WO2020070125A1

WO2020070125A1 - Energy collector for obtaining electrical energy in time-varying magnetic fields

Info

Publication number: WO2020070125A1
Application number: PCT/EP2019/076590
Authority: WO
Inventors: Daniel Hoffmann; Enrico Pannicke
Original assignee: Hahn-Schickard-Gesellschaft Für Angewandte Forschung E. V.; Otto-Von-Guericke-Uni Magdeburg
Priority date: 2018-10-02
Filing date: 2019-10-01
Publication date: 2020-04-09
Also published as: DE102018126909B4; DE102018126909A1

Abstract

The invention relates to an energy collector comprising a coupling element made of an electrically conductive material, which is connected in an oscillatory manner to an electromechanical converter in such a way that the time-varying magnetic gradient field excites the coupling element to oscillate and generates electrical energy in the converter. The invention further relates to methods and to uses of the energy collector for obtaining electrical energy during magnetic resonance tomography and to a system comprising an energy collector and a magnetic resonance tomograph.

Description

ENERGY COLLECTORS FOR THE PRODUCTION OF ELECTRICAL ENERGY IN PERMANENTLY CHANGEABLE MAGNETIC FIELDS

DESCRIPTION

The invention relates to an energy collector comprising a coupling element made of an electrically conductive material, which is connected to an electromechanical transducer so that it can vibrate in such a way that a time-varying magnetic gradient field excites the coupling element to oscillate and generates electrical energy in the transducer. The invention further relates to methods and uses of the energy collectors for obtaining electrical energy in magnetic resonance tomography and a system comprising one

Energy collector and a magnetic resonance tomograph.

Background and state of the art

National and international research groups (Mitcheson 2004, Mitcheson 2008, Shaikh 2016, Khaligh 2010, Beeby 2006, Tang 2010) have been focusing on the development and evaluation of energy harvesting systems (energy collectors) for harvesting ambient energy, especially machine vibrations , Spreemann 2006, Hoffmann 2014). This fact is also reflected in the quantity of publications. For coupling external vibrations into an energy harvesting system, resonant spring-mass-damper structures are preferably used (Mitcheson 2008), the mass excited to vibrate being damped with the aid of an electromechanical energy converter. The energy conversion can be electromagnetic, electrostatic or piezoelectric (Mitcheson 2004, Mitcheson 2008)

Energy collector systems have a wide range of applications. In production facilities, these can significantly increase energy efficiency by exploiting the machine vibrations that occur anyway. Furthermore, for any wireless, usually battery-operated electrical devices such as mobile telephones, mp3 players and the like, energy collectors are of great economic interest in order to increase battery life and thus ease of use (Mitcheson 2008).

Different designs for energy collectors are known in the prior art.

DE 10 2004 055 625 A1 discloses a voltage generator with a movable slide at the lower end of which there is an opposite-pole permanent magnet and a transducer element arranged below the slide. The transducer element consists of a carrier formed by a ferromagnetic leaf spring with strip-shaped piezo elements and is clamped at the lower end. Rapid swiveling movements of the slide are transmitted to the leaf spring by the magnetic interaction, so that voltage impulses can be picked up from the piezo elements. The voltage generator should be particularly suitable for supplying evaluation electronics.

DE 1 1 2016 000 199 T5 describes a device for generating electricity from an oscillation. The power generator has a first mass element in the form of a housing which is elastically connected to a vibrating element via a spring element. Within of the first mass element there is a second mass element. This preferably has the shape of a solid component and is held elastically by a second spring element. A piezoelectric power generation element connects the two mass elements so that a relative vibration can be used to generate electricity. The use of two oscillation systems is intended to enable an improved adaptation of the resonance frequency to the oscillation frequency of the oscillating element.

Energy collectors also provide significant technical advantages in the context of medical applications in which a cable-based energy supply can be disadvantageous.

Image-guided minimally invasive interventions, such as magnetic resonance imaging (MRI), are an important component in clinical diagnostics and in the implementation of therapy. Image-guided interventions in the magnetic resonance tomograph generally require accompanying examinations and continuous patient monitoring. The electronic devices used for this are mostly wired or battery-operated in the prior art. However, the presence of cables in an MRI is always associated with risks. On the one hand, imaging is impaired. On the other hand, the patient may be at risk from burns if the cables heat up in the high-frequency fields. The cable can also interfere with medical interventions and emergencies.

If batteries or accumulators are used exclusively to avoid the aforementioned disadvantages of cables, the reliability of the energy supply is limited. I.e. It must always be ensured that the devices are either returned to the charging stations after use or that the condition of the batteries is checked regularly. In addition, conventional rechargeable batteries can interfere with the magnetic fields and thus with MRI imaging. Special rechargeable batteries or batteries that are compatible with MRI applications, however, are expensive.

In the prior art there are therefore efforts to provide energy collector systems which are suitable for image-guided medical applications, such as magnetic resonance imaging.

Höfflin et al. In 2013, they proposed a concept for extracting electrical energy from the gradient fields of a spectrometer. The arrangement consists of a Figure 8 coil, which makes it possible to gain energy in the presence of the zero crossing of gradient fields. The Figure 8 coil harvests energy from gradient switching and RF pulses and converts these alternating signals into a DC voltage that can be used to operate a preamplifier. However, the concept is not readily transferable to a whole-body tomograph, since the Figure 8 coil requires a zero crossing of the gradient field in order to be operated efficiently. In addition, only one of the three available fields can be used at a time.

Other inductive approaches to using coils to collect energy from the magnetic fields of an MRI are not known in the prior art. The generation of energy from the potentially high-energy, high-frequency alternating field of the tomograph also harbors the problem that the transmitting and receiving coils also have the Larmor frequency of the High-frequency field are adjusted. In such applications, interactions between the transmitting / receiving elements and the energy collector would have to be expected, which would impair the imaging.

Systems are also known in the prior art which introduce additional external energy sources in order to ensure this for providing energy within an MRT.

Klymko et al. 2013 describes an array of piezoelectric loudspeakers that can focus acoustic energy on a local area. An acoustic energy collector (piezoelectric loudspeaker) is placed in this area in order to convert the acoustic energy back into electrical energy. An advantage of the proposed arrangement is that there is no interaction with the imaging magnetic fields of the MRT. However, the efficiency is very low at 0.01%. In addition, the speaker array must be installed in the MRT tube as an additional installation. The acoustic focus point can be adjusted via the phase of the loudspeakers, but additional time is required. Such an energy collector cannot be placed quickly and flexibly.

Bryon et. al. 2018 discloses a system based on the inductive coupling of two coils. The primary coil has been integrated into the patient table and is intended to supply a secondary coil with up to 1 1 W at a transmission frequency of 10 MHz. A disadvantage of this approach is the limited range of action of the secondary coil, which must always be in a volume above the primary coil. In addition, only one secondary coil can be operated efficiently on its own and the performance of the arrangement strongly depends on the coupling of the two coils. This is e.g. changed by the presence of a human body.

Höfflin et al. 2014 demonstrated the concept of optical energy transmission for the supply of preamplifiers in a magnetic resonance tomograph. The emitted light from a laser diode is guided to the amplifier via fiber optic cables and converted back into electrical energy with the help of a special photodiode (photonic power oohnbPq.). Sharafi et al. 2013 apply this principle to the supply of a miniaturized coil in a catheter, which is called active marker was used in MR imaging, but a cable that contains the corresponding optical waveguide is also necessary for an approach to optical energy transmission.

