Patent Publication Number: US-2019175148-A1

Title: Distance, diameter and area determining device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/214,297 (Attorney Docket No. 52859-703.201), filed Mar. 14, 2014, which claims the benefit of U.S. Provisional No. 61/801,438 (Attorney Docket No. 529859-703.101), filed Mar. 15, 2013, the entire content of which are incorporated herein by reference 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to methods and medical devices that gather information about vessels, structures or devices in a body and more particularly to methods and medical devices for measuring dimensions of such vessels, structures or devices and calculate cross-sectional areas of such vessels, structures or devices. 
     2. Description of Related Art 
     Within the field of interventional cardiology, the utilization of coronary drug-eluting stents has significantly reduced stent failure and the need for revascularization. Recent imaging studies have illustrated that the predominate cause of residual stent failure is stent underexpansion and lesion edge problems such as undersizing the length of the stent needed to appropriately cover the lesion. The limitations of today&#39;s angiogram often do not allow the physician to adequately assess the lesion prior to stent placement or determine the degree of expansion of the deployed stent. This is a problem in need of a solution. 
     Current imaging catheters utilize ultrasound or optical technologies to provide a cross-section image that is then interpreted by the physician to determine, among other characteristics, the dimensions of the lumen surrounding the catheter. For example, Intravascular Ultrasound (IVUS) is commonly used in interventional diagnostic procedures to image blood vessels to locate and characterize atherosclerosis and other vessel diseases and defects. In use, a guidewire is placed in a vessel of interest. Then, an IVUS catheter is threaded over the guidewire and ultrasonic signals are sent from the catheter, bounced off the tissue, received by the catheter and passed from the catheter to a system. These ultrasound echoes are processed by the system to produce images of the vessel and its physiology. 
     Optical Coherence Tomography (OCT) systems are also used in interventional diagnostic procedures to image blood vessels to locate and characterize atherosclerosis and other vessel diseases and defects. In use, again a guidewire is placed in a vessel of interest. Then, an OCT catheter is threaded over the guidewire and light signals are sent from the catheter, bounced off the tissue, received by the catheter and passed from the catheter to a system. These light echoes are processed by the system to produce images of the vessel and its physiology. 
     These IVUS and OCT images and the information about the vessel, including vessel dimensions, is considerably more detailed than the information that is obtainable from traditional angiography images that which shows only a two-dimensional shadow of the vessel lumen. Examples of some of the information provided by IVUS or OCT systems include: determining a diameter of a vessel to be used in determining the correct diameter or a stent to be placed; determining the length of a physiological problem such as the presence of atherosclerotic material so that the correct length of a stent to be placed can be determined to dilate the stenosis; verifying that a stent, once placed, is well apposed against a vessel wall to minimize thrombosis and optimize drug delivery (in the case of a drug eluting stent); verifying that after a stent has been place, the diameter and luminal cross-section area of the stented vessel are adequate; and identifying an exact location of side-branch vessels to aid in stent placement or therapy delivery. 
     But, although current IVUS and OCT systems provide additional and more detailed information compared to angiograms, these IVUS and OCT systems introduce significant additional time, cost and complexity into minimally-invasive procedures. Further, the images produces by IVUS and OCT systems often are subject to interpretation of the physician. Thus, there is a need for an improved way to get information about a vessel or structure, particularly information about the diameter of a vessel or structure. 
     SUMMARY OF THE INVENTION 
     The invention describes a novel implementation of ultrasound or OCT technology to approximate the dimensions of fluid-filled structures (when using ultrasound technology) or other structures (when using OCT technology). The invention in a preferred embodiment is an elongated member such as a catheter that uses ultrasound or OCT technology to approximate the dimensions of a structure into which the catheter has been placed. In a preferred embodiment, the catheter includes multiple ultrasound transducers arranged in an annular or circumferential configuration on, embedded into or within the body of the elongated member so that distance measurements can be obtained between the elongated member and the wall of the immediately facing structure (e.g., a fluid-filled lumen). Utilizing these measurements, the present invention approximates for the physician the shape and size of the structure into which the elongated member is placed. The invention also includes a method for producing three-dimensional images from two-dimensional images. 
