes a two-dimensional image and moving the transducer in two dimensions results in three-dimensional information. 
   In yet another embodiment, the imaging catheter uses electromagnetic scanning radiation, rather than ultrasound. In a preferred embodiment, the imaging array receives information in the near infrared spectrum. Such devices use technology, which is called optical coherence tomography, and are able to provide images inside the vasculature even though the vessel or body lumen is filled with visibly opaque blood. Exemplary devices that image using near infrared frequencies include U.S. Pat. No. 4,242,706 to McCormack et al., U.S. Pat. No. 5,935,075 to Casscells et al., and U.S. Pat. No. 6,415,172 to Painchaud et al, the entire specifications of each, which are included herein by reference. Combinations of optical and ultrasonic systems are also adaptable to this system. 
   In yet another embodiment, the imaging catheter uses either ultrasound or near infrared to map a feature in the vasculature during placement of an embolic device such as a coil, a stent, a neck bridge, or an amorphous embolic mass. This methodology is particularly suitable for placement of devices in the cerebrovasculature to embolize aneurysms of the cerebrovasculature. Cerebrovascular aneurysms are typically berry-type expansions in a vessel wall that could rupture if not protected against such systemic blood pressure. Rupture of a cerebrovascular aneurysm often can lead to severe neurological dysfunction, disability, or death. Biplanar fluoroscopy is currently used to guide endovascular treatments of these aneurysms but is unable to reveal the nuances of the anatomy. Such nuances, if undetected, can result in improper packing of the aneurysm and ultimately lead to aneurysm rupture or additional therapy. The real-time three-dimensional imaging, in conjunction with embolic device deployment can provide complete information and confirmation of correct placement. A very flexible catheter is required to reach the cerebrovasculature endovascularly since the carotid sinus or vertebral arteries are typically negotiated to reach the circle of Willis where most of the cerebrovascular aneurysms occur. The carotid sinus and vertebral arteries are highly tortuous so only very small and flexible catheters are capable of being placed across this area. The vibrational imaging array of the present invention is capable of such flexibility and small size since a rotating mechanical element is not required to pass from the proximal to the distal end of the catheter in order to move the imaging array. 
   An embodiment of the invention, using a solid-state actuator, is more reliable and less expensive than the rotating catheters with a single acoustic transducer. It can also easily have a central lumen for instrumentation or for a guidewire. In addition, the present invention produces a higher resolution image with fewer gaps in the information than the stationary imaging catheters. This invention creates a high-resolution ultrasound image with higher reliability and less expense than is currently available. This invention has the ability to generate real-time three-dimensional ultrasound images of the region surrounding the acoustic transducers. 
   Another significant advantage of an embodiment of the invention is its ability to navigate tortuous vasculature in order to reach the site of the lesion in the body vessel or lumen. It is, because of its greater flexibility, useful in catheters used to treat lesions of the cerebrovasculature or distal coronary circulation. Interventional devices, delivering therapies such as atherectomy, thrombectomy and irradiation, stent placement or removal, thrombogenic therapy and thrombolytic therapy, guided by this high-resolution ultrasound system, offer improved guidance and precision of placement as well as flexibility at potentially reduced cost and higher reliability than that obtainable from rotating shaft devices. Thus, this invention fills a market demand for a high resolution, reliable and inexpensive imaging and therapeutic catheter. 
   For purposes of summarizing the invention, certain aspects, advantages and novel features of the invention are described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein. 
   These and other objects and advantages of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A general architecture that implements the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention. Throughout the drawings, reference numbers are re-used to indicate correspondence between referenced elements. 
       FIG. 1  shows the imaging area for a stationary imaging catheter positioned in a body lumen, according to aspects of an embodiment of the invention; 
       FIGS. 2A and 2B  show the imaging area for a vibrating imaging catheter of the present invention, positioned in a body lumen, according to aspects of an embodiment of the invention; 
       FIG. 3  is a schematic view of an intravascular ultrasound catheter with optional therapeutic apparatus mounted thereto, according to aspects of an embodiment of the invention; 
       FIG. 4  is an enlarged detail of the distal tip of the imaging catheter of  FIG. 3  illustrating the actuator of the preferred embodiment with a radially directed ultrasound array and an optional forwardly directed ultrasound array, according to aspects of an embodiment of the invention; 
       FIG. 5  is an enlarged sectional view of the distal tip of the catheter of  FIG. 3  illustrating the forward directed and radially outwardly directed ultrasound transducer arrays, electrical connections and the swivel connection, according to aspects of an embodiment of the invention; 
       FIG. 6  is an enlarged view of the distal tip of the catheter of  FIG. 3  illustrating cutting and suction apparatus for an atherectomy or thrombectomy system, according to aspects of an embodiment of the invention; 
       FIG. 7  is an enlarged view of the distal tip of the catheter of  FIG. 3  illustrating a radio frequency, X-ray or microwave wave source, according to aspects of an embodiment of the invention; 
       FIG. 8  is an enlarged sectional view of the distal tip of the catheter of  FIG. 3  illustrating an ionizing radiation source and an optional shield or shutter, according to aspects of an embodiment of the invention; 
       FIG. 9  is an enlarged view of the distal tip of the catheter of  FIG. 3  illustrating a fiber-optic transmission system, according to aspects of an embodiment of the invention; 
       FIG. 10  is a sectional view of the distal tip of a catheter with an imaging array comprising an ultrasound transducer, which is oscillating circumferentially as well as axially, according to aspects of an embodiment of the invention; 
       FIG. 11  illustrates the imaging area of a transducer oscillating circumferentially according to aspects of an embodiment of the invention. 
