Abstract:
A sensing probe assembly and method for locating a magnetic field emitted by an implanted medical device. The assembly has a housing containing a magnetic field sensor circuit having an indicator light and a magnetic switch. The assembly further has a structure for marking the location of the magnetic field. The method utilizes a marking system whereby at least four points forming at least two perpendicularly intersecting line segments are located and marked above the magnetic field. The intersection is then used as a reference point for performing a medical procedure on the implanted medical device.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to a magnetic sensing probe assembly and method for detecting and marking the location of an implanted medical device. Particularly, this invention relates to a magnetic sensing probe assembly and method for locating the source of a magnetic field emitted from an implanted medical device. The assembly and method provide for easily and conveniently locating the magnetic source in an implanted medical device and marking its location for purposes of conducting a medical procedure. 
     Related art devices have been found to be difficult to operate because of their physical dimensions, because they require sensory adjustments for various conditions or procedures, and/or because of their mechanical or antiquated design. The present invention overcomes the problems with the prior art and provides a convenient probe assembly for a user, for example a medical technician, practitioner, or physician, to precisely locate a magnetic material incorporated into or a magnetic field emanating from an implanted medical device and to physically mark the location of the magnetic material or field with a nonpermanent agent. Both the sensing and marking mechanisms are incorporated into the assembly. 
     It is an object of this invention to provide a sensing probe assembly constructed and arranged to locate magnetic material incorporated into or a magnetic field from a medical device or its components. Another object of the invention is to provide an improved sensing probe assembly which is accurate and easy to use. Another object of the invention is to incorporate a marking mechanism into the assembly so that the location of the magnetic material or field can be conveniently, physically, and nonpermanently marked. Yet another object of this invention is to provide a medical device which is compact, reliable, and economical. 
     SUMMARY OF THE INVENTION 
     This invention relates to a magnetic sensing probe assembly and method for detecting and locating an implanted medical device. The present invention is easily held in and controlled by one hand. The assembly comprises an elongated housing containing a light source or diode, a power source, a magnetic switch and a circuit for electrical connection between the light source and the magnetic switch. The housing has opposing ends, namely, a light end and a tip end. 
     The assembly of the present invention further has a marking means located on the tip end of the housing to mark the location of a source of a magnetic field on the tissue of a patient once the magnetic field has been detected. The magnetic source is accurately located by moving the magnetic sensing probe assembly across the area containing the medical device to establish two pairs of points above the source. The points are detected as locations where the light source illuminates as the magnetic switch detects a magnetic field. The points are marked by depressing the marking means on the patient&#39;s skin or tissue. The intersection of the line segments connecting the two pairs of points provides the precise location of the magnetic material or the magnetic field. This method can be used to locate a component of a medical device spatially aligned with the magnetic material or source, so that a medical procedure can then be performed on the medical device. 
     The present invention provides an assembly and method for using a magnetic sensing probe in an easy, quick, reliable and convenient manner to locate a source of a magnetic field and to mark its location, thereby marking the location of an implanted medical device, for example. Particularly the sensing probe assembly may be utilized to non-invasively locate an injection port of a tissue expander or implanted inflatable device to thereby permit the device to be filled with fluid. 
     These and other benefits of this invention will become clear from the following description by reference to the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a lateral cross-sectional view of the probe housing of the magnetic sensing probe assembly of the invention; 
     FIG. 2 is a lateral view of the magnetic sensing probe assembly being used to locate an implanted medical device; 
     FIG. 3 is a lateral view of a marking cover having a circular marking tip; 
     FIG. 4 is a bottom end view of the marking cover of FIG. 3; 
     FIG. 5 is a lateral view of a marking cover having a square marking tip; 
     FIG. 6 is a bottom end view of the marking cover of FIG. 5; 
     FIG. 7 is a lateral view of a marking cover having a triangular marking tip; 
     FIG. 8 is a bottom end view of the marking cover of FIG. 7; 
     FIG. 9 is a perspective view of the magnetic sensing probe assembly of the present invention; 
     FIG. 10 is a perspective view of the magnetic sensing probe assembly of the present invention showing the assembly in a disassembled state; 
     FIG. 11 is a perspective view of the magnetic sensing probe assembly in use with a magnetic implant port assembly; 
     FIG. 12 is a plan view showing the probe housing of the sensing probe assembly; 
     FIG. 13 is a plan view showing the marking cover of the sensing probe assembly; 
     FIG. 14 is an end plan view of the marking cover of FIG. 13; and 
     FIG. 15 shows the coordinate system used to locate an implanted medical device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention relates to a magnetic sensing probe assembly and method which is useful for medical technicians, practitioners and physicians to locate and mark the source of a magnetic field which is incorporated into a medical device, for example. The invention provides for the quick, convenient and reliable marking of an implanted device in a non-invasive manner. 
