Locating errors in power or signal lines of MRI systems

Abstract

The present invention relates to the field of magnetic resonance and, in particular, to determining the location of an error in a power supply line or signal line (12). Due to the harsh environment of an MR system (10) in a hospital, the power supply line or signal line (12) of the MR system (10) is prone to errors. For maintainability and part replacement, it is important to locate the error in the power supply line or signal line (12) or to identify the subunit (14, 16, 18, 20) of the power supply line or signal line (12) where the error occurs. The basic idea of ​​the present invention is to use an additional impedance (24) coupled to the power supply line or signal line (12) of the MR system (10) in an interconnection region (22) for locating the error in the power supply line or signal line (12). The additional impedance provides a reference impedance value. By measuring the impedance and comparing the measured impedance with the reference impedance value, the error in the power supply line or signal line (12) can be located. In one embodiment, the additional impedance (24) is implemented as an additional capacitance and is provided as a capacitor (28).

Description

Technical Field

[0001] The present invention relates to the field of magnetic resonance (MR) and, in particular, to determining the location of errors in power or signal lines of a magnetic resonance system. Background Art

[0002] EP 1 126 283 A1 describes a method for locating cable breaks in cables, including optical fiber cables. The conductive shield or armor of the cable is divided into several sections, typically at a joint. A step function voltage is applied to one end of the conductive shield. Remote sensors at the end of each section monitor the voltage and current as a function of time and at steady state. The measurement data are encoded as current pulses and transmitted along the armor to the cable end. A computer at the cable end calculates the capacitance of each section of the shield based on the measured voltage and current. The broken section is identified by comparing the calculated capacitance of the section with the original capacitance, and the distance along the broken section to the break is calculated based on the calculated capacitance of the broken section and the original capacitance.

[0003] US patent US 5 551 430 discloses an RF coil identification interface having a coil plug having a housing block with five RF contacts and providing a single coil identification resistor in the connected RF coil. Summary of the Invention

[0004] Conventional MR coils are complex devices that use electronics within the coil to provide MR-specific functions such as signal amplification, coil detuning, A / D conversion, signal processing, and digital transmission. To support these functions, one or more power sources (i.e., power cables or signal cables) need to be connected to the coil to supply the desired voltage and / or power. The power cables or signal cables typically include several subunits, such as a power source, a cable to a coil connector (receptacle) at the patient table, a coil cable, potentially with a plug, and the electronics within the coil.

[0005] Due to the harsh environment of hospital MR systems, these power cords are prone to errors. If a coil problem occurs, the faulty subunit of the corresponding power cord needs to be located and replaced by service personnel. However, if the error is in the passive components, that is, in the cables and connectors involved, there is no reliable way to locate the error. In particular, these methods are not accurate enough to distinguish between errors assigned just before or just after the interconnection of two subunits, which is crucial for component replacement. Therefore, tedious additional tests must be performed by exchanging one or the other subunit to see if the error still exists. Similar problems can arise for signal lines that include several interconnected subunits.

[0006] It is therefore an object of the present invention to provide a means for locating errors along power or signal lines for simplified maintainability.

[0007] According to the invention, this object is solved by the subject matter of the independent claims. Preferred embodiments of the invention are described in the dependent claims.

[0008] Thus, according to the present invention, a magnetic resonance system is provided that includes a power supply line or a signal line, wherein the power supply line or the signal line includes a plurality of interconnected subunits, and wherein, in the interconnected region, an additional impedance is coupled to the power supply line or the signal line. Preferably, the power supply line or the signal line is a line for supplying voltage and / or power to one or more MR coils or a signal line for conveying a signal.

[0009] Furthermore, the present invention relates to a method for locating an error in such a power supply line or signal line of a magnetic resonance system, wherein the power supply line or signal line comprises several interconnected subunits, and wherein an additional impedance is coupled to the power supply line or signal line in the region of the interconnection, and wherein the additional impedance provides a reference impedance value, the method comprising the following steps:

[0010] a) measure impedance, and

[0011] b) Determine the location of the error by comparing the measured impedance with a reference impedance value.

