Abstract:
A modular ingestible capsule ( 15 ) comprising a capsule body ( 16 ) having an outer shell ( 21 ), a power supply ( 22 ), a transmitter ( 23 ) connected with the power supply, an antenna ( 24 ) connected with the transmitter, an activator ( 25 ) configured to activate the power supply, and an electrical coupling element ( 26 ) connected with the transmitter, a first modular sensing component ( 18 ) configured and arranged to connect to the capsule body and having an outer shell ( 28 ) configured and arranged to attach to the shell of the capsule body, a sensor ( 29 ) for sensing a parameter of an ingestible tract, and an electrical coupling element ( 32 ) connected with the sensor and configured and arranged to engage the electrical coupling element of the capsule body, whereby the first modular sensing component may be readily mechanically and electrically attached to the capsule body prior to ingestion of capsule by subject.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to ingestible capsules and, more particularly, to an ingestible capsule having interchangeable sensing components. 
       BACKGROUND ART 
       [0002]    Ingestible capsules are well-known in the prior art. Such capsules are generally small pill-like devices that can be ingested or swallowed by a patient. It is known that such capsules may include one or more sensors for determining physiological parameters of the gastrointestinal tract, such as sensors for detecting temperature, pH and pressure. 
         [0003]    It is also known that certain physiological parameters may be associated with regions of the gastrointestinal tract. For example, a 1988 article entitled “Measurement of Gastrointestinal pH Profiles in Normal Ambulant Human Subjects” discloses pH measurements recorded by a capsule passing through the gastrointestinal tract. It is known that pH has been correlated with transitions from the stomach to the small bowel (gastric emptying) and from the distal small bowel to the colon (ileo-caecal junction). 
         [0004]    U.S. Patent Publication Number US2007/0118012 discloses an imaging device having two optical heads, and discloses that domes may be placed over the optical heads and into abutment with a connecting sleeve so that the connecting sleeve and the domes form a closed housing that defines the boundary surface of the in-vivo device. International Publication Number WO 2006/0077535 discloses a medicament dispensing capsule in which individual reservoirs may be provided in respective modules which are interlocking and connectable. International Publication Number WO 2006/0070374 discloses a system and method for assembling a swallowable sensing device, including attaching a first piece of a shell to a second piece of a shell, where the attachment may include, for example, screwing the first piece to the second piece, welding or gluing the first piece to the second piece, snapping the first piece to the second piece or applying laser energy to a pigment in the first piece. 
       DISCLOSURE OF THE INVENTION 
       [0005]    With parenthetical reference to corresponding parts, portions or surfaces of the disclosed embodiment, merely for the purposes of illustration and not by way of limitation, the present invention provides a modular ingestible capsule ( 15 ) comprising a capsule body ( 16 ) having an outer shell ( 21 ), a power supply ( 22 ), a transmitter ( 23 ) connected with the power supply, an antenna ( 24 ) connected with the transmitter, an activator ( 25 ) configured to activate the power supply, and an electrical coupling element ( 26 ) connected with the transmitter, a first modular sensing component ( 18 ) configured and arranged to connect to the capsule body and having an outer shell ( 28 ) configured and arranged to attach to the shell of the capsule body, a sensor ( 29 ) for sensing a parameter of an ingestible tract, and an electrical coupling element ( 32 ) connected with the sensor and configured and arranged to engage the electrical coupling element of the capsule body, whereby the first modular sensing component may be readily mechanically and electrically attached to the capsule body prior to ingestion of the capsule by subject. 
         [0006]    The sensor may be selected of a group consisting of a pH sensor, a pressure sensor and a temperature sensor. The power supply may comprise a battery. The transmitter may be configured to transmit data to a remote receiver. The capsule body my further comprise a temperature sensor ( 27 ). The electrical coupling element of the capsule body may comprise a plug and the electrical coupling element of the modular sensing component may comprise a receptacle configured to receive the plug. The modular sensing component may further comprise a processor ( 31 ) connected with the sensor. The processor may be programmed to control the sampling rate of the sensor. The processor may be programmed to control the transmission burst duration and the rate of transmission bursts. The sensor may be an analog sensor ( 30 ) that provides an output voltage in response to stimuli. The modular sensing component may further comprise an analog-digital converter ( 41 ) configured to convert an analog signal from the sensor to a digital signal. The capsule body may further comprise a processor ( 74 ) connected with the electrical coupling element ( 75 ) of the body and the modular sensing component may further comprise an ID tag recognizable to the processor. 