       FIG. 12  illustrates the imaging area of a transducer oscillating longitudinally along the axis of the catheter, according to aspects of an embodiment of the invention; 
       FIG. 13  illustrates the imaging volume of a single transducer array oscillating circumferentially approximately 90 degrees and axially approximately 60 degrees, according to aspects of an embodiment of the invention; 
       FIG. 14  illustrates the three-dimensional imaging volume of a transducer array of four transducers oscillating circumferentially 90 degrees and axially 60 degrees relative to the axis of the catheter, according to aspects of an embodiment of the invention; 
       FIG. 15  is a sectional view of a catheter tip illustrating an inflation lumen, a collapsed dilatation balloon and a collapsed stent, according to aspects of an embodiment of the invention. The catheter also includes the transducer array and actuators for three-dimensional imaging of the body lumen or cavity; 
       FIG. 16  is a view of the catheter tip of  FIG. 15  with the dilatation balloon and stent expanded, according to aspects of an embodiment of the invention; and 
       FIG. 17  illustrates a sectional view of the catheter tip illustrating deployment of an embolic coil into an aneurysm, according to aspects of an embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention herein described is an ultrasound imaging and treatment catheter comprising a rotationally vibrating array of ultrasound transducers. An embodiment of the catheter allows the flexibility and cost effectiveness of a conventional stationary ultrasound-imaging catheter but has superior image data gathering capabilities as is illustrated in  FIGS. 1 ,  2 A, and  2 B. 
     FIG. 1  illustrates, in cross section, a distal tip of a stationary imaging catheter  102  imaging a body lumen  100 . The body lumen  100  has an inside surface irregularity  110  on a body lumen wall  101 . The imaging catheter  102  comprises a plurality or array of ultrasound transducers  104 , a plurality of fields of view or imaging areas  106  and a plurality of blind spots or blind areas  108 . Examples of body lumens include arteries, veins, ureters, the bladder, the urethra and biliary ducts. The transducers  104  are placed circumferentially around the tip  102 . Each transducer  104  transmits ultrasound energy and receives reflected ultrasound energy within its field of view  106 . The blind spots  108  are areas where no ultrasound energy is transmitted nor is any reflected ultrasound energy received. Most of the illustrated lumen irregularity  110  is in one of the blind spots  108 . After data from the transducers  104  is processed to create a visual image, the blind spots  108  correspond to areas of no or missing information, resulting in a poor image. 
   Referring to  FIG. 2A , a circumferentially vibrating portion of a distal tip or end  2  of an imaging catheter images a portion of the body lumen  100 . The vibrating part of the imaging catheter comprises a plurality or array of ultrasound transducers  4 , and a plurality of fields of view or imaging areas  6 . The transducers  4  are placed circumferentially around the tip  2 . Each transducer  4  transmits output ultrasound acoustic waves or energy in response to output or transmission electrical signals and receives reflected ultrasound energy within its imaging area  6 . The surface irregularity  110  of the body lumen  100  is not yet in the imaging area  6  of the transducers  4 . 
   As the array of transducers  4 , located within or on the catheter tip  2  is circumferentially vibrated, as illustrated in  FIG. 2B , the transducers  4  continue to transmit output ultrasound acoustic waves to and receive reflected ultrasound energy from the body lumen  100 . However, each transducer  4  is circumferentially vibrating and shifted from its previous position. The imaging areas  6  overlap, as shown by comparing  FIGS. 2A and 2B . The surface irregularity  110  of the body lumen  100  is in the field of view or imaging area  6  of the transducers  4  after the transducers  4  are circumferentially, or rotationally, vibrated. When the reflection data from the transducers  4  is processed, the resulting visual image has no areas of missing information; thus resulting in a complete image, which is superior to the image produced by a stationary ultrasound catheter. 
   An embodiment of the device, as shown in  FIG. 3 , is a catheter  12  comprising a catheter shaft  14 , a proximal end  16 , the distal end or tip  2 , a central lumen  18  and a wire bundle or transmission line  20 . Additional lumens are optionally added for functions such as dye or fluid injection, fluid removal, electrical or electromagnetic energy delivery, atherectomy control, stent or material deployment or retrieval, balloon inflation and/or deflation. The proximal end  16  comprises a power/data port  24 , a decoder/processor system  26 , an ultrasound-input signal and power supply/controller  28 , an actuator power supply/controller  30 , and a display device or display monitor  32 . The proximal end  16  optionally comprises an inflation port  36 , an inflation lumen  350 , an inflation system  38  and a guidewire  40 . The inflation system  38  may, for example, be a syringe with or without mechanical advantage such as levers or jackscrews. The proximal end  16  further optionally comprises an illumination source  218 , a power source  220  for X-ray, radio frequency or microwave energy and/or a shutter controller  222  for an ionizing radiation source. A connector  226  is optionally provided at the proximal end of the catheter  12  to seal the guidewire  40  entrance against fluid leakage, using a proximal fluid-tight seal  242 , and to allow for attachment of a suction device or vacuum source  224  to remove fluid and excised debris from the body vessel or lumen. Fluid injection to the body lumen is, for example, for purposes such as occlusion, chelation, drug delivery or lysis. 
