DE102010051684B4 - Magnet-assisted navigation system for vascular catheterization - Google Patents

Abstract

Device for controlling the movements of a catheter-like tool (14) within a blood vessel by directing a magnetic field applied from outside the body, wherein a controller (16) is provided which is adapted to operate on the basis of a data structure constructed from a computer or magnetic resonance tomographic 3-d reconstruction of the vessel course (34) to determine the spatial orientation of the electromagnet (2), characterized in that a single magnetic gradient between the poles of a magnetized catheter tip (14a) and a single one, by a motorized mechanism in all electromagnets (2) movable in spatial directions, a tensile force is exerted on the catheter tip (14a), which simultaneously causes the retraction and the spatial orientation of the catheter (14) in accordance with the course of the vessel (34), the control being implemented as a synchronizing control , which depending on the current llen position of the intraluminal catheter tip (14a), continuously determined by electromagnetic detection, the spatial orientation of the electromagnet (2) and the motorized guide (8) of the catheter (14) outside the body, which provides intermittent mechanical retention of the catheter (14) exercised, controlled.

Description

However, clinical use requires intravascular conditions and it is very unlikely that they can be transferred to the conditions prevailing in body cavities or in body tissue. Above all, however, in the acute treatment of common vascular diseases (such as "cerebral stroke") in the context of standard inpatient care, a relevant superiority in therapeutic efficiency compared to conventional methods would be expected.

III. Requirement profile and state of the art in intravascular catheterization

(see Literature, p. 32)

Significant requirements for a procedure for intravascular catheterization become clear above all under the demanding anatomical conditions of the cerebral arterial vessels: One encounters vessels whose lumen has already narrowed distally to 2-3 mm (A. cerebri media) with correspondingly easily injured ones vessel walls. Additional disease-related (or age-related degenerative) stenoses of the lumen are possible at all levels of the "cerebral vascular tree" and sometimes occur one after the other as so-called "tandem stenoses". The vessels connected distally (Aa. perforantes, branches of the A. cerebri media) are currently difficult or no longer accessible due to their anatomy, disease-related narrowing and the often steep angle of their branching. Already one of the vascular trunks (A. carotis interna) shows a curvy course, which must be followed within a short distance in all 3 spatial directions.

This results in requirement 1: a sufficiently precise change of direction of the catheter tip within the smallest possible radius (if possible "on the spot") in order to be able to make tight curves while protecting the vessel walls.

Essential mechanical requirements for a high degree of mobility of the catheter tip consist of a tip with the smallest possible dimensions, the greatest possible flexibility of a catheter tube that is as thin as possible, the type of force acting on the catheter tip (shearing force, pulling force, rotary forces), the location of the application of force ( hose, catheter tip) as well as in magnetic procedures also in the strength and shape of the magnetic field (e.g. the greatest possible concentration of the magnetic field lines around the longitudinal pole axis) in connection with a permanent magnet with the smallest possible dimensions in the catheter tip in order to ensure prompt coupling to achieve with exact spatial alignment of the tip. In the case of magnet-assisted procedures, the degree of precision achieved also depends not insignificantly on whether a sufficiently finely graduated alignment of the magnetic field can be achieved mechanically and whether the alignment exactly reproduces the actual vascular anatomy, which means the "congruence" of the reference systems (imaging and navigation ) or an effective error control in the procedure-necessary positioning and horizontal shifting of the patient requires a sufficiently high "resolution" of today's imaging and the use of a sufficiently sensitive and precise detection system.
The ability to pass through a vessel or a stenosis, as well as the extent of distal advance ("supraselective catheterization") depend essentially on the interaction of precision, dimensions of the catheter tip and the strength of the applied magnetic field strength.

In contrast to the conditions in a body cavity (e.g. a heart chamber), a vessel imposes limits on the range of movement of the intraluminal catheter according to a "channel" depending on the lumen width. A lateral deviation of the catheter tip from the ideal path is "anatomically" limited, all the more so the thinner the vessel is.
For magnetic navigation, the result is that stable "embedding" of the catheter tip in a complex, controlled (homogeneous) magnetic field at all times, combined with stable "holding" of the catheter tip in its respective position and alignment, is not a mandatory requirement for the intravascular represents catheterization. Rather, it can be expected that a slight deviation of the catheter tip from the "ideal path" (in the context of a change in the position of the magnets or even a temporary loss of magnetic force) can be tolerated without endangering the result of the navigation or significantly delaying it - the difference for navigation within a heart chamber or within the brain tissue (stereotaxy).

Compared to other body tissues, the brain tissue has by far the greatest vulnerability to ischemia, which occurs acutely in many cases (thrombo-embolic) and only allows a short time corridor for causal therapy, ie for recanalization of the blocked vessel. Even if time corridors of 4 hours (“systemic lysis”) and up to 8 hours (“arterial lysis” with preceding catheterization) are currently being discussed, within which the statistical benefit of the treatment outweighs the risks, the ideal time for treatment is immediately after on the first symptoms appear in order to be able to expect complete recanalization and the avoidance of permanent neurological deficits.
The resulting requirement 2 for intravascular catheterization is therefore the highest possible speed of the procedure and the shortest possible time until the catheter is in its final position.

The navigation within vessels, heart chambers and parenchyma for the performance of various diagnostic and therapeutic interventions at a circumscribed location is still predominantly manual in today's inpatient primary care: "Interventionalists" in neuroradiology and cardiology currently use wire-supported navigation with guide wires made of stainless steel with a caliber size of 0.008 " to 0.014" (0.36 mm) that have to be positioned along the vessel before inserting the flexible microcatheter, which takes a relatively long time - on average between 45 and 60 minutes for the cerebral vessels - and depends to a large extent on the experience of the examiner . The corresponding inner diameters of the microcatheters used, which are pushed into the desired position over the guide wire after navigation, are usually 0.010" and 0.018" (0.46 mm). The feed is carried out both manually and mechanically (so-called "advancer").

• - Die Möglichkeit der Gerinselbildung an der Oberfläche des Katheters mit zunehmender Dauer des Verfahrens.
• - Die Möglichkeit, die Ischämie durch den eingeführten Katheter selbst zu verschlimmern, abhängig von dessen Durchmesser.
• - Sprunghafte, schwer kontrollierbare Bewegungen des Führungsdrahtes (Vorschnellen, „coning“ usw.) bei der manuellen Kraftübertragung vom proximalen zum distalen Ende des Drahtes, insbesondere bei langen Übertragungswegen.
• - Die Möglichkeit der Auslösung sog. Gefäßspasmen mit nachfolgender Ischämie, abhängig vom Ausmaß der Gefäßwandirritation.
• - Das relativ hohe Risiko der Verletzung von Gefäßwänden mit der Folge intrazerebraler Blutungen, Loslösung von Gefäßwand-Plaques, akuter Ischämie oder Dissektionen.
• - Die intolerable Zunahme dieser Komplikationen bei komplexen und / oder pathologisch stark veränderten Gefäßverläufen mit kombinierten steilen Gefäßabgängen, stark gewundenen Abschnitten und ausgeprägten Stenosierungen, die bisher nicht selten eine Anwendungsbeschränkung für die Gefäß-Katheterisierung bedeuten.
• - Der große Zeitbedarf angesichts der therapeutischen Erfordernisse, wie sie sich bei akuten vaskulären Krankheitsbildern (insbesondere beim „zerebralen stroke') ergeben.
• - Die Abhängigkeit des Resultats (und der Komplikationsrate) vom Erfahrungsstand des Untersuchers und demzufolge die Beschränkung des Einsatzes auf erfahrene Zentren, auch bei der Versorgung durchaus häufiger Krankheitsbilder.

