阅读说明：本技术 对接收线圈位置的自动化检测 (Automated detection of docking take-up ring position ) 是由 P·韦尔尼科尔 C·G·洛斯勒 O·利普斯 I·施马勒 C·芬德科里 于 2020-01-10 设计创作，主要内容包括：本发明提供了一种磁共振成像系统(100、300)。所述磁共振成像系统包括：对象支撑物(120),其被配置用于在装载位置(121)与成像位置(200)之间移动对象；接收磁共振成像线圈(114),其被配置用于被放置在所述对象上；以及光检测系统(115),其包括至少一个环境光传感器,所述至少一个环境光传感器用于测量光数据(144)。所述光检测系统进行以下各项中的任一项：被安装到所述主磁体,使得所述光数据是从所述成像区测量的；以及被安装到所述接收磁共振成像线圈。处理器(130)对机器可执行指令(140)的执行使所述处理器：将所述对象支撑物从所述装载位置移动(500)到所述成像位置；当所述对象支撑物在所述成像位置中时,使用所述至少一个环境光传感器来采集(502)所述光数据；使用所述光数据来确定(504)所述接收磁共振成像线圈是否被定位用于采集磁共振成像数据；并且如果所述接收磁共振成像线圈被定位用于采集所述磁共振成像数据,则提供(506)信号(146)。(The invention provides a magnetic resonance imaging system (100, 300). The magnetic resonance imaging system comprises: a subject support (120) configured for moving a subject between a loading position (121) and an imaging position (200); a receive magnetic resonance imaging coil (114) configured for placement on the subject; and a light detection system (115) comprising at least one ambient light sensor for measuring light data (144). The light detection system performs any one of: is mounted to the main magnet such that the light data is measured from the imaging region; and mounted to the receive magnetic resonance imaging coil. Execution of machine-executable instructions (140) by a processor (130) causes the processor to: moving (500) the subject support from the loading position to the imaging position; acquiring (502) the light data using the at least one ambient light sensor while the subject support is in the imaging position; determining (504) whether the receiving magnetic resonance imaging coil is positioned for acquiring magnetic resonance imaging data using the light data; and providing (506) a signal (146) if the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data.)

1. A magnetic resonance imaging system (100, 300) configured for acquiring magnetic resonance imaging data (242) from an imaging zone (108), wherein the magnetic resonance imaging system comprises:

a main magnet (104) configured for generating a B0 magnetic field within the imaging zone;

a subject support (120) configured for moving a subject between a loading position (121) and an imaging position (200);

a receive magnetic resonance imaging coil (114) configured for placement on the subject;

a light detection system (115) comprising at least one ambient light sensor for measuring spatially encoded light data (144) from ambient lighting, wherein the light detection system does any of: is mounted to the main magnet such that the light data is measured from the imaging region; and mounted to the receive magnetic resonance imaging coil;

a memory (134) storing machine executable instructions (140);

a processor (130) for controlling the magnetic resonance imaging system, wherein execution of the machine executable instructions causes the processor to:

controlling (500) movement of the subject support from the loading position to the imaging position;

acquiring (502) the light data using the at least one ambient light sensor while the subject support is in the imaging position;

determining (504) using the light data whether the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data; and is

Providing (506) a signal (146) if the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data.

2. The magnetic resonance imaging system of claim 1, wherein the magnetic resonance imaging system further comprises a multi-channel radio frequency system configured for acquiring the magnetic resonance imaging data, wherein the radio frequency system comprises a body coil (800) and the receive magnetic resonance imaging coil, wherein the receive magnetic resonance imaging coil comprises a plurality of receive elements, wherein the memory further contains calibration commands configured for controlling the magnetic resonance imaging system to perform a calibration of the plurality of receive elements of the receive magnetic resonance imaging coil using the body coil, wherein execution of the machine executable instructions further causes the processor to:

calibrating a plurality of channels of the receive magnetic resonance imaging coil by executing the calibration commands; and is

Providing a hardware fault signal if the calibration fails, wherein the signal indicates that the receiving magnetic resonance imaging coil is properly positioned.

3. The magnetic resonance imaging system of claim 1 or 2, wherein the light detection system is mounted to the receiving magnetic resonance imaging coil.

4. The magnetic resonance imaging system of claim 3, wherein the magnetic resonance imaging system comprises an examination room (102) for housing the main magnet, wherein the examination room comprises a room illumination system (103), wherein the main magnet comprises a magnet illumination system (107) for illuminating the imaging zone, wherein the room illumination system is configured for generating a first type of light (160), wherein the magnet illumination system is configured for generating a second type of light (162), wherein execution of the machine executable instructions causes the processor to determine whether the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data by differentiating between the first type of light and the second type of light.

5. The magnetic resonance imaging system of claim 4, wherein the first type of light differs from the second type of light by any one of: color, intensity, oscillation frequency, intensity of color component, modulation of the light, and combinations thereof.

6. The magnetic resonance imaging system of any one of claims 4 or 5, wherein the magnet illumination system is configured for producing light with a spatially dependent frequency, a spatially dependent color coding and/or a spatially dependent modulation.

7. The magnetic resonance imaging system of claim 6, wherein execution of the machine executable instructions further causes the processor to determine a spatial position and/or orientation of the receiving magnetic resonance imaging coil using the spatially dependent frequency, the spatially dependent color coding, and/or the spatially dependent modulation produced by the magnet illumination system.

8. The magnetic resonance imaging system of any one of claims 3 to 7, wherein the light detection system comprises a plurality of ambient light sensors configured for measuring ambient light distributed over a surface of the receiving magnetic resonance imaging coil.

9. The magnetic resonance imaging system of any one of the preceding claims, wherein the receiving magnetic resonance imaging coil comprises a preamplifier (902), wherein the at least one ambient light sensor is attached to the preamplifier, wherein the receiving magnetic resonance imaging coil comprises an optical fiber (1000) for each of the at least one ambient light sensors, wherein each optical fiber is configured for channeling light from the surface of the receiving magnetic resonance imaging coil to one of the at least one ambient light sensors.