There is therefore a need for alternative approaches for energy collectors, which are particularly suitable for medical applications, such as for magnetic resonance imaging.

Object of the invention

The object of the invention is to provide an energy collector and a method for producing energy without the disadvantages of the prior art. In particular, it was an object of the invention to provide an energy collector which is highly efficient in the production of electrical energy, in particular for applications in the

Has magnetic resonance imaging and at the same time by a simple,

low-cost compact structure.

Summary of the invention The task is solved by the features of the independent claims. Beneficial

Embodiments of the invention are described in the dependent claims.

In a first aspect, the invention relates to an energy collector for the production of electrical energy in the case of magnetic fields which can be changed over time, in particular for use in the

Comprehensive magnetic resonance imaging

a. a coupling element for a temporally changing magnetic gradient field b. a housing and

c. an electromechanical transducer,

wherein the coupling element is made of a conductive material and over the

Electromechanical transducer is connected to the housing so that it can vibrate, so that a magnetic gradient field that changes over time, particularly in the case of

Magnetic resonance imaging excites the coupling element to oscillate and generates electrical energy in the converter. The coupling element is preferably set up or constructed in such a way that a time-changing magnetic gradient field induces eddy currents in its surface, which are subjected to a force when a static magnetic field is superimposed, so that a time-changing magnetic gradient field closes the coupling element when it is superimposed with a static magnetic field excites a vibration and generates electrical energy in the electromechanical transducer.

The energy collector according to the invention is characterized by a particularly efficient generation of energy from time-changeable magnetic fields, which are used in magnetic resonance tomography. The energy collector can thus be used in particular to supply the electronic systems for monitoring or communication with a patient with energy during an MRI examination. There is no need for disadvantageous cabling. Regular replacement of batteries or accumulators is also unnecessary. Instead, the energy collector uses the energy provided by the magnetic fields in the MRI and can be carried easily and flexibly by the patient due to its compact design. Potential fields of application of the energy collector relate not only to magnetic resonance imaging, but also to any areas in which time-varying magnetic springs occur, especially when these are overlaid by static magnetic fields.

The principle of the energy collector is based on the interaction of the coupling element with the electromechanical transducer, which form a system capable of oscillation through a connection to the housing. In the context of the invention, the coupling element is understood to mean an element made of electrically conductive material, which is designed such that a change in a magnetic field over time leads to the formation of eddy currents in its surface. If a static magnetic field is superimposed, the eddy currents are subjected to a force, causing the coupling element to vibrate or

Vibrations is excited. These vibrations can be converted into electrical energy via the electromechanical transducer, for example a piezoelectric bar, which can be made available to various consumer devices.

The energy collector according to the invention is particularly preferably suitable for obtaining electrical energy from magnetic fields that typically occur in magnetic resonance imaging.

Magnetic resonance imaging is preferably understood to mean any imaging method which is based on principles of nuclear magnetic resonance (English nuclear magnetic

Resonance, NMR) based and by generating sectional images in the medical

Diagnostics is used to represent structures or functions of tissues and organs. Magnetic resonance imaging or magnetic resonance imaging (MRI) are synonymous terms.

Three different magnetic fields are generally used for imaging in magnetic resonance tomography: a statistical magnetic field, a gradient field and a high-frequency field.

In magnetic resonance tomography, the static magnetic field is responsible for the development of a measurable magnetization in the patient. Typical field strengths for clinical use in humans are 0.5T - 3T. Higher field strengths can also be made available for experimental research and applications on small animals (mice, rats, etc.). For optimal imaging, a high field homogeneity is guaranteed in the tomograph with fluctuations of less than 1 ppm (parts per million). Outside the tomograph, the field strength decreases with increasing distance. The so-called stray field is present in this area.

Gradient fields are superimposed on the static magnetic field in MRT in order to obtain a linear dependence of the total magnetic field in one of the three spatial directions (x, y, z). With this dependency, location coding can be carried out, with which the associated signal distribution in the body can be reconstructed from the received sum signal.

Typically, the gradient fields are defined based on their increase in the spatial direction (e.g. max. 45 mT / m) and the rise time (e.g. max. 200T / m / s). Gradient fields can be approximated as linear within a certain volume. Outside of this range, the fields are not linear.

In order to generate a usable signal, high-frequency alternating fields are irradiated into the MRI tube. Their frequency is determined on the basis of the so-called Larmor frequency. The Larmor frequency describes the frequency of the precession of a nuclear spin in an external magnetic field and depends linearly on its strength. For protons (hydrogen atoms), the Larmor frequency in a static magnetic field of 1 Tesla is approx. 42.6 MHz; in the case of a static magnetic field of 3 Tesla, the Larmor frequency is approx. 128 MHz. Typical field strengths of the related high-frequency fields are in the mT range. The

Power densities are correspondingly high.

The interaction of all three magnetic fields is used for layer imaging. By applying a strong static magnetic field, longitudinal magnetization of the nuclear spin, in particular of hydrogen nuclei in the tissues to be examined, can be achieved will. By pulsing the high-frequency alternating field (e.g. by means of a 90 ° excitation pulse) in the area of the Larmor frequency, these magnetizations can be deflected from the direction of the static magnetic field and completely or partially converted into a transverse magnetization.

A precession of the transverse magnetization around the field direction of the static magnetic field generates an electrical voltage which can be detected. After switching off the high-frequency alternating field, the transverse magnetization decreases by aligning the spins to the static magnetic field. A 180 ° rephasing high-frequency pulse can be used to at least partially reverse the dephasing in a controlled manner.

The different time constants for spin-spin or spin-lattice relaxation depend on the chemical bond and the molecular environment, in the precessing

Hydrogen nucleus are present. Different tissue types therefore result in characteristic decay times and signal strengths, which can be used for imaging.

In order to be able to assign signals to the individual volume elements in slice imaging, a location coding is generated using linearly location-dependent gradient fields. This takes advantage of the fact that for a certain particle the Larmor frequency depends on the magnetic flux density (the stronger the field portion perpendicular to the direction of the particle angular momentum, the higher the Larmor frequency).

In clinical MRI examinations, a combination of high-frequency pulses and magnetic gradient fields of a certain frequency or strength is carried out, which can be switched on and off according to the specified sequence. These are also known as "sequences" or "pulse sequences".

A so-called slice selection gradient is typically applied during the excitation, which ensures that only a single slice has the appropriate Larmor frequency. Shortly after the excitation, a second gradient field transverse to the first gradient field can be switched on, which causes a different dephasing of the spins in each image line in a controlled manner (phase coding gradient). In addition, a frequency coding gradient field can be applied at right angles to the other gradient fields, which ensures that spins of each image column send a specific Larmor frequency.

Depending on the tissue to be examined or medical questions, the pulse sequences can vary for different MRI applications. Common to all commercially relevant MRI systems is the use of pulse sequences in which the gradient fields are switched on and off several times per second. The frequencies of the time-varying gradient fields are usually between 100 Hz and 2000 Hz.

The inventors have recognized that the clocked gradient fields of the MRT systems can be used for an energy collector without interfering with the imaging.