[0012] The basic concept of the present invention is to use an additional impedance, which is coupled to a power supply line or signal line in an interconnection region, for locating errors in the power supply line or signal line. The term additional impedance indicates that the additional impedance is not required for the operational capability of the MR system or the operational capability of the power supply line or signal line itself. The impedance required for the operational capability of the MR system or the operational capability of the power supply line or signal line performs a dedicated function for the operation of the MR system or the operation of the power supply line or signal line. Preferably, the dedicated function of the additional impedance is to add a defined impedance value for locating errors in the power supply line or signal line. Thus, the additional impedance provides a defined reference value that can be preset to a desired number. Preferably, the additional impedance has a defined value that is selected so as not to interfere with the power supply function and / or the MR system function.

[0013] The subunits are interconnected along power lines or signal lines. For example, the interconnection region includes a region where two subunits are interconnected and a region where ends of the power lines or signal lines are connected to another part (eg, a part of the MR system).

[0014] For example, an error in a power line or signal line may be an open circuit fault (such as a cable break), or it may be a short circuit. The error may of course occur in any of the subunits. The coupling of the additional impedance allows determination of the subunit in which the error occurred. The location of the error can be determined by measuring the impedance. By measuring the impedance and comparing the measured impedance with a reference value of the additional impedance, it is possible to determine the subunit in which the error is located. Since the additional impedance is coupled to the power line or signal line in the interconnection area, it is possible to reliably distinguish between errors distributed in two adjacent subunits.

[0015] The power or signal line of the MR system can be connected to a power supply, or the power supply can be a subunit of the power or signal line. Furthermore, the power or signal line can be a power line or a signal transmission line, or a combination of both. Examples of subunits in the MR system include a cable, a coil connector, a coil cable with a plug, or coil electronics or portions of coil electronics. Preferably, the subunits of the power or signal line are configured such that they are independently replaceable.

[0016] The device for measuring impedance can be incorporated into the MR system. Alternatively, the device for measuring impedance can be portable and therefore does not necessarily have to be incorporated into the MR system. For example, a portable device for measuring impedance can be used by a technician or by a service person to locate errors in power lines or signal lines. By measuring the impedance, the change in impedance compared to a reference value of the additional impedance indicates the location of the error in the power line or signal line. Therefore, it is not necessary to perform tedious additional tests by exchanging one or another subunit to check whether the error persists. Therefore, it is possible to reliably locate the error by impedance measurement, and maintainability is highly simplified. The basic idea of ​​using additional impedance to locate errors in the interconnect area can be used for devices and / or systems that must reliably transmit power via passive components (e.g., cables and connectors).

[0017] According to one embodiment of the present invention, the subunits include connectors, and the additional impedance is integrated into the connectors. Preferably, the connectors interconnect the subunits with each other and / or connect power or signal cables to other components of the MR system. Thus, the connectors are located in the area where the power or signal cables are interconnected. Integrating the additional impedance into the connectors is easy to implement. Furthermore, the easily accessible connectors simplify maintenance.

[0018] According to one embodiment of the present invention, the additional impedance is provided as a capacitor, a resistor, an inductor, and / or a resonant circuit. The additional impedance can be implemented as additional capacitance, additional resistance, additional inductance, and / or an additional LC combination. Preferably, the additional impedance is implemented as additional capacitance and provided as a capacitor. An ideal capacitor has a purely imaginary impedance and therefore only shifts the phase angle of the voltage and current in response to the applied power. More preferably, and particularly for power or signal lines that predominantly carry a constant supply current, the capacitor has a capacitance of approximately 100 pF to 1 nF. This capacitance value allows the function of the power or signal lines of the MR system to be uninterrupted and enables reliable location of the error. The capacitor can be incorporated into the connector. Implementing the additional impedance as an additional LC combination is particularly advantageous when combining the additional impedance with swept-frequency impedance measurement. The location of the error along the power or signal line can be determined by considering the number of resonant frequencies and the resonant frequency of the LC combination.

