Abstract:
An imaging capsule with a fail-safe radiation mechanism includes a first rotatable disk with a radiation source mounted thereon and having a collimator structure allowing emission of radiation from radiation source from a few locations on the first disk. A second rotatable disk surrounds the first disk, is rotatable relative to first disk, and includes areas that block radiation and areas that are transparent to emission of radiation. In a rest position, second disk is situated relative to first disk such that areas that block radiation are blocking the emission of radiation from the locations on the circumference of the disk that allow the emission of radiation. A motor is activated to rotate one of the disks and allow emission of radiation. A connector is configured to automatically return first disk and second disk to the rest position when the motor is deactivated.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/647,215, having a filing date of 15 May 2012, and U.S. Provisional Patent Application No. 61/647,234, having a filing date of 15 May 2012, both of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to limiting exposure of a patient to radiation and more specifically to a low-power-consumption, fail-safe radiation concealment mechanism in an imaging capsule that is swallowed by a patient to examine the patient&#39;s gastrointestinal tract. 
     BACKGROUND 
     One method for examining the gastrointestinal tract for the existence of polyps and other clinically relevant features that may indicate regarding the potential of cancer is performed by swallowing an imaging capsule that will travel through the tract and view the patient&#39;s situation. In a typical case the trip can take between 24-48 hours, after which the imaging capsule exits in the patient&#39;s feces. Typically the patient swallows a contrast agent to enhance the imaging ability of the imaging capsule. Then the patient swallows the imaging capsule to examine the gastrointestinal tract while flowing through the contrast agent. The imaging capsule typically includes a radiation source, for example including a radioisotope that emits X-rays or Gamma rays. The radiation is typically collimated to allow it to be controllably directed toward a specific area during the imaging process. In an exemplary case the imaging capsule is designed to measure Compton back-scattering and transmits the measurements (e.g. count rate) to an external analysis device, for example a computer or other dedicated instruments. 
     In a typical implementation a radio-opaque contrast agent is used so that a position with a polyp will have less contrast agent and will measure a larger back-scattering count. Alternatively, other methods may be used to image the gastrointestinal tract. 
     U.S. Pat. No. 7,787,926 to Kimchy the disclosure of which is incorporated herein by reference, describes details related to the manufacture and use of such an imaging capsule. 
     Use of an imaging capsule exposes the user to radiation, which may be potentially harmful. Accordingly, it is of interest to limit the user&#39;s exposure to radiation when not necessary, for example while the imaging capsule is located in positions that do not need to be measured. Typically, the imaging capsule may be designed with shutters that can be instructed to block the exit of radiation when not needed. However, there still exists the hazard that in case of malfunction of the imaging capsule, for example in case of a power failure, radiation may be emitted without constraint. 
     It is thus desirable to design a fail-safe radiation blocking mechanism that automatically blocks the emission of radiation and only allows radiation to be emitted if power is available and the device provides an instruction to allow radiation to be emitted. It may be further desirable to provide such a mechanism that can save power when opening and closing the shutters. 
     SUMMARY OF THE INVENTION 
     According to various aspects of the disclosure, an imaging capsule with a fail-safe radiation mechanism may include a first rotatable disk with the radiation source mounted thereon. The first disk has a collimator structure allowing the emission of radiation from the radiation source substantially only from a few locations on the circumference of the first disk. A second rotatable disk surrounds the circumference of the first rotatable disk and is configured to rotate relative to the first disk. The second disk includes areas that block radiation and areas that are transparent to the emission of radiation. In a rest position, the second disk is situated relative to the first disk such that the areas that block radiation are blocking the emission of radiation from the few locations on the circumference of the disk that allow the emission of radiation. A connector assembly couples the first disk to the second disk, and a motor rotates one of the rotatable disks relative to the other of the rotatable disks. The first disk and second disk are initially in the rest position blocking the emission of radiation until the motor is activated to rotate one of the rotatable disks and allow the emission of radiation. The connector is configured to automatically return the first disk and the second disk to the rest position when the motor is deactivated. 
