Magnetic resonance imaging device with patient positioning device

Abstract

The magnetic resonance imaging (MRI) device comprises a magnet unit, a patient table, and a patient position detection device. The magnet unit surrounds a patient acquisition area defined by an inner wall of the magnet unit and includes a whole-body coil. The patient table is movable within the patient acquisition area. The patient position detection device comprises a sensor unit, a determination unit, and a verification unit. The sensor unit is designed to determine the patient's position on the patient table. The determination unit is designed to determine the distance between the patient and the inner wall based on this position information. The verification unit is designed to check the patient's positioning against a distance limit based on this distance.

Description

[0001] The invention relates to a magnetic resonance device comprising a patient position determination device. Furthermore, the invention relates to a method for checking whether a patient's position complies with a distance limit value in a magnetic resonance device.

[0002] In a magnetic resonance imaging (MRI) scan of a patient, magnetic resonance tomography (MRI) is performed. Magnetic fields, particularly gradient fields, and radio frequency signals or fields are typically used to acquire magnetic resonance signals via a magnetic resonance device, according to a measurement protocol. To generate the gradient fields, a magnetic resonance device usually includes a gradient coil unit. Furthermore, the magnetic resonance device typically includes a radio frequency antenna unit, which can generate the radio frequency (RF) signals to excite atomic nuclei. The gradient coil unit, the radio frequency antenna unit, and a main magnet are typically enclosed within a magnet unit of the magnetic resonance device.A patient acquisition area (also called examination area) is typically located in a magnetic bore of the magnet unit, where a patient is positioned on a patient table during the magnetic resonance imaging (MRI) scan. The typically tubular magnetic bore of the magnet unit, encompassing the patient acquisition area, can also be referred to as the patient tunnel.

[0003] In magnetic resonance imaging (MRI), radiofrequency signals (or radiofrequency transmission fields) are generated by a high-power amplifier and then applied to the patient using a whole-body coil. The whole-body coil, which is permanently integrated into the MRI scanner, typically has transmitting antennas located directly behind an inner wall of a magnetic opening in the scanner.

[0004] The high-power amplifier and whole-body coil are enclosed within the high-frequency antenna unit. The high-frequency signals interact with human tissue. The eddy currents induced in the tissue generate heat, leading to a temperature increase. The absorbed power can be described as the specific absorption rate (SAR) in W / kg. The SAR value or parameter typically indicates the amount of energy absorbed by a patient during a magnetic resonance imaging (MRI) scan. A high SAR value results in excessive, intense heating of the tissue and can cause damage to the patient's body.

[0005] Typically, safety measures to ensure patient safety during magnetic resonance imaging (MRI) scans are based on international standards such as IEC 60601-1 and IEC 60601-2-33. These safety measures include, in particular, limiting the specific absorption rate (SAR) during the MRI scan. Especially in the immediate vicinity of the transmitting antennas of the whole-body coil, local intensity maxima of the radiofrequency signals can occur, which in the worst case can cause burns to the patient.

[0006] To prevent burns from overheating, patients are instructed not to touch the inner wall of the magnet unit. The inner wall of the magnet unit typically comprises a 5-15 mm thin plastic layer (in the form of a tube). The inner wall of the magnet unit is typically located between the whole-body coil and the patient acquisition area. Preferably, the inner wall of the magnet unit defines the boundaries of the patient acquisition area, particularly in the radial direction. However, even if the patient does not directly touch the inner wall of the magnet unit, the electromagnetic radiation from the high-frequency signals can be very high in the vicinity of the inner wall. Therefore, compliance with the SAR values ​​in this area must be ensured by contact protection.The transmission power of the transmitting antennas is limited based on the assumption that tissue is located at a critical distance (e.g., <50 mm) from the inner wall of the magnetic unit. However, the touch protection (also known as SAR contact protection) may be too conservative in many applications, as in many cases, e.g., with slim or average-sized patients who are properly positioned on the table, no tissue is located in the critical area.

