Method for determining a distance between a patient and an enclosure surrounding a patient reception area

Description

[0001] The present invention relates to a method for determining a distance of a patient from a housing surrounding a patient receiving area of ​​a magnetic resonance device during a magnetic resonance examination. Furthermore, the present invention relates to a magnetic resonance device that is designed to carry out the method for determining a distance of a patient from a housing surrounding a patient receiving area during a magnetic resonance examination. Furthermore, the present invention relates to a computer program that is designed to carry out the method for determining a distance of a patient from a housing surrounding a patient receiving area during a magnetic resonance examination.

[0002] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identity are included.

[0003] In magnetic resonance imaging, the spins of an object under examination, such as a patient, are deflected from their resting position using resonant radiofrequency (RF) pulses to generate a measurable signal or to achieve a targeted change in contrast. Applying the RF pulses transfers energy into the object under examination, which can lead to heating of the object and is described by the "specific absorption rate" (SAR). SAR limits must be adhered to, although these limits vary depending on the body region. These limits, for example, are based on an averaging time of 6 minutes and are therefore independent of the duration of a particular measurement protocol.Particularly with magnetic resonance sequences such as the SPACE sequence (3D turbo spin echo sequence), the TSE sequence (turbo spin echo sequence), the HASTE sequence (Half Fourier-Acquired Single Shot Turbo Spin Echo sequence), or even measurements with SMS (Simultaneous Multi Slice), which use RF pulses in rapid succession and with high amplitudes, high SAR values ​​can result that exceed the specified limits. This is detected by SAR monitoring and prediction, which may lead to, for example, the need to add pauses after the measurement and / or reduce flip angles or slices.

[0004] In addition to the SAR limits for whole-body examinations and / or individual body regions, other limiting factors should also be taken into account during a magnetic resonance examination of a patient. In particular, protection against contact, especially the distance between the patient and any enclosure surrounding the patient admission area, especially a radio-frequency antenna unit, is important. Significantly increased RF field amplitudes occur locally in the immediate vicinity of the inner wall of the patient admission area (e.g., where capacitors are located directly behind the tunnel wall). If the patient is positioned in such a way that body parts are in an area with locally significantly increased RF field amplitudes, a correspondingly increased power absorption occurs in the tissue located there, so that RF burns are possible despite compliance with the prescribed global SAR limits.To counteract this risk, a minimum distance from the enclosure surrounding the patient admission area is generally prescribed, which the user can achieve, for example, by using spacer cushions. To avoid excluding obese patients from the examination, this minimum distance should be as small as possible - e.g., 5 mm. At distances greater than the selected minimum distance (e.g., 5 mm), dangerous power absorption intensities may still occur locally in the tissue under unfavorable circumstances, so that even if the prescribed global SAR limits are observed, RF burns cannot be ruled out. To avoid RF burns under the aforementioned unfavorable circumstances, a contact protection function is provided that detects the unfavorable circumstances and then limits the RF transmission power accordingly, thus preventing RF burns.Unfavorable circumstances occur, for example, when the total currents in the end rings of the high-frequency antenna unit are particularly high.

[0005] To date, it has been assumed in magnetic resonance examinations that, firstly, the minimum distance is maintained, if necessary through the use of spacer pads, and secondly that tissue could be located at a distance of only 5 mm. The RF power to be applied is then determined or estimated based on a reference voltage determined during an adjustment measurement of the radio-frequency antenna unit. To avoid RF burns for the patient's possible position close to the tunnel wall, the RF power to be applied is restricted and / or limited. In many cases, however, the distance between the patient and the tunnel wall will be greater, making this limitation of the RF power unnecessary.

[0006] DE 10 2012 205 236 A1 discloses a method for operating an imaging medical modality, in particular a magnetic resonance imaging scanner. This method comprises a tuning process in which an electromagnetic field is generated by the modality and image data is generated using the electromagnetic field. Based on the image data, a distance between a patient and a wall of the modality is determined.

[0007] DE 10 2018 209 691 A1 discloses a method for automatically determining a collision probability of an object positioned on a patient support device with a housing surrounding a patient receiving area of ​​a medical imaging device. 3D position data of the objects positioned on the patient support device are first acquired using a 3D acquisition unit, and the 3D position data are subsequently evaluated using an evaluation unit. The 3D position data are evaluated with respect to a distance of the object arranged on the patient support device relative to the housing surrounding the patient receiving area in the radial direction. The collision probability is determined depending on the distance.

[0008] The present invention is based, in particular, on the object of providing a precise determination of the patient's distance from a housing surrounding the patient receiving area for protecting the patient from contact during a magnetic resonance examination. This object is achieved by the features of the independent claims. Advantageous embodiments are described in the subclaims.