     The disclosed device, as used in accordance with the methods of the invention, ensures a simpler way of calculating cross-sectional dimensions and creating three-dimensional maps than prior art devices and techniques. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described hereafter in detail with particular reference to the drawings. Throughout this description, like elements, in whatever embodiment described, refer to common elements wherever referred to and reference by the same reference number. The characteristics, attributes, functions, interrelations ascribed to a particular element in one location apply to that element when referred to by the same reference number in another location unless specifically stated otherwise. In addition, the exact dimensions and dimensional proportions to conform to specific force, weight, strength and similar requirements will be within the skill of the art after the following description has been read and understood. 
       All figures and drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship and dimensions of the parts to form examples of the various embodiments will be explained or will be within the skill of the art after the following description has been read and understood. 
         FIG. 1  is a side schematic view of a preferred embodiment of the catheter of the present invention. 
         FIG. 2  is an end view of an alternate embodiment of the catheter of the present invention. 
         FIG. 3A ,  FIG. 3B  and  FIG. 3C  are end views of the transducer arrays of alternate embodiments of the catheter of the present invention. 
         FIG. 4A  and  FIG. 4B  are perspective views of a switch and a single array of transducers of an alternate embodiment of the catheter of the present invention. 
         FIG. 5  is a perspective view of the catheter of the present invention in use in a vessel. 
         FIG. 6  is an end schematic view of the catheter of an embodiment of the present invention used to determine the cross-sectional area of a structure. 
         FIG. 7  is a side schematic view of an embodiment of the catheter of the present invention having an angioplasty balloon. 
         FIG. 8  is a side schematic view of an embodiment of the catheter of the present invention having a stent deployment balloon and a stent. 
         FIG. 9  is a side schematic view of a rapid exchange embodiment of the catheter of the present invention. 
         FIG. 10  is a perspective phantom view of three-dimensional map made according to the present invention. 
         FIG. 11  is a perspective phantom view of another three-dimensional map made according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In order that the invention may be clearly understood and readily carried into effect, preferred embodiments of the invention will now be described with reference to the accompanying drawings. The description of these embodiments is given by way of example only and not to limit the invention. The medical device of the present invention, in all of its embodiments, is shown in the drawings generally labeled  10 . A preferred embodiment of the present invention being described herein is a catheter. But, the invention applies to many other devices where knowing the dimensions around the medical device  10  is desirable. 
     As mentioned above, although a preferred embodiment of the present invention is a catheter, the invention applies to many other devices where it is desirable to know the cross-sectional dimensions the space surrounding the medical device  10 . Examples of such medical devices  10  include, but are not limited to, conventional intravascular ultrasound (IVUS), optical coherence tomography (OCT) and photoacoustic imaging systems, image guided therapeutic devices or therapeutic delivery devices, diagnostic delivery devices, Forward-Looking IVUS (FLIVUS), intracardiac echocardiography (ICE), forward looking ICE, optical light-based imaging (e.g., endoscopes), pressure sensing wires, high intensity focused ultrasound (HIFU), radiofrequency, thermal imaging or thermography, electrical impedance tomography, elastography, orthopedic and spinal imaging and neurological imaging. 
     As shown in  FIG. 1 , the medical device  10  of the present invention includes a body member  12  having a proximal end  14  and a distal end  16 . The medical device  10  includes a plurality of transducers  18 . In a preferred embodiment, the medical device  10  also includes an elongated tip  20  having a proximal end  22  and a distal end  24 . The medical device  10  includes a proximal connector  26 . In an embodiment of the invention, the medical device  10  is part of a system  28  that includes a distal connector  30 , electrical conductors  32 , a data acquisition unit  34  and a computer  36 . 
     In a preferred embodiment of the medical device  10  shown in  FIGS. 1-5 , the body member  12  is tubular and has a central lumen  38 . In a preferred embodiment of the medical device  10 , the body member  12  has a diameter of about 650 .mu.m. This dimension is illustrative and not intended to be limiting. In embodiments of the medical device  10 , the diameter of the medical device  10  will depend on the type of device that medical device  10  is and where the medical device  10  will be used, as is well understood in the art. 