     In some aspects, a method of providing fail-safe radiation while scanning inside a living body may include mounting a radiation source on a first rotatable disk, positioning collimators on the first rotatable disk so that the radiation is substantially allowed to be emitted only from a few locations on the circumference of the first rotatable disk, and placing a second rotatable disk to surround the circumference of the first rotatable disk and configured to rotate relative to the first rotatable disk, the second rotatable disk including areas that block radiation and areas that are transparent to the emission of radiation. The method further includes situating the second rotatable disk and the first rotatable disk initially in a rest position wherein the second rotatable disk is situated relative to the first rotatable disk such that the areas that block radiation are blocking the emission of radiation from the few locations on the circumference of the first rotatable disk that allow the emission of radiation, receiving instructions to begin emitting radiation, activating the motor to rotate the first rotatable disk relative to the second rotatable disk to a position that allows the emission of radiation, and coupling the first rotatable disk and the second rotatable disk so that they will return to the rest position automatically when the motor is deactivated. 
     This disclosure generally concerns the description of several possible fail-safe concealment mechanisms to limit the radiation exposure of patients to ionizing radiation such as x-rays, gamma rays, and beta emissions from a radio isotope that is used in an imaging capsule. The capsule is designed to be swallowed by the patient and travels through the Gastro Intestinal tract. An example of such a concealment mechanism is described in U.S. patent application Ser. No. 10/596,065, filed on the May 26, 2006, now U.S. Pat. No. 7,787,926, titled Intra Lumen Imaging Capsule, and PCT Publication No. WO 2012/035528, titled Fail-safe Radiation Concealment Mechanism, the disclosures of which are incorporated herein by reference. 
     The concealment mechanism is designed with shutters that are normally closed, effectively stopping the emitted radiation from the radiation source within the capsule to exit the capsule, thus reducing the exposure of the patient to ionizing radiation. 
     When the radiation is emitted and the collimator is moving and scanning, detectors (13) in FIGS. 1-4 detect X-ray Fluorescence and Compton scattering photons which are used for 3D imaging within the colon as described in U.S. patent application Ser. No. 10/596,065. 
     The described mechanisms open the shutters only when the capsule requires these photons (or beta electrons) for imaging the internal lumen of the gastro intestinal tract. 
     The requirement of fail-safe in the context of this invention means that the shutter mechanism cannot remain open and is dependent on electric power to be opened. Thus, if there is no battery power for whatever reason, the shutters close and exposure to the patient is effectively stopped. In addition, if for any reason there is a leak of the oil in the concealment mechanism, the shutter mechanism will remain closed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will be understood and better appreciated from the following detailed description taken in conjunction with the drawings. Identical structures, elements or parts, which appear in more than one figure, are generally labeled with the same or similar number in all the figures in which they appear, wherein: 
         FIG. 1A  is a schematic illustration of an exemplary screening system in accordance with various aspects of the disclosure; 
         FIG. 1B  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; 
         FIG. 2  is an illustration of an exemplary fail-safe imaging capsule according to various aspects of the disclosure; 
         FIG. 3  is an illustration of an exemplary fail-safe imaging capsule according to various aspects of the disclosure; 
         FIG. 4  is an illustration of an exemplary fail-safe imaging capsule according to various aspects of the disclosure; 
         FIG. 5  is an illustration of an exemplary fail-safe imaging capsule according to various aspects of the disclosure; 
         FIG. 6  is an illustration of an exemplary fail-safe imaging capsule according to various aspects of the disclosure; and 
         FIG. 7  is a cross-sectional view of an exemplary fail-safe concealment assembly of the fail-safe imaging capsule of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, corresponding or similar reference numbers will be used, when possible, throughout the drawings to refer to the same or corresponding parts. 
     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  ( FIG. 1B ) 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. 
     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 . 
     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 one or more radiation detectors  162  ( FIG. 2 ). 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. 
     Reference is now made to  FIG. 1B , 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 . 
     Reference is now made to  FIG. 2 , which is a schematic illustration of a perspective view of an exemplary failsafe imaging capsule  150 , according to various aspects of the disclosure. In an exemplary embodiment of the invention, imaging capsule  150  is designed to automatically block radiation from being emitted from it until receiving instructions to release radiation and image its surroundings. In an exemplary embodiment of the invention, power is required to prevent blocking emission of radiation. Optionally, if imaging capsule  150  lacks power the radiation will be blocked. 
     In an exemplary embodiment, imaging capsule  150  includes an encasement  160  for holding and protecting the elements of the device from acids and other liquids or gases along its path of motion. Optionally, the encasement  160  should be able to withstand external pressures for at least 50-100 hours to allow for imaging capsule  150  to traverse the gastrointestinal tract and exit while still intact. Inside encasement  160 , imaging capsule  150  includes a power source  162  (e.g. one or more batteries), a motor  164 , a radiation source  166 , one or more detectors  168 , and a transceiver  175 . In an exemplary embodiment of the invention, radiation source  166  is located on a first rotatable disk  180  and provides radiation that is blocked by a filling material  182  that forms a portion of the first disk  180 . For example, the filling materials may be made of lead or tungsten or other dense materials. Optionally, the radiation is only free to travel in a few specific directions through one or more collimators  184  formed in the first disk  180 . 
