WO2024074416A1

WO2024074416A1 - A medical microdevice and registration apparatus for registering an ultrasound system and a localization system of the microdevice

Info

Publication number: WO2024074416A1
Application number: PCT/EP2023/077030
Authority: WO
Inventors: Bernhard Gleich; Juergen Erwin Rahmer
Original assignee: Koninklijke Philips N.V.
Priority date: 2022-10-07
Filing date: 2023-09-29
Publication date: 2024-04-11

Abstract

Disclosed are a medical microdevice, a medical device and a registration apparatus that allow for tracking a medical device in an ultrasound image while maintaining the quality of the ultrasound image. The microdevice comprises a casing and a magneto mechanical resonator. The magneto mechanical resonator comprises at least two magnetic objects providing a permanent magnetic moment. The magneto mechanical resonator is adapted to transduce an external excitation field into a mechanical movement of the at least two magnetic objects relative to each other such that a periodically changing magnetic response field is generated. A pressure sensitive element is arranged such that an external ultrasound signal induces an additional movement of the magnetic objects such that the periodically changing magnetic response field is changed in dependency of the external ultrasound signal.

Description

A MEDICAL MICRODEVICE AND REGISTRATION APPARATUS FOR REGISTERING AN

ULTRASOUND SYSTEM AND A LOCALIZATION SYSTEM OF THE MICRODEVICE

FIELD OF THE INVENTION

The invention relates to a medical microdevice for insertion into a human body and a reading system for reading a signal from the medical microdevice. Further, the invention refers to a registration apparatus, method, and computer program for registering an ultrasound system with an electromagnetic reading system for reading a signal from the medical microdevice.

BACKGROUND

In medical procedures it is often important to determine a position of a medical device within a region of interest. In particular, a lot of medical procedures utilize ultrasound to image a region of interest and to perform a surgical procedure using a medical device under ultrasound guidance. However, the medical devices themselves are often poorly visible in the ultrasound image. This shortcoming can make the performance of procedures that depend on the precise movement of a medical device within the region of interest difficult and cumbersome to perform.

Generally, marker devices for marking the medical device that are visible in ultrasound are known and can be utilized to visualize the medical device in the ultrasound image. However, markers which are visible in ultrasound, in particular, reflect respective ultrasound signals, can often lead to distortions and imaging artifacts that do lead to a decrease in the image quality of the ultrasound image. Thus, a solution would be advantageous that allows to monitor a medical device in an ultrasound image without having an impact on the quality of the ultrasound image.

SUMMARY

The invention is defined by the independent claims. Dependent claims represent beneficial embodiments.

Various embodiments of the present invention provide a medical microdevice, a reading system for reading a signal from the medical microdevice, a registration apparatus, a registration method and a computer program product that allow for tracking a medical device in an ultrasound image while maintaining the quality of the ultrasound image.

Some embodiments of the present invention a medical microdevice for use inside a mammal, wherein the microdevice allows for measuring a location of the microdevice in space, wherein the microdevice comprises a casing, and within the casing a magneto mechanical resonator is located, wherein the magneto mechanical resonator comprises: a) at least two magnetic objects providing a permanent magnetic moment, wherein the magneto mechanical resonator is adapted to transduce an external magnetic or electromagnetic excitation field(-s) from a mechanical movement of the at least two magnetic objects relative to each other to generate a periodically changing magnetic response field, and b) a pressure sensitive element connected to at least one of the magnetic objects, wherein the pressure sensitive element is configured to be induced by an external ultrasound signal, and wherein as a result of such inducement, the periodically changing magnetic response field is changed, and a movement of the magnetic objects is created.

Since the medical microdevice comprises a pressure sensitive element arranged such that an external ultrasound signal induces an additional movement of the magnetic objects such that the periodically changing magnetic response field is changed in dependency of the external ultrasound signal, it is not only possible to determine a location of the microdevice using an electromagnetic reading system but also to determine when an ultrasound signal is transmitted in the direction of the microdevice. This allows to determine a registration between the electromagnetic reading system of a medical microdevice and the ultrasound system such that the location determined for the medical microdevice can be integrated into the ultrasound image very accurately. Moreover, the medical microdevice is small enough to be integrated into any medical tool and thus allows to very accurately determine the position of the medical tool in the ultrasound image. Furthermore, since the medical microdevice only passively detects the ultrasound signal and changes the electromagnetic signal transmitted by the microdevice instead of changing the ultrasound signal itself, the ultrasound signal and thus the ultrasound image are not affected by the presence of the microdevice. Thus, the microdevice allows to very accurately track the position of the medical tool in an ultrasound image without affecting the ultrasound image.

Generally, microdevices refer to devices that are smaller than 1 millimeter in at least one spatial direction. In some embodiments, the medical microdevice is smaller than 1 millimeter in at least two orthogonal spatial directions. The medical microdevice may be smaller than 1 millimeter in all spatial directions, i.e. in each spatial direction. In an embodiment, the medical microdevice comprises a size that allows it to be introduced into a circulatory system or a cavity in the body of a human being. However, even smaller sizes are possible for the medical microdevice.

The casing can be any casing surrounding the magneto mechanical resonator and can be adapted in accordance with a specific application of the microdevice. The casing can comprise a coating referring in particular to a biocompatible coating. Moreover, the casing can be provided as part of a medical device into which the microdevice is integrated. For example, a part of the casing of the medical device or tool can form at least a part of the casing of the microdevice. Generally, the casing is adapted to transmit the ultrasound signals such that the pressure sensitive element can react to the pressure difference caused by the external ultrasound signal. For example, the casing can be provided with openings or flexible parts that allows to transmit a pressure difference caused by an ultrasound signal to interact with the pressure sensitive element. Moreover, the pressure sensitive element can be arranged in contact or as part of the casing such that the ultrasound signal can directly influence the pressure sensitive element.

The at least two magnetic objects providing a permanent magnetic moment are beneficially made of a hard magnetic material allowing to keep a once introduced magnetic moment. The magnetic objects refer to neodymium magnets with a high remanence of N52, i.e. of 1.42 T. In applications in environments with a temperature of more than 80°C, for instance during ablation procedures, it is noted that the magnetic object refers to a neodymium magnet with H, SH, EH or AH characteristics according to the general neodymium magnet identification system. Also CoSm (cobalt samarium) magnets can be employed as magnetic objects.

In some embodiments, the magnetic objects comprise a spherical shape which is advantageous for improving a reliability of the medical microdevice. However, the magnetic object can also be provided in other shapes, for instance, in a cylindrical shape. Moreover, the magnetic objects can have two different shapes, for example, one magnetic object can comprise a spherical shape while another magnetic object can comprise a cylindrical shape.

The magneto mechanical resonator is adapted to transduce an external magnetic or electromagnetic field into a mechanical movement of the least two magnetic objects relative to each other. In particular, the external magnetic or electromagnetic excitation field refers to an oscillating field comprising a constant or a chirped frequency for exciting the mechanical movement of the at least two magnetic objects with respect to each other. The mechanical movement can refer to any movement that moves at least one of the magnetic objects with respect to the other magnetic objects. For example, the mechanical movement can refer to a rotation of a magnetic object relative to other magnetic objects or to a linear movement away or towards other magnetic objects. In some embodiments, one of the least two magnetic objects is fixed with respect to the casing, for example, by fixedly attaching the magnetic object to the casing, whereas the other magnetic object is arranged such that it can move relative to the fixed magnetic object. In an example embodiment one of the at least two magnetic objects is arranged such that it provides a restoring force to another of the at least two magnetic objects if the other of the at least two magnetic objects deviates from an equilibrium position. In this case it is beneficial that the mechanical movement of the at least one of the at least two magnetic objects refers to a rotational movement and the restoring force refers to a restoring torque provided to the respective moving magnetic object. However, the restoring force can also be provided by a restoring force providing element like a spring attached to one of the at least two magnetic objects. Generally, the arrangement of the at least two magnetic objects in the magneto mechanical resonator causes a relative movement of the at least two magnetic objects that generates a periodically changing respond field. Based on the periodically changing magnetic respond field a respective readout system can utilize the external magnetic or electromagnetic excitation field and determine the location of the medical microdevice with respect to the readout system.

