Abstract:
A system for detecting clinically-relevant features of a gastrointestinal (GI) tract of a subject. The system comprises an external magnetic field generator adapted to be affixed to a patient for generating at predetermined time intervals a magnetic field with respect to the subject. The magnetic field has a predetermined polarity and flux density, thereby establishing a patient coordinate system based upon the magnetic field. The system includes a capsule adapted to be swallowed by a subject. The system further includes at least one radiation source emitting X-ray or gamma radiation and at least one radiation detector. The radiation detector is configured to detect in a first energy window collimated X-ray fluorescence radiation from the X-ray contrast agent composition excited by the emitted radiation, and to detect a second energy window Compton-backscattered radiation from the X-ray contrast agent and the wall of the GI tract produced in response to the emitted radiation. The system includes a magnetic field detector configured to generate a first output responsive to a detected polarity and detected levels of flux density during exposure to the externally generated magnetic field. A processor generates a second output based upon relative changes in the first output, the first output varying as a function of relative changes in physical location or angular orientation of the capsule associated with movement of the capsule within the GI tract. A control unit configured to selectively enable or disable X-ray or gamma ray emissions from the capsule produced by the at least one radiation source based upon the second output, such that the GI tract is selectively irradiated upon detected movement of the capsule.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority of U.S. provisional application No. 61/344,867, entitled “Intra Body Capsule Motion Sensing and Position Determination,” filed on Oct. 29, 2010, the contents of which are incorporated herein by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure is directed generally to detecting motion of a capsule within the gastrointestinal tract of a patient and activating the capsule only when certain movements occur. More particularly, the present invention is directed to utilizing the correlation of capsule movement in the colon and a change in angular orientation as an indication for capsule movement in the colon. In addition, systems and methods for tracking changes in the position of the capsule are described as well as systems and methods for locating the position of the capsule in the patient frame of reference. 
       BACKGROUND 
       [0003]    Colorectal cancer is one of the leading causes of death in the Western world. Clinical evidence suggests that early detection of primary colorectal cancer leads to a 90% or better 5-year survival rate, while detection of the disease when it has already metastasized leads to poor prognosis with a 50% or less 5-year survival rate and a 30% recurrence rate. Colorectal cancer screening and early detection have a substantial positive impact on the prognosis of this malignancy. 
         [0004]    Some systems and methods directed at the detection of polyps and other clinically-relevant features that may harbor the potential for cancer of the gastrointestinal (GI) tract, particularly colorectal cancer, are discussed in U.S. Pat. No. 7,787,926, the contents of which are incorporated herein by reference. These systems and methods include a capsule designed to be swallowed by a patient and to travel through the GI tract. In a typical case, the trip can take between 24-48 hours after which the imaging capsule exits in the patient&#39;s feces. For example, a subject swallows a contrast agent, and, typically after a waiting period, a capsule comprising one or more gamma and/or X-ray radiation sources and radiation detectors. As the capsule travels through the GI tract, the radiation sources “illuminate” the vicinity of the capsule. The GI contents (including the contrast agent), GI wall, and tissue outside of the GI tract act as a scattering media for the emitted radiation, typically primarily through the process of Compton scattering. The scattered photons then travel back through the GI contents, which include the contrast agent. The radiation detectors count appropriately Compton-backscattered photons and transmit the count rate information to an external recording unit worn by the subject. 
         [0005]    The count rates collected by each detector per unit time interval are analyzed, typically only for predetermined photon energy windows. These data are presented to a physician in a manner that enables him to assess the likelihood that there is a polyp or some other anatomical deformation in the GI tract. In some embodiments, the data are also analyzed to indicate a general area of the colon where such a deformation may exist. These polyps or anatomical anomalies may be the result of a tumor beginning to grow within the GI tract. If the physician suspects the presence of a polyp or some other anatomical anomaly that may be cancerous or pre-cancerous, the subject is typically referred for further diagnostic testing, such as colonoscopic examination. 
         [0006]    Because the aforementioned process involves radiation of the human body, and because excessive radiation can have potentially adverse consequences on the patient, it is desirable to minimize the amount of time that the capsule is activated, that is, illuminating with radiation. Therefore, in such systems it is preferable to activate the capsule for scanning only when the capsule is moving through the GI tract. That is, it is not preferable to keep the capsule activated for scanning while it is stationary in the GI tract. 
         [0007]      FIG. 6  is a graph illustrating an example of a tracing of the position coordinates and the angular coordinates of a capsule in a patient. As detected by the magnetic tracking system and the accelerometer on board the capsule, movement in the XYZ trace can be seen to be correlated with a change in the angular orientation of the capsule as well as its relative position in the patient over time. Pressure changes are also measured in the capsule. 
         [0008]    In a clinical trial conducted by Check-Cap Ltd in January 2010, it was shown that there is very high correlation between capsule movements in the colon and change in angular orientation of the capsule as it was moving in the colon. This change in angular orientation was monitored by a magnetic tracking system (Motilis, Switzerland) that monitored a magnet that was embedded in the capsule. In addition, a 3D accelerometer (ST electronics) monitored the direction of the gravitational force vector. Both systems showed clear angular change of direction during movements of the capsule in the colon. 
         [0009]    It may therefore be desirable to provide systems and methods for sensing capsule movement in the GI tract and to activate the capsule, which in turn starts the capsule scanning, only upon sensing such movement. Capsule movement in the GI tract may be sensed by monitoring capsule movements in the colon and change in angular orientation of the capsule. Systems and methods of the disclosure utilize the correlation of capsule movement, which may occur due to changes in the relative location of the capsule as it transits the GI tract, as well as changes in the relative angular orientation of the capsule as it undergoes rotation within the GI tract. Consequently, detecting either event serves as a more reliable indication of actual capsule movement within the colon. In addition, systems and methods for tracking changes in the position of the capsule are described as well as systems and methods for locating the position of the capsule in the patient frame of reference. 
