NL2034167B1

NL2034167B1 - Magnetic field inductor

Info

Publication number: NL2034167B1
Application number: NL2034167A
Authority: NL
Inventors: Marthinus Heunis Christoff; Misra Sarthak
Original assignee: Univ Twente
Priority date: 2023-02-16
Filing date: 2023-02-16
Publication date: 2024-09-03
Also published as: WO2024172656A1

Abstract

2 1 ABSTRACT The present disclosure relates to a magnetic ﬁeld inductor for navigating and positioning a magnetic manipulation element in a clinical environment. The magnetic ﬁeld inductor including an 5 electromagnetic coil for generating a magnetic ﬁeld, the electromagnetic coil comprising at least one conductive element, for instance a copper wire, wound in a plurality of windings around a core extending in axial direction, thereby providing an outer circumferential coil element surface. The magnetic ﬁeld inductor including a conduit assembly, including at least one ﬂuid conduit for carrying a ﬂuid coolant, the at least one ﬂuid conduit being arranged in a pattern around the outer 10 circumferential coil element surface of the electromagnetic coil and being conﬁgured to be in thermally conductive contact with the outer circumferential coil element surface in order to allow conduction of heat between the at least one conductive element and ﬂuid coolant in the at least one ﬂuid conduit.

Description

MAGNETIC FIELD INDUCTOR

The present invention relates to a magnetic field inductor including a cooling unit, a system comprising such magnetic field inductor and a magnetic manipulation device, and to a method of operating a magnetic field inductor. In particular, the invention relates to navigating and positioning a magnetic manipulation element in a clinical environment.

For minimally or non-invasive surgery and other biomedical applications, means and methods for wireless manipulation of magnetic manipulation elements have been developed. An example of such magnetic manipulation element is a magnetically activated surgical catheter for endovascular procedures. Such magnetic manipulation elements may take the form of helical microrobots or helical endoscopic capsules that are inserted e.g. in a human body and which will be propelled under influence of a time-varving, rotating magnetic field. The time-varying, rotating magnetic field will induce a magnetic torque in the magnetic device which, due to e.g. its’ helical shape, may be steered through an artery or vein.

As another example of a biomedical application, a low-footprint collaborative surgical robot arm may be used to provide a metaphorical magnetic hand that can reach any extremity of a patient to manipulate deep-scated instruments. Such an arm consists of serial-link robots designed to reduce the physical burden of surgeons.

A magnetic field inductor system developed for any of the above-mentioned applications may have an electromagnetic coil installed on a robotic arm. During operation of the magnetic field inductor (by supplying the coil with a constant current), the electromagnetic coil heats up considerably. The amount of heat generated by the coil in view of the constant flow of current over time may also raise temperature in the nearby environment of the electromagnetic coil which prevents its use in more demanding clinical environments. On the one hand, overheating may result in decreased performance of the electromagnetic coil, as for example the coil insulation may be damaged and e.g. cause short circuits between the coil and neighboring components. On the other hand, during state-of-the-art interventions, the proximity of the coil and further surgical instruments to delicate brain, heart, and vascular tissue must be controlled reliably, both in space as temperature. Hence, in a clinical environment, the temperature of any device operated by using a constant flow of current should sometimes be limited to a relatively low temperature, for instance about 43° C or below. Such limit on the temperature is to be maintained for the whole duration of any intervention. This puts a restriction on the maximum time interval in which the device can be operated safely. In practice the magnetic field inductor system can only be operated for about 10 minutes or even less.

It is an object of the invention to provide a magnetic field inductor configured for navigating and positioning a magnetic manipulation element arranged its magnetic field that addresses at least one of the above-indicated and/or other limitations.

According to an aspect the object may at least partially be achieved in a magnetic field inductor as claimed in claim 1. The magnetic field inductor includes an electromagnetic coil for generating a magnetic field, the electromagnetic coil comprising at least one conductive element, for instance a copper wire, wound in one or more windings around a core extending in axial direction, thereby providing an outer circumferential coil element surface. The magnetic field inductor includes a cooling unit configured for cooling the electromagnetic coil, the cooling unit comprising a conduit assembly, comprising at least one fluid conduit for carrying a fluid coolant, the at least one fluid conduit being arranged in a pattern around the outer circumferential coil element surface of the electromagnetic coil and being configured to be in contact with the outer circumferential coil element surface in order to allow conduction of heat between the at least one conductive element and fluid coolant in the at least one fluid conduit.

The fluid coolant may be a liquid, a gas or a mixture of liquid and gas. A suitable fluid coolants may be water, liquid nitrogen, helium and the like.

The core may be a physical core made of magnetic or paramagnetic material. In other embodiments, however, the core is an imaginary core and comprises gas (for instance. air).

Obviously in the latter case the at least one electrically conductive element is wound relative to the imaginary core, for instance on generally tubular support surrounding the core.

In the context of the present application the term “contact” is intended to mean heat conductive contact between two elements wherein both elements are placed in thermally conductive contact with each other. In embodiments of the present disclosure the thermally conductive contact is a direct physical contact between the two elements. In other embodiments the thermally conductive contact is intended to mean that the two elements are positioned close to each other such that the interspace between the two elements is small enough to provide a heat transfer as if the two elements were in physical contact with each other.