     In an exemplary embodiment, power source  162  provides power to motor  164 , and motor  164  is rigidly and operably coupled to a second rotatable disk  186 . The second rotatable disk  186  is rotatable relative to the first rotatable disk  180 . Both the first and second rotatable disks  180 ,  186  are rotatable about the same rotation axis  188 . One or more directed radiation beams may be emitted from collimators  184  controllably scanning the surroundings through the imaging capsule  150 . One or more detectors  168  can detect backscattered particles resulting from the directed radiation beam. In an exemplary embodiment, detector(s)  168  may count the detected particle and provides the information to transceiver  175  for transmission to an external data recording unit  152  (e.g., a computer or processor) for processing and optionally constructing a visual representation of the information. In some embodiments of the invention, transceiver  175  uses radio frequency (RF) transmissions to receive instructions from an external device (unit  152  or another) and to provide information to the external device (unit  152  or another). In some aspects, the external device may instruct imaging capsule  150  to start scanning, to stop scanning, to scan in a specific motion pattern, to scan at specific times, etc. 
     In an exemplary embodiment, a radiation concealment mechanism  200  may include the first rotatable disk  180  and the second rotatable disk  186  that share the same rotation axis  188 . The first rotatable disk  180  and is free to rotate relative to the second rotatable disk  186 . The second disk  186  includes shutters or blocking areas  190  coupled therewith, which are made up from a material that blocks radiation. In an initial rest position, second rotatable disk  186  is positioned so that shutters  190  coincide and align with the outlets of collimators  184 , so that the emission of radiation from the collimators  184  is blocked. 
     In an exemplary embodiment of the invention, the first rotatable disk  180  and the second rotatable disk  186  are connected together with a spring  192 , for example, in the shape of a spiral. Thus, if the second rotatable disk  186  is rotated, for example, clockwise, the spring will tighten and exert a force on the first rotatable disk  180 , so that the first rotatable disk  180  will aspire to follow suit and rotate clockwise also. 
     It should be appreciated that as the second rotatable disk  186  rotates relative to the first rotatable disk  180 , in some positions, shutters  190  stop blocking the outlets of collimators  184  and the radiation is freely emitted to scan the patient. In the rest position of radiation control mechanism  200 , spring  192  is unwound (i.e., unloaded) and the collimators  184  are blocked. After rotating the second rotatable disk  186  some amount relative to the first rotatable disk  180 , the spring  192  is in a tightened (i.e., loaded) configuration. Thus, any relative angular (rotational) movement between the first rotatable disk  180  and the second rotatable disk  186  is quickly corrected since this relative angular movement loads the spring  192  and the spring  192  in turn reacts to return the relative angular position back to the rest position. 
     To activate the concealment mechanism  200 , the electric motor  164  is energized. The motor  164  performs a swift movement of large angular rotation in one direction (e.g., clockwise) and stops. This swift turn of the motor  164  rotates the second rotatable disk  186  relative to the first rotatable disk  180  since the second rotatable disk  186  is fixedly coupled for rotation by the motor  164 . This relative rotation between the first rotatable disk  180  and the second rotatable disk  186  loads the spiral spring  192 . Since the shutters  190  are rigidly coupled with the second rotatable disk  186 , this swift angular turn exposes the collimators  184  of the first rotatable disk  180  and the radiation is freely emitted to scan the patient. 
     Once the motor  164  stops, the loaded spiral spring  192  urges the the first rotatable disk  180  to rotate relative to the second rotatable disk  186 . As the first rotatable disk  180  turns relative to the second rotatable disk  186 , the spring  192  is unloaded. At this time, the first rotatable disk  180  accelerates rotationally while the spiral spring  192  pulls the first rotatable disk  180  towards the equilibrium point relative to the second rotatable disk  186 . At the equilibrium point (i.e., rest position), the collimators  184  are aligned just behind the shutters  190  of the second rotatable disk  186 . All the time until collimators  184  are aligned behind the shutters  190  of the second rotatable disk  186 , the collimators are open and thus radiation, for example, x-rays, gamma rays, or the like are emitted. Once the collimators  184  are aligned behind the shutters  190  of the second rotatable disk  186 , the x-rays, gamma rays, or the like are blocked. 
