WO2017157880A1 - Electromagnetic drivable inserts - Google Patents

Abstract

The present invention relates to magnetically activatable inserts. In order to provide improved activation of inserted implants, a drive threaded joint (1) for insertion in a body structure is provided. The drive threaded joint comprises a first part (2) provided as a thread-body for connection with a support structure, and a second part (3) provided as a drive-body for driving the first part. The thread-body has a thread (4) defining a screwing direction along a thread axis (6). The second part is mechanically connectable to the first part. The second part has a magnetic structure (7) such that a rotating movement of the second part around an axis is activatable by an appropriate magnetic field. The drive threaded joint is further arranged such that a torque energy created by said rotation of the second part is transferrable to the thread-body once the second part is rotationally mechanically connected to the first part, implying thus the driving of the thread-body.

Description

ELECTROMAGNETIC DRIVABLE INSERTS

FIELD OF THE INVENTION

The present invention relates to a drive threaded joint, a system for targeted magnetic activation of an inserted device and a method for activating a device inserted into a body structure.

BACKGROUND OF THE INVENTION

In medical interventional methods, medical devices are sometimes inserted in a body structure. For activating, for example bone screws, access has to be provided to be able to deliver the activation force, e.g. by a tool engaging with the screw. In order to deliver power, e.g. for interventional tasks and activating and deactivating functions of the device, cables or wires are used, for example as catheter tubes or similar. However, it has been shown that sometimes wires or cables are found to be not so convenient and may, for example, bother surgical steps. Further, the use of a magnetic field for power delivery is known. For example, the remote activation of an inserted screw via magnetic fields may be applied. However, it has been shown that only limited forces can be transferred by magnetic fields.

SUMMARY OF THE INVENTION

There may thus be a need to provide improved activation of inserted implants. The object of the present invention is solved by the subject-matter of the independent claims, wherein further embodiments are incorporated in the dependent claims. It should be noted that the following described aspects of the invention apply also for the drive threaded joint, the system for targeted magnetic activation of an inserted device and the method for activating a device inserted into a body structure.

According to the present invention, a drive threaded joint for insertion in a body structure is provided. The drive threaded joint comprises a first part provided as a thread-body for connection with a support structure, and a second part provided as a drive- body for driving the first part. The thread-body has a thread defining a screwing direction along a thread axis. The second part is mechanically connectable to the first part. The second part has a magnetic structure such that a rotating movement of the second part around an axis is activatable by an appropriate magnetic field. Further, the drive threaded joint is further arranged such that a torque energy created by said rotation of the second part is transferrable to the thread-body once the second part is rotationally mechanically connected to the first part, implying thus the driving of the thread-body.

This provides the effect that higher forces can be transferred, which facilitates turning screws in situations larger friction forces occur. The provision of a drive-body that can rotate freely at least over a certain angle allows to build up a momentum of force, which is then transferred by sudden engagement with the threaded part. In other words, one part is used to be accelerated by a magnetic field with a moving component, and one part is acting as the actual thread part to connect with a support structure. Thus, the drive threaded joint is incorporating a tool portion, i.e. the movable portion that is provided to build up the momentum of force.

The drive threaded joint can also be referred to as threaded joint or threaded joint device or threaded connecting device.

The thread-body is the part of the drive screw that functions as the screw connection, i.e. the part that can interact with a counter-part, for example a counter-thread or a material which engages with the thread of the thread-body and thus forms a counter-thread.

The torque moment of inertia is also referred to as angular momentum. By rotation of the second part, the torque moment of inertia can be generated. Thus, torque impulses can be generated in order to rotate the thread stepwise. Thus, higher friction forces, e.g. caused by bone structures with higher density, can be compensated.

The first state is also referred to as free-moving position; and the second state is referred to as engaged or force-transmitting position.

The second part is provided with a permanent magnetic structure, which, in interaction with a magnetic field, is causing a rotation of the second part in the first state.

The term "appropriate" relates to a magnetic field that is capable of inducing a rotation of the magnet, i.e. the second part.

The term "appropriate magnetic field" relates to a magnetic field sufficient to activate the magnetic structure of the drive-body such that the drive-body can rotate around its axis until reaching a torque sufficiently high to allow the transfer of this torque energy to the thread-body along the thread axis in the screwing direction according to the invention.

For example, a minimum "appropriate field" has at least some oscillation component perpendicular to the axis of rotation. The component has an amplitude of at least 0.1 ηιΤ/μο, but in an option above 1 mT/μο. The field may be provided below 100 mT/μο ίο ensure spatial selectivity to be achievable. Also

In an example, the magnetic field is rotating to act on the second part.

In another example, the magnetic field is provided with an oscillation in one direction to activate the rotating movement of the second part.

The term "rotationally mechanically" relates to rotation of a first member generating a kinetic and/or dynamic energy of this first member sufficiently high such that this energy can be at least partly mechanically transferred to a second element mechanically connected to the first member.

In an example, the drive-body has a magnetic structure and a movement of the second part is activatable by a targeted magnetic field with a moving component. In a first state, the drive-body is freely rotatably movable around the thread axis at least within an angular range, and, in a second state, the drive-body is connectable to the first part. Further, by rotation of the second part in the first state, a torque moment of inertia is achievable in the second part, which torque moment of inertia is transferrable to the thread-body in the second state for driving the thread-body.

In an example, the drive threaded joint is s drive screw inserted in a patient's body, for example for connection with a bone structure or another support structure inside the body. A first part is provided as a screw-body for connection with a support structure; and a second part is provided as a drive-body for driving the first part. The screw-body has an external thread defining a screwing direction along a thread axis; wherein the drive-body has a magnetic structure and a movement of the second part is activatable by a targeted magnetic field with a moving component. In a first state, the drive-body is freely rotatably movable around the thread axis at least within an angular range, and, in a second state, the drive-body is connectable to the first part. By rotation of the second part in the first state, a torque moment of inertia is achievable in the second part, which torque moment of inertia is transferrable to the screw-body in the second state for driving the screw-body, i.e. for moving the screw in relation to the thread of the support structure.

In another example, the drive threaded joint is a drive nut inserted in a patient's body, for example for connection with a screw part of a support structure inside the body. A first part is provided as a nut-body for connection with a screw part; and a second part is provided as a drive-body for driving the first part. The nut-body has an internal thread defining a screwing direction along a thread axis; wherein the drive-body has a magnetic structure and a movement of the second part is activatable by a targeted magnetic field with a moving component. In a first state, the drive-body is freely rotatably movable around the thread axis at least within an angular range, and, in a second state, the drive-body is connectable to the first part. By rotation of the second part in the first state, a torque moment of inertia is achievable in the second part, which torque moment of inertia is transferrable to the screw-body in the second state for driving the nut-body, i.e. for moving the nut along the thread of the screw.

The drive threaded joint can also be referred to as a micromachine.

According to an example, the drive threaded joint is a drive screw for insertion into a body structure. The first part is provided as a screw-body for connection with a support structure. Further, the screw-body has an external thread defining the screwing direction along a thread axis.

The screw-body is the part of the drive screw that functions as the screw connection, i.e. the part that can be screwed into a material, or that can interact with a bore thread, for example a counterpart in form of a nut.

By rotation of the second part in the first state, a torque moment of inertia is achievable in the second part, which torque moment of inertia is transferrable to the screw- body in the second state for driving the screw-body.

According to an example, the drive threaded joint is a drive but for insertion into a body structure. The first part is provided as a nut-body for connection with a support structure; and wherein the nut-body has an internal thread defining the screwing direction along a thread axis.

By rotation of the second part in the first state, a torque moment of inertia is achievable in the second part, which torque moment of inertia is transferrable to the nut-body in the second state for driving the nut-body.

According to an example, the drive threaded joint further comprises a guiding tube. The second part is movably hold in the guiding tube, in which the second part can be freely rotated and can also be freely translated in direction of the thread axis. The first part and the second part are provided with corresponding engagement interfaces to connect one to the other. Further, a translation of the second part in direction of the thread axis towards the first part brings the first part and the second part into engagement with each other to transfer the torque energy.

The second part is hold such that it can be positioned displaced to the first part such that the second part is freely rotating. Upon bringing the second part to sufficient rotation speed, the second part can be moved towards the first part for a mutual engagement. In an example, the second part is movably hold in a guiding tube, in which, in the first state, the second part is freely rotatable and is also freely translatable in direction of the thread axis. The first part and the second part are provided with corresponding

engagement interfaces. Further, a translation of the second part in direction of the thread axis towards the first part brings the first part and the second part into engagement with each other to transfer the torque moment of inertia.

In an example, the translation if the second part in relation to the first part is achieved by magnetic activation. In other words, the translation is provided by a respective control of the magnetic field.

The guiding tube may be provided as a sleeve structure. The guiding tube may be formed integrally by the first part, i.e. the screw-body or nut-body.

In another example, the second part is movably hold along a guide rod. A housing or envelope may be provided to protect surrounding tissue to be affected by the rotating second part.

According to an example, the corresponding engagement interfaces are provided as interfaces comprising at least one of the group of latches, protrusions and front- end gearing.

The latches can be provided with skewed or chamfered ends to facilitate the engaging procedures. The protrusions can be provided in combination with recesses for engagement by the protrusions. The front-end gearing can be provided as a saw tooth profile saw tooth.

According to an example, the first part and the second part comprise corresponding stop elements arranged to stop the rotation of the second part with respect to the first part when these stop elements are in abutment one to the other, allowing therefore the transfer of the rotation energy from the second part to the first part.

In an example, the second part is movably hold to the first part to be rotatable over a predetermined angular section. The predetermined angular section is defined by abutting of a delimiter at a pair of limit stops that allow free rotating movement between the limit stops, such that when the delimiter abuts one of the limit stops, the torque moment of inertia is transferrable.

The limit stops are also referred to as stopper. The delimiter can also be referred to as engaging link, or as engaging protrusion, or as engaging member.

The first state is the part of the free rotation of the second part. The second state is when the second part engages with the first part. A housing or envelope may be provided to protect surrounding tissue to be affected by the rotating second part.

According to an example, further comprising an energy storage, wherein the second part is connected to the energy storage. The drive threaded joint is further arranged such that the mechanical energy corresponding to the rotation of the second part in a first angular direction is transferrable to the energy storage as an activation energy. Further, the energy storage can release, upon activation, the stored activation energy as an activation force on the second part to cause a rotating movement of the second part in a second angular direction opposite the first angular direction to generate the torque. Preferably, the energy storage is a torsion spring element.

In an example, the activation is provided as magnetic activation. Alternatively, also other activation forces may be provided that are able to remotely activate, i.e. trigger the release of the energy storage.

In an example, the winding, i.e. the rotation of the second part in the winding direction, is provided in a first rotation speed, and the un- winding, i.e. the release in the unwinding direction, is provided in a second rotation speed. The first rotation speed is slower than the second rotation speed.

Thus, it's possible to transfer energy to the storage by a rather slow movement of the second part, which movement is caused by the targeted magnetic field with a moving component.

The connection of the second part to the energy storage is a load- or activation- force-transmitting connecting .

The winding up of e.g. a torsion spring element is provided by the magnetic field with the movement component. In an example, the triggering, i.e. the activation to set free the stored energy, is also provided by the magnetic field. The winding-up can take place in a slower speed, which facilitates the operation of the magnetic field. The movement caused by the spring can then be faster to achieve a high momentum.

In another example, the energy storage is provided by an elastic member, against which a force is acting when winding up the second part. Upon release, the elastic member causes the second part to rotate.

In other words, the movement energy provided by the magnetic field is stored and released by transferring the energy into angular momentum which is then used to generate the moment of a torque.

According to the invention, also a system for targeted magnetic activation of an inserted device is provided. The system comprises a magnetic field generator configured to generate a primary magnetic field with an arrangement resulting in a field free point or field free line where the fields cancel. The magnetic field generator is further configured to generate a displaceable secondary magnetic field to shift the position of the field free point and/or a mechanical movement of the magnetic field generator. The magnetic field generator is configured to displace the magnetic field to cause movement of a moving part of a determined one of a plurality of devices for insertion in a body, while, preferably, other devices of the plurality of devices remain in the same state.