[0009] The invention is based on a method for determining a distance of a patient from a housing of a magnetic resonance device surrounding a patient receiving area during a magnetic resonance examination, comprising the following method steps: Providing first size information of the patient, wherein the first size information is provided before the start of the magnetic resonance examination, acquiring magnetic resonance data of the patient during the magnetic resonance examination and determining second size information of the patient based on the acquired magnetic resonance data, and determining the distance of the patient to the enclosure surrounding the patient receiving area based on the first size information of the patient and based on the second size information of the patient.

[0010] The magnetic resonance device preferably comprises a medical and / or diagnostic magnetic resonance device that is designed and / or configured to acquire medical and / or diagnostic image data, in particular medical and / or diagnostic magnetic resonance image data, of a patient. Furthermore, the magnetic resonance device according to the invention can also be integrated into a combined magnetic resonance-PET system together with a PET device (positron emission tomography device).

[0011] The magnetic resonance device comprises a scanner unit. The scanner unit of the magnetic resonance device preferably comprises a magnet unit for acquiring the medical and / or diagnostic image data. The scanner unit, in particular the magnet unit, comprises a base magnet, a gradient coil unit, and a radio-frequency antenna unit. The radio-frequency antenna unit is fixedly arranged within the scanner unit.

[0012] The base magnet is designed to generate a homogeneous basic magnetic field with a defined magnetic field strength, such as a magnetic field strength of 0.55 T, 1.5 T, 3 T, or 7 T, etc. In particular, the base magnet is designed to generate a strong, constant, and homogeneous basic magnetic field. The homogeneous basic magnetic field is preferably arranged and / or located within a patient receiving area of ​​the magnetic resonance device. The gradient system is designed to generate magnetic field gradients that are used for spatial encoding during imaging.

[0013] For a magnetic resonance examination, the patient, in particular the area of ​​the patient to be examined, is positioned within the patient receiving area of ​​the magnetic resonance device. The patient receiving area is at least partially surrounded by the scanner unit, in particular cylindrically surrounded by the scanner unit. The housing surrounding the patient receiving area can be formed integrally and / or integrally with the radio-frequency antenna unit of the scanner unit, for example, by the housing surrounding the patient receiving area comprising a side of the radio-frequency antenna unit facing the patient receiving area.

[0014] A field of view (FOV) and / or an isocenter of the magnetic resonance device is preferably arranged within the patient acquisition area. The FOV preferably comprises a detection region of the magnetic resonance device within which the conditions for acquiring medical image data, in particular magnetic resonance image data, are present within the patient acquisition area, such as a homogeneous basic magnetic field. The isocenter of the magnetic resonance device preferably comprises the region and / or point within the magnetic resonance device that has the optimal and / or ideal conditions for acquiring medical image data, in particular magnetic resonance image data. In particular, the isocenter comprises the most homogeneous magnetic field region within the magnetic resonance device.

[0015] The magnetic resonance apparatus further comprises a system control unit, wherein the system control unit comprises at least one computing module and / or a processor. The system control unit is configured to control the individual components of the magnetic resonance apparatus for at least one magnetic resonance data acquisition and / or magnetic resonance data reconstruction. The system control unit generates corresponding control commands and / or control data for the individual components of the magnetic resonance apparatus depending on software executed by the processor and / or the computing module.

[0016] In particular, the system control unit is designed to execute computer-readable instructions for controlling the individual components of the magnetic resonance apparatus. In particular, the system control unit comprises a memory unit, wherein computer-readable information is stored on the memory unit, wherein the system control unit is designed to load the computer-readable information from the memory unit and to execute the computer-readable information for controlling the individual components of the magnetic resonance apparatus. The components of the system control unit can predominantly be designed in the form of software components. In principle, however, these components can also be partially implemented in the form of software-supported hardware components, for example FPGAs or the like, particularly when particularly fast calculations are required.Of course, it is also conceivable that several of the components mentioned are implemented together in the form of a single software component or software-supported hardware component.

[0017] The magnetic resonance examination preferably comprises at least one sequence for magnetic resonance data acquisition. A sequence for a magnetic resonance examination comprises, in particular, a logical sequence of radiofrequency pulses (RF pulses), gradient pulses, and acquisition periods for controlling data acquisition for magnetic resonance data acquisition for medical and / or diagnostic findings. A magnetic resonance examination on a patient can comprise a sequence of multiple sequences.

[0018] The first height information of the patient is provided before the start of the magnetic resonance examination. The first height information can be recorded during patient registration and then made available afterwards. Furthermore, the first height information can already be stored in a memory and / or a database, for example in the case of first height information determined during a preliminary examination and / or a previous examination. Furthermore, the first height information can also be recorded and made available during preparation for the magnetic resonance examination. The magnetic resonance examination starts and / or only begins when the patient, together with the patient table, has been moved into the patient admission area and is positioned in an examination position within the patient admission area.

