DE102016117763B4 - Marker and medical device for visualization of instruments and devices under MR imaging and method of manufacture - Google Patents

Abstract

Marker (1) for the visualization of instruments and devices under MR imaging, wherein the marker (1) is formed from at least one plastic and wherein in the marker (1) at least one individually located cavity (2) with solid walls (3) is formed and enclosed by the plastic, which is at least partially filled with plastic, such that the plastic in the cavity (2) is in liquid consistency, wherein the filling of the cavities (2) and the walls (3) have the same plastic ,

Description

The invention relates to a marker and a medical device for the visualization of instruments and devices under MR imaging and to methods for the production thereof.

Performing image guided interventions, e.g. B. Biopsy, puncture or ablation is under imaging by magnetic resonance imaging (MRI), for example, with a Siemens Skyra MRI 3T MRI http://www.healthcare.siemens.de/magnetic-resonance-imaging, difficult to carry out feasible. The MR-compatible instruments or guides are not imaging hard, or not properly visible. Therefore, their orientation from the puncture point relative to the target structure (intervention trajectory) can not be determined exactly.

1 shows by way of example a section of an MR-guided biopsy with a stainless steel biopsy needle ( e ), which can be recognized as an artifact in the form of a broad, blurred "beam". ( C. Thomas, et al .: Carbon Fiber and Nitinol Needles for MRI Guided Interventions, European Journal of Radiology, Volume 79, Issue 3, September 2011, Pages 353-358, ISSN 0720-048X, http: //dx.doi .org / 10.1016 / j.ejrad.2010.07.007 .)

All instruments and devices used for interventions under MRI should be MR-compatible. MR compatibility means that the instruments and devices used in the MRI do not pose a risk to the patient under any circumstances, that they are not attracted to the magnetic field of the scanner and that they do not cause massive imaging disturbances, such as artifacts.

The MR visibility of a medical instrument depends on the strength and orientation of the static MR magnetic field, the image sequence used, the material of the instrument, the materials in the immediate vicinity of the instrument, e.g. B. by guide means, the construction of the instrument and the orientation of the instrument to the main magnetic field.

MR imaging is based on the nuclear magnetic resonance property of various chemical elements. In clinical application, mainly the nuclear magnetic resonance of hydrogen protons is used to generate an MR image from the signals that can be measured in this way.

Since soft tissue consists to a large extent of water, they are particularly visible. The different relaxation times of individual tissue types and the concentration of hydrogen nuclei contribute to the image contrast or to the differentiability of anatomical structures.

In particular, because conventional MR-safe instruments and devices do not contain free hydrogen atoms, they are not or only very poorly, e.g. B. by signal cancellation, visible in the MRI. Their orientation relative to the highly visible patient tissue can thus often not be determined in MR-guided interventions.

Nevertheless, the intervention trajectory for achieving a target structure, z. B. to comply with a biopsy needle, MR-visible markers are used. They can be divided into active, semi-active and passive markers. Active markers are excited by externally supplied electrical energy to generate a magnetic field.

Semi-active markers lead to a local elevation of the high-frequency alternating magnetic fields used in MRI. Passive markers are visible in the MR image because they either exhibit a local change in the static magnetic field, i. cause inhomogeneity or because they themselves contain substances that allow a nuclear magnetic resonance and thus a distinction to the surrounding material or tissue.

From the US 2014/0 275 964 A1 For example, a marker flange is known for use with a brachytherapy applicator having a flange body having a first surface, a second surface, and a hollow chamber positioned between the first and second surfaces. A cavity extending through the flange body is dimensioned to receive a tandem in a brachytherapy applicator in a press-fit connection to secure the flange marker to an outer surface of the tandem. The hollow chamber comprises an MR imaging responsive marker that provides high signal intensities and high geometric accuracy in MR imaging.

From the US 2012/0 292 814 A1 For example, a method of making a medical implant comprising a radiopaque marker is known. The method includes producing a medical implant using stereolithography, wherein the medical implant has an outer surface that defines an opening to a channel. A curable blend of a biocompatible polymer and a radiopaque material is then introduced into the channel in a liquid state and cured in the channel to solidify in the channel.

Known from DE 100 58 538 B4 is, for example, a medical device with built-in markers for direct or indirect detection and imaging in MRI, where the markers are individually localized, tablet-like bodies filled with a gadolinium-water liquid or pure water.