         [0007]    The capsule may further comprise a second modular sensing component ( 20 ) configured and arranged to connect to the capsule body and having an outer shell ( 33 ) configured and arranged to attach to the shell of the capsule body, a sensor ( 30 ) for sensing a parameter of an ingestible tract, and an electrical coupling element ( 35 ) connected with the sensor and configured and arranged to engage the electrical coupling element of the capsule body, wherein the second modular sensing component may be interchangeably attached mechanically and electrically to the capsule body with the first modular sensing component. 
         [0008]    The capsule body ( 50 ) may comprise a second electrical coupling element ( 58 ) connected with the transmitter and the capsule may further comprise a second modular sensing component ( 20 ) configured and arranged to connect to the capsule body and having an outer shell ( 33 ) configured and arranged to attach to the shell ( 52 ) of the capsule body, a sensor ( 30 ) for sensing a parameter of the ingestible tract, and an electrical coupling element ( 35 ) connected with the sensor and configured and arranged to engage the second electrical coupling element of the capsule body, whereby the second modular sensing component may be mechanically and electrically attached to the capsule body prior to ingestion of the capsule by a subject. 
         [0009]    The sensor of the first modular sensing component may be different from the sensor of the second modular sensing component, and the sensor of the first modular sensor component may be a pH sensor ( 30 ) and the sensor of the second modular sensing component may be a pressure sensor ( 29 ). The sensor of the first modular sensing component may be the same as the sensor of the second modular sensing component, and the sensors may be pressure sensors. The transmitter may be connected directly to the power supply and the processor may communicate with the sensor bi-directionally. The electrical coupling element of the body may be connected to the power supply, and the electrical coupling element of the body may be connected directly to the power supply and the transmitter. 
         [0010]    In another aspect, the invention provides a method of measuring parameters of the gastrointestinal tract of a subject comprising the steps of providing a capsule body having an outer shell, a power supply, a transmitter connected to the power supply, an antenna connected with the transmitter, an activator configured to activate the power supply and an electrical coupling element connected with the transmitter, providing a first modular sensing component configured and arranged to connect to the capsule body and having an outer shell configured and arranged to attach to the shell of the capsule body, a sensor for sensing a parameter of an ingestible tract, and an electrical coupling element connected with the sensor and configured and arranged to engage the electrical coupling element of the capsule body, providing a second modular sensing component configured and arranged to connect to the capsule body and having an outer shell configured and arranged to attach to the shell of the capsule body, a sensor for sensing a parameter of an ingestible tract, and an electrical coupling element connected with the sensor and configured and arranged to engage the electrical coupling element of the capsule body, attaching one of the first or second modular sensing components to the capsule body, having a subject ingest the capsule, recording measurements from the sensor of the attached modular sensing component as the capsule passes through a gastrointestinal tract of the subject, and transmitting the measurements from a transmitter to a receiver located outside of the gastrointestinal tract of the subject. 
         [0011]    Accordingly, an object is to provide a modular capsule system in which different sensing components may be interchangeably used with a standard base component. 
         [0012]    Another object is to provide a method for customizing an ingestible capsule using interchangeable sensing components. 
         [0013]    These and other objects and advantages will become apparent from the foregoing and ongoing written specification, the drawings, and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic of a first embodiment of the modular ingestible capsule system. 
           [0015]      FIG. 2  is a front plane view of a first embodiment of the modular ingestible capsule. 
           [0016]      FIG. 3  is a longitudinal vertical sectional view of the modular capsule shown in  FIG. 2 , taken generally on line A-A of  FIG. 2 . 