According to an example, the magnetic field generator is configured to cause a targeted movement of the determined device for insertion and all other devices for insertion remain non-rotating. Preferably, the magnetic field generator comprises permanent magnets with N/S poles configuration on a movable support arm to perform a helical movement in order to create the rotating field to move the field free point.

According to an example, the magnetic field generator comprises a primary magnetic source for generation of the primary magnetic field. Further, the magnetic field generator comprises a secondary magnetic source for generation of the displaceable secondary magnetic field. Preferably, an X-ray imaging is provided and the primary magnetic source is provided by a magnetic system, and the secondary magnetic source is provided by a movable magnetic manipulator.

In an example, at least one drive threaded joint is provided to be activated by the system for targeted magnetic activation.

According to an example, at least one inserted device is provided as a drive threaded joint according to one of the examples above.

According to an example, at least one inserted device is provided as a radiation providing seed for use in radiotherapy. The seed comprises a seed core that is configured to generate radiation, a casing providing a cavity, and a movable insert which is guided inside the cavity. The seed core is attached to the movable insert. Further, the movable insert is configured as a magnetic insert, such that upon applying a magnetic field with a moving component, the insert is movable relative to the casing. The insert is movable between a first position and a second position such that the relative position or orientation of the insert with respect to the casing is changed from a first position or orientation to a second position or orientation. In the first position, the seed core is in a shielded arrangement within the casing, and in the second position, the seed core is in an exposed arrangement, such that in the second position, the seed provides more radiation than in the first position. In an example, the movable insert is configured to cause a movement between the first and the second position upon being moved relative to the casing.

In a further example, the insert is a screw insert with an outer thread. The screw insert has a magnetization component transverse to the screwing direction, such that upon applying a magnetic field with a rotational component, the screw insert is rotatable relative to the casing.

In a further example, the at least one device for insertion in a body is provided as an interventional device of at least one of the group of a biopsy needle, an interventional tool for manipulating tissue or bone structure, an ultrasound transducer head, and a drive screw. The interventional device comprises a corpus structure with an outer thread for interacting with surrounding portions of the body. Upon rotation of the corpus structure, the device is moving relative to the surrounding portions of the body.

According to an example, the system for targeted magnetic activation of an inserted device comprises an imaging system of at least one of the group of a magnetic particle imaging (MPI) system, a magnetic resonance imaging (MRI) system and an X- ray/CT imaging system.

According to the invention, also a method is provided for activating a drive threaded joint for insertion in a body structure. The method comprises the following steps: i) Providing a drive threaded joint with a first part provided as a thread-body for connection with a support structure; and a second part provided as a drive-body for driving the first part; the thread-body has a thread defining a screwing direction along a thread axis. Further, the second part is mechanically connectable to the first part. The second part has a magnetic structure such that a rotating movement of the second part around an axis is activatable by an appropriate magnetic field.

111) Generating a primary magnetic field with a field free point.

112) Moving the position of the field free point.

iii) Thereby causing rotating of the second part of the drive threaded joint by displacing the field free point; thus creating torque energy.

iv) Rotationally mechanically connecting the second part to the first part and thereby transferring the torque energy for driving of the thread-body.

According to an example, in step iv), for the mechanical connection, the second part is translated along the axis of ration in relation to the first part. The translation of the second part in direction of the thread axis towards the first part brings the first part and the second part into engagement with each other. The torque energy is transferred activating the drive threaded joint.

According to an example, the first and second part comprise corresponding stop elements arranged to stop the rotation of the second part with respect to the first part when these stop elements are in abutment one to the other. In step iv), the first part and the second part are abutting each other thus transferring at least a part of the rotation energy.

According to an example, in step iii), an opposite rotational movement is used for charging an energy storage to store energy to be released to cause a rotational movement to create torque energy. Further, in step iii), after a determined time, the stored energy is released to generate the rotational movement to create the torque energy.

According to an example, steps i) to iv) are implemented iteratively such that the thread-body is driven several successive times. In other words, in an example, a repetition is provided such that a "hammering" effect is achieved to support the screwing movement of the screw.

According to the invention, also a method is provided for activating a device inserted into a body structure. The method comprises the following steps: In a first step, a plurality of devices inserted in a body is provided. Each device comprises a movable part having a permanent magnet structure. In a first sub-step of a second step, a primary magnetic field with a field free point or field free line is generated. In a second sub-step of the second step, the position of the field free point is moved. In a third step, a movement of a movable part of a determined one of the plurality of the inserted devices is caused by displacing the field free point.

In an example, the term "activating" relates to activating a function of the device, such as activating and de-activating a radiation of a seed.

In another example, the tern "activating" relates to operating the device, e.g. moving the device, such as inserting a screw as an object. For example, the screw is operated for adjustment purposes.

According to an example, at least one of the inserted devices is a drive threaded joint according to one of the examples above. In step c) it is provided:

cl) causing movement of the second part of the drive threaded joint in the first state, wherein the movement is caused in the screwing direction; by rotation of the second part, a torque moment of inertia is achieved in the second part; and

c2) temporarily connecting the second part to the first part in the second state, causing to transfer the torque moment of inertia to the thread-body, thereby driving the thread-body. In an example, a method for activating a drive threaded joint for insertion in a body structure is provided. The method comprises the following steps:

i) generating a targeted magnetic field with a moving component; wherein a primary magnetic field with a field free point is generated, and the position of the field free point is moved; thereby causing movement of a second part of a drive threaded joint in a first state, which second part provided as a drive-body for driving a first part that is provided as a thread-body for connection with a support structure, wherein the thread-body has a thread defining a screwing direction along a thread axis; wherein the drive-body has a magnetic structure; and wherein the movement is caused in the screwing direction; and wherein, by rotation of the second part, a torque moment of inertia is achieved in the second part; and ii) temporarily connecting the second part to the first part in a second state, thereby transferring the torque moment of inertia to the thread-body thereby driving the thread-body.

According to the invention, also a computer program element for controlling a drive threaded joint according to one of the above-mentioned examples is provided, which, when being executed by a processing unit, is adapted to perform the method steps of one of the examples described above.

According to the invention, also a computer program element for controlling a system for targeted magnetic activation according to one of the above-mentioned examples is provided, which, when being executed by a processing unit, is adapted to perform the method steps of one of the examples described above.

According to the invention, also a computer readable medium is provided that is having stored the program element of the examples described above.

In an example, a radiation providing seed for use in radiotherapy is provided. The seed comprises a seed core that is configured to generate radiation, a casing providing a cavity, and a movable insert, which is guided inside the cavity. The seed core is attached to the movable insert. The movable insert is configured as a magnetic insert, such that upon applying a magnetic field with a moving component, the insert is movable relative to the casing. The insert is movable between a first position and a second position. In the first position, the seed core is in a shielded arrangement within the casing, and in the second position, the seed core is in an exposed arrangement, such that in the second position, the seed provides more radiation than in the first position.

This provides the effect that the seed can be activated by a magnetic field, and can also be deactivated by also applying the magnetic field respectively. The term "movable relative to the casing" relates to a relative movement between the insert and the casing. In one example, the insert moves and the casing remains; in another example, the casing moves and the insert remains; in a further example, the insert and the casing move. Hence, a mutual relative movement is provided, i.e. the insert is movable in relation to the casing.

The "moving component" of the magnetic field relates to a magnetic field with a field character or magnetic field distribution that is spatially changing over time in the sense that the magnetic field properties are spatially moved, for example in a two- or three- dimensional manner.

In an example, the cavity is formed by the casing. In another example, the cavity is formed by an inner container of vessel arranged inside the casing.

In an example, a magnetic field is provided with a field free point or field free line where two opposing magnetic fields cancel. Further, it is provided that the position of the field free point is moving, hence resulting in the moving component. The term "component" relates to a parameter or property of the field and not to a component such as a piece of equipment. The movement of the field free point / line may be achieved by a spatial adaption of the magnetic field. In another example, a primary magnetic field and a secondary magnetic field are provided and the spatial arrangement of the secondary field is moved.

In an example, the moving component is a mostly homogeneous component with a flux density magnitude of less than 50 mT, preferably less than 10 mT. It can have a relatively complex temporal shape, e.g. in three (sub-) components.

In an example, the moving component is a rotating component, i.e. the location of the field free point / line is moving in a rotational manner.

For example, the moving component comprises of several part-components. In on example, the rotating movement comprises several part-rotation components, e.g. quarter rotational movements in contrariwise manner.

In another example, the moving component is a translating component, i.e. the location of the field free point / line is moving in a translational manner.

In another example, the moving component is a combination of a translating and a rotating component, i.e. the location of the field free point / line is moving in a combined movement manner.

For example, an AC field or translationally moving gradient field is applied in helical mechanical guides.

In an example, a magnetic source is configured to create a magnetic field adapted to apply a mechanical attraction or repulsion force to the magnetic seed along a longitudinal axis or along a helical path, e.g. the longitudinal axis.

In an example, the "moving magnetic field", i.e. the moving component of the magnetic field, allows that the mechanical switch of the radiation is controlled directly by an applied magnetic force or torque. As a consequence, it does not require intermediary mechanism, i.e. like an elastic element (spring) or a heating element to free the radiation. This results in increased reliability and avoids the need of high frequency for heating and aspects related to applying heat. Further, compactness is optimized, without further activation means like a spring and also a wireless device.

In an example, the movable insert is configured to cause a movement between the first and the second position upon being moved relative to the casing.

In an example, the insert is a screw insert with an outer thread. The screw insert has a magnetization component transverse to the screwing direction, such that upon applying a magnetic field with a rotational component, the screw insert is rotatable relative, e.g. in relation to the casing.

In another example, the magnetic field is having a translationally moving gradient field, and the device, i.e. the seed, is provided with helical mechanical guiding means to allow a "helical movement" caused by the translational movement in interaction with the guiding means.

As an effect, it is provided that the insert provides the movement between the first and the second position due to the movement of the insert itself relative to the casing, which, due to guidance leads to a transversal displacement of the screw insert inside the cavity.

As an effect in the rotational example with the screw insert, it is provided that the screw insert provides the movement between the first and the second position due to the rotating movement of the screw itself, which, due to the thread, leads to a transversal displacement of the screw insert inside the cavity.

However, it is also provided that another type of insert is provided that is caused to move relative, e.g. in relation, to the casing such that a movement between the two positions is provided.

In an example, the position or orientation of the insert relative to the casing is provided to be moving, i.e. the insert and/or the casing are moving. Instead of the thread also other means are provided such as guidance for helical movement, such as pin/groove connection along a helical path. Such guidance can also be provided to be along a zigzag line or wavelike curved line to allow a movement of the insert to result in a translation movement component.

In an example, the seed core comprises radioactive material that generates radioactive radiation. The casing in a first part is provided with a radiation shielding material forming a shielding part of the casing. In a second part the casing has low Z material. In the first position, the seed core is arranged within the shielding part, and in the second position, the seed core is arranged outside the shielding part.

This provides the effect that a switchable seed is provided.

In an example, the casing is provided with a shield in a first part providing the shielding part. Preferably, the shield is also forming a part of the thread on the inside of a housing envelope. Further preferably, the casing is provided with a low Z liner also forming a non-shielding part of the tread on the inside of the housing envelope. Preferably, the low Z liner is also forming a part of the thread on the inside of a housing envelope.

In an example, the casing is provided as a spherical case, and a spherical inlet is rotatably arranged inside the spherical case. The spherical inlet is forming the cavity, e.g. comprising the inner thread or other guiding means for the insert. The spherical inlet further comprises a first part provided with a radiation shielding material forming a shielding part- sphere, and a second part provided with a low Z material. In the first position, the seed core is arranged within the shielding part-sphere, and in the second position, the seed core is arranged outside the shielding part-sphere.