• - bildgeführte Interventionen am MRT nicht oder nur schwer durchführbar sind, weil die Instrumente und Führungseinrichtungen nicht MR-sicher oder nicht im MR-Bild sichtbar sind;
• - bisher existierende Marker aufgrund der verwendeten Materialien zu ungewollten Bildartefakten führen können oder oftmals keine Strukturen auf weisen, mit denen die Interventionstrajektorie eindeutig bestimmt werden kann oder
• - die Herstellung individueller Marker, die an die unterschiedlichen Anforderungen verschiedener Interventionen angepasst sind, aufwendig und teuer ist.

Disadvantages of existing systems emerge superficially from the fact that

• - image-guided interventions on the MRI are difficult or impossible to perform because the instruments and management devices are not MR-safe or not visible in the MR image;
• - Hitherto existing markers may lead to unwanted image artifacts due to the materials used or often have no structures with which the intervention trajectory can be clearly determined or
• - The production of individual markers, which are adapted to the different requirements of different interventions, is complicated and expensive.

Against this background, the object of the present invention is to provide a marker and a medical device for the visualization of instruments and devices under MR imaging and a method for the production thereof, with which the aforementioned disadvantages can be overcome.

This object is achieved by a marker according to claim 1, a medical device according to claim 5, a method according to claim 6, as well as the further advantageous embodiments according to the subclaims.

Suggested markers ( 1 ) for the visualization of instruments and devices under MR imaging, wherein the marker ( 1 ) is formed from at least one plastic and wherein in the marker ( 1 ) at least one individually located cavity ( 2 ) with solid walls ( 3 ) is formed and enclosed by the plastic, which is at least partially filled with plastic, such that the plastic in the cavity ( 2 ) is in liquid consistency and thus suitable for visibility in magnetic resonance tomography.

This invention describes a marker that can be used for the visualization of instruments and devices under MR imaging. The marker can work as a passive marker, but depending on a selected or predetermined model geometry or cavern filling, the marker according to the invention can also act actively.

The inclusion of liquid building material in cavities of models has hitherto generally been considered disturbing, especially in the corresponding generative manufacturing processes. Either the inclusion had to be accepted or strategies had to be devised to remove the surplus, liquid material, eg. B. by means of their own channels in the model or by subsequent drilling to be developed. By contrast, this invention utilizes this property to keep the building material fluidly contained in the model caverns.

The marker ( 1 ) can have multiple cavities ( 2 ), which, depending on their intended visibility in an MRI, are arranged relative to one another according to defined dimensions and positions, preferably rotationally symmetrical to an axis ( z ).

With the nature of the visibility of these cavities in the MRI slice images, z. B. skew, unbalanced or symmetrical, the orientation of the marker can be detected relative to the image plane and further also adjusted until the orientation of the marker ( 1 ) and thus the orientation of the instrument or the device is optimal, for. When the instrument axis is collinear with the intervention trajectory by achieving fixed target patterns in the MR image layers.

An embodiment of the invention provides that the material for the marker ( 1 ) is a photosensitive, liquid plastic which hardens under the influence of light of a certain wavelength.

In addition, other principles besides light for curing of the plastic or resin are possible, such as. B.:thermal, z. B. by means of heat, mechanically, z. B. by means of ultrasonic stimulation or chemically, for. B. by reaction with a hardener.

Likewise, the marker ( 1 ) be formed such that the material is hardened by chemical reaction. For example, acrylic, epoxy or vinyl ester resins can be used.

The invention provides that the marker ( 1 ) is designed such that the substance for the filling of the cavities ( 2 ) and for the walls ( 3 ) have the same plastic. This has the advantage that the construction of the walls and the filling of the cavities can take place at the same time.

In addition, unwanted interactions between the cavities and walls, caused by reactions between different substances, can be avoided.

Likewise, the substance for the filling of the cavities ( 2 ) and the material for the walls ( 3 ) different plastics or different materials, eg. As natural oils, resins or solid natural substances. Likewise, pure and mixed materials can be used. This allows improved MR visibility properties, e.g. B. relaxation time, contrast can be achieved.

A medical device is proposed which comprises at least one marker according to the invention ( 1 ), in which instruments can be fastened and guided on or in this device. With knowledge of the relative positions of the instrument and marker in the device, the MR visibility of the marker can also be used to draw clear conclusions about the orientation of the instruments.

