WO2010006608A1

WO2010006608A1 - Tracking areas or volumes of dynamic objects

Info

Publication number: WO2010006608A1
Application number: PCT/DK2009/000172
Authority: WO
Inventors: Hans Jørgen PEDERSEN
Original assignee: Danfoss A/S; Briest, Arne
Priority date: 2008-07-18
Filing date: 2009-07-14
Publication date: 2010-01-21

Abstract

A system is described to track changes of the volumes or cross-sectional areas of objects, preferably hollow objects, by tracking the positions of magnetic field generating elements. The system is particularly for in-vivo systems where the objects would be hollow organs, such as the bladder and the stomach.

Description

TRACKING AREAS OR VOLUMES OF DYNAMIC OBJECTS

BACKGROUND

For many people it would be an advantage to be able to track how objects expands or contracts, either in their volumes or just in their cross-sectional areas.

One example is for people having urinary incontinence which is the accidental leakage of urine. At different ages, males and females have different risks of developing it.

For the male urinary system to do its job, muscles and nerves must work together to hold urine in the bladder and then release it at the right time. The urinary bladder is a temporary storage reservoir for urine. It comprises an opening into the urethra, being the final passageway for the flow of urine to the outside. A band of the detrusor muscle encircles this opening to form the internal urethral sphincter. Another sphincter, the external urethral sphincter, is a skeletal (voluntary) muscle and encircles the urethra where it goes through the pelvic floor. These two sphincters control the flow of urine through the urethra. When these sphincters fail to work properly, it may lead to urinary incontinence.

One possible treatment is to introduce an artificial sphincter, an implanted device that keeps the urethra closed until you are ready to urinate.

The device often has three parts: a cuff that fits around the urethra, a small balloon reservoir placed in the abdomen, and a pump placed in the scrotum. The cuff is filled with liquid that makes it fit tightly around the urethra to prevent urine from leaking. When it is time to urinate, you squeeze the pump with your fingers to deflate the cuff so that the liquid moves to the balloon reservoir and urine can flow through the urethra. When your bladder is empty, the cuff automatically refills in the next minutes to keep the urethra tightly closed.

One example of an artificial sphincter including a sensor is to be found in US2006142636, describing systems and methods for supplementing control of an anatomical sphincter. A collar containing variable viscosity fluid surrounds a portion of an anatomical conduit. The flow of bodily fluids through the anatomical conduit occurs according to the viscosity level of the variable viscosity fluid. Electro-rheologic fluid in the collar liquefies in the absence of an electrical potential difference to render the collar pliable, permitting the anatomical conduit to expand and fluid to flow through the anatomical conduit. Electro-rheologic fluid in the collar solidifies in the presence of an electrical potential difference to render the collar firm, restricting the anatomical conduit from expanding and restricting fluid from passing through the anatomical conduit. A control unit, or battery, operable in response to sensed pressure data or according to an external control unit manipulated by a patient, determines when an electrical potential difference is generated to change the state of the electro-rheologic fluid in the collar. Magneto-rheologic fluids can instead be used in the collar. An implanted or external control unit, or other magnetic source, determines when a magnetic field is generated to change the state of the magneto-rheologic fluid in the collar based on sensed pressure data or according to an external control unit operated by the patient.

In the various embodiments of the systems and methods of the artificial sphincter system according to the invention, a pressure sensor is provided in the anatomical conduit or organ to be emptied through the anatomical conduit upstream of the collar. The sensor can be a wireless sensor that communicates with the implanted control unit, battery, or magnetic field generator as the case may be, or the sensor can be a wired sensor physically connected to the implanted control unit, battery, or magnetic field generator. Regulation of the collar and the state of the variable viscosity fluid contained therein by the generation of the electric or magnetic field, is thus determined by data sensed by the pressure sensor or by operation of the external control unit by the patient.