     The proximal end  14  of the body member  12  is attached to the proximal connector  26 . In the embodiment of medical device  10  that includes an elongated tip  20 , proximal end  22  of the elongated tip  20  is attached to the distal end  16  of the body member  12 . The elongated tip  20 , where employed, allows the catheter  20  to be moved along a rapid exchange device, were employed as described below, adds flexibility to the distal end of the medical device  10  to allow easier maneuvering of the medical device  10 , particularly in vessels, and allows the transducers  18 , in certain embodiments, to be more precisely located in the vessel or other structure where the medical device  10  is placed. 
     The body member  12  and elongated tip  20  are made of resilient flexible biocompatible material such as is common for IVUS catheters as is well understood by those skilled in the art. Medical device  10  is preferably tubular with a central lumen  38  but may also not have a central lumen  38 . Further, medical device  10  may have one or more lumens in addition to central lumen  38 . Preferably, the outer diameter of the body member  12  and elongated tip  20 , if present, is substantially constant along its length. But, neither the body member  12  nor elongated tip  20  is required to have a substantially constant diameter. 
     The transducers  18  in embodiments of the medical device  10  using ultrasound are preferably conventional piezoelectric transducers such as are typically used on IVUS catheters. These piezoelectric transducers are built from piezoelectric ceramic material and covered by one or more matching layers that are typically thin layers of epoxy composites or polymers. In addition, other transducer technologies may be used to create transducers  18  including, but not limited to, PMUT (Piezoelectric Micromachined Ultrasonic Transducer), CMUT (Capacitive Micromachined Ultrasonic Transducer) and photoacoustic technologies. The medical device  10  of the present invention may be of the rotational type or solid state (non-rotational type) such as are commonly in use in connection with IVUS imaging systems. 
     Further, the operating frequency for the ultrasound transducers  18  is typically in the range of from about 8 to about 50 MHz, depending on the dimensions and characteristics of the transducer. Generally, higher frequency of operation provides better resolution and a smaller medical device  10 . But, the price for this higher resolution and smaller catheter size is a reduced depth of penetration into the tissue of interest and increased echoes from the blood itself (making the image more difficult to interpret). Lower frequency of operation is more suitable for imaging in larger vessels or within structures such as the chambers of the heart. Although specific frequency ranges have been given, this range is illustrative and not limiting. The ultrasonic transducers  18  may produce and receive any frequency that leaves the transducer  18 , impinges on some structure or material of interest and is reflected back to and picked up by the transducer  18 . 
     The medical device  10  may, in some embodiments, use optical coherence tomography (OCT) transducers  18 . These OCT transducers produce light in the near infrared range that leaves the transducer  18 , impinges on some structure or material of interest and is reflected back to and picked up by the transducer  18 . In some embodiments of these OCT transducers  18 , the light is produced by a laser or other coherent light source outside of the medical device  10  and passed to the medical device  10  via fiber optic strands through the proximal connector  26  and ultimately to the location of the transducers  18  near the distal end  16  of the body member  12 . In other embodiments of the medical device  10  that uses OCT transducers  18 , the light needed for the transducers  18  is produced on the medical device  10  itself (e.g., at or near the proximal end  14  of the body member  12  by, for example, laser diodes) or at the site of the transducers  18  themselves as, for example, by laser diodes. Also, these transducers  18  have been described as having been of the OCT type. But, any transducers  18  that use coherent light or electromagnetic radiation may be used. 
     Regardless of whether the transducers are of the ultrasound or OCT type, the transducers  18  may be located on the outer surface  40  of the body member  12 , within the material of the body member  12 , on the surface of the central lumen  38  or within the central lumen  38 . In those embodiments where the transducers  18  are not located on the outer surface  40  of the body member  12 , the material of the body member  12  must be transparent to the ultrasonic waves or light emitted from or returning to the transducers  18  or the ultrasonic waves or light emitted from or returning to the transducers  18  may pass through windows in the material of the body member  12 . 
     In the medical device  10  of the invention, two or more transducers  18  are arranged in a single annular or circumferential ring around or within the body member  12  ( FIG. 4A ) or can be an array of multiple annular or circumferential rings located one behind the other ( FIG. 4B ). Where the medical device  10  includes an array of transducers  18  such as is shown in  FIG. 4B , the transducers  18  in one annular or circumferential group are preferably, although not required to be, staggered with respect to the transducers  18  in the annular or circumferential group located either more proximal or distal to it. Further, although arrays of two annular or circumferential groups of transducers  18  are shown, any number of annular or circumferential groups of transducers  18  may be used. 
