WO2006087289A2

WO2006087289A2 - Method for driving a capsule inside a patient with the aid of an electric coil system

Info

Publication number: WO2006087289A2
Application number: PCT/EP2006/050788
Authority: WO
Inventors: Johannes Reinschke
Original assignee: Siemens Aktiengesellschaft
Priority date: 2005-02-18
Filing date: 2006-02-09
Publication date: 2006-08-24
Also published as: DE102005007631A1

Description

A method for driving a capsule within a patient by means of an electric coil system

The invention relates to a method for driving a permanent magnet containing capsule within a patient, in particular the gastrointestinal tract, with the aid of the patient's body at least partially to comprehensive ^¬ coil system.

For examining or treating a human or animal as a patient, minimally or non-invasive medical techniques are being used or developed more and more frequently. For some time, the use of endoscopes, which are introduced through body openings or small incisions in the patient. At the top of a more or less long flexible body there are inspection or manipulation devices, z. As a camera or a gripper, to perform a desired activity. Due to frictional effects and the limited length and bendability of endoscopes, these are of limited use. So can be z. B. the human small intestine with a total ^¬ length of about 5 m and a variety of entanglements difficult to reach endoscopically in its entirety.

From DE 101 42 253 a device or a method is known for endoscopy, which works wirelessly. A so-called "endorobot" in the form of a capsule of about 2 cm in length and about 1 cm in diameter containing an inspection, di ^¬ agnose- or therapy device. This may, for. Example, a video camera, a biopsy forceps, a clip or a drug be ^¬ reservoir. the capsule contains a magnetizable or permanently magnetic element. in the patient, the capsule is moved wirelessly. for this purpose, the patient is wholly or partially in an electric coil system of several, for example fourteen, individual coils. are from coil system suitable magnetic generates fields or gradient magnetic fields which generate forces or torques on the capsule located in the patient in order to move them in the patient. This allows the capsule to be navigated within the patient. Areas of use here are mainly hollow organs, in particular z. B. the human gastrointestinal tract, which is traversable with the capsule in a single pass in its entirety.

A disadvantage of the known method is that for the generation ^¬ supply even small forces and torques on the capsule in the patient, the power consumption of the field generating coil system is extremely high.

The object of the present invention is to specify an improved method for driving such a capsule.

The object is achieved by a method for driving a permanent magnet containing capsule within a patient, especially ^¬ intestinal tract within which Gastro, with the aid of the patient's body to ^¬ least partially surrounding the electric coil system, in which a) for various rotational positions of the Permanentmag ^¬ Neten with respect to the coil system which is determined by the Spulensys ^¬ tem for generating a desired driving force on the capsule required power. The capsule is then brought into the rotational position associated with a desired power in step b) by rotation. In step c), the driving force on the capsule from the coil system he testifies ^¬ .

In order to move the capsule within the patient, it must be rotated or displaced during examination or treatment of the patient. A magnetic dipole moment in the capsule is an indispensable prerequisite for exerting forces or torques on the capsule by external magnetic fields generated by the coil system. For the sake of simplicity, in the text below, the capsule or the contained magnetic member applied forces and / or torques, the term "driving force" ver ^¬ one. In the inventive method, a permanent magnet is used. Compared to a magnetizable body is omitted so the generation of a magnetization in the body causing the magnetic field by the coil system. This is already reduces the power consumed by the coil system.

The direction and strength of the necessary driving force of the capsule depends on the position of the capsule in the body of the patient and the desired capsule movement. For example, to be moved tilted the capsule in the patient by 10 ° and in the direction of the capsule longitudinal ^¬ according to the shape of a small intestine loop to the current Kapselort through which the capsule is to be navigated. Thus, a desired driving force to ge ^¬ in the form of a force on the capsule and a Drehmo ^¬ mentes attack. For this, the capsule suitable magnetic fields to be generated by the coil system at the location as generating ^¬ derum interacts with the permanent magnets of the capsule, the desired driving force. For this purpose, the coil system must be traversed by suitable currents in such a way that it generates the corresponding magnetic fields.

