FIELD OF THE INVENTION

The invention relates to medical devices and procedures, in particular to a conductivity investigating device. BACKGROUND OF THE INVENTION

In the physical sciences and engineering, the knowledge of the units and magnitude of the physical quantities is of particular relevance for describing multiple aspects studied in physics. And, there is a continuous need to provide improved devices for investigating physical quantities.

SUMMARY OF THE INVENTION

Various embodiments provide for a device and a method for investigating the conductivity of a decorated skin area as described by the subject matter of the independent claims. Advantageous embodiments are described in the dependent claims.

In one aspect, the invention relates to a device (or a conductivity scanner) for investigating (or determining) the conductivity of a decorated skin area. The decorated skin area has a permanent pigmentation of the dermis of the decorated skin area. The device is configured for acquiring measurement data by measuring an electrical property of the dermis of the decorated skin area. The electrical property is indicative of the conductivity of the decorated skin area. The conductivity of the decorated skin area is a property of the decorated skin area.

A tattoo is a design created on the skin by the injection of pigment into the dermal layer of the skin, so it is visible through the skin surface. Tattoos and permanent make-up are increasingly popular. However, there is a need of systems that take into account and evaluate pigmentation of the skin.

The device may be a handheld device to assess to conductivity of the decorated skin area. The electrical property of the decorated skin area may comprise the impendence or the resistance of the decorated skin area. The resistance of the decorated skin area refers to the resistance between two electrodes when a current is steadily passed between them. The two electrodes are inserted or placed in the decorated skin area such that they penetrate fully the epidermis of the decorated skin area as the tattoo's ink is below the epidermis, in the dermis of the decorated skin area.

The present system and method may provide an easy-to-use technique for investigating the conductivity. For example, the device may be provided as a simple handheld device with which a radiologist or MRI technician can obtain an indication of the conductivity of an in- vivo tattoo or permanent make-up.

Considering as an example an eyeliner that has been applied around the eye. When conductive eyeliner is used, voltage above 100V may be induced by the radio frequency (RF) field of an MRI system, which can drive a current of several Amps. This current is large enough to cause first degree burns.

The term "skin area" refers to any skin area on the body of the subject human or animal, including scalp areas and including transitional areas between areas of hair growth and balding areas. A given skin area may be a decorated skin area if the given skin area has a tattoo and/or permanent make-up which is permanently marked on the given skin area.

In one example, the decorated skin area is provided with one or more indicia to facilitate successive processing or monitoring of the same decorated skin area for determining the conductivity of the decorated skin area.

According to one embodiment, the decorated skin area comprises at least one of: tattoos and permanent make-ups. Tattoos and/or permanent make-ups are permanently marked on the decorated skin area. MRI scanning of tattoos and/or permanent make-up may not be without risk, because the composition of the ink is not known at the time when an MRI Scan is due. In case the ink is conductive, there is a significant hazard risk related to radio frequency (RF) burns. Thus, investigating the conductivity of the decorated skin area may help avoiding such burns.

According to one embodiment, the device is further configured for determining the difference in conductivity between the decorated skin area and a predefined reference skin area. The reference skin area is a skin area of a subject, the decorated skin area is another skin area of the same subject. This may provide a relative measurement which may be more relevant compared to an absolute measurement.

According to one embodiment, the reference skin area comprises another decorated skin area or a non-decorated skin area, wherein the non-decorated skin area comprises an area surrounding the decorated skin area. This may provide a reliable reference for an accurate measurement. The another decorated skin area may be a decorated skin area that is previously processed by the device i.e. the conductivity of the another decorated skin area is investigated using the device.

According to one embodiment, the device comprises: at least one first needle that is configured to be inserted into a respective contact point in the decorated skin area to a predefined depth of penetration, and conductivity measuring electronics integrally formed with the at least one first needle for measuring the electrical property of the decorated skin area using the at least one first needle.

According to one embodiment, the device comprises a consumable or replacement part comprising the at least one first needle. The consumable part may be changed or replaced after a predefined usage time period. For example, after every examination, the consumable part may be replaced for hygienic reasons. The device comprises the consumable part and a non-consumable part. The non-consumable part comprises the conductivity measuring electronics.