Significant disadvantages resulting from this established advancement procedure relate to therapeutic efficiency, usability and safety of vascular catheterization:

• - The possibility of clot formation on the surface of the catheter as the procedure progresses.
• - The possibility of aggravating the ischemia from the inserted catheter itself, depending on its diameter.
• - Erratic, difficult-to-control movements of the guide wire (jumping, "coning", etc.) during manual force transmission from the proximal to the distal end of the wire, especially over long transmission distances.
• - The possibility of triggering so-called vascular spasms with subsequent ischemia, depending on the extent of the vascular wall irritation.
• - The relatively high risk of injury to vessel walls resulting in intracerebral hemorrhage, detachment of vessel wall plaques, acute ischemia or dissections.
• - The intolerable increase in these complications in complex and / or pathologically severely altered vascular courses with combined steep vascular branches, severely tortuous sections and pronounced stenoses, which up to now have often meant a limitation of the use of vascular catheterization.
• - The great amount of time required in view of the therapeutic requirements as they arise in the case of acute vascular diseases (especially in the case of "cerebral stroke").
• - The dependency of the result (and the complication rate) on the level of experience of the examiner and consequently the restriction of use to experienced centres, even when treating quite common clinical pictures.

The starting point in the development of magnet-supported navigation systems has always been the expectation that these essential disadvantages of manual advancement can be eliminated by means of a precise and possibly accelerated movement of the catheter through the vessel, and that a significant increase in the therapeutic effectiveness and safety of intravascular catheterization can be achieved as a result an extension of their application to previously very problematic vascular conditions or to the acute treatment of cardiac and cerebral diseases may also result.
The development over the past 4 decades was dependent on the availability of sufficiently compact and strong, axially symmetrical electromagnets, the applicability of sufficiently precise mechanics with degrees of freedom in all spatial directions, the quality of the imaging, the availability of suitable detection systems (electromagnetic , sonographic, biplanar fluoroscopy, etc.) as well as the development of application-oriented strategies, algorithms and procedures in dealing with these techniques, in which there is a growing understanding of the requirement profile of intravascular catheterization and the interactions between magnetic forces, catheter and the respective physiological and anatomical Conditions mapped (1, 2, 5, 7).
The development of such systems was initially motivated by cardiology and neurosurgery and was therefore also adapted to the special physiological and anatomical conditions prevailing in heart chambers and brain tissue. Here it proved to be advantageous to establish a continuously effective magnetic field that precisely aligns the catheter tip and "holds" it in its respective position in order to avoid possible deviations of the catheter tip from the ideal path or from its reached position and the target in the area of the heart chamber over the duration of the following therapeutic procedures to focus precisely. A special requirement profile arose for the magnet-supported navigation within the heart chambers, in which the rhythmic range of motion of the heart itself, the turbulent flow conditions, but also the consequences of a possible deviation of the catheter tip from the ideal path (due to loss of magnetic control) have a special role played. The step-by-step advancement of the catheter was conventionally left to the manual or mechanically applied pushing force - in each case after the previous alignment of the catheter tip by the magnetic field (2, 3, 4, 5, 6). The focus was on the complex control of superimposed or homogeneous magnetic fields, with the aim of aligning the magnetized tip of a guide wire or catheter along the magnetic field lines generated in the body, according to the anatomical conditions found, which were determined by imaging (computer or computer) prior to the intervention . Magnetic resonance tomography) were to be determined. Today, these systems usually envisage the use of several external electromagnets (magnet clusters), either mobilized and equipped with mechanical suspensions with different degrees of freedom for the orientation of their magnetic fields, or fixed in certain spatial directions, such as in an orthogonal or opposite arrangement, surrounding the vascular system in question (1, 2, 3, 6, 11).
Correspondingly complex process algorithms were developed for the computer-assisted implementation.
The Ritter et al. (3, 4, 5, 7) developed and now continuously further developed "magnetic navigation system" (MNS) by Stereotaxis ^R (Niobe II System, Stereotaxis ^R , St. Louis, Mo) is internationally in clinical use in the field of university and focused cardiological care. It works with two oppositely arranged, vertically pivotable, complex electromagnets and creates a homogeneous magnetic field of 0.1 to 0.3 tesla in the heart to align the magnetized catheter tip. The resulting speed that this complex control circuit generates in clinical use has not yet been adequately evaluated and assessed in comparison with other methods. The magnets are aligned for each new position within 5 - 10 seconds, plus the time required for the assessment of the current catheter position and the resulting controls by the examiner (who necessarily remains involved in the control loop of the procedure) and for the further intended mechanical advancement of the catheter is to be expended. The complex technical equipment ensures the exact and "holding" guidance of the catheter tip, as required for navigating within the heart chambers.

A pull-in of the catheter caused by magnetic force simultaneously with its magnetically caused navigation has been repeatedly suggested and discussed in previous developments (7), particularly in connection with the introduction of embolizing material in the form of magnetized so-called 'coils' into an aneurysm is to pull or push the material gradient-mediated against a suitable wall of the aneurysm.

Shacharet. al. (11) developed an elaborate magnet system which, in addition to a "navigating force field" to align the catheter tip to the generated field lines (0.15 - 0.3 tesla), also uses a gradient-mediated, longitudinal force effect to move the catheter (1, 6 - 3.0 tesla) uses. The complex modulation of the force field also allows the combination of the different force approaches and their synchronous use. However, the system is also very complex and controls the magnetic field via a cluster with a maximum of 8 electromagnets, each arranged in different symmetries and with a correspondingly complex controlling algorithm. Its speed in clinical application has also not yet been adequately evaluated.

Another line of development consists of an "all-in-one" concept closely based on the technology of magnetic resonance imaging or even an implementation of the navigation in the apparatus configuration of magnetic resonance imaging (8, 9, 10). Various working groups are currently working very great effort made. However, this development would make the use of navigation very complex in the long term and would restrict it to highly specialized centers of so-called maximum care.

Rather, the previous development has led to complex and costly systems whose scope of control goes beyond the requirement profile of an exclusively intravascular catheterization and whose focus is on special, elective interventions in cardiological or neurosurgical centers, but whose use is not possible due to the financial burden that cannot be met in the long term in standard inpatient care and for the acute treatment of frequent vascular diseases.
In addition, it remains questionable whether the time required for these complex systems until the catheter is finally positioned meets the requirements for acute treatment (such as a “cerebral stroke”).

From the document DE 10 2005 028 226 A1 is known a device for controlling the movement of a catheter-like tool with a magnetic catheter tip arranged at the front end of a long catheter tube. The device comprises a plurality of diametrically opposed magnets which are pivotally attached to an arcuate magnet arm which in turn can be moved in the circumferential direction via a bearing. If the catheter is to be advanced, the magnets generate such magnetic fields that the magnetic catheter tip is oriented in the desired direction. A joystick-like steering element is provided for this purpose. The catheter can be advanced manually or by motor. The steering of the catheter tip by the plurality of magnets on the one hand and the advancement of the catheter tube on the other are functionally separate.