The invention is now based on the insight that for He ^¬ generating the same desired driving force on the same Kapselort or place of the permanent magnet for different rotational positions of the permanent magnet relative to the coil system, the power consumption of the Spulensys ^¬ tems in a wide range varies. The reason for this is the asymmetrical structure of the coil system, which is just not spherically symmetric with respect to a center and certainly not with respect to the current location of the capsule. In order to be able to introduce the patient into the coil system, this is rather cylindrical or barrel-shaped. Therefore, the power consumption of the coil system becomes a He ^¬ generation of the driving force to the capsule for various Ro ^¬ tationspositionen of the permanent magnet relative to the coil system determined prior to the actual application of the driving force to the capsule or generating the magnetic field by the coil system. Manentmagneten different rotational positions of the Per ^¬ alone are adjustable by applying torque and not by applying translational forces on the capsule. Rotation positions of the capsule are thus z. B. rotations of the capsule in any direction about a pivot point in the capsule interior.

The power required by the coil system (ohmic loss ^¬ power) is equal to the sum of the electrical power loss of the individual coil currents, which are necessary for field generation. The determination of the power required to produce a desired driving force can be done in various ways. Possible are z. B. simulation calculations for given capsule location and desired drive ^¬ force at the time of generation of the driving force, ie in real time. It can also in advance for a given coil system at selected locations for selected driving forces and Ro ^¬ tationspositionen of capsules power consumption of the coil system are calculated tabulated and checked during the operation of the system only table values or be the extent interpolated mög ^¬ Lich (look-up-table).

The invention continues to use the recognition that the on ^¬ bring torques on the capsule generally a power consumption of the coil system is required, which is clearly lower than that which is necessary to produce a translational force on the capsule.

Since for generating the desired or one and the same driving force on the capsule depending on the Rotationsposi ^¬ tion now various, recorded by the coil system services are now available in the previous Step were determined, for the actual generation of the driving force a corresponding desired power from ^{¬ be} selected.

From belonging to different rotational positions of various required performances, the desired performance will be selected and brought the capsule by rotation in the ent ^¬ speaking rotational position. Thereafter, or simultaneously, the actual driving force is generated by a suitable choice of the individual coil currents on the capsule.

The steps b) and c) are thus initially sequential. With continuous capsule travel, however, both steps can also be carried out quasi - continuously and temporally parallel.

In process step) b can be selected as desired performance, the mi ^¬ nimale performance. This makes the total ^¬ is power consumption of the system is minimized, causing as little power loss and thus waste heat, less Di ^¬ dimensioning of the coil currents delivered final power ^¬ stages of the coil system allows and both manufacturing as also lowers operating costs of the overall system.

The capsule can have a longitudinal axis, and the permanent magnet ^¬ can rigidly be integrated into the capsule and having a transversely oriented to the longitudinal axis dipole moment. In OF INVENTION ^¬ to the invention methods can be selected then the capsule about its longitudinal axis as a rotational positions different rotational angle in step a).

In many cases, an appropriate, be used in the process ^¬ capsule a capsule certain preferred direction and is elongated. For example, at the top of a video camera may be provided. The capsule then has a longitudinal axis ^¬ on to which they mostly externally rotationssymmet is executed ^¬ driven. It makes sense to the Permanentmag ^¬ net then a transverse to the longitudinal axis aligned dipole moment to rotate the capsule about its longitudinal axis by applying an external magnetic field can. Usually, the capsule in the direction of the longitudinal axis is to be moved in front of Windwärts ^¬. The direction of the desired driving force is therefore parallel to the longitudinal axis.

Due to the aligned transversely to the longitudinal axis of the dipole moment of a rotation of the capsule about its longitudinal axis by a transverse to the longitudinal axis rotating magnetic field mög ^¬ is Lich.

If the capsule is also rotationally symmetrical, the outer shape of the capsule is imaged in itself at each rotational position, which causes the least possible friction with the organs abutting the capsule when the capsule is rotated. Also needs the capsule enclosing hollow organ are then not expanded to additionally ^¬ or deformed when turning. So just ge ^¬ shallowest torque for rotation of the capsule are necessary, which in turn the power consumption of the entire system at their redu ^¬.