10. The magnetic resonance imaging system of any one of the preceding claims, wherein the light detection system is mounted to the main magnet, and wherein the receiving magnetic resonance imaging coil comprises at least one light generating element (302).

11. The magnetic resonance imaging system of any one of the preceding claims, wherein execution of the machine executable instructions causes the processor to determine whether the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data by inputting the light data into a decision module (148) programmed to compare the light data to a set of predetermined criteria.

12. The magnetic resonance imaging system of any one of claims 1 to 10, wherein execution of the machine executable instructions causes the processor to determine whether the receiving magnetic resonance imaging coil is positioned for acquisition of the magnetic resonance imaging data by inputting the light data to a trained machine learning module (150).

13. The magnetic resonance imaging system of any one of the preceding claims, wherein the magnetic resonance imaging system further comprises an optical data transmission system, wherein the optical data transmission system is configured for forming a bidirectional data link between the receiving magnetic resonance imaging coil and the processor, wherein the optical data transmission system comprises the light detection system.

14. A computer program product comprising machine executable instructions (140) for execution by a processor (130) controlling a magnetic resonance imaging system (100, 300), wherein the magnetic resonance imaging system is configured for acquiring magnetic resonance imaging data (242) from an imaging zone (108), wherein the magnetic resonance imaging system comprises a main magnet (104) configured for generating a B0 magnetic field within the imaging zone; wherein the magnetic resonance imaging system further comprises a subject support (120) configured for moving a subject between a loading position (121) and an imaging position (200); wherein the magnetic resonance imaging system further comprises a receiving magnetic resonance imaging coil (114) configured for being placed on the subject, wherein the magnetic resonance imaging system further comprises a light detection system comprising at least one ambient light sensor (115) for measuring spatially encoded light data (144) from ambient illumination, wherein the light detection system does any one of: is mounted to the main magnet such that the light data is measured from the imaging region; and mounted to the receive magnetic resonance imaging coil; wherein execution of the machine-executable instructions causes the processor to:

controlling (500) movement of the subject support from the loading position to the imaging position;

acquiring (502) the light data using the at least one ambient light sensor while the subject support is in the imaging position;

determining (504) using the light data whether the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data; and is

Providing (506) a signal (146) if the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data.

15. A method of operating a magnetic resonance imaging system (100, 300), wherein the magnetic resonance imaging system is configured for acquiring magnetic resonance imaging data (242) from an imaging zone, wherein the magnetic resonance imaging system comprises a main magnet (104) configured for generating a B0 magnetic field within the imaging zone; wherein the magnetic resonance imaging system further comprises a subject support (120) configured for moving a subject between a loading position (121) and an imaging position (200); wherein the magnetic resonance imaging system further comprises a receiving magnetic resonance imaging coil (114) configured for being placed on the subject, wherein the magnetic resonance imaging system further comprises a light detection system comprising at least one ambient light sensor (115) for measuring spatially encoded light data (144) from ambient illumination, wherein the light detection system does any one of: is mounted to the main magnet such that the light data is measured from the imaging region; and mounted to the receive magnetic resonance imaging coil, wherein the method comprises:

moving (500) the subject support from the loading position to the imaging position;

acquiring (502) the light data using the at least one ambient light sensor while the subject support is in the imaging position;

determining (504) using the light data whether the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data; and is

Providing (506) a signal (146) if the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data.

Technical Field

The present invention relates to magnetic resonance imaging.

Background

Magnetic Resonance Imaging (MRI) scanners use large static magnetic fields to align the nuclear spins of atoms as part of a procedure to generate images within a subject. This large static magnetic field is called the B0 field or main magnetic field. Various quantities or properties of an object can be measured spatially using MRI. The acquisition of magnetic resonance data can be controlled by using pulse sequences to implement various imaging protocols.

Chinese patent publication CN 103654778B discloses a positioning system and a magnetic resonance imaging control method, the magnetic resonance system comprising a resonance main machine and a movable deck local coil, the main deck being moved into a magnetic resonance volume, a magnetic resonance main machine receiving unit being provided with an optical signal, an optical signal emitting device being mounted on the deck or the local coil. The patent also discloses an imaging control method that automatically positions the center of the patient's MRI region using an optical signal receiving device and an optical signal transmitting unit in a step mode for a fast positioning mode, thereby simplifying positioning, imaging operations and improving positioning accuracy, saving examination costs, and better meeting actual imaging requirements.

US patent application US 2013/0119981 discloses a magnetic resonance imaging apparatus with a wireless RF coil and a sensor unit. The sensor unit may be an optical sensor which detects an optical signal from a laser emitting unit inside a gantry of the MRI system.

Disclosure of Invention

The invention provides a magnetic resonance imaging system, a method and a computer program product in the independent claims.

Configuring a magnetic resonance imaging system according to the use may be complicated. Failures during an imaging protocol or calibration protocol may be due to hardware failures and/or incorrect configuration for imaging of the subject. Receive magnetic resonance imaging coils (e.g., surface coils) can generally be used with the subject. If the receiving magnetic resonance imaging coil is placed incorrectly, the magnetic resonance imaging protocol may fail. Embodiments may provide a means to detect whether the receiving magnetic resonance imaging coil is properly placed on the subject by detecting changes in ambient light. If the ambient light sensor is placed directly on the receiving magnetic resonance imaging coil, a change in detected light between the loading position and the imaging position of the subject can be detected. Also, placing the ambient light sensor in the bore of the magnetic resonance imaging coil (e.g. in or near the imaging zone) may also allow detecting the correct position of the receiving magnetic resonance imaging coil. The present invention relates to a magnetic resonance imaging system having a light detection system to determine the position of a magnetic resonance imaging coil (local Radio Frequency (RF) antenna). According to the invention, the light detection system operates based on ambient lighting. The ambient illumination is spatially encoded in that at least the ambient illumination has a physical aspect that differs between the loading position and the imaging position of the subject support.