The term "needle" refers to an object which may pierce the skin of a person. The needle may or may not be conductive. For example, if the needle itself is used as point of contact to the dermis of the decorated skin area then it may need to be conductive. If electrodes are deposited on the needle, then the needle itself can be non-conductive. A needle may have a solid or a hollow body of arbitrary shape with a sharp point on the end. In general, a needle has a pointed tip which pierces the skin.

A needle that is named "first needle" is a needle that is configured to be inserted or injected in the decorated skin area. The first needle may be inserted such that it penetrates fully the epidermis as the tattoo's ink is below the epidermis, in the dermis. The predefined depth of penetration may be a depth of the decorated skin area at which the ink is disposed.

The dermis is a connective tissue made up of collagen and networks of elastic fibers which give skin its resiliency. The dermis is the layer in which tattoo ink is deposited.

For example, the device may prompt a user of the device to provide indications of the contact points and may receive in response user inputs indicating the contact points. In another example, the contact points may be determined such that each pair of contact points is within the decorated skin area.

According to one embodiment, the device comprises a single first needle, wherein the conductivity measuring electronics comprise a pair of interdigital electrodes on the first needle. For example, in case it is difficult to position the device having two needles such that two needles can connect to the decorated skin area a different consumable with one needle can be used. In this case interdigit electrodes are located on the isolated needle. This embodiment may provide a further improved easy-to-use technique for investigating the conductivity.

According to one embodiment, the at least one first needle comprising two first needles, the device further comprising two reference needles, wherein the reference needles are configured to be inserted into the reference skin area to the predefined depth, the conductivity measuring electronics comprising a bridge circuit having two fixed resistances with predefined ohmic values and two other resistances representing resistances of two skin areas located between the two first needles and between the two reference needles respectively. This embodiment provides a relative measurement of the impedance or resistance, which may be the optimal information required .. For example, the bridge circuit of this embodiment comprises a Wheatstone bridge.

According to one embodiment, the at least one first needle comprising two first needles, the device further comprising one reference needle, wherein the reference needle is configured to be inserted into the reference skin area to the predefined depth, the conductivity measuring electronics comprising a bridge circuit having two fixed resistances with predefined ohmic values and two other resistances representing resistances of two skin areas located between the two first needles and between the reference needle and one of the two first needles respectively. This embodiment may provide a relative measurement with a more simplified device compared to the precedent embodiment. This embodiment may lead to a further simplification as one reference needle of the two reference needles can be omitted and one of the first needles can be used as reference for both the decorated skin area measurement and the normal skin measurement. For example, the bridge circuit of this embodiment comprises a Wheatstone bridge.

According to one embodiment, the device comprises two first needles, the conductivity measuring electronics comprise two poles of a power source connected to the first needles respectively. This embodiment may provide a simplified structure of the device.

According to one embodiment, the device is adapted to be located at a position on the exterior of the examination volume. The device comprises: one or two electrical coils for generating an inductive coupling in a way that the properties of the inductive coupling change if a current passes the decorated skin area, and a circuit connected to the electrical coils being adapted for detecting the changes of the inductive coupling, wherein the change in the coupling is indicative of the electrical property. This embodiment may enable a an investigation device which does not penetrate the skin and thus is non-invasive. According to further embodiments, the device comprises a coil arrangement comprising two coils. According to further embodiments, the two coils have axes that are substantially perpendicular to each other. A first electrical coil may produce a primary magnetic field, which is screened by the second electrical coil. According to further embodiments, the device comprises one or more capacitors to make the coil arrangement resonant. For example, both coils may be resonant at the same frequency (preferably in the same range as MRI scanners, e.g. 64 - 128 MHz). The first electrical coil may be excited by a power source. Due to electric (C) and magnetic (M) coupling a part of the power is transferred to the coil.

According to one embodiment, the device being further configured for:

enabling controlling an RF source for depositing RF fields in an examination volume in accordance the conductivity of the decorated skin area, the examination volume comprising the decorated skin area.

According to one embodiment, the RF source comprises a MRI system. This may enable an automatic control of the MRI system based on the conductivity of the decorated skin area. This embodiment may for example be performed during an MRI exam. By contrast to a conventional method, this embodiment may reduce the number of user interventions to a minimum.