In the method according to the invention, in step b), the permanent magnet can be rotatably mounted inside or on the capsule. During rotation of the permanent magnet, the capsule then does not have to be rotated or only partly rotated, which leads to no or lower friction losses between the inner wall of the hollow organ and the capsule. The rotation can e.g. also be carried out by motor inside the capsule and not be caused by external fields.

Also, the permanent magnet can be rotated into a part of the capsule and in step b) only this part. Also, friction losses during rotation are reduced and rotation can be accomplished by force generated in the capsule.

The coil system can comprise more than six individual coils whose coil currents can be controlled independently of one another, and for the desired driving force six vectorial Components ^¬ th be given. In step a) of the method according to the invention, the coil currents can then be resistance-weighted with the resistance of their coil winding in order to determine the required power. An underdetermined equation ^¬ system between the desired driving force and resistance-weighted coil currents is then set up. Are determined coil currents, both a residual error of the sliding ^¬ surveillance system as well as the weighted coil currents minimize their respective 2 standards with respect to.

A coil system has, for example, a total of fourteen individual coils, each of which can be flowed through by an independent coil current. Each single coil has an ohmic resistance. As driving force are, for example, the three independent Kom ^¬ components of the desired at the capsule strength and the three components one at the capsule desired torque preset which together _x the 6-dimensional vector F = (T, T _y, T _z, F _x, F _y , F _z ) ^τ form. Instead of the torque can in

F and the three components B _x , B _y , B, a desired magnetic field ^{¬ be} specified at the location of the capsule. Thus, with the 14-dimensional vector I = (I _i , I ₂ ,..., I _M ) ^{τ of} the unknown coil currents, the magnetic dipole moment of the permanent magnet in the capsule m = (m _x , m _y , m _z f and the location f = (x, y, z) ^{τ is} a system of equations F = W (f, m) I, with the 6x14 matrix W (r, m), which depends on the geometry of the coil system, the capsule location and the magnetic moment of the Capsule depends on the law of Biot-Savart and the basic equations of magnetostatics calculable.

By weighting each individual coil current / ₍ with ie {1,2, ..., 14} with the square root of the ohmic resistance

The associated coil produces a weighted current vector ϊ = ( _c JKl _ι . V ^ iJ- The power consumption of the electric coil system is given as: • ^To determine the total power

minimizing coil currents, the 2-norm is minimized and among all solutions

those chosen with the minimum 2-norm 7.

In the case of predetermined torques and forces, the rank of the matrix W is equal to five, because in the direction of the permanent magnetic dipole moment on the capsule no torque can be exerted. Given the 3 B field components and the force at the capsule location, the rank of W equals six. For the solution of certain equations with rank drop may one out.: Known singular value decomposition or a fully ^¬ constant orthogonal decomposition [GH Golub and CF Van Loan.. 1996 "Matrix Computations" Third Edition, John Hopkins University Press,] be used With a full row rank can For example, the QR decomposition described in the same source can be used.

For a further description of the invention reference is made to the embodiments of the drawings. They show, in each case in a schematic outline sketch:

1 shows a system for non-invasive diagnosis or treatment of a patient with an endorobot, FIG. 2 shows the endo-robot from FIG. 1 in a detailed view.

Fig. 1 shows an endoscopy system 2 for non-invasive Be ^¬ fundung or treatment of a patient 4. The endoscopy system 2 comprises a coil system 6 having connected thereto power supply 8 as well as a controller 10 and a video unit 12.

The coil system 6 consists of fourteen individual coils. Of the coils are provided for clarity in Fig. 1 only four with reference numerals. These are divided into six rectangular rectangular Helmholtz coils 14a, b and eight together form a cylinder jacket in the cuboid saddle coils 16a, b. Each of the saddle coils 16a, b sweeps over an angular range of approximately 90 ° with respect to a central longitudinal axis 18 of the coil system 6. Each four saddle coils 16a, b thus form a cylinder jacket, which are axially juxtaposed.

The current flowing in each of the fourteen individual coils coil current is in turn represented by a fourteen, each with a single coil fed arrange ^¬ th power amplifiers 20a-c generated, of which in Fig. 1, only three. The fourteen ^¬ power amplifier 20a-c together form the power supply 8. All power amplifier 20a-c are driven respectively by the controller 10 via a respective control line 22 regulated.

