Abstract:
A method and system for detecting lead adequacy and quality for leads used in devices that sense or deliver low levels of electromagnetic energy. The system includes leads attached to a package substrate having known electrical or optical characteristics. The package is adapted to interface with a testing device that allows an operator to ascertain whether the leads are appropriate for a desired task. The operator need not remove the leads from the package to perform the test. The lead testing system may be freestanding or integrated into a lead utilizing instrument.

Description:
This application is a Continuation-In-Part of co-pending U.S. patent application Ser. No. 09/126,864, filed Jul. 31, 1998, which in turn claims priority under 35 U.S.C. § 119(e), to previously filed U.S. Provisional Application No. 60/116,396, filed Jan. 19, 1999; and U.S. Provisional Application No. 60/133,983, filed May 13, 1999, the subject matter of which is incorporated herein by reference. This application also claims priority under 35 U.S.C. § 119(e), to previously filed U.S. Provisional Application No. 60/234,054 filed Sep. 20, 2000, the subject matter of which is incorporated herein by reference. 

   FIELD OF INVENTION 
   The present invention relates to medical testing devices utilizing or measuring electromagnetic radiation. More particularly, the present invention relates to a method and apparatus for ascertaining that the leads utilized in testing are the intended lead for the task, of the intended quality, an acceptable alternative lead, or an acceptable alternative quality of lead for particular medical testing scenarios. 
   BACKGROUND OF THE INVENTION 
   A wide variety of modern medical testing instruments utilize leads to either sense electromagnetic energy or to deliver electromagnetic energy for testing or for therapeutic reasons. 
   A variety of different medical testing regimens utilize test leads for sensing or receiving electromagnetic energy emanating from the human body. For example, electrocardiogram testing (EKG or ECG) senses electrical impulses associated with the beating of the heart. Electroencephalogram testing (EEG) senses electrical activity related to brain function. Electromyelogram testing (EMG) senses electrical activity related to the functioning of skeletal muscle. 
   These instruments often are utilized to sense extremely low power levels emanating from the living organisms such as the human body. Because of the low energy levels involved, small variations in the electrical characteristics of the electrical leads can create significant differences in results. 
   In general, the leads used with these instruments are used for tests that are acute in nature. That is, the leads are applied to the test subject for a relatively short period of time. The leads are not intended for long-term use. An example of long-term use would be the leads that are implanted with an implantable cardioverter/defibrillator or pacemaker. The leads involved there are required to be more robust than the leads in question here. In addition, since those leads are associated with expensive devices and surgical procedures and lead expense is relatively trivial in the scope of the entire operation cost is not a great concern. 
   Therefore, lead sets utilized with these acute testing and treatment instruments are often disposable in nature. They are intended for use only once and are then intended to be discarded. Because of this disposable nature the market for leads for acute use is more price sensitive than that for chronic leads. Nonetheless it is essential for accurate diagnosis and treatment that acute use leads be within the desired range of electrical parameter tolerances. 
   In addition, some medical testing instrumentation senses electromagnetic radiation in the ultraviolet, visible light or infrared wavelengths. For example, certain intracardiac catheters contain fiber optic leads that sense reflected light radiation from structures in the heart. In this application, the applicant will primarily refer to leads. It should be understood that for the purposes of this application the term ‘lead’ also includes fiber optic strands. The invention is equally applicable to leads using fiber optic strands to transmit light energy. 
   Because sensing leads may be used to detect extremely low power levels, minor damage or deterioration may create significant loss of sensitivity and thus alteration of testing results. Handling the leads more than necessary may accelerate damage to them. 
   Various leads are used in medical testing to stimulate biological activity. For example, certain types of cardiac testing provide stimulation to the heart in addition to sensing EKG activity. An example of such testing is disclosed in U.S. Pat. No. 6,129,678 to Ryan and Hoium. This application is incorporated herein in its entirety by this reference. 
   Lead sets can also be used to deliver electromagnetic energy for therapeutic reasons. For example, intracardiac catheters often are utilized to deliver energy for purposes of ablating tissue. Such electromagnetic energy may be delivered, for example, in the form of radio frequency energy or laser light energy. 
   Often, multi-purpose lead sets may be utilized. Multi-purpose lead sets may contain electrical leads for sensing, electrical leads for stimulating, electrical leads for therapeutic purposes, fiber optic leads for sensing or therapeutic purposes, or any combination thereof. 
   With the proliferation of leads used for medical testing purposes, a variety of problems arise. First, any type of lead set will suffer degradation of performance with use. In use, leads may be exposed to variations in temperature, bodily fluids, skin oils, atmospheric oxygen and high oxygen environments. Any of these factors will tend to lead to corrosion of metal parts of the lead as well as loss of the lead&#39;s insulator dielectric strength. For example, skin surface leads have primary attributes of impedance, inductance and capacitance. Over time, and with exposure to environmental factors, these qualities of skin surface leads can change. If these qualities change sufficiently, electrical impulses transmitted by use of the skin surface leads are altered. Thus, the data measured will be changed causing instrument readings to be imprecise, potentially leading to an erroneous diagnosis. 