Many people in the world suffer from obesity of a number of reasons. It is a condition known to give a lot of health problems. One way to help is by restrictive operations to make the stomach smaller. With a smaller stomach the feeling of being full comes a lot quicker. The most common restrictive surgery is adjustable gastric banding. One typical way this works, is to create a small pouch at the top of the stomach. This pouch is not completely closed off from the rest of the stomach. A small opening allows the partially digested food to move into the rest of the stomach and then into the intestines.

It often require several visits to the doctor for adjusting the band before the patient feels that optimal restriction has been achieved, neither so loose that hunger is not controlled, nor so tight that food cannot be consumed.

Examples of such gastric banding are found in e.g. WO 2008/005387 and WO 2007/140430. In WO 2008/005387 a magnetic device is described for the treatment of obesity, and specifically, for restricting the medically effective volume of a stomach. In one embodiment, the magnetic device comprises a magnetic bar for placement around the gastric wall and biased to create two stomach portions. The first portion of the stomach is for the primary digestion of ingested food, while the second portion of the stomach is bypassed in the digestive process. In an additional embodiment a device is provided for restricting the capacity of a stomach and forming a gastric evacuation channel. The device comprises a magnetic body positioned on the external wall of a stomach from the superior surface of the stomach to the inferior surface of the stomach. The device may further comprise a subcutaneous balloon port for regulating the volume of a balloon pouch situated adjacent to the external wall of the stomach, and a plurality of adhesive bands for enhancing the stabilization of the device. In another embodiment, a system is provided for automatically reducing the capacity of a stomach upon the ingestion of food. The system comprises a device for restricting the capacity of the stomach, a sensor for sensing the ingestion of food, and a power supply. The sensor is capable of electronically communicating with the device, such that the device may shift between an open position wherein the stomach is not constricted and a closed position wherein the stomach is compressed into two sections. In yet another embodiment, a method is provided for placing the magnetic bar around the gastric wall to result in a decreased medically effective volume of a stomach.

FIGS. IA and IB show two views of an embodiment of a gastric remodeling device. In this embodiment, the gastric remodeling device 10 avoids the nutritional deficiencies observed with Malabsorptive Procedures, does not require sutures or staples that could lead to dehiscence (e.g., the opening of the suture site) or fistula (e.g., an abnormal connection between organs or intestines), and produces a significant amount of regurgitation and vomiting. In the embodiment shown in FIGS. IA and IB, the gastric remodeling device 10 is comprised of a first magnetic bar 12 and a second magnetic bar 14. Each of the magnetic bars 12, 14 comprises a proximate end 18 and a distal end 20. The first and second magnetic bars 12, 14 may be comprised of any permanent magnet material known in the art and may be flexible, semi-flexible, or articulated. In one embodiment, the first and second magnetic bars 12, 14 each comprise a thin, smooth, ferromagnetic bar. The first and second magnetic bars 12, 14 may be configured in any shape so long as both of the first and second magnetic bars 12, 14 easily conform to the side of a stomach. In one embodiment, both the first magnetic bar 12 and the second magnetic bar 14 each comprise an identical sigmoid-like shape and are disposed in a mating, mirror image relationship to each other. The first magnetic bar 12 and the second magnetic bar 14 are polarized such that the first magnetic bar 12 and the second magnetic bar 14 are biased towards each other. Due to the matching configuration and the bias between the first magnetic bar 12 and the second magnetic bar 14, the first and second magnetic bars 12, 14 are capable of magnetically engaging. When the first and second magnetic bars 12, 14 magnetically engage, the two magnetic bars 12, 14 form a single unit that is magnetically secured to any tissue compressed therebetween. The proximate end 18 of the first magnetic bar 12 magnetically and mechanically engages with the proximate end 18 of the second magnetic bar 14, such that the two magnetic bars 12, 14 are hingedly coupled and define an apex 16, an angle theta, and an interior space. The interior space comprises a width A. Merely by way of example, and without any intended limitation, when the first and second magnetic bars 12, 14 are magnetically coupled at their proximate ends 18, the gastric remodeling device 10 is configured as a V-shape.

