DE102006045177A1 - Electromagnet for e.g. magnetic navigation of catheter tip, has ring coils provided parallel to each other at front sides of hollow cylinder, and saddle coils arranged between ring coils in circumferential direction - Google Patents

Abstract

The electromagnet (1) has ring coils (2, 3) provided parallel to each other, where the electromagnet is formed as a hollow cylinder. The ring coils are provided at front sides of the cylinder, and saddle coils (4) are arranged between the ring coils in a circumferential direction. The saddle coils are rotatable relative to the ring coils about a longitudinal axis of the cylinder. One of the saddle coils has a coil opening (7) permeable for X-rays and sized in such a manner that an X-ray detector e.g. planar image X-ray detector, is positionable or insertable through the opening.

Description

The The invention relates to an electromagnet for generating a magnetic field for the navigation of a medical instrument, the one with the Having magnetic field interacting element.

It is known, a medical element equipped with a magnetic element Instrument, for example a catheter tip, via an externally generated magnetic field, which acts on the instrument to move through hollow organs or to navigate. Appropriate catheter procedures are under investigation or treatment of the heart or in other mazy or branched Hollow organs performed. Due to the external navigation of the catheter tip, in which the magnetic element interacting with the external magnetic field, For example, a small permanent magnet is located, a Movement and precise guidance catheter tip and catheter around tight bends or ramifications allows. By the interaction of the external, directed magnetic field with the interacting with it at the top of the medical instrument arranged element can the alignment of the catheter tip through the control of the magnetic field varies and the catheter is guided and be navigated. To a sufficiently strong force or a sufficient strong torque by means of the magnetic field on the catheter tip or exercise the medical instrument to be able to becomes at the catheter tip a relatively high magnetic field with a depending on the desired Direction of movement defined spatial Orientation needed. For heart catheter with magnetic tip, the external magnetic field should be at the place of Catheter tip about 80-120 mT amount.

A device for navigating a medical instrument is known from US 2003/0137380 A1 known. There, two special rotatable and swiveling permanent magnets are used on the left and right sides of the patient couch at the level of the heart region, which lie opposite each other. They are encapsulated by appropriate steel panels, whereby the respective panel tapers towards the patient or tapering. Both magnet units are very difficult, since at a certain location a sufficiently strong magnetic field must be generated for the guidance of the medical instrument.

The magnetic navigation of the medical instrument, for example a catheter in a blood vessel or in the interior of the heart, is carried out under visual control by means of one or two C-arm computed tomography or X-ray devices. For the visual inspection, it is necessary to allow the corresponding image recordings from as many viewing angles as possible. However, this is the case in the quasi-rigid system according to US 2003/0137380 A1 only very limited possible. A horizontal viewing angle from left to right or vice versa through the thorax is not possible here, because the permanent magnets or the magnet units are in the way, so that the C-arm can not be positioned accordingly. Only oblique imaging is possible without colliding with the magnet units.

In the US 6,241,671 B1 It has already been proposed to generate the magnetic field for a navigation device with electromagnetic coils. Like there for example 2 It can be seen that the required coils are very large, so they are disturbing in investigations with a computed tomography device or an X-ray machine in the way.

A similar navigation device is from the US 6,014,580 known, in which also a plurality of mutually perpendicular and mechanically rigidly interconnected individual coils are used.

Of the Invention is therefore the object of an electromagnet for generating a magnetic field for navigating a medical Indicating the generation of a sufficiently high Magnetic field allows and at the same time allows image acquisition for visual inspection.

to solution This object is with an electromagnet of the aforementioned Art provided according to the invention, that it is designed as a hollow cylinder, at its end faces there are two parallel ring coils between which a plurality of circumferentially arranged saddle coils are arranged. The opening in at least one of the saddle coils is so large that through the opening Through an X-ray is possible.

Of the Electromagnet according to the invention has the advantage that the toroidal coils and saddle coils comparatively close to the patient who was taken up in the hollow cylinder can be, so that a relatively low Amperewindungszahl in the coils for the magnetic navigation of the medical instrument sufficient is.