The magneto mechanical resonator further comprises a pressure sensitive element. The pressure sensitive element is arranged such that an external ultrasound signal induces an additional movement of the magnetic objects such the periodically changing magnetic response field is changed in dependency of the external ultrasound signal. Beneficially, the pressure sensitive element is arranged such that it causes a change in the distance between the at least two magnetic objects as additional movement of the magnetic objects. Since a change in the distance as additional movement changes the interaction between the two magnetic objects, also the periodically changing magnetic response field is changed depending on the external ultrasound signal. However, the pressure sensitive element can also be arranged such that it changes a rotation movement of the magnetic object, for instance, induces an additional rotation or hinders a rotation of at least one of the magnetic objects. Generally, the pressure sensitive element is configured to be sensitive to the pressure more in particular, the pressure differences, induced by the external ultrasound signal in the environment of the pressure sensitive element. Beneficially, the pressure sensitive element is configured to be sensitive to the quadratic terms of the pressure field caused by the ultrasound, wherein physically the quadratic terms refer to a pushing force induced into the environment of the pressure sensitive element by the absorbed or reflected ultrasound energy. In particular, it is beneficial that the pressure sensitive element is configured to cause the additional movement when subjected to a pressure difference lower than 0.2 mbar, more beneficially lower than 0.05 mbar and even more beneficially lower than 0.01 mbar. Beneficially, the pressure sensitive element is arranged such that a frequency of the additional movement induced by the external ultrasound signal is smaller than a frequency of the ultrasound signal. In particular, the dominant Fourier component of the additional movement is a smaller frequency than the frequency of the ultrasound signal.

In an example embodiment the casing and the pressure sensitive element are configured such that the pressure difference caused by the external ultrasound signal at different parts of the casing causes the additive movement. Arranging the pressure sensitive element and configuring the casing such that a pressure difference at different parts of the casing causes the additional movement allows to very exactly determine the pressure difference on the respective parts of the casing. Since generally the pressure difference caused on different parts of a casing relates to the direction at which the external ultrasound signal meets the microdevice, the direction of the external ultrasound signal with respect to the microdevice orientation can be derived from a change in the magnetic response filed caused by the additional movement. Thus, this embodiment allows not only to determine when an ultrasound signal meets the microdevice but also from which direction the ultrasound signal is coming with respect to the orientation of the microdevice. Beneficially, in this embodiment, the casing comprises at least two openings, wherein the pressure sensitive element is arranged between the at least two openings such that the pressure sensitive element experiences at two opposing sides a pressure difference in the presence of an external ultrasound signal. Generally, the openings refer to parts of the casing that allow to transmit a pressure provided at the casing into an inner part of the casing. Thus, the openings can be completely free of any material and can provide a direct fluidic contact between the outsides and the insides of the casing. However, it is beneficial that the openings are provided with a flexible membrane that allows to transmit a pressure applied at a casing inside the casing without allowing a direct contact of the insides of the casing with the outsides of the casing. In an example embodiment four openings are provided, wherein two of the openings are provided on each side of the pressure sensitive element respectively. Providing four openings allows for an accurate and fast pressure adaptation of the inside pressure to the outside pressure cause by the ultrasound signal at the casing of the microdevice. Thus, the detection of the ultrasound signal and the direction of the ultrasound signal becomes even more accurate.

In an embodiment, the pressure sensitive element is a flexible membrane, and wherein one of the magnetic objects is attached to the flexible membrane such that a movement of the flexible membrane causes a movement of the magnetic object. In some embodiments, the flexible membrane is formed by a flexible material, in particular, a rubber material like latex or a silicone but allows for a fast and flexible movements of the flexible membrane in reaction to the applied pressure. Beneficially, the flexible membrane is configured to flex at pressures below 0.2 mbar, more beneficially, 0.05 mbar, even more beneficially, below 0.01 mbar. Generally, the magnetic object can be attached indirectly to the flexible membrane via any kind of attachment, for instance, by an attaching filament, a holding structure, a bearing, et cetera. Moreover, the magnetic object can also be directly attached to the flexible membrane, for example, by integrating the magnetic object into the flexible membrane. In case the magnetic object is directly attached to the flexible membrane, in particular, integrated into the flexible membrane, the magnetic object only moves with the movements of the flexible membrane such that it is further beneficial in this embodiment that the other magnetic object provides the movement that causes the magnetic response field, for example by rotating relative to the magnetic object attached to the membrane. The movement of the flexible membrane caused by the ultrasound signal then causes a change in the relative movement between the two magnetic objects leading to a change in the forces between the two magnetic object and thus to a changed response field. Thus, a movement of the flexible membrane causes in this embodiment a change in the periodically changing response field that depends on the external ultrasound signal.

Some embodiments of the present invention a medical device for use during a surgical procedure under ultrasound guidance comprising a medical microdevice as described above are presented. In some embodiments, the medical device comprises a tip adapted such as to have the microdevice attached thereto. In some embodiments, the medical device may comprise one or more of an interventional device or an implant, in particular an electrical implant and/or an orthopedic implant. In some embodiments, the medical device may particularly comprise one or more of: a surgical instrument, an imaging probe, an endoscope, a bronchoscope or an ingestible pill. Alternatively or additionally, the medical device may comprise one or more of a catheter, a wire, in particular a guidewire, a stent, one or more aneurism codings, one or more vena cava filters, a heart valve, a shunt, a needle, a wire, a tube, a stylet or a radioactive seed. In some embodiments, the medical device may have a longitudinal shape. The medical device may be adapted to have a plurality of microdevices as described herein above attached thereto, wherein the plurality of microdevices may be arranged along longitudinal axis of said medical device. Some embodiments of the present invention disclose a registration apparatus for registering an ultrasound system with an electromagnetic reading system for reading a signal from a medical microdevice as described above are presented, wherein the apparatus comprises i) an receiving interface configured to receive a) a signal indicative of a transmit direction of an external ultrasound signal transmitted by the ultrasound system and b) an electrical response signal of the medical microdevice provided by the medical microdevice in response to a magnetic or electromagnetic excitation field provided by the electromagnetic reading system, ii) a processor configured to register the ultrasound system with the reading system based on the electrical response signal and the transmit direction.

Since the registration apparatus is configured to register the ultrasound system with the reading system based on the electrical response signal of a microdevice that is configured to sense the ultrasound signal of the ultrasound system and the transmit direction, the registration can be performed very accurately even when the marker device is within the human body, or in the presence of magnetic field disturbances.

The registration apparatus is configured to register an ultrasound system with an electromagnetic reading system used for reading the signal from a medical microdevice as described above. Generally, the registration apparatus can be realized in form of any computing device, for example, by utilizing one or more processors for performing the functions of the registration apparatus. Moreover, the registration apparatus can also be realized in form of network computing, for example, utilizing cloud computing or other distributed computing techniques.