In the document WO 2008/005387 an access port locator system for adjustable gastric bands is described. The system includes an access port with an RFID tag with its antenna adjacent to the receiving portion of the port. The system includes a locator with radio frequency transmitter/receiver circuitry for sending read or interrogation signals to the RFID tag and for sending write signals to the tag to write treatment data to memory of the RFID tag. The locator also includes an antenna array with four patch antenna arranged in pairs to model two monopulse radar antenna systems. The locator also includes processor(s) and logic modules/circuitry for processing the tag response signals received by the antenna array to determine location information for the RFID tag and associated port, i.e., to identify the center of the port relative to the antennae array or array face such as with strength and direction information relative to the array face.

These are in-vivo examples where a tracking of a volume or a cross-sectional area could increase the comfort of a patient. Tracking the volume of the bladder for persons with urinary incontinence, would give an indication of when the bladder is close to be filled and should be emptied, and people having a gastric band could be helped in the fitting of the band by tracking the actual cross- sectional area, or diameter, of the band, just at the band during daily life could be regulated, perhaps by decreasing periodic discomforts by relaxing the band. Another possibility would be to track the volume of the gastric pouch rather than the cross-sectional area of the gastric band. As it says in the document US 2006/0252982, then an initial maladjustment or a change in the stomach over time may lead to a stoma of an inappropriate size, warranting an adjustment of the gastric band. Otherwise, the patient may suffer vomiting attacks and discomfort when the stoma is too small to reasonably pass food. At the other extreme, the stoma may be too large and thus fail to slow food moving from the upper portion of the stomach, defeating the purpose altogether for the gastric band.

The document US 2006/0252982 therefore describes an implantable artificial sphincter system providing long-term adjustment via transcutaneous energy transfer (TET), minimizing invasive adjustment through adding or removing fluid via a syringe. An infuser device provides bi-directional fluid transfer via a flexible conduit to a sphincter band, such as a gastric band. Materials are nonferrous and nonmagnetic so as to be magnetic resonance imaging (MRI) safe, being substantially immune to strong magnetic fields and not introducing an electromagnetic interference/compatibility (EMIC) hazard.

An additional gastric method of the gastric banding is to establish a gastric bypass from the small stomach pouch formed by the band to the gastrointestinal-tract. However, this might lead to a lack of vital vitamins. Again, using a measurement of the volume of the small stomach pouch formed by the band, would give the possibility to 'shut off' the bypass. Further, it is common for example to use scanning techniques to measure the present width of the band by tracking radiating substances introduced in the body, or to use MIR scanning having a band of a contrast material. Neither of these common techniques is suitable for continuous measurements, they are costly, and may require that radiating substances are introduced to the body.

The present invention introduces a method for continuous tracking of volumes or areas, by tracking the positions of magnetic field generating devices, where there is no need for introducing substances, such as radiating substances, into the body. This both makes the measuring cheaper and easier, and increases the general comfort of a patient.