           [0017]      FIG. 4  is an exploded view of the modular capsule shown in  FIG. 2 . 
           [0018]      FIG. 5  is a longitudinal vertical sectional view of the modular capsule shown in  FIG. 4 , taken generally on line B-B of  FIG. 4 . 
           [0019]      FIG. 6  is a top plan view of the pressure modular cap shown in  FIG. 1 . 
           [0020]      FIG. 7  is a transverse vertical sectional view of the modular cap shown in  FIG. 6 , taken generally on line C-C of  FIG. 6 . 
           [0021]      FIG. 8  is a top plan view of the pH modular cap shown in  FIG. 1 . 
           [0022]      FIG. 9  is a longitudinal vertical sectional view of the modular cap shown in  FIG. 8 , taken generally on line D-D of  FIG. 7 . 
           [0023]      FIG. 10  is a front plan view of the pH and pressure modular cap shown in  FIG. 1 . 
           [0024]      FIG. 11  is a transverse horizontal sectional view of the modular cap shown in  FIG. 10 , taken generally on line E-E of  FIG. 10 . 
           [0025]      FIG. 12  is a transverse horizontal sectional view of the modular cap shown in  FIG. 10 , taken generally on line F-F of  FIG. 10 . 
           [0026]      FIG. 13  is an exploded view of a second embodiment of the modular ingestible capsule. 
           [0027]      FIG. 14  is a longitudinal vertical sectional view of the modular capsule shown in  FIG. 13 , taken generally on line G-G of  FIG. 13 . 
           [0028]      FIG. 15  is a diagram of electrical connections for the modular capsule shown in  FIG. 5 . 
           [0029]      FIG. 16  is an exploded view of a third embodiment of the modular ingestible capsule. 
           [0030]      FIG. 17  is a longitudinal vertical sectional view of the modular capsule shown in  FIG. 16 , taken generally on line H-H of  FIG. 16 . 
           [0031]      FIG. 18  is a diagram of electrical connections for the modular capsule shown in  FIG. 17 . 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0032]    At the outset, it should be clearly understood that like reference numerals are intended to identify the same structural elements, portions or surfaces consistently throughout the several drawing figures, as such elements, portions or surfaces may be further described or explained by the entire written specification, of which this detailed description is an integral part. Unless otherwise indicated, the drawings are intended to be read (e.g., cross-hatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this invention. As used in the following description, the terms “horizontal”, “vertical”, “left”, “right”, “up” and “down”, as well as adjectival and adverbial derivatives thereof (e.g., “horizontally”, “rightwardly”, “upwardly” etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms “inwardly” and “outwardly” generally refer to the orientation of a surface relative to its axis of elongation, or axis of rotation, as appropriate. 
         [0033]    Referring now to the drawings and, more particularly, to  FIG. 1  thereof, this invention provides a modular ingestible capsule system for evaluating the gastrointestinal tract of a subject, of which a first embodiment is generally indicated at  14 . As shown in  FIG. 1 , system  14  generally includes a standard capsule body  16  that is adapted to be connected with multiple different but interchangeable modular caps  18 ,  19  and  20 . Body  16  houses certain standard electronics for the capsule and each of caps  18 ,  19  and  20  are attachable to body  16  and include different sensors or combinations of sensors for sensing parameters of the gastrointestinal tract of a subject. Body  16  and caps  18 ,  19  and  20  are designed such that the capsule user can choose the cap having the sensor or sensor combination desired at that time and can plug and attach the cap to the capsule body to provide the desired capsule just prior to having the patient ingest the capsule. Thus, system  14  allows the user to selectively customize the ingestible capsule using interchangeable sensing components. Multiple different modular components may be interchangeably used with standard base component  16 . While this embodiment describes modular components having pH and pressure sensors, caps having other types of sensors may be used, such as temperature sensors, blood sensors, and imaging sensors. 
