as shown in the drawings for purposes of illustration , the fig1 and 2 illustrate a subcutaneously implantable and percutaneously adjustable fluid flow control device , generally designated in the accompanying drawings by the reference numbers 10 . the fluid flow control devices 10 is intended for use in a surgically implanted physiological shunt system for draining fluid from one portion of the body to another . in order to connect , for example , the device 10 in such a system , the device includes an inlet connector 12 and an outlet connector 14 which each receive one end of a piece of surgical tubing ( not shown ). the ends of the surgical tubing are placed over the connectors 12 and 14 and secured thereon by a single ligature just inside of an annular ridge formed near the end of each connector . when the flow control device 10 is used in a drainage system intended for the treatment of hydrocephalus , the inlet connector 12 is fluidly connected with a proximal catheter which is inserted through the skull into a brain ventricle containing cerebrospinal fluid under pressure . the outlet connector 14 is fluidly connected to a distal catheter which serves to discharge cerebrospinal fluid to , for example , the atrium portion of a patient &# 39 ; s heart . ordinarily the flow control device 10 will be surgically implanted on the patient &# 39 ; s skull with a flap of skin overlying the device . to facilitate holding the device in its desired position after implantation , a generally flexible mounting plate can be provided with one or more suture holes . the highly reliable fluid flow control device which has a single flow path there through and a valve mechanism which can be percutaneously adjusted when the device is subcutaneously implanted by the use of the present invention . the flow control device 10 include a relatively rigid , molded plastic base invested within an electrometric casing which , together , define a fluid flow path through the fluid flow control devices from the inlet connector 12 to the outlet connector 14 . the valve housing includes a percutaneously adjustable valve mechanism which restricts the flow of fluid through the device 10 . coupled to the adjustable valve mechanism is a magnetic indication device that may be externally located using an indicator tool . the present invention provides an improved mechanism for determining the setting the adjustable valve mechanism . the flow control device is described in more detail in u . s . pat . no . 5 , 637 , 083 issued to bertrand et al . entitled “ implantable adjustable fluid flow control valve .” fig3 is a schematic diagram illustrating an improved electronic valve indicator and locator tool in accordance with an example embodiment of the present invention . in this embodiment , a locator tool 300 is shown with an indicator tool 305 being placed into position over its corresponding indicator position 303 . the locator tool 300 includes an electronic display 311 to provide graphical and textual information to a user while the locator tool is in operation . the locator tool 300 also includes a background compass module 307 to measure ambient and background magnetic fields without influence from a magnetic device coupled to the implantable flow control device . in operation , the indicator tool 305 operates as an electronic compass to detect the orientation of magnetic fields associated with the magnetic device coupled to the valve in the implanted flow control device . the orientation of the magnetic device provides an indication of the setting for the valve . the indicator tool 305 is placed into its corresponding location on the locator tool 300 once the locator tool 300 is placed near the patient at a location corresponding to the site of the implantable flow control device . typically , the indicator tool is keyed to place the tool 305 into a pre - defined orientation relative to the locator tool 300 . this keying mechanism assists in placing the indicator tool 305 directly over an implanted flow control device once the flow control device has been identified and properly oriented relative to the locator tool 300 . the indicator tool 305 obtains its reading for the detected orientation of the magnetic field . this reading is communicated to the locator tool 300 for use in determining the setting for the valve . the reading obtained from the indicator tool 305 corresponds to magnetic fields that are a combination of a magnetic field generated by the magnetic device coupled to the valve of the implanted flow control device and ambient background magnetic fields . the reading from the indicator tool 305 is then processed to subtract an estimate for the ambient background magnetic fields obtained from the background compass 307 to generate a orientation for the magnetic field generated just by the magnetic device coupled to the valve of the implanted flow control device . the background compass 307 provides the ambient background magnetic field estimate when the background compass 307 is located within the locator tool at a position significantly separated from the expected location of the magnetic device coupled to the valve of the implanted flow control device when in place near a patient . because the magnetic field typically observable at a distance of 12 cm from a typical magnetic indicator device coupled to an implantable flow control device is generally less than 5 milligauss , the indicator tool must be placed as close as possible to the flow control device to permit the indicator tool to detect this magnetic field within the earth &# 39 ; s background magnetic field typically observed to be approximately 500 milligauss . as such , a background compass located far enough away from the implanted flow control device will not readily detect magnetic fields from the magnetic device coupled to the valve of the implanted flow control device . fig4 is a block diagram illustrating internal electronic modules used in implementing an embodiment of the indicator and locator tool of fig3 . tool set used to determine a valve setting and modify the valve setting on an implantable flow control device typically comprises three components : a locator tool 400 , an indicator tool 401 , and an adjustment tool 402 . the locator tool 400 typically provides a base unit that is used to locate the implanted flow control device in a patient . when the locator tool 400 is placed above the implanted flow control device near a patient , either the indicator tool 401 or the adjustment tool 402 is aligned with the locator tool 400 to orient either tool 401 - 402 into a proper position to perform its associated task . the locator tool includes a set of modules to perform its functions . these modules include a display module 411 , a processing module 410 , a background compass module 412 , and a target compass interface module 413 . the display module 411 is a display device for providing a user with graphical and textual information associated with the operation of the locator tool 400 . this display device 411 illustrates a setting for a valve on the implanted flow control device using the magnetic field data obtained from the background compass 412 and the indicator tool 401 . the processing module 410 is a programmable processing module to perform all control and data processing functions of the locator tool as well as its communication and control functions over the operation of the indicator tool . the background compass 412 is an electronic compass comprising one or more magnetic field detector devices used to measure the orientation of ambient background magnetic fields . as noted above , the background compass module is physically located within the locator tool 400 far enough away from the position of the indicator tool when it is in an operating position to not be affected by magnetic fields generated by magnetic device coupled to the valve of the implanted flow control device . the compass interface module 413 provides a data communications channel between the indicator tool 401 and the modules within the locator tool 400 . the indicator tool 401 provides its orientation data for use in subtracting background magnetic field data to obtain a correct valve setting . the indicator tool 401 electrically communicates this data to the locator tool 400 through a pair of interface modules . electrically , the two interface modules are electrically coupled together . this electrical connection may be a connection cable between the locator tool 400 and the indicator tool 401 . alternately , both the locator tool 400 and the indicator tool 401 may possess electrical connectors that engage each other when the indicator tool 401 is placed into its corresponding position on the locator tool 400 once the locator tool 400 is placed above the flow control device implanted in a patient . of course , one skilled in the art will recognize other communication mechanisms including wireless communications channels constructed using ir or rf wireless communications may be used without deviating from the spirit and scope of the present invention as recited within the attached claims . the indicator tool 401 includes a target compass module 422 , a compass control processing module 420 , and a locator tool interface module 423 . the target compass module 422 is an electronic compass comprising one or more magnetic field detector devices used to measure the orientation of a target magnetic field when the locator tool 400 and the indicator tool 401 are in their respective locations above an implanted flow control device . the compass control processing module 420 is a processing module used to control the operation of the indicator tool when data is collected and subsequently communicated to the locator tool 400 . this processing module may comprise a programmable processing device to permit software to be developed to perform the processing tasks associated with the indicator tool 401 . one skilled in the art will recognize that this processing module may also be implemented as a custom control module using a state machine or similar control logic as is typically used in embedded processing applications . the indicator tool 401 and locator tool 400 are handheld devices that may be moved to place them into positions near a patient . as such , these tools are typically powered by mobile power sources such as batteries . as such , the complexity of these processing modules is minimized to reduce the needs for power consumption of the tools while in operation to maximize the battery life before the batteries are recharged or replaced . the locator tool interface module 423 provides an electrical interface for the communications channel described above between the locator tool 400 and the indicator tool 401 . typically this communications channel is a serial data channel that transmits data a single bit at a time as a sequence of one bit data values . the interface modules on both sides of the communications channel perform any parallel to serial and serial to parallel data transformations needed to utilize this communication channel . the adjustment tool 402 is a magnetic device that is placed into position once the locator tool is in place . the magnetic device in the adjustment tool 402 couples to the magnet within an implanted flow control device to allow a