The invention enables to detect whether the position of the magnetic resonance imaging coil is in the imaging position or in the loading position without the need of providing separate optical hardware in the examination zone of the magnetic resonance imaging system.

In one aspect, the invention provides a magnetic resonance imaging system configured for acquiring magnetic resonance imaging data from an imaging zone. The magnetic resonance imaging system comprises a main magnet configured for generating a B0 magnetic field or main magnetic field within the imaging zone. The magnetic resonance imaging system further comprises a subject support configured for moving the subject between the loading position and the imaging position. When the object is in the loading position, the object is not within the imaging zone. When the object is in the imaging position, the object is at least partially within the imaging zone. The magnetic resonance imaging system further comprises a receive magnetic resonance imaging coil configured for being placed on the subject. This type of receive magnetic resonance imaging coil is commonly referred to as a surface coil. In some examples, the receive magnetic resonance imaging coil may also be flexible.

The magnetic resonance imaging system further comprises a light detection system comprising at least one ambient light sensor for measuring light data. An ambient light sensor, as used herein, is a sensor configured to detect light and collect light from an area surrounding the sensor. The light detection system performs any one of: a) is mounted to the main magnet such that the light data is measured from the imaging region; and b) mounted to the receive magnetic resonance imaging coil. Being mounted to the main magnet may include being mounted to any one of the following: a component attached to the main magnet, or a component for forming the main magnet. For example, a housing mounted to the main magnet may include body coils or other components.

The magnetic resonance imaging system further comprises a memory storing machine executable instructions. The magnetic resonance imaging system further comprises a processor for controlling the magnetic resonance imaging system. Execution of the machine-executable instructions causes the processor to move the subject support from the loading position to the imaging position.

Execution of the machine-executable instructions further causes the processor to: acquiring the light data using the at least one ambient light sensor while the subject support is in the imaging position. Execution of the machine-executable instructions further causes the processor to: using the light data to determine whether the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data. Execution of the machine-executable instructions further causes the processor to: providing a signal if the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data. The signal may for example indicate whether the coil is in the correct position or in the incorrect position. In different examples, the signal may take different forms. In one example, the signal may be a warning or other indicator to indicate whether the magnetic resonance imaging coil is not positioned in a position where it is capable of acquiring magnetic resonance imaging data. The signals may also take the form of data that is provided to other computing or software components and may be used to further control the magnetic resonance imaging system.

This embodiment may be beneficial in that the signal may serve as a stand-alone check of the operation of the magnetic resonance imaging system. The measurement of the light data is performed after the object support has been loaded into the imaging position. The knowledge of whether the coil is in the correct position can then be used to compare whether various other components of the magnetic resonance imaging system are functioning properly. For example, if the subject support is working properly, it actually moves the subject into the loading position. The signals may also be used to check the operation of the radio frequency system during calibration of the radio frequency system and associated radio frequency or imaging coils attached thereto. For example, the receive magnetic resonance imaging coil may be calibrated or configured prior to acquiring the magnetic resonance data. The signals can be used to determine whether the failure of the calibration is due to a failure of the configuration of the subject and the receiving magnetic resonance imaging coil, or possibly due to a radio frequency system.

In another embodiment, the main magnet is a cylindrical magnet having a bore. A light detection system is mounted to the bore. The light detection system can be arranged or attached such that the light data is measured from the imaging zone.

In another embodiment the magnetic resonance imaging system further comprises a multi-channel radio frequency system configured for acquiring the magnetic resonance imaging data. The radio frequency system comprises a body coil and the receive magnetic resonance imaging coil. The receive magnetic resonance imaging coil includes a plurality of receive elements. The memory also contains calibration commands configured to control the magnetic resonance imaging system to perform calibration of the plurality of receive elements of the receive magnetic resonance imaging coil using the body coil.

Execution of the machine-executable instructions further causes the processor to: calibrating a plurality of channels of the receive magnetic resonance imaging coil by executing the calibration commands. Execution of the machine-executable instructions further causes the processor to: providing a hardware fault signal if the calibration fails, wherein the signal indicates that the receiving magnetic resonance imaging coil is properly positioned. This embodiment may be advantageous as it may provide means for independent control in case the radio frequency system of the magnetic resonance imaging system is functioning properly.

In another embodiment, the light detection system is mounted to the receive magnetic resonance imaging coil. This embodiment may be advantageous as it may be implemented without any dedicated light source being provided in the room and/or the magnet. The properties of the light outside the magnetic resonance imaging system and the properties of the light within the imaging zone of the magnet may be different. For example, the light may have a different frequency and/or brightness that can be detected by at least one ambient light sensor. At least one ambient light sensor can be used to detect relatively complex or small changes in light. Various means may be useful for determining these changes. For example, various measurements may be made with coils external to the magnet and then with the magnetic resonance imaging coil placed in the correct position. This determination may be accomplished using an analytical model with thresholds. In other examples, machine learning may be useful for this. Machine learning can be useful for identifying various light patterns for a particular magnetic resonance imaging system.

In another embodiment, the magnetic resonance imaging system comprises an examination room for accommodating the main magnet. The examination room comprises a room lighting system. The main magnet comprises a magnet illumination system for illuminating the imaging zone and possibly also the bore of the magnetic resonance imaging magnet. The room lighting system is configured for generating a first type of light. The magnet illumination system is configured to generate a second type of light. Execution of the machine-executable instructions causes the processor to determine whether the receive magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data by distinguishing the first type of light from the second type of light. As mentioned above, this may be achieved in a number of different ways depending on the difference between the first type of light and the second type of light. This can be done using an analytical model or thresholding. In other examples, a neural network may be useful for distinguishing a first type of light from a second type of light.

In another embodiment, the first type of light differs from the second type of light by a color difference.

In another embodiment, the first type of light differs from the second type of light by an intensity difference.

In another embodiment, the first type of light differs from the second type of light in an oscillation frequency of the light.

In another embodiment, the first type of light differs from the second type of light by the intensity of the color component.