[0007] The object of the present invention is to increase the performance of the magnetic resonance imaging (MRI) device during a patient's MRI scan while simultaneously adhering to the SAR limits. This object is achieved by the features of the independent claims. Advantageous embodiments are described in the dependent claims.

[0008] According to the invention, a magnetic resonance device comprising a magnetic unit, a patient table, and a patient position determination device is proposed. The magnetic unit surrounds a patient acquisition area bounded by an inner wall of the magnetic unit and includes a whole-body coil. The patient table is designed to be movable within the patient acquisition area. The patient position determination device comprises a sensor unit, a determination unit, and a testing unit. The sensor unit is configured to determine the position of a patient on the patient table. The determination unit is configured to determine the distance between the patient and the inner wall of the magnetic unit based on this position information. The testing unit is configured to check the patient's positioning for compliance with a distance limit value based on this distance.

[0009] During a magnetic resonance imaging (MRI) scan, the patient is typically wholly or partially located within the patient acquisition area. Specifically, the patient may be positioned on a patient support surface of the patient table. The patient acquisition area is surrounded, in particular, by the inner wall of the magnetic unit, specifically by a magnetic port of the magnetic unit. The elongated extension of the patient acquisition area bounded by the magnetic port can also be referred to as the patient tunnel. Specifically, the portion of the patient from which imaging and / or spectroscopic magnetic resonance signals are to be acquired by the MRI scanner is positioned within the magnetic port. In particular, at least a portion of the patient is positioned at an isocenter of the MRI scanner, specifically within a main magnetic field.Preferably, the main magnetic field, and in particular its strength, exhibits particularly high homogeneity at the isocenter. During magnetic resonance imaging (MRI), the application of high-frequency transmission pulses typically generates high-frequency fields that deflect nuclear spins in the patient from their resting position. Subsequent relaxation of these spins produces imaging and / or spectroscopic MRI signals, which are received by one or more receiving antennas of the MRI scanner and can be used for reconstructing MRI images or for spectroscopy.

[0010] Preferably, the patient acquisition area is cylindrical and / or tunnel-shaped and / or tubular. To generate imaging and / or spectroscopic magnetic resonance signals during a magnetic resonance examination, high-frequency transmission pulses are emitted into the patient acquisition area, and in particular into the patient, using one or more transmitting antennas, according to a measurement protocol, in particular a magnetic resonance sequence. Preferably, the patient acquisition area (or the magnet opening) is bounded by an inner wall. In particular, the magnet unit can comprise a boundary and / or a housing element, in particular an inner wall. Preferably, the inner wall is located between a patient acquisition area, in which at least part of the patient is positioned, and the whole-body coil of the magnet unit.In particular, the whole-body coil, which is rigidly integrated into a magnetic unit of the magnetic resonance device, comprises at least one receiving antenna and / or one transmitting antenna. Preferably, the magnetic unit surrounds the patient acquisition area and / or delimits the magnetic opening. The magnetic unit may, in particular, comprise a housing element, especially an outer wall, which separates the magnetic unit, especially its end faces, from the surrounding environment and / or surrounds the magnetic unit.

[0011] Preferably, a patient positioning device, in particular the patient table, can be moved into the patient reception area. The patient table can preferably accommodate a horizontally lying patient. The patient table can include electronic components and connections that, for example, enable a change in position (in particular a movement) of the patient table.

[0012] The patient position determination device is, in particular, a device for determining and verifying the positioning of a patient on a patient table during a magnetic resonance imaging (MRI) examination. The patient position determination device comprises, in particular, three subcomponents: a sensor unit, a determination unit, and a verification unit.

[0013] The sensor unit is specifically designed to determine at least one piece of positional information about the patient on the patient table within the patient acquisition area. The sensor unit may comprise one or more sensors for determining the positional information. The sensor unit and / or the sensors of the sensor unit may be arranged, in particular, within the patient acquisition area, especially on or in the inner wall of the magnetic unit. The sensor unit and / or the sensors of the sensor unit may be arranged, in particular, outside the patient acquisition area, especially on an end face and / or a housing element of the magnetic unit. The sensor unit and / or the sensors of the sensor unit may be arranged, in particular, at and / or relative to a reference point, for example, the center of the magnetic opening or a predetermined point on the inner wall of the magnetic unit.