setting for the valve to be changed as desired . the operation the adjustment tool is discussed below in more detail in regards to fig8 . fig5 is a block diagram illustrating a general programmable processing system for use in a handheld device such as an improved electronic valve indicator tool and adjustment tool in accordance with an example embodiment of the present invention . in an exemplary embodiment of a handheld processing system 500 , computing system 500 is operative to provide a magnetic valve indicator tool processing system . those of ordinary skill in the art will appreciate that the magnetic valve indicator tool 500 may include many more components than those shown with reference to a computing system 500 shown in fig5 . however , the components shown are sufficient to disclose an illustrative embodiment for practicing the present invention . as shown in fig5 , magnetic valve indicator tool processing system 500 is used in connection with an implantable flow control device 10 as needed . the magnetic valve indicator tool processing system 500 also includes processing unit 512 , video display adapter 514 , and a mass memory , all connected via bus 522 . the mass memory generally includes ram 516 , rom 532 , and may include one or more mass storage devices , such as a removable memory device such as a compact flash , smart media , or secure digital memory card . the memory devices may store an operating system 520 for controlling the operation of magnetic valve indicator tool processing system 500 . it will be appreciated that this component may comprise a general purpose server operating system as is known to those of ordinary skill in the art , such as unix , mac os ™, linux ™, or microsoft windows ®. basic input / output system (“ bios ”) 518 is also provided for controlling the low - level operation of processing system 500 . the mass memory as described above illustrates another type of computer - readable media , namely computer storage media . computer storage media may include volatile and nonvolatile , removable and non - removable media implemented in any method or technology for storage of information , such as computer readable instructions , data structures , program modules or other data . the mass memory also stores program code and data for providing a software development and neural network analysis and training system . more specifically , the mass memory stores applications including magnetic valve indicator tool program 530 , and other programs 534 , and similar analysis tool applications 536 as may be needed . the magnetic valve indicator tool processing program 530 includes computer executable instructions which are executed to perform the logic described herein . the magnetic valve indicator tool processing system 500 also comprises input / output interface 524 for communicating with external devices , such as a touch screen and similar input devices , or other input devices not shown in fig5 . likewise , the magnetic valve indicator tool processing system 500 may further comprise additional mass storage facilities also not shown should additional data storage be needed . one skilled in the art will recognize that the processing system illustrated within fig5 may represent a set of processing components typically found within a handheld or similar dedicated processing system . of course , other processing systems including general purpose computing systems containing additional peripherals and user interface devices may also be used to implement the programmable processing according to various embodiments of the present invention without deviating from the spirit and scope of the present invention as recited within the attached claims . for example , a dedicated processing system may consist of a digital signal processor ( dsp ) for performing the required floating - point math , various internal memory types including flash , rom , ram , and fpga , some minimal external memory for the valve calibration system , and a user interface and display driver chip to run the switches and custom lcd display . a proprietary embedded operating system is and a specifically written application for implementing the indicator tool program may be included . fig5 illustrates an example of a suitable operating environment in which the invention may be implemented . the operating environment is only one example of a suitable operating environment and is not intended to suggest any limitation as to the scope of use or functionality of the invention . other well known computing systems , environments , and / or configurations that may be suitable for use with the invention include , but are not limited to , personal computers , server computers , hand - held or laptop devices , multiprocessor systems , microprocessor - based systems , programmable consumer electronics , network pcs , minicomputers , mainframe computers , distributed computing environments that include any of the above systems or devices , and the like . the invention may also be described in the general context of computer - executable instructions , such as program modules , executed by one or more computers or other devices . generally , program modules include routines , programs , objects , components , data structures , etc . that perform particular tasks or implement particular abstract data types . typically the functionality of the program modules may be combined or distributed as desired in various embodiments . processing devices typically includes at least some form of computer readable media . computer readable media can be any available media that can be accessed by these devices . by way of example , and not limitation , computer readable media may comprise computer storage media and communication media . computer storage media includes volatile and nonvolatile , removable and non - removable media implemented in any method or technology for storage of information such as computer readable instructions , data structures , program modules or other data . computer storage media includes , but is not limited to , ram , rom , eeprom , flash memory or other memory technology , cd - rom , digital versatile disks ( dvd ) or other optical storage , magnetic cassettes , magnetic tape , magnetic disk storage or other magnetic storage devices , or any other medium which can be used to store the desired information and which can be accessed by processing devices . communication media typically embodies computer readable instructions , data structures , program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media . the term “ modulated data signal ” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal . by way of example , and not limitation , communication media includes wired media such as a wired network or direct - wired connection , and wireless media such as acoustic , rf , infrared and other wireless media . combinations of any of the above should also be included within the scope of computer readable media . additionally , the embodiments described herein are implemented as logical operations performed by a programmable processing device . the logical operations of these various embodiments of the present invention are implemented ( 1 ) as a sequence of computer implemented steps or program modules running on a computing system and / or ( 2 ) as interconnected machine modules or hardware logic within the computing system . the implementation is a matter of choice dependent on the performance requirements of the computing system implementing the invention . accordingly , the logical operations making up the embodiments of the invention described herein can be variously referred to as operations , steps , or modules . fig6 a is a schematic diagram illustrating an improved electronic valve indicator and locator tool in accordance with another example embodiment of the present invention . fig6 b is a block diagram illustrating internal electronic modules used in implementing an embodiment of the indicator and locator tool of fig6 a . in this embodiment , the three piece locator , indicator and adjustment tool set operate in the same manner as discussed above with respect to fig3 and 4 respectively except that this embodiment does not include a separate background compass as discussed above . similarly , fig7 a is a schematic diagram illustrating an improved electronic valve indicator and adjustment tool in accordance with yet another example embodiment of the present invention . fig7 b is a corresponding block diagram illustrating internal electronic modules used in implementing an embodiment of the indicator and locator tool of fig7 a . in the embodiment of fig6 a and 6b , the compass module of the indicator tool 605 is used to generate magnetic field data for both ambient background magnetic fields and target magnetic fields . the locator tool 600 is held away from a patient with the indicator tool 605 in its proper place when magnetic field data is obtained for just the ambient background magnetic fields . this data is stored within the locator tool 600 . the locator tool 600 is next placed over the implanted flow control with the indicator tool 605 in place over its corresponding indicator position 603 and a second reading is obtained . the second reading corresponds to the magnetic fields that are a combination ambient background magnetic fields and target magnetic fields as discussed above . the locator tool 600 processes these two magnetic fields data values as described above to obtain the setting for the valve within the implanted flow control device . the electronic modules within the devices as shown in fig6 b perform the functions described above in regards to fig4 . the background magnetic fields data is generated by the compass module 622 in the indicator tool 601 and transmitted to the compass control module 620 and then through the communications channel of the interface modules 613 , 623 for storage within the processing module 610 . once the tools are placed over an implanted flow control device , the compass module 622 generated additional data that is again transmitted to the processing module 610 . the two sets of magnetic field data is processed in the processing module 610 to generate a setting value for the valve in the flow control device and the setting data is displayed to a user on the display module 611 . the adjustment tool 602 may be used as discussed below to change a setting for the valve as desired . the valve position detection process may be repeated once the valve has been adjusted to verify the new setting for the valve . fig7 b is another embodiment of a block diagram illustrating internal electronic modules used in implementing an embodiment of the indicator and locator tool 705 . in this embodiment , the electronics for the compass module 722 , processing module 710 , and display module 711 are all located within the indicator tool 701 . the compass module 722 measures the magnetic fields for both the ambient background fields as well as the target magnetic field and communicates the data to the processing module 710 via the compass control module 720 . because all of these electronic modules are located within the indicator tool 701 , a communications channel and corresponding interface modules are not needed . this embodiment places the electronic display 