The registration apparatus comprises a receiving interface, wherein the receiving interface can be realized in any form of communicative interface for communicating with other computational units, i.e. to receive wired and/or wireless data signals. In particular, the receiving interface is configured to receive a) a signal indicative of a transmitted direction of an external ultrasound signal transmitted by the ultrasound system and b) an electric response signal of the medical microdevice provided by the medical microdevice in response to a magnetic or electromagnetic excitation field provided by the electromagnetic reading system. For example, the receiving interface can be configured to be communicatively coupled with the storage unit on which the respective signals are already stored. However, the receiving interface can also be communicatively coupled directly to the ultrasound system and/or the electromagnetic reading system for receiving the respective signals directly from the systems providing these signals. The signals can be provided and received in form of any digital or analogue signal that allows to determine the information coded in the signal as defined above.

Generally, the ultrasound system can be any ultrasound system, for example a handheld ultrasound system or an automatic ultrasound system that is configured to provide and transmit an ultrasound signal into a region of interest of a patient. An ultrasound system transmits an ultrasound signal into a distinct clearly defined region of the patient, for example, utilizing a fan beam, stencil beam or cone beam, wherein a region of interest is scanned by the ultrasound by repeatedly changing the direction into which the ultrasound signal in the region of interest is transmitted. Thus, providing the transmit direction with respect to a known point in space, for example, the region of interest or the position of the ultrasound transducer allows to clearly define the space covered by the ultrasound signal at any given time.

Generally, an electromagnetic reading system for reading a signal from a medical microdevice comprises one or more coils for generating and/or receiving electromagnetic fields. In particular, an electromagnetic reading system for reading a signal from a medical microdevice as described above comprises at least one coil that is configured for providing the magnetic or electromagnetic excitation field for exciting the medical microdevice and one or more coils that are configured for receiving the electrical response signal of the medical microdevice. The electrical response signal of the medical microdevice is generally indicative of the location of the medical microdevice for example, a direction of the electromagnetic excitation field and a response time of the electrical response signal can be utilized to determine the location of the medical microdevice. Moreover, if more than one coil is utilized by the reading system also a comparison of the electrical response signals received by each of the different coils allows to derive a location of the medical microdevice. Thus, the electrical response signal allows to determine a location of the medical microdevice very accurately. Moreover, since the medical microdevice as described above is configured to provide an electrical response signal that changes with the presence of an ultrasound signal at the medical microdevice, it can also be determined very accurately based on the electrical response signal whether or not the medical microdevice is subjected at any given time to an ultrasound signal. Thus, based on the electrical response signal and the transmit direction of the ultrasound signal the processor can be configured to register the ultrasound system with the reading system. In this context the registration refers to determining a function that allows to transform a location of the medical microdevice determined in a coordinate system of the electromagnetic reading system into a location in the coordinate system of the ultrasound system. Thus, if the ultrasound system and the electromagnetic reading system are registered a location of the medical microdevice determined by the electromagnetic reading system is also directly known with respect to the ultrasound system. Accordingly, the location of the medical microdevice in the ultrasound image can be determined and provided to a user.

In an example embodiment the processor is further adapted to determine a presence or absence of an external ultrasound signal at the microdevice based on the response signal and a location of the medical microdevice relative to the electromagnetic reading system based on the response signals, and to register the ultrasound system with the reading system based on a transmit direction of the external ultrasound signal, the determined location and the determined presence or absence of the external ultrasound signal. Based on the determined location and based on the determined presence or absence of the external ultrasound signal it can be determined at which point in time the ultrasound signal is received by the medical microdevice and thus at which point in time the ultrasound signal is directed at the location of the medical microdevice. Moreover, since the location of the medical microdevice in the coordinate system of the reading system and the direction of the ultrasound signal in the coordinate system of the ultrasound system is known the two systems can be registered in at least one direction. Moreover, if the ultrasound signal refers to a stencil beam that covers substantially a line area in the region of interest the registration can also be performed in two directions. The further information with respect to the third coordinate can then be provided, for instance, based on respective pre-knowledge, for example, during a calibration procedure the distance between the ultrasound transducer and the medical microdevice can be predetermined or measured directly. The position of the ultrasound transducer in the coordinate system of the reading system is provided. For example, the position can be indicated by a user or during a calibration procedure the medical instrument comprising the marker in a known relative position in the instrument can be used to determine the position of the ultrasound system in the coordinate system of the reading system, for instance, by touching the medical instrument to a predetermined part of the ultrasound system. In an embodiment the ultrasound system can be configured to comprise an additional marker, wherein in this case the reading system is adapted to determine the location of the additional marker based on a signal of the additional marker, wherein the registration is then further based on the determined location of the additional marker. The additional marker allows for measuring a location of the additional maker in space. Since the additional marker is provided as part of the ultrasound system and not provided within the human body, the marker is not subjected to the same size restrictions as the microdevice. Thus the additional marker can be realized as any known marker that provides an electromagnetic signal in the presents of a changing electromagnetic field or can even be realized as an active electromagnetic source. For example, the marker can comprise an LC resonator or a sending coil. However, the additional marker can also be realized as an additional microdevice, wherein the additional microdevice also comprises a magneto mechanical resonator, wherein the magneto mechanical resonator comprises a) at least one magnetic object providing a permanent magnetic moment, wherein the magneto mechanical resonator is adapted to transduce an external magnetic or electromagnetic excitation field into a mechanical movement of the at least one magnetic object such that a periodically changing magnetic response field is generated. For example, the mechanical resonator of the additional microdevice can be similar to the mechanic resonator of the microdevice. However, in this embodiment it is not necessary that the additional microdevice comprises an ultrasound sensing possibility. Thus in the additional microdevice parts referring to this additional sensing possibility can be omitted. Based on the determined position of the additional marker on the ultrasound system the reading system can be registered in all three directions, in particular, during a calibration procedure in which the ultrasound system is positioned at different positions relative to the microdevice. However, in some embodiments it can also be suitable to register only in one or two directions. For example, if a coordinate of the third direction, in particular, a distance between the microdevice and the ultrasound system is determined and known due to the nature of the medical procedure or if an accurate location determination in one direction is not necessary for the success of the procedure. However, it is beneficial that the processor determines a distance between the source of the ultrasound signal provided by the ultrasound system and the microdevice based on the response signal, and to register the ultrasound system with the reading system further based on the determined distance. The distance between the source of the ultrasound signal and the microdevice can be determined based on the electrical response signal, for example, based on the strength of the parts of the response signal that indicates the presence of the ultrasound signal. Since the ultrasound signal strength also depends on the distance between the source and the microdevice, and since the response of the microdevice to the ultrasound signal also depends on the strength of the ultrasound signal reaching the microdevice, the distance between the microdevice and the ultrasound transducer can be determined. This allows for a registration in which a calibration step is omitted and the registration is directly performed with a microdevice placed in the region of interest.

Furthermore, to increase the accuracy of the registration, it is preferred that the processor is further adapted to determine a direction of the ultrasound signal relative to the microdevice, i.e. to determine the direction under which the ultrasound signal reaches the microdevice. Since the pressure differences caused in the pressure sensitive element of the microdevice generally depends on the direction under which the ultrasound signal reaches the microdevice, in particular, the pressure sensitive element, the response signal is indicative also of the direction under which the ultrasound signal reaches the microdevice. Thus, the response signal can also be utilized to determine this direction. This allows in particular during the registration to further determine a relative orientation of the microdevice at the location of the microdevice and thus increases the accuracy not only of the registration but also of the location determination of the microdevice.

