Indicator of the load condition of the flexible coil element

Abstract

The present invention relates to a flexible coil element for a flexible coil array for a magnetic resonance imaging device. The present invention relates to a flexible coil array for a magnetic resonance imaging device for indicating a load state of a flexible coil element arranged on at least one inductive element. The present invention relates to a method for indicating a load state of a flexible coil element arranged on at least one inductive element, wherein the flexible coil element is constituted by a flexible coil array, the flexible coil array including at least one flexible coil element. The present invention also relates to a software package including instructions for performing the method steps.

Description

[Technical field]

[0001] The present invention relates to a magnetic resonance imaging apparatus. flexibility For coil array flexibility Regarding the coil element.

[0002] The present invention also provides a method for detecting a temperature difference between the at least one inductive element and the at least one inductive element. flexibility Title: Magnetic resonance imaging apparatus for indicating a load state of a coil element flexibility Regarding the coil array.

[0003] The present invention is provided with a method for detecting a temperature difference between a semiconductor device and an inductive element. flexibility A method for indicating the load condition of a coil element. flexibility The coil element is flexibility It is composed of a coil array, flexibility The coil array has at least one flexibility Includes a coil element.

[0004] Furthermore, the invention relates to a software package containing instructions according to the method steps. [Background technology]

[0005] US Patent Application Publication No. 2010 / 060284 refers to a method of moving a table on which a subject rests so that the centre of a section, selected by a control unit of a computer system receiving a selection operation via a button, is located at the centre of a magnetic field.

[0006] JP2005 / 124855A discloses a light-emitting element mounted on the upper surface of a light-receiving coil, and when the light-receiving element is mounted on the opening of a gantry, and the upper plate on which the subject is mounted and the light-receiving coil are inserted into the center of a static magnetic field, the light-receiving element detects an optical signal from the light-emitting element to obtain the position of the upper plate, and the upper plate is moved by a predetermined distance determined by the shape of the gantry, and the subject and the light-receiving coil are inserted into the center of the static magnetic field.US2008 / 007263A discloses a magnetic resonance imaging apparatus including an array coil in which multiple element coils are arranged to receive magnetic resonance signals from the subject, a calculation unit that calculates projection data of element coils related to the arrangement direction of the multiple element coils based on multiple magnetic resonance signals received by the multiple element coils, and a determination unit that determines the position of the multiple element coils or the position of the array coil based on the projection data of the multiple element coils.

[0007] US Patent Application Publication No. 2015 / 253404 refers to a magnetic resonance imaging apparatus including a wireless communication unit, a radio frequency (RF) coil, and a specific unit.

[0008] US 2017 / 020409 A1 refers to a medical imaging device designed to acquire medical image data of a patient during a medical imaging examination, the medical data acquisition scanner having a patient receiving area at least partially surrounded by the scanner, within which a body area of ​​the patient is located during the medical imaging examination.

[0009] US Patent Application US2018 / 0217213 discloses an indicator array on a local coil assembly designed to display a signal indicative of activity of each of two or more coils. Summary of the Invention [Problem to be solved by the invention]

[0010] Based on this, it is an object of the present invention to provide an improved means for a magnetic resonance imaging apparatus. In particular, the object of the present invention is to flexibility The aim is to provide a more intuitive and simple aid for accurate placement of the coil array. [Means for solving the problem]

[0011] This problem is solved by the subject matter of claim 1. Preferred further embodiments are found in the dependent claims. According to the invention, a magnetic resonance imaging device for flexibility For coil array flexibility A coil element is provided. flexibility The coil element is disposed on the at least one inductive element and configured to generate a magnetic frequency signal. flexibility a measuring means configured to measure a magnetic frequency signal received by the coil element; flexibility and signal means configured to emit a human perceptible signal to indicate a load condition of the coil elements, the characteristics of the human perceptible signal being generated in dependence on the characteristics of the measured magnetic frequency signal.

[0012] In other words, a coil element is meant to be a single loop that functions, for example, as an antenna and / or a receiver.