In the previous development, the special focus was not on a magnetically guided insertion of the catheter through the activation of a single aligned magnetic gradient. The restriction to an exclusively gradient-mediated navigation with a single directed pulling force along the longitudinal gradient, which allows a magnetized catheter tip to "couple" and follow its spatial orientation, has not yet been raised to a fundamental principle for vascular catheterization and has not been subject to the appropriate methodological and apparatus Innovations and adjustments to clinical processes implemented.

• - eine vergleichbar rasche Katheter-Positionierung,
• - eine vergleichbar größere Sicherheit und geringere Traumatisierung,
• - eine relevante Ausweitung der Indikationsstellung bei seiner Anwendung sowie

leichzeitig eine relevante anwendungsorientierte Verfahrensvereinfachung im Vergleich mit bisherigen magnetischen Navigationsverfahren zu erreichen.It can be expected that an apparatus-based procedure corresponding to the one presented will be able to solve the problems associated with intravascular catheterization in order to

• - a comparably quick catheter positioning,
• - Comparably greater security and less traumatization,
• - a relevant extension of the indication for its use as well as

at the same time to achieve a relevant application-oriented process simplification compared to previous magnetic navigation processes.

The goals mentioned are to be achieved by establishing the process engineering prerequisites and problem solutions described.

IV. Methodical and technical innovations of the project

1. The restriction to a tensile force through the effect of a magnetic gradient between the magnetized catheter tip and a single external electromagnet that is spatially precisely aligned with a high degree of freedom ("pulling magnet") allows the intravascular catheter tip to be aligned and moved in one go ("synchronous navigation"). , whereby the force reversal (retraction instead of advance) equips the catheter with a "front drive", so to speak, supports the precise steering of the catheter tip and minimizes the risks compared to the manual advance procedure.

2. The use of a C-arm as an essential part of the supporting and aligning mechanics of the electromagnet, whereby two separately positioned mechanical units are provided: A so-called "internal mechanism" mediates the longitudinal displacement of the magnet along the C-arm and its inclination in relation to it the plane that the C-arm encloses. The motor unit is housed on the inside and inside of the C-arm and uses a rail inside the C-arm to move and a ball joint to tilt. A so-called "external mechanism" causes the C-arm to swivel around its horizontal axis and rotate around the plane it encloses. The motors are positioned within a joint encompassing the C-arm (for rotation) and within the stationary holding device for the C-arm (pivoting). "Inner" and "outer" mechanics allow a degree of freedom in all spatial directions for the spatial alignment except for the movement of the magnet within the plane that encloses the C-arm (the variation in the distance of the pole from the catheter tip is here caused by the variation in the magnetic field strength replaced).

3. The continuous action of the magnetic pulling force as well as a simultaneously lasting, mechanically mediated support give the catheter tip a dynamic "suspension" between the two opposing forces, which both creates its security and supports its magnetic coupling and its precise alignment with the longitudinal magnetic gradient .

4. The retraction of the catheter, which takes place in segments of variable length and at variable speed, due to the corresponding rotation of motorized rollers that guide and compress the catheter tube ("holder"), which adapt the respective catheter segment under the controlling and synchronizing influence of the system control to the effect of the continuously to the pulling force directed at the tip of the catheter (“permissive retraction”).

5. The use of a catheter next to its appropriately magnetized and attached the tip used for detection can retain a small diameter (0.5 - 1.5 mm) and have correspondingly favorable mechanical properties - essentially made possible by the omission of the power transmission required in the conventional feed method - and that via perforations in its hose connected to its tip, to improve its flexibility and to release diagnostic or therapeutic preparations.

7. The procedure for constructing a suitable data basis from the data set of a 3-D reconstruction of the vessel section created by computer or magnetic resonance imaging takes place before the start of the navigation and is carried out by a programmed algorithm. The data basis is used by the system control for the synchronizing control of all elements of the control loop during navigation. It includes the segmentation of the entire feed, the adapted variation sequence of the magnetic field strength, the resulting guide path of the pull magnet with corresponding positioning commands to its mechanics and a synchronized command structure to the "holder".

V. Detailed description of the procedure

(see VIII. Figures, p. 34 - 46)

The closed control loop of the procedure has "executive" devices (electromagnet and its mechanics, holder and microcatheter), "detecting" components (integrated electromagnetic detection, the tool to be detected in the catheter tip and the length determination by the holder) as well as the "system control “. The control circuit also has an interface to the data set of the previous imaging and an implemented algorithm for generating a system-compliant data basis. The system control mediates the controlling access of the examiner via a corresponding interface. Also provided are those devices that ensure an exact positioning of the patient, his horizontal displacement including a finely adjustable error correction.
and give a first overview of the arrangement of the electromagnet (2), its mechanics (1, 3 - 7) and the integrated electromagnetic detection (15b - 15d) from different viewing directions on a scale of 1:16.6 and 1:13.6. The specified mechanical dimensions are approximate values. In addition, the horizontally movable examination table (26), which connects the gantry (13) of the tomograph (11, 12) with the effective range of the navigation, as well as the horizontal resistance track (9), the patient's pad (10) and the Position of patient head support (46) shown. The position of the tomograph (11, 12, 13), which is not a tool inherent in the system, is therefore indicated. Front view and top view ( ) also indicate the estimated distance between the antennae (15b) and the patient's head and the distance between the markers (15c).

At the beginning of the process and even before the navigation, there is the procedure for constructing a suitable database (17) from the computer or magnetic resonance tomographic 3D reconstruction of the course of the vessel in question, to which the control of the navigation control loop is based from now on. such as , and show partial steps and results of this process.

The implemented algorithm (18) allows access to the imaging data set (11) via an interface. The course of the vessel (34) shown is first divided into virtual segments (37) over its entire length. The distance (38) of the section planes (37a) perpendicular to the longitudinal axis of the vessel is in a reciprocal relationship to the change in direction of the longitudinal axis of the vessel (36) (corresponding to the direction of flow), which determines the angle of the section planes to one another: the greater the change in direction the longitudinal axis of the vessel (ie the degree of curvature of the vessel), the denser the cut sequence (42). The default for the algorithm is therefore a specific angular dimension from which a new incision is made through the vessel reconstruction. The consideration of stenosis-related changes in direction (35) depends on the resolution of the imaging used (which has now reached a sufficient quality for this).
The sectional planes (37a) through the vessel reconstruction are related to the virtual coordinate system of the imaging (20). Then, for each segment, longitudinal vector guides (40) are made through the center of the vessel lumen, the spatial directions of which, also related to the coordinate system (20), depict the sequence of spatial directions in which the flow direction of the vessel is "targeted". The vectorial data are then transferred to the virtual coordinate system of the navigation (19), which is equivalent to a virtual horizontal displacement of the coordinate system (25), which must then be reproduced in exact accordance by the body that houses the vascular system (21). The result is a sequence of spatial alignments that the magnetic field of the pulling magnet (2) has to adopt in order to always bring the effective magnetic gradient into line with the longitudinal axis of the vessel and having the intravascular catheter tip magnetically coupled. The sequence of these spatial coordinates corresponds to the “path” (28) on which the pulling magnet (2) is guided around the relevant course of the vessel (34) during the subsequent navigation, in the sense of a precisely defined range of motion.
Finally, the spatial coordinates are translated into corresponding control commands, which are directed to the motorized mechanics of the magnet as a sequence during navigation (29, 30).