In an example, the casing comprises an inner vessel that forms the cavity. The inner vessel is at least partly filled with a melting material that has a melting point slightly above body temperature. The seed core is movable within the inner vessel upon applying the magnetic field with the moving component when the melting material is in a melting state upon applying thermal energy to the melting material.

In an example, the casing comprises an inner casing that provides the cavity. The visco-plastic fluid filling is arranged inside the casing, the casing forming an outer casing. The inner casing is arranged movably within the visco-plastic fluid filling. Preferably, a tuning arrangement is provided attached to the inner casing, and the tuning arrangement is magnetically activatable to adjust the spatial orientation of the inner casing in relation to the outer casing.

In an example, the seed core comprises radioactive material emitting alpha radiation. The casing, at a first portion, is provided with the inner thread and, at a second portion, with a target material for the alpha radiation to generate neutrons comprising radiation, such that, in the first position, the seed core is arranged distanced to the target material, and, in the second position, the seed core is arranged closer to the target material.

In an example, a locking mechanism for the screw insert is provided to prevent unwanted rotation. Preferably, the locking mechanism comprises one of the group of permanent magnets in the seeds, mechanical guiding elements, mechanical stops and visco- plastic fluid.

According to an aspect, a two-part screw or nut is provided. The two parts are interconnected in a way that cannot be separated from each other, but in a way that they can be rotated relative to each other over at least a certain range of motion. By engaging the two parts, a momentum can be transferred from part to the other. One part has the thread porting and the other part is the tool part that is used for generating the force to operate the thread part. The tool part is used to be moved by activation with a magnetic field and the movement thus generates a momentum due to the accelerated weight of the tool part. Upon sudden engagement, the momentum is transferred to the thread part. Thus, a screw or nut is provided that allows the generation of higher operating forces, which are provided as impulse forces for driving the screw or nut. In an example, the operation forces are provided for tightening the screw or nut. In a further example, the operation forces are provided for loosening the screw or nut. In a still further example, the operation forces are provided for both loosening and tightening the screw or nut. According to an aspect, selectively controlling identical micromachines, such as inserted devices as screws or seeds, using magnetic fields is provided. For example, this can be used supporting effective therapy for cancer and other diseases. One example of an inserted device to be operated by a targeted magnetic field are screws, such as bone screws or screws used for adjusting implanted prostheses. One example of an inserted device to be operated by a targeted magnetic field are seeds that can actively be controlled in their emission of for example nuclear radiation.

A magnetic actuation technology is provided that can be used to selectively energize individual micromachines within a 'swarm' of such devices injected into the human body. Being able to activate individual drug or radioisotope loaded micromachines, improves options for more effective treatment for difficult to treat diseases, such as tumors that are located close to or embedded in critical organs. Micromachines are injected into a patient's bloodstream or tissue to target specific disease sites. Instead of activating a plurality of these micromachines at the same time, improved control is provided by selecting individual micromachines in a swarm and activating these individually, such as turning on or off, i.e. an accurately targeted and modulated operation is provided. This concept achieves the required level of control by using applied magnetic fields to both select and energize an individual micromachine, even one that is surrounded by several identical devices. Energizing the selected micromachine is achieved by externally generating a rotating magnetic field that causes a tiny magnet in the device to rotate - similar to rotating a small bar magnet over a compass and watching the compass needle spin.

However, if this were the only applied field, the magnets in all those micromachines aligned with the rotating field would also rotate. To stop this from happening, a stronger static magnetic field is superimposed on the rotating field to overcome the rotating field's effect - equivalent to placing a strong magnet next to the compass to lock the compass needle in a fixed position. Put simply, if a micromachine is influenced by the static field, its magnet cannot rotate. If it is not influenced by the static field, its magnet can rotate. The key to energizing a single micromachine within a swarm of devices is to reduce the static field to zero, creating a so-called 'Field Free Point', at the precise location of the selected

micromachine. No longer locked in place by the static field, the magnet in this micromachine can then be rotated by the rotating field. Creating all the necessary magnetic fields, including those needed to generate a movable Field Free Point, can be achieved by driving suitable currents through three orthogonally arranged electromagnets. Selecting and energizing a specific micromachine is then only dependent on knowing its precise location, which can be determined by conventional imaging techniques such as X-ray CT or ultrasound scans, and then moving the Field Free Point to that location. Mechanical rotation of the selected micromachine 's magnet can be used in a number of ways. For example, it can be converted to linear motion either by driving a leadscrew, or by corkscrewing an entire helically- structured micromachine forwards or backwards.

One clinical application are controllable micromachines containing radioactive isotopes to treat cancer tumors via brachytherapy. These are also referred to as seeds. After being injected via a suitable catheter into the region of the tumor, the isotope pellet in these micromachines can be magnetically driven in and out of a radio-opaque protective shell to modulate the radiation dose, with selective activation of individual micromachines used to profile the spatial distribution of the radiation to match the shape of the tumor.

Another clinical application are controllable micromachines in form of screws that can be operated without the need of an external tool. After being inserted in an object, e.g. a patient's body, these micromachines can be magnetically driven, i.e. moved along their threaded connection with a support structure.

These and other aspects of the present invention will become apparent from and be elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will be described in the following with reference to the following drawings:

Fig. 1A shows a schematic illustration of an example of a drive threaded joint in a first state; and Fig. IB shows the drive threaded joint in a second state.

Fig. 2 shows another example of a drive threaded joint with a screw-body.

Fig. 3 shows a further example of a drive threaded joint with a nut-body. Fig. 4 shows a cross-section of an example of a drive threaded joint with a guide sleeve for guiding the drive-body.

Fig. 5 shows another example of a drive-body rotatable over a predetermined angular section.

Fig. 6 shows a schematic illustration of a system for targeted magnetic activation of an inserted device.

Fig. 7 shows another example of such system.

Fig. 8 shows basic steps of an example of a method for activating a device inserted into a body structure.

Figs. 9A to 9D show examples of an interventional device that can be used as described above.

Fig. 10 shows a schematic illustration of an example of a radiation providing seed for use in radiotherapy.

Fig. 11 shows a further example of the radiation providing seed.

Fig. 12 shows a still further example of a radiation providing seed.

Fig. 13 shows a further schematic cross-section through a radiation providing seed.

Fig. 14A and 14B show a further example of a radiation providing seed, wherein Fig. 14A shows a longitudinal cross-section and Fig. 14B shows a transverse cross- section.

Fig. 15 shows a further functional illustration of an example of a radiation providing seed.

Fig. 16 shows another example of a radiation providing seed.

Fig. 17 shows a still further example of a radiation providing seed.

Fig. 18 shows a further example of a radiation providing seed that can be activated by the screwing mechanism.

Fig. 19 and Fig. 20 show examples of a locking mechanism of a radiation providing seed.

Fig. 21 shows another example of a radiation providing seed.

Fig. 22 shows a still further example of a radiation providing seed.

Fig. 23 shows a neutron generation version of the radiation providing seed.

Fig. 24 shows a further schematic illustration of the neutron radiation providing seed.

Fig. 25 and 26 show further functional diagrams of the activated magnetic field.

DETAILED DESCRIPTION OF EMBODIMENTS

Fig. 1 schematically shows a perspective view of a drive threaded joint 1 for insertion in a body structure. In order to illustrate the different parts, the drawing is shown in an exploded view. The drive threaded joint 1 comprises a first part 2 provided as a thread- body for connection with a support structure, like a bone structure or another implant part or portion (not shown). Further, a second part 3 is provided as a drive-body for driving the first part 2. The thread-body 2 has a thread 4 that can be rotated, as indicated with arrow 5a. The thread 4 is defining thus a screwing direction along a thread axis 6. The second part is mechanically connectable to the first part. The second part has a magnetic structure 7, as also indicated with "N" and "S" for the different poles of such magnetic structure, such that a rotating movement of the second part around an axis is activatable by an appropriate magnetic field. The drive threaded joint is further arranged such that the torque energy created by said rotation of the second part is transferrable to the thread-body once the second part is rotationally mechanically connected to the first part, implying thus the driving of the thread-body.

In an example, the second part can be moved by translation, as indicated by a further arrow 5b, between the first state and the second state. The second part, i.e. the part that is moved by activation of the magnetic field can thus be brought to speed in the first state, as shown in Fig. 1 A. Upon translation, e.g. towards the first part, the second part can be brought into engagement with the first part, which is the second state, which state is shown in Fig. IB.

In an example, shown in Fig. 2, the drive threaded joint is a drive screw 500 for insertion into a body structure. The first part is provided as a screw-body 502 for connection with a support structure. The screw-body has an external thread 504 defining a screwing direction 506 along a thread axis 508.

In an example, shown in Fig. 3, the drive threaded joint is a drive screw 510 for insertion into a body structure; and wherein the first part is provided as a nut-body 512 for connection with a support structure; wherein the nut-body has an internal thread 514 defining the screwing direction along the thread axis.

In an example, shown in Fig. 4 in a longitudinal cross-section, the example further comprises a guiding tube 520, and the second part is movably hold in the guiding tube

520, in which the second part can be freely rotated and can also be freely translated in a direction of the thread axis, as indicated with an arrow 522. The first part and the second part are provided with corresponding engagement interfaces 524 to connect one to the other. A translation 526 of the second part in direction of the thread axis towards the first part brings the first part and the second part into engagement with each other to transfer the energy, i.e. an impact resulting from the torque moment of inertia.

In an example, not further shown, the corresponding engagement interfaces are provided as interfaces comprising at least one of the group of latches, protrusions and front-end gearing.

In another example, shown in Fig. 5a and 5b, the second part is movably hold to the first part to be rotatable over a predetermined angular section 530, in this case for nearly up to 360°. The predetermined angular section is defined by abutting of a delimiter 532 at at least one limit stop 534 that allows free rotating movement in between, such that when the delimiter abuts of the limit stop, the torque moment of inertia is transferable.

The first state is thus the state where the second part, e.g. in Figs. 5A and 5B the outer ring surrounding the screw part, can move freely in a rotating manner. The second state is thus the state where the second part engages with the first part, i.e. when the delimiter abuts the limit stop.

As indicated, the screw is provided with an outer ring part 536 and a screw part 538. The ring part may be hold such that rotation is possible, which rotation is only limited by the engagement of the protrusions provided on the inner side of the ring and on the upper part of the screw.

Fig. 5A shows a perspective view and Fig. 5B shows a top view. The magnetic properties of the movable upper part in form of the ring are indicated by "N" and "S".

In an example, not further shown, the second part is connected to an energy storage. The drive threaded joint is further arranged such that the mechanical energy is transferrable to the energy storage as an activation energy. Upon activation, the energy storage can release the stored activation energy as an activation force on the second part to cause a rotating movement of the second part in a second angular direction opposite the first angular direction to generate the torque.

In an example, the energy storage is a torsion spring element.

In Fig. 6, a system 200 for targeted magnetic activation of an inserted device is provided. The system comprises a magnetic field generator 202 configured to generate a primary magnetic field with an arrangement resulting in a field free point where the fields cancel. A displaceable secondary magnetic field is provided to shift the position of the field free point and/or a mechanical movement of the magnetic field generator. The magnetic field generator is configured to displace the magnetic field to cause movement of a moving part of a determined one of a plurality of devices for insertion in a body. Preferably, other devices of the plurality of devices remain in the same state.

An X-ray C-arm system may be fitted with a magnet assembly to operate the seed.

It is noted that in addition, also an imaging system, such as an X-ray imaging system, is shown as an option. Further, a patient support 206 is indicated and a patient 208 with a seed region 210 is illustrated. The X-ray imaging may comprise an X-ray tube 212 and an X-ray detector 214.

In an example, the primary magnetic field is a static magnetic field.

In another example, the secondary magnetic field is homogenous.

In an example, a plurality of devices is provided, wherein each device comprises a rotating part. The rotating part has a thread structure to cause a movement of the rotating part in direction of the axis of rotation upon rotation of the rotating part. The magnetic field generator is configured to cause rotation of a rotating part of the determined one of the plurality of devices. The rotating part has a permanent magnet structure with a north-south pole configuration that is arranged along a line transverse to an axis of rotation of the device.