In another embodiment, the first type of light differs from the second type of light in a modulation of the first type of light and/or the second type of light.

In another embodiment, the magnet illumination system is configured for generating light with a spatially dependent frequency and/or a spatially dependent color coding and/or a spatially dependent modulation. This embodiment may be beneficial because by using spatial correlation in the illumination system, the position of the receiving magnetic resonance imaging coil may be better determined or more accurately determined.

In another embodiment execution of the machine executable instructions further causes the processor to determine a spatial position and/or orientation of the receive magnetic resonance imaging coil using the spatially dependent frequency, the spatially dependent color coding and/or the spatially dependent modulation produced by the magnet illumination system.

In another embodiment, the light detection system comprises a plurality of ambient light sensors configured for measuring ambient light distributed over a surface of the receiving magnetic resonance imaging coil. This embodiment may be beneficial because the use of multiple sensors enables a more accurate determination of the position and/or orientation of the receiving magnetic resonance imaging coil.

In another embodiment, the receive magnetic resonance imaging coil includes a preamplifier. The at least one ambient light sensor is attached to the preamplifier. The receiving magnetic resonance imaging coil comprises an optical fiber configured for each of the at least one ambient light sensor for channeling light from the surface of the receiving magnetic resonance imaging coil to the at least one ambient light sensor. This embodiment may be beneficial because all activated electronics are moved to the location where the preamplifier is located. Placing the ambient light sensor within or near the coil elements of the receiving magnetic resonance imaging coil may make acquisition of magnetic resonance imaging data more difficult or degraded. Thus, the use of optical fibers may improve the quality of magnetic resonance imaging data measured with the antenna.

In another embodiment, the light detection system is mounted to the main magnet such that the light data is measured from the imaging zone. The receiving magnetic resonance imaging coil comprises at least one light generating element. This embodiment may be beneficial because an ambient light sensor within the main magnet may be used to detect when the receive magnetic resonance imaging coil is placed in proximity to the detector.

In various embodiments or examples, the receive magnetic resonance imaging coil may generate light having a spatially dependent frequency, color coding, and/or modulation that is detectable by the light detection system of the main magnet. This enables identification and/or more accurate positioning of the receiving magnetic resonance imaging coil.

In another embodiment execution of the machine executable instructions causes the processor to determine whether the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data by inputting the light data into a decision module programmed to compare the light data to a predetermined criterion. The decision module may be beneficial in that the conditions that trigger the correct position of the receive magnetic resonance imaging coil can be determined and programmed analytically.

In another embodiment execution of the machine executable instructions causes the processor to determine whether the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data by inputting the light data to a trained machine learning module. For example, deep learning may be used to train neural networks to identify when the magnetic resonance imaging coil is in the correct position. This may be beneficial because the trained machine learning module may be configured or trained directly for a particular magnetic resonance imaging system.

In another embodiment the magnetic resonance imaging system further comprises an optical data transmission system. For example, the main magnet and the receiving magnetic resonance imaging coil may both have optical transmitters and sensors, which enable data exchange. The optical data transmission system is configured to form a bidirectional data link between the receive magnetic resonance imaging coil and the processor. The optical data transmission system comprises the light detection system. This can be used for different purposes. In some cases it may be used to more accurately locate the position of the receiving magnetic resonance imaging coil, or it may also be used to positively identify the particular receiving magnetic resonance imaging coil or even the type of its imaging coil.

In another aspect, the invention provides a computer program product comprising machine executable instructions for execution by a processor controlling a magnetic resonance imaging system. The magnetic resonance imaging system is configured for acquiring magnetic resonance imaging data from an imaging zone. The magnetic resonance imaging system includes a main magnet configured to generate a B0 magnetic field within the imaging zone. The magnetic resonance imaging system further comprises a subject support configured for moving the subject between the loading position and the imaging position. The magnetic resonance imaging system further comprises a receive magnetic resonance imaging coil configured for being placed on the subject. The magnetic resonance imaging system further comprises a light detection system comprising at least one ambient light sensor for measuring light data.

The light detection system performs any one of: is mounted to the main magnet such that the light data is measured from the imaging region; and mounted to the magnetic resonance imaging coil. Execution of the machine-executable instructions causes the processor to: moving the subject support from the loading position to the imaging position. Execution of the machine-executable instructions causes the processor to: acquiring the light data using the at least one ambient light sensor while the subject support is in the imaging position. Execution of the machine-executable instructions causes the processor to: using the light data to determine whether the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data. Execution of the machine-executable instructions causes the processor to: providing a signal if the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data. The advantages of which have been discussed previously.

In another aspect, the invention provides a method of operating a magnetic resonance imaging system. The magnetic resonance imaging system is configured for acquiring magnetic resonance imaging data from an imaging zone. The magnetic resonance imaging system includes a main magnet configured to generate a B0 magnetic field within the imaging zone. The magnetic resonance imaging system further comprises a subject support configured for moving the subject between the loading position and the imaging position. The magnetic resonance imaging system further comprises a receive magnetic resonance imaging coil configured for being placed on the subject. The magnetic resonance imaging system further comprises a light detection system comprising at least one ambient light sensor for measuring light data. The light detection system performs any one of: is mounted to the main magnet such that the light data is measured from the imaging region; and mounted to the magnetic resonance imaging coil. The method comprises the following steps: moving the subject support from the loading position to the imaging position. The method further comprises the following steps: acquiring the light data using the at least one ambient light sensor while the subject support is in the imaging position. The method further comprises the following steps: using the light data to determine whether the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data. The method further comprises the following steps: providing a signal if the receiving magnetic resonance imaging coil is positioned for acquiring the magnetic resonance imaging data. The advantages of which have been discussed previously.

In another aspect, the invention provides a receive magnetic resonance imaging coil including a preamplifier. At least one ambient light sensor is attached to the preamplifier. The receive magnetic resonance imaging coil includes an optical fiber for each of the at least one ambient light sensor. Each optical fiber is configured to channel light from a surface of the receive magnetic resonance imaging coil to one of the at least one ambient light sensor.