The resulting sequence of lengths of the segments (42) over the entire course of the vessel is translated into a corresponding command structure to the Holder (8), which is sent to the Holder's motors during the subsequent navigation, synchronized with the alignment of the magnet (32 ) to allow segmented insertion of the catheter.
Although the range of variation of the lengths (38) can only be determined by experimental evaluation, an exact replication of stenosis-related changes in direction of the vessel (35) over a short distance (in the range of a few millimeters) requires the shortest possible step sequences up to the most fluid possible retraction. At any later point in time during the navigation, the examiner can decide on the respective lengths of the catchment segments. The algorithm generated at the beginning of the process, on the other hand, already anticipates this decision and thus supports the automated flow of the navigation process.

The constructed database (17) also includes the necessary variation of the magnetic field strength in adaptation to the variation of the distance (39) between the magnet pole and the tip of the catheter as well as to possible (stenosis-related) resistances during the passage. A corresponding command sequence to the voltage generator (31) of the electromagnet is provided for the following navigation. For this purpose, for each longitudinal vector guidance through the vessel segments, the intersection points (19a) with the planes of the surrounding coordinate system (19) of the navigation (on which the electromagnet (2) moves) and thus also the respective distance between vessel and magnet pole (39), determined. The field strength is adjusted accordingly to ensure penetration of air, skin, calvaria, meninges, liquor and brain tissue (41) and also to enable the catheter to be pulled in. The priority for the algorithm is to achieve the pull-in with the minimum effective field strength (the controlling variation of the distance between the magnet pole and the vessel by the motorized mechanics is not provided for in the process and can at best be done as part of an error check by moving the patient table take place (see below)).
Although the "range" of the field strength to be used will only be the result of experimental and preclinical evaluation, a variation in the magnetic field strength between 0.5 and 3.0 tesla can be assumed in advance. In particular, the passage of stenosis-related resistance requires narrowing preclinical investigations.
In addition, the examiner can also vary the magnetic field strength at any time during the navigation via a corresponding interface (43), for example when passing through a resistance caused by a stenosis—one of the possible problem situations.

The procedure presented is based on the spatial and temporal separation between the acquisition of the data basis (imaging and its processing) and the execution of the navigation, which makes it necessary to temporarily move the body or the vascular system horizontally from the area of effect of imaging to the area of effect of navigation (s . .
As already described, when constructing the database, the imaging coordinate system (20) was transferred to the navigation coordinate system (19), which amounted to a “virtual horizontal shift”. Before the navigation begins, the body (21) in which the vascular system is located is also moved horizontally with the aim of restoring the “congruence” of the constructed data base and the real vascular system.

Systematic errors can result both from the process of horizontal displacement and from changes in the position of the body in the meantime. They can cause the catheter tip to deviate in all spatial directions, with displacements ranging from a fraction of a millimeter to several millimeters being to be expected. Inadequate congruence will sooner or later result in resistance to further retraction of the catheter provided by the vessel wall. Even deviations in the millimeter range would therefore not be tolerable, although they would prove to be problematic above all when passing narrow vessel windings, steep vessel branches or narrow stenoses, less so in stretched sections of a vessel.

The avoidance of such systematic errors includes (see )
1. the constant positional relationship (22) between the tomograph (11 - 13) and the navigation system (1 - 5, 7), whereby the distance between the two devices should be as small as possible,
2. A length-controlled horizontal displacement of the body, which is ensured here by using a resistance track (9) controlled by a voltage level, which carries the examination table, and
3. the fixed positioning of the body (46 and 47), possibly also prior sedation and muscle relaxation.

The error detection essentially results from the interaction of the selected detection method (15) (here an electromagnetic method) and the system controller (16) (both are described in detail further below). The system control receives position data about the catheter tip in real time and in electronically processable form from the continuous detection (15) and first compares this spatial data with the expected values of the generated database, s. . A current catheter position "outside" the expected vessel wall indicates insufficient "congruence".
(The detection of a deviation from "congruence" depends crucially on the sensitivity and precision of the selected detection method - previous application-oriented studies have shown that electromagnetic detection with sufficient precision and sensitivity can also detect small deviations or changes in the position of an intravascular Markers (probe, ring, etc.) can make recognizable).
Nevertheless, in this part of the procedure, i.e. before the start of the navigation, it may make sense to also carry out another imaging procedure with good precision and sensitivity, such as biplanar fluoroscopy, in order to detect a lack of congruence with regard to the course of the vessels and the position of the catheter tip to sharpen.
In addition, it is provided that the method of fault detection be carried out continuously or at short time intervals, also later during the navigation, although the horizontal displacement has been completed and active and passive movements of the body are counteracted.

Furthermore, a continuous length control is carried out for orientation control of the actual lengths of the feeder segments, s. by the holder during the move-in. The system control compares this data with the planned lengths of the retraction segments of the generated database and detects discrepancies that can indicate faulty retraction (resistance effective over a longer section, "jamming" of the catheter tip).

The correction for a lack of "matching" is shown in , through a fine adjustment of the body position in the millimeter range and in all 3 spatial directions (23, 24), which the examination table has and which is possible at any point in the procedure, with the system control specifying the direction and extent of the correction.
The correction is therefore initially made by changing the position of the body and not by recalculating the data basis. The algorithm used is designed to allow the corrective procedures to take place automatically - the examiner, however, retains the option of making the corrections himself, either via the interface or manually at the table.
In addition, the database can be recalculated at any time based on the current data on the position of the catheter tip.

As in and shown, a single electromagnet (2) is provided as the executive element of the control circuit (“single-coil system”). When adapting to the needs of this navigation system, the technical possibilities already available are used: A superconducting electromagnet (2) to be cooled in the form of a cylindrical, axially symmetrical ring made of a copper coil (2b) compressed in an airtight manner with an exposed ferromagnetic core cylinder (2a ) that generates a sufficient magnetic force field (up to 3 tesla) and is able to concentrate the field lines of its pole-side magnetic field as strongly as possible along the longitudinal axis (36, 39), followed by the sufficient magnetic coupling of the catheter tip (14b). The resulting pole distance during navigation, s. , from the facing pole of the catheter tip (14b) depends on the respective position of the magnet and the position of the vessel and is estimated at 10 - 40 cm. The media to be penetrated (41), in addition to the air between the pole and the cranial vault, consist of skin, cranial bones, meninges, liquor and vessel walls, and also brain tissue of varying thickness up to the target vessel (34 or 37), and represent a supra-individual small fluctuating part of this distance. A magnetic field strength of 0.5 - 2 tesla could be sufficient.
The expansion of the core cylinder will probably reach a pole face diameter of 12-15 cm and a length of 45-50 cm.
A flow of about 0.4 - 0.5 gpm is used for water cooling. be enough
(in not shown).
A hydraulically induced advancement and retraction of the iron core inside the magnet in order to variably expand the magnetic pole and change the concentration of the field lines is initially not provided here (a possible requirement This will result from the pre-clinical application of the method).
A parabolic shield surrounding the magnet and coated accordingly, which could also lead to an intensification of the force field, is also initially not planned (in not shown).