     FIG. 1 shows a lateral cross-sectional view of the magnetic sensing probe assembly  10  having an elongated housing  11  that encapsulates a magnetic switch  18 , a light source or light-emitting diode (LED)  15 , and a circuit for electrical connection between the magnetic switch  18  and LED  15 . For example, the electrical circuit structure disclosed in U.S. Pat. No. 4,296,376 may be used to interconnect magnetic switch  18  and LED  15 . Other circuits may also be used in accordance with the teachings of the present invention. The housing  11  has an elongated shape so that it may be conveniently held in one hand like a pencil and is preferably made of a nonmagnetic material. The housing  11  has a tip end  12  encapsulating the magnetic switch  18  and a light end  13  encapsulating the light-emitting LED  15 , as shown in FIG.  12 . The light end  13  of the housing  11  surrounding the LED  15  is transparent so that a user can clearly see when the diode or light source is illuminated. Optimally, the housing end  13  may be of a colored, transparent or translucent material, such as a polycarbonate or the like. 
     As shown in FIG. 2, the magnetic sensing probe assembly  10  enables a user to detect and physically mark the precise location of a magnetic material incorporated into an implant port  21  of an implanted medical device  20 , for example. The magnetic sensing probe assembly  10  includes a marking cover structure  16  for marking the magnetic location on the skin or tissue  22  of a patient. The marking cover  16 , further shown in FIGS. 13 and 14, is generally tubular in configuration and is constructed and arranged to fit over and hold onto the tip end  12  of the housing  11  encapsulating the magnetic switch  18 . The marking cover  16  is preferably made of any nonmagnetic material, such as an acetal homo-polymer composition or the like. The cover structure  16  has a marking tip  17  for physically marking the location of the magnetic implant port  21 . The marking tip  17  is constructed so that it is held on the tip end  12  of the housing  11 , and so that it can be depressed upon a patient&#39;s skin or tissue  22  to leave a nonpermanent physical mark thereon. The marking tip  17  is shown to have a peripheral indented portion which defines a geometric shape. While the marking tip may be of any shape or dimension, as shown in FIGS. 3-8, the cover tip is shown to have a geometric shape such as a circle  24 , a square  26 , or a triangle  28  which are shown on covers  23 ,  25  and  27 , respectively. The physical mark may be created by the tip or by a marking agent, such as nonpermanent ink, that coats the marking tip  17  before it is pressed upon the patient. The marking cover  16  can be removed and reattached to the housing  11  as desired by the user or it may be permanently affixed to or incorporated into the housing  11 . Both the housing  11  and marking cover  16  are of a material, as discussed above, which can be sterilized as required before using the sensing probe assembly  10  in a medical procedure. 
     FIG. 9 shows a perspective view of the magnetic sensing probe assembly  10 , having light end  13 , housing  11  and marking cover  16  with marking tip  17 . FIG. 10 shows the marking cover  16  with marking tip  17  removed from magnetic sensing probe assembly  10 , thereby showing the tip end  12  of housing  11 . FIG. 11 shows the magnetic sensing probe assembly  10  in use with a magnetic implant port  21 . Housing  11  is shown having light end  13  which illuminates when a magnetic material or field is sensed. Marking cover  16  with marking tip  17  can then be used to mark the location of the magnetic material. 
     An advantage of this invention is that a user can use the magnetic sensing probe assembly  10  with one hand to easily and quickly locate the precise location of the magnetic material or field. A medical device or component spatially aligned with the magnetic material, for example, an implant port may be located in a non-invasive manner. The location procedure is accomplished by using the assembly to detect and mark the periphery of the associated magnetic field, since both the sensing and the marking mechanisms are incorporated into a single, convenient design. 
     The method of the present invention uses the magnetic sensing probe assembly  10  to mark a coordinate system  30  on a patent&#39;s skin or tissue, as shown in FIG.  15 . The probe assembly is scanned or moved across an area of the patient&#39;s skin or tissue under which the medical device is implanted. The magnetic material incorporated into the medical device produces a magnetic field which is detectable outside the patient&#39;s body. The magnetic switch activates and causes the light tip of the probe assembly to illuminate when it senses a magnetic field. When scanning the probe assembly across the area of skin the magnetic switch will activate when it senses a magnetic field and cause the light tip to illuminate, and will deactivate when it no longer senses the field, causing the light tip to darken. One sweep across the area will establish one point  36  where the light tip illuminates and another point  37  where the light tip illuminates. The marking tip can mark these two points  36  and  37  which establish a horizontal line segment  32 . Upon sweeping the probe assembly perpendicular to the horizontal line segment  32  two more points  34  and  35  will become apparent where the light tip illuminates due to the magnetic switch sensing the magnetic field. These points  34  and  35  can be marked and establish vertical line segment  31 . The intersection  33  of these two line segments  31  and  32  can also be marked and represents the location of the implanted medical device which is spatially aligned with a magnetic material or field. This location is where the medical procedure can be performed. More than two line segments and four reference points may also be detected and marked. 
     As many changes are possible to the embodiments of this invention, utilizing the teachings thereof, the description above and the accompanying drawings should be interpreted in the illustrative and not the limited sense.