In an example, the devices are seeds as described above.

In another example, the devices are interventional tools, as further described below.

The term "remain non-rotating" refers to the rotation of the rotating part.

In an example, only the determined device rotates, while all other devices are not rotating. For example, the magnetic field generator has two opposing north poles. As a further magnetic arrangement, a single-sided arrangement is provided.

The addition of a mainly homogeneous field moves the field free point (FFP). However, a mechanical movement of the arrangement moves the FFP as well.

In an example of a labyrinth- like cavity, along which the screw-insert is moved, it is possible that more than one screw rotates, while only one finds the way from one side to the other as the angle needs to be precisely aligned.

In an example, the magnetic field generator is configured to cause a targeted movement of the determined device for insertion and all other devices for insertion remain non-rotating. Preferably, the magnetic field generator comprises permanent magnets with N/S poles configuration on a movable support arm to perform a helical movement in order to move the field free point actually without a rotating field.

For example, the rotating field is provided plus a movement transversal to the rotation axis.

In an example, the magnetic field generator is configured to cause a targeted rotation of the rotating part of the determined device for insertion and all other devices for insertion remain non-rotating.

For example, as an imaging system, an MPI system is provided that has the capability to produce the primary and the secondary field.

For example, the system comprises an imaging system of at least one of the group of a magnetic particle imaging (MPI) system, a magnetic resonance imaging system

(MRI) and an X-ray/CT imaging system.

For example, Fig. 7 shows an X-ray imaging system 216 and a patient table

218. Further, a robotic arm structure 220 is provided carrying a magnetic assembly 220 to achieve the rotation of inserted devices or seeds, i.e. the rotation of the rotatable parts of these inserts or seeds.

According to an example, not further shown, the magnetic field generator comprises a primary magnetic source for generation of the primary magnetic field and a secondary magnetic source for generation of the displaceable secondary magnetic field.

Preferably, an X-ray imaging is provided and the primary magnetic source is provided by a magnetic system, and the secondary magnetic source is provided by a movable magnetic manipulator, for example a robotic arm.

For example, the magnetic system consists of a large permanent or electro magnet. In addition, as magnetic manipulator, some additional devices are provided to do the relatively fast movement, e.g. a coil system or a small portion of the field generator that moves.

The inserted device may be a temporarily implanted device (see below).

The term "transverse" relates to an orientation approximately perpendicular, i.e. for example, +/- 20° deviating from 90°, preferably a smaller deviation from 90°, or 90° = perpendicular.

The magnetic imaging system may be provided, for example, as a magnetic particle imaging system or as a magnetic resonance imaging system.

In an example, the movable magnetic manipulator is a robot with a magnetic structure attached to a movable arm.

In an example, a cylinder-shaped rod contains a permanent magnetic material. An externally enforced rotating magnetic field around the rod involves the mechanical rotation of the rod. Upon engaging with the screw part, due to the existence of a thread on the outside of the screw part, the rotational movement is translated into a longitudinal movement along the axis of the device.

Due to the sudden engagement, forces are available for this screwing mechanism that overcome frictions.

The sudden engagement is based on physically separating the thread from the magnetic rod, and keeping them aligned along the same axis. This alignment may be performed inside e.g. a joint sleeve, or by the rod being partly located inside the thread. The thread does not necessarily comprise magnetic material and can be e.g. in plastic material.

In an option, also the threaded part comprises magnetic material such that a further activation force is provided.

The two-part screw or nut, i.e. the two-part threaded device, works as follows: In a 1^st step, an energy uptake is provided. The rotation of an externally generated magnetic field acts only on the rod at increasingly higher speed because there is no friction between the threads on e.g. the bone to be overcome. An angular momentum is built up accordingly.

In a 2^nd step, the rapidly rotating rod is then drawn longitudinally along the axis by external magnetic forces in the direction of the other part. This translational movement ends with an abrupt contact between the rod and the thread, creating a sort of "hammer-" effect with the angular moment of the rod being suddenly transferred to the thread. As an example, pins on the end portions of the rod and of the thread are provided, which leads to a short but strong torque.

By this separation between the energy uptake and the energy release, the torque is significantly increased.

The provision of higher resulting operating forces is provided for example for screw in implants such as endoprostheses (knee joints, back bone / spinal, etc.) that contain various screwing mechanisms for fixation to other parts of the prostheses or towards bone material. In order to fasten these screws during an operation, tendons, muscles and generally other tissue need less to be temporarily pushed aside or even removed by surgery to provide space for the tools to access the screws' heads, since the screw can now be operated without direct access by a toll's head. The need for tissue dislocation that would lead to additional prolongation in the healing process after the operation is thus reduced.

In other words, it is provided a screw that can be turned without a tooling that requires direct spatial contact to the screw. This simplifies the operation technique and avoids unnecessary surgery.

Due to the momentum generation, the forces for this screwing mechanism are increased such that it is possible to overcome the friction between e.g. the external thread on the outside of the screw and the internal thread on the inside of whatever other part (threaded hole, bone, etc.). This is of advantage in particular when minimizing the size of the screw. Also, when the friction is increased in cases like screws in implants as endoprostheses due to body liquids and other tissue penetrating the devices, the integrated momentum generation of the two-part screw is of advantage.

As mentioned above, the torque is increased by separating the energy uptake process from the energy release process. Besides fixation of screw, it is also possible to adjust screws in existing implants without the need for an operation, since the screws can be activated remotely by the magnetic field.

In an example, not further shown, a method for activating a drive threaded joint for insertion in a body structure is provided. The method comprises the following steps: i) Providing a drive threaded joint with a first part provided as a thread-body for connection with a support structure; and a second part provided as a drive-body for driving the first part. The thread-body has a thread defining a screwing direction along a thread axis; the second part is mechanically connectable to the first part; the second part has a magnetic structure such that a rotating movement of the second part around an axis is activatable by an appropriate magnetic field.

111) Generating a primary magnetic field with a field free point.

112) Moving the position of the field free point.

iii) Thereby causing rotating of the second part of the drive threaded joint by displacing the field free point; thus creating torque energy.

iv) Rotationally mechanically connecting the second part to the first part and thereby transferring the torque energy for driving of the thread-body.

In an example, in step iv), for the mechanical connection, the second part is translated along the axis of ration in relation to the first part. The translation of the second part in direction of the thread axis towards the first part brings the first part and the second part into engagement with each other; and the torque energy is transferred activating drive threaded joints.

In an example, the first and second part comprise corresponding stop elements 532, 534 arranged to stop the rotation of the second part with respect to the first part when these stop elements are in abutment one to the other; and wherein in step iv), the first part and the second part are abutting each other thus transferring at least a part of the rotation energy.

In an example, in step iii), an opposite rotational movement is used for charging an energy storage to store energy to be released to cause a rotational movement to create torque energy. In a determined time, the stored energy is released to generate the rotational movement to create the torque energy.

Fig. 8 shows a method 300 for activating a device inserted into a body structure. The following steps are provided. In a first step 302, also referred to as step a), a plurality of devices inserted in a body is provided. Each device comprises a movable part having a permanent magnetic structure. In a second step, as a first sub-step 304, also referred to as step bl), a primary magnetic field is generated with a field free point. In a second sub- step 306, also referred to as step b2), the position of the field free point is moved. In a third step 308, also referred to as step c), the movement of a movable part of a determined one of the plurality of the inserted devices is caused by displacing the field free point.

In an example, each device comprises a movable part having a permanent magnet structure with a north-south pole configuration that is arranged along a line transverse to an axis of rotation of the device. The rotating part has a thread structure to cause a movement of the rotating part in direction of the axis of rotation upon rotation of the rotating part. In step c), the rotation of a rotating part of a determined one of the plurality of the inserted devices is caused by displacing the field free point. The movable part is having a thread structure to cause a movement of the rotating part in direction of the axis of rotation upon rotation of the rotating part.

According to an example, at least one device is provided as a radiation providing seed according to one of the above-mentioned examples. According a further option, the at least one device for insertion in a body is provided as an interventional device of at least one of the group of a biopsy needle, an interventional tool for manipulating tissue or bone structure, an ultrasound transducer head, and a drive screw. The interventional device comprises a corpus structure with an outer thread for interacting with surrounding portions of the body. Upon rotation of the corpus structure, the device is moving relative to the surrounding portions of the body.

For example, Fig. 9A shows a screw 402 with a biopsy needle 404. Further, a ring magnet 406 is provided, in addition to a bar magnet 408. Still further, a needle tip 410 is indicated.

Fig. 9B shows an MPI driven multi-tool, for example having a saw structure

412 on one side of the screw. Still further, also a ring magnet 406 and a bar magnet 408 are provided.

Fig. 9C shows an MPI driven ultrasound transducer with a screw structure 414, a ring magnet 416, and a coil structure 418. Still further, on a tip, a transducer 420 is provided.

Still further, Fig. 9D shows a drive screw 422 which is having an axle 424 and a magnet structure 426 with a tappet 428. Still further, inside a screw body 430, stoppers 432 are provided.

Referring to Fig. 9A, it is noted that the screw can be operated via a rotating magnetic field about a user-defined axis to propagate and fix the device to a target location. A gradient field is used to push a needle through the screw into the target tissue, which may be used to stabilize the rotation axis, or for a biopsy, drug delivery or similar intervention. The linear field orientation may be altered to orient the screw into the desired direction, i.e. the device can be moved on bended paths.

Referring to Fig. 9B, oscillating fields can be used to drive for example a saw or other cutting devices as shown.

Fig. 9C relates to rotational magnetic forces and electromagnetic energy transmission. For example, a screw is driven to the desired location and orientation, and an ultrasonic transducer is supplied with energy via a pick-up coil. The amount of transmittable power is in the order of Watts, which is sufficient for e.g. an ablation procedure. The transducer may be mounted in an asymmetric fashion as shown in Fig. 9C, or as a multielement transducer, including capacitive micromachined ultrasonic transducers which may be used for focusing. The ultrasonic may also be generated directly using a magnetostrictive device and an MPI drive field. Referring to Fig. 9D, it is noted that large angular momentum can be applied using an impulse drive screw as shown. A pivot mounted magnet with a tappet is pre-wound by appropriately one half turn until stopped by the magnet. After the field has rotated further 180°, or its polarity is inverted, the magnet performs a fast rotation until reaching a stopper, and large angular momentum are delivered via the angular momentum of the magnet. Thus, in a continuously rotating field, the device repetitively delivers strong torque impulses. This may be used to drive a screw into or out of very solid tissue, bone or other materials, or to fixate, adjust or lose an implant.

In an example, the MPI magnetic fields to operate a device include gradient fields to induce linear forces into a specific direction, homogeneous fields to orient a device into a specific direction, rotating fields to induce torque, oscillating fields to induce oscillatory movement or energy transmission, or a superposition of the aforementioned fields, for instance in order to induce a torque about a specific access in the space of the inner bore.

Radiation therapy can be used as a type of cancer therapy. For example, in brachytherapy, a radiation source is brought in close proximity to the target tissue. Radiation sources may utilize radioactive material or some sort of X-ray sources. One option is the permanent implantation of radioactive seeds. These seeds may remain in the patient and the radiation dose rate simply decays according to the used isotope. However, according to an example it is provided to change the apparent dose rate by mechanical means. For example, low energy X-ray and/or gamma-ray emitters are provided. The radiation of those can be shielded by a thin layer of high Z material. Therefore, the radiation can be modulated by moving the radiation source relative to an interacting material like a gold shield. Since in brachytherapy, usually about 100 seeds are placed, in an example, the seeds can be addressed individually by magnetic fields to operate the seed.

In one option, alternating magnetic fields are used, which tune each seed to a specific frequency.