The motorized mechanism is designed to support the weight of the pulling magnet while allowing it to be spatially aligned with sufficient accuracy. As in , and shown is a C-arm (1) made of steel
(or consisting of another sufficiently resilient material) is provided, which leads to the inside of the magnet. The C-arm surrounds the body part in question at a distance that leaves enough space for the magnet, but also allows the pole face to be as close as possible to the body surface.
The construction includes an "inner" ( and ) and “external” mechanics
( ). Their combination enables the magnet to be mobile in all spatial directions - by moving it along the arc (3e), pulled by a motor block (3a), which moves along a rail of the C-arm (3c), by pivoting the arc (1a ) mediated by another engine block (6) and by the inclination (3d) of the magnetic axis relative to the plane of the C-arm, mediated via a ball joint (3b).
The range of motion of the magnet is further increased by the rotation of the C-arm (1b) around the plane it encompasses, mediated by a motorized joint (4) articulating with another slide rail of the arch, which is attached to the stationary element of the supporting holding device ( 5) is attached. This rotation allows for more lateralization of the magnet to either end of the C-arm. However, it is not always possible in all planes (horizontal, vertical or inclined planes) or can only be carried out to a limited extent due to the space requirements of the body part in question (27, so-called “exclusive zone”).
The sequence of the magnet movement and the corresponding chain of position commands to the motors of the mechanics were already generated at the beginning of the procedure within the framework of the constructed data basis and are transmitted during the navigation from the system control (16) to the "inner" and "outer" mechanics (29, 30). Since, in addition to the longitudinal concentration of the magnetic field lines, the step intervals when the magnet changes direction also have an influence on the exact alignment of the force effect and on the magnetic coupling of the catheter tip, movement segments that are as small as possible (in the millimeter range or as an almost continuous movement) - corresponding to the smallest possible segmentation of the course of the vessels.
The examiner retains the option of moving and aligning the magnet himself at any time during the procedure via his interface (43) by specifying the length and number of individual steps and influencing the direction in space using suitable equipment.

Another executive element, presented in , consists of a motorized mechanical apparatus (holder) (8), which is located outside the body, leads the catheter tube to the point of entry into the body (so-called "sluice") (8i) and by means of an arrangement of 5 transverse to the longitudinal axis of the Guide rollers (8a) provided by the catheter exert a continuous, compressive pressure on the catheter tube, which counteracts the tensile force of the magnet continuously acting on the catheter tip and prevents it from being drawn in during the drawing-in interval.
The retraction takes place with the controlled rotation of the 5 guide rollers (8a), which in this way "release" a segment of the catheter tube with variable length and variable speed and "allow" its retraction through the continuously effective magnetic pulling force (permissive retraction) . The number and lengths of all indentation segments were determined at the beginning of the process when constructing the data basis (17). However, they can also be defined by the examiner at any later point in time (43).
The holder has a glass frame (8j) for better observability of its functions and is firmly connected to an elongated guide rail (8h) which guides the catheter tube (14d) within a protective groove before it enters the holder (8g) and after it exits (8i ) to the so-called “lock” (entry into the body). The engine block includes 5 separate electric motors (8b) whose drive shafts merge into the respective rotation rods (8k) of the rollers. While the 3 rollers positioned under the catheter tube and the associated 3 motors have fixed roller bearings (8d) or suspensions, the 2 rollers positioned above the catheter tube with their corresponding motors have a vertical “cushioning” suspension in the form of a front rail ( 8c) with 2 roller bearings for the rotation rods of the two rollers and a correspondingly springy suspension for the motors.
The two upper rollers and their motors are flanked by 2 compressors (8f) which apply variable pressure to both the front transverse rail (8c) and a rear transverse rail (8e),
which rests on the two upper electric motors (8b), exercise. This leads to the lowering of the two upper roller-motor units, thus to the com priming and retention of the catheter tube. The two compressors work in sync, lowering the front and rear rails the same amount needed to compress the hose sufficiently while still allowing the rollers to rotate.

The electric motors are subject to the system controller (32), from which they receive appropriate signals during navigation, for example in the case of an intermediate retraction of the catheter. They also work synchronously and allow the reels to rotate in both directions and at variable speeds. With continued compression of the catheter tube (and continuous effective traction on the catheter tip), it is pulled in with the synchronous rotation of the rollers, which is controlled in terms of speed and duration. The restraint remains effective during the controlled retraction, which prevents the catheter from jumping out in an uncontrolled manner (and corresponding traumatization of the vessel walls). Feeding stops when rotation stops.
The rotation in the other direction allows a controlled retraction of the catheter as well as its removal from the vessel. In the case of a longitudinally immobile catheter tip, indicating significant deviation, its entrapment, or resistance due to stenosis, counter-rotation of the guide rollers and measured retraction of the catheter can be used to guide it (and also the system control) to the previous position and thereby remobilize the catheter tip.
The rotation of the guide rollers is connected to a continuous length control (33) of the feed segments, the results of which are continuously sent to the system control for comparison with the previously calculated values of the database and thus also for the detection of errors or faults in the feed to serve.

Both during the retraction and during the retraction intervals, the catheter tip, which is located in the corresponding retraction segment (37) of the vessel (34), gets into a special position ("suspension") between 2 opposing forces, shown in , namely the continuous pulling force of the aligned electromagnet (2) acting on the catheter tip and the simultaneous mechanical support provided by the holder (8) via the catheter tube. On the one hand, this opposing application of force causes a permanent longitudinal tensioning of the catheter tube (14d), but at the same time supports the magnetic coupling of the catheter tip (14a) and its exact alignment on the longitudinal tension gradient (36) and counteracts a lateral deviation of the catheter tip.

On the other hand, it is to be expected that the longitudinal tension of the catheter tube could lead to damage to the vessel wall and the detachment of plaque, conceivable as a result of the exertion of pressure and the "dragging" of the catheter tube on the inner vessel wall (34a), particularly in the area of vascular turns and branches (Das Occurrence and the extent of this undoubtedly harmful effect will have to be clarified by pre-clinical evaluation). To control this possible risk factor, the system algorithm provides for the adjustment of the applied field strength of the pulling magnet within a 'range' (0.5 - 2 tesla) with orientation at the minimum of the required field strength.

Although it can be expected that both catheters and guide wires of different diameters and magnetized materials can be intravascularly navigated for various clinical tasks using the method presented, the use of a correspondingly thin microcatheter (14) (0.5 - 1.5 mm diameter) provided, shown in , the clinical use of which is likely to be in the recanalization of acute vascular occlusions by means of lysis. The procedure presented here makes it possible to dispense with the use of guide wires and also leads to a not inconsiderable time saving.

• Mit dem Ziel, einen möglichst punktförmigen Ansatz der Zugkraft an der Katheterspitze zu erreichen, bildet ein zylindrischer permanenter Magnet (14b) möglichst kleiner Polfläche (0,5 - 1,5 mm Durchmesser) den vorderen Bereich der Katheterspitze (14a). Seine magnetische Achse ist in Längsachse des Katheters ausgerichtet und seine Polfläche nach vorn konisch zugespitzt, um das magnetische Ankoppeln zu verbessern. Geeignete, magnetisch gut ansprechende Materialien sind verfügbar, wie etwa NbFe35, NdFeB (Neodym-Eisen-Barium) oder SMCo5 (Samarium-Cobalt). An den Magneten schließt sich die detektionsbezogene Vorrichtung (14c) an, im vorliegenden Verfahren ein umgreifender (0,5 - 1,0 mm Durchmesser), möglichst schmaler (0,5 mm) Ring aus polymerisiertem Kunststoff, dessen intraluminäre Position vom verwendeten elektromagnetischen (RADAR-)System zu bestimmen ist. Die Katheterspitze sollte dabei eine Gesamtlänge von 2,5 mm nicht überschreiten, um enge Richtungswechsel auch innerhalb von Gefäßen mit Durchmessern von 2 - 3 mm noch zu ermöglichen.