[0013] According to the invention, when placed on at least one inductive element flexibility A magnetic resonance imaging apparatus for indicating the load state of a coil element flexibility A coil array is also provided. flexibility The coil array includes at least one coil arranged to be disposed over the at least one inductive element. flexibility a coil element, a frequency generating means configured to generate a magnetic frequency signal, and a measuring means configured to measure the magnetic frequency signal received by the at least one coil element; flexibility Coil array flexibilityand signal means arranged for emitting a human perceptible signal for each of the coil elements, the characteristics of the human perceptible signal being generated in response to characteristics of the magnetic frequency signal being measured.

[0014] In other words, a coil array is a collection of several coil elements, which must be positioned above the object to be imaged.

[0015] In addition, flexibility The coil array may be any of the preferred embodiments. flexibility The coil elements may have any of the following characteristics:

[0016] According to the invention, it is arranged on at least one inductive element flexibility A method for indicating a load condition of a coil element is also provided, flexibility The coil element is flexibility It is composed of a coil array, flexibility The coil array has at least one flexibility The method includes the steps of generating a magnetic frequency signal by a frequency generating means, measuring the magnetic frequency signal received by the at least one coil element by a measuring means, and measuring the magnetic frequency signal received by the at least one coil element by a signal means. flexibility Coil array flexibility and transmitting, for each of the coil elements, a human perceptible signal, the characteristics of the human perceptible signal being generated depending on the characteristics of the magnetic frequency signal being measured.

[0017] Human-perceivable signals are flexibility It is fired independently to each of the coil elements.

[0018] Furthermore, the method may be any of the preferred embodiments. flexibility Coil element or flexibility The method steps may include those depending on the characteristics of the coil array.

[0019] According to the invention there is also provided a software package comprising instructions for carrying out the method steps on a computing system according to the invention. The software package may for example be provided as an update.

[0020] Furthermore, the software package may be implemented according to any of the preferred embodiments. flexibility Coil element or flexibility It may include instructions according to the method steps according to the characteristics of the coil array.

[0021] flexibility Coil element / flexibility The coil array may be constituted by a magnetic resonance imaging device.

[0022] The basic idea of ​​the present invention is to flexibility When positioning the coil elements, the user is immediately informed whether the positioning is correct relative to the inductive element. Correct positioning can be indicated to the user by acoustic or optical signals. The correct positioning of the flexible structure is considerably simplified, flexibility Efficient operation of the coil elements is advantageously enabled. flexibility When using a coil array to image small objects such as a foot, it may be intended that not all coil elements will be loaded and contribute to the imaging. The signal is meant to leave it up to the user to react, such as an optical signal means in the form of an LED indicator. Advantageously, this overcomes any automatic means that would attempt to adapt the tuning of the array in an unintended way.

[0023] According to a preferred embodiment, the frequency signal is a pilot signal or a noise signal. The pilot signal may be a frequency swept signal. The noise signal may be within a selected bandwidth. The magnetic frequency signal may be provided by an external device such as a patient table, or flexibility It may be provided by a coil element. flexibilityThe coil element may comprise an energy storage means. The magnetic frequency signal may be in the Larmor frequency range and the frequency may deviate from the Larmor frequency by within 100 kilohertz or more. Thus, flexibility Coil element / flexibility The coil array system and method can be flexibly adapted to specific application situations.

[0024] According to a preferred embodiment, the signaling means configured to emit a human perceptible signal is an Augmented Reality (AR) system or a beamer, or a Light Emitting Diode (LED), the light signal characteristics of the LED being on the inductive charging element. flexibility It depends on the positioning of the coil elements. Augmented reality is a computer-aided extension of the perception of reality. This information can address all human sensory modalities. AR systems may be used to overlay color indicators such as LEDs, or may be used in combination with other signaling means, for example, to provide more sophisticated feedback. The human-perceivable signal can be adapted to the particular application. For example, a visual signal may be more appropriate in a room with a lot of background noise, and conversely, an acoustic signal may be more appropriate in a room with a lot of light.

[0025] According to a preferred embodiment, the signalling means comprises: flexibility The coil element is in the center of the inductive element, or flexibility The coil elements are bent or deformed, or one or more flexibility Depending on how the coil elements are positioned on top of each other, they are configured to emit different types of human-perceivable signals. flexibility A signal type can be selected to account for specific scenarios that significantly impair measurements using the coil array, and the signal type is specifically assigned to the case. flexibility Depending on the requirements regarding the accuracy of the coil array measurements, flexibilityThe coil array can provide more or less of a signal for unfavorable configurations. In this way, the user can consciously eliminate sources of error. Thus, user friendliness is increased and at the same time the reliability of the measurements is guaranteed.