[0019] According to one embodiment of the present invention, the additional impedance is connected in parallel with the power line or signal line in the interconnection area. This indicates that the additional impedance is not connected along a single conductive path of the power line or signal line but is connected in parallel, that is, the additional impedance is connected along multiple paths of the power line or signal line. This is advantageous when the additional impedance is implemented as additional capacitance and provided as a capacitor or when the additional impedance is implemented as an additional LC combination and provided as a resonant circuit. In this case, it is possible to easily determine the location of an open circuit fault (such as a cable break) as an error in the power line or signal line.

[0020] According to one embodiment of the present invention, an additional impedance is connected in series to the power line or signal line in the interconnect region. This indicates that the additional impedance is connected along a single conductive path of the power line or signal line. This is advantageous when the additional impedance is implemented as an additional inductor and provided as an inductor. In this case, the location of a short circuit, such as a fault in the power line or signal line, can be easily determined.

[0021] According to one embodiment of the present invention, at least one additional impedance is coupled to the power line or signal line in each interconnect region. Therefore, the number of additional impedances is preferably equal to, or greater than, the number of subunits. This facilitates locating errors in the power line or signal line. Of course, errors in the power line or signal line can occur in any subunit. To distinguish errors in one subunit from errors in an adjacent subunit and to determine the exact subunit in which the error occurred, it is advantageous to couple at least one additional impedance to the power line or signal line in each interconnect region. Preferably, at least one additional impedance, and more preferably two additional impedances, are coupled to the power line or signal line in each subunit.

[0022] According to an embodiment of the present invention, a magnetic resonance system includes a power supply and an impedance measuring device, wherein the impedance measuring device is integrated into the power supply. Incorporating the impedance measuring device into the MR system's power supply is advantageous for simplified serviceability. By connecting the power supply or signal line to the power supply, the impedance can be measured using the impedance measuring device. This makes it possible to locate faults in the power supply or signal line. Consequently, service personnel do not need to carry a portable impedance measuring device. The integration of the impedance measuring device eliminates the risk of forgetting the portable impedance measuring device.

[0023] According to one embodiment of the present invention, the additional impedance is provided as a high-resistance sensing wire coupled to a power line or signal line in the interconnect region, or as a network of high-resistance sensing wires coupled to the power line or signal line in the interconnect region. In other words, the additional impedance can be implemented as an additional resistor. Preferably, the high-resistance sensing wire has a resistance of at least 1 kΩ / m. This resistance value is advantageous because the magnetic field of the MR system's coil does not induce excessive current in the sensing wire, thereby reducing the risk of damage to the MR system or injury to the patient.

[0024] In order to easily locate errors in the power line or signal line, it is advantageous to couple several different sensing wires to the power line or signal line. Alternatively, a network of high-resistance sensing wires can be coupled to the power line or signal line. In addition, an additional resistor can be connected to the high-resistance sensing wire or the network of high-resistance sensing wires to further add additional impedance. This increases the difference in measured impedance at different error locations in the power line or signal line and simplifies the determination of the error location. The high-resistance sensing wire can, for example, be made of a material with low electrical conductivity (preferably an alloy), or can be made of a very thin conductive material (for example, a thin metal surface as a conductive material covering a non-conductive material and / or a filament).

[0025] According to one embodiment of the present invention, a method for locating errors in a power line or signal line of a magnetic resonance system further includes the step of coupling an additional impedance to the power line or signal line in an interconnected region. Coupling multiple additional impedances to the power line or signal line is advantageous in order to distinguish errors distributed in one subunit from errors distributed in adjacent subunits. Preferably, at least one additional impedance is coupled to the power line or signal line in each subunit or in each interconnected region. More preferably, two additional impedances are coupled to the power line or signal line in each subunit.