Das verwendete Schlauch-Material (14d), das auch die Katheterspitze umschließt, weist neben einer sehr glatten Oberfläche bestimmte mechanische Eigenschaften auf: Bei der Verwendung sehr dünner Katheterschläuche (0,5 mm Durchmesser) wird eine große Flexibilität bewahrt, was die Beweglichkeit der Katheterspitze verbessert und enge Richtungswechsel mit möglichst kleinem Radius erlaubt. Allerdings lässt im vorgestellten Verfahren die kontinuierliche „Aufhängung“ des Katheters zwischen Zugkraft und Rückhalt eine longitudinale Anspannung des Schlauchs erwarten, was wiederrum seine Flexibilität und damit die Führbarkeit der Katheterspitze einschränken mag. Auch diesbezüglich sieht der Steuer-Algorithmus des Systems stets die Anwendung einer möglichst niedrigen Feldstärke des Zugmagneten vor, um diesen Effekt zu begrenzen.
Gleichzeitig erfordert die besondere Positionierung des Katheters zwischen Zugkraft und Rückhalt eine möglichst geringe Elastizität in Längsrichtung, um eine passagere Dehnung des Schlauchs mit Abweichen der Katheterspitze zu vermeiden.A variety of models that are already in clinical use can be used to design the microcatheter:

• A cylindrical permanent magnet (14b) with a pole surface that is as small as possible (diameter 0.5-1.5 mm) forms the front area of the catheter tip (14a) with the aim of achieving as punctiform an application of the pulling force as possible on the catheter tip. Its magnetic axis is aligned with the longitudinal axis of the catheter and its pole face is tapered forward to enhance magnetic coupling. Suitable materials with good magnetic response are available, such as NbFe35, NdFeB (neodymium iron barium) or SMCo5 (samarium cobalt). The magnet is followed by the detection-related device (14c), in the present method an encompassing (0.5 - 1.0 mm diameter), as narrow as possible (0.5 mm) ring made of polymerized plastic, the intraluminal position of which depends on the electromagnetic ( RADAR) system is to be determined. The catheter tip should not exceed a total length of 2.5 mm to avoid narrow direction exchange even within vessels with diameters of 2 - 3 mm.

The tubing material used (14d), which also encloses the catheter tip, has certain mechanical properties in addition to a very smooth surface: When using very thin catheter tubing (0.5 mm diameter), great flexibility is retained, which limits the mobility of the catheter tip improved and allows tight changes of direction with the smallest possible radius. However, in the method presented, the continuous "suspension" of the catheter between traction and restraint leads to the expectation of a longitudinal tension in the tube, which in turn may limit its flexibility and thus the ability to guide the catheter tip. In this regard, too, the system's control algorithm always provides for the use of the lowest possible field strength of the pulling magnet in order to limit this effect.
At the same time, the special positioning of the catheter between tensile force and restraint requires the least possible elasticity in the longitudinal direction in order to avoid temporary stretching of the tube when the catheter tip deviates.

The flexibility of the tube material, the length of the catheter tip and the type of force applied (tractive force) have a significant influence on the position of the pivot point when the catheter changes direction. The flexibility of the hose and the shortness of the catheter tip should be optimized so that the pivot point is positioned as far forward as possible. To further optimize the flexibility of the tube as close as possible to the tip of the catheter, 4 perforations ("slits") (14e) are provided in the longitudinal direction of the catheter, offset by 45° directly behind the tip of the catheter, in order to predispose this section in particular as a pivot point.
In addition, the lysis preparation and the contrast agent emerge through these perforations.

The control loop of the navigation is closed by its detecting leg, which uses electromagnetic detection for which data and clinical experience are already available. It serves to determine the position of the catheter tip with sufficient accuracy in real time.
When choosing the detection method (capacitive, inductive, optical and electromagnetic methods are currently in use or evaluation in this highly specialized field of application), priority was given to an inexpensive method that works in the presence of strong magnetic fields and dense structures (bones ) penetrates, which has a high resolution and sensitive detection and which provides the position data on the position of the catheter tip in real time and in electronic form to the system control and can therefore also provide an important prerequisite for an automated sequence of the navigation process (visual processes, such as biplanar fluoroscopy, mean that the examiner necessarily remains involved in the control loop of the procedure by assessing the image material / visualization of what is happening and making appropriate decisions).

For the application of electromagnetic detection, it is also advantageous that it permits different configurations and thus allows adjustments to practical requirements that may only arise when the navigation method is implemented and used (UW RADAR, continuous wave (CW) radar, Frequency Modulated (FM-CW) Radar or Pulse Doppler Radar).

Their coordinate-oriented data structure, which can be related to the coordinate system of the navigation, represents a further advantage over other detection methods.

The selected electromagnetic detection achieves the goal of its task by recognizing the energetic differences of the materials in the catheter tip against the surrounding background ("RADAR signature") and referring to an integrated spatial coordinate system, which in turn relates to the coordinate system of navigation in cover.

represents the implemented detection: Sequential UWB signals are emitted and received by 4 - 6 antennas (15b), which are positioned as close as possible to the patient on the floor and above the C-arm (1). The distance to the patient's head is about 80 cm (see Fig. ).

The signals reflected by the tip of the catheter (14c) are sent to a radio frequency module (15), modified into a "signature" in such a way that they can be optimally distinguished from the signals in the environment, amplified and related to an integrated coordinate system. whose 8 "markers" are also arranged near the patient in the C-arm and in another C-arm with an orthogonal position to the main C-arm in such a way that they describe the corner points of a cube (with synchronous panning of both C-arms) and their echo -Signals to build the coordinate system (15a) can be used. The distance between two markers is about 80 cm.
Thereafter, the conversion into electronic impulses is carried out by an analog-to-digital converter for further processing by the system control (15e and 16). The position data is here finally referred to the coordinate system of the navigation and compared with the already generated database. The detection appears to be sufficiently sensitive and precise to detect even minor systematic errors in the horizontal displacement of the patient and in establishing the spatial "congruence" of the generated database and the real position of the catheter tip (the course of the vessel). Possible deviations would be immediately recognizable at the beginning of the navigation and would be amenable to correction. There may still be opportunities to increase precision and sensitivity during development, e.g. E.g. by changing antenna positions.
The detection and imaging of the current spatial orientation of the intravascular catheter tip (possibility that can result from a very high resolution of the detection system and from the use of 2 detection coils in the catheter tip) are of no essential importance for the presented navigation method and for the exclusively intravascular catheterization : Smaller lateral deviations of the tip from the ideal path appear tolerable, while the larger deviations that disrupt progress are counteracted by the continuous alignment of the tip with the pull gradient on the one hand and, on the other hand - at least in the case of vessels with thin lumen - are limited by the canalizing vessel walls.

The controlled and synchronized interaction of the executive and detecting parts of the control loop, shown in , is realized by the software-supported system control (16) on the basis of the generated database and its continuous comparison with the detected position of the catheter tip.
It receives continuous data from the detection (15) on the current position of the catheter tip, relates it to the data in the generated database (17) of the system and continuously takes the exact alignment of the vascular path (i.e. its “congruent” reproduction) Magnetic field (29, 30) by sending appropriate control commands to the motors of the mechanics of the electromagnet.
A corresponding sequence of commands is sent synchronously to the mechanics of the holder (32) in order to release a certain retraction segment of a defined length at a defined speed to the pulling force (31) of the magnet, which is also synchronously adapted to the respective distance between the magnet pole and the tip of the catheter via appropriate instructions to the voltage generation of the magnet.
After the catheter segment has been retracted, the system control receives information about the actual retraction length (holder) and the new actual position of the catheter tip (detection) "in the sense of feedback".

