Abstract:
Improved wiring arrangements for sensor catheters are provided to reduce wire-to-wire cross-talk wherein wires connecting the sensor of the sensor catheter to a processing unit are divided into a plurality of wire bundles contained within respective sheaths, with the wires in wire bundle twisted together reduce electromagnetic signal interference among the individual wires, or between wire bundles.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional patent application Ser. No. 60/413,267, filed Sep. 23, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     This application relates to medical devices such as catheters that have sensors at their distal tips to which electrical wiring is connected. 
     Sensor catheters are used to gather information during medical procedures for diagnosing and treating patients. Ultrasonic imaging catheters, for example, may be used to gather ultrasonic images of a patient&#39;s blood vessels. Alternative imaging techniques also may be used, such as magnetic resonance imaging, optical coherence tomography and infrared imaging. During certain procedures, catheters may be used to gather a variety of physiological parameters such as temperature, pressure, pH, flow velocity and/or volumetric flow. Gradients or changes in physiological parameters across an area of interest may also be determined. 
     Sensor catheters are typically connected to control and analysis equipment, which may be used to generate images from raw imaging data and display physiological parameters. A number of wires must be run along the length of a typical catheter to connect the control and analysis equipment disposed at the catheter&#39;s proximal end to the sensor(s) disposed at the distal catheter tip. 
     In many instances, there are seven or more wires that convey power supply voltages, ground potential, drive signals, and raw sensor signals to and from the catheter sensors. These wires may be organized as a single cable bundle. However, cross-talk or noise among signal wires is a source of interference when using a sensor catheter to gather sensor measurements. This may adversely affect ringdown performance. 
     In view of the above, it would be desirable to provide an imaging catheter including improved wiring arrangements to reduce wire-to-wire cross-talk. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the present invention to provide a sensor catheter having improved wiring arrangements for reducing wire-to-wire cross-talk. 
     In accordance with the principles of the present invention, sensor catheters are provided having improved wiring arrangements that reduce wire-to-wire cross-talk. The wires are grouped in distinct subgroups such as pairs of wires or groups of three or more wires that carry related signals. Accordingly, a group of seven wires may be divided into two twisted wire pairs and one group of three twisted wires. In this manner, wire-to-wire cross-talk is reduced. 
     By way of example, in an ultrasonic imaging catheter, the two wires that carry sensor signals from the ultrasonic imaging catheter may be grouped together and twisted closely together as a pair. As a result, cross-talk between the two wires is reduced, especially when compared to wire arrangements in which all of the wires are arranged in a single bundle. In addition, wires associated with ultrasonic drive signals also may be grouped together as a pair. Likewise, wires carrying power supply and clock signals (e.g., for use by multiplexer circuits at the catheter&#39;s distal end) may be grouped together as a pair. 
     The above examples are merely illustrative arrangements. According to the present invention, sensor catheters having varying signaling needs and signal wires will require different wire subgroup arrangements. The resulting wire subgroup arrangements may be twisted together to form a single wire group formed of multiple wire subgroups. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects and advantages of the present invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG. 1  is a side view of a previously known sensor catheter system; 
         FIG. 2  is a side-sectional view of the previously known sensor catheter of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of a previously known wire bundle for a sensor catheter; 
         FIG. 4  is cross-sectional view of a first embodiment of a wiring arrangement for a sensor catheter constructed in accordance with the principles of the present invention; 
         FIG. 5  is cross-sectional view of a second embodiment of a wiring arrangement for a sensor catheter constructed in accordance with the principles of the present invention; and 
         FIG. 6  is cross-sectional view of a third embodiment of a wiring arrangement for a sensor catheter of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a previously known sensor catheter system  10  comprises catheter  12  including proximal end  12   a  attached to processing equipment  14  and distal end  12   b  including sensor assembly  16  comprising one or more sensors. By way of example, sensor assembly  16  may includes a temperature sensor, a pressure sensor, a pH sensor, a flow velocity sensor and/or a volumetric flow sensor for measuring temperature, pressure, pH, flow velocity and flow volume. Of course, sensor assembly  16  may include sensors other than those listed above. 
     Sensor assembly  16  also may include an imaging sensor, such as an ultrasound, magnetic resonance, optical coherence tomography or infrared imaging sensor. Imaging sensors are typically used to gather images from locations inside a patient&#39;s body during surgical and diagnostic procedures. Catheter  12  may be configured to gather images from inside a patient&#39;s blood vessels during percutaneous procedures such as cardiological or peripheral intervention. An illustrative catheter that may be used for ultrasound applications is described in commonly assigned U.S. patent application Ser. No. 10/233,870, filed Aug. 29, 2002. 