         [0034]      FIG. 2  shows modular cap  18  connected to capsule body  16 . As shown, connected they form an elongated generally ellipsoid-shaped device  15 , somewhat resembling a medicament capsule. Capsule  15  is adapted to be ingested or otherwise positioned within a tract to sense pressure, pH and/or temperature within the tract and to transmit such readings. The capsule is generally provided with an outer surface or shell to facilitate easy swallowing of the capsule. In the preferred embodiment, capsule  15  is an autonomous swallowable capsule and is self-contained. Thus, capsule  15  does not require any wires or cables to, for example, receive power or transmit information. The pH, pressure and/or temperature data are transmitted from within the GI tract to a remote data receiver. 
         [0035]    As shown in  FIGS. 2-5 , standard capsule body  16  generally includes a power supply  22 , a transmitter  23 , an antenna  24 , an activation switch  25  and a temperature sensor  27  housed in a hard shell or casing  21 . One end  21  a of casing  21  is rounded and the other end terminates in an annular rim  21   b  and includes an electrical receptacle  26  adapted to receive a corresponding electrical plug. Power supply  22  and transmitter  23  are connected to each other and to electrical receptacle  26 . 
         [0036]    In this embodiment, power supply  22  is a lithium battery, although it is contemplated that other batteries may be used, such as a silver-oxide battery. Power supply  22  is adapted to power the electrical components of capsule  15  when in the gastrointestinal tract of a subject. 
         [0037]    To maximize its operation life, battery  22  is activated just prior to ingestion by way of a magnetic activation switch  25  adapted to turn the capsule on and off. In this embodiment, activation switch  25  is a circuit operating between battery  22  and the electrical components that selectively powers on and off the electronic components by way of a magnetic sensor which responds selectively to the presence, absence and/or polarity of a magnetic field. A number of conventional switches may be used. For example, an “active” reed switch system may be used, in which an external magnetic field actively holds a reed switch so that the circuit remains open. When the ingestible capsule is removed from the magnetic field, the reed switch closes the circuit, thereby activating the capsule. An alternative method is to use a passive reed switch and a magnetizable bias magnet asymmetric design manipulated by an external magnet. The circuitry of the capsule is selectively switched on and off depending on the magnetic state of the bias magnet, which determines the reed switch on/off state. The magnetic activation and deactivation circuit disclosed in U.S. patent application Ser. No. 11/899,316 entitled “Magnetic Activation and Deactivation Circuit and System,” the entire disclosure of which is incorporated herein by reference, may also be used in this embodiment. 
         [0038]    In this embodiment, transmitter  23  is a radio frequency (RF) transmitter that transmits measurements from capsule  15  when it is in the gastrointestinal tract of a subject to a remote receiver. Transmitter  23  transmits measurements at about  434  MHz. A portable data receiver worn by the subject receives and stores the measurements transmitted by transmitter  23  for later download through a docking station to a Windows PC compatible computer, such as a conventional laptop or a desktop. Antenna  24  amplifies the transmit power of transmitter  23  so that it can be received by the remote receiver. 
         [0039]    In this embodiment, body  16  also includes a temperature sensor  27  communicating with power supply  22  and electrical receptacle  26 . This temperature sensor may be used to compensate or provide a baseline relative to sensors in the modular cap that is connected to base  16 . 
         [0040]    Caps  18 ,  19  and  20  may be interchangeably used with body  20  to form an ingestible capsule. Cap  18  is adapted to be used with body  16  if the user desires to sense pressure within the gastrointestinal tract of the subject with capsule  15 . As shown in  FIG. 7 , cap  18  has an outer shell  28  that houses a processor  31  and pressure sensor assembly  29 . As shown, shell  28  has a top rounded end and terminates at an annular rim  28   c.    
         [0041]    Pressure sensor assembly  29  includes a chamber  38  between an inner wall  28   b  and a flexible membrane  28   a  of shell  28 . Chamber  38  is filled with a fluid. A rigid PCB arm  36  extends into the chamber and supports a conventional piezoelectric bridge  39 . As fluid presses against bridge  39 , it creates an electrical signal which corresponds to the pressure of fluid in chamber  38 . The fluid is a non-compressible medium that transfers a force onto the sensing mechanism for sensor  39 . In this embodiment, the fluid used is a dielectric gel. Alternatively, it is contemplated that other fluids, such as mineral oil, may be used or an inert gas may be used instead of a fluid. Thus, pressure sensor  39  is operatively arranged to sense pressure within chamber  38 . An analog to digital converter  41  is provided to convert the analog signal from sensor  39  to a digital signal. 