In embodiments of the present application the at least one fluid conduit of the conduit assembly comprises a conduit wall made of heat conductive material. The conduit wall may be arranged to physically contact the at least one conductive element. In case both the tubular inner wall and the electromagnetic coil are made of metal (for instance, steel and copper, respectively), there is metal-on-metal heat conduction between the coil and the fluid coolant inside the conduit.

In embodiments of the present application a power source for the inductor is provided wherein the power source is configured to drive the electromagnetic coil with a direct current (DC). This direct current causes the electromagnetic coil to generate an essentially stationary magnetic field. The magnetic field is strong enough to cause a magnetic manipulation element located at close range (i.e. in the magnetic field) to be held and to move along any movement of the inductor.

The inductor may comprise mounting means for mounting the cooling unit with the electromagnetic coil connected thereto to a robotic arm, for instance a robotic arm of an advanced robotics for magnetic manipulation (ARMM) system. When the inductor is mounted to the (outer end of) a robotic arm and the robotic arm is configured to be remotely controlled (by an operator), the robotic arm can be used to move the associated magnetic manipulation element controlled from the same remote position.

In embodiments of the present application the conduit assembly comprises a tubular inner housing wall made of heat conductive material, for instance metal, the tubular inner housing wall being arranged or configured to be arranged in a fitting manner around the electromagnetic coil.

The conduit assembly may further comprise an outer housing wall arranged around the inner housing wall, wherein the at least one fluid conduit is arranged between the tubular inner housing wall and the outer housing wall. The outer housing wall may be attached to the tubular inner housing wall, for instance by clamping the outer housing onto the tubular inner housing, although in other embodiments the inner and outer housing walls remain free from each other.

In embodiments of the present application wherein the at least one fluid conduit of the conduit assembly comprises a conduit wall made of heat conductive material this conduit wall may be arranged to physically contact the tubular inner housing wall.

The conduit(s) may be placed directly against the outer circumferential coil element surface or against an inner housing wall (which inner housing wall may be placed directly against the coil element). In some embodiments the conduit(s) may be arranged between an inner housing wall and an outer housing wall, wherein the conduit(s) may preferably be placed only against the inner housing wall. A gap may exist between the conduit(s) and the outer housing wall so as to provide for a ventilation space allowing relatively cold outside air to be guided along the conduit(s) in order to assist in discharging heat to the environment.

In embodiments of the present application a conduit is formed by a tube (or, similar, a pipe, hose and the like). The tube may be made of relatively stiff material so that the tube can remain autonomously in its original shape (forming a pattern, as mentioned above) while in other embodiments the tube is made of flexible material, as will be explained hereafter.

The tube may be placed directly against the outer circumferential coil element surface or against an inner housing wall (which inner housing wall may be placed directly against the coil clement).

In embodiments of the present application a conduct is formed by a channel formed in at least one of an inner housing wall and an outer housing wall, wherein the channel is optionally formed by one or more grooves arranged in only the inner housing wall, in only the outer housing wall or in both the inner and outer housing walls. The channel (herein also referred to as the duct) is realized once the inner and housing has been connected to each other. In embodiments of the present disclosure the inner housing wall and/or outer housing wall may comprise an inlay wherein the one or more grooves are formed. For instance, the housing wall may be comprised of a relatively strong metal wall that at one surface thereof as been provided with a relatively soft backing material forming the inlay. In this example the channel / duct may have been formed by one or more grooves provided only in the backing material.

A contact area may be defined as the area of contact between the conduit assembly and the outer circumferential surface of the electromagnetic coil. In preferred embodiments this contact area may be at least 50%, preferably at least 60%, more preferably at least 70%, of the total area of the circumferential surface of the electromagnetic coil. In these embodiments the temperature of the electromagnetic coil in use may be kept below a safe value (i.e. safe for the practitioner who moves the manipulation element by appropriate movement of the magnetic field inductor, safe for the equipment used (i.e. for the manipulation element etc.) and/or safe for the individual that is treated by the manipulation element), for instance lower than 43 degrees Celsius.

The inventors have found that an especially efficient cooling of the electromagnetic coil mag be achieve in a inductor wherein the cross-section of the at least one conduit is non-axisymmetric.

The non-axisymmetric shape of the conductor has a positive influence the amount of energy to be discharged by the cooling unit. In specific examples of the present disclosure the at least conduit has a generally rectangular, triangular, trapezoid-like, D-like, or droplet like shape in cross-section.

Alternatively or additionally, an efficient discharge of heat can be accomplished in a magnetic field inductor wherein the part of the tubular inner housing wall facing the electromagnetic coil (and which may be placed against or close to the electromagnetic coil) is substantially flat. The fact that the inner housing wall is flat means that a relatively large contact area is created, resulting in a relatively efficient transfer of heat from the electromagnetic coil to the cooling unit.

In embodiments of the present application the cooling unit comprises at least one pump connected to the at least one conduit for pumping fluid coolant through the cooling unit. In an embodiment a single pump is used for two or more conduits, while in other embodiments each conduit has its own pump. Furthermore, the fluid flow may be controlled using one or more controllable valves. For instance, in embodiments wherein the conduit assembly comprises a first conduit and a second conduit, the cooling unit may comprise at least one pump configured to cause fluid coolant to flow in a first direction through the first conduit and in a second direction through the second conduit, the first direction preferably being essentially opposite to the second direction.