[0026] According to one embodiment of the present invention, the step of measuring impedance includes measuring the impedance of a power supply line or a signal line. Preferably, the impedance measurement is integrated into the power supply of the MR system. More preferably, the step of measuring the impedance of the power supply line or the signal line includes connecting the power supply line or the signal line to a power supply and measuring the voltage and current of the power supply line or the signal line as a function of time. Furthermore, the impedance can be measured by continuously applying a sinusoidal signal above the power supply voltage, by sequentially applying small jumps in the power supply voltage and measuring the time response, and / or by sequentially applying a frequency sweep and measuring the spectral response.

[0027] According to one embodiment of the present invention, the step of measuring impedance includes measuring the impedance between a high-resistance sensing wire and a power line or signal line. For example, a voltage can be sensed via the high-resistance sensing wire and the power line or signal line, ensuring that the input impedance of the impedance measuring device is sufficiently high. Alternatively, the resistance between the high-resistance sensing wire and the power line or signal line can be measured. If an error exists in a power line or signal line assigned to one of the subunits, different impedance measurements are made for different error assignments. Thus, the location of the error in the power line or signal line can be determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. However, such embodiments do not necessarily represent the full scope of the invention, and reference is therefore made to the claims and herein for interpreting the scope of the invention.

[0029] In the attached figure:

[0030] Figure 1 schematically depicts a possible embodiment of a magnetic resonance system comprising a power supply line, wherein the additional impedance is provided as a capacitor;

[0031] Figure 2 schematically depicts another possible embodiment of a magnetic resonance system comprising a power supply line, wherein the additional impedance is provided as a high resistance sensing wire; and

[0032] Figure 3 Another possible embodiment of a magnetic resonance system comprising a signal line is schematically depicted, wherein the additional impedance is provided as a network of high-resistance sensing wires.

[0033] Reference Signs List

[0034] Magnetic resonance system 10

[0035] Power line or signal line 12

[0036] Subunit, power supply, first signal transmission line 14

[0037] Subunit, coil connector cable, second signal transmission line 16

[0038] Subunit, coil cable, third signal transmission line 18

[0039] Subunit, coil electronics 20

[0040] Interconnection area 22

[0041] Additional impedance 24

[0042] Connector 26

[0043] Capacitor 28

[0044] Resistor, high resistance sensing wire 30

[0045] Power Supply 32

[0046] Impedance measurement equipment DETAILED DESCRIPTION

[0047] Figure 1 A possible embodiment of a magnetic resonance system 10 as disclosed herein is depicted. The MR system 10 includes a power cord 12 for transmitting power to coil electronics 20 within the coil, which provide MR-specific functions such as signal amplification, coil detuning, A / D conversion, signal processing, and digital transmission. The power cord 12 includes several subunits 14, 16, 18, and 20. In this embodiment, the subunits are the power supply 14, the coil connector cable 16, the coil cable 18, and the coil electronics 20.

[0048] The subunits 14, 16, 18, 20 are interconnected, i.e., the power supply 14 is connected to the coil connector cable 16, the coil connector cable 16 is connected to the coil cable 18, and the coil cable 18 is connected to the coil electronics 20. In the interconnection region 22 of the two subunits, i.e., in the region 22 where the power supply 14 is connected to the coil connector cable 16, in the region 22 where the coil connector cable 16 is connected to the coil cable 18, and in the region 22 where the coil cable 18 is connected to the coil electronics 20, an additional impedance 24 is coupled to the power supply line 12.

[0049] exist Figure 1In the embodiment depicted in FIG, the additional impedance 24 is implemented as an additional capacitance and is provided as a capacitor 28. Capacitor 28 is connected in parallel to the power supply line 12 in the interconnection region 22. In this embodiment, the subunits 14, 16, 18, 20 include a connector 26 for interconnecting the subunits 14, 16, 18, 20 to each other. Capacitor 12 is integrated into connector 26. Capacitors 28 each have a capacitance of approximately 100 pF to 1 nF; a capacitance that is small enough not to interfere with the function of the power supply line 12 and the MR system 10, and a capacitance that is high enough for reliable location of errors.