In another option, the absence of a static field is provided, which can also be used for imaging such as in "Magnetic particle imaging" (MPI). If the north poles of two identical magnets face each other, the fields in the middle cancel, but the field magnitude increases from this point towards all directions. The point, where the fields cancel is called the "Field Free Point" (FFP). Adding a small homogeneous field shifts the position of the field free point and the field strength at the original FFP becomes non-zero. In the imaging case, this effect was used to saturate soft magnetic material positioned not at the FFP and use an AC field to generated harmonics at the FFP. Magnetic material that is not located at the position of the original FFP remains in the state of saturation and therefore does not generate harmonics. The same effect can be used to manipulate the material. In this type of field (let's call it "selection field"), soft magnetic material will be pushed away from the field free point. With this, a switchable seed may be constructed.

Fig. 10 shows a radiation providing seed 10 for use in radiotherapy. The seed

10 comprising a seed core 12 that is configured to generate radiation. Further, a casing 14 is provided that provides a cavity 16. For example, the cavity is formed by the casing. In an option, an inner container or vessel is provided to form the cavity. A movable insert 18 is guided inside the cavity. The seed core 12 is attached to the movable insert 18. The movable insert is configured as a magnetic insert such that upon applying a magnetic field with a moving component, the insert 18 is movable relative to the casing. The insert 18 is movable between a first position PI (indicated with a hashed line) and a second position P2 (also indicated with a hashed line). In the first position PI, the seed core 12 is in a shielded arrangement within the casing 14, and in the second position P2, the seed core 12 is in an exposed arrangement such that in the second position P2, the seed 10 provides more radiation than in the first position PI .

In an example, the insert is guided inside the casing, e.g. the insert with a smooth outer surface enabling to be moved inside the casing, and some stops inside the casing to retain the insert inside the casing when not magnetically activated are provided.

Fig. 11 shows an example, where the insert 18 is a screw insert 20 with an outer thread 22. The screw insert 20 has a magnetization component 24 transverse to the screwing direction, such that, upon applying a magnetic field with a rotational component, the screw insert 20 is rotatable relative to the casing 14.

In an example, the magnetization is e.g. 45° oriented to the screwing direction, i.e. a magnetization having a magnetization component parallel and a magnetization component perpendicular to the screwing direction.

The screwing direction is relating to the axis in which the screw is moving upon rotation.

In an example, the casing is non-magnetized. In a further example, the casing is also magnetized.

For example, the magnetic field is moving. A moving magnetic field relates to an example where the magnetic field generating apparatus is rotated such that the resulting magnetic field is also rotating.

The screw/thread arrangement can also be provided as helical guiding mechanism. The mechanism provides that upon rotation of an inner part inside a casing, the inner part moves relative to the casing in a moving direction, e.g. a longitudinal direction. In other words, the magnetic field with the moving component results a rotation of the insert. Due to being guided by the guiding mechanism, the rotation results in a movement component along the longitudinal direction. Hence, the guiding mechanism is acting as a thread in this respect, but does not necessarily have to provide the same tight guidance and connection.

Due to the screwing mechanism, the seed is a switchable seed, i.e. a seed that can be activated or deactivated, or simply said, a seed that can be switched on and off.

In an example, the casing is comprising an inner thread forming the cavity. For example, the outer thread of the screw insert is engaging with the inner thread of the casing.

In a further example, a viscous fluid is arranged inside the cavity, and the outer thread of the screw insert is interacting with the viscous fluid such that upon rotation of the insert, the screw insert is moving relative to the casing.

According to an option, also shown in Fig. 11, the seed core 12 comprises radioactive material that generates radioactive radiation. The casing 14 is provided with a radiation shielding material in a first part 25 forming a shielded part of the casing. In a second part 26, the casing 14 is provided with a low Z material. In the first position PI, the seed core 12 is arranged within the shielding part and in the second position P2, the seed core is arranged outside the shielding part. In Fig. 11, an intermediate state is shown, where the seed core 12 has just left the shielding part of the casing and entered the second part.

For example, the casing is made out of titanium and thus provides a titanium case. The second part may be provided by a low Z polymer thread and liner. The first part 25 providing the shielding part may be made as a gold shield and thread.

In an example, the seed core is attached to the screw insert as a longitudinally

(i.e. in screwing direction) extending protrusion, and the casing is provided with a receptacle at one end such that in the second position, the seed core is resting inside the receptacle.

As mentioned above, as an option, the casing is provided with a shield in a first part providing the shielding part. Preferably, the shield is also forming a part of the thread on the inside of a housing envelope, as shown in Fig. 11 and further figures. As a further option, the casing is provided with a low Z liner also forming a non-shielding part of the thread on the inside of the housing envelope. Preferably, the low Z liner is also forming a part of the thread on the inside of a housing envelope, as indicated in Fig. 11.

In an example, instead of a low Z polymer, other low Z materials like graphite or boron nitride are provided. They also provide the effect of low radiation damage.

In an example, the shield is a gold shield. In another example, other high Z materials are used for the shield.

In an example, shown in Fig. 12, a band 28 of soft magnetic material is provided along the length of the casing. For example, the band is provided in a helical shape, or as a straight line or in form of several portions or fragments.

In another example, a helical high Z material is provided alternatively or in addition to the helically shaped band of Fig. 12 to provide a directionality of the radiation if the seed remains in an intermediate state.

In an example, there are at least two different states, in which the seed core is arranged outside the shielding part. In other words, the second position comprises two sub- states. For example, two sub-states with different directions for the radiation are provided, e.g. with a helical structure.

The term "soft" magnetic material, or magnetically soft material, relates to materials that can be magnetized, but which materials have no (or little, i.e. iHc < 1 mT/μΟ) tendency to stay magnetized. For example, paramagnetic materials are provided. In another example, a material with small coercive force is provided.

The term "hard" magnetic material, or magnetically hard material, relates to materials that stay magnetized.

In an example, in absence of a magnetic field (except the magnetic field of the earth), or at fields with a value in a lower range, high coercive force is needed.

The term "permanent magnet" relates to a magnetized material creating its own permanent, i.e. persistent magnetic field. For materials that can be magnetized, and which are also attracted to a magnet, are called ferromagnetic, and include among iron, nickel, and cobalt also e.g. alloys of rare earth materials.

For example, permanent magnets are made from hard ferromagnetic materials such as alnico and ferrite, for which a special processing is provided, e.g. in a powerful magnetic field during manufacture in order to align their internal microcrystalline structure. This processing results in that they are rather "hard" to demagnetize. For the demagnetization of a saturated magnet, a magnetic field must be applied with a strength above a threshold that depends on the coercivity of the respective material. Simply said, "hard" materials have high a coercivity and "soft" materials have a low coercivity.

The term "along the length" relates to the direction, in which the screw insert moves inside the cavity. In an example, the soft magnetic band 28 is provided with different magnetic spectral properties along its length in order to provide for determination of the switching state of the seed.

In an example, inside the cavity, a lubricating fluid 30 is provided, as indicated in Fig. 12 as an option also applicable for other examples shown in different figures.

Fig. 13 shows a further option, according to which the casing is provided as a spherical case 32, i.e. an outer casing. A spherical inlet 34, i.e. an inner casing, is arranged inside the spherical case 32 in a movable manner, e.g. the inlet can be swiveled or rotated. This provides the effect that an orientation of the radiation is possible, since the inlet can be oriented by applying respective magnetic field components, e.g. in addition to the moving components for activating the insert like the screw.

The spherical inlet 34 is forming the cavity, e.g. comprising the inner thread, indicated with reference numeral 36, forming the cavity. The spherical inlet comprises a first part 38 provided with a radiation shielding material forming a shielding part-sphere, and a second part 40 provided with a low Z material. In the first position PI, the seed core is arranged within the shielding part-sphere, and in the second position P2, the seed core is arranged outside the shielding part-sphere.

For supporting the spherical insert inside the spherical case, a bearing fluid 42 is arranged between the spherical insert and the casing.

In an example, inside the cavity, a lubricating fluid is provided as an alpha radiation shielding liquid.

Before referring to further examples, some general aspects relating to the present invention are described in the following.

The radiation providing seeds described above can be used, for example, in radiotherapy as a type of cancer therapy. This is also known as brachytherapy, where a radiation source is brought in close proximity to a target tissue. The above described seeds are suitable for example for permanent implantation of radioactive seeds that can remain in the patient and the radiation dose rate can be controlled by activating, i.e. moving the radiation seed core inside the casing. The radiation can be modulated by moving the radiation source relative to an interacting material like a gold shield.

A screwing mechanism is used to activate the radiotherapy seed. For example, on the screw, the radioactive material (¹²⁵I or ¹⁰³Pd) is placed. In the off-state, the screw rests in a compartment shielded by a few 10 μιη gold or similar material. In the initiated state, the screw is turned by a magnetic field that rotates perpendicular to the thread axis. For this, the screw is at least partly composed of a permanent magnet material. When the screw reaches the unshielded compartment, the seed is in the on-state. Soft magnetic material at both ends of the thread may be provided for the following purposes. The first purpose is to hold the screw in its position, when no rotating field is applied. The second one is to localize the seed in the, for example, magnetic particle imaging system. The third purpose is to determine the position of the screw within the seed to determine the switching state. The system can replace traditional brachytherapy seeds keeping the external dimensions exactly the same. When miniaturized, alternative delivery modes, like the transarterial route, may be applied.

The intended outer dimensions are for example, 0.8 mm in diameter and 4.5 mm in length. The screw is magnetized mainly perpendicular to the long axis of the device. One way of achieving this magnetization is to use permanent magnetic material, like FeNdB attached to the screw, e.g. in a hole in the middle of the screw. Further, also a semi-hard magnetic material may be used. Still further, also soft magnetic material can be used, e.g. as a layer within the screw in the paper or drawing plane, i.e. the same geometry as in the case of semi- hard material as in Fig. 11. The radioactive material is attached on the screw. The radioactive material is usually either ¹²⁵I or ¹⁰³Pd and the apparent activity is typically in the range of 1E7 to 1E8 Becquerel. The activity may vary for special applications. The shield of the radiation in the non-activated state consists of two parts. First, the gold shield, or any other high Z high density material, and the lubricating fluid which contains intermediate to high Z elements like P, S, CI for still rather low Z or I for relatively high Z. For a so to speak "complete" shielding of the radiation, the thickness of the gold shield may be a few 10 μιη, e.g. 50 μιη. The 1/10 value layer gold for ¹²⁵I is about 35 μιη. So for 50 μιη of gold, switching ratios are in the order of 1 to 20. The fluid inside the cavity blocks radiation to the side, when not activated. The recess in the plastic part of the thread, indicated with reference numeral 44 in Fig. 11, allows for a low absorption path in the case of activation. The whole seal is enclosed in an end welded titanium tube to provide a biocompatible surface and a hermetic seal for the radiation source.

Fig. 14A shows an example where the screwing mechanism is not achieved by thread in thread, but by a thread in a viscous fluid 46.

In other words, a screw is having an outer thread and the inner side of the casing enclosing the cavity is provided without a thread, but the fluid in between provides a holding effect such that when the screw insert is rotated, a helical relative movement is achieved. The fluid hence provides a sort of guiding connection due to its viscosity.

In another example, instead of a thread, a helical groove is provided that results in a helical guidance of the insert.

In addition to Fig. 14A, an option is provided according to which the thread is on the other surface, i.e. the inner surface of the casing enclosing the cavity, and the seed has no thread. In Fig. 14A, a gold shield 48 is provided with a cavity, inside which the high viscosity high density fluid is provided. The seed may be provided with a structural element 50 as a magnetic screw with radioactive material in a thread 52. Further, a low Z polymer or metal 54 is provided, also forming a further portion of the cavity. Still further, soft magnetic cross elements 56 are arranged.

Fig. 14B shows a transverse cross-section of the example shown in Fig. 14A. An inner circle 58 indicates the cavity and the soft magnetic cross elements 56 are also shown inside the gold shield 48.

In an option (not shown in detail), the casing comprises an inner vessel that forms the cavity. The inner vessel is at least partly filled with a melting material that has a melting point slightly above body temperature. The seed core is movable within the inner vessel upon applying the magnetic field with the moving component when the melting material is in a melting state upon applying thermal energy to the melting material.