In embodiments of the present application wherein the electromagnetic coil has first end and a second end, opposite the first end. the at least one conduit comprises a first conduit arranged to 5 allow flow of fluid coolant from a first position at the first end of the electromagnetic coil to a second position at the second end of the electromagnetic coil and a second conduit arranged to allow flow of fluid coolant from a third position at the second end of the electromagnetic coil to a fourth position at the first end of the electromagnetic coil.

In embodiments of the present application the at least one conduit is configured to extend generally parallel to the at least one conductive element. In a further embodiment the at least one conduit has an essentially helical shape. The helical shape preferably defines a pattern that follows the windings of the electromagnetic coil. In case of two conduits the pattems of both the first conduit and the second conduit may be formed by helical trajectories. The first conduit extends along a first helical trajectory, the second conduit extends along a second trajectory. The first and

I5 second trajectories may be shaped and dimensioned so that the first conduit extends essentially parallel to the second conduit. Alternatively or additionally, the first and second trajectories may be shaped and dimensioned so that both conduits extend in an abutting manner relative to each other in order to maximize the heat transmission area of the conduit assembly.

In embodiments of the present application wherein at least one of the fluid conduits of the conduit assembly comprises an inlet and an outlet, the axial position of the inlet substantially may correspond to the axial position of the outlet. As when the inlet and outlet are in the same level, it allows the liquid to enter and exit the channel with a relatively steadier flow. This may further minimize pressure differences and reduce a risk of - too high — turbulent flow. This may provide a more effective heat transfer, minimizing pressure loss and increase overall efficiency. Should the inlet and outlet be at different levels, it might cause the liquid to flow through the channel at varying, different speeds, which potentially could create pressure differences. The position of the inlet and outlet may further influence turbulent flow. which reveals a trade-off between the positions of the in- and outlet, and turbulence. Herein turbulent flow may display a high heat transfer coefficient, accompanied by high pressure drop and fluid resistance. Hence, it may be preferable to have a slight turbulence. Overall, turbulent flow may increase a heat transfer rate, while simultaneously decrease an overall efficiency of the system. Thus, there is a need to balance the trade-off between heat transfer rate and system efficiency.

In embodiments of the present application the conduit assembly is configured to provide a first cooling capacity at or close to a first (distal) end of the coil element and a second cooling capacity at or close to the second (proximal) end of the coil element, wherein the first cooling capacity is larger than the second cooling capacity. This makes it possible to realize a temperature variation over the length (i.e. the axial direction) of the inductor. For instance. at the end of the conductor that in use is closest to a human being (operator, patient) the cooling capacity can be selected to be larger than at other positions so that the temperature at this end of the inductor can be optimally reduced.

In embodiments of the present application the cooling unit comprises ventilation means configured to provide a ventilation air flow along the at least one conduit. For instance, the ventilation means may comprise various air inlet and air outlet openings provided in the housing.

These openings may allow relatively cool outside air to pass along the conduits and thereby further cooling the same.

In embodiments of the present application the inductor comprises a fluid coolant reservoir.

The reservoir usually is situated rather remote from the source of heat (1.e. the electromagnetic coil) so that heat can be radiated more easily to the external environment. A further advantage is that in the reservoir an additional volume of fluid coolant can be stored. This additional volume of fluid coolant may be used to ensure that at any circumstance enough fluid coolant is available for keeping the conduit(s) filled with coolant (also if air bubbles are present inside the conduit).

The fluid coolant reservoir may be positioned at the first end of the electromagnetic coil. In use the reservoir is preferably positioned above the electromagnetic coil so that fluid coolant has the tendency to flow downward trough the at least one conduit so as to automatically cool the electromagnetic coil.

In embodiments of the present application the inductor further comprises a radiator in heat conductive contact with the conduit assembly.

In embodiments of the present application the inner diameter of a fluid conduit is smaller than the diameter of the inlet and the outlet so as to induce a turbulent flow of fluid coolant.

According to a further aspect, a system for navigating and positioning a magnetic manipulation element is provided, the system comprising: - a magnetic field inductor as defined herein; - at least one magnetic manipulation element, wherein the magnetic field inductor is configured generate a magnetic field for remote navigation and positioning of the at least one magnetic manipulation element when the at least one magnetic manipulation element is placed in this magnetic field.

In embodiments of the present application the system is configured for allowing the magnetic manipulation element to be moved/positioned in a clinical environment.

The magnetic manipulation element may be an endovascular catheter, for instance an endovascular ferromagnetic tip catheter.

The system may further comprise a robotic arm on which the magnetic field indictor is mounted, preferably as an end effector.

Another aspect of the present disclosure relates to the use of a magnetic field inductor or system as defined herein.

According to another aspect a method of operating a magnetic field inductor, for instance the magnetic field inductor as defined herein or a system as defined herein, for navigating and positioning a magnetic manipulation element arranged in the magnetic field of the magnetic field inductor is provided, the method comprising: - driving the magnetic field inductor with a direct current (DC) for generating a magnetic field, the magnetic manipulation element being located in the generated magnetic field: - navigating and positioning the magnetic manipulation element by moving the magnetic field inductor; the method further comprising cooling the electromagnetic coil of the magnetic field inductor during the generation of the magnetic field by causing at least one fluid coolant to flow through the one or more fluid conduits of the conduit assembly of the magnetic field inductor.

Further objects, details, characteristics, aspects, effects and advantages of particular embodiments of the disclosure are described in the following detailed description of a number of exemplary embodiments. In the description reference is made to the annexed drawings.