     Referring to  FIG. 2 , signals from sensor  16  are transmitted to and from processing equipment  14  via wire bundle  18  including a plurality of wires. Sensor assembly  16  may include an ultrasound sensor that transmits signals to processing equipment  14 , which processes the signal data and displays the resulting images on a suitable display screen. Alternatively, sensor assembly  16  may include other sensors that transmit different signals to the processing equipment. 
     Processing equipment  14  also transmits signals that control the operation of sensor assembly  16 . For example, if catheter  12  is an ultrasound imaging catheter, processing equipment  14  transmits drive signals for one or more transducer elements disposed within the sensor assembly. These drive signals cause the transducer elements to emit acoustic vibrations directed towards a target area within the patient&#39;s body. 
     Power supply signals and clock signals (e.g., for synchronizing the timing of circuitry within sensor assembly  16 ) also may be transmitted to sensor assembly  16  from processing equipment  14  via wire bundle  18 . In order to improve overall system performance, it is desirable to reduce cross-talk between the different wires, regardless of the type of signal being transmitted. 
     Referring now to  FIG. 3 , a previously known wiring arrangement  20  for a sensor catheter comprises a single wire bundle having six individual wires  20   a  radially surrounding central wire  20   b . Wiring arrangement further comprises outer sheath  21  for retaining the wires  20   a  and  20   b . This arrangement has the advantage of being relatively compact, but suffers from a relatively high degree of wire-to-wire cross-talk. 
     Referring to  FIG. 4 , a first embodiment of a wiring arrangement for sensor catheter  12  constructed in accordance with the principles of the present invention is described. Wiring arrangement  22  comprises first wire bundle  24  contained within sheath  25 , second wire bundle  26  contained within sheath  27  and third wire bundle  28  contained within sheath  29 . First wire bundle  24  includes wires  24   a  and  24   b , which are twisted together to assist in electrically isolating the wires from the environment, thereby reducing electromagnetic signal interference among the individual wires. Similarly, second wire bundle  26  includes wires  26   a  and  26   b  that are twisted together; third wire bundle  28  includes wires  28   a ,  28   b  and  28   c  that are twisted together. All three wire bundles  24 ,  26  and  28  are twisted together to form wiring arrangement  22  and housed within outer sheath  30 . 
     Referring to  FIG. 5 , a second embodiment of a wiring arrangement for sensor catheter  12  constructed in accordance with the principles of the present invention is described. Wiring arrangement  32  comprises first wire bundle  34  contained within sheath  35 , second wire bundle  36  contained within sheath  37  and third wire bundle  38  contained within sheath  39 . First wire bundle  34  includes wires  34   a  and  34   b , which are twisted together to assist in electrically isolating the wires from the environment, thereby reducing electromagnetic signal interference among the individual wires. Similarly, second wire bundle  36  includes wires  36   a  and  36   b  that are twisted together; third wire bundle  38  includes wires  38   a ,  38   b  and  38   c  that are twisted together. Unlike the embodiment of  FIG. 4 , wire bundles  34 ,  36  and  38  of the embodiment of  FIG. 5  are not twisted and retained within an outer sheath. 
     Referring to  FIG. 6 , a third embodiment of a wiring arrangement for sensor catheter  12  of the present invention is described. Wiring arrangement  42  comprises first wire bundle  44  contained within sheath  45 , second wire bundle  46  contained within sheath  47  and third wire bundle  48  contained within sheath  49 . The first pair of wires includes wires  44   a ,  44   b  and  44   c , which are twisted together to assist in electrically isolating the wires from the environment, thereby reducing electromagnetic signal interference among the individual wires. Similarly, second wire bundle  46  includes wires  46   a ,  46   b  and  46   c  that are twisted together; third wire bundle  48  includes wires  48   a ,  48   b  and  48   c  that are twisted together. All three wire bundles  44 ,  46  and  48  are twisted together to form wiring arrangement  42  and contained within an outer sheath  50 . 
     Twisting the wires in the wire bundles has been observed to reduce electromagnetic interference among the wires. In some embodiments, the wires are twisted in a clockwise direction, while in others the wires may be twisted in a counter-clockwise direction. Alternatively, wires within different bundles may be twisted in different directions depending upon the application of the sensor catheter. Moreover, multiple wire bundles may be twisted together to form a single wire group. When forming a single wire group from multiple wire bundles, the direction of wire bundle twisting preferably is opposite to the direction in which individual wires are twisted when forming the multiple wire bundles. 
     The wiring arrangements of  FIGS. 4-6  are merely illustrative. As would be appreciated by those of skill in the art, many different wiring arrangements are possible without departing from the scope of the present invention. For example, the wiring arrangement may include 2 or more wire bundles, each wire bundle including two or more individual wires. 
     Although preferred illustrative embodiments of the present invention are described above, it will be evident to one skilled in the art that various changes and modifications may be made without departing from the invention. It is intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the invention.