In another aspect, the invention relates to a method for investigating the conductivity of a decorated skin area. The decorated skin area has a permanent pigmentation of the dermis of the decorated skin area. The method comprises: acquiring measurement data by measuring an electrical property of the decorated skin area. The electrical property is indicative of the conductivity of the decorated skin area.

According to one embodiment, the method further comprises providing measurement data to a controller of the MRI system, and using the measurement data for controlling the MRI system for scanning an examination volume in order to avoid a radio frequency burn of the examination volume, the examination volume comprising the decorated skin area.

According to one embodiment, the controlling of the MRI system comprises one of: switching off the MRI system; controlling the MRI system such that the energy induced in the decorated skin area is limited to a predefined maximum energy. For example, the controlling of the MRI system may be obtained by setting a limit to the local SAR value in the user interface of the scanner (this can be done manually by the operator) or automatically. According to one embodiment, the method is performed in real-time.

Magnetic resonance image data is defined herein as being the recorded measurements of radio frequency signals emitted by atomic spins by the antenna of a Magnetic resonance apparatus during a magnetic resonance imaging scan. A Magnetic Resonance Imaging (MRI) image is defined herein as being the reconstructed two or three dimensional visualization of anatomic data contained within the magnetic resonance imaging data. This visualization can be performed using a computer.

It is understood that one or more of the aforementioned embodiments of the invention may be combined as long as the combined embodiments are not mutually exclusive.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following preferred embodiments of the invention will be described, by way of example only, and with reference to the drawings in which:

Fig. 1 shows a cross-sectional view of an exemplary device for investigating the conductivity,

Fig. 2 shows a cross-sectional view of another exemplary device for investigating the conductivity,

Fig. 3 is a schematic diagram of an electrical circuit arrangement of another exemplary device for investigating the conductivity,

Fig. 4 depicts an experimental setup with of a coil arrangement of another exemplary device for investigating the conductivity,

Fig. 5 is a flowchart of a method for investigating the conductivity of decorated skin area, and

Fig. 6 shows a cross-sectional and functional view of an MRI system.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following, like numbered elements in the figs, are either similar elements or perform an equivalent function. Elements which have been discussed previously will not necessarily be discussed in later figs, if the function is equivalent.

Various structures, systems and devices are schematically depicted in the figs, for purposes of explanation only and so as to not obscure the present invention with details that are well known to those skilled in the art. Nevertheless, the attached figs, are included to describe and explain illustrative examples of the disclosed subject matter. Fig. 1 depicts an embodiment of a device (or conductivity scanner) 100 for measuring or determining the conductivity of a decorated skin area 130 of a subject (e.g. a person) in accordance with the present disclosure. The decorated skin area 130 may be a portion of the skin of a subject or patient. The decorated skin area may for example comprise tattoos and/or permanent make-ups. The decorated skin area 130 has a permanent pigmentation of the dermis of the decorated skin area.

The device 100 comprises conductivity measuring electronics 101 and two needles 103 A-B forming two electrodes. Each of the needles 103 A-B has a respective proximal end 105 A-B and distal end 107 A-B. The distal ends 107 A-B are connected to a respective terminal 108A-B. The connection to the terminals 108A-B may for example be performed using connection means. The connection means may for example comprise two conductive (e.g. cylindrical) objects and spring means disposed on top of the cylindrical objects. This may provide a galvanic contact between the disposable needles or electrodes on the needles and the non-disposable electric circuitry.

In another example, the distal ends 107A-B may directly be connected to the terminals 108A-B. Both needles are placed in different spots on the decorated skin area 130.

For providing a flexible device the device 100 may be split in two parts. The upper part contains the conductivity measuring electronics 101 and the lower part is a consumable with needles. After every examination the part with the needles may for example be replaced for hygienic reasons. As illustrated in Fig. 1, the lower part may be a detachable unit.

The conductivity measuring electronics 101 may comprise a power source 121 for supplying electric power (alternating current and/or direct current) to the two electrodes or needles 103 A-B, a control unit 123 which controls the power source with an integrated Volt meter 121, an Ampere meter 122 and a display or indicator 124 for displaying the measurement results and the like. The needles 103 A-B are connected to the power source 121 and the Ampere meter 122.