If an inventive coupling element made of an electrically conductive material, which is preferably not ferromagnetic, is placed in the inner tube of an MRT, then in induced eddy currents due to the clocked gradient fields. The strong static magnetic field in the area of a few Tesla now leads to a force effect on the coupling element, which is set in vibration by the rapid sequence of switching the gradient fields (see Fig. 1)

The vibration of the coupling element can be used for energy generation. For this purpose, the coupling element is connected to the housing of the energy collector so that it can vibrate via an electromechanical transducer. For this purpose, the energy collector preferably has an elastic element (for example a spring element) and the coupling element is coupled to the housing both by the elastic element and by the electromechanical transducer (electrical damper) (see FIG. 3a).

The coupling element, which experiences a force through the direct action of the changing gradient fields when superimposed on a static magnetic field, can transmit this force directly to the elastic element, whereby an oscillation is generated. If the natural frequency of the oscillatable system is adapted to the excitation, resonant operation can be achieved, which leads to a high effectiveness of the energy conversion.

As electromechanical transducers, e.g. piezoelectric transducers (e.g. PZT bimorph elements) or an electrostatic transducer.

In one embodiment according to the first aspect of the invention, the vibration of the coupling element can be used to generate energy in the magnetic fields for generating energy by connecting the coupling element to a housing via an electromechanical transducer.

However, the teaching according to the invention can also include other configurations of an energy collector, which use the vibration of the coupling element to generate energy.

In a second aspect, the invention relates to an energy collector for the production of electrical energy in the case of time-variable magnetic fields, in particular for use in the

Comprehensive magnetic resonance imaging

a. a coupling element for a temporally changing magnetic gradient field b. a housing

c. an elastic element and

d. a vibration energy collector,

wherein the vibration energy collector is connected to the coupling element, which is made of an electrically conductive material and is connected to the housing via the elastic element so that it can vibrate, so that a time-varying magnetic gradient field excites the coupling element to oscillate and generates electrical energy in the vibration energy collector. For this embodiment, too, the coupling element is preferably set up or configured such that a magnetic that changes over time

Gradient field induces eddy currents in its surface, which experience a force when a static magnetic field is superimposed, so that a time-changing one magnetic gradient field when superimposed with a static magnetic field

Coupling element excites to oscillate and generates electrical energy in the electromechanical converter.

A schematic illustration of a preferred embodiment of the energy collector according to the second aspect of the invention is shown in Fig. 3c.

In an energy collector according to the second aspect of the invention, the vibration of the coupling element is translated into a vibration of a classic vibration energy collector. The term “vibration energy collector” is to be understood as a device of the generic type which is able to obtain electrical energy from mechanical vibrations. Various systems are known for vibration energy collectors and are described, for example, in Mitcheson 2004, Mitcheson 2008, Shaikh 2016, Khaligh 2010, Beeby 2006, Tang 2010, Spreemann 2006 or Hoffmann 2014. It is preferably a vibrati on energy collector comprising a further housing (preferably made of a non-conductive material) in which there is a seismic mass which is connected to the housing via an energy converter, preferably in the form of a spring-damper structure.

The coupling element is preferably mechanically connected to the vibration energy collector in such a way that the vibrations are transmitted largely without dissipation. For example, a rigid mechanical connection between the coupling element and the housing of the vibration energy collector may be preferred. In the event of a vibration of the coupling element, the vibration energy collector will therefore vibrate equally, so that, however, the inside the seismic mass is excited to oscillate via a spring-damper structure as an energy converter. The energy conversion in the spring-damper structure can preferably take place electrostatically or piezoelectrically. Electromagnetic energy conversion based on induction is less preferred, since imaging can be impaired, particularly in applications in magnetic resonance tomography.

In a third aspect, the invention relates to an energy collector for obtaining electrical energy in the case of time-variable magnetic fields, in particular for use in magnetic resonance imaging

a. a coupling element for a temporally changing magnetic gradient field b. an electromechanical transducer and

c. a seismic mass

wherein, the coupling element is a hollow body, the outer wall of which is made of an electrically conductive material and in the inner cavity of which the electromechanical transducer as well as the seismic mass are present, the seismic mass oscillating via the electro-mechanical transducer with the outer wall of the coupling element is connected so that a temporally changing magnetic gradient field excites the coupling element to oscillate and generates electrical energy in the electromechanical transducer. In this preferred embodiment, the coupling element is also preferably set up or provided in such a way that a temporally changing magnetic gradient field creates eddy currents in the latter Surface induced, which experiences a force effect when a static magnetic field is superimposed, so that a temporally changing magnetic gradient field, when superimposed with a static magnetic field, excites the coupling element to oscillate and generates electrical energy in the electromechanical transducer. A schematic illustration of a preferred embodiment of the energy collector according to the third aspect is shown in Fig. 3d.

In the case of an energy collector according to the third aspect, the coupling element is preferably designed as a hollow body, in the inner cavity of which a seismic mass is connected to the outer wall as an electromechanical transducer via a spring-damper structure. The seismic mass can be configured as in the case of classic vibratory energy collectors and, in order to increase efficiency, is preferably characterized by a high mass with a small volume. For example, materials with a high density, particularly preferably with a density higher than 10 g / cm ³ , are preferably used for a seismic mass. Tungsten or lead are suitable for this. It is also preferred that the seismic mass is not a hollow body but a solid body in order to ensure a high mass with the smallest possible size (volume). The ratio of the volume enclosed by the outer surface of the seismic mass and the mass of the seismic mass preferably has more than 10 g / cm ³ . This ensures a particularly effective generation of energy from the excitation of the seismic mass for oscillation by the vibration of the coupling element.

In addition, in the embodiment, the coupling element not only serves to excite vibration, but preferably also functions as a housing at the same time. A separate housing is not necessary. Furthermore, the coupling element also preferably has a magnetic shielding function for alternating magnetic fields, such as the changing gradient fields, so that the energy converter and the seismic mass in the inner cavity interact only to a lesser extent with the outer magnetic fields. This helps to minimize disruptive influences on the imaging when used in magnetic resonance imaging. Furthermore, the shielding function for alternating magnetic fields allows greater flexibility in the choice of materials for the electromechanical transducer and the seismic mass, since disadvantageous magnetic properties lead to less interference.

The configurations of the energy collector according to the first, second and third aspect are connected by the common idea of a coupling element which is optimized for being excited by magnetic fields to vibrate, which typically occurs in the

Magnetic resonance imaging may occur. The configurations of the energy collector according to the first, second and third aspects differ, as described above, primarily in how the vibrations of the coupling element into electrical energy

being transformed.

What the energy collectors have in common is that they comprise a coupling element made of an electrically conductive material, which is connected to an electromechanical transducer so that it can oscillate in such a way that a time-varying magnetic gradient field excites the coupling element to oscillate and generates electrical energy in the transducer. One skilled in the art therefore also understands that the preferred ones described below

Embodiment largely apply equally to energy collectors according to the first, second and third aspects. This applies, for example, to the selection of particularly suitable electromechanical transducers, as well as the material or the shape of the coupling elements.

The shape, choice of material and size of particularly suitable coupling elements are preferably adapted to the gradient fields that can be changed over time.