[0026] According to a preferred embodiment, the human perceptible signal comprises: flexibility for repositioning or relocating coil elements; or flexibility A user command to maintain the position or alignment of the coil elements. The user command may be, for example, a request to move the entire array relative to a region of interest (ROI) in combination with a vital eye camera system. The beam may be used to project a color indicator onto the coil elements, or provide more sophisticated feedback. Thus, the user can directly instruct how to improve the position. This allows: flexibility The time required to accurately position the coil elements / arrays is reduced.

[0027] According to a preferred embodiment, the frequency generating means comprises at least one flexibility The coil element and / or at least one inductive element are provided. The advantage of this is that flexibility In the case where the magnetic frequency generating means is a coil element, this can be particularly compact. In the other case, i.e. where the magnetic frequency generating means is an inductive element, the inductive element can be specifically designed to generate the pilot signal.

[0028] According to a preferred embodiment, the method further comprises, after the step of generating a frequency signal by the frequency generating means, converting the frequency signal into flexibility The method includes sampling the frequency signal within the bandwidth range by the coil element. For example, a coil array can sample the signal within the available bandwidth. Furthermore, time averaging and debouncing can be applied. When the signal means is supplied with the energy of the frequency generating means, the blinking of the signal of the signal means, for example an LED, can be avoided.

[0029] According to a preferred embodiment, the method includes, after the step of measuring the magnetic frequency signal by the measuring means, a step of comparing, by the control means, the curve shape of the frequency signal with at least one stored pattern, and a human perceptible signal characteristic is selected based on one of the at least one stored pattern that has the most similarity to the curve shape of the frequency signal. Such a step may include that the sampled signal is evaluated. In the case of LEDs, depending on the most matching pattern, an LED color is selected. This allows the user to react according to the signal. For example, in the case of a multi-purpose array, an imperfect loading condition of the coil may be intended.

[0030] According to a preferred embodiment, the method comprises the steps of: flexibility Coil array flexibility emitting a light signal to each of the coil elements, the light signal characteristic being indicative of at least one of the coil elements on the at least one inductive charging element. flexibility The LEDs may be located inside the translucent housing containing the coil array or may point directly to the outside. This provides feedback to the user during coil array placement. For example, the LEDs may be illuminated green if (all) the coil elements are coupled to tissue. In such case, the coil load is within the intended range. Alternatively, (a) the LED(s) assigned to a coil may be illuminated red if the respective coil to which it is assigned is not intentionally placed in tissue. The tissue may be human tissue, such as breast.

[0031] The present invention will now be described in more detail based on preferred design examples with reference to the drawings. [Brief description of the drawings]

[0032] [Figure 1] 2 shows a flow chart of a method according to an embodiment. [Figure 2A] 2 illustrates a schematic diagram of a flexible coil element according to an embodiment in a normal state. [Figure 2B] 2A and 2B show schematic diagrams of a flexible coil element according to an embodiment in a deformed state. [Figure 2C] 1 shows a schematic diagram of two flexible coil elements according to an embodiment in a stacked state. [Diagram 3] 2 illustrates a schematic representation of a flexible coil element according to an embodiment in a folded state. [Figure 4A] 1A and 1B illustrate schematic diagrams of a flexible coil array according to a tissue-focused embodiment; [Figure 4B] 13A and 13B are schematic diagrams illustrating a flexible coil array according to an embodiment being displaced in accordance with tissue. [Figure 4C] 1 shows a schematic diagram of a flexible coil array according to an embodiment, with one flexible coil element folded; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] 1 shows a flow chart of a method according to an embodiment. The method includes steps 100, 150, 200, 250, and 300. Alternatively, the method includes steps 100, 150, 200, 250, and 300A. Furthermore, the method includes steps 400 and 500, which are included in both alternatives.

[0034] First, the coil elements can be enabled. For example, they can be enabled by connecting a plug to the coil array 2.

[0035] According to the step indicated by the reference number "100", the method comprises the generation of a magnetic frequency signal by a frequency generating means. In particular, a frequency sweep signal is generated from inside the patient table. The magnetic frequency signal comprises frequencies in the range of the Larmor frequency or frequencies deviating from the Larmor frequency in the kilohertz range. The frequency signal is similar to the tuning signal of the body coil. Alternatively, the signal can be generated by the coil itself, which allows to perform these measurements without connecting the coil to the system, i.e. in the preparation room. For this purpose, the coil is equipped with a battery to perform this measurement autonomously.