[0014] The determination unit is specifically designed to determine the patient distance between the patient and the inner wall of the magnetic unit, particularly the inner wall of the magnetic opening of the magnetic unit, based on the positional information. The determination unit can preferably be included by a control unit of the magnetic resonance device, which is designed to control the execution of the magnetic resonance examination. The determination unit can preferably be included by the examination unit. The determination unit can, in particular, include one or more processors and / or one or more memory modules designed to process and store the positional information. The determination unit can also be designed to provide and / or display the determined positional information, for example, on a monitor or display unit.

[0015] The test unit is specifically designed to check the patient's positioning for compliance with a distance limit based on the patient's distance. The distance limit can be, in particular, a predetermined threshold specifying how close the patient may be positioned to the magnet unit without exceeding the specific absorption rate (SAR). The test unit can, for example, be configured to issue a warning or initiate an adjustment of the patient's positioning via a control signal if the patient's distance falls below and / or exceeds the distance limit. Specifically, the test unit can be configured to generate a control signal based on the position information, which may be suitable for adjusting the patient's position on the table and / or stopping the magnetic resonance imaging (MRI) scan.

[0016] Preferably, the position information can describe the (ideally actual) spatial position of the patient, in particular a part of the patient's body, on the patient table. Preferably, the position information can include a three-dimensional and / or two-dimensional description (in x and y) of a point, in particular a center point and / or a point on a surface, of the body part. This description can be relative to a reference object, in particular a reference point (especially by means of a coordinate system). The reference point (e.g., the origin of the coordinate system) is preferably the center point of the magnet opening and / or a predetermined point on the inner wall of the magnet unit. The patient's distance can be determined, for example, by the determination unit evaluating position information, in particular a signal strength or a signal propagation time of a sensor signal.

[0017] The patient distance is preferably a measure of a spatial distance, in particular a minimum spatial distance, between the patient, especially a part of the patient's body, and the inner wall of the magnetic opening of the magnetic unit. Advantageously, the patient distance can be determined by the measuring unit based on the patient's position information on the patient table.

[0018] Advantageously, the magnetic resonance imaging device according to the invention, which includes the patient positioning device, enables increased examination safety, improved image quality, and increased efficiency of the magnetic resonance examination. This can be achieved in particular because the patient positioning device allows for optimal positioning of the patient relative to the magnetic field, monitoring and control of the distance between the patient and the inner wall, especially the magnet opening and the magnet unit, as well as quick and precise adjustment of the patient table position. This reduces the risk of unwanted heating and / or tissue burns caused by electromagnetic radiation.

[0019] According to one possible aspect of the invention, the sensor unit comprises a distance sensor for detecting position information. The magnetic unit of the magnetic resonance device preferably includes the distance sensor. In particular, the inner wall of the magnetic opening of the magnetic unit of the magnetic resonance device can include the distance sensor.

[0020] The distance sensor can, in particular, comprise a sensor and the measuring unit. The distance sensor can, in particular, be configured to measure a spatial distance, especially the patient distance, between the sensor and a patient, especially a part of the patient's body. The distance sensor can, for example, be configured to acquire distance data using ultrasound, induction, capacitive, and / or optical methods. The distance sensor can be mounted at various locations on the magnetic resonance device, e.g., on the inner wall of the magnet unit, on the outer wall of the magnet unit, or on the patient table. The distance sensor can, in particular, be electronically connected to the testing unit in order to use the determined distance data, especially the patient distance, to check whether the patient's positioning complies with a distance limit value.