     As stated, the circumferential arrays of transducers  18  are axially separated along the body member  12 . In one configuration of the circumferential arrays of transducers  18 , the transducers  18  in one array are aligned with the transducers  18  in the adjacent array along the elongated axis of the body member  12 . In another, preferred embodiment of the medical device  10  shown in  FIG. 4B , the transducers  18  in one array are staggered with respect to the transducers  18  in the adjacent array. “Staggered” means that the transducers  18  in one array are not aligned with the transducers  18  in the adjacent array along the axis of the body member  12 . 
     In the preferred embodiment of the medical device  10  of  FIG. 4B , the transducers  18  in one array overlap with the transducers  18  in the adjacent array so that a very compact configuration of transducers  18  is produced. For example, by way of illustration, the medical device  10  could have two arrays of transducers  18  where the transducers  18  are staggered with respect to the transducers  18  of the adjacent array ( FIG. 4B ) and the centers of the transducers  18  of one array are spaced from the centers of the transducers  18  of the other array by a distance, for example, of about 250 .mu.m. This dimension is illustrative and not intended to be limiting. Further, although the preferred embodiment of the medical device  10  has the transducers  18  of one array overlapping with the transducers  18  of the adjacent array, these transducers  18  are not required to be overlapping. 
     This embodiment of the medical device  10  where one circumferential array of transducers  18  is off-set from and overlapping or interlaced with the adjacent array of transducers  18  allows each transducer  18  to have sufficient surface area to be effective because the distance between the centers of each transducer  18  is minimized. As a result, the staggering and in some cases the interlacing of the transducers  18  allows all the transducers  18  to fit within a small circumference as required when the transducers  18  are utilized on small medical devices  10  such as a 0.035″ or 0.018″ wire or even a 0.014″ wire such as would be used in coronary guidewire such as much pass through the lumen tube of an angioplasty catheter which is approximately 650 um in size. 
     The surface shape of the transducers  18  can be circles, ovals, squares, rectangles, triangles, wedges, or similar shapes. The distance between centers of each ultrasound transducer  18  can be as large as 1-2 mm without being significant to vascular measurements although distances less than 1 mm are preferable and even more preferable is less than 500 um. At center-spacing distances of 500 um or less, the distance measurements produced by the transducers  18  will not be meaningfully altered by the fact that the transducers  18  in adjacent arrays of transducers  18  are not circumferentially aligned. 
     As shown in  FIG. 6 , each of the transducers  18 , when energized, emits an ultrasonic wave or light that is directed away from the transducer  18  and thus from the body member  12 . As shown in  FIG. 2 , because the transducers  18  are located in an annular or circumferential fashion around the body member  12 , the ultrasonic waves or light they emit are directed away from the body member  12  in non-parallel paths. The transducers  18  may be energized to emit ultrasonic waves or light simultaneously or may be energized selectively (e.g., sequentially around the circumference of the body member  12  or in any other selective fashion). 
     The transducers  18  can be individually connected to electrical conductors  32  to connect the transducers  18  to the proximal connector  26 . In certain embodiments, each transducer  18  needs an electrical pulses to energize the transducer  18  and the ability to deliver received echo signals from the transducer  18  electrically to a computer  36  or Patient Interface Module (PIM)  44  to be analyzed (during the intervals between transmit pulses). Where a PIM  44  is used, the PIM is located along the path between the medical device  10  and computer  36  and may include the distal connector  30 . The computer  36  or PIM  44  controls the electrical or optical pulses sent to the transducer  18 , processes, amplifies, filters or aggregates the data, interprets the signal coming back from the transducer  18  after the transducer  18  picks up the received echoes from the emitted pulses, produces images, makes calculations including calculations of dimensions and performs co-registration of images, data and calculations produced by the computer  36  with other images, data and calculations. 
     The electrical conductors  32  in certain embodiments run from the transducers  18  to the proximal connector  26  and may run within the material of the body member  12  or along its outer surface  40  or along or within the central lumen  38  to conduct the electrical excitation provided to the proximal connector  26  to the transducer  18  and return the signal from the transducer  18  thereafter to the proximal connector  26 . Electrical conductors  32  also carry signals from the transducers  18  to the computer  36  or PIM  44 . The electrical conductors  32  may be wires including twisted pair wire, coaxial cable, fiber optics, wave guides and other wire media as is well understood in the art. 