   Additionally, the distal tip  2  comprises the plurality or array of radially, outwardly directed ultrasound transducers  4 , a circumferential actuator  42  or, in the preferred embodiment, a nitinol circumferential actuator  42 , and a swivel joint or circumferential rotational bearing  44 . The distal tip further optionally comprises the other end of the central lumen  18 , the other end of the guidewire  40 , or a balloon  22 . The balloon  22  is preferably an angioplasty-type balloon suitable for vessel dilation or stent expansion. Such balloons are made from materials such as polyethylene terephthalate (PET), polyimide or other high-strength polymers. The balloon  22  could also be made from elastomeric materials like polyurethane or latex. Such materials are suited for centering the catheter tip in the body lumen or vessel. 
   The distal tip  2  of catheter  12  optionally comprises an array of forwardly directed ultrasound transducers  202 . It also optionally comprises a distal fluid-tight seal  204 , which prevents fluid from passing into the central lumen  18  from the guidewire  40  exit. A cutting apparatus  208  and a fluid suction or vacuum port  206  are also included on the oscillating distal tip  2  of the catheter. The distal tip  2  of catheter  12  further optionally comprises a wave source  228 . Possible wave sources are X-ray emitters, microwave and radio frequency antennas and ionizing radiation sources. 
   As shown in  FIG. 5 , each transducer in the transducer arrays  4  and  202  comprises a plurality of transducer leads  48 . As shown in  FIG. 4 , the circumferential actuator  42  comprises a positive signal/power lead  60  and a negative signal/power lead  62 . The leads  48 ,  60 ,  62  are bundled together in the wire bundle or transmission line  20  which travels the length of the catheter shaft  14  and carries power to the actuator  42  as well as output and reflection electrical signals to and from, respectively, the acoustic arrays  4  and  202 . The central lumen  18  is also shown. 
   Referring to  FIG. 3 , the catheter  12  is positioned in a body lumen or cavity to collect data for an ultrasound image. The lumen wall ideally fits against the outside of the catheter or is liquid-filled in order to efficiently transmit the acoustic waves. In lumens that are not liquid filled, the balloon  22  is optionally disposed to surround transducers  4  and inflated with liquid to fill the space between the catheter tip  2  and wall of the body lumen. The ultrasound array signal and power supply/controller  28  sends output signals to and receives reflection signals from the transducer arrays  4  and  202  over the cable or wire bundle  20 . The information from the ultrasound arrays  4  and  202 , in the form of reflection electrical signals, is sent to the decoder/processor system  26  where the electronic data is processed to compensate for jitter, hysteresis, and uneven rotation. The processed data is sent to the display monitor  32  where the ultrasound image of the body lumen or cavity is displayed. 
   While the ultrasound arrays  4  and  202  are receiving and transmitting information, the circumferential actuator  42  is receiving control signals from the actuator power supply  30 . The actuator control signals are such so as to cause the circumferential actuator  42  to rotate the distal tip  2  of the catheter  12  through an angle of 360 degrees or less and then reverse the rotation through an angle of 360 degrees or less. Once the clockwise and counterclockwise rotation cycle is complete, the cycle repeats until the desired data is collected. 
   In a preferred embodiment, the circumferential actuator  42  utilized to rotationally vibrate the distal tip  2  of the ultrasound-imaging catheter  12  comprises a nitinol actuator. Nitinol is a nickel-titanium alloy, which, in certain embodiments, exhibits a shape memory effect. Shape memory alloys (SMA) are easily deformed and, when heated, they return to their original shape. Shape memory actuators fabricated from thin film or wire can be heated resistively. The small thermal mass and large surface to volume ratios associated with thin films allow for rapid heat transfer. Switching rates can be in the range of up to about 100 Hz or faster. Motion rates for transducers  4  ideally will be between 1 Hz and 300 Hz and more preferentially between 30 Hz and 200 Hz in order to provide an image with a minimum of flicker. 
     FIG. 4  shows the distal tip  2  of the catheter  12  of  FIG. 3  with the circumferential actuator  42  of the preferred embodiment. The distal tip  2  of the catheter comprises the central lumen  18  with the guidewire  40 , the ultrasound transducer array  4 , the swivel joint  44 , the wire bundle  20  and the nitinol actuator  42 . Optionally, the distal tip  2  also contains the forwardly directed ultrasound transducer array  202 . The nitinol actuator  42  comprises a mount top  52  and a mount bottom  54 , a nitinol ligament/element  56 , a connection or attachment  58 , the positive signal/power lead  60  and the negative signal/power lead  62 . The mount bottom  54  is attached to the catheter shaft  14  while the mount top  52  is attached to the catheter tip  2 . The positive lead  60  and the negative lead  62  are attached to opposite edges of the nitinol ligament/element  56 , respectively. 