       SUMMARY OF THE INVENTION 
       [0010]    In various aspects, the present disclosure is directed to systems for detecting clinically-relevant features of a gastrointestinal (GI) tract of a subject. According to some aspects, the system may comprise an external magnetic field generator adapted to be affixed to a patient for generating at predetermined time intervals a magnetic field with respect to the subject. The magnetic field may have a predetermined polarity and flux density, thereby establishing a patient coordinate system based upon the magnetic field. A capsule adapted to be swallowed by a subject may include a radiation source emitting X-ray or gamma radiation and a radiation detector. In some aspects, the radiation detector may detect in a first energy window collimated X-ray fluorescence radiation from the X-ray contrast agent composition excited by the emitted radiation, and in a second energy window Compton-backscattered radiation from the X-ray contrast agent and the wall of the GI tract produced in response to the emitted radiation. In accordance with various aspects, a magnetic field detector may generate a first output responsive to a detected polarity and detected levels of flux density during exposure to the externally generated magnetic field. A processor may generate a second output based upon relative changes in the first output. The first output may vary as a function of relative changes in physical location or angular orientation of the capsule associated with movement of the capsule within the GI tract. The system may include a control unit configured to selectively enable or disable X-ray or gamma ray emissions from the capsule produced by the a radiation source based upon the second output, such that the GI tract is selectively irradiated upon detected movement of the capsule. 
         [0011]    In accordance with some aspects, the radiation source may include an X-ray generator and a power source, and the control unit selectively enables or disables radiation emissions by regulating power supplied to the X-ray generator based upon the second output. 
         [0012]    According to some aspects, the radiation source may comprise a radioisotope selected from the group comprising T1201, Xe133, Hg197, Yb169, Ga67, Tc99, Tc99m, In111, I131 and Pd100. 
         [0013]    In accordance with some aspects, the control unit may include a radiation shield movably configured with respect to the radiation source, and a motor configured to controllably reposition the radiation shield relative to the radiation source, such that the GI tract is selectively irradiated based upon the second output. 
         [0014]    According to various aspects, the magnetic field detector may comprise a magnetic compass. 
         [0015]    In accordance with various aspects of the disclosure, the external magnetic field generator may comprise magnets affixed at spaced apart locations on a belt to be worn by the subject. 
         [0016]    In some aspects, the magnets may comprise electromagnets and a controlled current generator. 
         [0017]    In accordance with some aspects, the controlled current generator varies the current supplied to each of the electromagnets. 
         [0018]    In various aspects, the present disclosure is directed to a system for detecting clinically-relevant features of a gastrointestinal (GI) tract of a subject. The system may comprise an external signal transmitter adapted to be affixed to a patient for generating at predetermined time intervals a transmission field with respect to the subject. The transmission field may have a predetermined amplitude and frequency, thereby establishing a patient coordinate system based upon the transmission field. A capsule adapted to be swallowed by a subject may include a radiation source emitting X-ray or gamma radiation and a radiation detector. In some aspects, the radiation detector may be configured to detect in a first energy window collimated X-ray fluorescence radiation from the X-ray contrast agent composition excited by the emitted radiation, and to detect in a second energy window Compton-backscattered radiation from the X-ray contrast agent and the wall of the GI tract produced in response to the emitted radiation. In accordance with some aspects, a transmission field detector may generate a first output responsive to a detected amplitude and frequency during exposure to the externally generated transmission field. The system may further comprise a processor configured to generate a second output based upon relative changes in the first output, the first output varying as a function of relative changes in physical location or angular orientation of the capsule associated with movement of the capsule within the GI tract. The system may include a control unit configured to selectively enable or disable X-ray or gamma ray emissions from the capsule produced by the radiation source based upon the second output, such that the GI tract is selectively irradiated upon detected movement of the capsule. 
         [0019]    In accordance with some aspects, the external signal transmitter comprises a transducer configured to generate radio frequency emissions. 
         [0020]    According to various aspects, the transmission field detector further comprises an antenna configured to receive said radio frequency emissions. 
         [0021]    In accordance with various aspects of the disclosure, the external signal transmitter comprises a transducer configured to generate ultrasound emissions. 
         [0022]    In some aspects, the transmission field detector further comprises a transducer configured to receive said ultrasound emissions. 