[0019] The first size information preferably comprises an extent of the patient, in particular an extent of the patient in the transverse direction of the patient table. Of particular importance here is an extent of that region of the patient which is arranged within the patient acquisition area during the magnetic resonance examination. In particular, the first size information of the patient comprises size information and / or extent information and / or an outline of the patient which is arranged outside the FOV in the transverse direction of the patient table. The first size information of the patient is preferably provided by means of a provision unit of the magnetic resonance device. The provision unit can comprise a camera and / or a database and / or a control unit and / or further units deemed appropriate by a person skilled in the art.

[0020] The acquisition of magnetic resonance data for determining the second item of patient height information takes place during the magnetic resonance examination. The acquisition of the magnetic resonance data takes place using an acquisition unit, wherein the acquisition unit comprises the scanner unit of the magnetic resonance device. The acquisition of magnetic resonance data for determining the second item of patient height information can preferably include special adjustment measurements from which the second item of patient height information can be determined. Such adjustment measurements are preferably performed during measurement pauses and / or between individual radiofrequency pulses of the magnetic resonance examination. Such an adjustment measurement can also be performed at the beginning of the magnetic resonance examination. However, the entire extent of the patient in the transverse direction of the patient table cannot be determined and / or determined using the magnetic resonance data.The second size information is limited to the field of view of the magnetic resonance imaging device and includes the region of the patient to be examined and the regions of the patient arranged around the region to be examined. In particular, the second size information contains a position of the region to be examined and / or an anatomy of the patient within the field of view.

[0021] To determine and / or ascertain the second size information, magnetic resonance images are reconstructed from the acquired magnetic resonance data. Preferably, the second size information of the patient comprises magnetic resonance image data of the patient.

[0022] The determination of the distance between the patient and the enclosure surrounding the patient and the patient receiving area, in particular the high-frequency antenna unit, is preferably carried out by means of a determination unit. The determination unit can comprise a computing unit and / or a control unit. In particular, based on the first size information and the second size information, the determination unit determines and / or calculates a body model of the patient, such as a virtual body model. The body model is limited to the partial area of ​​the patient located within the patient receiving area.For example, if the second size information comprises magnetic resonance image data of the patient's torso arranged within the FOV, an overall image of the partial region of the patient located within the patient acquisition area can be created using the first size information, which comprises, for example, an extent and / or position of the patient's arms.

[0023] In addition, the distance between the patient and the enclosure surrounding the patient reception area, in particular the radio-frequency antenna unit, can be determined using a machine learning method, also known as a deep learning method, which is based on an artificial neural network. An artificial neural network (ANN) is, in particular, a network of artificial neurons simulated in a computer program. The artificial neural network is typically based on a network of several artificial neurons. The artificial neurons are typically arranged in different layers. The artificial neural network usually comprises an input layer and an output layer, the neuron output of which is the only one visible in the artificial neural network.Layers located between the input layer and the output layer are typically referred to as hidden layers. Typically, an architecture and / or topology of an artificial neural network is first initiated and then trained in a training phase for a specific task or for multiple tasks in one training phase. Training the artificial neural network typically involves changing the weight of a connection between two artificial neurons of the artificial neural network. Training the artificial neural network can also involve developing new connections between artificial neurons, deleting existing connections between artificial neurons, adjusting thresholds of the artificial neurons, and / or adding or deleting artificial neurons.The artificial neural network was trained in advance to determine the distance of the patient to the enclosure surrounding the patient reception area, in particular the high-frequency antenna unit.

[0024] The invention has the advantage that the distance between the patient and the enclosure surrounding the patient receiving area, in particular the radio-frequency antenna unit, can be precisely determined. Furthermore, this also provides a high level of patient safety during the magnetic resonance examination. This also allows safety measures, such as limiting and / or reducing the RF power of the RF pulses to be delivered, to be initiated only when the distance between the patient and the enclosure surrounding the patient receiving area is actually below a threshold value, for example, less than 5 mm, thus avoiding unnecessary restrictions on the RF power during the magnetic resonance examination. This also allows unnecessary restrictions on the RF transmission to be avoided.

[0025] In an advantageous development of the method according to the invention, it can be provided that the first size information is provided by means of a camera. In this case, the provision unit preferably comprises the camera. The camera can comprise a 2D camera or a 3D camera. In this case, the camera is particularly advantageously arranged on a front side of the magnetic resonance device, in particular the scanner unit. In addition, the camera can also be arranged in an area arranged in front of the patient reception area in the direction of entry of the patient table, such as on the ceiling of the area arranged in front of the patient reception area. This embodiment of the invention has the advantage that current and / or accurate first size information about the patient can always be provided in a simple manner.

[0026] In an advantageous development of the method according to the invention, it can be provided that the first size information is provided by means of a database and / or patient registration. In this case, the provision unit preferably comprises the database and / or a computing unit with a user interface for recording the patient registration. For example, initial size information from previous examinations can be stored in the database. In addition, initial size information about the patient can also be recorded during patient registration and made available for determining the distance between the patient and the housing surrounding the patient receiving area, in particular the radio-frequency antenna unit. During patient registration, the patient is examined prior to the magnetic resonance examination, and all data relevant to the magnetic resonance examination is recorded from the patient.In this way, existing data, in particular initial size information, of the patient can be provided particularly quickly for determining a distance of the patient to the enclosure surrounding the patient reception area, in particular the high-frequency antenna unit.