Preferred electrically conductive materials include materials with an electrical

Conductivity at room temperature (25 ° C) of at least 10 ³ S / m (Siemens per meter), particularly preferably 10 ⁴ S / m, 10 ⁵ S / m, 10 ⁶ S / m. In particular, it is preferred to choose a metal as the electrically conductive material for the coupling element.

In a preferred embodiment, the electrically conductive material is a paramagnetic or diamagnetic metal.

Paramagnetic metals are characterized by a magnetic permeability of greater than 1 or a magnetic susceptibility of greater than 0 and follow an external, applied magnetic field in their magnetization, whereby the magnetic field within paramagnets is strengthened. Examples of paramagnetic metals include lithium, sodium, platinum, tungsten, potassium, titanium, magnesium or aluminum.

In an external magnetic field, a magnetic field is induced in diamagnetic metals, which is opposite to the external magnetic field and weakens the magnetic field inside.

Diamagnetic metals have a magnetic permeability of less than 1 or a magnetic susceptibility of less than 0. Examples of diamagnetic metals include copper, silver, gold, bismuth, zinc or lead.

In contrast to ferromagnets, there is no spontaneous magnetization of larger areas and macroscopic magnetization in the external magnetic field. For this reason, coupling elements made of para- or diamagnetic metal do not interfere with the imaging in MRI or only with little. While the magnetic fields are only slightly affected, the coupling elements are effectively excited to oscillate and vibrate due to the changing gradient fields.

The materials copper, titanium and aluminum have proven to be particularly suitable. Eddy currents with low dissipation and heat generation are induced in these by the changing gradient fields. There are particularly strong vibrations without noticeable interference with the imaging being recorded. Furthermore, particularly light coupling elements can be provided with the aid of the materials, which increases the efficiency.

Classic energy collectors based on vibrations require the heaviest possible seismic masses in order to obtain energy from the external vibrations. In contrast, the

Energy generation of the described energy collector on the induction of eddy currents by time-variable magnetic fields, which lead to a vibration of the coupling element in a statistical magnetic field. There are no particularly heavy materials required, instead light materials can be used to increase the efficiency. In addition, lightweight coupling elements also lead to less wear and thus a longer product life.

In a preferred embodiment, the material of the coupling element has a density of less than 10 g / cm ³ . Materials of this type can be used to construct lightweight coupling elements with the aforementioned advantages.

The inventors have also recognized that in addition to the choice of materials, a specification of the shape or structure of the coupling elements is also suitable in order to increase their efficiency.

In a preferred embodiment of the invention, the coupling element is a hollow body, preferably an ellipsoidal hollow body, very particularly preferably a hollow ball.

For the purposes of the invention, a hollow body preferably designates a partially hollowed-out coupling element which comprises an outer wall and an inner cavity which is at least partially enclosed therefrom. As in the case of a hollow sphere or a hollow cuboid, the cavity can be completely enclosed by the outer wall or, as in the case of a hollow cylinder, can also have open sides. The outer wall of the hollow body is preferably made of the conductive material, with preference being given to using diamagnetic or paramagnetic metals.

The cavity is not filled with the conductive material and is preferably empty. However, it can also be preferred to introduce a non-conductive, light filler or foam into the cavity.

The principle of action of the coupling elements in the form of a hollow body is shaped by the outer wall, in which eddy currents form in the case of magnetic fields which can be changed over time.

Layer thicknesses of the outer wall of 0.5 mm to 10 mm, preferably 1 mm to 5 mm, have proven to be particularly advantageous.

Due to the two-dimensionality, the direction and propagation of eddy currents in magnetic fields of changing orientation can be controlled particularly precisely in the case of hollow bodies.

Coupling elements in the form of hollow ellipsoids, preferably hollow spheres, are also characterized in particular by the fact that they are reliably excited to vibrate regardless of an orientation with respect to preferred directions of the changing magnetic fields and thus serve to generate energy. This is of particular advantage when using the energy collector in magnetic resonance tomography, in which it can be preferred to attach it to the patient in different orientations. The embodiment is thus characterized by a high degree of flexibility with high efficiency.

In addition, in contrast to solid coupling elements, hollow bodies are characterized by a particularly low effective density and lightweight construction. In a preferred embodiment of the invention, the ratio of the volume enclosed by the surface of the coupling element and the mass of the

Coupling element less than 10 g / cm ³ , preferably less than 1 g / cm ³ , particularly preferably less than 0.1 g / cm ³ .

The ratio of the volume enclosed by the surface of the coupling element and the mass of the coupling element can also be referred to as effective density in the sense of the invention. In the case of a solid coupling element, e.g. a solid sphere, the effective density will correspond to the material density. In the case of a hollow body, however, significantly lower effective densities can be achieved.

Under a volume enclosed by the outer surface, a is preferred

Understood envelope volume of the coupling element. With an external surface such as a hollow sphere or cuboid, the volume corresponds to that of the sphere or cuboid. In the case of not completely closed outer walls or surfaces, such as in the case of a hollow cylinder, the volume which is enclosed by an imaginary convex envelope should preferably be understood. With regard to the example of a hollow cylinder, the volume enclosed by the outer surface therefore preferably corresponds to the volume of a solid cylinder with the same outer dimensions.

By choosing hollow bodies with appropriate ratios of the wall thicknesses to the cavities, coupling elements with a particularly low weight can be provided largely independently of the material density. The vibration excitation through time-varying gradient fields is also particularly pronounced and controllable.

In a further preferred embodiment, the coupling element is a sheet with a thickness of 0.5 mm to 3 mm, preferably 1 mm to 2 mm, and a surface of 20 cm ² to 200 cm ² , preferably 40 cm ² to 80 cm ² . The term sheet metal denotes a preferably flat dimensioning of the coupling element, which is particularly preferably formed from a metal sheet. The shape of the sheet surface can be chosen differently. For example, a circular shape, a curved shape or a rectangular shape may be preferred.

Regardless of the specific shape, the aforementioned dimensions, in particular in magnetic resonance tomography, can be used to achieve excellent results for vibration excitation with optimized power transmission to the electromechanical transducer.

The aforementioned embodiments of the coupling elements are for the induction of

Eddy currents are optimized in a temporally changing magnetic gradient field, which experiences a force effect particularly when superimposed with a static magnetic field and thus excite the coupling element to oscillate or vibrate. The embodiments of the coupling element according to the invention therefore differ from components of known vibration energy collectors, such as the seismic masses.

Seismic masses in known vibration energy collectors are mostly massive

Components designed to provide the largest possible mass in relation to their volume. Prior art seismic masses are therefore preferred Materials with high density and are also neither flat nor designed as hollow bodies. Instead, solid cuboids, solid spheres or solid cylinders are preferred.

The described coupling elements with a large surface for induction of eddy currents thus represent a departure from seismic masses from the prior art and are specifically optimized for the described energy generation in time-varying magnetic gradient fields.

With the coupling element according to the invention, in particular for those described above

Embodiments, induction of oscillations or vibrations occurs in time-variable magnetic fields. In order to use this to generate electrical energy, the coupling element is connected to the housing so that it can vibrate via an electromechanical transducer.

In the sense of the invention, the electromechanical converter preferably denotes an electrically damping element which converts kinetic energy (oscillation / vibration) into electrical energy. The ability to vibrate is preferably realized by an elastic element (spring element). This can be integrated in the electromechanical converter or else connect the coupling element to the housing separately in parallel.