         [0042]    As shown in  FIGS. 6-7 , multiple chambers  38   a ,  38   c  with multiple pressure sensors  39   a ,  39   c  may be included on capsule  18 . In this embodiment, cap  18  is somewhat elliptical, and includes four chambers and four pressure sensors  39  located generally at the opposed corners on the major axis  37   b  and  37   d  and minor axis  37   a  and  37   c  of cap  18 . 
         [0043]    Pressure sensor assembly  29  is connected to and communicates with micro-processor  31 . Processor  31  controls the sampling rate of sensor  29  and is also connected through plug  32  and port  26  to transmitter  23  to control the RF transmission frequency and the information and data being transmitted. Processor  31  may also process signals received from sensor  29  and temperature sensor  27  and may provide other command or control signals to capsule components. The term processor as used herein refers to any data processor. Some examples of processors are microprocessors, microcontrollers, CPUs, PICs, PLCs, PCs or microcomputers. The processor described above is for purposes of example only. Thus, the term processor is to be interpreted expansively. 
         [0044]    Cap  20  is adapted to be used with body  16  if the user desires to sense pH within the gastrointestinal tract of the subject with capsule  15 . As shown in  FIG. 9 , cap  20  has an outer shell  33  that houses a processor  34 , an analog to digital converter  41 , and a pH sensor assembly  30 . In this embodiment, pH sensor assembly  30  comprises a conventional ISFET type pH sensor  40  on one side with a pH reference electrode  42  on the other. ISFET stands for ion-selective field effect transistor and the sensor is derived from MOSFET technology (metal oxide screen field effect transistor). A current between a source and a drain is controlled by a gate voltage. The gate is composed of a special chemical layer which is sensitive to free hydrogen ions (pH). Versions of this layer have been developed using aluminum oxide, silicon nitride and titanium oxide. Free hydrogen ions influence the voltage between the gate and the source. The effect on the drain current is based solely on electrostatic effects, so the hydrogen ions do not need to migrate through the pH sensitive layer. This allows equilibrium, and thus pH measurement, to be achieved in a matter of seconds. The sensor is an entirely solid state sensor, unlike glass bulb sensors which require a bulb filled with buffer solution. Only the gate surface is exposed to the sample. An analog to digital converter  41  is provided to convert the analog signal from sensor  40  to a digital signal. The pH ISFET sensor  40  and pH reference electrode  42  extend from the shell  33  in protective channels, such that the sensors are exposed to the medium of the gastrointestinal tract but are protected from breaking or causing damage. 
         [0045]    Micro-processor  34  is connected to and communicates with pH sensor  30 . Processor  34  controls the sampling rate of sensor  30  and is also connected through plug  35  and port  26  to transmitter  23  to control the RF transmission frequency and the information and data being transmitted. Processor  34  may also process signals received from sensor  30  and temperature sensor  27  and may provide other command or control signals to capsule components. 
         [0046]    Cap  19  is adapted to be used with body  16  if the user desires to sense both pH and pressure within the gastrointestinal tract of the subject with capsule  15 . As shown in  FIGS. 10-12 , cap  19  has an outer shell  49  that houses a processor  44 , an analog to digital converter  44 , a pH sensor  48 , a pH reference electrode  43 , and a pressure sensor assembly  46 . As shown, pH sensor  48  and reference electrode  43  are similar to the pH sensor assembly  30  of cap  20 . Pressure sensor assembly  46  is similar to pressure sensor assembly  29  of cap  19 , with a flexible membrane portion  49   a  of shell  49  and inner wall  49   b  of shell  49  defining a chamber  47  containing a piezoelectric bridge  45  operatively arranged to sense pressure within chamber  47 . Again, since the output from the sensors is an analog signal, an analog to digital converter  41  is provided to convert the signal from sensor  45  and  48  to a digital signal. Micro-processor  44  is connected to and communicates with pH sensor  48  and pressure sensor  46 . Processor  44  controls the sampling rate of sensors  48  and  46  and is also connected through a plug (not shown) and port  26  to transmitter  23  to control the RF transmission frequency and the information and data being transmitted from body  16 . Processor  44  may also process signals received from sensors  48  and  46  and temperature sensor  27  and may provide other command or control signals to capsule components. 