[0027] In an advantageous development of the method according to the invention, it can be provided that the first size information comprises a region in at least one spatial direction, wherein this region in the at least one spatial direction is arranged outside the FOV of the magnetic resonance device. Preferably, the at least one spatial direction comprises a transverse direction of the patient table of the patient support device. The patient table is preferably retracted into the patient receiving area in the longitudinal direction of the patient table. The transverse direction is aligned perpendicular to the longitudinal direction of the patient table. In the transverse direction, the patient table borders on both sides on the housing surrounding the patient receiving area, in particular on the radio-frequency antenna unit. The FOV of a magnetic resonance device is arranged around the isocenter and comprises only a partial region, in particular a central region, of the patient receiving area.In the at least one spatial direction, in particular in the transverse direction of the patient table, the FOV does not cover the entire patient imaging area. However, the first patient size information contains a region of the patient that extends beyond the FOV in the at least one spatial direction, in particular in the transverse direction of the patient table. This region preferably also covers, in the at least one spatial direction, an edge region of the patient imaging area that is located outside the FOV in the at least one spatial direction.

[0028] This embodiment of the invention has the advantage that both pieces of size information, in particular the first piece of size information and the second piece of size information, can provide a complete recording of the patient's dimensions for determining the patient's distance from the enclosure surrounding the patient receiving area, in particular the radio-frequency antenna unit. In particular, the second piece of size information determines the patient's position relative to the isocenter, and the patient model, for example, a virtual patient model, is completed using the first piece of size information.

[0029] In an advantageous development of the method according to the invention, it can be provided that the acquisition of magnetic resonance data for determining the second item of patient size information is carried out with a maximum FOV. The maximum FOV of a magnetic resonance device preferably comprises a device-specific maximum FOV. The maximum FOV is preferably aligned to its maximum in the coronal plane. For example, such a maximum FOV can be 50 cm in the z-direction and 45 cm each in the x-direction and y-direction. The z-direction corresponds to the longitudinal direction of the patient recording area, the x-direction runs in the horizontal direction and is perpendicular to the z-direction, and the y-direction runs in the vertical direction and is perpendicular to the z-direction and perpendicular to the x-direction.To acquire the magnetic resonance data for determining the second patient size information, multiple slices are preferably excited in the z-direction, and magnetic resonance data from these multiple slices are acquired. In this way, a large overview image can be provided for determining a patient's position and thus also the patient's distance from the enclosure surrounding the patient receiving area, in particular the radio-frequency antenna unit. In addition, the acquisition of magnetic resonance data for determining the second patient size information may be carried out with a low resolution, in particular a lower spatial resolution, than the acquisition of medical and / or diagnostic magnetic resonance data and / or image data, so that the acquisition of the magnetic resonance data for determining the second patient size information can be carried out particularly quickly and in a time-saving manner.

[0030] In an advantageous development of the method according to the invention, it can be provided that the acquisition of the magnetic resonance data for determining the second item of patient size information is carried out for a region of the patient relevant for the magnetic resonance examination. The region of the patient relevant for the magnetic resonance examination is preferably arranged in the patient's FOV, so that a simple acquisition of the magnetic resonance data for determining the second item of patient size information can be achieved. In particular, this can also provide an exact position determination of the region to be examined within the FOV, and thus also the distance of the patient to the housing surrounding the patient receiving area, in particular the radio-frequency antenna unit, can be determined particularly precisely.

[0031] In an advantageous development of the method according to the invention, it can be provided that the acquisition of the magnetic resonance data for determining the second item of patient size information comprises an adjustment measurement and / or a localization measurement. A localization measurement and / or adjustment measurement preferably comprises a measurement and / or a scan with a low resolution, in particular a low spatial resolution, and is designed to localize the patient and / or their anatomy within the FOV. Due to the low resolution, such a measurement, in particular the adjustment measurement and / or the localization measurement, can be carried out in a particularly time-saving manner. In particular, such an adjustment measurement and / or localization measurement can be carried out in a particularly time-saving manner during measurement breaks between two scans and / or sequences for acquiring medical and / or diagnostic magnetic resonance data.

[0032] Alternatively or additionally, the magnetic resonance data for determining the second patient height information can be acquired together with medical and / or diagnostic magnetic resonance data. This eliminates the need for additional measurements and / or scans to acquire the magnetic resonance data for determining the second patient height information, thus providing the second patient height information in a particularly time-efficient manner.