   Referring to  FIG. 3  and  FIG. 4 , the positive lead  60  and the negative lead  62  are routed into the wire bundle or transmission line  20 . The positive  60  and negative leads  62  exit the wire bundle  20  at the power/data port  24  where they are connected to the actuator power supply/controller  30 . The actuator power supply/controller  30  transmits over the transmission line  20  an electrical signal through the leads  60 ,  62  to the nitinol ligament/element  56 . This creates either resistive heating when powered or cooling when power is removed through the nitinol ligament/element  56  which causes the nitinol ligament/element  56  to expand or contract its length along the circumference of the distal tip  2 . 
   The nitinol ligament  56  comprises a nitinol film attached to a flexible substrate as described by R. S. Maynard in U.S. Pat. No. 5,405,337. The nitinol film is deposited onto a corrugated silicon surface coated with a thin layer of silicon nitride giving the nitinol ligaments  56  a sinusoidal shape. Polyimide is then spun on and windows are opened to expose the nitinol element. After dissolving the silicon wafer, the flexible polyimide acts as a support structure for the nitinol ligaments  56 . While a shape memory alloy actuator is the preferred embodiment, other actuators  42 , such as those manufactured with electromagnetic or mechanically driven systems, could also be used. The published literature includes other SMA actuators that are also useable with this invention. 
   Referring to  FIG. 3  and  FIG. 4 , the actuator power controller  30  sends a signal through the positive  60  and negative leads  62  to the SMA ligament/element  56  such that the ligament/element  56  becomes heated and contracts which pulls or rotates the distal tip  2  through an angle of 360 degrees or less at the swivel joint  44 . Next, the power supply/controller  30  sends a signal causing the SMA ligament/element  56  to cool and stretch, which pulls back or reverses the rotation of the distal tip  2  through the swivel joint  44 . Typically heating is caused by applying power to the resistive load of the SMA element/ligament and cooling is caused by removing said power. The duty cycle of the signal is set to cause the SMA ligament/element  56  to continuously pull and push the distal tip  2 . The resulting motion is a rotational vibration of the catheter tip  2 . 
   In a more preferred embodiment, a plurality of nitinol actuators  42  are disposed circumferentially around the catheter tip  2 . The phases of the controlling signals are adjusted such that when one nitinol actuator  42  is pulling, the opposing SMA actuator  42  is pushing. That is, when power is applied across the leads  60  and  62  of the first actuator  42 , the electrical power across the electrical leads  60  and  62  of the second SMA actuator  42  is turned off. In this manner, the rotational vibration of the catheter tip  2  can be made steadier and more reliable. 
   In another embodiment, the actuator  42  is electromagnetic, using permanent magnets and electromagnets to oscillate the catheter tip  2 . This system is similar to an electric motor in that the polarities are switched on the electromagnet but continuous rotation is prevented. The electromagnetic system can be installed in the catheter tip  2  or it can transmit the energy through a torque shaft and thus be outside the body. 
   In yet another embodiment, a mechanical rocker linkage can be used to cause the rotational oscillations. 
   In another preferred embodiment the tip  2  rotates independently of the catheter shaft  14 . A longitudinal section of the distal tip  2  is shown in  FIG. 5 . The distal tip  2  comprises the plurality or array of radially directed ultrasound transducers  4  and, optionally forwardly directed ultrasound transducers  202 , the wire bundle  20 , the guidewire  40 , and the swivel connection  44 . Each transducer  4  and  202  comprises leads  48  which are constrained together in the wire bundle  20 . The swivel connection  44  of this embodiment comprises a shaft lip  68 , a tip lip  72 , and a corresponding void  74 . The shaft lip  68 , the tip lip  72 , and the void  74  are annular in configuration. The shaft lip  68  and tip lip  72  mate in a non-binding manner with the void  74  between the shaft lip  68  and tip lip  72 . The shaft lip  68  and tip lip  72  are constructed to retain the distal tip  2  onto the catheter shaft  14 . This results in the catheter shaft  14  retaining the catheter tip  2  but allowing the tip  2  to rotate freely on the shaft  14 . The wire bundle  20  comprising the leads  48 ,  60 ,  62  passes through the above described annular swivel joint  44 . 
   In another embodiment, the leads are connected to a swivel joint electrical rotational connector  44  to allow for the passage of electrical signals and power through the swivel joint. 
   Yet another embodiment of the swivel joint  44  is an elastic segment joining the catheter shaft  14  and the catheter tip  2 . This segment absorbs torque of the oscillating tip  2  and does not transmit the rotational vibration through the catheter shaft  14 . The catheter shaft could optionally also include a high inertia region disposed proximal of the distal tip to stabilize the proximal portion of the catheter. 
   A further embodiment of the swivel joint  44  is a rotational bearing system. Additionally, the catheter  12  could be so flexible as to not require any special swivel connection. Any rotational oscillation would be damped along the length of the catheter shaft  14 . 
   In addition to the guidewire  40  and the balloon  22 , other embodiments of the catheter  12  include a linear reference transducer, and a rotational reference transducer. The balloon  22  is used with the balloon inflation/deflation system  38  to center the catheter  12  in a vessel lumen. The guidewire  40  is used to guide the catheter to the region to be imaged. The linear reference transducer is used when performing a three-dimensional pullback image of the vessel lumen. It allows for accurate determination of location axially along the lumen. 