A Further improvement can be achieved when the saddle coils relative to the toroids about the longitudinal axis of the hollow cylinder are rotatable. It is then possible to use the visual inspection the computed tomography device or the X-ray device through openings make the saddle coils, and from any direction perpendicular to the patient's longitudinal axis.

In the electromagnet according to the invention It is particularly preferred that it comprises four saddle coils, which preferably each extend over a quarter of the circumference.

at Other embodiments of the invention may provide that the electromagnet comprises four saddle coils, two of which are opposite Contain permanent magnets, preferably as a winding core are arranged in the saddle coils.

When Ring coils are preferably used so-called "race track coils", which have a constant, have rectangular cross-section. In the same way can also the saddle coils have a rectangular cross section, it will however, it is preferable that the saddle coils have a constant in area but in the form of variable cross section.

at The electromagnet according to the invention, the Ring coils and saddle coils Ladder made of aluminum or copper have, which are preferably provided with a paint insulation.

According to one Advantageous development of the invention, an X-ray source and / or an X-ray detector be arranged on saddle coils of the hollow cylinder. In such a rigid connection of the X-ray device with the hollow cylinder obstruction of the X-ray examinations is avoided. Alternatively, however, angiography may be performed mechanically independent of the hollow cylinder movable C-arm are performed, its movement by means of a control device with the rotation of the saddle coils synchronized hollow cylinder.

The Current supply to the individual coils of the electromagnet via current control units, z. B. power amplifier. For generating magnetic fields in any spatial direction, it is sufficient in usually, if opposite Coils can be controlled by a common power amplifier. Alternatively, especially in a coil system that is not symmetrical in pairs is constructed, each coil can be controlled by a separate power amplifier become.

The opening in one of the saddle coils is advantageously so large that a complete flat-panel tube detector in the opening can be mechanically retracted or used.

It can also be provided that in the solenoid according to the invention the size and / or the direction of the generated magnetic field by sole control the saddle coil currents by means a control unit can be influenced. This is useful if be changed with the solenoid switched on Angiographieblickwinkel should, what usually a rotation of the saddle cylinder is required. So that the magnetic field of the electromagnet is not changed is, the magnetic field can during the rotation of the saddle cylinder by the changed control of the Saddle coil currents kept constant.

Besides The invention relates to a navigation device with a device for generating a magnetic field for navigating a medical Instruments comprising an electromagnet according to the invention.

Further Advantages and details of the invention are described below of exemplary embodiments explained with reference to the figures. The figures are schematic Representations and show:

1 an electromagnet according to the invention with a hollow cylinder having coils;

2 an axial view of the hollow cylinder of 1 ;

3 a side view of the hollow cylinder of 1 ;

4 a second embodiment of the invention in an axial view; and

5 a third embodiment of the invention.

The 1 to 3 show an extracorporeal electromagnet 1 in different views. The electromagnet 1 is formed as a hollow cylinder, in the cavity in the interior of the electromagnet 1 a patient may be admitted during an examination or treatment. The electromagnet 1 includes toroidal coils 2 . 3 which are arranged at both ends of the hollow cylinder and between which saddle coils 4 are located.

In the illustrated embodiment, the solenoid comprises 1 four saddle coils distributed over the circumference 4 , Each saddle coil 4 consists of two axial coil sections 5 and two radial coil sections 6 wherein the axial coil sections 5 and the radial coil sections 6 together a coil opening 7 limit. The four saddle coils 4 form a saddle coil cylinder 8th that rotates in the toroidal coils 2 . 3 is stored. Each saddle coil 4 extends over about a quarter of the cylinder circumference and has a sufficiently large opening, so that an X-ray examination by two opposite coil openings 7 can be carried out. In particular, studies "from left to right" are possible, the could not be performed in conventional devices because of the large permanent magnets.