     In other embodiments of the medical device  10 , particularly those embodiments using OCT technology, optical fibers carry energy to the transducers  18  and signals from the transducers  18  to the computer  36  or PIM  44  or both. In a variant embodiment applicable to both ultrasound and OCT systems, electrical energy may be carried to the transducers  18  via electrical conductors  32  and the signal of the received echoes sent back from the transducers  18  to the computer  36  or PIM  44  via optical fibers. 
     Further, although in some embodiments of the medical device  10 , the transducers  18  send their signals to the computer  36  or PIM  44  through electrical conductors  32  or optical fibers, in other embodiments, the transducers  18  communicate their signals to the computer  36  or PIM  44  through wireless communication means well known to those skilled in the art including but not limited to acoustic, RF and infrared technology. 
     Alternately, as shown in  FIG. 5 , the transducers  18  can be connected to an electrical switch  46  located between the electrical conductors  32  and the transducers  18 . The electrical switch  46  reduces the number of necessary electrical conductors  32  by having fewer lines travel from the proximal connector  26  to the switch  46  and then having the electrical energy carrying ability of the few line expanded through the switch to reach the multitude of transducers  18 . Further, additional electrical conductors  32  or optical fibers can be added to control the electrical switch  46 . In a preferred embodiment of switch  46 , switch  46  is a multiplexer such as is well understood in the art. The use of a multiplexer reduces the number of electrical conductors  32  or optical fibers passing from the proximal connector  26  through the body member  12  to the transducers  18  and in some cases, provides additional control functions. 
     Preferably, four ( FIG. 3A ) to  12  transducers  18  are used for measurements in a medical device  10 . More preferably, six ( FIG. 3C ) to ten transducers  18  will be utilized ( FIG. 3B  showing eight transducers  18 ). Where the medical device  10  is a coronary catheter, because of the need to keep the medical device  10  small in order to fit into the small coronary arteries, each transducer  18  will preferably have an area of less than about 1 mm 2 . The number of transducers  18 , as well as the dimensions given, are for illustration purposes only and not intended to be limiting. Any number of two or more transducers  18  as well as any practical dimensions for the transducers  18  may be used as technology allows and as desired by those skilled in the art. 
     Where the medical device  10  is part of a system  28 , in addition to the medical device  10  described above, the system  28  will further include the computer  36  or PIM  44  or both (instead of just having the medical device  10  connected to the computer  36  or PIM  44 ). Where the medical device  10  is part of a system  28 , a distal connector  30  mates with the proximal connector  26 , as is well understood in the art, to connect the medical device  10  to the rest of the system  28 . Electrical conductors  32  carry the control signals or energy or both to the distal connector  30  where the control signals, energy or both are passed to the proximal connector  26  to be used by the medical device  10 . 
     The system  28  also preferably includes a data acquisition unit  34  that may be part of or separate from the computer  36  or PIM  44 . The data acquisition unit  34  converts the analog data produced by the transducers  18  into digital data that can be processed by the computer  36  or PIM  44 . As mentioned, the data acquisition unit  34  may be part of or separate from either the computer  36  of PIM  44 . In addition, the data acquisition unit  34  may be part of the medical device  10  itself or may be located in the distal connector  30  or elsewhere along the path from the distal connector  30  to the computer  34  or PIM  44 . 
     In an embodiment of the medical device  10  shown in  FIG. 7 , an angioplasty balloon  48  is placed on or around the body member  12  as is well understood in the art. In this embodiment, the transducers  18  are preferably placed distal to the angioplasty balloon  48 . In another embodiment of the medical device  10  shown in  FIG. 8 , a stent delivery balloon and stent assembly  50  is placed on or around the body member  12  as is well understood in the art. In this embodiment, the stent delivery balloon and stent assembly  50  includes a stent delivery balloon  52  and a stent  54 . The transducers  18  are also preferably placed distal to the stent delivery balloon and stent assembly  50 . In either of these embodiments, the medical device  10  includes a duct  56  that travels along the length of the body member  12  from the respective balloons and ends in an inflation port  58 . Balloon  48  or the balloon of the stent delivery balloon and stent assembly  50  may be selectively inflated and deflated via the inflation port  58 . 