The power source 121 is configured to apply a current (direct current or alternating current) to the decorated skin area 130 through the needle 103 A and the needle 103B. The power source 121 applies a current to the decorated skin area with the needle 103 A functioning as a negative electrode and the needle 103B functioning as a positive electrode. The voltmeter of the power sourcel21 is configured to measure the voltage between the needlel03A and needle 103B when a current (e.g. alternating current) is applied to the decorated skin area 130 through the needles 103 A-B from the power source 121. The value measured by the voltmeter is input to the control unit 123. The control unit 123 calculates the impedance of the decorated skin area 130 using the voltage value received from the power source with Volt meter 121, and a current value that is measured by and received from the Ampere meter 122. The control unit 123 calculates the conductance of the decorated skin area based on the calculated impedance value. The conductance and/or corresponding conductivity may be displayed on the display 124.

The determined conductivity may for example be compared with a reference conductivity value, wherein the reference conductivity value comprises the conductivity of a reference skin area (e.g. a non-decorated skin area of the same subject). For example, the difference between the determined conductivity and the reference conductivity value may be provided as the conductivity value of the decorated skin area. This may be advantageous because if the decorated skin area is conductive the impedance/resistivity may be much lower than with non-conducting decorated skin area or with a non-decorated skin area.

Each of the needles 103A-B may be configured to be inserted in the decorated skin area 130. Fig.l shows the depth of penetration 131 of the needles 103A-B. The needles 103A-B may be inserted such that they penetrate fully the epidermis 133 as the tattoo's ink is below the epidermis 133, in the dermis 135. The predefined depth of penetration may be a depth of the decorated skin area at which the ink is disposed.

In another embodiment of the device for investigating the conductivity, Fig. 2 depicts device 200 comprising a single needle 205. The device of Fig.2 is the device of Fig. l where two needles 103A-B are replaced with a single needle 205 and where the connection to the terminals is performed via electrodes 207 and 209. The electrodes 207-209 are configured in the form of two interdigital electrodes engaging in one another. The far ends of the electrodes 207-209 are connected to the terminals 108A-B, by means of which the electrodes 207-209 are connected to the power source 121 and Ampere meter 122.

As described above, the power source 121 is configured to apply a current (direct current or alternating current) to the decorated skin area 130 through the electrodes 207 and 209. The power source 121 applies a current to the decorated skin area with the electrode 207 functioning as a negative electrode and the electrode 209 functioning as a positive electrode. The voltmeter of the power source 121 is configured to measure the voltage between the electrode 207 and electrode 209 when a current (alternating current) is applied to the decorated skin area 130 through the electrodes 207-209 from the power source 121. The value measured by the voltmeter of the power source 121 is input to the control unit 123. The control unit 123 calculates the impedance of the decorated skin area 130 using the voltage value received from the voltmeter of the power source 121, and a current value that is measured by and received from the Ampere meter 122. The control unit 123 calculates the conductance of the decorated skin area based on the calculated impedance value. The conductance or corresponding conductivity may be displayed on the display 124.

The determined conductivity (of Fig. 2) may for example be compared with a reference conductivity value, wherein the reference conductivity value comprises the conductivity of a reference skin area e.g. a non-decorated skin area. For example, the difference between the determined conductivity and the reference conductivity value may be provided as the conductivity value of the decorated skin area.

For example, needles 103A-B and 205 of the examples of Fig. 1 and Fig. 2 may comprise micro-needles. Instead of normal needles, similar to those used for intervenous injections, micro needles can be used, which only penetrate the highly insulating top layer (epidermis) of the decorated skin area.

Fig. 3 is a schematic diagram of the electrical circuit arrangement 300 forming at least part of a conductivity measuring electronic of another example of the device for investigating the conductivity. In this example, the device (e.g. 100 and 200) comprises 4 needles. Two needles are configured to be placed or inserted in the decorated skin area 130 and two other needles are configured to be placed or inserted outside the decorated skin area e.g. in a non- decorated (normal) skin area.

The electrical circuit arrangement 300 comprises a bridge circuit such as a

Wheatstone bridge. The bridge circuit 300 comprises two known or fixed resistances 302 and 303 and two unknown resistances 306 and 307. The unknown resistance 306 is a resistance loop formed between the needles placed in the decorated skin area 130. The unknown resistance 306 is a resistance loop formed between the two needles placed outside the decorated skin area 130. The electrical circuit arrangement 300 further comprises a battery 313 that is connected to two opposite points of the bridge circuit. The electrical circuit arrangement 300 further comprises a current detector 315 of a predefined resistance that is connected between terminal points 305B and 309B.