[0033] In an advantageous development of the method according to the invention, it can be provided that the acquisition of the magnetic resonance data for determining the second item of patient height information is repeated at least once until the end of the magnetic resonance examination. Preferably, the acquisition of the magnetic resonance data for determining the second item of patient height information is repeated at regular intervals and / or during existing measurement breaks in the magnetic resonance examination. In particular, the acquisition of the magnetic resonance data for determining the second item of patient height information is carried out twice or more often.In this way, a continuous monitoring of the position of the patient and thus also a continuous correction in the determination of the distance of the patient to the housing surrounding the patient receiving area, in particular the radio-frequency antenna unit, can advantageously be carried out during the magnetic resonance examination, as is advantageous, for example, when the patient moves.

[0034] According to the invention, in order to determine the distance of the patient from the housing surrounding the patient receiving area, in particular the radio-frequency antenna unit, a body model of the patient is determined based on the first piece of patient size information and based on the second piece of patient size information. The body model is preferably created and / or determined from a partial area of ​​the patient arranged within the patient receiving area. The body model of the patient preferably comprises a contour and / or an outline and / or a surface of the partial area of ​​the patient arranged and / or located within the patient receiving area. The body model can comprise a 2D body model or a 3D body model. In particular, the second piece of size information, in particular the magnetic resonance image data, which is supplemented by the first piece of size information, can serve as the basis for the body model.For example, a visible inner arm boundary can be determined from the patient's first size information, in particular from the magnetic resonance image data, to which an arm diameter determined from the first size information can be added in order to obtain information about the patient's entire body and its outer contour. Using the body model, the distance between the patient and the enclosure surrounding the patient receiving area, in particular the radio-frequency antenna unit, can be determined and / or ascertained particularly precisely and quickly.

[0035] In an advantageous development of the method according to the invention, it can be provided that the determined distance of the patient from the housing surrounding the patient receiving area, in particular the radio-frequency antenna unit, is compared with a safety distance and, if the determined distance is smaller than the safety distance, at least one safety measure is carried out. The safety distance preferably comprises a minimum distance of the patient from the housing surrounding the patient receiving area, in particular the radio-frequency antenna unit. For example, the safety distance of the patient from the housing surrounding the patient receiving area, in particular the radio-frequency antenna unit, can be 5 mm. The at least one safety measure preferably comprises a reduction of the RF power during the magnetic resonance examination.This can, for example, lead to pauses after each measurement and / or to a reduction in the number of slices and / or a reduction in the flip angles, etc. In addition, the at least one safety measure can prevent the magnetic resonance examination from starting until the distance between the patient and the enclosure surrounding the patient admission area is greater than the safety distance. Alternatively or additionally, the at least one safety measure can also include a warning message and / or an instruction to the medical operating personnel, for example to reposition the patient. If, on the other hand, the safety distance between the patient and the enclosure surrounding the patient admission area, in particular the radio-frequency antenna unit, is maintained, the magnetic resonance examination can be performed as planned.In addition, at least one safety measure can be lifted again as soon as the distance between the patient and the enclosure surrounding the patient reception area is again greater than the safety distance.

[0036] Furthermore, the invention is based on a magnetic resonance device which is designed to carry out a method for determining a distance of a patient from a housing surrounding a patient receiving area during a magnetic resonance examination, comprising: a provision unit configured to provide first size information of the patient, a detection unit configured to detect magnetic resonance data to determine second size information of the patient, and a determination unit configured to determine a distance of the patient from the housing surrounding the patient receiving area, in particular the radio-frequency antenna unit.

[0037] The magnetic resonance device according to the invention has the advantage that it allows for precise determination of the distance between the patient and the enclosure surrounding the patient receiving area, in particular the radio-frequency antenna unit. Furthermore, this also provides a high level of patient safety during the magnetic resonance examination. Safety measures, such as limiting and / or reducing the RF power of the RF pulses to be delivered, can thus only be initiated when the distance between the patient and the enclosure surrounding the patient receiving area is actually below a threshold value, for example, less than 5 mm, thus avoiding unnecessary restrictions on the RF power during the magnetic resonance examination. This also makes it possible to avoid unnecessary restrictions on the RF transmission.

[0038] The advantages of the magnetic resonance device according to the invention essentially correspond to the advantages of the method according to the invention for determining a distance of a patient from a housing of a magnetic resonance device surrounding a patient receiving area during a magnetic resonance examination, which have been described in detail above. Features, advantages, or alternative embodiments mentioned herein can also be applied to the other claimed subject matter, and vice versa.

[0039] Furthermore, the invention is based on a computer program product comprising a computer program and / or control program and directly loadable into a memory of a programmable control unit, with program means for controlling a method for determining a distance of a patient from a housing of a magnetic resonance device surrounding a patient receiving area during a magnetic resonance examination when the computer program and / or control program is executed in the control unit. The computer program and / or control program may require program means, e.g., libraries and auxiliary functions, to implement the corresponding embodiments of the method.The computer program and / or control program can comprise software with source code that still needs to be compiled and linked or that only needs to be interpreted, or executable software code that only needs to be loaded into a corresponding computing unit for execution. The control unit must have the prerequisites, such as appropriate RAM, a corresponding graphics card, or a corresponding logic unit, so that the respective method steps can be carried out efficiently. The computer program product is stored, for example, on a computer-readable medium or on a network or server, from where it can be loaded into the processor of a local computing unit, which can be directly connected to the magnetic resonance device or formed as part of it. Furthermore, control information of the computer program product can be stored on an electronically readable data carrier.The control information of the electronically readable data carrier can be configured such that, when the data carrier is used in a computing unit, it executes the individual method steps of the method according to the invention and / or controls their execution. Thus, the computer program product can also represent the electronically readable data carrier. Examples of electronically readable data carriers are a DVD, a magnetic tape, a hard disk, or a USB stick on which electronically readable control information, in particular software (see above), is stored.