711 from the locator tool 700 to the indicator tool 705 over its corresponding indicator position 703 as shown in fig7 a . the adjustment tool 702 may be used as discussed below to change a setting for the valve as desired . the indicator tool 701 , however , may need to be larger in size to contain all of these electronic modules as well as a power supply , battery , and other associated components . the indicator tool 701 would also need to nest with the housing of the locator tool 700 . such an embodiment would , however , operate with existing locator tools that do not currently include any electronics . the packaging of this compass and corresponding electronics into a small indicator tool could present the limitations of any such design . the indicator tool may be implemented in a housing that is substantially mushroom shaped . a smaller bottom portion of the indicator tool 701 may contain the magnetic compass module in order to place them close to the valve of the implantable flow control device . such an arrangement permits the smaller bottom portion of the tool to nest within the locator tool . a larger cap part provides additional space as needed for additional electronics . one skilled in the art , however , would recognize that either embodiment works to implement the present invention as disclosed herein with the inclusion of the electronic modules within one and two tools is a matter of design choose within the scope and spirit of the present invention as recited within the attached claims . fig8 illustrates a diagram of an improved locator tool while used with an accompanying adjustment tool in accordance with an example embodiment of the present invention . once the current position of the valve is determined and displayed on display module 811 , the adjustment tool 805 may be used to alter the setting for the valve within the flow control device . the adjustment tool 805 corresponds to a magnetic coupling device that is placed over the locator tool 800 to orient the adjustment tool 805 directly over the magnetic indication device 801 that is part of the valve . the adjustment tool 805 magnetically couples to the magnetic indication device 801 such that a rotation of the adjustment tool 805 causes the magnetic indication device to rotate within the valve . this rotation of the magnetic indication device 801 changes the settings for the valve within the flow control device as the magnetic indication device 801 is directly coupled to the valve setting mechanism . the operation of the adjustment tool 805 is disclosed in additional detail with the published u . s . patent application to bertrand et al ., no . 2002 / 0022873 as identified above . fig9 illustrates a flowchart of a method for use of an improved indicator tool in accordance with an example embodiment of the present invention . the method for determining the setting of a valve within an implantable flow control device begins by determining an estimate for background magnetic fields 901 . next , the method for determining the setting of a valve within an implantable flow control device places the indicator tool 903 near the implantable flow control device within a patient . once the indicator tool is located as close to the flow control device as possible , the indicator tool detects an observed magnetic field 905 from all sources using a set of target compass module . the background magnetic fields may be subtracted from the observed values 907 to obtain a orientation for the magnetic indicator device coupled to the valve that is part of the implanted flow control device . as discussed above , the background magnetic fields may be measured using the separate a background compass module and a target compass module as well as measured using a single compass module with the indicator tool located in two positions . a method practiced using principles of the present invention may utilize either of these two device embodiments to perform the method . the orientation of the magnetic indicator device is compared to a known orientation of the flow control device to determine a setting 909 for the valve of the flow control device . the known orientation of the flow control device may be manually determined by requiring the indicator tool to be oriented to a particular position relative to flow control device . once the indicator tool has determined the setting for the valve , a user may utilize an adjustment tool to magnetically rotate and thus alter the setting of the valve as desired in the claims , any means - plus - function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures . thus , although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together , whereas a screw employs a helical surface , in the environment of fastening wooden parts a nail and a screw are equivalent structures . many embodiments of the invention have been described . various modifications may be made without departing from the scope of the claims . these and other embodiments are within the scope of the following claims .
the invention is directed toward a magnetic indicator tool used to determine the setting of an implantable medical device . the implantable medical device includes a magnetic indicator device coupled to a valve on the implantable medical device . external magnetic fields , specifically earth &# 39 ; s magnetic field , may interfere with a conventional compass and create an incorrect device setting indication . the magnetic indicator tool estimates the external magnetic fields to subtract the estimate from received data to minimize any influence that external magnetic field has on the accuracy of the device setting measurement .