         [0023]    The present invention will be more fully understood from the following detailed description of embodiments thereof, taken together with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    In the drawings, 
           [0025]      FIG. 1A  is a schematic illustration of an exemplary screening system in accordance with various aspects of the disclosure; 
           [0026]      FIG. 1B  is a schematic illustration of an exemplary capsule of the system of  FIG. 1A  in accordance with various aspects of the disclosure; 
           [0027]      FIG. 1C  is a schematic illustration of an exemplary external data-recording unit of the system of  FIG. 1A  in accordance with various aspects of the disclosure; 
           [0028]      FIG. 2A  is a schematic illustration of an exemplary screening system in accordance with various aspects of the disclosure; 
           [0029]      FIG. 2B  is a schematic illustration of an exemplary capsule of the system of  FIG. 2A  in accordance with various aspects of the disclosure; 
           [0030]      FIG. 2C  is a schematic illustration of an exemplary belt of the system of  FIG. 2A  in accordance with various aspects of the disclosure; 
           [0031]      FIG. 2D  is a schematic illustration of an exemplary screening system in accordance with various aspects of the disclosure; 
           [0032]      FIG. 2E  is a schematic illustration of an exemplary magnet of the system of  FIG. 2D  in accordance with various aspects of the disclosure; 
           [0033]      FIG. 2F  is a schematic illustration of an exemplary screening system in accordance with various aspects of the disclosure; 
           [0034]      FIG. 2G  is a schematic illustration of an exemplary electromagnet of the system of  FIG. 2D  in accordance with various aspects of the disclosure; 
           [0035]      FIG. 3A  is a schematic illustration of an exemplary screening system in accordance with various aspects of the disclosure; 
           [0036]      FIG. 3B  is a schematic illustration of an exemplary capsule of the system of  FIG. 3A  in accordance with various aspects of the disclosure; 
           [0037]      FIG. 3C  is a schematic illustration of an exemplary belt of the system of  FIG. 3A  in accordance with various aspects of the disclosure; 
           [0038]      FIG. 3D  is a schematic illustration of an exemplary screening system in accordance with various aspects of the disclosure; 
           [0039]      FIG. 3E  is a schematic illustration of an exemplary adhesive member of the system of  FIG. 3D  in accordance with various aspects of the disclosure; 
           [0040]      FIG. 4A  is a schematic illustration of an exemplary screening system in accordance with various aspects of the disclosure; 
           [0041]      FIG. 4B  is a schematic illustration of an exemplary capsule of the system of  FIG. 4A  in accordance with various aspects of the disclosure; 
           [0042]      FIG. 5A  is a schematic illustration of an exemplary screening system in accordance with various aspects of the disclosure; 
           [0043]      FIG. 5B  is a schematic illustration of an exemplary capsule of the system of  FIG. 5A  in accordance with various aspects of the disclosure; 
           [0044]      FIG. 5C  is a schematic illustration of an exemplary adhesive member of the system of  FIG. 5A  in accordance with various aspects of the disclosure; and 
           [0045]      FIG. 6  is a graph illustrating the tracing of the position coordinates and the angular coordinates of a capsule in the GI tract of a patient. 
       
    
    
     DETAILED DESCRIPTION 
       [0046]    Reference is made to  FIG. 1A , which is a schematic illustration of a screening system  140 , in accordance with various aspects of the disclosure. The system  140  typically comprises an ingestible capsule  150  and an external data-recording unit  152 . For some applications, the data-recording unit  152  may be worn on the waist of a subject  154  (as shown in  FIG. 1A ) or elsewhere on the subject&#39;s body, such as the wrist (configuration not shown), etc. Alternatively, for some applications, the capsule  150  may comprise an internal data-recording unit, and the external data-recording unit  152  may not be provided. In these applications, the data recorded by the capsule  150  is retrieved after the capsule has been expelled from the body. 
         [0047]    Reference is now made to  FIG. 1B , which is a schematic illustration of an exemplary capsule  150 , in accordance with various aspects of the present disclosure. The capsule  150  may comprise at least one radiation source  160  adapted to emit gamma rays, X-rays, and/or beta electrons (i.e., radiation having an energy of at least 10 keV), at least one gamma and/or or X-ray radiation detector  162 , and, typically, at least one collimator  163  adapted to collimate the radiation produced by the radiation source  160 . For some applications, the radiation source  160  may comprise a radioisotope or a miniature radiation generator. 
         [0048]    In some aspects of the disclosure, radiation source  160  may comprise a miniature X-ray generator, such as those described in one or more of the following references: U.S. Pat. Nos. 6,134,300 and 6,353,658 to Trebes et al.; Haga, A. et al., “A miniature x-ray tube,” Applied Physics Letters 84(12):2208-2210 (2004); and Gutman, G. et al., “A novel needle-based miniature x-ray generating system,” Phys Med Biol 49:4677-4688 (2004). Such a miniature X-ray generator or X-ray tube may be used for radiation source  160  instead of a radioisotope to illuminate the colon contents with X-ray photons. Turning such a generator on and off as needed typically reduces exposure of the subject to radiation. In addition, the energy range can be better controlled and the flux may be higher for the on periods without increasing subject total exposure. 
         [0049]    According to various aspects, the capsule  150  may comprise one or more gamma and/or X-ray radiation sources and/or sources of beta electrons, such as T1201, Xe133, Hg197, Yb169, Ga67, Tc99, Tc99m, In111, I131 or Pd100. With the use of such radioisotopes as a radiation source, however, it is desirable to incorporate a radiation shield which can be selectively moved relative to the radiation source, thereby limiting irradiation of the GI tract only when needed, such as during periods when movement of the capsule within the GI tract has been affirmatively detected. 
         [0050]    The capsule  150  also typically comprises circuitry  164  (which, for some applications, includes a pressure sensor), a power supply  166 , such as a battery, a wireless communication device  167  for communicating with external data-recording unit  152  (communication device not shown), and a radiation shield  168 . The shield  168  may comprise a material having a high atomic weight and a high specific density, such as lead, tungsten, tantalum, or gold. In an embodiment of the present invention, the radiation source  160  and detector  162  are arranged to “observe” the entire 4 pi squared sphere (or a portion of it) surrounding the capsule. According to some aspects, the capsule incorporates an electromechanical control unit, comprising the radiation shield  168  and the radiation source  160  which are movable relative to one another via a low power actuator, such as a motor and power source (not shown), thereby selectively permitting and preventing exposure of GI lumen tissue by emissions from the source  150  based on their relative positions. For example, in some aspects, the source  160  may be stationary and the shield  168  movable. In some aspects, the shield  168  may be stationary and the source  160  movable. In some aspects, the shield  168  and the source  160  may both be movable. In the case where the radiation source comprises an electrically-powered X-ray generator, the control unit comprises a regulated power source which is activated when emissions are desired and deactivated when emissions are not desired, such as when the capsule is stationary. 