[0040] Further advantages, features and details of the invention will become apparent from the embodiment described below and from the drawings.

[0041] They show: Fig. 1 shows a magnetic resonance device according to the invention in a schematic representation, Fig. 2 shows a method according to the invention for determining a distance of a patient from a housing of a magnetic resonance device surrounding a patient receiving area during a magnetic resonance examination, and Fig. 3 shows a cross section through a patient receiving area of ​​the magnetic resonance device.

[0042] In Fig. 1 A magnetic resonance apparatus 10 is shown schematically. The magnetic resonance apparatus 10 comprises a scanner unit 11 formed by a magnet unit. In addition, the magnetic resonance apparatus 10 has a patient receiving area 12 for receiving a patient 13. The patient receiving area 12 in the present exemplary embodiment is cylindrical and is surrounded in a circumferential direction by the scanner unit 11, in particular by the magnet unit. The scanner unit 11 further has a housing 14 surrounding the patient receiving area 12. In principle, however, a different design of the patient receiving area 12 is conceivable at any time.

[0043] The patient 13 can be pushed and / or moved into the patient receiving area 12 by means of a patient support device 15 of the magnetic resonance device 10. For this purpose, the patient support device 15 has a patient table 16 designed to be movable within the patient receiving area 12. In particular, the patient table 16 is mounted so as to be movable in the direction of a longitudinal extent of the patient receiving area 12 and / or in the z-direction.

[0044] The scanner unit 11, in particular the magnet unit, comprises a superconducting base magnet 17 for generating a strong and in particular constant base magnetic field 18. Furthermore, the scanner unit 11, in particular the magnet unit, has a gradient coil unit 19 for generating magnetic field gradients that are used for spatial encoding during imaging. The gradient coil unit 19 is controlled by a gradient control unit 20 of the magnetic resonance device 10. The scanner unit 11, in particular the magnet unit, further comprises a radio-frequency antenna unit 21 for exciting a polarization that arises in the base magnetic field 18 generated by the base magnet 17.The radio-frequency antenna unit 21 is controlled by a radio-frequency antenna control unit 22 of the magnetic resonance device 10 and radiates radio-frequency magnetic resonance sequences into the patient receiving area 12 of the magnetic resonance device 10. The radio-frequency antenna unit 21 comprises the housing 14 surrounding the patient receiving area 12. In particular, the housing 14 surrounding the patient receiving area 12 comprises a side of the radio-frequency antenna unit 21 facing the patient receiving area 12.

[0045] The magnetic resonance apparatus 10 includes a system control unit 23 for controlling the base magnet 17, the gradient control unit 20, and the radio-frequency antenna control unit 22. The system control unit 23 centrally controls the magnetic resonance apparatus 10, such as performing a predetermined imaging gradient echo sequence. Furthermore, the system control unit 23 includes an evaluation unit (not shown in detail) for evaluating medical image data acquired during the magnetic resonance examination. The system control unit 23 also includes a storage unit 24, such as a database.

[0046] Furthermore, the magnetic resonance device 10 comprises a user interface 25 connected to the system control unit 23. Control information such as imaging parameters and reconstructed magnetic resonance images can be displayed on an output unit 26, for example, on at least one monitor, of the user interface 25 for medical personnel. Furthermore, the user interface 25 has an input unit 27, by means of which information and / or parameters can be entered by the medical personnel during a measurement process.

[0047] The magnetic resonance device 10 further comprises a camera 28, which is arranged on a ceiling 29 of an examination room in which the scanner unit 11 of the magnetic resonance device 10 is arranged. Alternatively, the camera 28 can also be arranged on a front side of the scanner unit 11. The camera 28 can comprise a 2D camera or a 3D camera. The patient 13 on the patient table 16 is captured by the camera 28. In particular, the patient 13 on the patient table 16 is captured by the camera 28 before being moved into the patient reception area 12.

[0048] The illustrated magnetic resonance apparatus 10 may, of course, include additional components that magnetic resonance apparatuses 10 typically have. A general mode of operation of a magnetic resonance apparatus 10 is also known to those skilled in the art, so a detailed description of the additional components is omitted.