   Further, the rotational reference transducer is optionally used to measure the rotational displacement between the catheter shaft  14  and the catheter tip  2 . One embodiment comprises a Hall effect switch or other magnetic device where part of the device is attached to the catheter tip  2  and the remaining part of the device is attached to the catheter shaft  14 . Signals are sent, via the wire bundle  20 , containing tip  2  to shaft  14  displacement information. The information is processed and correlated with the ultrasound image. The reference transducers, in another embodiment, are made from strain-gauge type devices that change resistance with strain. Such strain gauge or reference transducers could be mounted across any part of the catheter that moves, including being mounted across the actuators to measure contraction and expansion. 
   Different therapeutic apparatus are optionally incorporated into a catheter that comprises imaging capability. Endovascular treatment of patients is becoming more widely practiced and improved guidance of endovascular therapies would be beneficial to the patient.  FIGS. 3 ,  6 ,  7 ,  8 ,  9 ,  15  and  16  illustrate some of the therapeutic apparatus applicable to this system. 
     FIG. 6  shows an enlarged view of the distal tip  2  of catheter  12  with optional atherectomy or thrombectomy apparatus. Atherectomy and/or thrombectomy may be accomplished using a rotational or vibrating cutter disposed on the catheter to excise plaque or thrombus. The distal tip  2  additionally comprises the distal fluid-tight seal  204 , the fluid suction ports  206  and the plurality of cutting apparatus  208 . The cutting apparatus  208 , such as cutting blades or atherectomy cutters, vibrate rotationally under the motion generated by actuator  42 . Optionally, the cutting apparatus  208  may be driven by a different actuator than that used to drive the motion of the ultrasound arrays  4  and  202 . The distal fluid-tight seal  204  prevents flow around the guidewire  40  exit when vacuum is generated in the central lumen  18 . It allows the vacuum to be directed through vacuum ports  206  to remove tissue that has been excised by the cutting blades  208 . Referring to  FIG. 3 , connector  226  seals the central lumen  18  around the guidewire  40  entrance using the proximal fluid-tight seal  242 , and allows for connection of the vacuum source or suction device  224 . 
     FIG. 7  shows an enlarged view of distal tip  2  incorporating an optional wave source  228 . These wave sources emit potentially therapeutic energy to the body lumen or cavity. The wave source  228  comprises a wave generator  214  and a plurality of electrical leads  216 . Possible wave generators are an X-ray source such as an X-ray tube, a radio frequency antenna or a microwave antenna. Referring to  FIG. 3  and  FIG. 7 , the electrical leads  216  are connected to the wave generator  214  at the distal tip  2 , traverse the catheter  12  through the wire bundle  20  and are connected to the power source  220  at the proximal end  16  of catheter  12 . 
     FIG. 8  shows an enlarged sectional view of the distal tip  2  showing another embodiment of the optional wave source  228 . In this embodiment, the optional wave source  228  comprises a radioactive source  234 , a shutter  240 , a cavity  232 , a linkage  236 , a flexible connector  230  and a lumen  238 . The radioactive source  234  provides therapeutic energy, in the form of ionizing radiation, to the body vessel or lumen. The shutter  240  is opened and closed by linkage  236 . When the shutter  240  is opened, the radioactive source  234  radiates outward into the body vessel or lumen. When the shutter  240  is closed, the radiation is prevented from escaping. The cavity  232  provides space for the shutter  240  to open. The linkage  236  rides within lumen  238  and is connected across the swivel joint  44  by the flexible connector  230 . Referring to  FIG. 3  and  FIG. 8 , the linkage  236  is connected at the proximal end  16  of catheter  12  to the shutter controller  222 . The radioactive source  234  could be positioned proximal to the swivel joint  44  to eliminate the need for the flexible connector  230 . 
     FIG. 9  shows an enlarged view of the distal tip  2  of catheter  12  comprising yet another embodiment of optional wave source  228 . Wave source  228  comprises, in this embodiment, an optional fiber optic bundle  210  and a lens  212 . The fiber optic bundle  210  is used to provide illumination of the body lumen or cavity with visible or near visible light such as infrared or ultraviolet light. The fiber optic bundle  210  is connected to the optional lens  212  to allow for focusing or dispersion of the light as desired. Referring to  FIG. 3  and  FIG. 9 , the fiber optic bundle  210  is disposed along the central lumen  18  of the catheter  12 , so that it is not stressed or flexed by the vibrational rotation of the catheter distal tip  2 . The fiber optic bundle  210  is connected at the proximal end  16  of catheter  12  to the illumination source  218 . 
     FIG. 10  shows an enlarged view of the distal tip  2  of catheter  12  comprising elements that allow for three-dimensional imaging of the body lumen or cavity. The distal tip  2  comprises the catheter shaft  14 , an axial carrier element  302 , the array of radially outwardly directed ultrasound transducers  4 , a circumferential carrier  318 , an acoustic transmission fluid  316 , an axial bearing  300 , the circumferential rotational bearings or swivel joints  44 , a set of at least one axial actuator  304 , a corresponding set of axial connector arms  306 , the circumferential actuators  42 , a corresponding set of circumferential connector arms  312 , a set of strain gauges  308  and the wire bundle  20 . 