It is known in the prior art to track the position of a device by measuring the magnetic field from a magnetic unit connected in or to the device. One example is to be found in WO/2007/074445, "SYSTEM AND METHOD OF IN-VIVO MAGNETIC POSITION DETERMINATION", describing systems and methods for position detection of a in-vivo sensing device. A magnetic field generator generates magnetic fields which are measured by an antenna. The position of the in-vivo sensing device is determined from the magnetic field intensity values. With reference to Figure 1 it is described that the system may include a device 40 having a sensor, e.g., an imager 46, one or more illumination sources 42, a power source 45, a magnetic unit 44 and a transmitter/receiver 41. In some embodiments, device 40 may be implemented using a swallowable capsule, but other sorts of devices or suitable implementations may be used. Outside a patient's body may be, for example, an external receiver/recorder 12 (including, or operatively associated with, for example, one or more antennas, or an antenna array), a storage unit 19, a processor 14, and a monitor 18. In some embodiments, for example, processor 14, storage unit 19 and/or monitor 18 may be implemented as a workstation, e.g., a computer or a computing platform. Further, the device 40 may include magnetic unit 44 which may include a magnetic field generator, for example, a conductive coil 49, a plurality of conductive coils 49, a permanent magnet, a plurality of permanent magnets, or any other magnetic field generator. The magnetic field unit may include a conductive coil, a current source or a power source that may be operativeiy connected to the conductive coil and a control unit which may be a switch or a controller to control the magnetic field generator. The power source may be included in magnetic unit 44, power source 45 or an external power source. In some embodiments magnetic unit 44 may include three mutually perpendicular coils, each may generate a magnetic field at a different time while receiver 12 may include at least three receiving antennas, for example, three mutually perpendicular coils. Based on the difference in the power received in each receiving antenna the position of the transmitting antennas may be determined. In some embodiments one coil may be included in magnetic unit 44 and three or more receiving antennas may be located outside the body in order to acquire a three-dimensional position. In some embodiments coils located outside the body may be used as the generating magnetic field antennas while coils located in magnetic unit 44 may be used as the receiving antennas. The magnetic unit may be used as a voltage source for other units or elements in device 40, for example, a conductive coil and a voltage source may be used as power source for illumination source 42, optical system 50 or any other unit or electrical circuit in device 40. During the operation of magnetic unit 44 an AC current flows through the conductive coil. The AC current may be low frequency, for example in a range of 0.5-5 Miz. The AC current may generate a magnetic field which may be used for determining the position of device 40. Other frequencies may be used. In some embodiments, voltage or current may be applied to one or more coils, for example, selectively, at pre-defined time intervals, substantially continuously, at one or more pre-defined time(s), on demand, in response to a remote instruction, in response to an external instruction, or the like. In some embodiments, voltage or current may be applied to one or more coils to generate magnetic fields simultaneously but with different frequencies. The predefined times may be, for example, after each transmitted video frame.

None of these cited systems possesses the ability to survey the expanding or decreasing surfaces of objects, and especially in the case of in-vivo implants, they lack the ability to calibrate the system without having to do surgery.

One document, US 2007/167758, discloses techniques for automatically detecting cardiac motion using contrast markers. The contrast markers can be located in images generated by an external imaging device, and may be such as to emit, or magnetic fields. The contrast markers can be used for locating regions of interest in a heart and their relative motion. The contrast markers, however, are elements being attached in the body as individual elements, making them more combersom to fix to an object. Further, the document the document does not disclose using the markers directly to measure a changing cross-area or volume.

The object of this invention is predominantly to overcome these lacks.

SUMMARY

Therefore the object of this invention is mainly to introduce a syste for tracking expansions and contractions of volumes, or just their changing surfaces. Therefore a systm is invented a magnetic field generating element, at least one receiving antenna for measuring magnetic field intensity values of magnetic fields, and a processor for determining the position of the object from the magnetic field.

In a preferred embodiment of invention, the magnetic field generating element is positioned in connection with or close to an object and the position of the magnetic field generating element is used to determine movements of the body or the surface of the object.

In another preferred embodiment the system further comprises a reference magnetic field generating element being fixedly positioned.

In another preferred embodiment more than one independently trackable magnetic field generating elements are positioned in connection with or close to an object.

In another preferred embodiment at least one magnetic field generating element is positioned in connection with or close to the external surface of the object.

In another preferred embodiment the magnetic field generating element is in- vivo, or invasively, positioned in a human body.

In another preferred embodiment the magnetic field generating element is externally positioned in contact with a human body.

In another preferred embodiment the object comprises a cavity and walls enclosing the cavity, wherein the movement being tracked is the movement of at least part of the walls enclosing the cavity.

In another preferred embodiment the magnetic field generating element is positioned in connection with or close to at least a part of the walls enclosing the cavity.

In another preferred embodiment a plural of magnetic field generating elements surround the object at least partly. In another preferred embodiment the plural of magnetic field generating elements are used to measure a change in cross-sectional area or volume of at least a part of the object.