         [0051]    Reference is now made to  FIG. 1A . During a typical screening procedure using system  140 , an oral contrast agent  170  is administered to subject  154 . Contrast agent  170  is typically adapted to pass through a gastrointestinal (GI) tract  172  and be expelled with the feces, substantially without being absorbed into the blood stream. The contrast agent material may be similar to compounds used routinely for the study of the GI with X-rays, such as Barium sulfate liquid concentrate, iodine-based compounds, or other such materials. For some applications, additional appropriate contrast agents include Tantalum, Gadolinium, Thorium, Bismuth, and compounds of these materials. After the contrast agent is administered (e.g., several hours after the contrast agent is administered), subject  154  swallows capsule  150 . 
         [0052]    Capsule  150  travels through GI tract  172 , emitting gamma and/or X-ray radiation. Beginning at a certain point in time, capsule  150  records the Compton scattered gamma and/or X-ray photons that strike radiation detectors  162 . The count rate information received from each of the radiation detectors is typically stored together with a time stamp for that measurement. Within a time period typically of less than one second (e.g., several tens to several hundred milliseconds), it is assumed that the capsule and the surrounding colon wall and the contrast agent are in quasi-steady state. Taking small enough time intervals and integrating the counts over the small intervals allows for this quasi-steady-state assumption. The data may be stored in the capsule and sent by the capsule to the external recording unit from time to time, or after data-gathering has been completed. 
         [0053]    Reference is now made to  FIG. 1C , which is a schematic illustration of the external data-recording unit  152 , in accordance with an exemplary embodiment of the present disclosure. The data-recording unit  152  may comprise a receiver/memory unit  155 , a support electronics/battery unit  156 , an antenna  157 , and/or user controls  158 . In some aspects, the unit  152  may also include a strap  159 , such as a belt or wrist/arm strap, for coupling the unit to the subject  154 . 
         [0054]    Referring now to  FIG. 2A , an exemplary screening system  200  includes an exemplary capsule  250 , which is some aspects may be similar to the capsule  150  described above. The capsule  250  is sized and adapted to be swallowed by a patient  201  for diagnostic or treatment purposes. As shown in  FIG. 2B , the capsule  250  incorporates a magnetic field detector comprising a miniature magnetic compass  202  (such as, for example, YAS529 from Yamaha) and a processor  203  that is communicable with the magnetic compass  202 . For clarity of illustration, the capsule  250  is shown without the components described above with reference to capsule  150 . Referring now to  FIG. 2C , an exemplary belt  204  according various aspects of the disclosure is shown. The belt  204  may include one or more magnets  206 , such as, for example, permanent magnets or electromagnets, placed thereon. Additionally or alternatively, in some aspects, the magnet(s)  206  can be attached to an article of clothing, such as a vest, or can be attached to the patient  201  by an adhesive sticker, for example, as discussed below in connection with  FIG. 2D . It should be appreciated that there are numerous conventional ways the magnets  206  can be coupled with a patient  201 . In each case, the magnets  206  are positioned so that they are securely attached to the patient  201  and move with the patient  201 . This fixed positioning defines the magnets  206  in a patient coordinate system/frame of reference. 
         [0055]      FIG. 2D  illustrates an exemplary screening system  1200  including a patient  201  wearing one or more exemplary sticker magnets  207  and having swallowed the exemplary capsule  250 . An exemplary sticker magnet  207  is shown in  FIG. 2E .  FIG. 2F  illustrates an exemplary screening system  2200  including a patient  201  wearing an exemplary sticker electromagnet  207  and having swallowed the exemplary capsule  250 . An exemplary sticker electromagnet  207  is shown in  FIG. 2G . 
         [0056]    In use, referring to  FIGS. 2A-2E , a subject swallows a contrast agent, and, typically after a waiting period, swallows the capsule  250 . Eventually, after some time, the capsule reaches the colon of the GI tract. As the capsule  250  travels through the GI tract, the radiation sources of the capsule  250  “illuminate” the vicinity of the capsule  250  to enable imaging of the tract. When the capsule  250  stops moving and comes to rest, the capsule  250  may be deactivated to cease irradiating the GI tract, thereby avoiding unnecessary radiation of the patient and limiting potential side effects of the screening process. 
         [0057]    When the exemplary capsule  250  in the colon  205  starts to move, it performs a change in orientation as described above with reference to  FIG. 6 . The change in orientation of the capsule changes the orientation of the magnetic field (or fields, if a few magnets  207  are detected simultaneously by the magnetic compass  202 ) that the magnetic compass  202  in the capsule  250  detects. An algorithm of instructions programmed into the capsule processor  203  calculates the difference between the previous orientation of the capsule  250  and the current orientation of the capsule  250 , sampling in short time intervals, for example, typically from a few milliseconds to a few seconds. If a predefined threshold of capsule orientation change is reached, the processor  203  determines that the capsule  250  has changed orientation considerably from the last orientation and movement of the capsule is thus about to occur. 
         [0058]    According to some aspects, an adaptive algorithm is employed in the capsule  250  to adapt to changes and the level of changes in orientation of the capsule  250 . According to some aspects, the algorithm can be implemented in a unit external to the capsule  250 , which is configured to communicate with the capsule  250 . 
         [0059]    Referring now to  FIGS. 2F and 2G , according to some aspects, the system  2200  includes electromagnets  207  and the capsule  25   0  is communicable with a controlled current generator  208  for controlling the current of the one or more electromagnets  207  to vary the field of the electromagnet(s)  207 . Controlling the current of the electromagnet(s)  207  allows the algorithm to modify the magnetic flux of the electromagnet(s)  207  such that when the capsule  250  is far inside the body not close to the electromagnet(s)  207  on the patient  201 , the magnetic field can be intensified by applying more current to the electromagnet(s)  207 , thereby improving the sensitivity of the compass  202  within the capsule  250 . When the capsule  250  comes near the electromagnet  207 , it may be advantageous to reduce the electric current in the electromagnet  207  to reduce the magnetic flux, in order to prevent saturation of the magnetic compass  202  in the capsule  200 . In addition, the electromagnet(s)  207  can be switched on and off depending on the position of the capsule  250 , thus optimizing in real time the magnetic field that the capsule compass  202  senses. This further improves the sensitivity of the capsule  25   0  for motion detection. 