1. a) Individuelle Gestaltung von dem Marker-Modell mit Wänden und zumindest einem Hohlraum,
2. b) Fertigung des Markers nach den Modellvorgaben durch Aufbau der Wände und unter Einschluss des Hohlraumes.

A method for producing a marker ( 1 ) for the visualization of instruments and devices under MR imaging, comprising a generative manufacturing method comprising at least the following steps:

1. a) individual design of the marker model with walls and at least one cavity,
2. b) Manufacture of the marker according to the model specifications by building the walls and including the cavity.

Here, the starting material or the starting materials for the marker and / or the medical device may have a liquid, gel or pasty form, such. B. in the processing of conventional silicones.

This marker can thus be produced by generative manufacturing processes, for example in the rapid prototyping process, also called RP processes.

As building material for the marker, a liquid resin can be used, which is cured in a specific manner along a predetermined model geometry. This is how the defined model is created in layers.

In addition, the building material in the liquid state causes a nuclear magnetic resonance, which is comparable to that of water or soft tissue. Thus, it is similarly visible on MRI.

With the layered manufacturing principle, it is also possible to include uncured areas inside the model. In these "cavities", the resin remains liquid, thereby distinguishing in visibility from the cured surrounding structures in MR imaging.

• - manueller Fertigung,
• - CNC-Fräsen,
• - Bohren.

Alternatively, the marker according to the invention can also be prepared by other, non-additive methods, for example by means of

• - manual production,
• - CNC milling,
• - drilling.

1. a) Bereitstellung einer Druckeinrichtung nach generativem Fertigungsprinzip zur Verarbeitung von zumindest einem Ausgangswerkstoff,
2. b) Bereitstellung einer individuell gestalteten Modellgeometrie zur Ausbildung des Markers (1), wobei in der Modellgeometrie zumindest ein Hohlraum (2) ausgebildet wird, in dem der Werkstoff unverarbeitet verbleiben kann,
3. c) Verfestigung des Ausgangswerkstoffs in der Druckeinrichtung entlang der Modellgeometrie,
4. d) Verschließen des Hohlraums (2), vorzugsweise durch den weiteren Aufbau von Wandstrukturen.

An embodiment of the invention comprises a method for producing a marker ( 1 ), comprising a generative manufacturing method with at least the following steps:

1. a) providing a printing device according to a generative manufacturing principle for processing at least one starting material,
2. b) provision of an individually designed model geometry for the formation of the marker ( 1 ), wherein in the model geometry at least one cavity ( 2 ) is formed, in which the material can remain unprocessed,
3. c) solidification of the starting material in the printing device along the model geometry,
4. d) closing the cavity ( 2 ), preferably by the further construction of wall structures.

1. a) der flüssige Werkstoff für die Markerwände und Hohlräume befindet sich in einem Vorratsbehälter, in dem die Bauplattform so gelagert ist, dass sie anfänglich nur dünn mit dem Werkstoff bedeckt ist,
2. b) entsprechend der vorgegebenen Modellgeometrie wird der flüssige Werkstoff mittels Licht (z. B. UV-Laser) lokal erhärtet,
3. c) die Bauplattform wird in der Höhe um den Wert der Schichtdicke in dem Werkstoffbad abgesenkt, sodass die zuvor gehärtete Schicht wieder dünn mit flüssigem Werkstoff bedeckt ist und der Prozess beginnt von Neuem bis das Modell fertig aufgebaut ist.

For example, the realization of the claim (A9) according to the generative manufacturing principle of stereolithography done (see also: https://de.wikipedia.org/wiki/Stereolithographie:

1. a) the liquid material for the marker walls and cavities is located in a reservoir in which the construction platform is mounted so that it is initially only thinly covered with the material,
2. b) according to the given model geometry, the liquid material is locally hardened by means of light (eg UV laser),
3. c) the construction platform is lowered in height by the value of the layer thickness in the material bath, so that the previously hardened layer is thinly covered again with liquid material and the process begins again until the model is finished.

1. a) der flüssige Werkstoff bzw. die flüssigen Werkstoffe für die Markerwände und Hohlräume wird/werden entsprechend der vorgegebenen Modellgeometrie schichtweise mit mehreren Druckdüsen auf einer Bauplattform aufgetragen,
2. b) unmittelbar nach dem Auftrag wird z. B. der Werkstoff für die Wände mittels UV-Licht erhärtet,
3. c) die Bauplattform wird in der Höhe um den Wert der Schichtdicke abgesenkt und der Prozess beginnt von Neuem bis das Modell fertig aufgebaut ist.