In another preferred embodiment the plural of magnetic field generating elements are attached to a shaped elastic or stretchable material and where the shaped elastic or stretchable material surrounds at least a part of the object.

In another preferred embodiment the shaped stretchable material is shaped as a balloon, a pouch, a sheet of any shape, a belt, a band or any combination of these.

In another preferred embodiment each magnetic field generating element creates a magnetic field for not overlapping periods of time, or pulses, and/or has individual frequencies.

In another preferred embodiment each magnetic field generating element is equipped with a tag, such as a RFID tag, making them separately trackable.

In another preferred embodiment the object is an organ in a human body, such as the bladder, the stomach, the gastrointestinal-tract, the lungs or the heart.

In another preferred embodiment the magnetic field generating elements are attached to a stent, thus being positioned internally in the cavity of the body.

In another preferred embodiment the measured positions are used as data to be stored and/or processed, to give a signal such as an alarm, to activate or deactivate an actuator or a valve, or to compress or relax an in-vivo or ex-vivo compression or expansion system.

The invention further concerns a method for determining the changing volume or cross-sectional area of an object comprising the steps of: providing at least one antenna (3); a plural of magnetic fields generating elements connected in or to the surface of the object, detecting the magnetic fields generated by the magnetic field generating elements by the antenna(s) and measuring magnetic field values of the detected magnetic fields; and determining the position of the magnetic field generating elements from the measured magnetic field intensity values, and thereby estimating the changes in volume or cross-sectional area.

In one preferred embodiment the magnetic field generating elements are introduced with a cannula or endoscope.

FIGURES

Fig. A shows the basic principle of the invention, where an imlanted magnetic field generating element is tracked with antennas.

Fig. 1B illustrates the vectorial magnetic field of an element.

Fig. 2 shows a second aspect of the invention, where one magnetic field generating element is at a fixed position.

Fig. 3shows the an imbodiment of the invention used to track the bladder.

Fig. 4 shows a plural of magnetic field generating elements positiond for tracking of a cross sectional area.

Fig. 5 shows a plural of magnetic field generating elements positioned at an elastic circular band.

Fig. 6 shows a plural of magnetic field generating elements positioned at an elastic sheet.

Fig. 7A shows a plural of magnetic field generating elements positioned at a band formed sheet.

Fig. 7B shows the sheetformed band wrapped around an object.

Fig. 8 shows a plural of magnetic field generating elements positioned at a poch formed elastic material.

Fig. 9 shows a plural of magnetic field generating elements positioned at a ballon formed elastic material. Fig. 10 shows the pouch formed elastic element positioned at an object.

Fig. 11 shows the system of the invention used in gastric banding.

Fig. 12 shows the system of the invention used in gastric banding with bypass.

DETAILED DESCRIPTION

Fig. 1 A shows a simple illustration of the basic technology forming the present invention, where as in e.g. WO/2007/074445 a magnetic field generating element (2) is positioned inside a human or animal body (1), in the following non-limiting referred to as the human body (1). The magnetic field generating element (2) generates a magnetic field (4) either continuously or in pulses and is therefore trackable, or traceable. Preferably externally to the human body (1) is at least one receiving antenna (3), to detect the magnetic field, where the receiving antenna (3) would be connected to the necessary equipment for generating the received signal into data such as the intensity and/or the direction of the magnetic field, or said alternatively, either by measuring the intensity, the direction or by measuring the vectorial magnetic field. Knowing the magnetic strength and/or direction of the magnetic field generating element (2), the measured intensity can then be used to determine the distance from the magnetic field generating element (2) to the receiving antenna (3) and thereby the depth into the human body (1). Having three mutually orthogonal receiving antennas (3), it would then be possible to determine the position of the magnetic field generating element (2) within the human body (1).

The magnetic field generating element (2) itself may be a permanent magnetic object, such as, but not limited to, a ferromagnetic element, or it could be an electro magnet either getting energy from batteries or other energy storing devices, or could get energy from the externals as it is known in the art, such as receiving electro-magnetic energy in pulses.