The ring coils 2 . 3 are "race-track coils" with a rectangular cross-section that is constant over the coil length, the coils are made of an aluminum conductor or a copper conductor with a rectangular cross-section, including the electrical insulation of the conductor realized by lacquer Coil have a conductor fill factor of more than 70% or even more than 80% 4 have a constant in area but variable in shape cross-section. The radial coil sections 6 have a rectangular cross section, whereas the axial coil sections 5 have a trapezoidal cross section, as in 2 you can see. In this way, the size of the coil openings 7 be maximized. On the other hand, the distance of the conductor core from the axial axis is minimized, whereby the power requirement is minimized for a given field strength in the working volume. The electromagnet 1 is designed to produce a free-field induction of approximately 100 mT in a cubic working volume of 10 × 10 × 10 cm ³ .

The four coil openings 7 in the rotatable saddle-cylinder 8th allow mono- and bi-planar angiography in any direction within the transversal-sagittal plane, as required in particular for electrophysiological procedures in the heart.

In 2 are an X-ray source 9 and an x-ray detector 10 shown arranged so that the x-rays are undisturbed by coil openings 7 reach. X-ray source 9 and x-ray detector 10 can be rigid on the saddle coil cylinder 8th Alternatively, the angiography can be arranged with one independent of the electromagnet 1 movable C-arm, its movement with the rotation of the saddle cylinder 8th is synchronized. The movement of the C-arm and the rotation of the saddle-cylinder 8th takes place computer controlled by means of a control unit.

When the solenoid is on 1 Angiographieblickwinkel is to be changed, is a rotation of the saddle coil cylinder 8th required. By a suitable control or reversal of the saddle coil currents by means of a control unit, the magnetic field during the rotation of the saddle coil cylinder 8th kept constant. A change in the currents through the toroidal coils 2 . 3 not necessary.

The 4 and 5 show further embodiments of the invention in an axial view, wherein for those components that match those of the first embodiment, the same reference numerals are used. In accordance with the first embodiment, the in 4 illustrated electromagnet 11 four saddle coils with axial coil sections 5 and two opposing coil openings 7 , In the openings of the two other saddle coils, which in 4 left and right are permanent magnets 12 . 13 ,

5 shows a further embodiment with an electromagnet 16 in which, inside two saddle coils, opposed permanent magnets 14 . 15 are located. The permanent magnets 14 . 15 are opposite the permanent magnets 12 . 13 of the foregoing embodiment, and thus can generate a stronger magnetic field.

The based on the embodiments explained Electromagnets have the advantage of being used in angiography are more flexible than conventional systems that rely exclusively on Permanent magnets are based. Another advantage is the shutdown to see the electromagnet. In addition, with the electromagnet by change the coil currents the direction of the magnetic field and its strength are changed much faster than this by mechanically moving heavy permanent magnets possible is.

Since the hollow cylinder designed as an electromagnet 11 can be rotated by a full 360 °, it is sufficient that two opposite saddle coils coil openings 7 wherein the opening, the coil eye, is dimensioned such that it can be angiographed through this opening. Ideally, the size of the coil openings 7 so chosen that a complete flat-panel detector of a C-arm through a coil opening 7 in the electromagnet 11 can be retracted so that the flat panel detector is as close as possible to the observed object, which may be an organ or tissue. The other two coils, which need not necessarily have an opening, are filled with a permanent magnetic material, wherein the magnetization runs along the preferred field direction of the energized coil, this magnetization direction is in the 4 and 5 symbolized by the arrows. Because the "edge current" of the permanent magnets 12 . 13 . 14 . 15 As an additional current acts on the inner circumference of the associated coil, the actually flowing electric current in the coil can be correspondingly reduced for a given field strength to be achieved.

For minimal electrical power consumption, the electromagnet, consisting of the coils and the permanent magnets, is designed that the maximum permissible electric current in the coil is able to wipe out the field of permanent magnets. By varying the electric current from the negative maximum value to the positive maximum value, the field of the coil changes between (practically) zero and the maximum value of the field strength. A reversal of the field direction is not absolutely necessary, since this already by a mechanical rotation by 180 ° of the existing of the four saddle coils hollow cylindrical electromagnet 11 . 16 can be done.