[0050] Furthermore, the MR system 10 includes an impedance measuring device 34 integrated into the power supply 14. For example, the impedance measuring device may be an LCR meter (inductance (L), capacitance (C), and resistance (R)). The LCR meter can measure the inductance, resistance, and capacitance of a component, and from these values, the impedance at any frequency can be determined. For example, to measure the impedance of the power supply line 12, the voltage and current of the power supply line 12 can be measured as a function of time. By measuring the impedance of the power supply line 12, the location of the fault in the power supply line 12 can be determined. Figure 1 For the MR system 10 depicted in FIG, assuming ideal (lossless) components, the relationship between the position of the error in the power line 12 and the measured capacitance is, for example, as follows:

[0051]

[0052]

[0053] Figure 2 Another possible embodiment of a magnetic resonance system 10 as disclosed herein is depicted. The MR system 10 includes a power cord 12 for transmitting power to coil electronics 20 within the coil, which provide MR-specific functions such as signal amplification, coil detuning, A / D conversion, signal processing, and digital transmission. The power cord 12 includes several subunits 14, 16, 18, 20, which in this embodiment are the power supply 14, the coil connector cable 16, the coil cable 18, and the coil electronics 20.

[0054] The subunits 14, 16, 18, 20 are interconnected, i.e., the power supply 14 is connected to the coil connector cable 16, the coil connector cable 16 is connected to the coil cable 18, and the coil cable 18 is connected to the coil electronics 20. In the interconnection region 22 of the two subunits, i.e., in the region 22 where the power supply 14 is connected to the coil connector cable 16, in the region 22 where the coil connector cable 16 is connected to the coil cable 18, and in the region 22 where the coil cable 18 is connected to the coil electronics 20, an additional impedance 24 is coupled to the power supply line 12.

[0055] exist Figure 2In the depicted embodiment, the additional impedance 24 is implemented as an additional resistor and provided as a high-resistance sense wire 30. In this embodiment, one high-resistance sense wire 30 is coupled to each interconnect region 22, so three high-resistance sense wires 30 are used to locate errors in the power line 12. The high-resistance sense wire 30 is coupled to one path of the power line 12. However, it is possible to equip each path of the power line 12 with a high-resistance sense wire 30. Error analysis of the MR system 10 can show that the probability of an error varies from one path of the power line 12 to another, especially when using an asymmetrical power line 12, such as a coaxial cable.

[0056] In addition, Figure 2 In the depicted embodiment, an additional resistor is connected in series with the high-resistance sense wire 30 to further add additional impedance. This increases the difference in measured impedance for different locations of an error in the power supply line 12. The resistance of the high-resistance sense wire 30 is preferably >1 kΩ / m to ensure that the magnetic field passing through the coils of the MR system 10 does not induce excessive current in the high-resistance sense wire 30. To determine the location of the error, the impedance between the high-resistance sense wire 30 and the power supply line 12 can be measured. For example, a voltage can be sensed across the high-resistance sense wire 30 and the power supply line 12 to ensure that the input impedance of the impedance measurement device is sufficiently high. If an error exists in the power supply line 12 assigned to one of the subunits 14, 16, 18, 20, different impedances are measured for different error assignments. Thus, the location of the error in the power supply line 12 can be determined. This eliminates the need for tedious additional testing by replacing one or another subunit 14, 16, 18, 20 of the power supply line 12 to see if the error persists.