         [0060]    It should be appreciated that, according to some aspects, the decision as to whether the capsule  250  has moved is based on a correlation of at least one parameter coming from at least one sensor such as a pressure sensor, a strain gauge on the capsule  250 , a capacitive sensing on the capsule  250 , an accelerometer, and other parameters coming from the imaging data that the capsule  250  generates. 
         [0061]    According to some aspects, the electromagnets  207  are switched on one at a time. In response, the capsule  250  transmits the detected direction of the magnetic compass  202  relative to the magnetic field. Applying such a sequence allows the receiver (or the capsule  250 ) to gather information about the position of the capsule  250  by calculating the point of intersection of the directions to the magnetic field that were sensed by the capsule  250  and combines this information with the position of the external electromagnets  207  on the patient  201 . This enables the position of the capsule  250  in the patient frame of reference to be calculated. 
         [0062]    In another embodiment of this invention, the capsule  250  senses the switching of the external magnet and acts as in a UART (Universal Asynchronous Receive Transmit) port protocol to lock on the switching of the magnets and transmit relative orientation of the magnetic compass  202  to the magnet  207  that is on after the transit of the switching to the next magnet  207  has occurred. In this way, there is no need for RF protocol to be involved in the synchronization of the transmission of direction after magnet  207  switching. 
         [0063]    This exemplary procedure of switching each magnet  207  in its turn or switching a subset of the magnets  207  or modulating their current in a known way to manipulate the direction of the magnetic force vector detected by the capsule magnetic sensor can be repeated from time to time and allows tracking the capsule  250  in its movement in the GI tract. 
         [0064]    According to some aspects, a single, external fixed-field magnet (not shown) can be used to approximately locate the position of the capsule  200 . The fixed-field magnet can be brought near the body of the patient  201  and the capsule  250  can continuously send the direction of the magnetic “North” it is detecting via the magnetic compass  202  and the amplitude of the magnetic moment, so that the closest point to the capsule  250  from the outside can be determined. 
         [0065]    According to some aspects, magnets  207  on the patient  201  are placed with opposite pole direction. As the capsule  250  moves along the gastrointestinal tract, the magnetic force can be registered and the approximate position of the capsule  250  can later be deduced from the change of direction of the magnetic field as the capsule  250  moves to “see” one magnetic pole and then sensing the change to the opposite pole near a different magnet along the route of the capsule  250 . 
         [0066]    The influence of Earth&#39;s magnetic field may affect the aforementioned procedures. Two mechanisms can be used to compensate for this influence. First, with no permanent magnets on the body of the patient  201  (or with all the electro magnets switched off) the direction of the earth magnetic field can be determined and later compensated for when magnets on the patient  201  body are applied (or switched on). Second, the use of relatively strong magnets (typically a few hundred to a few thousand Gauss in relation to 0.5 Gauss of Earth&#39;s magnetic field) means that the Earth&#39;s magnetic influence on the direction of the capsule&#39;s internal magnetic compass  202  will be minimal when magnets are placed (or switched on) the patient  201 . 
         [0067]    Referring now to  FIGS. 3A-3C , an exemplary embodiment of another method of detecting motion of a capsule within the Gastro Intestinal tract of a patient and activating the capsule only when such movements occur includes use of an alternating magnetic system to sense a change in orientation and/or position of the capsule in the colon and hence capsule movement. In some aspects, such an alternating magnetic system may be similar to a magnetic position sensing such as those manufactured by Ascension http://www.ascension-tech.com/ and Biosense http://www.biosensewebster.com/products/navigation/. 
         [0068]    For example, as illustrated in  FIG. 3A , an exemplary screening system  300  includes an exemplary capsule  350 , which is some aspects may be similar to the capsule  150  described above. The capsule  350  is sized and adapted to be swallowed by a patient  301  for diagnostic or treatment purposes. As shown in  FIG. 3B , the capsule  350  includes a coil  302 , such as, for example, a miniature 3D coil, and a processor  303 . The 3D coil may comprise three coils that are each wound at 90 degrees relative to the other two coils, respectively. The processor  303  is communicable with the coil to pick up signals from the three channels of the coil. Referring now to  FIG. 3C , an exemplary belt  304  according various aspects of the disclosure is shown. The belt  304  may include one or more transmitters  306  such as, for example, a 3D coil with each coil at 90 degrees relative to the other two coils). In some aspects, the belt may include electromagnets. It should be appreciated that the transmitter  306  may attached to a vest to be worn by a patient, or may be attached to a patient by an adhesive sticker  307  ( FIG. 3E ). In any event, the one or more transmitter(s) are positioned so that they are securely attached to the patient and move with the patient, thus defining the transmitters in the patient system of coordinates. 
         [0069]    In use, when the exemplary capsule  350  in the colon starts to move, a change in orientation occurs, as described above relative to  FIG. 6 . The change in orientation of the capsule  350  in turn changes the orientation of the 3D coil  302  in the capsule  350  relative to the transmitter  306 , for example, an external 3D coil. The change in orientation of the capsule 3D coil  302  relative to the transmitter  306  changes the magnetic flux detected in the coils, and the processor  303  in the capsule  350  can compute and detect the change in orientation of the capsule. Change in orientation is usually associated with capsule movement, so that an algorithm in the capsule can use this information to trigger capsule scanning due to movement. 