BRIEF DESCRIPTION OF DRAWINGS

By way of example only, the embodiments of the present disclosure will be described with reference to the accompanying drawings, wherein:

Figures 1-4 show a first embodiment of a magnetic field inductor, wherein figure 1 is a top- side view of the magnetic field inductor, figure 2 is a cross-section along line II-I of figure 1 without the conduit assembly, figure 3 is bottom-side view of magnetic field inductor, and figure 4 is a side view showing the conduit assembly to be arranged between the outer housing wall 2 and the electromagnetic coil 7;

Figures 5A and 5B are cross-sections of further embodiments of the magnetic field inductor;

Figure 6 illustrates schematically a cross section of another example of a magnetic field inductor in accordance with the invention:

Figures 7A-7B illustrate schematically cross-sections of examples of ducts in accordance with the invention;

Figures 8A-8B illustrate schematically cross-sections of further examples of ducts in accordance with the invention;

Figure 9 illustrates schematically a further embodiment of a duct of a cooling unit in accordance with the invention;

Figure 10 illustrates another exemplifying embodiment of a duct of a cooling unit in accordance with the invention; and

Figure 11 schematically represents a view of an embodiment of a system comprising a magnetic field inductor and a magnetic manipulation element, wherein the magnetic field inductor is configured to cause the magnetic manipulation element to move.

Generally, a magnetic field inductor I may be mounted to a positioning device such as a robotic arm 31 (cf. figure 11). The positioning device is configured to move and position the magnetic field inductor 1 to a desired position (1.e. a desired location and orientation). In the magnetic field of the magnetic field inductor 1 one or more magnetic manipulation elements (for instance any of the magnetic manipulation elements 40 described in connection with figure 11) may be placed. Movement of the magnetic field inductor 1 mounted on the positioning device causes a corresponding movement of the manipulation element(s), thereby enabling the positioning device to guide (i.e. to navigate and position) the manipulation element(s) to a desired target position.

The positioning device, magnetic field inductor 1 and the magnetic manipulation element are located in a workplace, such as — but not limited to — a clinical environment. Examples of where clinical environments may be found include rooms for training sessions of surgeons and/or operators, academic and/or general research facilities, hospital pre-intervention preparation and/or waiting rooms, operating rooms, recovery rooms, etc.

Figuresl1-4 show a first embodiment of the magnetic field inductor 1. Figure 1 is a top-side view of an outer shell or outer housing wall 2, figure 2 is a cross-section along line I-11 of figure 1 without the conduit assembly, figure 3 is bottom-side view of the outer housing wall 2, and figure 4 is a side view showing the conduit assembly to be arranged between the outer housing wall 2 and the electromagnetic coil 7.

More specifically, figure 1 shows an outer housing wall 2 in which a number of fluid inlets 3, 4 and fluid outlets 5, 6 are arranged and an opening 48. The fluid inlets 3, 4 and fluid outlet 5. 6 are connected to a number of fluid conduits 12a, 12b (cf. figure 4). The fluid conduits 12a, 12b are in fluid connection with a pump unit 28 comprising one or more pumps configured to pump a fluid coolant through the fluid conduits 12a, 12b, as will be explained later. In the inner surface of the outer housing wall 2 a number of helical grooves 22 is arranged. These grooves 22 are arranged so as to at least partially receive therein a fluid conduit 12 in a fitting manner so that an optimal heat conduction from the fluid conduits 12 through the outer housing wall 2 to the environment can take place. In case of two different fluid conduits, grooves 22a, 22b are arranged so as to at least partially receive therein the respective fluid conduits 12a, 12b.

The electromagnetic coil 7 is accommodate in the inner space defined inside the outer housing wall 2. This situation is shown in figure 2 (wherein for simplicity the fluid conduits 12a, 12b have not been shown). The electromagnetic coil 7 is connected to a DC power source 27 that provides a suitable current to the electromagnetic coil to generate a static external magnetic field with the required high field strength (tvpically in the order of 20-60 mT at a distance in the order of 50-250 mm).

Still referring to figure 2, a cross-section of the magnetic field inductor 1 of figure 1 is shown, illustrating an interior of the magnetic field inductor 1. The figure schematically shows the clectromagnetic coil 7 for generating the magnetic field. The electromagnetic coil 7 is comprised of one or more conductive elements 39 wound in one or more windings around a (physical or imaginary) core 8. The electromagnetic coil 7 extends in an axial direction 9, thereby providing an outer circumferential coil element surface. The electromagnetic coil 7 and its outer coil element surface is enclosed by an inner shell 10. In some embodiments the electromagnetic coil 7 may include several coil elements 7a, 7b making up the coil 7.

Referring to figures 2 and 3, a conduit assembly 11 is illustrated, comprising at least one fluid conduit 12 for carrying a fluid coolant. The at least one fluid conduit 12 is arranged in a pattern around the outer surface of the inner shell 10. In the example of figures 1-4 the fluid assembly is arranged between the outer housing wall 14 and the outer surface of the inner shell 10.