According to the method, the production of the marker ( 1 ) also according to the multijet principle, see also: https://www.google.com/webhp?ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&ei=gU7iV8SrN4jZ8Ae1 n7-ABg, the following steps include:

1. a) the liquid material or the liquid materials for the marker walls and cavities is / are applied according to the predetermined model geometry in layers with a plurality of pressure nozzles on a construction platform,
2. b) immediately after the order is z. B. the material for the walls hardened by UV light,
3. c) the construction platform is lowered in height by the value of the layer thickness and the process begins again until the model is finished.

1. a) der feste Werkstoff für die Markerwände wird aufgeschmolzen und entsprechend der vorgegebenen Modellgeometrie schichtweise über eine oder mehrere Druckdüsen auf einer Bauplattform aufgetragen,
2. b) unmittelbar nach dem Auftrag wird neben den Markerwänden der flüssige Werkstoff für die Hohlräume über eine weitere Düse im Bereich der Hohlräume aufgetragen,
3. c) die Bauplattform wird in der Höhe um den Wert der Schichtdicke abgesenkt und der Prozess beginnt von Neuem bis das Modell fertig aufgebaut ist.

Another alternative production method according to the FDM principle may include, for example, the following steps:

1. a) the solid material for the marker walls is melted and applied in layers according to the given model geometry via one or more pressure nozzles on a construction platform,
2. b) immediately after the application, in addition to the marker walls, the liquid material for the cavities is applied via another nozzle in the region of the cavities,
3. c) the construction platform is lowered in height by the value of the layer thickness and the process begins again until the model is finished.

According to the invention, the walls ( 3 ) are made of the same plastic, with which the cavities ( 2 ) are filled.

According to a further embodiment of the invention, the walls ( 3 ) are made of a first plastic and the cavities ( 2 ) are filled with a second plastic.

Another embodiment provides that the cavities are not completely closed to the outside. As a result, minimum openings may remain, z. B. so that air can escape completely.

Advantageously, the material in the cavities can change its state of aggregation. This ensures that single or multiple cavities for MR visibility can be disabled or even activated. This function can, for. B. be used to support the differentiability of the visible structures in the respective image layers.

Another embodiment of the marker provides that the visible marker cavities or cavities ( 2 ) are formed in the MR imaging not as orienting, but as surrounding structures, such that the walls ( 3 ) are available for orientation. The orientation for aligning the marker then takes place via the visible patterns or struts of the solid marker walls. Thus, the marker walls can be made thinner, which z. B. the time for the generative production of the marker is shortened.

The marker can be attached to instruments or assistive devices.

Due to the defined geometric expression of filled with liquid resin cavities, eg. B. in the form of several rotationally symmetrical, vertical and horizontal cuboids, it is possible to detect the position of the marker relative to its surroundings by means of MR imaging.

With this manufacturing principle, it is also possible to include uncured areas inside the model. In these "cavities", the resin remains liquid, thereby distinguishing in visibility from the cured surrounding structures in the MR imaging.

Because the plastic, z. B. resin of the additive manufacturing, both in the solid and in the liquid state is fully MR-compatible, it leads, in contrast to metallic MR markers, no artifact formation.

The geometric shape of the marker shape and the cavities can be individually adapted to the requirements of different applications for each marker model.

By physically referencing instruments to the marker model, their intervention trajectory can be precisely defined.

The production of the marker via generative manufacturing is precise, fast, individual and cost-effective. The RP-MR marker is fully MR compatible, i. no attraction and no artifact formation.

The invention will be explained in more detail below with reference to further figures in the form of exemplary embodiments, the invention not being limited thereto.

• 2: schematisch einen Marker (1),
• 3: schematisch den Marker aus 2 mit verdeckten Kanten (1'),
• 4: schematisch eine Schnittdarstellung des Markers (1) in y-z-Ebene,
• 5: schematisch eine weitere Schnittdarstellung des Markers (1) in x-y-Ebene
• 6: schematisch eine weitere Schnittdarstellung des Markers (1),
• 7: schematisch eine weitere Ausbildung des Markers (1) in rotationssymmetrischer Form,
• 8: schematisch den Marker aus 7 mit verdeckten Kanten,
• 9: schematisch den Marker aus den 7 und 8 in der y-z-Schnittebene,
• 10: schematsch eine weitere Ausbildung des Markers (1) in der Schnittansicht durch die x-y-Ebene,
• 11: schematisch eine Schnittansicht des Markers aus 10 schief um die Y-Achse,
• 12: schematisch einen achsensymmetrischen RP-MR-Marker (1),
• 13: schematisch den Marker aus 12 mit verdeckten Kanten,
• 14: schematisch den Marker mit einer Schnittansicht durch die x-z-Ebene,
• 15: schematisch eine weitere Schnittdarstellung des Markers (1) durch die y-z-Ebene
• 16: schematisch eine weitere Schnittansicht des Markers (1) durch die x-y-Ebene und
• 17: schematisch eine allseitig schiefgeschnittene Ansicht des Markers (1).