In an example embodiment the registration apparatus further comprises an output interface configured to provide an output signal adapted to cause a visualization of a location of the microdevice in an ultrasound image based on the registration. For example, the location of the microdevice can be visualized by utilizing a virtual marker or other virtual highlighting that allows a user to perceive the determined location of the microdevice in the ultrasound image. Moreover, based on the known location of the microdevice and further based on a known relation between the microdevice and, for instance, the medical device, also a location of the medical device can be visualized in the ultrasound image.

Some embodiments of the invention disclose a reading system for reading a signal from a medical microdevice as described above and registering the reading system to an ultrasound system are presented, wherein the reading system comprises i) a field generator for generating a magnetic or electromagnetic excitation field for inducing a mechanical movement of a magnetic object of a magneto mechanical resonator of the medical microdevice, wherein the movement of the magnetic object generates a periodically changing response magnetic field, ii) a transducer for sensing and transducing the response magnetic field into an electrical response signal, iii) an apparatus as described above.

Generally, the field generator can refer to a field generator that can generate a periodically changing magnetic or electromagnetic field of a predetermined frequency. The transducer can refer to one or more magnetic coils that allow to transduce a magnetic field into an electric current that can be regarded as the electrical response signal. The processor is adapted to determine a location and/or a physical parameter and/or a change of a physical parameter in an environment of the medical microdevice based on the electrical response signals. In an example embodiment, the field generator comprises at least one air-core coil that is adapted to generate an excitation field between 1 kHz and 200 kHz, wherein the transducer is adapted to sense and transduce a magnetic signal of up to more than twice the frequency of the excitation field. In some embodiments, the transducer comprises at least one or beneficially more than three, air-core coils made from copper or aluminum.

Some embodiments of the invention disclose a computer implemented registration method for registering an ultrasound system with an electromagnetic reading system for reading a signal from a medical microdevice as described above are presented, wherein the method comprises i) receiving a signal indicative of a transmit direction of an external ultrasound signal transmitted by the ultrasound system, ii) receiving an electrical response signal of the medical microdevice provided by the medical microdevice in response to a magnetic or electromagnetic excitation field provided by the electromagnetic reading system, iii) registering the ultrasound system with the reading system based on the electrical response signal and the transmit direction.

In an example embodiment the registration method as described above, further comprises determining a presence or absence of an external ultrasound signal at the microdevice based on the electrical response signal and a location of the medical microdevice relative to the electromagnetic reading system based on the electrical response signals, and registering the ultrasound system with the reading system based on a transmit direction of the external ultrasound signal, the determined location and the determined presence or absence of the external ultrasound signal. Moreover, the method further comprises determining a distance between the source of the ultrasound signal provided by the ultrasound system and the microdevice based on the electrical response signals, and registering the ultrasound system with the reading system further based on the determined distance. The registration method as described above, further comprising providing an output signal adapted to cause a visualization of a location of the microdevice in an ultrasound image based on the registration.

Some embodiments of the invention disclose a computer program product for causing the registration apparatus as described above to perform the method as described above are presented, when the computer program product is run on the registration apparatus.

It shall be understood that embodiments of the present invention can also include any combination of the dependent claims or above embodiments with the respective independent claim.

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

BRIEF DESCRIPTION OF THE DRAWINGS

In the following drawings:

Fig. 1 shows schematically and exemplarily a medical system comprising a microdevice and an apparatus for registering an ultrasound system and a reading system of a medical microdevice, Fig. 2 shows schematically and exemplarily a method for registering an ultrasound system and a reading system of a medical microdevice,

Fig. 3 shows schematically and exemplarily a medical microdevice integrated into a medical tool, and

Fig. 4 shows schematically and exemplarily a calibration procedure for registering the ultrasound system and the reading system.

DETAILED DESCRIPTION OF EMBODIMENTS

Fig. 1 shows schematically and exemplarily an embodiment of a medical system comprising a medical microdevice. The medical system 100 comprises an ultrasound system 130, a medical microdevice 160, and an electromagnetic reading system 140 for reading out the microdevice. Further, the medical system 100 comprises an apparatus 110 for registering the ultrasound system 130 and the electromagnetic reading system 140 and further an output unit 120 for providing an ultrasound image to the user indicating the position of the microdevice 160 in the ultrasound image.

In this, exemplarily embodiment a microdevice 160 is placed within a patient 150 placed on a patient table 151. The medical microdevice 160 is generally placed in a region of interest, i.e. in a region in which, for example, a surgical intervention should be performed. The medical microdevice 160 can be provided as, integrated in or attached to a medical tool that should be used in the region of interest. An example of a medical microdevice integrated into a medical tool is shown in Fig. 3. The medical tool 300 comprising the integrated medical microdevice is in this case realized in form of a medical needle with a tapered end 301. However, the medical tool 300 can generally be realized in any other form, for instance, as a catheter, guidewire, ablation element, etc. In the example shown in Fig. 3 the medical microdevice is directly integrated into the medical tool 300 such that a part of the casing is a part of a wall, for instance, an outer wall, of the medical tool 300. However, in other embodiments, the medical microdevice can also be provided with a casing that is not integrated into a housing of the medical tool and can for instance then be attached to a part of the medical microdevice. Within the casing 302 the medical microdevice comprises a magneto mechanical resonator that comprises in this example two magnetic objects 312, 311. The two magnetic objects 312, 311 are realized as magnetic spheres and are arranged within the casing 302 such that the magnetic poles of the two magnetic objects 312, 311 are in anti-parallel configuration, i.e. the positive pole of the magnetic object 312 faces the negative pole of the magnetic object 311. This configuration provides a restoring force acting on a magnetic object if it leaves its position. Generally, in this example the magnetic objects 312, 311 are shown as spheres, however, the magnetic objects can also be realized in other shapes, for example, as cylinders, ellipsoids, or any other shape that allows to provide a configuration in which the two magnetic objects 312, 311 provide a restoring force if one magnetic object is moved. In this example, the magnetic object 312 is attached to the casing 302 using a filament 314 that allows the magnetic object 312 to rotate around an axis formed by the filament 314. Since a rotation of the magnetic object 312 with respect to the magnetic object 311 causes a restoring force to act on the magnetic object 312, a movement of the magnetic object 311 will lead to a periodic movement around the neutral position shown in Fig. 3 and thus will lead to the generation of an electromagnetic field. Accordingly, by providing an external magnetic or electromagnetic excitation field to the medical microdevice that induces a rotation in the magnetic object 312 a periodically changing magnetic response field is generated.

In this exemplary embodiment of the medical microdevice the magnetic object 311 is attached to a pressure sensitive element 313 realized as a flexible membrane. In the embodiment shown in Fig. 3 the magnetic object 311 is integrated into the flexible membrane 313, however, the magnetic object could also be simply attached to the flexible membrane. Generally, the flexible membrane 313 comprises a flexibility that allows the flexible membrane 313 to react to a pressure difference on both sides of the flexible membrane 313, in particular, by moving in the direction with a lower pressure. Thus, a pressure induced movement of the magnetic object 311 will cause a distance change between the two magnetic objects 311, 312 and thus lead to a difference in the restoring force acting on the rotating magnetic object 312. Due to the change in the restoring force also the movement, in particular, the frequency of the rotational movement, of the magnetic object 312 will change leading to a change in the periodically changing magnetic response field. In particular, for this application of the medical microdevice the flexible membrane 313 is configured and arranged such that a pressure difference induced by an external ultrasound signal will cause the movement of the flexible membrane 313. In particular, it is preferred that the flexible membrane 313 is configured to be ultrasound sensitive by reacting to the quadratic terms of the pressure field, i.e. to the pushing force induced by an absorbed or reflected ultrasound energy and generally referring to the acoustic radiation pressure of the ultrasound signal.