         [0047]    After activation and ingestion, capsule  15  senses and transmits measurements for at least 120 hours after activation. In the preferred embodiment, the range and accuracy of the sensors are generally 1 to 9.0 pH units with an accuracy of ±0.5 pH units, 0 to 350 mmHg with an accuracy of ±5 mmHg, and 25° to 49° C. with an accuracy of ±1° C. 
         [0048]    Caps  18 ,  19 ,  20  and capsule body  16  have both mechanical connecting elements and electrical connecting elements. As shown in  FIGS. 5 and 7 , the shell of the subject modular cap attaches to the shell  21  of body  16  in this embodiment by a snap connection. The bottom peripheral rim  28   c  of the subject cap includes an annular cavity  61 . A corresponding annular protrusion  62  is provided in the top rim  21   b  of shell  21  of body  20 . Annular cavity  61  in the subject cap is configured to receive protrusion  62  of the body. The body and subject cap are thereby pressed together until angular protrusion  62  snaps into corresponding cavity  61 , thereby holding the subject cap and body  16  together. However, it is contemplated that other types of connections may be used to attach the subject cap to body  16 . For example, shell  28  and shell  21  may include corresponding screw threads with matching grooves along a flange on their outer rims so that the two ends of the shells may be screwed together. Alternatively, the rims of shells  28  and  21  may be attached by gluing or bonding the two parts together or the shells may be threaded and twisted relative to one another to provide a connection. 
         [0049]    The electrical connection between the subject cap and body  16  is provided by an I/O connector having an electrical connecting input or plug  32 ,  35  on the subject cap and an electrical output connection, port or receptacle  26  in body  16 . Port  26  is adapted to receive either plug  32  or plug  35  and to electrically connect the subject components of the selected cap and capsule body  16 . To form the capsule, the user selects the desired cap, aligns the plug in the subject cap with receptacle  26  of body  16 , and then presses the cap and body together until they snap in place, by which an electrical and mechanical connection is formed between them. Thus, the subject cap and body  16  may be easily or readily connected together by the user. The body and subject cap may be connected by hand, and may also be releasably connected such that the subject cap and body may be easily or readily detached from each other. 
         [0050]    As shown in  FIG. 15 , power supply  22  is connected to transmitter  23  and temperature sensor  27  in capsule body  16  and is connected through port  26  and plug  32 / 35  to the subject sensors  29 / 30 , subject processor  31 / 34  and converter  41 . Power supply  22  is, as described above, activated by switch  25 . The subject sensors  29 / 30  are connected through analog to digital converter  41  to the subject processor  31 / 34 . Processor  31 / 34  is also connected through plug  32 / 35  and port  26  to transmitter  23 . Transmitter  23  is in turn connected to antenna  24 . 
         [0051]      FIGS. 13 and 14  show an alternate capsule body  50  which is adapted to allow for modular caps to be interchangeably attached to both ends of the body. As shown, a pressure sensing cap  18  is attached to one end of body  50  and a pH sensing cap  20  is attached to the other end of body  50 . Capsule body  50  includes the same internal components as with body  16  housed in a cylindrical shell  52 . However, rather then having a single electrical receptacle  51 , body  50  includes a second electrical receptacle  58  at the opposed end. Thus, electrical plug  32  of cap  18  may be inserted into receptacle  51  of capsule body  50 , and plug  35  of cap  21  may be inserted into receptacle  58  of capsule body  50  to provide an ingestible capsule that senses both pH and pressure. With this embodiment, different sensing configurations may be formed by the user as desired. For example, caps having different sensors may be attached to the ends of capsule body  50  or, alternatively, caps having the same sensors may be attached to the ends of capsule body  50 . As with the first embodiment, caps  18  and  20  and body  50  are connected both electrically and mechanically. Thus, shell  28  of cap  18  attaches to end  50   a  of shell  52  and shell  33  of cap  20  attaches to the other end  50   b  of shell  52 . As discussed above, in this embodiment the shells are also attached or connected using a snap connection. However, other connecting methods or features may be used to provide the attachment such that the capsule does not leak when it is ingested and passes through the gastrointestinal tract of the subject. 