Show it:

• 2 : schematically a marker ( 1 )
• 3 : schematically the marker off 2 with hidden edges ( 1' )
• 4 : schematically a sectional view of the marker ( 1 ) in yz plane,
• 5 : schematically another sectional view of the marker ( 1 ) in xy plane
• 6 : schematically another sectional view of the marker ( 1 )
• 7 schematically a further development of the marker ( 1 ) in rotationally symmetrical form,
• 8th : schematically the marker off 7 with hidden edges,
• 9 schematically the marker from the 7 and 8th in the yz section plane,
• 10 : schematsch another training of the marker ( 1 ) in the sectional view through the xy plane,
• 11 schematically a sectional view of the marker 10 crooked about the Y-axis,
• 12 : schematically an axisymmetric RP-MR marker ( 1 )
• 13 : schematically the marker off 12 with hidden edges,
• 14 FIG. 2 schematically shows the marker with a sectional view through the xz plane, FIG.
• 15 : schematically another sectional view of the marker ( 1 ) through the yz plane
• 16 FIG. 1 schematically a further sectional view of the marker (FIG. 1 ) through the xy plane and
• 17 FIG. 2 schematically shows an obliquely cut view of the marker (FIG. 1 ).

2 schematically shows a marker ( 1 ) in isometric view for the universal instrument recording in the center, z. B. by means of adapter sleeves.

3 schematically shows the marker ( 1 ) out 2 with hidden edges ( 1' ).

4 schematically shows a sectional view of the marker ( 1 ) from the 2 and 3 in the Y Z -Level. The marker ( 1 ) has a bore ( 4 ) or tube with a respective final collar ( 5 ) and is for the universal recording of instruments, eg. B. by means of additional adapter sleeves suitable.

In doing so, the federal government ( 5 ) can also be used to connect other facilities. In the covenant ( 5 ) are cavities or caverns ( 2 ), which may for example be arranged in the form of a circumferential "double triangle".

5 time schematically another sectional view of the marker ( 1 ) from the 2 and 3 in the xy -Level.

6 schematically shows a further sectional view of the marker ( 1 ), wherein the sectional view around the y -Axis is cut rotated. The truncated marker cavity ( 4 ) is asymmetrically visible, analogous to the image plane, to recognize that the triangular shapes are mirrored around the triangle peaks unsymmetrical. In MRI he gives it an identification feature for an oblique orientation of the marker.

In 7 is schematically in isometric view a further embodiment of the marker ( 1 ) with a bunch ( 5 ) is shown in rotationally symmetrical form, wherein the marker for a universal instrument recording in its center z. B. is suitable by means of an adapter sleeve, not shown.

8th shows the marker 7 with hidden edges ( 1' ).

9 schematically shows the marker from the 7 and 8th in the yz section plane. Again, the marker ( 1 ) a hole ( 4 ) or tube with a respective final collar ( 5 ) and is for the universal recording of instruments, eg. B. by means of additional adapter sleeves suitable. In doing so, the federal government ( 5 ) can also be used to connect other facilities.

10 shows schematically the formation of the marker ( 1 ) from the 7 . 8th . 9 in the sectional view through the xy plane, wherein the opposite cone structures shown here can be used for the alignment of the marker. A rotation about the z-axis causes z. As the change in the diameter of the visible in the MRI cone cross section (circle).

In this case, either the marker in a static image plane, z. B. xz plane, or vice versa, the image plane in the static marker to be rotated. After the diameter of the visible cone cross-section is greatest, is due to the further rotation about the z-axis z. B. in the yz plane a cavity level visible, cf. 9 ,

The circumferentially distributed, cuboid-shaped cavities ( 2 ) are very thin, z. B. with a depth of 1 mm. They all only appear completely in the image plane, that is, with perfect square projections, if the marker is oriented in low angular tolerance perpendicular to the xy plane shown here.