Furthermore, in the embodiments shown in these figures the conduit 12 includes two separate fluid conduits 12a, 12b. The conduit assembly 11 is configured to be in thermally conductive contact, for instance but not limited to direct physical contact, with the inner shell 10 to allow conduction of heat between the at least one conductive element 7a; 7b and fluid coolant in the at least one fluid conduit 12. The contact between conduit assembly 11 and the surface of the inner shell 10 is physical. preferably flush, but at least heat conductive contact. Thermal conductivity of the contact may be further improved by applying a thermal interface material. such as a thermal paste. The core 8 of the electromagnetic coil 7 may be a magnetic or paramagnetic material, or air, or other suited material for supportmg a magnetic field.

The arrangement of the conduit assembly 11 and the inner shell 10 allows for indirect cooling, meaning that there is no direct contact between the fluid coolant and the conductive element 7a. This allows for the fluid to be a liquid, a gas, or even a combination thereof. A contact arca 13, as shown in figures 6, 7A, 7B, 8A, 8B, which may be defined as the area of contact between the conduit assembly 11 and the inner shell 10, is at least 50%, preferably at least 60%, or more preferably at least 70%, of the total area of the surface of the inner shell 10 of the electromagnetic coil 7.

In some embodiments of the present disclosure the walls of the conduits (herein also referred to as the conduit wall 50) may be positioned against the material of the windings of the conductive clement so as to provide a direct contact between the conduits and electromagnetic coil and therefore an optimal thermal conduction between the conductive element and the fluid coolant in the conduit assembly. In other embodiments the housing comprises both the outer shell or outer housing wall 2and the inner shell 10 or inner housing wall (cf. figure 5A). The inner shell 10 or inner housing wall 29 has a generally tubular shape and can be arranged around the electromagnetic coil 7 (preferably in a fitting manner ensuring direct physical contact between the inner shell or inner housing wall 29 and the conductive element(s) 39 of the electromagnetic coil 7, but in other embodiments a small gap may exist between the inner housing wall 29 and the conductive element(s) 39). Such a gap may be filled with a thermal paste as to provide a thermal interface. The conduit assembly in this embodiment is arranged between the inner shell or inner housing wall 29 and the outer shell or outer housing wall 14.

In other embodiments a conduct 12 is formed by a channel 44 arranged between an inner housing wall 45 and an outer housing wall 46, wherein the channel is formed by one or more grooves or indentations arranged in the inner housing wall 45, in the outer housing wall 46 (as is shown in figure 5B) or in both the inner and outer housing walls 45, 46.

For example, the at least one fluid conduit 12 may be formed by at least one channel 1.e. duct formed in the surface of the outer housing wall 14 facing the tubular inner housing. Hence, the fluid conduit 12 may be arranged as carved out conduits on an inner lining 15 of the outer housing 14.

In some embodiments, the conduit 12 may be of a rigid material, in other embodiments the conduit 12 may be made of flexible or soft material(s). This may provide for a lower weight, or e.g. for a larger magnet. It may further enable squeezing of the inner housing in the outer housing 14, thereby potentially increasing the thermally conductive contact area. It may also allow for a front end 16 to be covered by the shell 2 i.e. outer housing 14. Herein the front end 16 refers to the location or area of intervention where the electromagnetic field is intended to be directed to. The outer housing 14 may be attached to the tubular inner housing by, for instance clamping the outer housing 14 onto the tubular inner housing. The surface of the tubular inner housing facing the electromagnetic coil 7 is preferably substantially flat. This facilitates maximizing contact surface i.e. contact area 13 between fluid conduit 12 and inner shell 10.

The outer shell may be part of the conduit assembly 11. It may also be a tubular shaped cooling shell having a proximal and a distal end. The cooling shell may include at least two grooves running i.e. spiraling across an inner circumference thereof from the proximal end to the distal end of the shell. The grooves are formed such that when an inner housing is positioned inside the cooling shell, the outer surface of the inner housing provides a sealing surface closing off the grooves to form the at least two respective coolant conduits.

The conduit assembly 11 may include a first conduit 12a configured to allow fluid coolant to flow in a first direction and a second conduit 12b configured to allow fluid coolant to flow in a second direction, opposite the first direction. Thereto, for example, one or more pumps may be connected to the fluid inlets 3: 4 and configured to pump fluid coolant through the one or more fluid conduits, in the example of figures 1-3 two conduits 12a, 12b. the configuration of pumps may be controlled via control means, such as a controller. Or there may be one pump using a splitter to direct flow in opposite directions through the conduits. In addition, or instead, the fluid inlets 3, 4 may be connected via valves the pump unit 28 to achieve the same.

It has been discovered by the inventor that the cooling operation of the conduit assembly may be further improved by inducing a turbulent flow in the at least one fluid conduit or fluid conduits. Such turbulent flow may be achieved by adaptation of the one or more pumps or the manner of control of the one or more pumps. More preferably, it is achieved by configuring the fluid conduit and associated inlet such that an inner diameter of a fluid conduit is smaller than the diameter of the inlet and the outlet. By such configuration a turbulent flow is induced. This difference in diameter for obtaining a turbulent flow may be achieved for example by changing shape of the fluid conduit, or by adding one or more projections inside the fluid conduit.

Furthermore, the inner surface of the fluid conduit is preferably smooth, or at least not rough, in order to reduce drag.

Referring to figures 2 and 3, the electromagnetic coil has a first end 17 and a second end 18, opposite to the first end 17. The at least one fluid conduit 12 i.e. conduit assembly 11 may include afirst conduit 12a arranged to allow flow of fluid coolant from a first position 3 at the first end 17 of the electromagnetic coil 7 to a second position 5 at the second end 18 of the electromagnetic coil 7 and a second conduit 12b arranged to allow flow of fluid coolant from a third position 4 at the second end 18 of the electromagnetic coil 7 to a fourth position 6 at the first end 17 of the electromagnetic coil 7.