         [0070]    According to some aspects, the processor  303  on the exemplary capsule  350  calculates the change in position due to change in magnetic flux detected by the 3D coil  302  on board the capsule  350 . The changes related to position movement are used by the processor  303  to determine when to start and stop scanning by the capsule  350 . Additionally, relative position information which is correlated to magnetic flux amplitude in the 3D coil  302  on board the capsule  350  can be transmitted from the capsule  350  to an external receiver (not shown) or stored in the capsule  350  for later analysis of the position of the capsule  350  in time relative to the external 3D coil transmitter  306  on the patient  301 . The calculation as to whether the capsule  350  has moved is based on a correlation of at least one parameter coming from at least one sensor such as a pressure sensor, an accelerometer, an alternating magnetic detector, and other parameters coming from imaging data the capsule generates. 
         [0071]    In another exemplary embodiment of a screening system including an alternating magnetic system, referring again to  FIG. 3A , the capsule  350  may include at least one coil and an electronic circuit that is in communication with the coil to pick up signals from the coil. On the patient, a transmitter coil or a number of transmitter coils or electromagnets are placed on a belt or vest or are attached to the patient by an adhesive sticker. The transmitter(s) is positioned so that it is well attached to the patient and moves with the patient, thus defining the transmitter(s) in the patient system of coordinates. 
         [0072]    When the capsule  350  in the colon  305  starts to move, it may change orientation or position. This in turn changes the magnetic flux picked up by the coil, and the controller in the capsule can compute and detect change in position or orientation of the capsule. In some aspects, the decision on whether the capsule has moved is based on a correlation of a few parameters coming from a few sensors such as a pressure sensor, an accelerometer, the alternating magnetic detector, and other parameters coming from the imaging data that the capsule generates. 
         [0073]    In another exemplary embodiment of a screening system including an alternating magnetic system, referring again to FIG. A, the capsule  350  incorporates at least one coil and an electronic circuit that is in communication with the coil to transmit signals from the coil. On the patient a receiver coil or a number of receiver coils are placed on a belt, vest or attached to the patient by an adhesive sticker. The receiver(s) is positioned so that it is well attached to the patient and moves with him, thus defining the receiver(s) in the patient system of coordinates. 
         [0074]    When the capsule  350  in the colon  305  starts to move, it may change orientation or position. This in turn changes the magnetic flux picked up by the coils on the patient body. This information is processed by electronic circuits and a controller on the patient body and is used to compute if the capsule has moved. This information in turn is transmitted to the capsule, and the controller in the capsule can compute and detect change in position or orientation of the capsule. 
         [0075]    In another exemplary embodiment of a screening system including an alternating magnetic system, referring again to  FIG. 3A , the capsule  350  incorporates at least one magnetic sensor such as a fluxgate magnetometer (e.g., FLC3-70 from Stefan Mayer Instruments) or MI magnetometer (e.g., MI-CB-1DK from Aichi Steel Ltd. Japan) and an electronic circuit that is in communication with the magnetometer to pick up signals. On the patient, a transmitter coil or a number of transmitter coils or electromagnets are placed on a belt or vest or attached to the patient by an adhesive sticker. The transmitter(s) is positioned so that it is well attached to the patient and moves with him, thus defining the transmitter(s) in the patient system of coordinates. 
         [0076]    When a capsule in the colon starts to move, the capsule may change orientation or position, which in turn changes the magnetic flux picked up by the magnetometer, and the controller in the capsule can compute and detect change in position or orientation of the capsule. The decision on whether the capsule has moved is based on a correlation of a few parameters coming from a few sensors such as a pressure sensor, an accelerometer, the alternating magnetic detector, and other parameters coming from the imaging data that the capsule generates. 
         [0077]    In another exemplary embodiment of a screening system including an alternating magnetic system, referring again to  FIG. 3A , the capsule  350  incorporates at least one coil and an electronic circuit that is in communication with the coil to transmit signals from the coil. On the patient, a magnetometer or a number of magnetometers (such as FLC3-70 from Stefan Mayer Instruments) magnetometer or MI magnetometer (e.g., MI-CB-1DK from Aichi Steel Ltd. Japan) are placed on a belt or vest or attached to the patient by an adhesive sticker. The magnetometer(s) is positioned so that it is well attached to the patient and moves with him, thus defining the magnetometer(s) in the patient system of coordinates. 
         [0078]    When a capsule in the colon starts to move, it may change orientation or position, which in turn changes the magnetic flux picked up by the magnetometer(s) on the patient&#39;s body. This information is processed by electronic circuits and a controller on the patient body and is used to compute if the capsule has moved. This information in turn is transmitted to the capsule, and the controller in the capsule can compute and detect change in position or orientation of the capsule. The decision on whether the capsule has moved is based on a correlation of a few parameters coming from a few sensors such as a pressure sensor, an accelerometer, the alternating magnetic detector, and other parameters coming from the imaging data that the capsule generates. 
         [0079]    Referring now to  FIG. 4A , an exemplary embodiment of another system  400  and method of detecting motion of an exemplary capsule  450  within the GI tract of a patient  401  and activating the capsule  450  only when such movements occur. The exemplary capsule  450 , in some aspects, may be similar to the capsule  150  described above. The capsule  450  is sized and adapted to be swallowed by a patient  401  for diagnostic or treatment purposes. As shown in  FIG. 4B , the capsule  450  includes includes at least one miniature accelerometer  404  and a processor  403  that is communicable with the accelerometer  404 . The accelerometer(s)  404  is configured to sense change in orientation of the capsule  450  in the colon and hence capsule movement. 
         [0080]    In use, when a capsule  450  in the colon  405  starts to move, the capsule  450  performs a change in orientation as described above in connection with  FIG. 6 . This change in orientation of the capsule  450  in turn changes the orientation of the accelerometer  404 , which is directed towards the center of Earth gravity. This change in direction of the accelerometer  404  can signify change in orientation, which can be linked to capsule movement in the colon  405 . The controller/processor  403  in the capsule  450  can use this information to decide when to start and stop scanning, that is, illuminating the GI tract with radiation. 