Even before the start of the navigation, as well as at short time intervals during the navigation, the system control analyzes the data obtained with regard to sufficient "congruence" and corrects the deviation either automatically or gives instructions for error correction to the examiner, which initially uses a correction of the patient's position.
However, the algorithm also provides for a correction by generating an adapted data base again. The investigator makes the decision.
Implemented algorithms ensure that possible problem situations are mastered and possible errors are corrected during navigation, thereby creating an essential basis for safety, speed and an automated process flow.
Strong resistance to the further insertion of the catheter may serve as an example of a problem to be expected: The algorithm must then first distinguish whether there is only a lack of "congruence" between navigation and the real course of the vessel, whether there is only a stenosis (with possible deviation of the catheter tip). ) determines the resistance or whether it is a combination of both. Based on the result of this analysis, errors or problems can be corrected automatically or determined by the examiner, such as horizontal readjustment of the patient's position on the examination table, retraction of the catheter to remobilize the catheter tip or a temporary increase in the magnetic field strength.

Under defined conditions (to be defined in each case before the procedure), the system control stops the automatic procedure with a corresponding error or problem message and hands it over to the examiner via a corresponding interface (mode change). The system control already provides an adapted action plan for the subsequent "problem management". The examiner can also bring about this change of mode himself at any time during the procedure.
The system control presents the examiner with a continuous synoptic visualization of the processes in real time on the monitor (44). It contains the reconstruction of the course of the vessel on generated data basis and the current position of the catheter tip, visualizes the degree of "congruence" and, in the event of an intolerable deviation, also shows the spatial direction in which a position correction should be made (although mostly a horizontal correction is to be expected).

In addition, the system control ensures that the procedure is documented on data carriers in accordance with the criteria and standards.

The navigation system presented has options for optimizing the performance of the system (in particular the speed of the process and the precision with which the catheter is positioned) at various elements of the control loop, which only becomes clear as further development proceeds. Certainly, the system would benefit from changes that improve the magnetic coupling, alignment, and mobility of the catheter tip. Here, in particular, there should be potential for further optimization.

VI. Expected benefit

1. 1. bisher schwierig zu passierende anatomische Gegebenheiten - physiologisch- oder krankheitsbedingt - wie etwa Tandem-Stenosen, hochgradige Stenosen, starke Krümmungen oder steile Gefäßabgänge ausreichend exakt nachvollzogen werden können, daher passierbar werden, und dass ebenso dünnlumige distale Gefäßzweige besser erreicht werden können (im Vergleich mit dem gängigen Vorschub-Verfahren) - entsprechend der Anforderung 1 an die Gefäß-Katheterisierung (s. S. 4),
2. 2. eine Zeitersparnis im Verfahrensablauf in Aussicht steht, die im Wesentlichen aus der Art der Kraft (Zugkraft) und ihres Ansatz-Punktes (Katheterspitze), dem ermöglichten Verzicht auf die Anwendung eines Führungsdrahtes, aus der Verfahrensvereinfachung sowie aus dem erreichten Grad der Automatisierung resultiert und was dem besonderen zeitlichen Erfordernis bei der Akutbehandlung zerebraler Gefäßverschlüsse entgegen kommen würde (im Vergleich mit dem gängigen Vorschub-Verfahren, wie auch mit den bisher entwickelten magnetgestützten Systemen) - entsprechend der Anforderung 2 an die Gefäß-Katheterisierung (s. S. 6),
3. 3. ein erheblich günstigeres Risiko- bzw. Komplikations-Profil für die Gefäß-Katheterisierung erreicht werden könnte, was neben den patientenbezogenen Vorteilen unter anderem eine wesentliche Voraussetzung für anwendende Kliniken darstellt, fortan auf die bisher erforderlichen aufwendigen Anpassungen, wie etwa das Vorhalten einer Neurochirurgie in Bereitschaft, verzichten zu können (im Vergleich mit dem gängigen Vorschub-Verfahren),
4. 4. die Indikationsbreite für die Gefäß-Katheterisierung (im Bereich der Akutbehandlung vaskulärer Verschlüsse nach Ausprägungsgrad und Lokalisation der Läsion, nach Alter des Patienten, nach Komorbidität des Patienten) nachhaltig erweitert und einer deutlich größeren Anzahl von Patienten als bisher zugänglich gemacht werden könnte,
5. 5. das System eine Verfahrensvereinfachung mit sich bringen würde (Reduzierung der technisch-apparativen Aufwands und der sofware-basierten Ausstattung), im Wesentlichen resultierend aus der Beschränkung auf einen einzelnen Elektromagneten zum Erreichen einer synchronen Navigation (gegenüber den bereits entwickelten magnetgestützten Systemen),
6. 6. das Navigations-Ergebnis in geringerem Maße von klinischen Erfahrungen und manuellen Fertigkeiten des Untersuchers abhinge, als es beim herkömmlichen Verfahren der Fall ist, was sich im Wesentlichen aus dem erreichten Grad an Automatisierung ergeben würde (im Vergleich mit dem gängigen Vorschub-Verfahren),
7. 7. sich unter Berücksichtigung der Aspekte 1. bis 6. der Weg in die stationäre Regelversorgung für die Gefäß-Katheterisierung eröffnen könnte, wobei ihr Hauptnutzen dann im Wesentlichen in der Akutbehandlung häufiger vaskulärer Verschlüsse, insbesondere der hirnzuführenden Gefäße, zur Abwendung oder Abmilderung bleibender neurologischer Defizite und lebenslanger Behinderungen bestehen könnte.

The favorable influencing of essential mechanical parameters (degree of mobility of the catheter tip, precision of its steering, cross-section of the catheter) through the interaction of all components of the control loop shown allows us to expect that for the clinical application of the method

1. 1. Anatomical conditions that were previously difficult to pass - due to physiology or illness - such as tandem stenoses, high-grade stenoses, severe curvatures or steep vascular branches can be reproduced with sufficient accuracy and are therefore passable, and that distal vascular branches with thin lumen can also be reached more easily (in Comparison with the common feed method) - according to requirement 1 for vascular catheterization (see p. 4),
2. 2. there is a prospect of saving time in the course of the procedure, which essentially results from the type of force (tractive force) and its point of application (catheter tip), the possibility of dispensing with the use of a guide wire, the simplification of the procedure and the degree of automation achieved and what would meet the special time requirement in the acute treatment of cerebral vascular occlusions (compared to the common feed method, as well as with the previously developed magnet-supported systems) - according to requirement 2 for vascular catheterization (see p. 6) ,
3. 3. a significantly more favorable risk and complication profile for vascular catheterization could be achieved, which, in addition to the patient-related advantages, is an essential prerequisite for clinics using it, from now on to the previously required complex adjustments, such as the provision of neurosurgery willing to be able to do without (compared to the usual advance procedure),
4. 4. the range of indications for vascular catheterization (in the area of acute treatment of vascular occlusions according to the severity and location of the lesion, the age of the patient, the comorbidity of the patient) could be sustainably expanded and made accessible to a significantly larger number of patients than before,
5. 5. the system would result in a simplification of the process (reduction of the technical and equipment costs and the software-based equipment), essentially resulting from the restriction to a single electromagnet to achieve synchronous navigation (compared to the magnet-supported systems already developed),
6. 6. the navigation result would depend to a lesser extent on clinical experience and manual skills of the examiner than is the case with the conventional method, which would essentially result from the degree of automation achieved (compared to the conventional feed method) ,
7. 7. Taking aspects 1 to 6 into account, the path to standard inpatient care for vascular catheterization could open up, with its main benefit then essentially being in the acute treatment of frequent vascular occlusions, in particular of the vessels supplying the brain, to avert or alleviate permanent neurological deficits and lifelong disabilities could exist.