The patient 4 is retracted along the central longitudinal axis 18 in the Spu ^¬ lensystem 6. The patient 4 is placed in the coil system 6 in such a way that the endoscopy capsule 30 swallowed by him comes to rest approximately in the middle of the coil system. There, the coil system 6 has a so-called Arbeitsvolu ^¬ men, within which the capsule can be navigated.

The coil system 6, a coordinate system 32 is permanently assigned. The spatial position and the orientation of the longitudinal axis 34 of the endoscopy capsule 30 in the coordinate system 32 are detected by a position detection 36. The position detection 36 transmits the position data of the Endoskopiekap ^¬ sel 30 in turn to the controller 10th

In Fig. 2, the endoscopy capsule 30 is greatly enlarged Darge ^¬ represents. At its front end 38 the Endoskopiekap ^¬ sel 30 carries in its interior a camera and lighting device, not shown. Through a viewing window 40, the vicinity of the endoscopic capsule 30 is illuminated and can Ka ^¬ meraeinrichtung an image of the capsule around in the direction of arrow record 42nd The recorded image data are per Radio transmitted to a video receiver 44 outside the patient 4 and displayed on a screen 46.

To control the capsule movement in the coil system 6 or in the patient 4 is an input device in the form of a 6D mouse 48, which by an operator, not shown, for. A doctor examining the patient 4 is operated on the basis of the image displayed on the screen 46.

From the position shown in FIG. 1 in the stomach of the patient, the endoscopy capsule 30 is now to be moved from there into the small intestine and through it to the colon. The doctor, not shown, considers the video image delivered by the endoscopy capsule 30 on the ^moni tor 46 and navigates the endoscopy capsule 30 by hand to the stomach outlet and through the small intestine. For each navigation step now explained below pre ^¬ applies hens example.

2, the endoscopy capsule 30 is at its midpoint 50 at a position determined by the position detection 36 and thus known in the coordinate system 32. The orientation of the endoscopy capsule 30, ie its longitudinal axis 34, is thus also known. It should be moved in the direction of the arrow 42, that is along its longitudinal axis 34. For this purpose, a force 49 in the direction of the arrow 42 has to be exerted on the endoscopy capsule 30 by the coil system 6, which is shown only symbolically in FIG. 2.

In the endoscopy capsule 30, a permanent magnet 51 is included with a transverse to the longitudinal axis 34 oriented dipole moment 52. The instantaneous direction and rotation Posi ^¬ tion 53a of the dipole moment 52 in the coordinate system 32 is also known (on the position detection 36 and ^¬ due to the fact that a magnetic dipole moment is along an outer B field aligns). Since the set force 49 and the dipole moment 52 and the capsule position known 10, the controller 10 may determine a hypothetical current pattern in the coil system 6, ie the currents of the fourteen individual coils 14a, b and 16a, b, to generate a magnetic field 54 inside the coil system 6 which interacts with the dipole moment 52, the force 49 would be generated on the endoscopy capsule 30 or on the permanent magnet (not shown). At the same time, the electrical power to be absorbed by the fourteen output stages 20a-c is thus known in the controller 10. This is stored as power value 55a in the controller 10 and assigned to the orientation or rotational position 53a. The determination of the unknown coil currents takes place by the solution of the sub-determined equation system which describes them.

The field 54 is therefore not initially generated, i. no such current pattern is applied to the coil system 6, but only the power consumption theoretically necessary for this purpose is determined or calculated.

Based on the actual orientation 53a of the dipole moment 52, a hypothetical value of the power consumption of the power supply 8 is calculated in the same way for different imaginary angles of rotation 56 of the dipole moment 52 about the longitudinal axis 34. In FIG. 2 this is, for example, by rotating by 10 ° position 53b of the dipole moment 52 in phantom Darge ^¬ represents. In the dashed position of the dipole moment 52 in the coil system 6 or coordinate system 32, a field distribution 58 different from the field distribution 54 is necessary to generate the force 49. To generate this field distribution 58, another current pattern in the coil system 6 or the individual coils is necessary. Therefore, the power ^¬ recording of the power supply 8 is changed. This value of the power consumption is also stored as power value 55b in the controller 10 and assigned to the rotational position 53b. In this way, for different angles of rotation 56 of the dipole moment 52, starting from the current position as the 0 ° position, the respectively corresponding power values 55a-d of the power supply 8 for rotation angles 56 of, for example, 0 °, +/- 5 ° and +/- 10 ° determined hypothetically.