The at least one conduit 12 or conduits 12a, 12b may be configured to extend generally parallel to the direction of the conductive element, for example the copper wire, such as in figures1-4. Herein, the conduits 12, 12a, 12b have an essentially helical shape.

Referring to figures 9 and 10, illustrating different embodiments of fluid assemblies 19; 20, the at least one conduit 21 may extend in one or more different directions, for instance along the axial direction 23 of a coil intended to be encompassed by the fluid assembly. Referring to figure

9, the conduit 21 runs partially axial along the axis of the electromagnetic coil and partially circular and bending around the coil axis (extending in axial direction 23). Referring to figure 10, the conduit 54 runs substantially axially along the central axis 23 of the electromagnetic coil, only to bend at opposite ends of the coil.

As illustrated in figure 9, the inlet 24 and outlet 25 of the fluid conduit 21 of the conduit assembly 11 are positioned at substantially the same axial position. By having the axial position of the inlet substantially corresponding to the axial position of the outlet, a minimum required capacity of the pump is reduced, such as e.g. less than 5%, 10%, or 20%. When the axial position of inlet and outlet substantially correspond, this is preferably within 20% of the total axial height of the coil.

Referring to figures 7A, 7B, 8A, 8B. various shapes of the fluid conduit(s) in cross-section are shown. As mentioned above, a surface contact area 13 is preferably optimized for heat conductive contact between the conduit assembly 11 and the electromagnetic coil 7. To further enhance the cooling performance, the conduit preferably has a flat side surface facing the electromagnetic coil, see contact area 13. Whereas other sides not facing the coil may be shaped to optimize a surface area 26 to enable cooling of conduit by convection. The cross-sectional shape may

Referring to figure 6 another embodiment of a magnetic field inductor is schematically illustrated, wherein the fluid conduit 12 has an essentially triangular cross-section, is helically wrapped around the electromagnetic coil 7 and core 8, and the contact surface area 13 allows for heat conductive contact.

The magnetic field inductor, according to any of the examples illustrated in the figures may further include a fluid coolant reservoir 27, of which an example is shown in figure 4. The use of a reservoir allows to maintain a minimum pressure in the conduit assembly. It may further reduce the occurrence of air bubbles. The fluid coolant reservoir may be positioned at the first end of the electromagnetic coil. When placed at the distal, front end 17 or proximal end 18 of the electromagnetic coil 7, the reservoir is preferably shaped to correspond to the cross-section of the coil. For example, in case of a circular cross-section, the reservoir is shaped as a cylindrical, disc- like container for buffering fluid. Likewise, in case of a rectangular or square cross-section, the reservoir is shaped correspondingly.

To further enhance the cooling performance, the magnetic field inductor may further include a radiator in heat conductive contact with the conduit assembly. A radiator could be effective at dissipating heat in view of its relatively large surface area and fins which can increase the heat transfer coefficient or they could be coupled with fans to enhance convection and air flow. The size and type of the radiator used can vary, depending on the amount of heat that needs to be dissipated and the conditions of the surrounding environment. Additionally, with this kind of configuration, the coolant can be cooled down before returning to the heating element, improving the system efficiency. However, adding a radiator to the system may increase the complexity of the system and may also the risk of leakage.

Furthermore, the magnetic field inductor may further include a power source (not shown) that is configured to drive the electromagnetic coil with a direct current (DC).

Regardless of the embodiment of the fluid conduit(s) 12, 12a, 12b, the conduit assembly 11 may be configured to provide a first cooling capacity at or close to the first (distal) end 17 of the coil element 7 and a second cooling capacity at or close to the second (proximal) end 18 of the coil element, wherein the first cooling capacity is larger than the second cooling capacity. Herein, the proximal end is the end which is closest to where the magnetic field inductor is mounted, as e.g. a robotic arm or other component for moving the device, and the distal end is farther away from the mount and closer to the area of intervention, such as ¢.g. a subject in a clinical environment.

It has been discovered by the inventor that the cooling operation of the fluid assembly may provide for non-uniform cooling of the electromagnetic coil. For instance, the temperature at the distal end of the coil, which may be positioned closest to a subject in the clinical environment, is of more importance than that of the proximal end. Hence, the proximal end 18 may be allowed to rise, slightly higher than the distal end. Vice versa, it may be sufficient to maintain the distal end at a required temperature which is lower than the temperature quired at the proximal end.

More in general, the magnetic field inductor is configured to maintain, while in use, the temperature of the electromagnetic coil below 43 degrees Celsius; or at least, as mentioned above, at the distal end 17.

The magnetic field inductor as described in reference to the examples above, may be part of a system 30 for navigating and positioning a magnetic manipulation element in a clinical environment, such as a room for training sessions of surgeons and/or operators, academic and/or general research facilities, hospital pre-intervention preparation and/or waiting rooms, operating rooms, recovery rooms, etc. An example of such system 30 is shown in figure 11.