     When the motor  164  stops and the loaded spring  192  urges the first rotatable disk  180  to rotate relative to the second rotatable disk  186 , the first rotatable disk  180  accelerates rotationally and acquires and angular (rotational) velocity and momentum. Thus, in the absence of a rotationally stopper, the first rotatable disk  180  rotates relative to the second rotatable disk  186  until it overshoots the equilibrium point, and the collimators  184  are covered and then again uncovered by the shutters  180  as they overshoot. This overshoot in turn again starts to load the spiral spring  192 , this time in an opposite angular direction compared with the initial loading of the spring  192 . Thus, the resistance of the spring  192  to the reloading thus slows down the rotation of the first rotatable disk  180  relative to the second rotatable disk  186  until the relative rotation stops and starts to return the first and second rotatable disks  180 ,  186  back to the equilibrium position where the collimators  184  are behind the shutters  180 . 
     It should be understood that this mechanical behavior can be described using the general equation of a driven spring and mass rotating harmonic mechanical oscillator. The first and second rotatable disks  180 ,  186  are attached to one another with a spring  192 . This mechanical structure can be viewed as a driven mechanical oscillator where the first rotatable disk  180  is free to move about its central axis  188  and is tied by a spring  192  with its mass M. The second rotatable disk  186  is rigidly connected to the electric motor  164 . 
     To activate the concealment mechanism, the electric motor  164  is energized. The motor  164  performs a swift movement of large angular rotation in one direction and stops. A first encoder ring  194  is connected to the first rotatable disk  180  and second encoder ring  196  is connected to the second rotatable disk  182 . A controller  198  is connected to a first encoding sensor  193 , which detects encoder ring  194 , and to a second encoding sensor  197 , which detects encoder ring  196 . The sensors  193 ,  197  count the number of sectors that the first rotatable disk  180  and the second rotatable disk  182  rotate. This enables the controller  198  to know when the collimators  184  get behind the shutters  190  of the second rotatable disk  182 . Thus, the controller  198  can selectively activate the electric motor  164  when it is desired to uncover the collimators  184  to radiate the patient. 
     The controller  198  can thus activate the electric motor  164  to short periods of time acting as a driver to the forced mechanical oscillator that is comprised of the first rotatable disk  180  and the second rotatable disk  182  attached with a spring  192 . Every short motor movement drives this mechanical system to oscillate. Thus applying electric motor  164  drive only at the correct timing in accordance with the relative position of the first and second encoder rings  194 ,  196 , the controller  198  activates the electric motor  164  to move in a back and forth rotational direction in sync with the natural harmonic frequency of the mechanical oscillating system using the information of the encoder sensors  193 ,  197  to coordinate the activation times of the motor  164 , as well as advancing the relative position of the shutters  190  so that over time there are no blind spots for the scanning. 
     Referring now to  FIG. 3 , according to various aspects, an exemplary imaging capsule  350  similar to the previously-described capsule  150  may include the electric motor  164  and the second rotatable disk  186 , which are rigidly connected together. The imaging capsule  350  includes a one directional bearing  399  operably coupled with a drive shaft  365  of the electric motor  164  to ensure that the second rotatable disk  186  does not turn backwards when the electric motor  164  is not powered. In this case, all motor movements are in the same rotational direction and not back and forth. The controller  198  activates the electric motor to move in one direction in sync with the natural harmonic frequency of the mechanical oscillating system. 
     Referring now to  FIG. 4 , in another embodiment of an exemplary imaging capsule  450  similar to capsule  150  described above, the spiral spring  192  of the embodiments of  FIGS. 2 and 3  is replaced by a pair of magnetic rings  491 ,  492 . The first magnetic ring  491  is fixedly coupled with the first rotatable disk  180 , and the second magnetic ring  492  is fixedly coupled with the second rotatable disk  186 . The magnets  491 ,  492  operate to “connect” the first rotatable disk  180  and the second rotatable disk  186  as did the spiral spring  192  in the previous embodiments. For example, the magnets  491 ,  492  exert a “reverse” rotational torque as similar poles are moved toward a position facing each other and exert a “forward” rotational torque as opposite poles are moved toward a position facing each other. 
     Referring now to  FIG. 5 , according to various aspects, an exemplary imaging capsule  550  similar to the previously-described capsule  450  may include the electric motor  164  and the second rotatable disk  186 , which are rigidly connected together. The imaging capsule  550  includes a one directional bearing  599  operably coupled with a drive shaft  365  of the electric motor  164  to ensure that the second rotatable disk  186  does not turn backwards when the electric motor  164  is not powered. In this case, all motor movements are in the same rotational direction and not back and forth. 