Fig. 1B illustrates such a magnetic field generating element (2) having a magnetic field in the direction from left to right. Fig. 2 shows a first preferred embodiment of the present invention, where a reference magnetic field generating element (5), also being magnetic field generating, is fixedly positioned at or in the human body (1), where the reference magnetic field generating element (5) advantageously, but not necessarily, is identical to the magnetic field generating element (2). This gives the possibility to calibrate the system since the reference magnetic field generating element (5) has a known magnetic field (direction and intensity / magnitude) and position. Thereby there would be no need for anatomical landmarks and it would be easy to ensure long term stability and to recalibrate the system. One natural choice for positioning the reference magnetic field generating element (5) would be the pubis bone, but other positions either externally or internally to the human body (1) would also be possible.

In a preferred embodiment of the invention the system is used to survey the movement of the surface of an object, where the object could be solid or hollow, and could be an internal organ of an animal or human or an external body part.

When used invasively, or in-vivo, the magnet field generating elements (2) should be bio-compatible, either in that the materials themselves are biocompatible, by coating them, or perhaps covering them by a foil. Any biocompatible material or any manner known in the art to make elements bio- compatible would apply to the invention.

They could advantageously be implanted with an implanter in any manner known in the art to introduce e.g. a chip or tag into the body just beneath the skin of a pet animal. One common way is to introduce the chip with a syringe type implanter where a pushing device inside the cannula pushes the chip out of the cannula when at the correct position within the body.

The magnetic field generating elements (2) would advantageously be equipped with fixation elements like for example small hooks for securing them at the desired position within the body.

In this preferred embodiment of the invention, one example of the surveillance of an internal organ to the human body is to position the magnetic field generating element (2) in connection to the bladder as seen in Fig. 3, showing the magnetic field generating element (2) being attached to the external surface of the bladder (6).

Using together with an artificial sphincter to attach a magnetic field generating element (2) in connection with the walls of the bladder (6) makes it possible to track the filling of the bladder making it possible to identify when to urinate by giving some kind of signal or alarm.

In another preferred embodiment more than one movable and trackable magnetic field generating element (2) exists in the system. The separate magnetic field generating objects (2) then advantageously would create magnetic fields in pulses not overlapping in time, in order to make them individually trackable, and they could in another preferred embodiment additionally be equipped with tags like RFID tags to give each magnetic field generating element (2) a unique identification. Any other traceable identification method would also apply to the invention, such as letting each trackable magnetic field generating element (2) operate at its own individual frequency.

In the embodiment where the bladder is surveyed, one or more magnetic field generating elements (2) could be attached to a stent being introduced for example in the opening of the bladder, or into some other vessels or hollows.

Having a plural of magnetic field generating elements (2) makes it possible to track changes in e.g. cross-sectional areas and volumes. This is illustrated in Fig. 4 showing three magnetic field generating elements (2a, 2b, 2c) positioned around a tube shaped object (7) having a first diameter (8a), and thereby a first cross-sectional area. When the tube shaped object (7) changes to a second diameter (8b), and thereby a second cross-sectional area, the magnetic field generating elements (2a, 2b, 2c) move to different positions. Measuring the new positions would give at least an indication of the second diameter (8b), and thereby the second cross-sectional area. Knowing the exact shape of the cross section of the object (7) and/or increasing the number of magnetic field generating elements (2) would then increase the precision of the estimation of the second cross-sectional area.

In the same manner a 3-D picture could be obtained by distributing the magnetic field generating elements (2) around the (external or internal) surface of a (preferable hollow) body. In this manner a volume or a change in volume may be measured and estimated.

The tube shaped object (7) could for example be a stent inserted into an artery or vein.