Generally, the acoustic radiation pressure acting on an object can be calculated according to P = wherein P is a pressure, I is the incident power density, i.e. an incident power per unit area, of the incident radiation and c is the radiation velocity. For a generally known ultrasound transducer used in medical applications under an average distance between the region of interest and the transducer a good estimate for the incident power density is I = 15kW /m² and the velocity can be estimated as c = 1500m/s. From this estimate it follows that the acoustic radiation pressure of an ultrasound transducer in a medical application can be estimated as P = 0. Imbar. Thus, a flexible membrane is configured to react with a movement of the magnetic object for pressure differences beneficially below 0.05 mbar, even more beneficially, below 0.01 mbar. For example, the flexible membrane can be made of a rubbery material like a silicone or latex and the signals of the flexible membrane can then be adjusted in order to allow for the reaction to the respective pressure difference.

In order to allow the pressure difference induced by the ultrasound signal to induce a movement of a flexible membrane, the pressure has to be transmitted through the casing 302 to the pressure sensitive flexible membrane 313. In this exemplarily embodiment this is realized by providing openings 304, 305 in the casing of a medical microdevice. The openings 304, 305 are provided such that the interior of the casing 302 surrounding the magnetic object 311 is in a fluidic contact with a surroundings of the casing 302. For example, the openings 304, 305, can be directly open. However, it is preferred in order to avoid bodily fluids to enter the medical microdevice, that the openings 304, 305 are closed off, for example, also with a flexible membrane that allows to transmit a pressure from the outside of the casing 302 to the inside of the part of the casing 302 surrounding the magnetic object 311. Moreover, in this exemplarily embodiment the two medical objects 311, 312 are separated by a separator 303. Accordingly, the pressure transmitted into the casing 302 can only act on the pressure sensitive membrane 313 and thus only on magnetic object 311, while the filament 314 and the magnetic object 312 will not be influenced by any pressure differences. This allows for an easier calibration of the medical microdevice and a more accurate measurement of the pressure difference induced by the ultrasound signal.

The microdevice described above can for instance be utilized as a microdevice 160 shown in Fig. 1. The ultrasound system 130 can refer to any known medical ultrasound system and comprises an ultrasound transducer that provides ultrasound signals into a region of interest in the patient in which the medical microdevice 160 is positioned. Generally, the ultrasound system 130 provides ultrasound signals in form of pencil beams, fan beams, or cone beams, wherein based on the position of the ultrasound system 130 a direction of a currently emitted ultrasound signal relative, for instance, to the region of interest, the position of the ultrasound device 130 or any other fixed position that can define a coordinate system, can be determined. The ultrasound system 130 is then configured to provide a signal to the apparatus that is indicative of a current direction in which the ultrasound signal is provided by the ultrasound transducer.

The system further comprises the electromagnetic reading system 140 for reading out the medical microdevice. The reading system 140 comprises at least a field generator for generating the magnetic or electromagnetic excitation field that can be used to excite the microdevice 160. Further, the reading system 140 comprises one or more transducers that can measure the generated response magnetic field of the medical microdevice and transduce the generated response magnetic field into an electrical response signal. In some embodiments, the field generator can also be utilized as transducer in addition or alternatively to the other transducers described above. The transducers can be realized as coils transducing the response magnetic field generated by the medical microdevice 160 into an electrical response signal. The electrical response signal can then be provided to a processor that is adapted to process the electrical response signals, for instance, for localizing the medical microdevice 160 or for determining a physical parameter measured by the medical microdevice in its environment. In particular, the processor can be adapted to compare the response signal of different transducers and based on this comparison use a triangulation algorithm to determine the location of the medical microdevice. Moreover, the processor can be adapted to analyze a frequency spectrum of the response signal and to compare the frequency spectrum to a frequency spectrum that is stored already, for instance, from a previous time span or from a calibration measurement. Based on this comparison the processor can then determine a physical parameter or a change in a physical parameter in the environment of the medical microdevice. However, also other methods can be utilized for localizing the medical microdevice and/or for determining a physical parameter based on the response signals.

Moreover, the processor can be configured to determine based on the response signal generated by the medical microdevice the presence of an ultrasound signal. For example, in a previous calibration procedure the signals changes caused by an ultrasound signal meeting the medical microdevice 160 at different angles and at different distances can be recorded and the respective response signals can be compared to current response signals of the medical microdevice. Based on the comparison it can be determined when an ultrasound signal reaches the medical microdevice. Moreover, if the medical microdevice 160 is further configured such that the flexible membrane reacts differently to different directions under which the ultrasound signal meets the medical microdevice, also this direction can be determined by the processor based on the response signal provided by the medical microdevice 160. Moreover, since the radiation pressure of the ultrasound signal provided to the medical microdevice depends on the distance between the medical microdevice 160 and the ultrasound transducer 130, also this distance can be determined, for example, by the processor, based on the electromagnetic response signal of the medical microdevice 160. Generally, the intensity of an ultrasound beam changes with distance in a known way. For example, for a point source, it decreases with the square of the distance, if there is negligible absorption. However, in reality, the situation can be more complicated, if the ultrasound field is shaped by the ultrasound transducer and does not refer to a simple point source. However, the shape of the ultrasound beam is generally known and can be provided, for example, based on a specification or based on calibration measurements for an ultrasound system. Based on this knowledge the distance from the ultrasound transducer to the microdevice can be calculated. The accuracy of the distance calculation can further be increased if the attenuation and diffraction/scattering of the ultrasound signal by the tissue is taken into account. For example, a respective estimation for common soft tissues can be found in literature for a specific ultrasound frequency and tissue type. Based on the attenuation and diffraction/scattering estimate and based on the shape of the ultrasound beam for a given ultrasound probe, a relative accurate prediction, i.e. theoretical intensity, for the ultrasound intensity over depth, i.e. distance, can be derived. As the microdevice measures the ultrasound intensity, it is possible to reconstruct the depth, i.e. distance, by comparing the measured intensity with the theoretical intensity and determining the distance based on the comparison, e.g. by selecting the distance that matches best. Furthermore, to further increase the accuracy, a dependency of the measured intensity by the microdevice on the orientation of the microdevice relative to the angle of the ultrasound field can be taken into account. This angle can be determined, for example, from a known position of the microdevice relative to the reading system and a position of an additional marker attached to the ultrasound probe. However, also other possibilities for determining a position of the ultrasound probe in a coordinate system of the reading system can be utilized, for example, touching the microdevice to the ultrasound device, etc. If the reading system does not comprise a processor in itself it can directly provide the electromagnetic response signal received from the medical microdevice 160 to the apparatus 110 and the processor 112 of the apparatus 110 can be configured to determine the location of the medical microdevice and optionally also the distance between the medical microdevice and the ultrasound transducer and/or the direction from which the ultrasound signal meets the medical microdevice 160 based on the electromagnetic response signal provided by the reading system 140. However, if the reading system 140 comprises a processor that can calculate this measures, the reading system 140 can provide a signal to the apparatus 110 that is indicative of the already calculated measures. In this case it can be regarded that the processor 112 of the apparatus 110 and the processor of the reading system 140 perform the function of registering the ultrasound system and the reading system 130, 140 together in a distributed computing.