[0049] In Fig. 2 A method according to the invention for determining a distance 30 of the patient 13 from the enclosure 14 surrounding the patient receiving area 12, in particular the radio-frequency antenna unit 21, during a magnetic resonance examination of the patient 13 is shown. The method is monitored and controlled by a control unit 31. The control unit 31 has the necessary computer programs and / or software, which are stored in a memory unit of the control unit 31. Furthermore, the control unit 31 has a processor configured to execute the computer programs and / or software.When the computer programs and / or software are executed by the processor of the control unit 31, the method for determining the distance 30 of the patient 13 to the enclosure 14 surrounding the patient receiving area 12, in particular the radio-frequency antenna unit 21, is started during the magnetic resonance examination of the patient 13 and controlled by the control unit 31. In the present exemplary embodiment, the control unit 31 is included in the system control unit 23 of the magnetic resonance apparatus 10. In addition, the control unit 31 can also be configured separately from the system control unit 23.

[0050] In a first method step 100, first size information of the patient 13 is provided, wherein the first size information of the patient 13 is provided before the start of the magnetic resonance examination. The first size information of the patient 13 preferably comprises an extent of the patient 13. In particular, the first size information of the patient 13 comprises a region in at least one spatial direction 33, wherein this region is arranged outside a field of view 32 of the magnetic resonance device 10 in the at least one spatial direction 33. Preferably, the at least one spatial direction 33 comprises a transverse direction of the patient table 16 of the patient support device 15. In particular, an extent of that region of the patient 13 in the transverse direction that is arranged within the patient receiving area 12 during the magnetic resonance examination is of importance here.In particular, the first size information of the patient 13 comprises size information and / or extent information and / or an outline of the patient 13 arranged outside the FOV 32 in the transverse direction of the patient table 16. For example, the first size information comprises a shape and / or a contour of the arms of the patient 13.

[0051] The first size information of the patient 13 can already be recorded and provided during patient registration. Furthermore, the first size information can already be stored in the storage unit 24 and / or a database, for example, in the case of first size information that was determined during a preliminary examination and / or a previous examination. Furthermore, the first size information can also be recorded and provided during preparation of the patient 13 for the magnetic resonance examination, for example by means of the camera 28. The first size information of the patient 13 is preferably provided by means of a provision unit 34 of the magnetic resonance device 10. The provision unit 34 can comprise the camera 28 and / or the database or the storage unit 24 and / or a registration unit and / or further units that appear appropriate to the person skilled in the art.The registration unit may, for example, comprise the control unit 31 and / or the system control unit 23.

[0052] In a second method step 101, magnetic resonance data of the patient 13 is acquired, wherein the acquisition of the magnetic resonance data is performed during the magnetic resonance examination of the patient 13. The acquisition of the magnetic resonance data for determining the second item of height information of the patient 13 is carried out by means of an acquisition unit 35 of the magnetic resonance device 10, wherein the acquisition unit 35 comprises the scanner unit 11. Based on the acquired magnetic resonance data, a second item of height information of the patient 13 is determined, wherein the determination of the second item of height information of the patient 13 is carried out by the control unit 31.

[0053] In order not to disrupt the magnetic resonance examination of patient 13, the magnetic resonance data for determining the second item of height information of patient 13 can be acquired during measurement pauses between individual radio-frequency pulses of the magnetic resonance examination. Preferably, the magnetic resonance data for determining the second item of height information of patient 13 is acquired with a maximum FOV 32 in order to cover the largest possible area of ​​patient 13 in the acquired magnetic resonance data. In particular, magnetic resonance data for determining the second item of height information of patient 13 is acquired from an area of ​​patient 13 relevant for the magnetic resonance examination. Acquiring the magnetic resonance data for determining the second item of height information of patient 13 includes an adjustment measurement and / or a localization measurement.Preferably, several slices are excited in the z-direction and magnetic resonance data of these several slices are acquired.

[0054] Alternatively, the acquisition of the magnetic resonance data for determining the second size information of the patient 13 may also include the acquisition of medical and / or diagnostic magnetic resonance data.

[0055] In a subsequent third method step 102, the distance 30 of the patient 13 to the enclosure 14 surrounding the patient receiving area 12, in particular the radio-frequency antenna unit 21, is determined based on the first size information of the patient 13 and the second size information of the patient 13. This third method step 103 is carried out by means of a determination unit of the magnetic resonance apparatus 10. In the present embodiment, the determination unit comprises the control unit 31.

[0056] In this third method step 102, the determination unit, in particular the control unit 31, determines the distance 30 of the patient 13 to the enclosure 14 surrounding the patient receiving area 12, in particular the radio-frequency antenna unit 21, using a body model, wherein the body model is determined and / or created based on the first size information of the patient 13 and based on the second size information of the patient 13. In this case, for example, an exact position of the patient 13 within the patient receiving area 12 is first determined using the second size information of the patient 13. Furthermore, for example, a body model for the partial area of ​​the patient 13 located within the FOV is created from the second size information of the patient 13, and this body model is supplemented with the partial areas of the patient 13 located outside the FOV 32 based on the first size information of the patient 13, see Fig. 3For example, a torso with a visible inner arm border can be provided using the second size information of the patient 13, and the arms can be added to complete the body model using the first size information of the patient. Based on the body model and the position of the patient 13 within the patient receiving area 12, the determination unit, in particular the control unit 31, then determines and / or calculates the distance 30 of the patient 13 to the enclosure 14 surrounding the patient receiving area 12, in particular the radio-frequency antenna unit 21.