[0036] According to the step indicated by reference numeral "150", the method comprises: flexibility This involves sampling the frequency signals within the bandwidth range by the coil elements. In other words, the coil array 2 samples signals within the available bandwidth. Furthermore, time averaging and debouncing are applied to avoid flickering of the signal means.

[0037] According to the step indicated by reference numeral "200", the method includes measuring, by a measuring means, a magnetic frequency signal received by at least one coil element.

[0038] According to the step indicated by the reference numeral "250", the method includes comparing, by the control means, the curve shape of the frequency signal with at least one stored pattern. More specifically, the curve shape of the sampled signal is evaluated and matched against known patterns.

[0039] According to the step indicated by reference numeral "300", the method comprises: flexibility Coil array flexibility For each coil element, a human perceptible signal is emitted by a signal means.

[0040] Instead, following the steps designated by reference numeral "300A," the method includes: flexibility Each coil array flexibility It consists of sending a light signal to the coil elements. In the case of LEDs, the LED color is selected depending on the best matching pattern. The user can then react accordingly. In the case of multi-purpose arrays, imperfect load conditions can be contemplated.

[0041] According to the step indicated by reference number "400", the method includes triggering, by the control means, the start of a scan measurement.

[0042] According to the step indicated by the reference numeral "500", the method includes: controlling the signaling means / LED and flexibility and turning off the load measurements of the coil elements. In other words, when a scan is intended to begin as indicated by, for example, moving the patient table or a user input, the method includes sweeping the signal and therewith turning off the measurement LED light.

[0043] A digital preamplifier with radio frequency (RF) in / out and corresponding local control logic allows measurements and LED illumination to be performed locally without the need to connect to a scanner front end.

[0044] Under certain circumstances, it is possible to derive the loading conditions from the sampling noise in a given bandwidth, instead of requiring a pilot signal.

[0045] FIG. 2(a) shows an embodiment in a normal state. flexibility 2(b) shows a schematic representation of the coil element 1 according to an embodiment in a deformed state that may result when the coil array is squeezed. flexibility Shown diagrammatically is the coil element 1. The rectangular element is the preamplifier 4. flexibility The coil element 1 is circular in the normal state. In the deformed state, flexibility The coil element 1 is bent. FIG. 2C shows two flexibilityThe coil elements 1 are shown diagrammatically in an overlapping configuration, as may occur when the flexible array is wrapped around an arm or leg.

[0046] FIG. 3 shows an embodiment in a folded state. flexibility The coil elements are shown diagrammatically. In this particular case, flexibility The coil elements are folded to form a semicircle.

[0047] FIG. 4A is an embodiment focusing on tissue 5. flexibility Shown diagrammatically is a coil array 2. The tissue 5 may be human tissue, such as the breast. flexibility The coil array 2 is equipped with light emitting diodes (LEDs) as signaling means. All LEDs are illuminated with the same color, such as green (not shown). Thereby, all flexibility The coil element 1 is coupled to the tissue 5, flexibility This indicates to the user that the coil load of each of the coil elements 1 is within the intended range. The array includes a color LED for each coil element 1 to indicate its status (in the RF direction).

[0048] FIG. 4B is an example of flexibility The coil array 2 is shown displaced in response to tissue 5. The LEDs are green (not shown) and red ( flexibility The load is determined to be within its intended range. flexibility In the area of ​​the coil array 2, the LED lights up green (not shown). flexibility The coil load of the left row of coil element 1 is determined to be too low. In such a case, the LED (beam in FIG. 4B) lights up red, if applicable, to request replacement. For example, a large flexibility When the coil array is used to image small objects such as the foot, it may be intended that not all coil elements are loaded and contribute to the imaging. The LED indicator informs the user of the response. For example, the user may center the coil array 2 relative to the tissue 5 or use a strap to wrap around the body located below the tissue 5. flexibility The coil element 1 can be wound.