The apparatus 110 is configured for registering the ultrasound system 130 with the electromagnetic reading system 140. In particular, a registration of the two systems refers to determining a function that allows to calculate based on the location of the medical microdevice determined by the reading system 140 the location of the medical microdevice 160 in the ultrasound image of the ultrasound system 130. In particular, this function refers to a coordinate transformation that transforms the coordinates of the location of the medical microdevice 160 in the coordinate system of the reading system 140 to the coordinate system of the ultrasound image, i.e. to the coordinate system of the ultrasound system 130. For this the registration apparatus 110 comprises a receiving interface 111 that can be realized as any form of communicative interface that allows to receive wired or wireless signals from the ultrasound system 130 and the reading system 140. Accordingly, the receiving interface can receive a signal from the ultrasound system that is indicative of the direction of the ultrasound signal. For example, the signal can be indicative of a current direction of the ultrasound signal or can comprise a sequence of directions of the ultrasound signal associated with the respective time at which the ultrasound signal is provided in the respective direction. Further, the receiving unit can receive accordingly from the reading system 140, as described above, a response signal of the medical microdevice 160 or directly the determined location of the medical microdevice and optionally also the distance between the medical microdevice and the ultrasound transducer and/or a direction under which the ultrasound signal meets the medical microdevice 160. Moreover, the signal received by the receiving interface can also be indicative when the ultrasound signal meets the medical microdevice 160. For example, the signal can be indicative whether or not currently the medical microdevice 160 is subject to an ultrasound signal, and/or can be indicative of the times at which the medical microdevice was subject to the ultrasound signal. However, as also described above, the receiving interface 111 can also receive a signal that is indicative of the electrical response signal of a medical microdevice, wherein in this case the processor 112 is configured to determine the above measures.

The processor 112 is then configured to register the ultrasound system with the reading system based on the response signal, in particular, based on the measures derived from the response signal and the transmit direction. In particular, in a first step the processor can be configured to determine times at which the medical microdevice 160 is subjected to the ultrasound signal. The processor can then utilize the transmit direction of the ultrasound signal from these times since at these times the position of the medical microdevice lies within the region covered by the ultrasound signal transduced in the transmit direction. Further, the processor can be configured to utilize the location of the medical microdevice 160 determined based on the response signal to determine the registration. In particular, based on the location and the direction of the ultrasound signal a registration in at least one direction, if the ultrasound signal is a pencil beam also in two directions, can be performed. A registration in all three directions can be based on further information. For example, during a calibration procedure the medical microdevice can be placed in a predetermined distance from the ultrasound transducer and can then be placed in different locations in order to register all three directions. However, if during the interventional procedure the response signal also provides information about the distance to the ultrasound transducer and/or the direction under which the ultrasound signal meets the medical microdevice 160, the calibration procedure can be omitted, and the directly derived information during the interventional procedure can be utilized for registering the ultrasound system and the reading system in all three directions.

A preferred calibration procedure that can be utilized for determining the registration is described in the following based on Fig. 4. In this embodiment, the ultrasound system 420 comprises an additional marker 421 that allows to determine the location of the ultrasound system in the coordinate system of the reading system. The additional marker can be any device that provides a signal measurable by the reading system. For example, the marker can comprise an LC resonator that responds to the changing electromagnetic field provided by the reading system and generates a respective response signal that can be measured by the reading system. However, the marker can also be an active marker that generates an electromagnetic signal measurable by the reading system independent of an external magnetic or electromagnetic field. Beneficially the marker is realized as a microdevice comprising a magneto mechanical resonator similar to the magneto mechanical resonator of the microdevice. However, the magneto mechanical resonator is beneficially only adapted for allowing a localizing of the additional marker without providing an ultrasound detectability. Beneficially, the ultrasound system, in particular the ultrasound probe 420, can be equipped with an additional marker capable to be localized in 6 degrees of freedom relative to the reading system. When the position and optionally orientation of the microdevice and additional marker are known and if further the position and beam angle of the ultrasound system is known, generally a microdevice position can be computed relative to the ultrasound image. This allows for a position indication of the microdevice in an ultrasound image without determining the absence or presence of the ultrasound signal at the location of the microdevice. However, the position and orientation of the microdevice relative to the additional marker can often not be determined with sufficient precision or can change during an interventional procedure due to changes in the electromagnetic field used for determining the positions of the microdevice and the marker. For example, metallic objects near a patient can disturb the electromagnetic field and it might not always be possible to ensure that a position of the object and thus the disturbance does not change during the interventional procedure. In these cases it is advantageous if a fast and easy way can be provided that allows to again determine the position of the microdevice in the ultrasound image very accurately. Therefore, it is preferred to register the ultrasound system and the reading system in a fast and easy calibration procedure that can be repeated, if necessary during an interventional procedure. In an exemplary calibration procedure, the user positions the ultrasound probe 420 with the additional marker 421 relative to the microdevice 410, for instance, on a surface 400 of the patient or a calibration dummy. The ultrasound beam 422 can then be angled in a way that the microdevice 410 detects the ultrasound signal. The detection of the ultrasound signal at the first position 440 together with the information on the locations of the microdevice 410, the additional marker 421 and the angle, i.e. direction, of the ultrasound beam 422 can then be stored. This procedure can then be repeated at least two times at different positions of the ultrasound probe 420, for example, the same information can also be determined for a second position 450 of the ultrasound probe 420. The registration processor can then be configured to optimize the beam starting point, or line for an array transducer, position and the beam angle or beam plane angle for a 2D array, relative to the additional marker in the coordinate system of the reading system 430 to fit all the measurements. The optimization then results in a registration that allows to display the position of the microdevice in the ultrasound image, based on the microdevice position and the additional marker position. Moreover, if the ultrasound probe is not moved during the interventional procedure the registration allows even to only use the microdevice position for determining and displaying the microdevice in the ultrasound image.

Based on the registration the location of the medical microdevice 116 in the ultrasound image 120 provided by the ultrasound system 130 can be determined utilizing the location of the medical microdevice 160 as determined by the reading system 140. Thus, the apparatus 110 can utilize the registration result to determine the location of the medical microdevice 160 in the ultrasound image and provide this location to a display 120. Further, the ultrasound system 130 can provide the ultrasound image to the display 120 and the display 120 can then display the ultrasound image showing the location of the medical microdevice 160. In particular, a marker or other virtual representation of the medical microdevice can indicate the location of the medical microdevice in the ultrasound image and thus in the region of interest. Since in most cases the medical microdevice will be provided as integrated into or attached to a medical device, based on the location of the medical microdevice 160 also the location of the medical device can be indicated in the ultrasound image 120, for instance, by using a virtual representation of the medical device.

In some embodiments, instead of an ultrasound other imaging equipment can be used. A non-limiting example includes computed tomography (CT), angiography equipment, X-ray equipment, fluoroscopic X-ray equipment, magnetic resonance imaging (MRI) equipment. In some embodiments non-imaging equipment can be used instead, such as pressure equipment (during e.g., manometry), pH analysis equipment and others. Some embodiments of the present application disclose a microdevice according, wherein the external ultrasound signal causes a pressure difference, wherein the pressure difference is caused by the external ultrasound signal at different parts of the casing and/or the pressure sensitive element that causes movement of the magnetic objects.

Some embodiments of the present application disclose a microdevice wherein the casing comprises at least two openings, wherein the pressure sensitive element is arranged between the at least two openings, and wherein a pressure difference is created between the at least two openings.

Some embodiments of the present application disclose a microdevice, wherein the pressure sensitive element is a flexible membrane, and wherein one of the magnetic objects is attached to the flexible membrane such that a movement of the flexible membrane causes a movement of the magnetic object.