The conductor cross-section and the control by power amplifier of the electromagnet are designed for the maximum current value. At the two electromagnets 11 . 16 with the permanent magnets 12 . 13 . 14 . 15 in the coil openings, the maximum current value is reduced. Accordingly, the conductor cross-section can be reduced and / or the maximum power to be provided by the drive connected load can be reduced. Since opposing coils are typically driven by the same power amplifier and the three required power amplifiers are typically identical, in an optimized coil design, the conductor cross-section of the two open coils is larger compared to that in FIG 2 illustrated embodiment, at the same time, the conductor cross-section of the two coils with the permanent magnet is smaller, so that the summed maximum electrical power losses of the open coil pair and the coil pair with permanent magnets are the same.

There the conductor cross sections of adjacent saddle coils no longer the same are not necessarily cheap, to form all saddle coils as quarter circle coils. better it is when the coils with permanent magnet sweep over a circular arc segment <90 ° and the open coils sweep a circular arc segment> 90 °. In this version There is the advantage that the generated field strength with lower electrical currents is achieved, thereby reducing the electrical power consumption is.

Claims (14)

Electromagnet for generating a magnetic field for the navigation of a medical instrument, which has a magnetic field interacting element, characterized in that the electromagnet ( 1 . 11 . 16 ) is formed as a hollow cylinder, on whose front sides, two parallel annular coils ( 2 . 3 ), between which a plurality of circumferentially arranged saddle coils ( 4 ) are arranged. Electromagnet according to claim 1, characterized in that the saddle coils ( 4 ) relative to the toroidal coils ( 2 . 3 ) are rotatable about the longitudinal axis of the hollow cylinder. Electromagnet according to claim 1 or 2, characterized in that it comprises four saddle coils ( 4 ). Electromagnet according to one of the preceding claims, characterized in that at least one saddle coil ( 4 ) a X-ray transparent coil opening ( 7 ) having. Electromagnet according to claim 4, characterized in that the coil opening ( 7 ) is so large that an X-ray detector, in particular a flat-screen X-ray detector, through the coil opening ( 7 ) can be introduced or used in the coils. Electromagnet according to one of the preceding claims, characterized in that it comprises two mutually opposite permanent magnets ( 12 . 13 . 14 . 15 ), preferably in coil openings ( 7 ) of the saddle coils ( 4 ) are arranged. Electromagnet according to one of the preceding claims, characterized in that the toroidal coils ( 2 . 3 ) and / or the saddle coils ( 4 ) Have conductors with rectangular cross section. Electromagnet according to one of the preceding claims, characterized in that the toroidal coils ( 2 . 3 ) and / or the saddle coils ( 4 ) Comprise conductors of aluminum or copper, which are preferably provided with a paint insulation. Electromagnet according to one of the preceding claims, characterized in that assaxial sections ( 5 ) of the saddle coils ( 4 ) have a trapezoidal cross-section. Electromagnet according to one of the preceding claims, characterized in that an X-ray source ( 9 ) and / or an X-ray detector ( 10 ) on saddle coils ( 4 ) of the hollow cylindrical electromagnet is mechanically rigidly arranged or are. Electromagnet according to one of the preceding claims, characterized characterized in that it is operable together with a C-arm and the X-ray detector of the C-arm is retracted into the electromagnet and the electromagnet and the C-arm are preferably rotatably rotatable. Electromagnet according to one of the preceding claims, characterized characterized in that the size and / or the direction of the magnetic field generated by controlling the coil currents by means a control unit can be influenced. Electromagnet according to claim 12, characterized in that the magnetic field upon rotation of the saddle coils ( 4 ) can be kept constant by controlling the saddle coil currents. Navigation device with a device for Generating a magnetic field for navigating a medical instrument, characterized in that the navigation device is an electromagnet according to one of the claims 1 to 13.