Various principles are known in the prior art for obtaining energy from mechanical movements by means of electrical damping. These include, in particular, transduction mechanisms based on piezoelectric, electrostatic or electromagnetic (Beeby 2006).

Electromagnetic generators use the induction of an electric field to generate electricity, which is generated by a relative movement of a conductor in a magnetic flux. In this case, permanent magnets or ferromagnetic materials are mostly used. For applications in magnetic resonance tomography, an electromagnetic converter can therefore have disruptive effects on the imaging.

In a preferred embodiment of the invention, the electromechanical transducer is therefore a piezoelectric or an electrostatic transducer.

An electrostatic converter uses the relative movement of electrically insulated capacitor plates, which can be conveyed by the vibration, to generate electrical energy. Here, the mechanical energy provided by the vibrations is used to perform work against the electrostatic (attraction) force of differently charged capacitor plates. In the constant charge mode, the energy of the electric field increased by mechanical work can be provided in the form of a voltage increase, while in the constant voltage mode an electrical current can be tapped. The

Provision of charged capacitor plates can be provided by a so-called priming or precharging. Alternatively, electrets can also be used which, in the form of dielectric layers, allow quasi-permanent storage of electrical charges. With regard to the shape of the capacitor plates, various arrangements are conceivable, for example in the form of parallel plates or as a comb structure, the capacitive change of which is based on a variation in the comb coverage or the comb spacing (cf. Beeby 2006).

Electrostatic converters are characterized by high reliability with a simple and robust design.

A piezoelectric transducer or generator is based on the use of mechanical vibrations for the elastic deformation of piezoelectric materials, as a result of which an electric field or a voltage is generated (piezoelectric effect, cf. Mitcheson 2008).

Different geometric shapes of piezoelectric transducers are suitable for the purposes described.

For example, piezoelectric layers can be introduced between plates, the vibrations leading to a change in distance and thus voltage generation.

Piezoelectric beams (bending beams, biomorphic elements) are particularly preferred. The pie zoelectric bars can preferably be arranged as cantilever chairs (canf / ^' / ever) with which the coupling element is connected. A vibration excitation of the coupling element causes a mechanical, elastic deformation of a piezoelectric layer of the piezo bar, which can be tapped as an electrical voltage. Such piezoelectric beam structures can cause vibrations of different orientations and

Amplitudes can be used particularly effectively to generate electrical energy.

Lead zirconate titanate (PZT), aluminum nitride (AIN), zinc oxide (ZnO), flafnium oxide or lithium niobate (LiNb03) are particularly suitable as piezoelectric materials for the applications described. Excellent efficiency and results are achieved with these materials. It is particularly preferred to use piezoelectric materials which have no ferromagnetic properties in order to minimize potential interference.

The electromechanical transducers are particularly preferably so-called microelectromechanical systems (MEMS). Such mechanical electronic devices are characterized by a high degree of compactness

Dimensions in the micrometer range. Technological progress in the field of MEMS means that excellent functionality can be achieved at ever lower manufacturing costs.

In a preferred embodiment, the energy collector is characterized in that the housing, the electromechanical transducer and the coupling element form an oscillatable system which has at least one natural frequency between 100 and 2000 Hz, preferably between 200 and 2000 Hz, very particularly between 500 and 1000 Hz .

The system consisting of housing, electromechanical transducer and coupling element is characterized by at least one degree of freedom and is described as capable of oscillation. In the case of a piezo bar, the coupling element may vibrate on the

Act bar structure, which is installed on the housing. In the case of an electrostatic converter, for example, a capacitive comb structure can also be arranged parallel to a spring element the housing and the coupling element are arranged. In this case, the degree of freedom corresponds to a linear compression or extension.

The aforementioned embodiment is particularly preferred for an energy collector according to the first or second aspect. For an energy collector according to the third aspect, on the other hand, it is particularly preferred that the coupling element (which preferably acts as a housing), the electromechanical converter and the seismic mass form an oscillatable system which has at least one natural frequency between 100 and 2000 Hz, preferably between 200 and 2000 Hz, especially between 500 and 1000 Hz.

For an energy collector according to the third aspect, the system of coupling element (which acts as a housing), electromechanical transducer and seismic mass is characterized by at least one degree of freedom and can be described as capable of oscillation. In the case of a piezo bar, it can be a vibration of the seismic mass on the bar structure, which is installed on the coupling element. In the case of an electrostatic converter, e.g. there is also a capacitive comb structure arranged parallel to a spring element between the coupling element and the seismic mass. In this case, the degree of freedom corresponds to a linear compression or extension.

When a system capable of oscillation is excited with a so-called natural frequency or a frequency which is close to the natural frequency, particularly high amplitudes are achieved. The system resonates. A natural frequency corresponds to the frequency at which the oscillatable system oscillates with the associated mode (mode) and can be determined experimentally or theoretically by a modal analysis.

The natural frequencies of vibratable systems depend on their mechanical or electrical properties, such as a spring constant or the damping strength. By appropriate selection of the parameters, in particular for the electromechanical transducer, energy collectors with predetermined natural frequencies can be provided.

The preferred embodiment has at least one natural frequency between 100 and 2000 Hz, preferably between 200 and 2000 Hz, very particularly between 500 and 1000 Hz. When the coupling element is excited to oscillations or vibrations in one

The frequency range which is close to the natural frequency thus becomes particularly large

Amplitudes and at the same time achieved a high energy yield.

The preferred embodiment is thus optimized for applications in which the

Coupling element is excited in the aforementioned frequency range. This is particularly the case for use of the energy collector in magnetic resonance tomography, in which the changing gradient fields typically experience a timing of 100 to 2000 Hz.

In contrast, known, well-known vibration-based energy collectors are designed with significantly lower natural frequencies in order to generate energy efficiently

To guarantee machine vibrations or from vibrations that occur when using mobile devices. The natural frequencies of typical spring-seismic mass-vibration systems are often less than 100 Hz or 50 Hz. In a further preferred embodiment, the energy collector has at least two coupling elements, each of which is connected to the by an electromechanical converter

Housing are connected to vibrate, preferably at least two oscillatable systems are formed from a coupling element, an electromechanical transducer and the housing, which have different natural frequencies.

The aforementioned embodiment is particularly preferred for an energy collector according to the first or second aspect. In contrast, for an energy collector according to the third aspect, the coupling element preferably functioning as a housing, it is particularly preferred that the energy collector has at least two seismic masses, each of which is connected to the coupling element by an electromechanical transducer, preferably at least two systems capable of oscillation each formed from a seismic mass, an electromechanical transducer and the coupling element, which have different natural frequencies.

By providing an array of oscillatable systems with different natural frequencies, a larger frequency range of the time-variable magnetic fields can be used effectively for energy generation. In the preferred field of application of magnetic resonance tomography, several specific harmonics were found in experimental tests. By means of an array of at least two coupling elements (or two seismic masses) and a corresponding coverage of at least two natural frequencies, the harmonics that occur in the clocked gradient fields can be used efficiently to generate energy.

Particularly preferred are energy collectors with 2 to 10, very particularly preferably 2 to 5 coupling elements and a corresponding number of electromechanical transducers or for an energy collector according to the third aspect with 2 to 10, very particularly preferably 2 to 5 seismic masses and a corresponding number of electromechanical transducers. Such energy collectors are characterized by an optimal balance of efficiency, compactness and manufacturing costs.