[0057] Subsequently, in a fourth, in particular optional, method step 103, the determined distance 30 of the patient 13 to the housing 14 surrounding the patient receiving area 12, in particular the radio-frequency antenna unit 21, is compared with a safety distance. If the determined distance 30 is smaller than the safety distance, a safety measure is initiated and / or carried out by the determination unit, in particular the control unit 31, in this fourth method step 103. For example, the safety distance is 5 mm. If the distance 30 of the patient 13 to the housing 14 surrounding the patient receiving area 12, in particular the radio-frequency antenna unit 21, is smaller, this can lead to undesired injuries, in particular burns, to the patient 13. A safety measure can, for example, be that an RF power of RF pulses to be played out from the radio-frequency antenna unit 21 is reduced.This may, for example, lead to pauses after each measurement and / or to a reduction in the number of slices and / or a reduction in the flip angles, etc.

[0058] If, however, the distance of the patient 13 to the enclosure 14 surrounding the patient receiving area 12, in particular the radio-frequency antenna unit 21, is greater than the safety distance, the magnetic resonance examination will continue to be carried out with the original settings as planned.

[0059] During the magnetic resonance examination of patient 13, the second to fourth method steps 101, 102, 103 are repeated at least once until the magnetic resonance examination is completed. Preferably, the second to fourth method steps 102, 103, 104 are repeated several times by the control unit 31 in order to regularly detect and monitor changes in the position of patient 13 and thus also a change in the distance 30 of patient 13 from the enclosure 14 surrounding the patient receiving area 12, in particular the radio-frequency antenna unit 21.

[0060] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited to the disclosed examples and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims

1. Method for ascertaining a distance between a patient and an enclosure, which surrounds a patient receiving region, of a magnetic resonance apparatus during a magnetic resonance examination, comprising the following method steps: - providing a first item of size information of the patient, wherein the first size information is provided before starting the magnetic resonance examination, - capturing magnetic resonance data of the patient during the magnetic resonance examination and determining a second item of size information of the patient on the basis of the captured magnetic resonance data, and - ascertaining the distance between the patient and the enclosure surrounding the patient receiving region on the basis of the first size information of the patient and on the basis of the second size information of the patient, wherein, in order to determine the distance between the patient and the enclosure surrounding the patient receiving region, a body model of the patient is determined on the basis of the first size information and on the basis of the second size information, from a subregion of the patient arranged within the patient receiving region.

2. Method according to claim 1, characterised in that the first size information is provided by means of a camera.

3. Method according to one of the preceding claims, characterised in that the first size information is provided by means of a database and / or a patient registration.

4. Method according to one of the preceding claims, characterised in that the first size information comprises a region in at least one spatial direction, wherein this region in the at least one spatial direction is arranged outside the FOV of the magnetic resonance apparatus.

5. Method according to one of the preceding claims, characterised in that the capturing of magnetic resonance data for determining the second size information of the patient is performed with a maximum FOV.

6. Method according to one of the preceding claims, characterised in that the capturing of the magnetic resonance data for determining the second size information of the patient is performed for a region of the patient that is relevant to the magnetic resonance examination.

7. Method according to one of the preceding claims, characterised in that the capturing of the magnetic resonance data for determining the second size information of the patient comprises an adjustment measurement and / or a localiser measurement.

8. Method according to one of the preceding claims, characterised in that the capturing of the magnetic resonance data for determining the second size information of the patient is repeated at least once until the conclusion of the magnetic resonance examination.

9. Method according to one of the preceding claims, characterised in that the ascertained distance between the patient and the enclosure surrounding the patient receiving region is compared with a safety distance, and, if the ascertained distance is smaller than the safety distance, at least one safety measure is performed.

10. Magnetic resonance apparatus, which is embodied to carry out the method for determining a distance between a patient and an enclosure surrounding a patient receiving region, in particular a radiofrequency antenna unit, during a magnetic resonance examination according to one of claims 1 to 9, comprising: - a provision unit, which is embodied to provide a first item of size information of the patient, - a capture unit, which is embodied to capture magnetic resonance data for determining a second item of size information of the patient, and - an ascertaining unit, which is embodied to ascertain a distance of the patient from the enclosure surrounding the patient receiving region.

11. Computer program product, which comprises a control program and can be loaded directly into a memory of a programmable control unit, with program means in order to control a method for determining a distance between a patient and an enclosure surrounding a patient receiving region during a magnetic resonance examination according to one of claims 1 to 9, when the program is executed in the control unit.