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

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as an apparatus, method or computer program product. Accordingly, aspects of the present invention may take the form of: an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit," module "or" system. Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer-readable media having computer-executable code embodied thereon.

Any combination of one or more computer-readable media may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. "computer-readable storage medium" as used herein encompasses any tangible storage medium that can store instructions that are executable by a processor of a computing device. The computer-readable storage medium may be referred to as a computer-readable non-transitory storage medium. The computer readable storage medium may also be referred to as a tangible computer readable medium. In some embodiments, the computer-readable storage medium is also capable of storing data that is accessible by a processor of the computing device. Examples of computer-readable storage media include, but are not limited to: a floppy disk, a magnetic hard drive, a solid state disk, flash memory, a USB thumb drive, Random Access Memory (RAM), Read Only Memory (ROM), an optical disk, a magneto-optical disk, and a register file for a processor. Examples of optical disks include Compact Disks (CDs) and Digital Versatile Disks (DVDs), e.g., CD-ROMs, CD-RWs, CD-R, DVD-ROMs, DVD-RWs, or DVD-R disks. The term "computer-readable storage medium" also refers to various types of recording media that can be accessed by a computer device via a network or a communication link. For example, data may be retrieved over a modem, over the internet, or over a local area network. Computer executable code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to: wireless, wired, fiber optic cable, RF, etc., or any suitable combination of the foregoing.

A computer readable signal medium may include a propagated data signal with computer executable code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to: electromagnetic, optical, or any suitable combination thereof. The computer readable signal medium may be any computer readable medium that: the computer readable medium is not a computer readable storage medium and can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

"computer memory" or "memory" is an example of computer-readable storage media. Computer memory is any memory that can be directly accessed by a processor. A "computer storage device" or "storage device" is another example of a computer-readable storage medium. The computer storage device is any non-volatile computer-readable storage medium. In some embodiments, the computer storage device may also be computer memory, or vice versa.

"processor" as used herein encompasses an electronic component capable of executing a program or machine-executable instructions or computer-executable code. References to a computing device that includes a "processor" should be interpreted as potentially containing more than one processor or processing core. The processor may be, for example, a multi-core processor. A processor may also refer to a collection of processors within a single computer system or distributed among multiple computer systems. The term "computing device" should also be read to possibly refer to a collection or network of multiple computing devices, each of which includes one or more processors. The computer executable code may be executed by multiple processors, which may be within the same computing device or even distributed across multiple computing devices.

The computer executable code may include machine executable instructions or programs that cause a processor to perform an aspect of the present invention. Computer executable code for performing operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language (e.g., Java, Smalltalk, C + +, etc.) and a conventional procedural programming language (e.g., the "C" programming language or similar programming languages), and compiled as machine executable instructions. In some instances, the computer executable code may be in a high level language form or in a pre-compiled form, and may be used in conjunction with an interpreter that generates the machine executable instructions on the fly.

The computer executable code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet service provider).

Aspects of the present invention are described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block or portion of the blocks of the flowchart, illustrations and/or block diagrams can be implemented by computer program instructions in computer-executable code where appropriate. It will also be understood that blocks of the various flow diagrams, illustrations, and/or block diagrams, when not mutually exclusive, may be combined. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

As used herein, a "user interface" is an interface that allows a user or operator to interact with a computer or computer system. The "user interface" may also be referred to as a "human interface device". The user interface may provide information or data to and/or receive information or data from an operator. The user interface may enable input from an operator to be received by the computer and may provide output from the computer to a user. In other words, the user interface may allow an operator to control or manipulate the computer, and the interface may allow the computer to indicate the effect of the operator's control or manipulation. Displaying data or information on a display or graphical user interface is an example of providing information to an operator. Receiving data through a keyboard, mouse, trackball, trackpad, pointing stick, tablet, joystick, gamepad, webcam, head-mounted device, foot pedal, wired glove, remote control, and accelerometer are all examples of user interface components that enable receiving information or data from an operator.

As used herein, "hardware interface" encompasses an interface that enables a processor of a computer system to interact with and/or control an external computing device and/or apparatus. The hardware interface may allow the processor to send control signals or instructions to an external computing device and/or apparatus. The hardware interface may also enable the processor to exchange data with external computing devices and/or apparatus. Examples of hardware interfaces include, but are not limited to: a universal serial bus, an IEEE 1394 port, a parallel port, an IEEE 1284 port, a serial port, an RS-232 port, an IEEE-488 port, a Bluetooth connection, a wireless local area network connection, a TCP/IP connection, an Ethernet connection, a control voltage interface, a MIDI interface, an analog input interface, and a digital input interface.

"display" or "display device" as used herein encompasses an output device or user interface suitable for displaying images or data. The display may output visual, auditory, and/or tactile data. Examples of displays include, but are not limited to: computer monitors, television screens, touch screens, tactile electronic displays, braille screens, Cathode Ray Tubes (CRTs), memory tubes, bi-stable displays, electronic paper, vector displays, flat panel displays, vacuum fluorescent displays (VFs), Light Emitting Diode (LED) displays, electroluminescent displays (ELDs), Plasma Display Panels (PDPs), Liquid Crystal Displays (LCDs), organic light emitting diode displays (OLEDs), projectors, and head mounted displays.

Magnetic Resonance Imaging (MRI) data is defined herein as being measurements of radio frequency signals emitted by atomic spins recorded using an antenna of a magnetic resonance apparatus during a magnetic resonance imaging scan. A magnetic resonance image or MR image is defined herein as being a two-dimensional visualization or a three-dimensional visualization of the reconstruction of anatomical data contained within the magnetic resonance imaging data. Such visualization can be performed using a computer, for example.