It is particularly preferred that the at least two different natural frequencies lie in a range from 100 and 2000 Hz, preferably between 200 and 2000 Hz, very particularly between 500 and 1000 Hz, and preferably at least 50-70 by a difference of 40-100 Hz Hz differentiate. The abovementioned frequency ranges and differences are matched to the preferred use of the energy collector in magnetic resonance tomography and reflect the harmonics of the clocked gradient fields to be recorded here.

The housing of the energy collector serves as the reference point of the oscillatable system and for stabilizing or protecting the energy collector from external influences. The

The dimensions of the housing are preferably chosen such that they can be conveniently attached to the patient. The choice of material is preferably adapted to the requirements of the applications. In particular for applications in magnetic resonance tomography, it is advantageous to use a housing which is made from an electrically non-conductive material. In this way, an effect on the imaging can be avoided. Plastics combine this property with high stability and low weight and one

inexpensive manufacturing method.

In a preferred embodiment, the housing is therefore made of an electrically non-conductive material, very particularly preferably of a plastic. This

Embodiment is particularly preferred for an energy collector according to the first or second aspect. For an energy collector according to the third aspect, as stated above, the coupling element itself preferably acts as a housing.

In a further embodiment of the invention, the energy collector has at least one permanent magnet for building up a static magnetic field. The presence of a permanent magnet is not necessary for applications in magnetic resonance tomography. As described above, the clocked gradient fields generate eddy currents in the coupling element, which, due to the presence of a strong static magnetic field, leads to the application of force and thus vibration excitation.

However, the principle of the energy collector for generating energy by means of magnetic fields that can be changed over time can advantageously be used in other areas.

For example, magnetic fields that can be changed over time also occur in power lines. These also induce eddy currents in the preferred coupling elements. Without a static magnetic field, the induced eddy currents are not translated into mechanical vibrations. For this purpose, it can be preferred to provide an energy collector with at least one permanent magnet, which generates a static magnetic field. The static magnetic field does not have to penetrate the range of a few Tesla in terms of strength. Rather, significantly lower field strengths are sufficient, in particular for the recovery of energy from the time-variable magnetic fields of power lines, in order to obtain significant electrical energy.

In a further aspect, the invention relates to a use of the described

Energy collector for obtaining electrical energy from a time-changing magnetic gradient field in magnetic resonance imaging.

On the one hand, the design of the energy converter is tailored to the magnetic fields used in magnetic resonance imaging, so that a particularly high degree of efficiency is achieved in such an application. On the other hand, classic implementations of energy supply for monitoring systems in the MRI tube are problematic. With cabling, the high-frequency alternating fields can melt the cables or burn the patient. Special, expensive batteries or accumulators must also be used to avoid interference with imaging. By using the described energy collector, these disadvantages can be avoided and a reliable power supply for various electronic devices close to the patient in the MRT tube can be guaranteed. In a further aspect, the invention therefore also relates to a system comprising a) a magnetic resonance tomograph and

b) an energy collector according to the invention or preferred embodiments thereof.

The magnetic resonance tomograph is understood to be a device which is configured to carry out a magnetic resonance tomography. Generic

Magnetic resonance tomographs are described, for example, in Nitz et al. Described in 2011. A variety of different commercial systems are known in different designs. This includes open and closed magnetic resonance tomographs.

Components that allow the generation of the described magnetic fields are characterized for a magnetic resonance tomograph. This includes in particular the generation of a static magnetic field, a time-variable gradient field and high-frequency fields. For this purpose, the magnetic resonance tomograph can have transmitter and receiver coils. The system according to the invention is not based on a specific construction method

Magnetic resonance tomograph limited. Instead, any devices that generate the aforementioned magnetic fields for an imaging method can be suitable.

It is preferred that the magnetic resonance tomograph is configured to be a static one

To provide a magnetic field with a field strength of at least 0.1 Tesla, preferably 0.1 to 10 Tesla, particularly preferably 0.5 to 3 Tesla.

Furthermore, the magnetic resonance tomograph is preferably configured to generate a high-frequency magnetic field in the megahertz range, which is preferably matched to the Larmor frequency of the atoms to be imaged. Field strengths of the generated high-frequency fields are preferably in the mT range.

In a preferred embodiment, the magnetic resonance tomograph is configured to generate a time-changing magnetic gradient field with a frequency between 100 Hz and 2000 H. Such magnetic resonance tomographs are widely used in the prior art. The changing magnetic gradient fields become as described above

Location coding used.

In a further preferred embodiment, the system comprises consumer devices, preferably for attachment to a patient, the energy collector using the

Consumer devices is connected to supply them with energy.

The term consumer devices is preferably understood to mean electronic devices which are not used directly for imaging but are used to support an MRI examination. Preferred consumer devices are used for monitoring (patient monitoring) or communication with the patient. Examples of preferred consumer devices that can be supplied by the energy collector include breathing belts or EKG devices or keyboards, screens or touchpads to enable communication between the patient and the medical personnel. The energy collector described is particularly optimized with regard to its use in magnetic resonance tomography or is distinguished by its property for this.

However, the principle according to the invention can advantageously also be used in other fields in which magnetic gradient fields that can be changed over time occur. On the one hand, as described above, this relates to current paths with magnetic fields which can be changed over time and which induce eddy currents in the coupling elements and, in the case of an additional permanent magnet, lead to vibration or oscillation of the coupling element.

However, the energy collectors described can advantageously be used in any system in which a time-varying magnetic gradient field and a static magnetic field are generated.

In a further aspect, the invention therefore also relates to a system comprising

a) a device for generating a temporally changing magnetic gradient field and a static magnetic field and

In a further aspect, the invention also relates to a system comprising

a) a device for generating a temporally changing magnetic gradient field and

b) an energy collector according to the invention or preferred embodiments thereof, the energy collector one

Has permanent magnets for generating a static magnetic field.

Very different, time-changing magnetic are advantageously suitable

Gradient fields and static magnetic fields to generate energy. While the high static field strengths of a few Tesla in a magnetic resonance tomograph lead to particularly good results, a use is not limited to this. Rather, even with smaller field strengths of the static magnetic field (for example of a few milli-Tesla (mT) or micro-Tesla (mT) with correspondingly changing magnetic gradient fields, substantial energy can be generated.

In a further aspect, the invention relates to a method for obtaining electrical energy in magnetic resonance imaging comprising the steps

a) Providing an energy collector according to the invention or preferred embodiments thereof

b) provision of a magnetic resonance tomograph

c) positioning of the energy collector, so that the energy collector is carried out by means of a magnetic resonance tomograph Magnetic resonance imaging is located in a time-changing magnetic gradient field

d) Use of the electrical energy generated by the energy collector for operating at least one consumer device.

The person skilled in the art recognizes that preferred embodiments and advantages which have been disclosed for the energy collector, its use and for the system have been found

equally applied to the process.

The energy collector is preferably positioned in such a way that it is located at a location where a magnetic gradient field undergoes changes in time during the execution of a magnetic resonance tomography. If the construction of the

If the magnetic resonance tomograph comprises an MRT tube, the energy collector is inserted into it. In the case of an open MRI system, for example in a C-shape, the

Energy collector accordingly inserted between the C-plates, between which the magnetic fields are generated. Due to the compact design, the energy collector can also be carried easily and flexibly by the patient.