         [0081]    It should be appreciated that by using more than one accelerometer, it may be possible to detect acceleration differences between the two or more accelerometers. This information can be also be used to sense if there is movement of the capsule  450 , and hence an algorithm including instructions stored in the controller/processor  403 , for example, in the capsule  450  can use this information to trigger capsule scanning due to capsule movement. 
         [0082]    It should also be appreciated that by using one or more accelerometers  404  in the capsule  450  and one or more accelerometers (not shown) on the patient&#39;s body, it is possible to detect acceleration differences between the capsule  450  and the body-worn receiver accelerometers. This information can be used to sense if there is relative movement or relative change in orientation and hence, an algorithm in the capsule  450  or in an external receiver (not shown) can include instructions that use this information to trigger capsule scanning due to capsule movement. 
         [0083]    In some aspects of the disclosure, the processor  403  in the capsule  450  calculates the change in position of the capsule  450 . The changes related to position movement are used by the capsule processor  403  to determine when to start and stop scanning by the capsule  450 . Additionally, relative position information which is correlated to acceleration differences detected on board the capsule  450  can be transmitted from the capsule  450  to the external receiver (not shown) or stored in the capsule  450  for later analysis of the position of the capsule in time relative to the external transmitter (not shown) on the patient  401 . According to various aspects, the calculation as to whether the capsule  450  has moved is based on a correlation of at least one parameter coming from at least one sensor such as a pressure sensor, accelerometer, the alternating magnetic detector, and other parameters coming from the imaging data that the capsule  450  generates. 
         [0084]    Referring now to  FIG. 5A , an exemplary embodiment of another system  500  and method of detecting motion of an exemplary capsule  550  within the GI tract of a patient  501  and activating the capsule  550  only when such movements occur. The exemplary capsule  550 , in some aspects, may be similar to the capsule  150  described above. The capsule  550  is sized and adapted to be swallowed by a patient  501  for diagnostic or treatment purposes. As shown in  FIG. 5B , the capsule  550  includes an ultrasonic localization system to sense change in orientation and/or position of the capsule  550  in the colon  505  and hence capsule movement. For example, the capsule  550  includes one or more miniature ultrasonic transducers  503  tuned to receive externally generated ultrasound emissions and generate a first output responsive to the detected amplitude and frequency of such ultrasound transmissions, and a processor  502  that is communicable with the transducers  503 . On the patient, a transmitting ultrasonic transducer or a number of transmitters  507 , as shown in  FIG. 5C , may be placed on a belt or vest, or attached to the patient  501  by an adhesive sticker, as shown in  FIG. 5A . The transmitter(s)  507  is positioned so that it is securely attached to the patient  501  and moves with the patient  501 , thus defining the transmitter(s) in the patient system of coordinates. 
         [0085]    In use, when a capsule  550  in the colon  505  starts to move, a change in orientation occurs as described above, thereby changing the orientation of the ultrasonic transducers  503  in the capsule  550  relative to the external ultrasonic transmitter  507 . This change in relative orientation changes the amplitude of the ultrasound signal received by the transducers  503  on the capsule  550 . This change in relative amplitude received by the capsule transducers  503  can signify change in orientation of the capsule  550 , which can be linked to capsule movement in the colon  505 . In turn, the processor  502  will identify relative changes in the detected ultrasound emissions over time and generate a second output associated with detected movement of the capsule within the GI tract. The processor/controller  502  in the capsule  550  can use this information to decide when to start and stop scanning by the capsule, thereby limiting scanning radiation emissions to the adjacent body tissue only when needed, such as when the capsule is moving within the GI tract. 
         [0086]    It should be appreciated that by using more than one ultrasonic transducer  507  as transmitters and transmitting a pulse (or a modulated pulse) from the external transmitters  507 , it is possible to detect time differences between the two or more coming signals. Taking into account the velocity of sound in the tissues, it is possible to estimate the relative distance of the capsule  550  from the transmitters  507  and hence calculate if there is a change in position of the capsule  550 . This information can be to sense if there is movement and hence, an algorithm in the capsule  550  can use this information to trigger capsule scanning due to movement. 
         [0087]    In another embodiment of this invention, the capsule  550  also calculates the change in position of the capsule  550 . These changes related to position movement are used by the capsule controller  502  to decide when to start and stop scanning, that is, illumination by the capsule  550 . Additionally, relative position information which is correlated to ultrasonic time difference detected on board the capsule  550  can be transmitted from the capsule  550  to an external receiver (not shown) or stored in the capsule  550  for later analysis of the position of the capsule in time relative to the external transmitter  507  on the patient  501 . 
         [0088]    It should be appreciated that the calculation as to whether the capsule  550  has moved is based on a correlation of at least one parameter coming from at least one sensor such as a pressure sensor, an accelerometer, an alternating magnetic detector, an ultrasonic detector and other parameters coming from the imaging data that the capsule  550  generates. 
         [0089]    Referring again to  FIG. 5A , in another exemplary embodiment of a screening system a method of detecting motion of a capsule within the GI tract of a patient and activating the capsule only when such movements occur may include using a radio frequency (RF) system, rather than an ultrasound system, to sense change in orientation and/or position of the capsule in the colon and hence capsule movement. For example, the capsule  550  may include at least one RF antenna and an electronic circuit that is communicable with the antenna to pick up RF signals generated by an external RF transmitter, or a number of RF transmitter antennae, carried on a belt or a vest worn by the patient, or are otherwise attached to the patient by an adhesive sticker. The antenna(e) is positioned so that it is securely attached to the patient and moves with the patient, thus defining the antenna in the patient system of coordinates. 