   As discussed previously, each array of ultrasound transducers  4  comprise the plurality of transducer leads  48 . The circumferential actuators  42  and the axial actuators  304  comprise the positive signal/power leads  60  and the negative signal/power leads  62 . The strain gauges  308  comprise a plurality of strain gauge electrical leads  310 . The leads  48 ,  60 ,  62  and  310  are bundled together in the wire bundle  20  which travels the length of the catheter shaft  14  and carries power to the circumferential actuators  42  and the axial actuators  304  and power/deflection information to and from the strain-gauges  308  as well as output and reflection electrical signals to and from the ultrasound acoustic transducer array  4 . 
   Referring to  FIG. 10 , the axial carrier element  302  holds the transducer array  4  within the circumferential carrier  318 . The acoustic transmission fluid  316 , such as water, fills the space between axial carrier  302  and circumferential carrier  318  as well as the space between circumferential carrier  318  and catheter shaft  14 . The bearing  300  couples the axial carrier element  302  to the circumferential carrier  318 . Circumferential rotational bearings  44  couple the circumferential carrier  318  to the catheter shaft  14 . Axial actuators  304  connect the circumferential carrier  318  to the rotational carrier  302  through the axial connector arms  306 . Circumferential actuators  42  connect the catheter shaft  14  to the circumferential carrier  318  through circumferential connector arms  312 . Strain gauges  308  are connected across actuators  42  and  304 . 
   Electrical signal leads  48  connect the ultrasound transducers  4  to wire bundle  20  through swivel joint  44 . Positive signal/power leads  60  and negative signal/power leads  62  connect the axial actuators  304  and circumferential actuators  42  to the wire bundle  20  through swivel joint  44 . Strain gauge electrical leads  310  connect the strain gauges  308  to the wire bundle  20  through swivel joint  44 . 
   Referring to  FIG. 3  and  FIG. 10 , axial carrier  302  holds the transducers  4  and is able to move in a rocking fashion around the axis constrained by bearing  300  to motion in the plane parallel to the axis of the catheter shaft  14 . Bearing  300  is also an optional electrical swivel joint. Axial actuators  304  move the axial carrier  302  about bearing  300  to image in the forward (toward the distal tip) and backward (toward the proximal end of the catheter) direction. Sufficient space should be provided inside circumferential carrier  318  to allow for the desired motion of axial carrier  302 . Acoustic transmission fluid  316  is required to fill any air gaps that might exist in the catheter tip so that the acoustic signals are not attenuated after leaving transducers  4  or before being received by transducers  4 . The shapes of the circumferential carrier  318  and axial carrier  302  are designed to minimize drag and cavitation when operating in the liquid  316 . Preferred shapes for the carriers  302  and  318  are cylinders with axes parallel to their respective bearings  300  and  44  or a single sphere. The sphere could be magnetically levitated within a cavity so no bearing would be needed. Optional connector arms  306  increase the freedom of motion for the axial carrier  302 . Sufficiently flexible actuators  304  and  42  would not require connector arms  306  or  312 , respectively. Strain gauges  308  provide positioning information for each of the actuators  304  and  42 . The strain gauge  308  information is fed through the electrical lead  310 , the swivel joint  44  and the wire bundle  20  to the decoder/processor  26  for image analysis. Positioning information is required in order to map the transducer output into a two or three-dimensional coordinate system. Actuators  42  move the circumferential array carrier  318  in the circumferential direction with one rotational bearing  44  shown near the tip of the catheter and another rotational bearing  44  located at the bottom of the circumferential carrier  318 . Positive signal/power leads  60  and negative signal/power leads  62  provide controlled power to each of the actuators  304  and  42  through wire bundle  20  from actuator power supply/controller  30 . Transducer leads  48 , bearing  300  and electrical swivel joint  44  connect the decoder/processor  26  and ultrasound-input signal and power supply/controller  28  through the wire bundle  20  to the transducers  4 . 
   Actuators  42  and  304  are shown for ease of viewing in the plane parallel to the axis of the catheter shaft  14 . One or more actuators  42  and  304  could also be mounted in the plane perpendicular to the axis of the catheter shaft  14 . One or both sets of actuators  304  and  42  could be disposed on a single integrated device to provide motion in both the circumferential and the forward and backward axial rocking directions. Such orthogonal disposition of some or all the actuators could minimize longitudinal stiffness in the catheter and maximize flexibility. In addition, swivel bearings  300  and  44  could be replaced with a single bearing operational in two dimensions, rotation and axial. Such a bearing would be, for example, a ball in a socket or an elastic coupling. The axial transducer carrier  302  and the circumferential transducer carrier  318  would be integrated into a single unit for the single bearing system. In a further evolved embodiment, the transducers  4  could be mounted to actuators  304  and  42  such that no pivot bearing is required, rather, the transducers  4  would be pivoted directly by the actuators. The transducers  4  could also be moved linearly by the actuators but motion is limited by the travel of the actuators so pivoting allows for increasing the three-dimensional imaging volume without a very large amount of actuator travel. The apparatus allows for two-dimensional and three-dimensional imaging of a body lumen or cavity without the need to move the catheter shaft  14  to obtain some of the imaging information. 