     According to an exemplary embodiment of this disclosure, the shutter mechanism depends on fluid dynamic friction force to open and closes when rotation stops. 
       FIGS. 6 and 7  illustrate an exemplary embodiment of a fail-safe mechanism that is based on the following principle of operation. An exemplary imaging capsule  650  is designed to automatically block radiation from being emitted from it until receiving instructions to release radiation and image its surroundings. In an exemplary embodiment of the invention, power is required to prevent blocking emission of radiation. Thus, if imaging capsule  650  lacks power the radiation will be blocked. 
     In an exemplary embodiment, imaging capsule  650  includes an encasement  660  for holding and protecting the elements of the device from acids and other liquids or gases along its path of motion. Inside encasement  660 , imaging capsule  650  includes a power source  662  (e.g. one or more batteries), a motor  664 , a radiation source  666 , one or more detectors  668 , and a transceiver  675 . In an exemplary embodiment of the invention, radiation source  666  is located on a first rotatable disk  680  and provides radiation that is blocked by a filling material  682  that forms a portion of the first disk  680 . For example, the filling materials may be made of lead or tungsten or other dense materials. Optionally, the radiation is only free to travel in a few specific directions through one or more collimators  684  formed in the first disk  680 . 
     In an exemplary embodiment, power source  662  provides power to motor  664 , and motor  664  is rigidly and operably coupled to the first rotatable disk  680 . A second rotatable disk  686  is mounted for rotation relative to the first rotatable disk  680 . Both the first and second rotatable disks  680 ,  686  are rotatable about the same rotation axis  688 . One or more directed radiation beams may be emitted from collimators  684  controllably scanning the surroundings through the imaging capsule  650 . One or more detectors  668  can detect backscattered particles resulting from the directed radiation beam. In an exemplary embodiment, detector(s)  668  may count the detected particle and provides the information to transceiver  675  for transmission to an external data recording unit  152  (e.g., a computer or processor) for processing and optionally constructing a visual representation of the information. In some embodiments, transceiver  675  uses radio frequency (RF) transmissions to receive instructions from an external device (unit  152  or another) and to provide information to the external device (unit  152  or another). In some aspects, the external device may instruct imaging capsule  650  to start scanning, to stop scanning, to scan in a specific motion pattern, to scan at specific times, etc. 
     Referring now to  FIG. 7 , in an exemplary embodiment, a radiation concealment mechanism  700  may include the first rotatable disk  680  and the second rotatable disk  686  that share the same rotation axis  688 . The first rotatable disk  680  may include a first limiter  681  fixed thereto, and the second rotatable disk  686  may include a second limiter  687  fixed thereto. The second rotatable disk  686  and is free to rotate relative to the first rotatable disk  680 . The second disk  686  includes shutters or blocking areas  690  coupled therewith, which are made up from a material that blocks radiation. The shutters  690  are movable in a chamber  689  containing a viscous liquid  691 . In an initial rest position, second rotatable disk  686  is positioned so that shutters  690  coincide and align with the outlets of collimators  684 , so that the emission of radiation from the collimators  684  is blocked. 
     In an exemplary embodiment of the invention, the first rotatable disk  680  and the second rotatable disk  686  are connected together with a spring  692 , for example, in the shape of a spiral. Thus, if the first rotatable disk  680  is rotated, for example, clockwise, the spring  692  will tighten (i.e., load) and exert a force on the second rotatable disk  686 , so that the second rotatable disk  686  will aspire to follow suit and rotate clockwise also. Although the second rotatable disk  686  wants to turn relative to the first rotatable disk  680  under the urging of the loaded spring  692 , the second rotatable disk  686  moves in the viscous liquid  691 , which in turn exerts torque on the second rotatable disk  686  and pivotable fins  685  to resist movement of the second rotatable disk  686  relative to the first rotatable disk  680 . 