[0057] exist Figure 3 In another embodiment depicted in FIG, the MR system 10 includes a signal line 12 for transmitting MR signals from the coil electronics 20 inside the coil. The signal line 12 includes several subunits 14, 16, 18, 20, which in this embodiment are a first signal transmission line 14, a second signal transmission line 16 in the patient table, a third signal transmission line 18, and the coil electronics 20. Also in FIG. Figure 2 In the depicted embodiment, the subunits 14, 16, 18, 20 are interconnected. In the interconnection region 22 of two subunits 14, 16, 18, 20, an additional impedance 24 is coupled to the signal line 12.

[0058] exist Figure 3In the embodiment depicted in FIG, the additional impedance 24 is implemented as an additional resistor and provided as a network of high-resistance sense wires 30. In this embodiment, a network of high-resistance sense wires 30 is coupled to each interconnect region 22 for use in locating errors in signal line 12. The network of high-resistance sense wires 30 is coupled to one path of signal line 12, and an additional resistor is connected to the network of high-resistance sense wires 30 to further add additional impedance. This increases the difference in measured impedance at different locations of an error in the signal line. To determine the location of the error, the impedance between the high-resistance sense wire 30 and the signal line 12 can be measured.

[0059] Although the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments may be understood and implemented by those skilled in the art in practicing the claimed invention by studying the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. Although certain measures are recited in mutually different dependent claims, this does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope. Furthermore, for the sake of clarity, not all elements in the drawings may have been provided with reference signs.

Claims

1. A magnetic resonance system (10), comprising a power line or a signal line (12), wherein: The power supply line or signal line (12) comprises several interconnected subunits (14, 16, 18, 20), and wherein, in a respective interconnection region (22), a respective additional impedance (24) is coupled to the power supply line or signal line (12), wherein the additional impedance (24) provides a defined reference impedance value and is configured to add to the reference impedance value for locating an error in the power supply line or signal line (12).

2. The magnetic resonance system (10) according to claim 1, wherein The subunit (14, 16, 18, 20) comprises a connector (26), and the additional impedance (14) is integrated in the connector (26).

3. A magnetic resonance system (10) according to any preceding claim, wherein: The additional impedance (24) is provided as a capacitor (28), a resistor (30), an inductor and / or a resonant circuit.

4. A magnetic resonance system (10) according to any preceding claim, wherein: In the interconnection region (22), the additional impedance (24) is connected in parallel to the power supply line or signal line (12).

5. The magnetic resonance system (10) according to any one of claims 1 to 3, wherein: In the interconnection region (22), the additional impedance (24) is connected in series to the power supply line or signal line (12).

6. A magnetic resonance system (10) according to any preceding claim, wherein In each interconnect region (22), at least one of the additional impedances (24) is coupled to the power line or signal line (12).

7. A magnetic resonance system (10) according to any preceding claim, wherein: The magnetic resonance system (10) includes a power supply (32) and an impedance measurement device (34) integrated into the power supply (32).

8. The magnetic resonance system (10) according to claim 1, wherein In the interconnection region (22), the additional impedance (24) is provided as a high resistance sense line (30) coupled to the power or signal line (12) or as a network of high resistance sense lines (30) coupled to the power or signal line (12).

9. A method for locating an error in a power supply line or a signal line (12) of a magnetic resonance system (10), wherein: The power supply line or signal line (12) comprises a number of interconnected subunits (14, 16, 18, 20), and wherein, in a corresponding interconnection area (22), a resistive additional impedance (24) is coupled to the power supply line or signal line (12), and wherein the additional impedance (24) provides a reference impedance value, the method comprising the following steps: a) measure impedance, and b) determining the location of the error by comparing the measured impedance with the reference impedance value.

10. The method according to claim 9, wherein: The method further comprises the step of coupling the additional impedance (24) to the power or signal line (12) in the interconnect region (22).

11. The method according to claim 9 or 10, wherein: The step of measuring impedance includes measuring the impedance of the power line or signal line (12).

12. The method according to claim 9 or 10, wherein: The step of measuring impedance includes measuring the impedance between a high resistance sensing line (30) and the power line or signal line (12).

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