Ambient light sensors as used herein may encompass commercially available ambient light sensors used in consumer electronics (e.g., smart phones, car displays, LCT televisions, or notebook computers). Ambient light sensors are a common type of electronic component. More broadly, an environmental sensor may encompass a photodetector or photodiode that receives light from a solid angle greater than a selected solid angle. The selected solid angle may be greater than any of: 3/2Pi, 3/4Pi, and 1/2 Pi.

Drawings

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

figure 1 illustrates an example of a magnetic resonance imaging system;

figure 2 shows a further view of the magnetic resonance imaging system of figure 1;

figure 3 illustrates a further example of a magnetic resonance imaging system;

figure 4 shows a further view of the magnetic resonance imaging system of figure 1;

figure 5 illustrates a method of operating the magnetic resonance imaging system of figure 1 or figure 3;

figure 6 illustrates a further example of a magnetic resonance imaging system;

figure 7 illustrates a further example of a magnetic resonance imaging system;

figure 8 illustrates a further example of a magnetic resonance imaging system;

figure 9 illustrates an example of a receive magnetic resonance imaging coil; and is

Figure 10 illustrates an example of a receive magnetic resonance imaging coil.

List of reference numerals

100 magnetic resonance imaging system

102 examination room

103 room lighting system

104 main magnet

106 magnet bore

107 magnet illumination system

108 imaging zone

110 magnetic field gradient coil

112 magnetic field gradient coil power supply

114 receive magnetic resonance imaging coil

115 ambient light sensor

116 transceiver

118 object

120 object support

121 loading position

122 actuator

126 computer system

128 hardware interface

130 processor

132 user interface

134 computer memory

140 machine-executable instructions

142 pulse sequence commands

144 optical data

146 signal

148 decision module

150 trained machine learning module

152 initial light data

154 optional calibration command

160 light of a first type

162 light of a second type

200 imaging position

209 region of interest

240 calibration results

242 magnetic resonance imaging data

244 magnetic resonance image

300 magnetic resonance imaging system

302 light generating element

304 light from the light generating element

500 move a subject support from a loading position to an imaging position

502 collect light data using at least one ambient light data when the subject support is in the imaging position

504 uses the light data to determine whether a receiving magnetic resonance imaging coil is positioned for acquiring magnetic resonance imaging data

506 if the receive magnetic resonance imaging coil is not positioned for acquiring magnetic resonance imaging data, providing a mis-aligned signal

800 body coil

900 coil element

902 preamplifier

1000 optical fiber

1002 lens

Detailed Description

In the drawings, like numbered elements are either equivalent elements or perform the same function. Elements that have been previously discussed will not necessarily be discussed again in later figures if their functionality is equivalent.

Figure 1 illustrates an example of a magnetic resonance imaging system 100. The magnetic resonance imaging system 100 comprises an examination room 102 with a room illumination system 103.

The magnetic resonance imaging system 100 includes a magnet or main magnet 104. The magnet 104 is a superconducting cylindrical magnet having a bore 106 therethrough. Within the bore of the magnet 106 is a magnet illumination system 107. The room lighting system 103 generates a first type of light 160. The magnet illumination system 107 generates a second type of light 162.

Different types of magnets may also be used; for example, a split cylindrical magnet and a so-called open magnet may be used at the same time. The split cylindrical magnet is similar to a standard cylindrical magnet except that the cryostat has been split into two parts to allow access to the iso-plane of the magnet, such a magnet may be used, for example, in conjunction with charged particle beam therapy. An open magnet has two magnet parts, one above the other, with sufficient space in between to accommodate the object: the regional arrangement of these two parts is similar to that of a helmholtz coil. Open magnets are popular because the subject is not so restricted. Inside the cryostat of the cylindrical magnet there is a set of superconducting coils. Within the bore 106 of the cylindrical magnet 104 is an imaging zone 108, in which imaging zone 108 the magnetic field is sufficiently strong and uniform to perform magnetic resonance imaging.

Also within the bore 106 of the magnet is a set of magnetic field gradient coils 110 for acquiring preliminary magnetic resonance data to spatially encode magnetic spins within the imaging zone 108 of the magnet 104. The magnetic field gradient coils 110 are connected to a magnetic field gradient coil power supply 112. The magnetic field gradient coils 110 are intended to be representative. Typically, the magnetic field gradient coils 110 comprise three separate sets of coils that are used for spatial 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 110 is controlled as a function of time and may be ramped or pulsed.

A subject 118 is shown lying on a subject support 120. There is a receive magnetic resonance imaging coil 114, in which case the receive magnetic resonance imaging coil 114 is a surface coil. The receive magnetic resonance imaging coil 114 has an ambient light sensor 115 mounted thereon. The subject support 120 is currently in the loading position 121. The ambient light sensor 115 is exposed to the first type of light 160. The ambient light sensor 115 can measure or detect the presence of the first type of light 160 and determine that the object 118 is in the loading position 121. There is an actuator 122 capable of moving the subject support 120 into the bore 106 of the magnet 104.

The receive magnetic resonance imaging coil 114 is used to receive radio transmissions from spins also within the imaging zone 108. The radio frequency antenna may comprise a plurality of coil elements. The radio frequency antenna may also be referred to as a channel or antenna. The radio frequency coil 114 is connected to a radio frequency receiver or transceiver 116. The radio frequency coil 114 and the radio frequency transceiver 116 may be replaced by separate transmit and receive coils and separate transmitters and receivers. The radio frequency coil 114 may also have multiple receive/transmit elements and the radio frequency transceiver 116 may have multiple receive/transmit channels. For example, if a parallel imaging technique such as SENSE is performed, the radio frequency coil 114 will have multiple coil elements.

The transceiver 116, the gradient controller 112, and the actuator 122 of the subject support 120 are shown as being connected to a hardware interface 128 of a computer system 126. The computer system also includes a processor 130 in communication with the hardware system 128, memory 134, and user interface 132. Memory 134 may be any combination of memory accessible to processor 130. This may include devices such as main memory, cache memory, and may also include non-volatile memory such as flash RAM, hard drives, or other storage devices. In some examples, memory 134 may be considered a non-transitory computer-readable medium.