The needles placed on the decorated skin area 130 may be connected to respective terminals 305 A-B of the bridge circuit 300. The connection to terminals 305A-B may be performed using connection means as described above with reference to Fig.l . The needles placed on the non-decorated skin area may be connected to respective terminals 309A-B of the bridge circuit 300 e.g. using connection means as described above with reference to Fig. 1. A current may be applied by battery 313 to the decorated skin area 130 through the needles that are connected to the terminals 305A-B and to the non-decorated skin area through the needles that are connected to the terminals 309A-B. By measuring either the voltage or the current across the centre of the bridge 300 the unknown resistances can be determined. The values measured between the terminals 309A-B may provide reference values of the conductivity of the non-decorated skin area while values measured between the terminals 305A-B may provide conductivity of the decorated skin area. The differential comparator 311 may provide g a relative measurement of the conductivity of the decorated skin area 130.

In an alternative example of the conductivity measuring electronic of Fig.3, only three needles may be used instead of four needles. For example, needle that is connected to terminal 308A can be omitted and the needle that is connected to terminal 305A can be used as reference for both the decorated skin area measurement and the normal skin measurement.

Fig. 4 depicts an experimental setup with of a coil arrangement 400 for performing noninvasive resonance measurement. The coil arrangement 400 may be part of a device for investigating the conductivity. The coil arrangement 400 comprises two coils 401 and 403. The two coils 401, 403 may for example have axes that are perpendicular to each other. The coil 401 may produce a primary magnetic field, which is screened by the receiving coil 403. Fig.4 shows an example circuit of each of the coils 401 and 403. The two coils 401 and 403 comprise respective capacitors 407 and 409 to make the coil arrangement 400 resonant. For example, both coils 401 and 403 may be resonant at the same frequency (preferably in the same range as MRI scanners, e.g. 64 - 128 MHz). The coil 403 is excited by a power source 411. Due to electric (C) and magnetic (M) coupling a part of the power is transferred to the coil 401.

In this example, the coupling (as illustrated by doted lines) between two coils 401, 403 is changed due to neighbouring electrical conductive material. If an electrically conductive material is in the neighbourhood of the coils 400 the magnetic field of the coil 403 is distorted and the net flux through the receiving coil 401 does not equal zero which means that a voltage is induced. In other terms, when a conductive object is brought near by the coupling changes, thereby changing the amount of power transferred and/or the frequency at which coupling is maximal. The conductivity of the decorated skin area 130 is determined by a change in coupling of the two coils when moving the coil arrangement 400 in proximity of the decorated skin area 130

(e.g. moving the coil arrangement 400 from skin areas without the tattoo to skin areas with the tattoo). For example, the coil arrangement 400 may be moved at a predefined distance 405 e.g. 3cm.

In another example, the coil arrangement 400 may comprise a single coil (e.g. a single resonant loop) instead of two coils 401-403. In this example, a magnetic field produced by the current within the single coil induces eddy currents in the decorated skin area 130. The single coil may be combined with an impedance measurement. If a conductive object is brought close to the single coil its impedance changes.

Fig. 5 is a flowchart of a method for investigating the conductivity of a decorated skin area e.g. 130.

In step 501, measurement data may be acquired by measuring an electrical property of the decorated skin area e.g. using the device for investigating the conductivity as described above with reference to Figs. 1-4. The electrical property is indicative of the conductivity of the decorated skin area 130.

In step 503, the measurement data may be provided (e.g. sent) to a controller of a RF source for depositing RF fields in an examination volume that comprises the decorated skin area in accordance with the conductivity. For example, the RF source may be an MRI system as described with reference to Fig. 6.

In case of the MRI system, the measurement data may be used by the controller for controlling the MRI system for scanning an examination volume (e.g. of a patient) in order to avoid a radio frequency burn of the examination volume. The examination volume comprises the decorated skin area 130. The controlling of the MRI system may comprise one: switching off the MRI system; controlling the MRI system such that the energy induced in the decorated skin area is limited to a predefined minimum energy.