In a further aspect, a medical device for use during a surgical or a medical procedure performed under ultrasound guidance wherein the medical device comprises a medical microdevice is disclosed. Medical procedure could be of invasive or non-invasive nature. Surgery could refer to minimally invasive procedures.

In a further aspect a registration apparatus comprising an ultrasound system, and an electromagnetic reading system for reading a signal from a medical microdevice is disclosed. The registration apparatus comprises: a receiving interface configured to receive a) a signal indicative of a transmit direction of an external ultrasound signal transmitted by the ultrasound system and b) an electrical response signal of the medical microdevice in response to a magnetic or electromagnetic excitation field (-s) provided by the electromagnetic reading system, and one or more processors configured to register the ultrasound system with the reading system based on the electrical response signal and the transmit direction of the electrical response signal.

In some embodiments, the registration apparatus is disclosed, wherein the one or more processors are further adapted to determine a presence or absence of the external ultrasound signal at or near the microdevice based on the electrical response signal and a location of the medical microdevice relative to the electromagnetic reading system.

In some embodiments, a registration apparatus is disclosed, wherein the one or more processors are further adapted to determine a distance between the ultrasound system, and the microdevice based on the electrical response signal (-s).

In some embodiments a registration apparatus is disclosed, wherein the registration apparatus further comprises an output interface configured to provide an output signal adapted to cause a visualization of a location of the microdevice, such as a visualization of a location of the microdevice in an ultrasound image of the ultrasound system.

In a further aspect, a reading system for reading a signal from a medical microdevice comprising a magneto mechanical resonator and registering the reading system to an ultrasound system is disclosed. The reading system comprises: a field generator for generating a magnetic or electromagnetic excitation field (-s) for inducing a mechanical movement of a magnetic object of a magneto mechanical resonator of the medical microdevice, wherein the movement of the magnetic object generates a periodically changing response magnetic field, and a transducer for sensing and transducing the response magnetic field into an electrical response signal, and a registration apparatus.

In some embodiments, the reading system comprise a receiving interface configured to receive: a) a signal indicative of a transmit direction of an external ultrasound signal, and b) an electrical response signal of the medical microdevice provided by the medical microdevice in response to a magnetic or electromagnetic excitation field provided by the electromagnetic reading system, one or more processors configured to register the ultrasound system with the reading system based on the electrical response signal and the transmit direction.

In a further aspect, a computer-implemented registration method for registering an ultrasound system with an electromagnetic reading system for reading a signal from a medical microdevice is disclosed. The method comprises the steps of: receiving a signal indicative of a transmit direction of an external ultrasound signal transmitted by the ultrasound system, receiving an electrical response signal of the medical microdevice provided by the medical microdevice in response to a magnetic or electromagnetic excitation field provided by the electromagnetic reading system, registering the ultrasound system with the reading system based on the electrical response signal and the transmit direction of the electric response signal.

In some embodiments, the method further comprises determining a presence or absence of an external ultrasound signal at the microdevice based on the electrical response signal and a location of the medical microdevice relative to the electromagnetic reading system based on the electrical response signals, and registering the signal of the ultrasound system with the reading system based on a transmit direction of the external ultrasound signal.

In some embodiments, the method further comprises determining a distance between a source of the external ultrasound signal transmitted by the ultrasound system and the microdevice based on the electrical response signals, and registering the ultrasound system with the reading system further based on the determined distance.

In some embodiments, the method further comprises providing an output signal adapted to cause a visualization of a location of the microdevice.

In a further aspect, a computer program product for causing a registration apparatus to perform the method as disclosed herein is disclosed.

In a further aspect, a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method as disclosed herein is disclosed.

Fig. 2 shows schematically and exemplarily a flow chart of the method 200 for registering the ultrasound system with the reading system for a medical microdevice. The method 200 comprises a step 210 of receiving a signal indicative of the transmit direction of the ultrasound signal transmitted by the ultrasound system, for instance, ultrasound system 130. Further, the method comprises a step 220 of receiving a signal indicative of the response signal of the medical microdevice, for example, as provided by the reading system 140. Further, the method 200 comprises a step 230 of registering the ultrasound system with the reading system based on the electrical response signal and the transmit direction, for example, as already described above with respect to the apparatus 110 in detail.

Although in the above embodiments the medical microdevice was integrated into a medical tool, in other embodiments the medical microdevice can also be provided with its own casing and can then be attached to a medical tool or can be provided, for instance, as marker, in a region of interest without a medical tool.

Although in the above embodiments the medical microdevice was provided with the magnetic object attached to a filament in a magnetic object attached to a flexible membrane, in other embodiments both medical objects might be attached to flexible membranes, or to filaments. Moreover, also other attachments can be utilized like springs flexible filaments, etc.

Moreover, although in the above embodiments the response signal was provided by the magnetic objects due to a rotation of the magnetic objects in other embodiments the response signal can also be provided by other movements of the magnetic objects relative to each other, for instance, by movements periodically changing a distance between the magnetic objects or changing an orientation of the magnetic objects. Furthermore, although in the above embodiments the pressure sensitive element was provided as a flexible membrane, in other embodiments the pressure sensitive element can refer to any element that allows to introduce relative motion between the magnetic objects. For example, a pressure sensitive spring or filament or any other construction can also be utilized.

Although in the above embodiments the medical microdevice was provided with two magnetic objects, in other embodiments the medical microdevice can also be provided with more than two magnetic objects, for instance, also magnetic objects in between the two magnetic objects can be provided or at the sides of the magnetic objects in order to stabilize the movement of the magnetic objects. Furthermore, although in the above embodiments the casing was provided with two openings, in other embodiments the openings can be omitted, for example, if the casing itself is provided with a flexible material, or more than two openings can be provided. In some embodiments four openings are provided in order to allow for an accurate pressure transmitting between the outside of the casing and the inside of the casing

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art from a study of the drawings, the disclosure, and the appended 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 unit or device may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Procedures like the receiving of the signals, the registering of the systems, et cetera, performed by one or several units or devices can be performed by any other number of units or devices. These procedures can be implemented as program code of a computer program and/or as dedicated hardware.

A computer program may be stored/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.

Any reference signs in the claims should not be construed as limiting the scope.

Embodiments refer to a medical microdevice, a medical device and a registration apparatus that allow for tracking a medical device in an ultrasound image while maintaining the quality of the ultrasound image. The microdevice comprises a casing and a magneto mechanical resonator. The magneto mechanical resonator comprises at least two magnetic objects providing a permanent magnetic moment. The magneto mechanical resonator is adapted to transduce an external excitation field into a mechanical movement of the at least two magnetic objects relative to each other such that a periodically changing magnetic response field is generated. A pressure sensitive element is arranged such that an external ultrasound signal induces an additional movement of the magnetic objects such that the periodically changing magnetic response field is changed in dependency of the external ultrasound signal.

Some portions of the description are presented in terms of symbolic representations of operations on non-transient signals stored within a computer memory. These descriptions and representations are used by those skilled in the data processing arts to convey the substance of their work most effectively to others skilled in the art. Such operations typically require physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical, magnetic, or optical signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It is convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. Furthermore, it is also convenient at times to refer to certain arrangements of steps requiring physical manipulation of physical quantities as modules or code devices, without loss of generality.

However, all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system memories or registers or other such information storage devices, transmission or display devices. Portions of the present disclosure include processes and instructions that may be embodied in software, firmware, or hardware, and when embodied in software, may be downloaded to reside on and be operated from different platforms used by a variety of operating systems.