[0049] Figure 4C shows one flexibility Coil element 1 folded, according to the embodiment flexibility The coil array 2 is shown diagrammatically. In other words: flexibility The coil array 2 folds back on itself. The LEDs light up in different colors, such as green (not shown) and blue (indicated by the beam in the coil element in the upper left corner of the array). It is determined that the load is within the intended range. flexibility In the area of ​​the coil array 2, the LED is illuminated in green (not shown). Furthermore, a blue light (indicated by a beam) in the area of ​​the folded coil element 1 illuminates the flexibility Coil element 1 is indicated to be folded, if possible, and the user is flexibility This requires that the coil array 2 be flattened. Hereinafter, embodiments of the present invention will be described. (Appendix 1) 1. A flexible coil element for a flexible coil array for a magnetic resonance imaging apparatus, the flexible coil element being configured to be positioned over at least one inductive element, measuring means configured to measure a magnetic frequency signal received by said coil element; A flexible coil element comprising: signal means for indicating a load status of the flexible coil element, the signal means configured to emit a human perceptible signal, the characteristics of the human perceptible signal being generated in dependence on characteristics of the measured magnetic frequency signal. (Appendix 2) 2. The flexible coil element of claim 1, wherein the frequency signal is a pilot signal or a noise signal. (Appendix 3) The signal means configured to emit the human perceptible signal comprises: Augmented reality, AR, system, or beamer, or Light Emitting Diode, LED 3. The flexible coil element of claim 1 or 2, wherein the characteristics of the LED light signal depend on the positioning of the flexible coil element on the inductive charging element. (Appendix 4) 4. The flexible coil element of any one of claims 1 to 3, wherein the signal means is configured to emit a type of human-perceivable signal depending on whether the flexible coil element is at the center of the inductive element or whether the flexible coil element is bent or deformed. (Appendix 5) 5. The flexible coil element of any one of claims 1 to 4, wherein the human-perceptible signal is a user command to reposition or reconfigure the flexible coil element or to maintain a position or configuration of the flexible coil element. (Appendix 6) 6. A flexible coil array for a magnetic resonance imaging apparatus for indicating a load state of flexible coil elements when positioned over at least one inductive element, the flexible coil array comprising several flexible coil elements according to any one of claims 1 to 5. (Appendix 7) 7. The flexible coil array of claim 6, further comprising a frequency generating means for generating the magnetic frequency signal. (Appendix 8) 7. The flexible coil array of claim 6, wherein the frequency generating means comprises the at least one flexible coil element and / or the at least one inductive element. (Appendix 9) 9. The flexible coil array of any one of claims 6 to 8, wherein the signal means is configured to emit a type of the human perceptible signal depending on whether one or more flexible coil elements are configured on top of each other. (Appendix 10) 2. The flexible coil element of claim 1, further comprising a frequency generating means for generating the magnetic frequency signal. (Appendix 11) 1. A method for indicating a load condition of a flexible coil element positioned on at least one inductive element, the flexible coil element being configured by a flexible coil array, the flexible coil array having at least one flexible coil element, the method comprising: generating a magnetic frequency signal by a frequency generating means; measuring said magnetic frequency signal received by at least one coil element by a measuring means; transmitting a human perceptible signal by signal means to each of said flexible coil elements for indicating a load condition of said flexible coil element, the characteristics of said human perceptible signal being generated in dependence on the characteristics of said measured magnetic frequency signal; or The method comprises the steps of any of the features according to any of claims 1 to 10, method. (Appendix 12) 12. The method of any one of claims 1 to 11, further comprising, after the step of generating a frequency signal by the frequency generating means, sampling the frequency signal within a bandwidth range by the flexible coil element. (Appendix 13) 13. The method of claim 11 or 12, further comprising, after the step of measuring the magnetic frequency signal by a measurement means, a step of comparing by a control means a curve shape of the frequency signal with at least one stored pattern, wherein the characteristic of the human perceptible signal is selected based on one of the at least one stored pattern that is most similar to the curve shape of the frequency signal. (Appendix 14) the method comprising the step of transmitting, by the LED, a light signal to each of the flexible coil elements of the flexible coil array, the characteristic of the light signal being generated in dependence on a positioning of the at least one flexible coil element over the at least one inductive charging element. Any of the methods set forth in appendix 11 to 13. (Appendix 15) A software package having instructions for carrying out the method steps of any one of claims 1 to 14 on a computing system. [Explanation of symbols]