In Fig. 15, a further example is shown that may be provided having an outer diameter of 0.8 mm and 4.5 mm in length as a titanium rod. An inner vessel 60 is placed with a diameter of about 0.5 mm. This vessel is filled with a material 62 having a melting point slightly above body temperature. In this vessel, a sphere 64, containing radioactive material (¹²⁵I) and a magnetically semi-hard rod 66 is placed in the sphere 64. On the right side, a gold shield 68 is applied with suitable thickness to block the photons from the radioactive material to a sufficient degree. Further, between the inner vessel, or inner hull, thermo insulation material 70 may be provided as an option.

In Fig. 16, a further example is described, according to which the radioactive seed is similar to that shown in Fig. 15. Except for a light decrease in the size of the gold shield in the right-hand side and a new design of the radioactive sphere. The movable sphere consists of a thin radioactive plate 72 that is backed by a radiopaque gold layer 74. The sphere is completed by a radio-transparent material 76 like a polymer. The magnetic material for heating and movement of the sphere is augmented by a small fraction of permanent magnetic material 78 to introduce a preferred orientation.

Fig. 17 shows a further example of the seed as an augmented version of the seed in Fig. 16. The seed comprises two directional radiation sources that are located in two compartments of the inner vessel. The compartments are separated by a radiation shield 80 and contain materials with slightly different melting points. For example, in the left part of the cavity, a lower melting point material 82 is provided, and on the left side, the cavity is provided with a higher melting point material 84.

In Fig. 18, a further example of a seed is shown. This seed is activated by a screwing mechanism. Inside a titanium hull 86 with radiation shield 88 on one side, a polymer material is inserted and a thread is cut into the material. Inside the thread, a radioactive screw is inserted. The radioactivity is preferably at the cylindrical surface of the screw and a shield prevents the radiation from escaping the outer gold shield by paths through the screw. In the screw body, a permanent magnetic material is inserted with a magnetization perpendicular to the through axis.

Fig. 19 shows a further example of the seed with the screwing mechanism of Fig. 18. However, the screwing mechanism is fitted with a locking mechanism. The locking is achieved in Fig. 19 by two soft magnetic strips 90, one for the off position in the right-hand side, and one for the on position on the left-hand side. As the seed is drawn in the off position, only this soft magnetic sheet is magnetized.

In Fig. 20, an example is provided where a thin magnetic rod 92 is placed at the side of the seed to generate a homogeneous bias field.

In Fig. 21, a seed mechanism suitable for further miniaturization is shown. The radioactive and magnetic screw 94 is held in place by a Bingham fluid (or other type of visco-plastic fluid) 96 that need a minimum shear force to flow. There is no inner thread provided. The screw propels through the fluid due to rotation. The screw can travel between two containers. One container is radiopaque, the other transparent. The path between the containers is narrow and may exhibit some blocking structures 98 so that only a suitable local magnetic field sequence moves the screw between the containers. Further, the radioactive screw 94 is provided with a permanent magnet 99.

In an example, the casing comprises an inner casing that provides the cavity. Further, a visco-plastic fluid filling is arranged inside the casing, the casing forming an outer casing. The inner casing is arranged movably within the visco-plastic fluid filling. In an option, a tuning arrangement is provided attached to the inner casing. The tuning

arrangement is magnetically activatable to adjust the spatial orientation of the inner casing in relation to the outer casing.

In Fig. 22, in addition to the example shown in Fig. 21, a directional version of the device of Fig. 21 is shown. A spherical shell 100 is provided with a visco-plastic fluid filling 102 and further, magnetic tuning forks 104 are added. Instead of forks, also other tuning means are provided.

When operated, the tuning forks or others reduce the viscosity within the sphere and an external magnetic field can apply a torque on the tuning forks to point the radiation into the desired direction. The tuning forks are operated by a high frequency magnetic field.

According to an example, shown in Figs. 23 and 24, the seed core comprises radioactive material emitting alpha radiation. At a first portion, the casing is provided with the inner thread. At a second portion, a target material 106 is provided for the alpha radiation to generate neutrons comprising radiation such that in the first position, the seed core is arranged distanced to the target material, and in the second position, the seed core is arranged closer to the target material. For example, the case is a titanium case with a titanium thread. Further, a polonium 210 alpha emitter is provided, indicating with reference numeral 108. Still further, the emitter is attached to the magnetic screw 110. A lubricating fluid 112 is provided that may also act as an alpha shield. In the left-hand side, beryllium or boron target 106 is provided.

In an example, the seed core contacts the target material in the second position.

The radiation is provided as neutrons comprising radiation.

In an example, the target is fixed relative to the seed structure, whereas the source is moveable relative to the seed structure.

In an example, inside the cavity, a lubricating fluid is provided as an alpha radiation shielding liquid.

Fig. 24 shows an example, where an alpha emitter like polonium is used as the radiation source on the screw. For example, a polonium thread 114 is provided. The screw body is made of some relatively arbitrary engineering material and may contain a permanent magnet 116 to operate the screw. On one part of the casing, beryllium is plated, for example as an inner thread 118. If the alpha emitter is in contact with the beryllium, neutrons are produced.

As a further option, in Fig. 24, also some soft magnetic lock elements 120 are provided at the end faces.

According to a further example, not further shown, a locking mechanism for the screw insert is provided to prevent unwanted rotation. Preferably, the locking mechanism comprises one of the group of permanent magnets in the seeds and visco-plastic fluid.

In a further example, markers are provided to verify the switching state of the seed under imaging guidance, such as X-ray markers for X-ray imaging or MPI markers for MPI imaging.

In Fig. 25, a schematic illustration is shown for activating a particular one of a number of magnetically activatable screws. A primary magnetic field is provided with an arrangement resulting in a field free point 120 where fields cancel. A displaceable secondary magnetic field is provided to shift the position of the field free point, for example along a circulating movement path 122. Whereas such rotation results in a rotation 124 of a first seed 126, the effect on the neighboring seed 128 is only a swiveling motion 130. Hence, it is possible to achieve rotation for a targeted screw, whereas neighboring screws remain un- rotated.

Fig. 26 describes further the separation in the case of an access separation of the seeds. Other than in Fig. 25, the seeds are separated in their direction of rotation. If the field free point (FFP) rotates around the upper seed by moving from the drawn position in the paper plane, then to the left of the upper seed, out of the paper pane (in the direction of the viewer) to the right of the seed, passing the seed in the front, and back again to the paper plane, the magnet in the upper seed will rotate. However, the same torque, is applied to the lower seed. This seed will not rotate, as there is an additional torque indicated by the force arrows denoted with F. Due to this torque, the friction of the magnet in the bearing is increased to a level, that blocks the rotation.

In Fig. 18, a device, i.e. a seed is illustrated that operates purely mechanically.

The device consists of a thread in e.g. a plastic material inside the protective titanium hull. In the OFF position, the radioactive screw rests in the rightmost position. To avoid that radiation leaks out, the radioactive material is at the outmost position of the screw, e.g. in the thread and the screw body shields the radiation. This shielding can be accomplished by a special gold shield or by choosing the right material for the screw body e.g. silver which also has favorable radiochemical properties for radioactive iodine. Inside the screw body, a permanent magnetic material (e.g. Fei₄Nd₂B) is inserted with its magnetization perpendicular to the screw axis. The radiation is switched on, if the screw is moved to the left. One example for operating the screw is to apply a homogeneous magnetic field that rotates being always perpendicular to the screw axis. In this case the screw rotates without any additional magnetic torques or forces. To selectively operate the screw, on top of the rotating field, the selection field is added with the field free point (FFP) placed on the screw position. As at the FFP position, the field is zero, nothing changes for the screw and it rotates as illustrated in Figs. 25 and 26. In the combined field, the FFP is no more at the position of the screw, but rotates around the screw. Concerning a screw located at a distance from the position of the FFP of the selection field, for the sake of simplicity, it is only considered the situation where the field component at the seed position due to the selection field is perpendicular to the seed axis. If the field amplitude is higher than the amplitude of the rotating field, the total field at the seed position does not cover all directions. This means it only oscillates around a direction and does no more rotate. Therefore, the screw only oscillates and does not rotate. In the example of the FFP movement, the FFP does no more rotate around the seed and therefore no rotation in the seed occurs as shown in Figs. 25 and 26. Hence, the selection of a seed in the plane perpendicular to the axis depends on if the PPF moves around the screw or not. The selection mechanism in screw direction relies on a different principle and is also depicted in Figs. 25 and 26. Referring to a pure rotational field without the selection field, a field in screw direction is added. Independent of the strength of the added field, this results in the same radial torque on the screw as before. What changes is the torque on an axis perpendicular to the screw direction. This torque induces a canting of the screw and increases the torque needed for the rotation. This effect depends on length, surface properties and lubrication of the screw.

In an example, the operation does not start in a flux density below 2 mT, to avoid activating the screwing mechanism by every-day magnetic fields. As an option, a shear thinning lubricant is provided. The shear thinning effect is known from e.g. tooth paste, non- dripping dye and foods like ketchup. These fluids only flow, if enough shear force is applied. A different way to implement a locking mechanism is to add permanent magnets or soft magnetic material and hold the screw by the magnetic forces. This is illustrated in Figs. 19 and 20. In Fig. 19, the soft magnetic approach is illustrated. A thin and long strip of soft magnetic material is attached to the lids of the seed. The dimension of the strip in up-down direction is much longer than in the direction orthogonal to the paper plane. Therefore, magnetic anisotropy is generated. This means, the screw is locked in an orientation that is parallel to the strip as long as it is close enough to the ON or OFF position. In Fig. 20, the locking is achieved by a thin rod of permanent magnetic material. This material generates a fairly homogeneous field at all screw positions, and can therefore lock it in any desired position. This may be used to achieve a limited directionality of the seed. One option is to have an additional absorber in the left part of the seed e.g. a helical gold foil that describes one full loop. Depending on the position of the screw, the shadow of the gold foil has different directions and may be used to avoid critical tissue. A different approach for the directionality would be a permanent magnetic rod with a magnetization that varies in a helical way. This would change the orientation of the locked screw according to the position of the locking. If the screw is radiopaque and is provided with a radioactive surface only in part, the radiation direction can also be altered.

In order to provide delivery of seeds as trans-arterial delivery by a catheter procedure, the seeds are provided with a small diameter. For example, a diameter of 0.2 mm is provided. Considering the shielding point of view, this is achieved by ¹⁰³Pd sources, where the shielding thickness is only 30 μιη giving rise to 60μιη diameter penalty. For the 30 keV isotopes, a good (to 1 %) shielding gives rise to a diameter penalty of 200 μιη for gold. Here, a more efficient absorber may be desired. With platinum, the diameter penalty can be reduced to 170 μιη and with uranium to 130 μιη. So depleted uranium should be considered as a shielding material given the small total amount of it within all seeds in the patient. The total uranium mass for about 200 seeds would be in the order of 10 mg. The radiation would be rather negligible with a total activity of 200 seeds of less than 0.2 Bq. Furthermore, the alpha particles are shielded by the uranium itself and the necessary protective layer. Some of the rare gammas and the betas of the daughter nuclei (^234Th and ^234mPa) will reach the tissue resulting in a lifetime radiation dose well below 10 μGray. For very small seeds, the size of the radioactive material becomes significant, too. Current high activity Palladium seeds have an activity of 74 MBq (2 mCi) while the Iodide seeds have usually less than 37 MBq (1 mCi). With theoretical specific activity of 2800 TBq/g (75 kCi/g) for ¹⁰³Pd and 640 TBq/g (17 kCi/g), a cube of desired activity has a side length of 13 μιη assuming metallic palladium and 27 μιη assuming silver iodide. Therefore, seeds with diameters of roughly 100 μιη with Palladium are provided. The iodine seeds would require a little larger volume, but 200μιη diameter are provided in an example.