         [0052]    Once the desired capsule is put together by the user, it is ingested by the subject. As the capsule passes through the gastrointestinal tract of the subject, the pH sensor and/or pressure sensor take measurements and body  16  transmits the measurements to a receiver being worn by the user, where they are stored. 
         [0053]      FIGS. 16-18  show a third embodiment  70  of the modular capsule. Capsule  70  is similar to the first embodiment in that capsule body  72  includes a power supply  22 , a transmitter  23 , an antenna  24 , an activation switch  25  and a temperature sensor  27  housed in a hard shell or casing  21 . However, in this embodiment capsule body  72  also houses microprocessor  74 . 
         [0054]    Cap  71  is similar to caps  18 - 20  in that it is attachable to body  72  and comes in different versions having different sensors or combinations of sensors for sensing parameters of the gastrointestinal tract of a subject. However, cap  71  differs in that it does not contain a microprocessor and instead contains a settable ID tag programmed into non-volatile memory  73 . The settable ID tag is used to indicate the type of sensor or cap being attached to capsule body  72 . For example, if cap  71  is a version that contains a pressure sensor  29  it has a first ID tag. If it is a version that contains a pH sensor it has a second and different ID tag. In this embodiment, the ID tag is programmed into an EEPROM or flash memory or set using a DIP switch during manufacturing, and the EEPROM or DIP switch is a I2C-bus compatible device which allows it to communicate directly through the I2C-bus to microprocessor  74  in capsule body  72 . Thus, in this embodiment there is no need for additional interfacing. A four position Dip Switch or 4-bit EEPROM allows for 16 different versions of modular sensing cap  71  to be identified and a five position Dip Switch or 5-bit EEPROM allows for 32 different versions of modular sensing cap  71  to be identified and used with a single body  72 . Once activated, the ID tag acts as a control line into processor  74 . The ID tag is read and variables within the operating program are set according to a look-up table. These variables may include parameters which are unique to the particular sensor on the subject cap  71 , such as the sampling rate of the sensor, the transmission burst duration and the rate of transmission bursts. 
         [0055]    Different versions of cap  71 , each version having a different sensor(s) may be attached to body  72  as in the first embodiment. As shown in  FIG. 18 , cap  70  includes an I-O connector having an electrical connecting input or plug  76  on the subject cap  71  and an electrical output connection, port or receptacle  75  in body  72 . Power supply  22  is connected to a transmitter  23 , temperature sensor  27  and processor  74  in capsule body  72 , and is connected through port  75  and plug  76  to the subject sensor(s), memory  73  and converter  41  in cap  71 . As with the first embodiment, power supply  22  is activated by switch  25 . The subject sensors are connected through analog to digital converter  41  and, through plug  76  and port  75 , to processor  74 . Temperature sensor  27  in body  72  is connected directly to processor  74 . Processor  74  is connected directly to transmitter  23  and transmitter  23  is in turn connected to antenna  24 . 
         [0056]    While the above embodiments have been described in relation to the gastrointestinal tract of a human, it is contemplated that the system may be used in connection with the gastrointestinal tract of other animals. 
         [0057]    The present invention contemplates that many changes and modifications may be made. Therefore, while the presently-preferred form of the improved modular capsule system has been shown and described, and a number of alternatives discussed, persons skilled in this art will readily appreciate that various additional changes and modifications may be made without departing from the spirit of the invention, as defined and differentiated by the following claims.