11 schematically shows a sectional view of the marker 10 slanted around the y-axis. The cut marker cavities ( 2 ) are also asymmetrically visible here, z. B. the quadratic projections are only partially visible or missing completely, analogous to the image plane in the MRI and thus provide identification features for the alignment of the marker ( 1 ), which is then optimal as soon as the cutting plane is off 10 is reached.

The rotationally symmetrical design of the marker ( 1 ) allows the targeted distribution, even of large cavities or marker structures around a central axis around, with the axis of symmetry of the instrument, z. B. can match a biopsy needle. Conclusions on the position of the invisible in the MRI instrument can be done by determining the planes of symmetry, because these z. B. in the symmetry axis of the instrument.

12 schematically shows an axisymmetric marker ( 1 ), which has individual channels (K) for biopsy needles with diameters corresponding to the usual needle sizes and according to the entered scale in an isometric view.

13 shows the marker ( 1 ) out 12 with hidden edges ( 1' ). The axisymmetric design of the marker allows the placement of several holes or tubes, for each recording different instruments, on a plane.

In contrast to the two previously shown embodiments of the marker, there are so many crossing points of planes of symmetry through the Bohrungsmittelachsen as holes are available. The associated larger sizing of the marker can be useful for the precision of the marker alignment, because thin cavities located in the marker ends are only fully visible with higher alignment accuracy, see also analogy in 10 ,

14 schematically shows the marker 12 or 13 with a sectional view through the xz-plane, wherein the cavities or caverns ( 2 ) can also be expressed in the form of numbers (Zi) and letters or marks, for example in the form of triangles ( 2 ' ) and thus also allow direct orientation in MR imaging.

15 schematically shows a further sectional view of the marker ( 1 ) through the yz plane with cavities ( 2 ).

16 schematically shows a sectional view of the marker ( 1 ) through the xy plane, wherein the cavities or caverns can also be expressed in the form of numerals (Zi) and letters in analogy to 14 ,

17 schematically shows an obliquely cut view of the marker on all sides ( 1 ). All cut marker cavities are asymmetrically visible, analogous to the image plane in the MRI and thus provide identification features to the marker to be made.

Claims (10)

Marker (1) for the visualization of instruments and devices under MR imaging, wherein the marker (1) is formed from at least one plastic and wherein in the marker (1) at least one individually located cavity (2) with solid walls (3) is formed and enclosed by the plastic, which is at least partially filled with plastic, such that the plastic in the cavity (2) is in liquid consistency, wherein the filling of the cavities (2) and the walls (3) have the same plastic , Marker (1) after Claim 1 comprising a plurality of cavities (2), which, depending on their intended visibility in an MRI, are arranged relative to each other according to predetermined dimensions and positions, preferably rotationally symmetrical to an axis (z). Marker (1) after Claim 1 or 2 , wherein the material is a photosensitive, liquid plastic, which hardens under the influence of light of a certain wavelength. Marker (1) according to one of the preceding claims, wherein the material hardens by means of chemical reaction. Medical device comprising a marker (1) according to one of the preceding claims, wherein instruments can be attached and guided on or in this device. Method for producing a marker (1) for the visualization of instruments and devices under MR imaging according to one of Claims 1 - 4 comprising a generative manufacturing method comprising at least the following steps: a) individual design of the marker model with walls and at least one cavity, b) production of the marker according to the model specifications by building the walls and enclosing the cavity, the walls (3) be made of the same plastic, with which the cavities (2) are filled. Process for the preparation of a marker (1) according to Claim 6 comprising at least the following steps: a) providing a printing device according to a generative manufacturing principle for processing at least one starting material, b) providing an individually designable model geometry for forming the marker (1), wherein in the model geometry at least one cavity (2) is formed, in which the starting material after step a) can remain unprocessed, c) solidification of the starting material in the printing device along the model geometry. d) closing the cavity (2), preferably by the further construction of wall structures. Method according to Claim 6 or 7 , wherein the cavities are not completely closed to the outside. Method according to one of Claims 6 - 8th , characterized in that the material in the cavities can change its state of aggregation. Marker (1) according to one of the preceding Claims 1 - 4 , wherein the visible marker cavities (2) in the MR imaging are not formed as orientation-giving, but as surrounding structures, such that the walls (3) can be used for orientation.

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