The use of the electrical energy generated by the energy collector for operating at least one consumer device can be implemented in a variety of ways.

For example, the electrical energy generated can be used directly for the operation of the

Consumer device can be used. However, it can also be preferred that the electrical energy generated is temporarily stored in an accumulator, which is the

Consumer device supplied with energy.

DETAILED DESCRIPTION

The invention is to be explained in more detail below with the aid of examples, without being restricted to these.

Brief description of the images

Fig. 1 Functional principle for generating vibrations of a coupling element in the

Magnetic resonance imaging

Fig. 2 Acceleration measurement, vertical axis: a) inside the MRI tube at the top of

MRI housing; b) on a coupling element which is positioned on the bed

Fig. 3 Schematic representation of preferred embodiments of the energy collector

Fig. 4 Schematic illustration of a preferred use of the energy collector for generating electrical energy in magnetic resonance imaging

Fig. 5 a) Schematic representation of frequency spectra with different MRI

Investigations. b) Preferred embodiment of an energy collector with an array of coupling elements and electrical converters to cover several natural frequencies and detailed description of the images

Figure 1 shows the operating principle for generating the vibrations of the coupling element.

Three different magnetic fields are used in magnetic resonance imaging: a static magnetic field, clocked (i.e. time-changeable) magnetic gradient fields and high-frequency fields. The interplay of the magnetic fields is used for layer-by-layer imaging.

If a coupling element made of a conductive material (e.g. copper or aluminum) is placed in the tube of an MRT, eddy currents are induced in it due to the clocked gradient fields. The strong static magnetic field in the MRI tube now leads to a force effect on the coupling element. Therefore, the coupling element is set to vibrate according to the timing of the switching of the gradient fields (Figure 1). This chain of effects is e.g. also responsible for the noise development during an MRI examination if the current-carrying gradient coils experience a force effect in the static magnetic field.

Figure 2 shows experimental measurements of the vibrations that are generated by the clocked gradient fields in a typical MRI examination. The tests were carried out on an MR tomograph (3T-MRT Skyra, Siemens).

Figure 2a shows a frequency spectrum that was measured in the sky in the MRI tube in the vertical direction. In terms of quality, the spectrum shown also resembles spectra that were recorded in other directions and at different positions on the housing of the MRI tube. In particular, the spectra are characterized by dominant frequencies, which are lined up at the same distance and form harmonic harmonics. The frequencies are in a range of 100 Hz - 2 kHz with amplitudes (depending on the sequence) of up to 0.4 g.

Figure 2b shows an exemplary frequency spectrum of a coupling element, which was placed on a couch in the MRI tube. The coupling element is a copper sheet with a surface between 40 cm ² to 80 cm ² and a thickness of 1 to 2 mm. As Figure 2b shows, significantly higher acceleration amplitudes are measured on the coupling element than with a vibration measurement on the MRI housing or directly on the couch (without coupling element). According to analytical estimates based on the existing accelerations, powers of up to 50 mW can be generated.

Figure 3 illustrates preferred embodiments of an energy collector, which should use the previously described chain of effects.

In Fig. 3a, a preferred embodiment of an energy collector according to the first aspect of the invention is shown, wherein a coupling element via an elastic element (spring element) and an electromechanical transducer (electrical damper) within the energy collector connected to its housing. The coupling element, which experiences a force through the direct action of the changing gradient fields, can transmit this force directly to the elastic element or spring element, as a result of which an oscillation or vibration is generated. If the natural frequency of the oscillatory system is adapted to the excitation, a resonant one can Operation can be achieved, which leads to a particularly high effectiveness of energy conversion. The electromechanical transducers can be based on various transduction mechanisms. For example, the vibration can be damped by an electrostatic or a piezoelectric transducer and thus provide electrical energy.

Figure 3b shows the use of a piezoelectric beam structure (piezo beam) as the preferred electromechanical energy converter. The piezo bar is attached to the housing of the energy collector as a cantilever and is excited to vibrate by the vibrations of the coupling element. The resulting elastic deformations of piezoelectric layers convert the mechanical vibrations into electrical energy. The piezo bar thus combines the functionalities of an elastic element (cantilever) and an electrical damper (piezoelectric damping of the elastic deformations).

Figure 3c shows a preferred embodiment of an energy collector according to the second aspect of the invention. Here, the coupling element is mechanically connected to a classic vibration energy collector, so that the vibrations of the coupling element are transmitted directly to the vibration energy collector by a vibration within the housing. The vibration energy collector preferably comprises its own housing, in which there is a seismic mass, which is connected to the housing via an energy converter, preferably in the form of a spring-damper structure.

Figure 3d shows a preferred embodiment of an energy collector according to the third aspect of the invention. In the embodiment, the coupling element is a hollow body in the inner cavity of which a seismic mass is connected to the outer wall as an electromechanical transducer via a spring-damper structure. By stimulating the coupling element, the seismic mass is vibrated via the elastic element, so that energy is generated in the electromechanical transducer (electrical damper). The coupling element also preferably functions as a housing and has a magnetic shielding function, so that the energy converter and the seismic mass in the inner cavity interact only to a lesser extent with external magnetic fields. In this way, disruptive influences on the imaging when used in magnetic resonance tomography can be minimized.

Figure 4 illustrates a preferred use of the energy collector to generate electrical energy during an MRI scan. Due to the compact dimensions, the energy collector can be attached to the patient, so that the energy collector is located in the MRI tube together with the patient while a magnetic resonance tomography is being carried out. The energy obtained from the clocked gradient fields can be used for a wide variety of consumer systems, in particular for monitoring or communication with the patient.

Figure 5a) illustrates frequency spectra that occur in different MRI examinations. Depending on the medical indication or the tissue to be examined, different sequences (ie sequential applications of the high-frequency and gradient fields) can be used. The different sequences lead to different Chen frequencies of the circuits of the gradient fields during imaging, whereby the vibration spectra vary.

Figure 5a) illustrates the results of measurements for MRI examinations with different sequences. The harmonics of different sequences visible in the frequency spectrum are congruent or closely related. However, the amplitudes of the dominant frequencies can fluctuate significantly depending on the sequences. It can happen that dominant frequencies with only a small amplitude are found at a frequency f1 or with very different amplitudes at a frequency f2.

With regard to a specific harmonic (e.g. f2), the required frequency bandwidth B1, which must be covered by an energy collector, is relatively small (<10 Hz). The frequency spacing B2 of the harmonics is 50 Hz or 67 Hz depending on the sequence.

The natural frequency of an energy collector can be varied by up to 100 Hz using mechanical methods (Neiss 2014, Eichhorn 201 1, Floffmann 2016, Lallart 2010, Wang 2017) or by using extraction circuits by up to 10 Hz (Hsieh 2015, Cai 2018) .

In order to be able to efficiently harvest the energy at different frequencies, it may be preferable to use an array with several coupling elements (e.g. 2 to 5 coupling elements). Such a preferred embodiment is illustrated in FIG. 5b for the use of piezo bars as an electromechanical energy converter.

It should be noted that various alternatives to those described

Embodiments of the invention can be used to carry out the invention and to achieve the solution according to the invention. The embodiments of the energy collector according to the invention, the system and their use, in particular in the described methods, are therefore not limited to the above preferred embodiments.