         [0090]    Consequently, when the capsule in the colon starts to move, a change in relative orientation of the capsule will change the detected amplitude of the RF transmission received by the RF transducers within the capsule  550 . This change in relative amplitude received by the capsule transducers can signify change in orientation of the capsule  550 , which can be linked to capsule movement in the colon  505 . In turn, the processor  502  will identify relative changes in the detected RF emissions over time and generate a second output associated with detected movement of the capsule within the GI tract. The processor/controller  502  in the capsule  550  can use this information to decide when to start and stop scanning by the capsule, thereby limiting scanning radiation emissions to the adjacent body tissue only when needed, such as when the capsule is moving within the GI tract. 
         [0091]    Additionally, the calculation as to whether the capsule has moved can also be based upon a correlation of more than one parameter sensed by multiple sensors incorporated into the capsule, such as a pressure sensor, an accelerometer, RF power, an alternating magnetic detectors, and other parameters coming from the imaging data that the capsule generates. 
         [0092]    According to some aspects, an RF signal is transmitted from the capsule in sync with an alternating electromagnetic signal transmitted from at least one coil in the capsule. On the patient, an RF receiver antenna or a number of RF receiver antennae are placed on a belt, vest or attached to the patient by an adhesive sticker. The antenna(e) is connected to an RF receiver. RF signals received on the patient are used to sync the electronic circuits that are connected to at least one coil or other magnetic sensor positioned so that they are securely attached to the patient and move with the patient, thus defines them in the patient system of coordinates. In this way, feeble electromagnetic signals picked up by the magnetic sensor can be detected with improved sensitivity since the exact timing of each such signal is known synced with the RF signal. This allows improved detection since noise picked up at times in which there is no RF transmission, hence no electromagnetic transmission can be ignored. 
         [0093]    According to some aspects, the exemplary capsule serves as the receiver, and the transmissions of the electromagnetic signals are transmitted from the coils placed on the patient belt, sticker, etc. in some aspects, an RF signal is transmitted from the external receiver in sync with an alternating electromagnetic signal transmitted from at least one coil on the patient belt or vest. On the patient, an RF transmitting/receiving antenna or a number of RF transmitting/receiving antennae are placed on a belt, vest or attached to the patient by an adhesive sticker. The antenna(e) is connected to an RF transceiver. RF signals received in the capsule are used to sync the electronic circuits that are connected to at least one coil or other magnetic sensor in the capsule. In this way, feeble electromagnetic signals picked up by the magnetic sensor in the capsule can be detected with improved sensitivity since the exact timing of each such signal is known synced with the RF signal. This allows improved detection since noise picked up at times in which there is no RF transmission, hence no electromagnetic transmission can be ignored. 
         [0094]    In accordance with another embodiment of the disclosure, a process is used for compensation of movements between the coils and other magnetic sensors on the patient&#39;s belt or vest or stickers to minimize artifacts due to such movements. Referring to  FIGS. 2A-4B , a capsule  250 ,  350 ,  450  is sized and adapted to be swallowed by a patient for diagnostic or treatment purposes. The capsule may incorporate at least one coil and an electronic circuit that is in communication with the coil to pick up signals from the coil. On the patient, at least two coils are placed on a belt or vest or are attached to the patient by an adhesive sticker. The coils are positioned so that they are well attached to the patient and move with the patient, thus defining the coils the patient system of coordinates. 
         [0095]    During the process of signal acquisition, the coils on the patient transmit, each on its turn, an electromagnetic signal while the other coils are configured to pick up this signal. In the controller of the external unit on the patient, a table of signal values may be stored whereby for each coil emitting the electromagnetic signal, the values of the signals picked up by all other coils are stored. This process may be done in a cyclic fashion at short intervals for all coils. Transmissions from the capsule are done at time intervals when the coils on the patient body are not transmitting. These values are stored in a memory and used as a reference to ascertain whether movements between the coils have occurred. This process ensures that movements due to change in position between coils on the patient body are not mistaken as capsule movements since such movements will be detected separately from change in magnetic signals due to capsule movements. 
         [0096]    In another embodiment of the disclosure, a low pass filter or a Kalman filter is used to continuously update the change in signals in the table due to position change between the coils on the patient body. These values are stored in a memory and used as a reference to ascertain whether movements between the coils have occurred. This process ensures that movements due to change in position between coils on the patient body are not mistaken as capsule movements since such movements will be detected separately from change in magnetic signals due to capsule movements. 
         [0097]    According to various aspects, accelerometers and/or gyros are placed near the coil (or other electromagnetic sensor) on the patient body on a belt or a vest or by way of stickers. A control unit is connected to these accelerometers and/or gyros and is configured to calculate the relative movements of each coil (or other electromagnetic sensor) on the patient body. In case one or more than one of the coils (or other electromagnetic sensor) are moving relative to each other as detected by the accelerometers and or gyros attached to them, the controller will take that into account when sensing possible changes in the electromagnetic signal pickup from the sensors so that relative movements of the electromagnetic sensors between themselves are not mistaken for capsule movements. 
         [0098]    In another embodiment of this invention, ultrasonic transducers (such as piezoelectric transducers, magneto constrictive transducers or others) are placed near the coil (or other electromagnetic sensor) on stickers placed on the patient. A control unit is connected to these ultrasonic transducers and is configured to measure distance between the transducers based on time of flight of the acoustic signals, whereby these transducers serve both as transmitters and receivers of the acoustic signals. The controller then calculates the relative distance between the transducers and hence the relative movements of each coil (or other electromagnetic sensor) on the patient body. In case one or more than one of the coils (or other electromagnetic sensor) are moving relative to each other as detected by ultrasonic transducers attached to them, the controller will take that into account when sensing possible changes in the electromagnetic signal pickup from the sensors so that relative movements of the electromagnetic sensors between themselves are not mistaken for capsule movements. 
         [0099]    It will be apparent to those skilled in the art that various modifications and variations can be made in the medical devices and methods of the present invention without departing from the scope of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only.