     In an embodiment of the medical device  10  shown in  FIG. 9 , the medical device  10  is a rapid-exchange catheter. Accordingly, the medical device  10  further includes a guide wire exit port  60  located on or near the distal end  24  of the elongated tip  20  in order to aid in directing the medical device  10  through a vessel. Of course, the medical device  10  may be an “over-the-wire” device. In this embodiment of the medical device  10 , a guidewire passes through the medical device  10  through the central lumen  38  from the proximal connector  30  to the distal end  16  of the body member  12  or distal end  24  of the elongated tip  20  if an elongated tip is used. In order for the guidewire to pass entirely through the medical device  10 , the central lumen  38  must also pass through the array or arrays of transducers  18  as well as the switch  46  and elongated tip  20 , if either is present. 
     In embodiments of the present invention involving the system  28 , the system  28  may also include a patient interface module PIM  44  that facilitates communications between the medical device  10  and the remaining aspects of the system  28 . In some embodiments of the system  28 , the PIM  44  performs some of the functions of the computer  36  including, but not limited to, amplification, filtering, or aggregating of the data or any combination of these. Further, the PIM  44  may also supply high and low voltage AC or DC power or light to the body member  12  including for powering the transducers  18 . 
     In use, the medical device  10  described above, is placed in a desired location, for example, by advancing the medical device  10  up the femoral artery to a desired location in the aorta. Because of the unique location of each of the transducers  18  on the outer surface  40  of the body member  12 , one the medical device  10  is in a desired location, each transducer  18  is “aimed” at a different location and thus will “see” different structure ( FIG. 2 ). With the medical device  10  in the desired location, the transducers  18  are energized so that either an ultrasonic or light wave produced by the transducers  18  leave the transducers  18  to impinge on the surrounding structure ( FIG. 6 ). The ultrasound or light waves reflect off the surrounding structure (which could be tissue, blood or other fluid, devices, bone, etc.) at different depths and return to the transducers  18  where they are picked up by one or more transducer  18  ( FIG. 6 ). The signal detected by each transducer  18  is sent to the computer  36  or PIM  44  to be processed. 
     In particular, the signal is processed to calculate the distance from each transducer to the nearest structure (e.g., the wall of the vessel in which the medical device  10  is placed). The distance is calculated using time-of-flight techniques associated with IVUS and OCT systems such as is well understood in the art. 
     Because each transducer  18  is uniquely aimed circumferentially around the medical device  10  ( FIGS. 2 and 3A-3C ), each transducer  18  will produce a signal representative of the distance from that transducer  18  to the structure nearest that transducer  18 . For example as shown in  FIG. 10 , the medical device  10  has six transducers in each array of transducers  18 . Each transducer  18  sends and receives a signal to produce respective distances D 1 -D 6  in one array and distances D 7 -D 12  in an adjacent array. When all the distances from each of the transducers  18  to their respective nearest structures are received, and because the diameter of the body member  12  where the transducers  18  are located is known, the computer  36  or PIM  44  can calculate the diameter of the cavity around the transducers  18  at any location radially from the transducers  18 . This is done by taking the calculated distance from transducers  18  arranged on opposite sides of the body member  12  to their respective nearest structure (e.g., D 1  and D 4 , D 2  and D 5 , D 3  and D 6 ) and adding the diameter of the medical device  10  at the transducers  18  to determine the axial distance from one “wall” of the structure facing one transducer  18  to the “wall” of the structure facing the transducer  18  directly opposite the first transducer  18 . By calculating such distances of respective pairs of transducers  18  (e.g., D 1  and D 4 , D 2  and D 5 , D 3  and D 6 ), the radial distance or diameter from one “wall” to the opposite “wall” along an axis passing through the paired transducers  18  can be determined. When several such distances are calculated and plotted radially around the medical device  10 , a map of the cross-section of the structure (e.g., blood vessel, heart chamber, bladder) can be determined. 