In Fig. 21, a seed is proposed, that can have a size almost as mall as the theoretical limit derived above. The seed is having two containers between which the radioactive material can travel. Only one container is transparent for the radiation. To avoid accidental travel of the radioactive material, the passage is narrow and has kinks and protrusions to allow only changing the containers, if the applied magnetic field is suitable just for this seed in this position and angle. To avoid mechanical vibrations, which are present in the patient due to his movement, to eventually move the screw between the containers, a fluid filling the device is provided having a special property. The fluid behaves like a solid for low shear stress and becomes liquid above a certain threshold. Such fluids are called visco-plastic fluids or "Bingham fluids" with the most common example being toothpaste. The fluid should also contain medium or high Z elements to attenuate radiation going through the connecting path and thereby reaching tissue. The whole seed may need to be covered by some protective layer e.g. a thin gold film that may be deposited also on the titanium part.

To determine approximate shear stress, a simple model with employing an infinitely long cylinder with radius r and average magnetization M may be used. In an external flux density B, the shear stress for the rotational movement \sigma_r is:

\sigma_r = Yfrac{r^A2 \pi 1 M B} { r 2 r \pi 1} = \frac{l } {2} M B wherein 1 being the "length" of the cylinder assumed to be large compared to the radius, so the ends of the cylinder can be neglected. As seen from the formula, the radius of the device cancels in the formula. Therefore, the rotational shear stress remains constant when scaling the device. Assuming M = 0.13 TAmu_0 A/m i.e. 10% permanent magnet content and an actuation flux density field of 1 mT, the shear stress is about 50 Pa.

In comparison, the average shear stress due to translation \sigma_t may be estimated as:

\sigma_t = Yfrac{r^A2 \pi 1 M G} {2 r \pi 1} = \frac{l } {2} M G r wherein G is the gradient of the flux density. In this case, the radius does not cancel so smaller devices exhibit less stress. Assuming a gradient of 1 T/m and a radius of 20 μιη, the shear stress is 1 Pa. This is much lower than in the rotational case. Therefore, it is impossible to (accidentally) operate the device using gradients. To determine, if the device is safe in case of vibrations the shear stress due to acceleration may be estimated by:

\sigma_a = \frac {r^A2 \pi 1 a YDelta \rho} {2 r \pi 1} = \frac { 1 } {2} r a YDelta \rho where a is the acceleration and YDelta \rho the difference in density. Assuming $a$ to be 9.81 m/s^A2 and YDelta Yrho to be about 5000 kg/m^A3, the shear stress is about 0.5 Pa.

As a proper visco-plastic fluid is a very efficient mechanism to avoid accidental actuation of the seed, the only purpose of the kinks and protrusions is to avoid the actuation of the wrong seed while using the gradient and rotating field to actuate one other. Therefore, the kinks may be rather small, much smaller than in the drawing, resulting in a diameter closer to the theoretical limit.

The miniaturized seed has no ability to direct the radiation, yet. The approach using a melting effect is no more technically feasible for this size, as thermal insulation is becoming very difficult and a sufficient temperature rise is no more expected. But the visco- plastic effect may also be used to address a seed as shown in Fig. 22. The miniature radioactive seed is now encapsulated in a sphere filled with a visco-plastic fluid. The yield stress of the fluid needs to be high enough that in expected magnetic fields, especially those applied to operate the other seeds, no rotation is observed. Rotation is only possible, if the seed oscillates thereby generating a very high shear stress. The oscillation may be generated by some tuning-fork device which is attached to the seeds. The tuning fork is made from a ferromagnetic material and resonant to the HF frequency applied or some harmonics of it. By magnetizing the tines in the same direction, they repel each other and by repeating the process using the HF magnetic field, the oscillating force is generated. The tuning forks can be used to apply the magnetic torque on the seed. Basically, the seed will orient in the direction of the applied magnetic field with some deviation due to unbalanced gravitational forces. As the direction should not be changed unintentionally, the total amount of magnetic material and the anisotropy should not be too high. The tuning fork approach is only one possibility. The system may also work with other devices that produce a torque in an alternating magnetic field. E.g. a magnet sphere in a Newtonian high viscosity fluid could be attached to the seed. If magnetic fields vary slowly, no torque is transmitted to the seed. In a fast rotating magnetic field, the torque is transmitted through the viscous coupling and the seed is turned. It is even possible to use focused ultrasound to selectively thin the visco- plastic fluid in the sphere and only a small permanent magnet is attached to the inter structure to turn the seed in the desired direction.

In order to be able to provide neutron radiation that has a different biological effect than photon radiation, small neutron sources are provided.

As an alpha emitter to generate an exceedingly low amount of gammas to count as neutron source, ²¹⁰Po is provided as an isotope with only 12 ppm of 803 keV photons being emitted for each alpha particle emitted. As neutrons have at least 10 times the biological effect than photons and the average energy of the neutrons is 4.5 MeV, the radiation effect due to photons is less than 2 % of the radiation damage due to neutrons. Moreover, the photons' energy is distributed over a much larger volume and a significant fraction of the photons may leave the patient altogether. Unfortunately, with a half-life of 138 days ²¹⁰Po does not seem to be useful for permanent implants as either a very low dose rate has to be chooses or an unsafe high dose has to be delivered.

With the magnetically switchable seeds, even a high dose rate does not have to be maintained until the radiation decayed.

The implementation of such a seed is very similar to the seeds shown so far except there is no way to direct the radiation in any way. The radiation source has to be replaced with polonium and the gold shield has to be replaced with beryllium. As the mean free path of alpha particles in a liquid is only about 10 μιη, the fluid filled variants are less suitable for the purpose, but as a thick shielding is not required, the seed can still be quite small.

In Fig. 24, a proposed neutron seed is sketched. It is very similar to the seed proposed in Fig. 20. The radioactivity is deposited on the screw thread as a thin layer of polonium or a polonium compound. It needs to be thinner than the free path of the alpha particles. Therefore, in one example, the thickness is in the order of 1 μιη or less. Some of the thread in the hull is covered by beryllium. The thickness of the beryllium layer does not need to be large as the alpha particles are stopped within the first 30 μιη. Accounting for the threshold energy of the reaction, 20 μιη beryllium is provided. Other than in the case of the photon emitters, here it is possible to inverse the position if beryllium and polonium which may me a little simpler to manufacture. The seed may be provided with a stopping mechanism as shown above.

In an example, the radiation effect (dose rate) of a photon seed R_p is compared with the radiation effect of the neutron seed R_n for the same activity a. The radiation effect of the photon seed is:

R_p = a * \eta_ {escape-photon} * E_ {photon} * W_ {photon} where \eta_ {escape} is the efficiency of photon escape from the seed assumed to be 0.5 and W_ {photon} is the relative biological effectiveness (RBE) of photons which is 1. E_ {photon} is the average photon energy which is 28 keV for ¹²⁵I. In the neutron case the dose rate is:

R_n = a * \eta_ {escape-neutron} * \eta_{production_neutron} * E_ {neutron}

* W_ {neutron}

where \eta_{production_neutron} is the production efficiency of neutrons and W_ {neutron} the RBE of 4.5 MeV neutrons which is about 10. E_ {neutron} is the average neutron energy of the Po-Be source and about 4.5 MeV. \eta_ {escape-neutron} is the escape probability of neutrons out of the seed and very close to 1. The theoretical efficiency of neutron production being 77ppm but we cannot expect to have this value in the switchable seed geometry, as only half of the neutrons travel into the right direction. Therefore, an efficiency of 38 ppm is assumed. In total, the dose rate ratio for the same activity is:

\frac{R_n} {R_p} = \frac{\eta_ {escape-neutron} * \eta_{production_neutron}

* E_ {neutron} * W_ {neutron} } {\eta_ {escape-photon} * E_ {photon} * W_ {photon} } \approx 0.12

So for the same activity about 12% the dose rate with neutrons is provided. This means, instead of 37 MBq (1 mCi) for an ¹²⁵I seed, 300 MBq (8 mCi) for a Po-Bi seed are provided. Assuming the theoretical specific activity of 1.66el4 Bq/g (4490 Ci/g) and a density of 9196 kg/m³, the needed polonium volume is 2e-13 m³ or a cube with 58 μιη side length. Assuming a screw with a diameter of 0.4 mm (total seed diameter 0.5 mm) and a screw length of 0.4 mm (total seed length of 1 mm), it is provided a layer thickness of 0.5 μιη even without taking the enlarged surface due to the thread into account. Shrinking the device could be accomplished by further enlarging the surface area e.g. by a higher aspect ratio thread or by using the frontal face of the screw, too.

Operating the screw may need a precise alignment of fields, while the patient may move; or other events disturb the operation of the screw. Therefore, a feedback mechanism is provided to check if the operation of the seed works. One option is to check with a Geiger counter the chance of activity while operating a screw. However, this gives only confidence that some operation happened, but does not tell which seed. Using a collimated radiation detector like an Anger camera improves the situation somewhat, but does not indicate where the seeds in off state are. Still such a device might be useful to locate seeds in on state that migrated far away from the implantation site. In an example, for operating the seeds, the position and orientation is provided with high accuracy. For example, imaging modalities are provided to guide the magnetic field. The modalities are Ultrasound, MRI, CT, X-ray and MPI.

Ultrasound is a very versatile imaging technique. In an example, special markers, like resonators are provided to detect the state of the seed.

MRI is an excellent imaging method especially in terms of soft tissue contrast. The seeds could be identified by their susceptibility artifact and, if the artifact is small enough, it could be precisely determined which seed should be operated as the surrounding tissue may be identified. In an example, the magnetic field is ramped down, to provide field cycling MRI.

CT is also a method to image the seeds and identify the tissue they are in, and CT can resolve the internal structure of (at least) the larger seeds thereby identifying their switching state.

Simple projection X-ray may also solve the problems of CT. As the shape and size of the seeds is known, only two projections are needed to determine spatial position. The high-resolution detector allows determining the internal structure of the seeds including the smaller designs. By collimating the X-ray field of view to not much more than the seed size, it is feasible to image a seed repeatedly without prohibitive high dose. Additionally, C-arm systems provide enough space to apply a magnetic field generator simultaneously. At least for the very small (trans-arterial) seeds, a very high resolution system is desired with a small focal spot diameter a small (<100 μιη) detector pixels. A very small but high resolution detector may be added to a conventional detector, as only a small field of view is needed. The small beam width may allow using the detector without anti-scatter grid (or maybe just a tube around the detector) to increase X-ray photon efficiency and resolution. In Fig. 6, a sketch of a permanent magnet system within an X-ray system is shown. Clearly there is enough space for both components still leaving a considerable angle accessible for X-ray imaging. This is needed for a determination of all seed properties. In this image, the geometric magnification of an X-ray system is used to maximize the resolution, which is critical for proper assessment of the seeds.

MPI systems inherently have the ability to operate the seeds. For example, the seeds in Figs. 19 and 20 incorporate soft magnetic material that would make detectable signal in MPI allowing determining the location of the seed. They also allow determining the switching state. If the screw is near the soft magnetic locking device, there will be an offset field. Therefore, the position would be determined incorrectly by MPI. The deviation of the localization depends on the gradient strength. The two locking soft magnetic materials may also differ in their spectral response e.g. by having different hysteresis. Hence, it is possible to determine at which end of the seed the screw rests. If the soft magnetic locks exhibit different directions of anisotropy, it is also possible to determine the direction and rotation of the seed. Therefore, all relevant parameters concerning the seed can be determined. The surrounding tissue may be imaged by MPI or by using the scanner in MRI mode if available.

The field generator is provided for at least three things. First it has to provide a sufficient gradient strength to address the seeds individually. Second, it has to change fast enough to switch the seeds in a reasonable time and third, only for the thermal seeds, it has to provide a HF field with sufficient high amplitude and frequency.