In a preferred embodiment of the present invention when comprising a plural of magnetic field generating elements (2), they are attached to a stretchable and preferably elastic material, where the material in a non-limiting manner could be a polymer or more specifically an elastomere. The stretchable material could be shaped as the (internal or external) surface of the object to be surveyed, and could be formed as a band, a pouch or a balloon.

Fig. 5 shows a preferred embodiment where four magnetic field generating elements (2) are attached around a band (10) of an elastic or at least stretchable material.

Fig. 6 shows another preferred embodiment where the magnetic field generating elements (2) are attached to a sheet of any shape (11) of an elastic/stretchable material. The sheet (11) would then be wrapped around an object to be surveyed. Often the object would have openings or parts extruding that should not be covered by the sheet (11), so the sheet (11) could have any shape other than rectangular, any kind of cut-outs (12) and holes or include 3-D structures. The sheet could advantageously be equipped with any known kind of connection means such as Velcro.

Fig. 7A shows a version where the sheet (11) is formed like a belt (13), and Fig. 7B shows this belt (13) wrapped around the object (14). The belt could be equipped with connection means (like Velcro) at the ends (15a, 15b) to secure the two ends to each other, thereby securing the belt (13) to the object (14). Fig. 8 shows a preferred embodiment where a plural of magnetic field generating elements (2) are distributed around a pouch (16) of an elastic or at least stretchable material.

Fig. 9 shows a preferred embodiment where a plural of magnetic field generating elements (2) are distributed around a balloon (17) of an elastic or at least stretchable material.

In this manner, such a system comprising an elastic material and magnetic field generating elements (2) would be positioned preferably around the surface of the object to be surveyed, and would then follow the moving and changing surface of the object, as illustrated in Fig. 10, where a pouch shaped elastic (or at least stretchable) material (16) comprising the magnetic field generating elements (2) is positioned around the object (14) partly or totally comprising it (where the object (14) for example could be the bladder (6) of a human being). When the volume and thereby the surface of the object (14) changes, the elastic material (16) would change accordingly, and thereby the magnetic field generating elements (2) would change positions accordingly.

When used especially in-vivo, the elastic material would have to be biocompatible at least at the surface.

The system of the invention can advantageously be used in bariatric procedures, where Fig. 11 shows one preferred embodiment of the present invention, where gastric band (20) is wrapped around an upper part of the stomach establishing an upper stomach pouch (21), but is not wrapped more tightly than to leave an access to the remaining stomach part (22). Food first arrives to the upper stomach pouch (21) at a first rate, and the upper stomach pouch (21) fills to give the person the sensation to be full at a much earlier state than it would without the gastric band system. At a significantly slower rate the food enters the remaining stomach part (22) from the upper stomach pouch (21) to continue to the rest of the digestive system.

The gastric band (20) comprises the magnetic field generating element (2) positioned around the band, whereby it becomes possible to measure the dimensions of the gastric band (20), to give an indication of the actual state of the band and thereby the opening from the upper stomach part (21) to the remaining stomach part (22).

Optionally the gastric band system is equipped with a system (23) for adjusting the gastric band (20) where the system (23) would comprise means for receiving information and commands from the externals, possibly in response to the measured cross-sectional area of the gastric band (20). Such a system could be any system known from the art, where one example is as it is described in US 2006/0252982.

Fig. 12 shows an addition to the gastric banding method where a bypass line (24) is inserted from the upper stomach pouch (21) to the gastrointestinal-tract (25), thereby partly or totally bypassing the remaining stomach part (22) lowering the amount of nutrition extracted from the food. This, however, may lead to a lack of vital vitamins. Therefore a valve system may be introduced comprising a controllable valve (26) and a control system (27) comprising means to receive instructions from the external and means to regulate the controllable valve (26). The controllable valve (26) and control system (27) could be of any kind known in the art. This gives the option to partly or totally shut off the bypass line (24) from time to time to ensure that the body gets a chance to acquire the needed vitamins.

In another embodiment of the invention, the system, such as the illustrated embodiments, is equipped with an inclination sensor. Such a sensor would then measure the inclination of e.g. a patient, since it influences the system whether the patient is lying, standing or sitting. The measured inclination could then be included as additional input data for regulations of for example the bladder or sphincter control.