Then, from the power values 55a-d a ge ^¬ desired power consumption, z. B. the minimum power 55b, selected and the dipole moment 52 is actually rotated in the corre sponding ^¬ spatial position 53b by the rotation angle 56, in the example of Fig. 2 so by + 10 °, as in dashed lines ^¬ net. For this purpose, the entire endoscopy capsule 30 is rotated, but this means no external change in the capsule geometry due to its rotational symmetry. Then in the now modified position 53b of the dipole moment 52 is actually generated the appropriate coil current pattern in the coil system 6, resulting in a corresponding field distribution 58 with the result, and the force 49 actually acts on the dipole moment 52 and thus at the Endo ^¬ skopiekapsel 30th Due to the force 49 be ^¬ the endoscopic capsule 30 of the arrow 42 moves along its central axis 34 in the direction.

After displacement of the endoscopy capsule 30 by a certain distance along its central axis 34, the process just described is repeated to again determine the minimum power consumption of the Spulensys ^¬ tems 6 for further generation of a new force at the new location of Endoskopiekap ^¬ sel 30. In this way, it is possible to move the endoscopy capsule 30 along a path, for example, through the entire small intestine of the patient 4 with minimal effort.

A similar procedure also applies to the generation of torque by the action of magnetic fields on the dipole moment 52, so rotation of the Endoskopiekap ^¬ sel to allow 30 with the lowest possible power consumption of the coil ^¬ systems. 6 The rotational position of the permanent magnet is initially selected so that the cosinus between Permantentmagnetrichtung and torque direction is minimal. The optimal permanent magnet orientation, in which the power consumption of the coil system is as low as possible, can differ slightly from this rotational position due to the asymmetry of the coil system and is determined downstream.

Claims

claims

1. A method for driving a permanent magnet (51) containing capsule (30) within a patient (4), Special into ^¬ the gastrointestinal tract, with the aid of the body of the patient (4) at least partially surrounding e- lektrischen coil system (6), wherein: a) for different rotational positions (53a, b) of the Perma ^¬ mag- nets (51) with respect to the coil system (6) each from the coil system (6) for generating a ge ^¬ desired driving force (49) to the capsule (30) erfor ^¬ derliche power (55a-d) is determined, b) the capsule (30) by rotation (56) in which a Ge ^¬ desired power (55b) associated with the rotational position

(53b) is brought, c) the driving force (49) on the capsule (30) from the Spulensys ^¬ tem (6) is generated.

2. The method of claim 1, wherein:

- In step b) as the desired power (55 b), the minimum power is selected.

3. The method according to claim 1, wherein the capsule has a longitudinal axis and the permanent magnet has a dipole moment aligned transverse to the longitudinal axis, in which:

- In step a) as rotational positions (53 a, b) different angles of rotation of the capsule (30) about its longitudinal axis (34) are selected.

4. The method according to any one of the preceding claims, wherein:

- In step b) of the permanent magnet (51) within the cap ^¬ sel (30) is rotated.

5. The method according to any one of claims 1 to 3, wherein - The permanent magnet is contained in a part of the capsule and in step b) only this part of the capsule is rotated.

6. The method according to any one of the preceding claims, wherein the coil system more than six, each of an independent current / ₍ flowable individual coils includes, and ge ^¬ desired driving force F (49) six vector components are given, in which in step a) to determine the required power (55a-d):

- The coil currents I ₁ with the square root of the resistive Wi ^¬ resistance

their coil winding are weighted,

an underdetermined system of equations F

Zvi ^¬'s desired driving force F is / set up (49) and widerstandsge- weighted coil currents,

- coil currents / ₍ which are both residual

F -W (r, m) [dia.g (R)) / as well

minimize the weighted coil currents 7 with respect to their 2-norms.