Figure 11 shows a positioning device, for instance a robotic arm 31, more specifically a 6

DoF robotic arm. The robotic arm 31 comprises a plurality of mutually pivotable and/or rotatable arm parts 32-34. The arm parts 32-34 may be actuated by electric motors (not shown) that can be controlled by a remote controller 35. The robotic arm 31 comprises an end effector 36 to which a magnetic field inductor 1 is mounted. To this end the magnetic field inductor 1 comprises mounting means 36, such as screws and the like, for mounting the inductor to the robotic arm 31.

Figure 11 also shows a manipulation element 40 to be manipulated by an operator via the positioning device. In the shown embodiment the manipulation element 40 comprises an endovascular magnetic catheter 41 that can be arranged into an individual (p). The endovascular magnetic catheter 41 is connected to a flexible control/steering shaft 42. In the tip of the catheter 41 a miniaturized electromagnet 43 is arranged. Power to the electromagnet 43 is supplied through the flexible shaft 42. The magnetic catheter 41 may be moved to a suitable target location by arranging the magnetic catheter 41 in the external magnetic field of the magnetic field inductor 1 and moving end effector with the magnetic field inductor 1 accordingly.

In certain embodiments the catheter 41 is capable of controlled release of one or more untethered capsules 47 fitted in a dock 55 at the catheter tip of the catheter 41. In these embodiments the catheter 41 is first guided to a suitable target location using the external magnetic field provided by the magnetic field inductor 1. Upon reaching this target location, a capsule may be ejected by reversing the direction of the current in the electromagnet 43. Upon ejection, the capsule may move as a projectile in the static magnetic field of the magnetic field inductor 1 until it reaches a further target location.

The magnetic field inductor 1 is arranged as part of the system and configured to be movable

I5 so as to cause remote navigation and positioning of the at least one magnetic manipulation element when the at least one magnetic manipulation element is placed in the magnetic field of the electromagnetic coil. The manipulation element as described herein can be formed by at least one of the catheter 41 and/or the releasable capsule.

In the embodiments described herein the cooling unit is configured to cool the electromagnetic coil in an indirect manner. Indirect cooling may be characterized in that there is an interface (for instance at least one thermally conductive wall) between the coolant and the (conductive element of the) electromagnetic coil. This interface may be a single wall, for instance conduit wall 50 or an inner housing wall 45 or may be a combination of the conduit wall 50 and an inner housing wall 29 placed around the electromagnetic coil. This is in contrast to cooling units that cool the electromagnetic coil in a direct manner. In direct cooling the coolant comes in direct contact with the (conductive element of the) electromagnetic coil. In view of the high electrical currents employed in the present magnetic field inductor strict safety measures should be taken, especially if the fluid coolant is electrically conductive. Furthermore, direct contact with the coolant means that direct liquid cooling requires cooling plants and water treatments, which increases the number of component of the cooling unit and may reduce its mobility (which is important a system wherein the coil is mounted to a robotic arm and used to guide a manipulation element).

Although the present invention has been described above with reference to specific embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims and, other embodiments than the specific above are equally possible within the scope of these appended claims.

Furthermore. although exemplary embodiments have been described above m some exemplary combination of components and/or functions, it should be appreciated that, altemative embodiments may be provided by different combinations of members and/or functions without departing from the scope of the present disclosure. In addition, it is specifically contemplated that a particular feature described, either individually or as part of an embodiment, can be combined with other individually described features. or parts of other embodiments.

Claims

CONCLUSIONS

1. A magnetic field inductor adapted to navigate and position a magnetic manipulation element arranged in the magnetic field of the magnetic field inductor, S the magnetic field inductor comprising: an electromagnetic coil for generating a magnetic field, the electromagnetic coil comprising at least one conductive element, for example a copper wire, wound in one or more turns around an axially extending core, thereby defining an outer surface of the coil element; a cooling unit adapted to cool the electromagnetic coil, the cooling unit comprising a conduit assembly comprising at least one fluid conduit for conveying a fluid coolant, the at least one fluid conduit being arranged in a pattern around the outer surface of the coil element of the electromagnetic coil and being adapted to be in thermally conductive contact with the outer surface of the coil element to permit conduction of heat between the at least one conductive element and fluid coolant in the at least one fluid conduit.

2. The magnetic field inductor of claim 1, wherein the at least one fluid conduit of the conduit assembly comprises a conduit wall of thermally conductive material, the conduit wall being adapted to make physical contact with the at least one conductive element.

3. Magnetic field inductor according to claim 1 or 2, wherein the conduit assembly comprises a tubular inner housing wall of heat-conducting material, for example metal, the tubular inner housing wall being arranged to fit around the electromagnetic coil.

4. The magnetic field inductor of claim 3, further comprising an outer housing wall disposed about the inner housing wall, the at least one fluid conduit being disposed between the tubular inner housing wall and the outer housing wall.

5. A magnetic field inductor according to claim 4, wherein the outer housing wall is attached to the tubular inner housing wall, for example by clamping the outer housing to the tubular inner housing.

6. A magnetic field inductor as claimed in claim 3, 4 or 5, wherein the at least one fluid conduit of the conduit assembly comprises a conduit wall of thermally conductive material and wherein the conduit wall is arranged to make physical contact with the tubular inner housing wall.

7. A magnetic field inductor according to any one of the preceding claims, wherein a conduit is formed by a tube, the tube optionally being arranged between an inner housing wall and an outer housing wall.