The computer system may also include a processor. The processor executes instructions to implement some, or all aspects of methods and processes described herein. The processor is tangible and non-transitory. As used herein, the term “non-transitory” is to be interpreted not as an eternal characteristic of a state, but as a characteristic of a state that will last for a period. The term “non- transitory” specifically disavows fleeting characteristics such as characteristics of a carrier wave or signal or other forms that exist only transitorily in any place at any time. The processor is an article of manufacture and/or a machine component. The processor is configured to execute software instructions to perform functions as described in the various embodiments herein. The processor may be a general- purpose processor or may be part of an application specific integrated circuit (ASIC). The processor may also be a microprocessor, a microcomputer, a processor chip, a controller, a microcontroller, a digital signal processor (DSP), a state machine, or a programmable logic device, a logical circuit, including a programmable gate array (PGA), such as a field programmable gate array (FPGA), or another type of circuit that includes discrete gate and/or transistor logic. The processor may be a central processing unit (CPU), a graphics processing unit (GPU), or both. Additionally, any processor described herein may include multiple processors, parallel processors, or both. Multiple processors may be included in, or coupled to, a single device or multiple devices. The processor can include one or more internal levels of cache, and a bus controller or bus interface unit to direct interaction with a bus.

“Memory” is an example of a computer-readable storage medium. Computer memory is any memory which is directly accessible to a processor. Examples of computer memory include RAM memory, registers, and register files. References to “computer memory” or “memory” should be interpreted as possibly being multiple memories. The memory may for instance be multiple memories within the same computer system. The memory may also be multiple memories distributed amongst multiple computer systems or computing devices. The memory may store various software applications including computer executable instructions, that when run on the processor, implement the methods and systems set out herein. Other forms of memory, such as a storage device and a mass storage device, may also be included and accessible by the processor (or processors) via the bus. The storage device and mass storage device can each contain any or all of the methods and systems discussed herein.

The computer system can further include a communications interface by way of which the computer system can connect to networks and receive data useful in executing the methods and system set out herein as well as transmitting information to other devices. The computer system further includes a video display unit as an output device by which information can be output, such as a liquid crystal display (ECD), an organic light emitting diode (OLED), a flat panel display, a solid-state display, or a cathode ray tube (CRT), for example. Additionally, the computer system includes an input device, such as a keyboard/virtual keyboard or touch-sensitive input screen or speech input with speech recognition, and a cursor control device, such as a mouse or touch-sensitive input screen or pad. The computer system also optionally includes a disk drive unit, a signal generation device, such as a speaker or remote control, and/or a network interface device.

The processes and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may also be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform one or more method steps.

The illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The illustrations are not intended to fully describe all the elements and features of the disclosure described herein. Many other embodiments may be apparent to those of skill in the art upon reviewing the disclosure.

Claims

CLAIMS:

1. A medical microdevice for use inside a mammal, wherein the microdevice allows for measuring a location of the microdevice in space, wherein the microdevice comprises a casing, and within the casing a magneto mechanical resonator is located, wherein the magneto mechanical resonator comprises: a) at least two magnetic objects providing a permanent magnetic moment, wherein the magneto mechanical resonator is adapted to transduce an external magnetic or electromagnetic excitation field(-s) from a mechanical movement of the at least two magnetic objects relative to each other to generate a periodically changing magnetic response field, and b) a pressure sensitive element connected to at least one of the magnetic objects, wherein the pressure sensitive element is configured to be induced by an external ultrasound signal, and wherein as a result of such inducement, the periodically changing magnetic response field is changed, and a movement of the magnetic objects is created.

2. The medical microdevice according to claim 1, wherein the external ultrasound signal causes a pressure difference, wherein the pressure difference is caused by the external ultrasound signal at different parts of the casing and/or the pressure sensitive element that causes movement of the magnetic objects.

3. The medical microdevice according to claim 2, wherein the casing comprises at least two openings, wherein the pressure sensitive element is arranged between the at least two openings, and wherein a pressure difference is created between the at least two openings.

4. The medical microdevice according to any one of claims 1-3, wherein the pressure sensitive element is a flexible membrane, and wherein one of the magnetic objects is attached to the flexible membrane such that a movement of the flexible membrane causes a movement of the magnetic object.

5. A medical device for use during a surgical or a medical procedure performed under ultrasound guidance wherein the medical device comprises a medical microdevice according to any one of claims 1-4.

6. A registration apparatus comprising an ultrasound system, and an electromagnetic reading system for reading a signal from a medical microdevice, wherein the registration apparatus comprises: a receiving interface configured to receive a) a signal indicative of a transmit direction of an external ultrasound signal transmitted by the ultrasound system and b) an electrical response signal of the medical microdevice in response to a magnetic or electromagnetic excitation field (-s) provided by the electromagnetic reading system, one or more processors configured to register the ultrasound system with the reading system based on the electrical response signal and the external ultrasound signal.

7. The registration apparatus according to claim 6, wherein the one or more processors are further adapted to determine a presence or absence of the external ultrasound signal at or near the microdevice based on the electrical response signal and a location of the medical microdevice relative to the electromagnetic reading system.

8. The registration apparatus according to claim 7, wherein the one or more processors are further adapted to determine a distance between the ultrasound system and the microdevice based on the electrical response signal (-s).

9. The registration apparatus according to any one of claims 6-8, wherein the registration apparatus further comprises an output interface configured to provide an output signal adapted to cause a visualization of a location of the microdevice, such as a visualization of a location of the microdevice in an ultrasound image of the ultrasound system.

10. A reading system for reading a signal from a medical microdevice comprising a magneto mechanical resonator and registering the reading system to an ultrasound system, wherein the reading system comprises: a field generator for generating a magnetic or electromagnetic excitation field (-s) for inducing a mechanical movement of a magnetic object of a magneto mechanical resonator of the medical microdevice, wherein the movement of the magnetic object generates a periodically changing response magnetic field, a transducer for sensing and transducing the response magnetic field into an electrical response signal, a registration apparatus.

11. The reading system of claim 10, wherein the registration apparatus comprises: a receiving interface configured to receive: a) a signal indicative of a transmit direction of an external ultrasound signal and b) an electrical response signal of the medical microdevice provided by the medical microdevice in response to a magnetic or electromagnetic excitation field provided by the electromagnetic reading system, one or more processors configured to register the ultrasound system with the reading system based on the electrical response signal and the external ultrasound signal.

12. A computer-implemented registration method for registering an ultrasound system with an electromagnetic reading system for reading a signal from a medical microdevice, wherein the method comprises the steps of: receiving a signal indicative of a transmit direction of an external ultrasound signal transmitted by the ultrasound system, receiving an electrical response signal of the medical microdevice provided by the medical microdevice in response to a magnetic or electromagnetic excitation field provided by the electromagnetic reading system, registering the ultrasound system with the reading system based on the electrical response signal and the external ultrasound signal.

13. The method according to claim 12 further comprising determining a presence or absence of an external ultrasound signal at the microdevice based on the electrical response signal and a location of the medical microdevice relative to the electromagnetic reading system based on the electrical response signals, and registering the signal of the ultrasound system with the reading system based on the external ultrasound signal.

14. The method according to claim 13, wherein the method further comprises determining a distance between a source of the external ultrasound signal transmitted by the ultrasound system and the microdevice based on the electrical response signals, and registering the ultrasound system with the reading system further based on the determined distance.

15. The method according to any one of claims 12-14, further comprising providing an output signal adapted to cause a visualization of a location of the microdevice.

16. A computer program product for causing a registration apparatus to perform the method according to any one of claims 12-15.

17. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method of any one of claims 12-15.