The memory 134 is shown as containing machine executable instructions 140. The machine-executable instructions 140 enable the processor 130 to send commands to control various components of the magnetic resonance imaging system 100. The machine-executable instructions 140 also enable the processor 130 to perform various data analysis and data manipulation tasks. The memory 134 is also shown as containing pulse sequence commands 142 that enable the magnetic resonance imaging system 100 to acquire magnetic resonance imaging data from the subject 118 when the subject is within the imaging zone. The memory 134 is shown as containing light data 144, the light data 144 being data measured with the ambient light sensor 115. The memory 134 is also shown as containing initial light data 152. The initial light data 152 is light data measured with the object and the object support 120 at the loading position 121. The initial light data 152 thus describes the first type of light 160.

The memory 134 is also shown as containing a signal 146, which signal 146 can be used to indicate whether the receiving magnetic resonance imaging coil 114 is in position to acquire magnetic resonance data from the imaging zone 108. The memory 134 is also shown as containing an optional decision module 148 that is capable of using the light data 144 acquired within the bore 106 of the magnet and optionally using the initial light data 152 to determine whether the receiving magnetic resonance imaging coil 114 is in the correct position for acquiring magnetic resonance data. The memory 134 is also shown as containing an optional training machine learning module 150, the training machine learning module 150 may be, for example, a neural network that has been trained to recognize or distinguish a first type of light 160 from a second type of light 162.

The decision module 148 and/or the trained machine learning module 150 may be trained to also use the light data 144 to determine the position and/or orientation of the receiving magnetic resonance imaging coil. The memory 134 is also shown as containing optional calibration commands 154 that enable the radio frequency system 116 and the receive magnetic resonance imaging coil 114 to be calibrated once the receive magnetic resonance imaging coil 114 is in place in the magnet 154. This may be used, for example, when the radio frequency system 116 contains multiple receive channels for the receive magnetic resonance imaging coil 114.

Figure 2 shows a further view of the magnetic resonance imaging system 100 of figure 1. In this example, the subject support 120 has been moved to the imaging position 200. The ambient light sensor 115 is now exposed to the second type of light 162 in the bore of the magnet 106. The light data 144 can then be used to determine that the receiving magnetic resonance imaging coil 114 is in the correct position for acquiring magnetic resonance imaging data from the region of interest 209 within the imaging zone 108.

The first type of light 160 and the second type of light 162 may be distinguished in various ways (e.g., color, oscillation frequency, modulation frequency, brightness), or may be distinguished using the presence of various color components.

The computer memory 134 is also shown as containing calibration results 240 resulting from the execution of the calibration commands 154. The calibration result 240 can be compared to the signal 146 to indicate whether the magnetic resonance imaging system 100 is operating properly and whether the pulse sequence commands 142 are allowed to be executed. The memory 134 is also shown as containing magnetic resonance imaging data 242, the magnetic resonance imaging data 242 being acquired by controlling the magnetic resonance imaging system with the pulse sequence commands 142. The memory 134 is also shown as containing a magnetic resonance image 244 that has been reconstructed from the magnetic resonance imaging data 242.

Figure 3 shows an alternative magnetic resonance imaging system 300. The magnetic resonance imaging system 300 depicted in fig. 3 is similar to the magnetic resonance imaging system 100 illustrated in fig. 1 and 2, except that the ambient light sensor is now mounted within the bore 106 of the magnet 104 and the receiving magnetic resonance imaging coil 114 comprises a light generating element 302. The light generating element 302 generates light 304. The ambient light sensor 115 is capable of detecting light 304 from the light generating element 302. The magnetic resonance imaging system is still shown as comprising a room illumination system 103 generating a first type of light 160. This may or may not be present. In all examples, the ambient light sensor 115 may not necessarily be sensitive to the first type of light 160.

Figure 4 shows a further view of the magnetic resonance imaging system 300 of figure 3. The view in figure 4 is similar to the view illustrated in figure 3 for the other magnetic resonance imaging system 100. In this example of fig. 4, we see that the subject support 120 has been moved into the imaging position 200. The light generating element 302 is now close to the ambient light sensor 115. The ambient light sensor 115 can then detect that the receiving magnetic resonance imaging coil 114 is in the correct position for acquiring the magnetic resonance imaging data 242.

Figure 5 shows a flow chart illustrating a method of operating the magnetic resonance imaging system 100 of figures 1 and 2 or the magnetic resonance imaging system 300 illustrated in figures 3 and 4. First in step 500, the subject support 120 is moved from the loading position 121 to the imaging position 200. Next, in step 502, light data 144 is acquired using the ambient light sensor 115. This is done while the subject support 120 is in the imaging position 200. Next in step 504, it is determined using the light data 144 whether the receiving magnetic resonance imaging coil 114 is positioned for acquiring magnetic resonance imaging data 242. This may be performed, for example, using decision module 148 or trained machine learning module 150. Finally, in step 506, if the receiving magnetic resonance imaging coil 114 is positioned for acquiring the magnetic resonance imaging data 242, the signal 146 is provided.

In the example illustrated in figures 1-4, the ambient light sensor 115 can generally inform whether the receiving magnetic resonance imaging coil 114 is properly positioned. However, a larger number of ambient light sensors 115 and/or magnet illumination systems 107 and/or light generating elements may be provided, enabling the position and orientation of the receiving magnetic resonance imaging coil 114 to be determined.

Fig. 6 illustrates an example in which a linear position along an axis of a magnet can be determined. In this example, there are multiple ambient light sensors 115 on the receive magnetic resonance imaging coil 114. There are many magnet lights used in magnet lighting systems 107. The properties of the light generated by the magnet illumination system 107 can vary linearly. For example, color, oscillation frequency, modulation of light, color components, or other characteristics can be varied such that a wide variety of ambient light sensors 115 can detect changes in measured ambient light. Alternatively, a large number of light generating elements can be used in place of the ambient light sensor 115, and the ambient light sensor can instead be mounted on the bore 106 of the magnet 104.