Fig. 6 illustrates a magnetic resonance imaging system 600. The magnetic resonance imaging system 600 comprises a magnet 604. The magnet 604 is a

superconducting cylindrical type magnet with a bore 606 in it. The use of different types of magnets is also possible; for instance it is also possible to use both a split cylindrical magnet and a so called open magnet. A split cylindrical magnet is similar to a standard cylindrical magnet, except that the cryostat has been split into two sections to allow access to the iso- plane of the magnet. Such magnets may for instance be used in conjunction with charged particle beam therapy. An open magnet has two magnet sections, one above the other with a space in-between that is large enough to receive a subject 618 to be imaged, the arrangement of the two sections area similar to that of a Helmholtz coil. Inside the cryostat of the cylindrical magnet there is a collection of superconducting coils. Within the bore 606 of the cylindrical magnet 604 there is an imaging zone or volume 608 where the magnetic field is strong and uniform enough to perform magnetic resonance imaging.

Within the bore 606 of the magnet there is also a set of magnetic field gradient coils 610 which is used during acquisition of magnetic resonance data to spatially encode magnetic spins of a target volume within the imaging volume or examination volume 608 of the magnet 604. The examination volume 608 comprises the decorated skin area 130 which in the skin of the subject 618. The magnetic field gradient coils 610 are connected to a magnetic field gradient coil power supply 612. The magnetic field gradient coils 610 are intended to be representative. Typically magnetic field gradient coils 610 contain three separate sets of coils for the encoding in three orthogonal spatial directions. A magnetic field gradient power supply supplies current to the magnetic field gradient coils. The current supplied to the magnetic field gradient coils 610 is controlled as a function of time and may be ramped or pulsed.

MRI system 600 further comprises an RF coil 614 at the subject 618 and adjacent to the examination volume 608 for generating RF excitation pulses. The RF coil 614 may include for example a set of surface coils or other specialized RF coils. The RF coil 614 may be used alternately for transmission of RF pulses as well as for reception of magnetic resonance signals e.g., the RF coil 614 may be implemented as a transmit array coil comprising a plurality of RF transmit coils. The RF coil 614 is connected to one or more RF amplifiers 615.

The magnetic field gradient coil power supply 612 and the RF amplifier 615 are connected to a hardware interface 628 of computer system 626. The computer system 626 further comprises a processor 630. The processor 630 is connected to the hardware interface 628, a user interface 632, a computer storage 634, and computer memory 636.

The computer memory 636 is shown as containing a control module 660. The control module 660 contains computer-executable code which enables the processor 630 to control the operation and function of the magnetic resonance imaging system 600. It also enables the basic operations of the magnetic resonance imaging system 600 such as the acquisition of magnetic resonance data. The MRI system 600 may be configured to acquire imaging data from the patient 618 in calibration and/or physical scans. The control module 660 may comprise instructions that when executed by the processor 630 cause the processor to perform at least part of the method of Fig.5 by for example controlling the MRl system 600 to scan the examination volume 608 based on the conductivity of the decorated skin area that is part of the examination volume 608. The conductivity of the decorated skin area may for example be received by the control module 660 from the device 100 or may be received from a user of the device 100.

For example, the method and device described above can be used as an accessory to MRl scanners e.g. MRl system 600 for determining the conductivity of a tattoo or permanent make-up in order to increase MR safety.

LIST OF REFERENCE NUMERALS

100 device

101 conductivity measuring electronics

103A-B first needles

105A-B proximal end

107A-B distal end

108A-B terminal

121 power source

122 Ampere meter

123 control unit

124 display

130 decorated skin area

131 depth

133 epidermis

135 dermis

200 device

205 first needle

207-209 electrodes

300 electrical circuit arrangement

302 resistance

303 resistance

305A-B terminal

306 resistance

307 resistance

309A-B terminal

311 differential comparator

313 battery

315 resistance

400 coil arrangement

401 coil

403 coil

405 distance

407 capacitor 409 capacitor

41 1 power source

501-503 steps

600 magnetic resonance imaging system

604 magnet

606 bore of magnet

608 imaging zone

610 magnetic field gradient coils

612 magnetic field gradient coil power supply

614 radio-frequency coil

615 RF amplifier

618 subject

03626 computer system

628 hardware interface

630 processor

632 user interface

634 computer storage

636 computer memory

660 control module.