   Additionally, certain types of medical testing leads may suffer degradation of their electrical or optical qualities over a period of storage. Again, corrosion, loss of dielectric strength or other deterioration may affect the electrical qualities of leads while in storage. 
   The proliferation of leads also creates a variety of potential problems created by the use of the wrong leads for a given circumstance. Multipurpose instrumentation may require different types of leads for different testing or treatment scenarios. 
   Lead sets may be very similar in appearance and, if reusable, once removed from their packaging may be difficult to identify. The use of the wrong set of leads for a given testing procedure may lead to degraded or altered data results and potentially erroneous diagnosis. In addition, leads used for stimulation or therapeutic purposes may not deliver the appropriate level of stimulating or therapeutic electromagnetic energy. This can result in over treatment or under treatment of the medical condition in question. 
   Under some circumstances there may be a need to perform medical testing when the desired lead set is unavailable. Under these circumstances it would be desirable to be able to determine whether an alternative lead set would provide acceptable results. In some circumstances instrumentation may be calibrated to a particular lead set to increase the precision of the result. 
   Many types of lead sets are provided in disposable configurations intended for a single use and then immediately discarded. With the increasing pressure to hold down costs there can be a temptation to reuse lead sets that are intended for only a single use. This activity increases the risk of erroneous diagnosis and also potentially increases the risk of infection if the lead set is intended to be sterile at its initial use. It would be desirable to be able to determine whether a lead set had previously been used and to prevent the reuse of lead sets that are intended for a single disposable use. 
   Thus, it would be desirable in the field of medical testing arts to be able to readily test leads prior to use, even prior to opening the packaging, to determine whether those leads have deteriorated in storage, to ascertain that they are the appropriate leads for the test or that they are an acceptable alternative set. In addition, it would be desirable to determine whether reusable leads have degraded from the rigors of use prior to their application. It would be further desirable to identify and/or disable reuse of single use leads so that they could not be reused beyond their desired intent. 
   SUMMARY OF THE INVENTION 
   The present invention solves many of the problems indicated above. The invention provides leads attached to a package having known electrical or optical characteristics. The package is adapted to interface with a testing device that allows the operator to ascertain whether the leads are appropriate for the desired task. 
   The system of the present invention generally includes packaging of known electrical or optical characteristics, a package testing interface, and a lead testing assembly including hardware and/or software to determine whether the leads in question fulfill the desired characteristics. The lead testing assembly may be freestanding or may be incorporated into an existing testing instrument. 
   Leads generally include an electrode or a connector for attaching to an electrode. For the purposes of this application the end of the lead that interfaces with the patient will be referred to as a lead termination. This term is intended to encompass electrodes, connectors to electrodes, catheters, fiber optic emitters or receivers and any other lead end that is distal from a patient testing instrument. 
   The lead terminations are releasably secured to the packaging so that they are in electrical or optical communication with the packaging. The packaging is connectable to the package testing interface thus creating an electrical or optical communication to the testing instrument. This allows the leads to be evaluated to ascertain whether the leads are appropriate for the desired task without the need to open the packaging. In the case of sterile leads this preserves the sterility of the leads. The verification of leads is simplified since it is not necessary to remove the leads from the packaging for testing. 
   Further, since the leads are protected by the package during testing and handling, sensitive leads may be tested numerous times without damage. Also, the interface allows for multiple connections and disconnections to the package without creating stress or wear on the lead terminations themselves, further protecting the integrity of the leads. 
   Isolation of the lead terminations in their connection to the packaging allows for testing of leads that operate at very low power levels without interference with one another. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic block diagram of the apparatus for detecting lead adequacy and quality of the present invention; 
       FIG. 2  is an alternative embodiment of the apparatus for detecting lead adequacy and quality of the present invention; 
       FIG. 3  is a schematic diagram of the lead package and package interface in accordance with the present invention; and 
       FIG. 4  is a schematic of the lead package, interface and algorithm of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1 and 3 , an apparatus  10  for detecting lead adequacy and quality in accordance with the present invention generally includes leads  12  enclosed in package  14 , testing interface  16 , testing subassembly  18  and connector interface  20 . 
   Leads  12  may be any conventional testing, therapeutic or ablating leads. Leads  12  typically include a plurality of lead terminations  22 , lead conductors  24  and connector  26 . Lead conductors  24  may include electrical wires, other electrical conductors, or fiber optic wires for carrying electromagnetic radiation in the form of light (including visible light, infrared light and ultraviolet light.) Connector  26  is adapted to receive lead conductors  24  and to connect them to an appropriate testing instrument  28 . Connector  26  includes appropriate electrical and/or optical connecting members. 
   Leads  12  may be used to sense or deliver signals that are electrical, magnetic or light energy related in character. Some examples of instruments where this apparatus and method may be employed are ECG, signal averaged ECG, external pacemakers, external defibrillators, EP pacing systems, pacing catheters, defibrillation catheters, RF ablation catheters, optical ablation catheters, implantable pacemakers, implantable defibrillators, Holter monitors, external neurological stimulators, internal neurological stimulators, EEG, EMG, external neuromuscular stimulators, internal neuromuscular stimulators, TENS and TNS. This list is exemplary and is not intended to be exhaustive. 