Without wanting to anticipate the results of a later clinical evaluation of this procedure (e.g. in comparison with the established systemic lysis), it can be expected that its clinical application will result in significant advantages for the range of indications, the therapeutic effectiveness, the risk profile and possibly There can also be advantages for the cost-benefit ratio (in clinics of different categories) for vascular catheterization, which are very likely to be positively correlated with each other.

VII. Literature

• 1. Jenkins A, Parker H "Electromagnetic support arrangement with three-dimensional control" J Appl Phys 1959; 30:238-239
• 2. Montgomery DB et al. "A new magnet system for intravascular navigation" Med Biol Engl 1968; 6:143-147
• 3. Howard MA, Mayberg M, Grady MS, Ritter RC, Gillies GT U.S. Patent No. 5,125,888 (1992)
• 4. Grady MS, Howard MA, Dacey RG et al. "Experimental study of the magnetic stereotaxis system for catheter manipulation within the brain" J Neurosurg 2000; 93: 282-288
• 5. Mc.Neill RG, Ritter RC "Characteristics of an improved magnetic-implant guidance system" Biomechanical Engineering 1995; Volume 42
• 6. Creighton IV "Magnetic navigation system and magnet system therefor" US Patent No. 7,305,263 (2007)
• 7. Knight et. al. "Control method for magnetic stereotaxis system" US Pat. No. 5,654,864 (1997)
• 8. Gillies GT "Catheter navigation within an MR imaging device" US Patent No. 6,834,201 (2004)
• 9. Kucharczyk J "Combined magnetic resonance imaging and magnetic stereotaxis surgical apparatus and processes" US Patent No. 6,298,259 (2001)
• 10. Zhung K, Krafft AJ "Real-time MR navigation and localization of an intravascular catheter with ferromagnetic components" Magn Reson Mater Phy 2010; 23:153-163
• 11. Shachar Y "Apparatus for shaped magnetic field control for catheter, guidance, control and imaging" EP 2080488 A2 (2009).

character list

• (p. 34) with an overview of the navigation control loop. The executive parts are red, the detecting parts are blue, and the controlling parts are black.
• (p. 35) on the construction of the “navigation coordinate system” and its “virtual horizontal shift”.
• , and (p. 36) for the construction of the data basis.
• (p. 37) shows the horizontal displacement of the patient.
• (p. 38) shows the electromagnet and its "internal mechanics".
• (p. 39) shows the range of motion of the "inner mechanics".
• (p. 40) shows the range of motion of the "external mechanics".
• (p. 41) shows the holder in side view and top view.
• (p. 42) shows the microcatheter in cross section, side and front view.
• (p. 43) illustrates the opposite application of force at the tip of the catheter.
• (p. 44) shows the integrated electromagnetic detection.
• (p. 45) shows the side view of the navigation system
• (p. 46) shows the front view and top view of the navigation system.

Claims (7)

Device for controlling the movements of a catheter-like tool (14) within a blood vessel by directing a magnetic field acting from outside the body, wherein a controller (16) is provided which is adapted to operate on the basis of a data structure constructed from a computer or magnetic resonance tomographic 3-d reconstruction of the course of the vessel (34) to determine the spatial orientation of the electromagnet (2), characterized in that via a single magnetic gradient between the poles of a magnetized catheter tip (14a) and a single one, driven by a motorized mechanism in electromagnets (2) movable in all spatial directions, a tensile force is exerted on the catheter tip (14a), which simultaneously causes the retraction and the spatial orientation of the catheter (14) in accordance with the course of the vessel (34), the control being designed as a synchronizing control, which depends on the current position of the intraluminal catheter tip (14a), continuously determined by electromagnetic detection, the spatial orientation of the electromagnet (2) and the motorized guide (8) of the catheter (14) outside the body, which provides intermittent mechanical retention of the catheter (14) exercised, controlled. device after claim 1 , characterized in that the tip (14a) of a microcatheter (14) in its front portion cylindrical, permanent magnet (14b), the pole axis (36) of which lies in the longitudinal axis of the catheter (14), and has the detection-specific device (14c) in its rear section, and that the catheter tube (14d) has longitudinal perforations (14e) immediately behind the catheter tip (14a) for exiting the therapeutically or diagnostically active substances and for improving its flexibility. device after claim 2 , characterized in that a motorized mechanism for guiding (8) the catheter section outside the body is provided, which counteracts the tensile force of the electromagnet (2) continuously acting on the catheter tip (14a) with a mechanical retention of the catheter (14) by an arrangement rollers positioned transversely to the longitudinal axis of the catheter causes compression of the catheter tube (14d), the catheter tube (14d) is released by rotation of the rollers (8a) at variable speed and duration so that it can be drawn in by the magnetic field, as a result of which the tensile force is continuously acting on the catheter tip ( 14a) allows the catheter (14) to be retracted in a segmented to almost flowing manner, the catheter (14) is retracted in a controlled manner by the counter-rotating guide (8) of the catheter tube (14d) and, after completion, is extracted from the vessel again, as well as a continuous determination of the length of the retraction segments undertakes, the results of which are continuously sent to the system be routed to the control for further control of the feed. device after claim 3 , characterized in that the motorized mechanism (8) carries the electromagnet (2) on the inside of a C-arm (1a) that can be pivoted about its horizontal axis and is longitudinally displaceable, additionally the inclination of the electromagnet (2) and its polar axis (36) relative to the plane that the C-arm encloses, provides for the rotation of the C-arm around the plane that it encloses, and receives continuously synchronized electronic instructions to the motors from a system controller (16) for positioning the electromagnet (2) with freedom of movement in all spatial directions around the part of the body that accommodates the vessel course (34) in question. device after claim 4 , characterized in that the system controller (16) positions the electromagnet (2) so that the magnetic gradient is always brought into line with the longitudinal axis of the vessel section (34) and is coupled to the magnetic catheter tip (14a). Device according to one of claims 1 until 5 , characterized in that before the start of the navigation, the construction of a database for controlling the entire method of navigation is provided by a computer-assisted procedure, the algorithm of which is based on the data set of a computer or magnetic resonance tomographically created 3-D reconstruction of the course of the vessels (34) allows access to the fact that over the entire length of the relevant vessel section there is a segmentation depending on the respective degree of curvature and for each segment (37) a longitudinal vector guidance is carried out through the center of the vessel volume and referred to a virtual coordinate system - with the results of a draft of the guidance path of the electromagnet (2), whose pole axis (36) is always aligned with the longitudinal axis of the flow direction of the vessel and the flow direction always points to the electromagnet (2), a sequence of corresponding position commands to the mechanism (1) of the Elektroma magnets (2) and a control sequence for the mechanism for guiding (8) the catheter (14) outside the body. device after claim 6 , characterized in that the electromagnet (2) is designed to vary the magnetic field strength to be applied, preferably by an embodiment with a displaceable core (2a).

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