To estimate the needed gradient strength, it is determined at what distance the seeds shall be switched individually and at which flux density they should start moving. Seeds should be rarely closer than 5 mm to each other and if they are closer, they may be switched simultaneously. So the desires minimum separation is about 5 mm. The minimum field to operate is determined by the field at which the seeds shall definitely not operate, i.e. the minimum field for rotation. Around magnetic equipment, like MRI scanners, the line of 0.5 mT flux density is marked as potential hazardous area for people with implants. Setting the threshold 4 times as high, the minimum flux density is estimated to be 2 mT. The ratio of the two values leads to a minimum gradient of 0.4 T/m. For a field free point, the gradient in one direction is double the value of the other direction. This leads to a minimum gradient in the strong direction of 0.8 T/m. It is also possible to operate the seed in a higher field strength as long as the precision of the minimum operating field is 2 mT. E.g. the seeds operate at a minimum of 4 mT with a spread of 3 to 5 mT. Such a field can be generated using permanent magnets. For example, an assembly of two opposing cylindrical permanent magnets with a diameter of 20 cm and a length of 25 cm each separated by 40 cm generates 1 T/m in the center assuming a magnetization of the permanent magnets of 1.3 Τ/μ₀. The mass of the assembly would be about 125 kg. An electromagnet with the same performance has typically roughly the same size and maybe a little heavier. The width of a patient is typically less than 30 cm. Therefore, the FFP can be moved by 10 cm with this assembly. To switch seeds outside this field of operation, in the case of permanent magnets, at least one pole shoe has to be changed. Full patient coverage may be reached with 2 to 3 permanent magnet assemblies.

The speed of rotation of the screws determines the speed of the whole procedure. Switching all seeds should be performed within half an hour. There are roughly 80 seeds. Assuming a thread diameter of 0.5 mm, 4 mm length and 0.2 diameters movement per turn, 40 turns for each seed is needed. In total 3200 turns are needed. So, about 2 turns per second is the minimum goal. Such a speed can be realized by pure mechanical means as the radius of the movement of the magnet assembly is only about 5 mm. The flux density chance is 4*2mT/0.5s = 16 mT/s, i.e. orders of magnitude below the threshold for nerve stimulation of about 20 T/s.

The last point, the coils for generating the HF have been described in the context of MPI. Basically resonant coils made from high frequency litz wire can generate the desired 4 mT and such a flux density in axial direction is below the nerve stimulation threshold at 150 kHz. Operation at even higher frequencies would be feasible, too.

In another exemplary embodiment of the present invention, a computer program or a computer program element is provided that is characterized by being adapted to execute the method steps of the method according to one of the preceding embodiments, on an appropriate system.

The computer program element might therefore be stored on a computer unit, which might also be part of an embodiment of the present invention. This computing unit may be adapted to perform or induce a performing of the steps of the method described above. Moreover, it may be adapted to operate the components of the above described apparatus. The computing unit can be adapted to operate automatically and/or to execute the orders of a user. A computer program may be loaded into a working memory of a data processor. The data processor may thus be equipped to carry out the method of the invention.

This exemplary embodiment of the invention covers both, a computer program that right from the beginning uses the invention and a computer program that by means of an up-date turns an existing program into a program that uses the invention.

Further on, the computer program element might be able to provide all necessary steps to fulfil the procedure of an exemplary embodiment of the method as described above.

According to a further exemplary embodiment of the present invention, a computer readable medium, such as a CD-ROM, is presented wherein the computer readable medium has a computer program element stored on it which computer program element is described by the preceding section.

A computer program may be stored and/or distributed on a suitable medium, such as an optical storage medium or a solid state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems.

However, the computer program may also be presented over a network like the World Wide Web and can be downloaded into the working memory of a data processor from such a network. According to a further exemplary embodiment of the present invention, a medium for making a computer program element available for downloading is provided, which computer program element is arranged to perform a method according to one of the previously described embodiments of the invention.

It has to be noted that embodiments of the invention are described with reference to different subject matters. In particular, some embodiments are described with reference to method type claims whereas other embodiments are described with reference to the device type claims. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters is considered to be disclosed with this application.

However, all features can be combined providing synergetic effects that are more than the simple summation of the features.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing a claimed invention, from a study of the drawings, the disclosure, and the dependent claims.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfil the functions of several items re-cited in the claims. The mere fact that certain measures are re-cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A drive threaded joint (1) for insertion in a body structure, the drive threaded joint comprising:

a first part (2) provided as a thread-body for connection with a support structure; and

- a second part (3) provided as a drive-body for driving the first part;

wherein the thread-body has a thread (4) defining a screwing direction along a thread axis (6);

wherein the second part is mechanically connectable to the first part;

wherein the second part has a magnetic structure (7) such that a rotating movement of the second part around an axis is activatable by an appropriate magnetic field ; and

wherein, the drive threaded joint is further arranged such that a torque energy created by said rotation of the second part is transferrable to the thread-body once the second part is rotationally mechanically connected to the first part, implying thus the driving of the thread-body in the screwing direction around the thread axis.

2. Drive threaded joint according to claim 1, wherein:

i) the drive threaded joint is a drive screw (500) for insertion into a body structure; and wherein the first part is provided as a screw-body (502) for connection with a support structure; wherein the screw-body has an external thread (504) defining a screwing direction (506) along a thread axis (508); or

ii) the drive threaded joint is a drive screw (510) for insertion into a body structure; and wherein the first part is provided as a nut-body (512) for connection with a support structure; wherein the nut-body has an internal thread (514) defining the screwing direction along the thread axis.

3. Drive threaded joint according to claim 1 or 2, further comprising a guiding tube (520), wherein the second part is movably hold in the guiding tube (520), in which the second part can be freely rotated and can also be freely translated in a direction (522) of the thread axis; and

wherein the first part and the second part are provided with corresponding engagement interfaces (524) to connect one to the other; and wherein a translation (526) of the second part in direction of the thread axis towards the first part brings the first part and the second part into engagement with each other to transfer the torque energy.

4. Drive threaded joint according to one of the preceding claims, wherein the corresponding engagement interfaces are provided as interfaces comprising at least one of the group of latches, protrusions and front-end gearing.

5. Drive threaded joint according to one of the preceding claims, wherein the first part and the second part comprise corresponding stop elements (532, 534) arranged to stop the rotation of the second part with respect to the first part when these stop elements are in abutment one to the other, allowing therefore the transfer of the rotation energy from the second part to the first part.

6. Drive threaded joint according to one of the preceding claims, further comprising an energy storage, wherein the second part is connected to the energy storage;

wherein the drive threaded joint is further arranged such that the mechanical energy corresponding to the rotation of the second part in a first angular direction is transferrable to the energy storage as an activation energy; and

that the energy storage can release, upon activation, the stored activation energy as an activation force on the second part to cause a rotating movement of the second part in a second angular direction opposite the first angular direction to generate said torque;

wherein, preferably, the energy storage is a torsion spring element.

7. A system (200) for targeted magnetic activation of an inserted device, the system comprising:

a magnetic field generator (202) configured to generate: a primary magnetic field with an arrangement resulting in a field free point or field free line where the fields cancel; and a displaceable secondary magnetic field to shift the position of the field free point and/or a mechanical movement of the magnetic field generator; and

wherein the magnetic field generator is configured to displace the magnetic field to cause movement of a moving part of a determined one of a plurality of devices for insertion in a body;

while, preferably, other devices of the plurality of devices remain in the same state.

8. System according to claim 7, wherein the magnetic field generator is configured to cause a targeted movement of the determined device for insertion and all other devices for insertion remain non-rotating;

wherein, preferably, the magnetic field generator comprises permanent magnets with N/S poles configuration on a movable support arm to perform a helical movement in order to create the rotating field to move the field free point.

9. System according to claim 7 or 8, wherein the magnetic field generator comprises:

a primary magnetic source for generation of the primary magnetic field; and - a secondary magnetic source for generation of the displaceable secondary magnetic field;

wherein, preferably, an X-ray imaging is provided, and the primary magnetic source is provided by a magnetic system, and the secondary magnetic source is provided by a movable magnetic manipulator.

10. System according to one of the claims 7 to 9, wherein at least one inserted device is provided as a drive threaded joint according to one of the claims 1 to 6.

11. System according to one of the claims 7 to 10, wherein at least one inserted device is provided as a radiation providing seed (10) for use in radiotherapy, the seed comprising: a seed core (12) that is configured to generate radiation; a casing (14) providing a cavity (16); and a movable (18) insert which is guided inside the cavity;

wherein the seed core is attached to the movable insert; wherein the movable insert is configured as a magnetic insert, such that upon applying a magnetic field with a moving component, the insert is movable relative to the casing; wherein the insert is movable between a first position (PI) and a second position (P2) such that the relative position or orientation of the insert with respect to the casing is changed from a first position or orientation to a second position or orientation; wherein in the first position, the seed core is in a shielded arrangement within the casing, and wherein in the second position, the seed core is in an exposed arrangement, such that in the second position, the seed provides more radiation than in the first position; wherein, preferably, the movable insert is configured to cause a movement between the first and the second position upon being moved relative to the casing; and wherein, further preferably, the insert is a screw insert (20) with an outer thread (22); and the screw insert has a magnetization component (24) transverse to the screwing direction, such that upon applying a magnetic field with a rotational component, the screw insert is rotatable relative to the casing; and/or

wherein, preferably, the at least one device for insertion in a body is provided as an interventional device of at least one of the group of:

a) a biopsy needle,

b) an interventional tool for manipulating tissue or bone structure,

c) an ultrasound transducer head, and

d) a drive screw;

wherein the interventional device comprises a corpus structure with an outer thread for interacting with surrounding portions of the body; and

wherein, upon rotation of the corpus structure, the device is moving relative to the surrounding portions of the body.

12. System according to one of the claims 7 to 11, wherein the system comprises an imaging system of at least one of the group of:

a magnetic particle imaging (MPI) system;

a magnetic resonance imaging (MRI) system; and

an X-ray/CT imaging system.

13. A method for activating a drive threaded joint for insertion in a body structure, the method comprising the following steps:

i) providing a drive threaded joint with a first part provided as a thread-body for connection with a support structure; and a second part provided as a drive-body for driving the first part; wherein the thread-body has a thread defining a screwing direction along a thread axis; wherein the second part is mechanically connectable to the first part; wherein the second part has a magnetic structure such that a rotating movement of the second part around an axis is activatable by an appropriate magnetic field;

111) generating a primary magnetic field with a field free point; and

112) moving the position of the field free point; iii) thereby causing rotating of the second part of the drive threaded joint by displacing the field free point; thus creating torque energy; and

iv) rotationally mechanically connecting the second part to the first part and thereby transferring the torque energy for driving of the thread-body in the screwing direction around the thread axis.

14. Method according to claim 13, wherein in step iv), for the mechanical connection, the second part is translated along the axis of rotation in relation to the first part;

wherein the translation of the second part in direction of the thread axis towards the first part brings the first part and the second part into engagement with each other; and

wherein the torque energy is transferred activating the drive threaded joint.

15. Method according to claim 13 or 14, wherein in step iii), an opposite rotational movement is used for charging an energy storage to store energy to be released to cause a rotational movement to create torque energy; and

wherein in step iii), after a determined time, the stored energy is released to generate the rotational movement to create the torque energy.

16. Method according to claim 13, 14 or 15, wherein steps i) to iv) are

implemented iteratively such that the thread-body is driven several successive times.

17. A method (300) for activating a device inserted into a body structure, the method comprising the following steps:

a) providing (302) a plurality of devices inserted in a body;

wherein each device comprises a movable part having a permanent magnet structure;

bl) generating (304) a primary magnetic field with a field free point;

b2) moving (306) the position of the field free point; and

c) thereby causing (308) movement of a movable part of a determined one of the plurality of the inserted devices by displacing the field free point.

18. Method according to claim 17, wherein at least one of the inserted devices is a drive threaded joint according to one of the claims 1 to 6; and wherein in step c) it is provided:

cl) causing movement of the second part of the drive threaded joint in the first state, wherein the movement is caused in the screwing direction; and wherein, by rotation of the second part, a torque moment of inertia is achieved in the second part; and

c2) temporarily connecting the second part to the first part in the second state, causing to transfer the torque moment of inertia to the thread-body, thereby driving the thread-body.

19. A computer program element for controlling a drive threaded joint according to one of the claims 1 to 6, which, when being executed by a processing unit, is adapted to perform the method steps of one of the claims 13 to 18.

20. A computer readable medium having stored the program element of claim 19.