   In a preferred embodiment, actuators  304  and  42  comprise nitinol actuators. These actuators  304  and  42  operate independently to move their respective carriers  302  and  318  about their respective pivot points. Each actuator is separately operated or fired. Counter-attached actuators  304  are energized sequentially to create a rocking motion of the axial carrier  318 , around axial bearing  300 , through axial connector arms  306 . This axial rocking motion is independent of the circumferential rocking motion generated by actuators  42 . Counter-attached actuators  42  would be energized sequentially to create a rocking motion of circumferential carrier  318 , around circumferential bearing  44 , through circumferential connector arms  312 . Sequential energizing of counter-attached actuators involves energizing one actuator while power to the other actuator is turned off. Various types of motion could be obtained with this system ranging from random motion to a coordinated scan similar to that used on cathode ray tube screens. Circumferential and axial scan rates of 1 to 400 Hz are appropriate with preferred ranges of 30 to 200 Hz. 
     FIG. 11  illustrates, in cross-section orthogonal to the axis of the catheter, the two-dimensional imaging area of a two-ultrasound transducer array  4 , rotating or oscillating circumferentially through a 90-degree arc. Catheter  12  is inserted into body lumen  100 . The tip  2  of catheter  12  comprises the array  4  of two ultrasound transducers. The image generated by the ultrasound transducer array  4  has a range illustrated by a boundary  332 . Body lumen  100  comprises the body lumen wall  101 , the surface irregularity or atherosclerosis  110 , a surrounding tissue  328  and a volume of blood or fluid  330 . 
   The lumen wall  101  is disposed circumferentially around catheter  12 , which is centered in body lumen  100 . In this embodiment, the array of transducers  4  is rotated or oscillated only in the circumferential direction through a 90-degree angle. A two-dimensional wedge shaped image of the body lumen  100  is obtained. The wedge is bounded by the range of the transducers  4  and the angle through which the transducers  4  are rotated. In this embodiment, the image area comprises two 90-degree wedges. Additionally, there is an area where no information is acquired comprising a blind area  320  of two 90-degree wedges. The body lumen wall  101 , surface irregularity  110 , surrounding tissue  328  and fluid  330  are not visible in the blind areas  320 . 
   The maximum range of the transducers is described by the boundary  332 . The distance from the transducer  4  to the boundary  332  and the resolution of the image are affected by the modulation frequency of the transducer array  4 . In general, when the modulation frequency is increased, the range is decreased and the resolution of the image is increased. The modulation frequency of the ultrasound system is from 1 to 100 MHz, with a preferred range from 5 to 50 MHz and a more preferred range of 10 to 30 MHz. The practical circumferential angular limit is determined by the mechanics and dynamics of the actuators  42  and circumferential connector arms  312 , number of transducers  4 , mechanics of bearings  44  and  300  and the space available within the catheter  12 . 
     FIG. 12  illustrates, in cross-section parallel to the axis of the catheter, the two-dimensional imaging area of a two-ultrasound transducer array  4  rocking or pivoting longitudinally parallel to the axis of the catheter through a 60-degree arc. Catheter  12  is inserted into body lumen  100 . The tip  2  of catheter  12  comprises the array  4  of two ultrasound transducers in axial carrier  302  being rocked around axial bearing  300 . Body lumen  100  comprises the surface irregularity or atherosclerosis  110 , the surrounding tissue  328  and blood or fluid  330 . Fluid  330  fills the image between the body lumen wall  101  and the catheter  12 . The body lumen wall  101  is disposed around catheter  12 , which is centered in the body lumen  100 . In this embodiment, the array of transducers  4  is rocked 30 degrees forward and 30 degrees backward (60 degrees total) in the plane parallel to the axis of the catheter  12 . A two-dimensional wedge-shaped image of the body lumen wall  101  is obtained. The wedge is bounded by the range  332  of the transducers  4  and the angle through which the transducers  4  are rocked. In this embodiment, the field of view or imaging area comprises two 60-degree wedges. Additionally there is an area where no information is acquired comprising the dead or blind area  320  of two 120-degree wedges. The body lumen wall  101 , blood  330  and atherosclerosis  110  are not visible in the blind areas  320 . 
   Referring to  FIG. 3  and  FIG. 10 , the practical limit of the angular tilt of the array of transducers  4  is governed by the mechanics and dynamics of the bearing  300 , the axial carrier  302 , the space provided for the carrier  302  to move, the mechanics of the linkages  306  and the performance of the actuators  304 . The practical angular limit in the plane parallel to the catheter  12  is 180 degrees or less. The practical range  332  of the system is governed by the frequency of the ultrasound signal and other characteristics of the transducers  4  and their controller  28  but is sufficient to visualize the body lumen  100  and immediate surroundings. These factors also have an effect on the resolution of the system. 
     FIG. 13  illustrates the three-dimensional imaging volume of the single ultrasound transducer array  4 , oscillating circumferentially through a 90-degree angle (45 degrees clockwise and 45 degrees counterclockwise) and simultaneously rocking through a 60-degree angle (30 degrees forward and 30 degrees backward). In this embodiment, the catheter  12  comprises the single transducer ultrasound array  4  and the central lumen  18 . As the array  4  is rotated and rocked, a three-dimensional field of view or imaging volume  340  is obtained. The imaging volume  340  is bounded by the range  332  of the transducer array  4 , two 90-degree wedges and two 60-degree wedges. Additionally, there is an area where no information is acquired comprising a dead or blind volume  342 . The blind volume  342  is the sphere enclosing the array  4  with the range  332  minus the imaging volume  340 . These representative specifications are appropriate to allow for monitoring of endovascular therapies. However, the angular specifications may significantly differ from those shown and still be useful and appropriate. 