Figure 7 illustrates a further example of being able to determine the orientation of the receive magnetic resonance imaging coil 114. Fig. 7 shows a cross-sectional view of the magnet 104. In this example, the receive magnetic resonance imaging coil 114 again has a plurality of ambient light sensors 115. In the bore 106 of the magnet 104 there are again a plurality of lamps for the magnet illumination system 107. The properties of the light generated by the magnet illumination system 107 can vary as a function of the angle about the axis of the magnet. Different ambient light sensors 115 thus measure different light having different properties. This can be used to infer the orientation of the receive magnetic resonance imaging coil 114. As in the linear case illustrated in fig. 6, the lamp 107 can have its properties varied, e.g. color, intensity, oscillation frequency, with a modulated signal or other properties, which enables identification of the orientation of the receiving magnetic resonance imaging coil 114.

The linear encoding illustrated in figure 6 can be combined with the radial encoding in figure 7 so that a very accurate picture of the position and orientation of the receiving magnetic resonance imaging coil 114 can be determined. For example, modulation may be performed in one of the two coordinates and then color or intensity may be used in the other coordinate. The decision module 148 and/or the trained machine learning module 150 may be adapted to determine the position and orientation also using a scheme as illustrated in fig. 6 and 7. It should be noted that the example in figure 7 can also be modified, wherein the ambient light sensor 115 is mounted on the wall of the bore of the magnet 106 and the light generating element is positioned on the receiving magnetic resonance imaging coil 114. The individual light-generating elements can then generate light, which is different and can be measured using the ambient light sensor 115.

The Magnetic Resonance (MR) Receive (RX) coil receiver (receive magnetic resonance imaging coil 114) in the art is preferably calibrated in terms of time alignment (synchronization), gain, etc. parameters. This may provide a means of distinguishing the position of the coil outside or inside the scanner bore independent of the actual existing measures. This helps to distinguish between a calibration failure due to a real defect and a situation where the coil is only in the wrong position.

For some of these parameters, a low power calibration signal is transmitted via the body coil. Unfortunately, when this calibration procedure fails, it is not clear whether the coil (its preamplifier or digitizer) is damaged or whether the coil is located just outside the body coil (in which case the calibration signal is too weak).

For radiation therapy or MR/PET, knowing the positioning of the RF coils (shields) helps to prevent therapy/treatment planning errors.

Currently, due to uncertainty, not all failed calibration phases will result in scan aborts to avoid too high false positive coil failure detection rates. This means that in some cases where there is a real fault, scanning will be performed but image artefacts will result and repeated scanning will be required.

To distinguish between these two cases, the coil position can be determined either inside the body coil (imaging position 200) or outside the body coil (loading position 121).

To create added value, the new measures can be independent of existing RF-based components.

One measure is to equip each coil element with a photodiode (ambient light sensor 115) to detect ambient light 160, 162. When the light outside the scanner and the light inside the scanner are coded differently, the coil position is easily determined.

Figure 8 illustrates an alternative view of the magnetic resonance imaging system 100. The magnetic resonance imaging system is shown to additionally include a body coil 800. The body coil is not shown in fig. 1 and 2, but may also be mounted there. The body coil 800 may be particularly useful during calibration of the receive magnetic resonance imaging coil 114. The above fig. 8 shows an overview. As usual, the scanner is equipped with a lamp (magnet illumination system 107) inside the bore and a corresponding ceiling lamp (room illumination system 103) inside the cage.

In the given example, the coil array is actually placed in such a way that part of it is inside the body coil (calibration work) and another part is outside the body coil (calibration easily fails). Fig. 9 and 10 below show a detailed sketch of one coil element 900. Each coil element 900 is equipped with at least one photodiode 115 that detects ambient light. The diode can be placed in the center of the corresponding coil element 900, or when the coil is small enough, it can be placed on the preamplifier or ADC PCB. Optionally, a lens 1002 and fiber 1000 may be used to pick up light at a first location while placing a detector at another location.

Typically the coil cover is made of a translucent material so that the detector can be hidden under the coil cover. The AD conversion of the detector signals can be done as part of the digital coil infrastructure.

Figure 9 illustrates an example of a receive magnetic resonance imaging coil 114. The receive magnetic resonance imaging coil includes one or more coil elements 900 and a preamplifier 902. The ambient light sensor 115 is shown mounted within or around the coil element 900. The ambient light sensor 115 will be mounted such that it can measure ambient light exposed on the surface of the receiving magnetic resonance imaging coil 114.

Figure 10 shows a further example of a receive magnetic resonance imaging coil. In this example, the ambient light sensor 115 is attached or mounted to the preamplifier 902. This has the advantage of removing the electronics from the coil element 900. To allow light to reach the ambient light sensor 115, the optical fiber 100 is coupled to a lens 1002 mounted on the surface of the receiving magnetic resonance imaging coil 114. Only a single sensor 115 and optical fiber 1000 are shown, but in this way a greater number of sensors 115 may be incorporated without interfering with the measurements made by the receive magnetic resonance imaging coil 114. This may, for example, allow the position and orientation of the receive magnetic resonance imaging coil 114 to be determined more accurately.

The actual encoding of the light can be done (for example only) by:

different colours (warm and cold white)

Light of different intensity over time (e.g. 200Hz oscillating ceiling lamp versus 100Hz bore lamp, modulation invisible to the human eye)

Intensity of one component of light over time (RGB LED)

When the coil is moved into the bore, it will detect the corresponding change in the optical properties and report it to the back end.

If the current illumination in the ceiling light and the current bore light produce different types of light, the example can be implemented without changing these lights or installing additional lights.

However, the normalization of the illumination simplifies the detection of the position, in particular the definition of the detector technology and the threshold values.

In further advance, the bore light near the service end and the bore light at the patient end also emit differently coded light. This allows positioning of the coil along the bore.

While 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 can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. Although some measures are recited in mutually different dependent claims, this does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems. Any reference signs in the claims shall not be construed as limiting the scope.