     Note that this map is a two-dimensional map. But, a three-dimensional map may also be produced by the medical device  10 . This may be accomplished two ways. First, in embodiments of the medical device  10  where there is more than one array of transducers ( FIG. 4B ), each array will produce its own two-dimensional cross-sectional map. For example, in  FIG. 10  two maps are made, the first map made up of distances D 1 -D 6  and connecting segments M 1 -M 6  corresponding to a first array of transducers  18  and a second map made up of distances D 7 -D 12  and connecting segments M 7 -M 12 , respectively. Because each array of transducers  18  is spaced from its neighbor array of transducers  18 , the resulting two-dimensional cross-sectional maps will represent different cross-sections of the underlying structure (e.g., cross-sections separated by the spacing between each of the circumferential arrays). Combining these multiple two-dimensional maps produces a three-dimensional structure ( FIG. 10 ). 
     Another way of producing a three-dimensional map is to move the medical device  10  axially forward or backwards while taking measurements. Preferably, such forward or backward axial movement is done in a controlled and measured way. By knowing the speed and direction of the pullback, the location of the respective distance measurements can be plotted to define a three-dimensional structure. For example, if a medical device  10  is in a blood vessel, for example during a veinogram, and is pulled back at a controlled rate while taking measurements of the distance from each of the transducers  18  to the wall of the blood vessel directly facing the transducer  18 , a three-dimensional map of the blood vessel is produced ( FIG. 11 ). 
     In the example of  FIG. 11 , each array of transducers  18  will produce its own two-dimensional cross-sectional map. In the example of  FIG. 11  three maps are made. The first map is made up of distances D 13 -D 18  and connecting segments M 13 -M 18  corresponding to a first array of transducers  18 . A second map is also made up of distances D 19 -D 24  and connecting segments M 19 -M 24 , respectively. This second map can be made by either a second array of transducers  18  as described above in connection with the maps of  FIG. 10  or may be made by making a first map by an array of transducers  18  and then moving that same array of transducers axially to produce the second map. In addition, a combination of both approaches to creating maps can be done so that each array of transducers  18  produces a map at a particular axial location of the medical device  10  and each array produces additional maps as the medical device  10  is being moved axially. Because each array of transducers  18  is spaced from its neighbor array of transducers  18 , the resulting two-dimensional cross-sectional maps will represent different cross-sections of the underlying structure (e.g., cross-sections separated by the spacing between each of the circumferential arrays). Combining these multiple two-dimensional maps, however produced, produces a three-dimensional structure ( FIG. 11 ). 
     The two or three-dimensional maps described above may be co-registered to data, figures, physiological measurements, images such as x-ray, fluoroscopy, IVUS, OCT, CT, MRI and other previous or currently acquired images or information according to known co-registration techniques. 
     Further, with the cross-sectional maps formed as described above, the cross-sectional area can be determined. This cross-sectional area is determined by taking the distance lines produced by the transducers  18  to calculated diameters, which distance lines are adjacent to each other circumferentially around the medical device  10 , generating a line connecting the adjacent distance lines to create a two-dimensional closed substantially “pie piece” shape, calculating the area of that shape and then adding together the areas of all the shapes to get the total area of the structure around the medical device  10 . Techniques for generating the lines connecting adjacent diameters to create two-dimensional closed shapes include, but are not limited to, forming straight lines, arcs of a circle, curves and splines, such as Basis splines or B-splines, and may take into consideration information from other two-dimensional cross-sectional diameters or distances from the transducers  18  to the closest tissue or structure of interest determined from other arrays of transducers  18  on the medical device  10  or from two-dimensional diameters determined from moving the medical device  10  axially as described above. 
     The transducers  18  of one or more arrays may be energized simultaneously so that a “snap shot” image is produced. Where the transducers  18  are energized simultaneously, the medical device  10  must be configured to be able to pass the signals produced by the various transducers  18  by receiving their respective echoes back to the computer  36  or PIM  44  to be processed. The transducers  18  of one or more arrays may also be energized in a predetermined sequence to reduce the amount of information necessary to be passed back to the computer  36  or PIM  44  at any given time. This sequential energizing of transducers  18  may be desirable when using a multiplexer switch  46  as described above. 