     FIG. 14A  illustrates the three-dimensional imaging volume  340  of catheter  12 . In this embodiment, sufficient transducers  4  are rotated through a circumferential angle sufficient to fill in the gaps or blind zones between the transducers  4 . For example, if four transducers  4  are used, a circumferential rotation angle of 90-degrees or greater would suffice to render a complete 360-degree image. Six transducers  4  would require a 60-degree or greater circumferential rotation angle. The array of ultrasound transducers  4  are also rocked or pivoted axially through a 60-degree angle. The resulting three-dimensional imaging volume  340  is a toroid bounded by the range  332  of the transducers  4  and constrained within a 60-degree wedge shaped longitudinal section. 
     FIG. 14B  shows the three-dimensional imaging volume  340  of catheter  12  where axial rocking occurs through a greater angle than in  FIG. 14A . In this embodiment, sufficient transducers  4  are rotated through a circumferential angle sufficient to fill in the gaps or blind zones between the transducers  4 . Additionally, the transducer array  4  is rocked axially through a 180-degree angle. The resulting three-dimensional imaging volume  340  is a sphere centered about the ultrasound array  4  and bounded by the range  332  of the ultrasound transducers  4 . In this embodiment, there are no blind zones within the range  332  of the transducers  4 . 
     FIG. 15  and  FIG. 16  show the tip  2  of the catheter  12  with the added features of the inflation lumen  350 , the non-distensible dilatation balloon  22 , a stent  354  and a radiopaque marker  356 . Referring to  FIG. 15 , the balloon  22  and the stent  354  are collapsed to be able to pass through the body lumen  100  to the target site. In this embodiment, the balloon  22  is positioned on the catheter tip  2 , over the transducer array  4 , to be able to image the balloon  22  and stent  354  during inflation and deployment or retrieval. Deployment or retrieval of resiliently expandable stents  354  or devices would be similarly monitored with this system. The radiopaque marker  356  allows for visualization of the catheter under fluoroscopy and X-ray. The radiopaque marker  356  in one embodiment is designed to provide orientation information for the catheter in the circumferential direction. Typically, the radiopaque marker  356  is fabricated from tantalum, platinum or the like. 
     FIG. 16  shows the tip  2  of the catheter  12  with the balloon  22  and the stent  354  expanded. Expansion occurs through the application of high-pressure fluid, preferably water, saline, or radiopaque contrast material to the interior of the balloon  22 , which is accessed by the inflation lumen  350 . Referring to  FIG. 3  and  FIG. 16 , the high pressure is generated by the inflation system  38 , such as a syringe, connected at the proximal end  16  of the catheter  12  to the inflation port  36 , which connects to the balloon  22  through the inflation lumen  350 . 
     FIG. 17  illustrates the distal end of an imaging catheter  400  comprising a catheter shaft  402  with a proximal and a distal end, a plurality of imaging transducers  414  and  416  that are vibrated rotationally and, optionally, rocked in a plane parallel to the long axis of the catheter shaft  402 . The imaging catheter  400  further comprises a delivery lumen  406 , an embolic coil  408 , a pusher  412 , a releasable link  410 , and a radiopaque marker  404 . The anatomy into which the embolic coil  408  is being deployed comprises the parent vessel  420 , the aneurysm sac  422 , and blood  424 . An exemplary field of view  418  of transducer  414  is also illustrated. 
   The pusher  412  extends from the distal end of the catheter  400  to the proximal end and the operator pushes on the pusher  412  to move the embolic coil  408  along the delivery lumen  406  and out near the distal end of the catheter  400 . The releasable link  410  is activated to unhook the embolic coil  408 . The pusher  412  is then withdrawn out of the proximal end of the catheter  400  and a new coil  408 , attached to a pusher  412  by a releasable link  410 , is now advanced into the proximal end of the delivery lumen  406 . 
   Referring to  FIG. 17 , the method of aneurysm or arteriovenous malformation embolization comprises the steps of first placing a guidewire or guide catheter endovascularly into the cerebrovasculature. The real time 2-D or 3-D ultrasound imaging array is advanced either over the guidewire or through one or more guiding catheters to the location of the aneurysm under fluoroscopic guidance. The ultrasound imaging array catheter  400  comprises a lumen for delivery of embolic material such as hardenable polymers, platinum coils, gels or the like. In another embodiment, a catheter separate from the imaging catheter  400  is used to treat the aneurysm or arteriovenous malformation by deploying the embolic material. With two separate catheters, close proximity between the imaging region of the imaging catheter and the distal end of the treatment catheter are beneficial. Under direct visualization of the aneurysm  422 , as imaged by the catheter  400 , the embolic material  408  is deployed through the delivery lumen  406  into the aneurysm  422 . Complete treatment and interrogation of the result is completed using the imaging array  414  and  416 . Additional embolic material is deployed as required. The imaging and treatment catheters are removed. 
   The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is therefore indicated by the appended claims rather than the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.