     Rotation of the first rotatable disk  680  by the motor  664 , for example, in the clockwise direction as viewed in  FIG. 7 , changes the position of the first rotatable disk  680  relative to the second rotatable disk  686  until the first position limiter  681  reaches the second position limiter  687  at an open configuration. Once the first position limiter  681  reaches the second position limiter  687 , the first rotatable disk  680  and the second rotatable disk  686  turn together, whereby the spring  692  connecting between the first and second disks  680 ,  686  is loaded. At this position, the first rotatable disk  680  and the second rotatable disk  686  are aligned so that radiation from the radiation source  666  can escape through the collimators  684 , which are no longer blocked by the shutters  690 . This continues as long as the motor  664  rotates the first rotatable disk  680  at sufficient rotational velocity to keep the spring  692  loaded at the open configuration of the first and second limiters  681 ,  687 . 
     When the motor  664  stops turning the first rotatable disk  680 , the torque induced by the viscous liquid  691  is reduced. Thus, the loaded spring  692  exerts torque that exceeds any torque induced by the viscous liquid  691  and moves the second rotatable disk  686  until the second limiter  687  of the second rotatable disk  686  reaches the first limiter  681  at a closed configuration. At this closed configuration, the shutters  690  block radiation from escaping the collimators  684 . The spring  692  is preloaded so that it holds the first rotatable disk  680  and the second rotatable disk  686  in this closed configuration absent energization of the motor, preventing movements between the first rotatable disk  680  and the second rotatable disk  686 , and thus blocking radiation by the radiation source  666  from escaping via the collimators  684 . 
     It should be appreciated that the spring  692  can be replaced by other types of flexible material which will exert torque when displaced. In another embodiment, magnets can be placed instead of the spring  692  to exert torque if brought close together (similar poles facing each other) or exert torque pulling each other (opposite poles facing each other). 
     It should be understood by persons skilled in the art that the viscosity of the liquid or gel  691  may be chosen according to the required rotational velocity of the concealment mechanism  700 . If a fast rotational velocity is chosen, a low viscosity liquid will generate sufficient drag to load the spring  692  at high rotational velocity. If a slow rotational velocity is chosen for the concealment mechanism  700 , a high viscosity liquid or gel is required to generate sufficient drag to load spring  692  at low rotational speed. 
     The viscous liquid  691  can be Paraffin oil if low viscosity liquid is chosen or other bio compatible high viscosity liquid or gel such that if a leak occurs and liquid or gel is released out of the capsule into the gastro intestinal track, it will not cause any harm. In this scenario, if the liquid escapes the capsule, the concealment mechanism  700  will not function and will not open as it will not exert torque on the second rotatable disk  686  when turning. This constitutes a safety feature of this concealment mechanism keeping it closed and blocking radiation from escaping if the mechanical integrity of the concealment mechanism is compromised. 
     In another embodiment, the viscous liquid or gel  691  is contained in a sealed container that is positioned near the concealment mechanism  700 . On the concealment mechanism  700 , at least one magnet may be attached. Inside the sealed container with the viscous liquid or gel, at least one fin  685  made of magnetic material or ferromagnetic material is placed such that when the concealment mechanism  700  rotates, this fin  685  rotates with the concealment mechanism due to its attraction to the at least one magnet on the concealment mechanism. 
     In another embodiment of this invention, ferromagnetic or magnetic powder is placed in the sealed container with the viscous liquid or gel. This powder is attracted to the at least one magnet on the concealment mechanism and rotates when the concealment mechanism rotates. This powder acts in the same manner as the fin described above. 
     It should be appreciated that the radiation source  160  may be adapted to emit gamma rays, X-rays, and/or beta electrons (i.e., radiation having an energy of at least 10 keV). For some applications, the radiation source  166 ,  666  may comprise a radioisotope or a miniature radiation generator. In some aspects of the disclosure, radiation source  166 ,  666  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. It should be appreciated that the capsule  150 ,  350 ,  450 ,  550 ,  650  may include more than one radiation source  166 ,  666 . According to various aspects, the capsule  150 ,  350 ,  450 ,  550 ,  650  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. 
     The capsule  150 ,  350 ,  450 ,  550 ,  650  also typically comprises circuitry (not shown), which, for some applications, may include a pressure sensor. In an embodiment of the disclosure, the radiation source  166 ,  666  and detector(s)  168 ,  668  are arranged to “observe” the entire 4 pi squared sphere (or a portion of it) surrounding the capsule. 
     From the foregoing, it will be appreciated that, although specific embodiments have been described herein for purposes of illustration, various modifications or variations may be made without deviating from the spirit or scope of inventive features claimed herein. Other embodiments will be apparent to those skilled in the art from consideration of the specification and figures and practice of the arrangements disclosed herein. It is intended that the specification and disclosed examples be considered as exemplary only, with a true inventive scope and spirit being indicated by the following claims and their equivalents.