     In the embodiments of the medical device  10  that include an angioplasty balloon  48 , the medical device  10  is located in a vessel such as a coronary artery so that the angioplasty balloon  48  is at a desired location. Fluid is passed into the inflation port  58  where it travels through the duct  56  to inflate the angioplasty balloon  48  as is well understood in the art. The transducers  18  may be fired before, during and after activation of the angioplasty balloon  48  to assist in correctly locating the angioplasty balloon  48 , ensuring that the angioplasty balloon is inflating correctly and is applying the desired therapy (e.g., the vessel diameter is increasing) and confirming that the angioplasty procedure was successful after the angioplasty balloon  48  is deflated but before the medical device  10  is removed. The transducers  18  are operated and the diameter of the vessel determined as described above. 
     In embodiments of the medical device  10  that include a stent delivery balloon and stent assembly  50 , again the medical device  10  is located in a vessel such as a coronary artery so that the stent deployment balloon  52  of the stent delivery balloon and stent assembly  50  is at a desired location. Fluid is passed into the inflation port  58  where it travels through the duct  56  to inflate the stent deployment balloon  52  as is well understood in the art. Again, the transducers  18  are fired, as described above, before, during and after activation of the stent deployment balloon  52  to assist in correctly locating the stent  54 , ensuring that the stent deployment balloon  52  is inflating correctly and is applying the desired therapy (e.g., the vessel diameter is increasing and the stent  54  is deploying) and confirming that the stent  54  was successfully and fully deployed after the stent deployment balloon  52  is deflated but before the medical device  10  is removed. The transducers  18  are operated and the diameter of the vessel determined as described above. This embodiment of the medical device  10  confirms that the stent  54  is fully deployed and that the correct stent  54  is used. In the embodiments using either an angioplasty balloon  48  or a stent delivery balloon and stent assembly  50 , the preferred number of transducers  18  placed circumferentially around the body member  12  is from six to eight although fewer or more transducers  18  may be used depending on where the medical device  10  is used, the frequency of the emitted ultrasound or light signals, among the possible considerations. 
     The present invention has applicability wherever it is desirable to know the cross-sectional dimensions the space surrounding the device. Illustrative examples of these applications include, but are not limited to, diagnosing or treating non-thrombotic venous disease, coronary stable angina, placing or retrieving inferior vena cava (IVC) filters, replacing or repairing heart valves, placing peripheral drug eluting balloons (DEB), 
     Throughout this description, mention has been made of placing the medical device  10  in vessels. Vessel, as used herein, means any fluid filled structure or structure surround by fluid within a living body or, where ultrasound is not use, any structure that may be imaged and includes both natural and man-made structures. Examples of such vessels include, but are not limited to, organs including the heart, arteries, veins, liver, kidneys, gall bladder, pancreas, lungs, breasts; ducts; intestines; nervous system structures including the brain, dural sac, spinal cord and peripheral nerves; the urinary tract; rectum; vagina; as well as valves within the blood or other systems of the body. In addition to the previously listed natural structures, the medical device  10  may be used as described herein to calculate dimensions, image or otherwise take data on such man-made structures as, without limitation, heart valves, stents, shunts, filters and other devices positioned within the body, for example, a guide wire or guide catheter. 
     While the above description contains many specifics, these should not be construed as limitations on the scope of the invention, but rather as examples of preferred embodiments thereof. As a result, the description contained herein is intended to be illustrative and not exhaustive. Many variations and alternatives of the described technique and method will occur to one of ordinary skill in this art. Further, the medical device  10  has been described in connection with producing maps of the distance from the transducers  18  to the tissue of structure opposite the transducers  18  or the area around the transducers  18 . But, the medical device  10  may also be used to produce images such as intravascular ultrasound (IVUS) or OCT images as is well understood in the art. 
     Variations in form of the component pieces described and shown in the drawings may be made as will occur to those skilled in the art. Further, although certain embodiments of a medical device  10  have been described, it is also within the scope of the invention to add other additional components or to remove certain components such as the elongated tip  20 , multiple arrays of transducers  18 , switches  46  or proximal connectors  26 . Also, variations in the shape or relative dimensions of all of the various components of the medical device  10  or system  28  will occur to those skilled in the art and still be within the scope of the invention. 
     All these alternatives and variation are intended to be included within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompasses by the claims attached hereto. As a result, while the above description contains many specifics, these should not be construed as limitations on the scope of the invention but rather as examples of different embodiment thereof.