An ex-vivo example where the system could be applied, is to survey babies, sick or just weakened people, since a band or belt comprising magnetic field generating elements (2) could be wrapped around their chest to survey whether they are breathing, and an inclination sensor added to the system could detect if a baby supposed to be sleeping is standing or crawling in the bed, giving off a signal.

It should be understood that, though the illustrated embodiments are for in-vivo systems, any system, in-vivo or ex-vivo, within the field of healthcare, industrial or other, would also apply to the invention.

Claims

1. A system for tracking the movement of an object, the system comprising at least two magnetic field generating elements (2), at least one receiving antenna (3) for measuring magnetic field intensity values of magnetic fields, and a processor for determining the position of the object from the magnetic field, wherein the at least two magnetic field generating elements (2) are attached to a shaped elastic or stretchable material (11 , 13, 10, 16, 17) and where the shaped elastic or stretchable material (11 , 13, 10, 16, 17) surrounds at least a part of the object.

2. A system as in claim 1 , wherein at least onemagnetic field generating element (2) is positioned in connection with or close to an object and the position of the magnetic field generating element (2) is used to determine movements of the body or the surface of the object.

3. A system as in claim 2, wherein the system further comprises a reference magnetic field generating element (5) being fixedly positioned.

4. A system as in claim 3, wherein at least one magnetic field generating element (2) is positioned in connection with or close to the external surface of the object.

5. A system as in any of the preceding claims, where the magnetic field generating elements (2) is in-vivo, or invasively, positioned in a human body.

6. A system as in any of the claims 1 to 4, wherein the magnetic field generating elements (2) is externally positioned in contact with a human body.

7. A system as in any of the preceding claims, where the object comprises a cavity and walls enclosing the cavity, wherein the movement being tracked is the movement of at least part of the walls enclosing the cavity.

8. A system as in claim 7, wherein the magnetic field generating element (2) is positioned in connection with or close to at least a part of the walls enclosing the cavity.

9. A system as in claim 8, wherein a plural of magnetic field generating elements (2) surround the object at least partly.

10. A system as in claim 9, wherein the plural of magnetic field generating elements (2) are used to measure a change in cross-sectional area or volume of at least a part of the object.

11. A system as in claim 1 wherein the shaped stretchable material (11 , 13, 10, 16, 17) is shaped as a balloon, a pouch, a sheet of any shape, a belt, a band or any combination of these.

12. A system as in claim 11 , wherein each magnetic field generating element (2) creates a magnetic field for not overlapping periods of time, or pulses, and/or has individual frequencies.

13. A system as in any of the preceding claims, where each magnetic field generating element (2) is equipped with a tag, such as a RFID tag, making them separately trackable.

14. A system as in any of the preceding claims, wherein the object is an organ in a human body, such as the bladder, the stomach, the gastrointestinal-tract, the lungs or the heart.

15. A system as in any of the preceding claims, wherein the magnetic field generating elements (2) are attached to a stent, thus being positioned internally in the cavity of the body.

16. A system as in any of the preceding claims, wherein the measured positions are used as data to be stored and/or processed, to give a signal such as an alarm, to activate or de-activate an actuator or a valve, or to compress or relax an in-vivo or ex-vivo compression or expansion system.

17, A method for determining the changing volume or cross-sectional area of an object comprising the steps of: providing at least one antenna (3); a plural of magnetic fields generating elements (2) connected in or to the surface of the object, detecting the magnetic fields generated by the magnetic field generating elements (2) by the antenna(s) (3) and measuring magnetic field values of the detected magnetic fields; and determining the position of the magnetic field generating elements (2) from the measured magnetic field intensity values, and thereby estimating the changes in volume or cross-sectional area.

18. A system or method according to any of the preceding claims, wherein the magnetic field generating elements (2) are introduced with a cannula or endoscope.