8. A magnetic field inductor according to any one of claims 1 to 6, wherein a conductor is formed by a channel formed in at least one of an inner housing wall and an outer housing wall, the channel optionally being formed by one or more grooves arranged in the inner housing wall, in the outer housing wall or in both the inner and outer housing walls.

9. Magnetic field inductor according to any of the preceding claims, wherein a contact area defined as the contact area between the lead assembly and the outer surface of the electromagnetic coil is at least 50%, preferably at least 60%, more preferably at least 70% of the total area of the outer surface of the electromagnetic coil.

10. Magnetic field inductor according to any one of the preceding claims, wherein the cross-section of the at least one lead is non-asymmetrical.

11. A magnetic field inductor according to any preceding claim, wherein the cross-section of the at least one lead has a generally rectangular, triangular, trapezoidal, D-like or drop-like shape.

12. Magnetic field inductor according to any one of the preceding claims, wherein the part of the tubular inner housing wall facing the electromagnetic coil is substantially flat.

13. Magnetic field inductor according to any one of the preceding claims, wherein the cooling unit comprises at least one pump connected to the at least one conduit for pumping liquid coolant through the cooling unit.

14. A magnetic field inductor according to any preceding claim, wherein the conduit assembly comprises a first conduit and a second conduit and wherein the cooling unit comprises at least one pump adapted to flow liquid coolant in a first direction through the first conduit and in a second direction through the second conduit, the first direction preferably being substantially opposite to the second direction.

15. A magnetic field inductor according to any preceding claim, wherein the electromagnetic coil has a first end and a second end opposite the first end, and wherein the at least one conduit comprises a first conduit configured to facilitate flow of liquid coolant from a first position at the first end of the electromagnetic coil to a second position at the second end of the electromagnetic coil and a second conduit configured to facilitate flow of liquid coolant from a third position at the second end of the electromagnetic coil to a fourth position at the first end of the electromagnetic coil.

16. A magnetic field inductor according to any preceding claim, wherein the at least one lead is arranged to extend generally parallel to the at least one conductive element.

17. A magnetic field inductor according to any preceding claim, wherein the at least one lead has a substantially helical shape.

18. A magnetic field inductor according to any preceding claim, wherein the at least one conduit assembly comprises a fluid conduit having a flat side surface facing the electromagnetic coil.

19. A magnetic field inductor as claimed in any preceding claim, wherein at least one of the fluid conduits of the conduit assembly comprises an inlet and an outlet, the axial position of the inlet substantially corresponding to the axial position of the outlet.

20. A magnetic field inductor according to any preceding claim, wherein the conduit assembly is configured to provide a first cooling capacity at or near a first (distal) end of the coil element and a second cooling capacity at or near the second (proximal) end of the coil element, the first cooling capacity being greater than the second cooling capacity.

21. A magnetic field inductor according to any preceding claim, wherein the cooling unit comprises ventilation means adapted to provide a ventilation air flow along the at least one conduit.

22. A magnetic field inductor according to any preceding claim, further comprising a fluid coolant reservoir.

23. The magnetic field inductor of claims 21 and 22, wherein the fluid coolant reservoir is positioned at the first end of the electromagnetic coil.

24. A magnetic field inductor according to any preceding claim, further comprising a radiator in thermally conductive contact with the conduit assembly.

25. A magnetic field inductor according to any preceding claim, wherein an inner diameter of a fluid conduit is smaller than the diameter of the inlet and the outlet to induce turbulent flow of fluid coolant.

26. A magnetic field inductor according to any preceding claim, adapted to maintain the temperature of the electromagnetic coil below 43 degrees Celsius during use.

27. A magnetic field inductor according to any preceding claim, further comprising a current source adapted to drive the electromagnetic coil with a direct current (DC).

28. Magnetic field inductor according to any of the preceding claims, comprising mounting means for mounting the cooling unit with the electromagnetic coil connected thereto to a robot arm, for example a robot arm of an Advanced Robotics for Magnetic Manipulation (ARMM) system.

29. A magnetic field inductor according to any preceding claim, adapted to navigate and position the magnetic manipulation element in a clinical environment.

30. System for navigating and positioning a magnetic manipulation element, the system comprising: - a magnetic field inductor according to any one of the preceding claims;

- at least one magnetic manipulation element, the magnetic field inductor being adapted to generate a magnetic field for remote navigation and positioning of the at least one magnetic manipulation element when the at least one magnetic manipulation element is placed in said magnetic field.

31. The system of claim 30, wherein the magnetic manipulation element is an endovascular catheter, for example an endovascular ferromagnetic tip catheter.

32. System according to claim 30 or 31, further comprising a robotic arm on which the magnetic field indicator is mounted, preferably as an end effector.

33. Use of a magnetic field inductor according to any one of claims 1 to 29 or a system according to any one of claims 30 to 32.

34. A method of operating a magnetic field inductor, for example the magnetic field inductor according to any one of claims 1-29 or a system according to any one of claims 30-32, for navigating and positioning a magnetic manipulation element in the magnetic field of the magnetic field inductor, the method comprising: - driving the magnetic field inductor with a direct current (DC) for generating a magnetic field, the magnetic manipulation element being located in the generated magnetic field; - navigating and positioning the magnetic manipulation element by moving the magnetic field inductor; the method further comprising cooling the electromagnetic coil of the magnetic field inductor during the generation of the magnetic field by flowing at least one liquid coolant through the one or more fluid conduits of the conduit assembly of the magnetic field inductor.