Rather, a large number of design variants are conceivable, which can deviate from the solution shown. The aim of the claims is to define the scope of the invention. The scope of protection of the claims is aimed at covering the energy collector according to the invention, the system, their uses, in particular in the methods described, and equivalent embodiments thereof.

REFERENCE SIGN LIST

I energy collector

3 coupling element

5 electromechanical converter

7 Elastic element

9 Electrically damping element

I I housing

13 vibration energy collectors

15 Seismic mass

17 piezo bars

19 consumer devices

21 MRI tube

23 patient

BIBLIOGRAPHY

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C. Eichhorn, R. Tchagsim, N. Wilhelm, and P. Woias, “A smart and self-sufficient frequency tunable vibration energy harvester,” J. Micromech. Microeng, vol. 21, no.10, p. 104003, 201 1st

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Condition Monitoring of Maritime Gearboxes, ”in PowerMEMS, 2014, p. 012099.

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Electromagnetic Technologies - State of the Art, ”IEEE Trans. Ind. Electron, vol. 57, no.3, pp. 850-860, 2010.

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Claims

PATENT CLAIMS

1 . Energy collector (1) for the generation of electrical energy with time-changeable

Magnetic fields in particular for use in magnetic resonance imaging comprising a. a coupling element (3) for a time-varying magnetic gradient field b. a housing (11) and c. an electromechanical transducer (5), characterized in that

the coupling element (3) is made of an electrically conductive material and is connected to the housing (11) so that it can vibrate via the electromechanical transducer (5), the coupling element being set up in such a way that a time-changing magnetic gradient field induces eddy currents in its surface, which experience a force effect when a static magnetic field is superimposed, so that a temporally changing magnetic gradient field, when superimposed with a static magnetic field, excites the coupling element (3) to oscillate and generates electrical energy in the transducer (5).

2. Energy collector (1) for the production of electrical energy with time-changeable

Magnetic fields in particular for use in magnetic resonance imaging comprising a. a coupling element (3) for a time-varying magnetic gradient field b. a housing (11) c. an elastic element (7) and d. a vibration energy collector (13) characterized in that

the vibration energy collector (13) is connected to the coupling element (3), which is made of an electrically conductive material and is connected to the housing (11) in an oscillating manner via the elastic element, the coupling element being set up so that a time-changing magnetic Gradient field

Eddy currents are induced in its surface, which experience a force when a static magnetic field is superimposed, so that a magnetic gradient field that changes over time when excited with a static magnetic field excites the coupling element (3) to oscillate and generates electrical energy in the vibration energy collector (13).

3. Energy collector (1) for obtaining electrical energy in the case of time-variable magnetic fields, in particular for use in magnetic resonance imaging, comprising a. a coupling element (3) for a time-varying magnetic gradient field b. an electromechanical transducer (5) and c. a seismic mass (15) characterized in that

the coupling element (3) is a hollow body, the outer wall of which is made of an electrically conductive material and in the inner cavity of which the electromechanical transducer (5) and the seismic mass (15) are present, the seismic mass (15) being able to oscillate via the electromechanical Transducer (5) is connected to the outer wall of the coupling element (3), the coupling element being set up so that a time-changing magnetic gradient field eddy currents in its

Surface induced, which experience a force when a static magnetic field is superimposed, so that a time-changing magnetic

Gradient field when superimposed with a static magnetic field excites the coupling element (3) to oscillate and generates electrical energy in the electromechanical transducer (5).

4. Energy collector (1) according to one of the preceding claims

characterized in that

the conductive material is a paramagnetic or diamagnetic metal, particularly preferably selected from the group comprising aluminum, titanium and / or copper.

5. Energy collector (1) according to one of the preceding claims

characterized in that

the coupling element (3) is a hollow body, preferably an ellipsoidal hollow body, very particularly preferably a hollow ball.

6. Energy collector (1) according to one of the preceding claims

characterized in that

the ratio of the volume enclosed by the outer surface of the coupling element (3) and the mass of the coupling element (3) less than 10 g / cm ³ , preferably less than 1 g / cm ³ , particularly preferably less than 0.1 g / cm ³ and / or the material of the coupling element (3) has a density of less than 10 g / cm ³ .

7. energy collector (1) according to one of the preceding claims if dependent on

Claim 1 or 2 characterized in that the coupling element (3) is a sheet having a thickness of 0.5 mm to 3 mm, preferably 1 mm to 2 mm, and a surface area of 20 cm ² to 200 cm ^2, preferably 40 cm ² to 80 cm ^2.

8. Energy collector (1) according to one of the preceding claims

characterized in that

the electromechanical transducer (5) is a piezoelectric transducer or a

is an electrostatic converter.

9. energy collector (1) according to one of the preceding claims if dependent on

Claim 1 characterized in that

the housing (11), the electromechanical transducer (5) and the coupling element (3) form an oscillatable system which has at least one natural frequency between 100 and 2000 Hz, preferably between 200 and 2000 Hz, very particularly between 500 and 1000 Hz.

10. Energy collector (1) according to one of the preceding claims if dependent on

Claim 1 or 2 characterized in that

the energy collector (1) has at least two coupling elements (3), each of which is connected to the housing (11) by an electromechanical transducer (5) so that it can vibrate, preferably at least two systems capable of vibration which have different natural frequencies.

1 1. Energy collector (1) according to one of the preceding claims if dependent on

Claim 1 or 2 characterized in that

the housing (11) is made of a non-metallic material, preferably of a plastic.

12. Energy collector (1) according to one of the preceding claims

characterized in that

the energy collector (1) has at least one permanent magnet for building up a static magnetic field.

13. Use of an energy collector (1) according to one of the preceding claims for the generation of electrical energy from a time-changing magnetic gradient field in magnetic resonance imaging.

14. System comprehensive a. a magnetic resonance tomograph and a. an energy collector (1) according to one of the preceding claims 1-12

15. System according to the previous claim

characterized in that the magnetic resonance tomograph is set up for this generate a static magnetic field, a temporally changing magnetic gradient field and / or a high-frequency magnetic field during magnetic resonance tomography.

16. System according to the previous claim

characterized in that the static magnetic field has a field strength of at least 0.1 Tesla, preferably 0.1 to 10 Tesla, particularly preferably 0.5 to 3 Tesla.

17. System according to one of the preceding claims 15 or 16

characterized in that the temporally changing magnetic gradient field is generated by clocked switching of magnetic gradient fields which are used for spatial coding in the context of magnetic resonance tomography.

18. System according to the previous claim

characterized in that the clocked switching takes place at a frequency of 100 Hz to 2000 Hz.

19. System according to one of the preceding claims 14 to 18

characterized in that

the system comprises consumer devices (19), preferably for attachment to a patient (23), and the energy collector (1) is connected to the consumer devices (19) in order to supply them with energy.

20. A method for obtaining electrical energy in magnetic resonance imaging comprising the steps a. Providing an energy collector (1) according to one of claims 1 -12 b. Providing a magnetic resonance tomograph c. Positioning the energy collector (1) within the

Magnetic resonance tomograph, so that the energy collector (1) is located during a magnetic resonance tomography in a time-changing magnetic gradient field which is overlaid by a static magnetic field d. Use of the electrical energy generated by the energy collector (1) to operate at least one consumer device (19).