[0050] 1 flexibility Coil element 2 flexibility Coil Array 3 Signal means 4. Preamplifier 5 Organization 100 A magnetic frequency signal is generated by a frequency generating means. 150 flexibility The coil elements sample the frequency signals within the bandwidth range. 200 A measuring means measures the magnetic frequency signal received by at least one coil element. 250 The control means compares the shape of the curve of the frequency signal with at least one stored pattern. 300 By signal means, flexibility Coil array flexibilityEach coil element emits a signal that can be sensed by humans. With 300A LED, flexibility Coil array flexibility An optical signal is sent to each coil element 400 Triggers the start of a scan measurement by the control means 500 By the control means, the signal means / LED and flexibility Turn off the load measurement of the coil element

Claims

1. 1. A flexible coil element for a flexible coil array for a magnetic resonance imaging apparatus, comprising: the flexible coil element is configured to be positioned over at least one inductive element and configured to measure a magnetic frequency signal received by the flexible coil element, the received and measured magnetic frequency signal being a magnetic frequency signal generated by a frequency generating means; The flexible coil element includes: a signal emitter positioned on the inductive element for indicating a load condition of the flexible coil element, the signal emitter configured to emit a human perceptible signal, the characteristics of the emitted human perceptible signal being generated in dependence on characteristics of the magnetic frequency signal measured at the flexible coil element; A flexible coil element having a

2. The flexible coil element of claim 1 , wherein the magnetic frequency signal is a pilot signal or a noise signal.

3. The signal emitter configured to emit the human perceptible signal comprises: Augmented reality, AR, system, or beamer, or Light Emitting Diode, LED 3. The flexible coil element of claim 1 or 2, wherein the characteristics of the LED light signal depend on the positioning of the flexible coil element on an inductive charging element.

4. 4. The flexible coil element of claim 1, wherein the signal emitter is configured to emit a type of human-perceivable signal depending on whether the flexible coil element is at the center of the inductive element or whether the flexible coil element is bent or deformed.

5. 5. The flexible coil element of claim 1 , wherein the human perceptible signal is a user command to reposition or reconfigure the flexible coil element, or to maintain a position or configuration of the flexible coil element.

6. A flexible coil element according to any one of the preceding claims, comprising frequency generating means for generating said magnetic frequency signal.

7. 7. The flexible coil element of claim 6, wherein the frequency generating means comprises the at least one flexible coil element and / or the at least one inductive element.

8. A flexible coil array for a magnetic resonance imaging device for indicating a load state of a flexible coil element when positioned on at least one inductive element, the flexible coil array comprising several flexible coil elements according to any one of claims 1 to 7.

9. 10. The flexible coil array of claim 8, wherein the signal emitter is configured to emit a type of the human perceptible signal depending on whether one or more flexible coil elements are configured on top of one another.

10. A magnetic resonance imaging apparatus comprising a flexible coil array according to claim 8 or 9.

11. 1. A method for indicating a load condition of a flexible coil element positioned on at least one inductive element, the flexible coil element being configured by a flexible coil array, the flexible coil array having at least one flexible coil element, the method comprising: a frequency generating means generating a magnetic frequency signal; measuring the magnetic frequency signal received by the at least one flexible coil element; for each of the flexible coil elements positioned on the inductive element, indicating a load condition of the flexible coil element, the indicating including transmitting a human perceptible signal, a characteristic of the transmitted human perceptible signal being generated in dependence on a characteristic of the measured magnetic frequency signal; The method comprising:

12. 12. The method according to any one of claims 1 to 11, comprising after the step of generating the frequency signal, sampling the magnetic frequency signal within a bandwidth range by means of the flexible coil element.

13. 13. The method of claim 11 or 12, further comprising, after the step of measuring the magnetic frequency signal, a step of comparing a curve shape of the frequency signal with at least one stored pattern, and wherein the characteristic of the human perceptible signal is selected based on one of the at least one stored pattern that is most similar to the curve shape of the magnetic frequency signal.

14. the method comprising the step of transmitting, by an LED, an optical signal to each of the flexible coil elements of the flexible coil array, the optical signal characteristic being generated in dependence on a positioning of the at least one flexible coil element on the at least one inductive element; 14. The method of any one of claims 11 to 13.

15. A software package comprising instructions for controlling a computing system to carry out the method of any one of claims 11 to 14.

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