   Package  14  includes backing  30  which further includes an isolated lead pad  32  for each individual lead termination  22 . Each isolated lead pad  32  is adapted to releasably receive lead termination  22 . The mechanical connection between isolated lead pad  32  and lead termination  22  may be made by adhesives, clips, screws, clamps or any other means of connecting lead terminations or electrodes known to those skilled in the art. The electromagnetic connection between isolated lead pad  32  and lead termination  22  is adapted for the particular type of application. For example, isolated lead pad  32  provides an electrical contact for electrical leads, an inductive interface for magnetic leads or an optical transmission interface for fiber optic leads. 
   Testing interface  16  includes a plurality of lead pad connectors  24  and a package engaging member  36 . Testing subassembly  18  is interposed between testing interface  16  and connector interface  20 . Testing subassembly  18  includes electronic components  38  and software algorithms  40 . 
   Connector interface  20  is adapted to receive connector  26  and to attach each of leads  12 , whether they be electrical or optical in nature, to testing subassembly  18 . 
   Isolated lead pads  32  are configured to accept any of a variety of lead terminations and electrodes. Lead terminations include adhesive electrodes, screw attachments, pad electrodes, tines and helices. Any other type of lead termination is contemplated as being utilized with the present invention. For example, isolated lead pads  32  for use with an adhesive pad type electrode may be simple conductive plates of known electrical qualities. Isolated lead pads  32  for use with screw type electrodes may be a threaded bore adapted to receive the screw type electrode. Isolated lead pads  32  may be configured to receive optical leads, such as when associated with a laser ablation catheter. In this case, isolated lead pads  32  include a transmission medium of known optical qualities and an engagement member to releasably hold the catheter tip in contact with the transmission medium. Those skilled in the art will be able to create isolated lead pads of known electrical, magnetic or optical qualities for the myriad lead terminations that are used in the medical arts. 
   In another embodiment of the invention, isolated lead pads  32  are configured to distort, deform, tear or otherwise display an indication that the leads have been removed from the package. Removal of the leads may also create some change in the known electrical, magnetic or optical characteristics of isolated lead pads  32 . 
   In operation, lead connector  26  is connected to connector interface  20  and package  14  is connected to package engaging member  36 . Because package  14  includes isolated lead pads  32  the connection of package  14  to package engaging member  36  creates an electrical circuit in the case of electrical leads. In the case of optical or magnetic leads, an appropriate circuit is created as well. Each isolated lead pad  32  comes into contact with an associated corresponding lead pad connector  34 . Because isolated lead pads  32  are of a known electrical magnetic or optical quality, electronic components  38  in combination with algorithm  40  are able to test the leads  12  while still in the package  14 . The end result of this operation is that the quality and adequacy of leads  12  for a given purpose can be determined without the necessity of opening the package thus ensuring accurate testing for delivery of energy for a given medical situation. 
   In another embodiment of the invention, isolated lead pads  32  will indicate whether the leads have been removed from the package previously. This indication, whether it be due to distortion, deformation, tearing or some other indication that the leads have been removed from the package serves to warn the operator that the leads are intended for a single use and having been once used should not be used again. 
   In another embodiment of the invention, the characteristics of isolated lead pads  32  will be altered by the removal of leads  12 . Therefore, when the package  14  is connected to package engaging member  36 , the electronic components of the system for detecting lead quality and adequacy  10  will display an indication that the leads have been previously used and are no longer acceptable for use. 
   In operation, package  14  is engaged to testing interface  16 . Engaging package  14  to testing interface  16  connects connector  26  to connector interface  20  and connects isolated lead pads  32  each to a corresponding lead pad connector  34 . 
   Note that package  14  can be connected to testing interface  16  and connector interface  20  without placing significant stress on lead conductors  24 , lead terminations  22  or connector  26 . Connector  26  is a relatively robust component. Thus, connector  26  is well adapted to be connected and disconnected repeatedly. Lead conductors  24  and lead terminations  22  are relatively more subject to damage and wear. Since connection is limited to isolated lead pads  32 , the more delicate components of lead  12  are protected from harm. This allows for the repeated testing and verification of leads  12  if need be. 
   In an additional embodiment of the invention, when leads  12  are removed from package  14 , they are separated from backing  30 . Backing  30  is altered by the removal of leads  12 . This alteration both signals that the leads  12  have been previously used and prevents the repackaging and retesting of leads  12 . This effectively prevents the intentional or inadvertent reuse of leads  12  that are intended for a single disposable use. 
   The written description filed as U.S. Provisional Patent Application No. 60/234,054 is attached as appendix A and is hereby incorporated by reference and made part of this application. 
   The present invention may be embodied in other specific forms without departing from the spirit of any of the essential attributes thereof; therefore, the illustrated embodiment should be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.