[0021] The distance sensor can, in particular, comprise a distance and / or proximity sensor. The distance sensor can also, for example, include a proximity sensor. Furthermore, the distance sensor can be configured, in particular, to measure and / or detect the presence of an object under investigation, especially a patient and / or a patient limb and / or a patient's tissue, within a certain distance. Moreover, the distance sensor can be configured, in particular, to quantitatively measure the distance between the distance sensor and the tissue, especially a body part, of the patient. Preferably, the distance sensor is configured to distinguish between human tissue and padding, coils, and / or the like, in particular by determining the number of protons in the object to be detected.

[0022] The use of one or more distance sensors as a sensor unit can contribute to increased patient safety and examination efficiency during magnetic resonance imaging (MRI) scans. These sensors can advantageously enable optimal patient positioning relative to the magnetic field while simultaneously ensuring a defined minimum distance to the inner wall of the magnetic unit. For example, an MRI device incorporating a distance sensor can allow for precise and rapid alignment of the patient table. This can also benefit from reducing the risk of unintended heating or burns to the patient's tissue caused by electromagnetic radiation.

[0023] According to one possible aspect of the invention, the sensor unit comprises an ultrasonic sensor.

[0024] In particular, the distance sensor can be designed as an ultrasonic sensor.

[0025] An ultrasonic sensor is typically a sensor that emits and receives sound waves in the ultrasonic range (above 20 kHz) to determine the distance to an object. The ultrasonic sensor might, for example, include a piezoelectric element that vibrates when an electrical voltage is applied, generating ultrasonic waves. When these ultrasonic waves encounter an object, they are partially reflected and can be received again by the ultrasonic sensor. The travel time of the waves typically depends on the distance between the sensor and the object. By measuring this travel time, the distance between the object and the ultrasonic sensor can be calculated.

[0026] The ultrasonic sensor can, in particular, measure the transit time and / or phase of reflected sound waves to determine position information. The ultrasonic sensor can, in particular, be mounted on the inner wall of the magnetic unit and / or on, in particular, an outer wall of the magnetic unit. The ultrasonic sensor can, for example, be configured to detect the distance between the sensor and the patient's tissue and / or the surface of a part of the patient's body, especially when the patient is in close proximity to the ultrasonic sensor. The ultrasonic sensor can, in particular, be configured to transmit the measurement data to the target unit and / or a control unit in order to calculate the position information, in particular from the transit time data, and to adjust the magnetic resonance device accordingly.

[0027] An ultrasonic sensor offers the advantage of precise, robust, and reliable distance measurement, particularly in determining positional information. Ultrasonic sensors are typically unaffected by electromagnetic fields and therefore do not cause interference or artifacts in the image data. Furthermore, ultrasonic sensors enable rapid and non-contact measurement of distance, and especially positional information, between the patient and the inner wall, particularly the magnet opening, of the magnetic unit, without requiring direct tissue contact and / or the use of additional equipment. An ultrasonic sensor can also achieve high accuracy and reliability in distance measurement, particularly in determining positional information, especially when the patient's tissue has good acoustic impedance.Furthermore, ultrasonic sensors are typically inexpensive and easy to install, which in turn can simplify the maintenance of the magnetic resonance device.

[0028] According to one possible aspect of the invention, the sensor unit comprises an inductive sensor.

[0029] In particular, the distance sensor can be designed as an inductive sensor.

[0030] An inductive sensor is typically a sensor that generates an alternating magnetic field and measures changes in the magnetic field caused by the presence of an object, particularly a metallic one, in order to determine the distance to that object. The inductive sensor may, for example, comprise a coil through which an electric current flows, generating a magnetic field. Particularly when the object is positioned near the sensor, a change in the magnetic field can occur, leading to a change in the coil's inductance. By measuring this change, positional information, especially the distance between the object and the inductive sensor, can be determined and / or calculated.

[0031] The inductive sensor can, in particular, measure the change in voltage, current, and / or frequency in the coil to determine position information. The inductive sensor can, in particular, be mounted on the inner wall of the magnetic unit and / or on, in particular, an outer wall of the magnetic unit. The inductive sensor can, for example, be configured to detect the distance between the sensor and a surface of a patient's body part, especially if the surface of the body part is equipped with a detection element, such as a metallic patch or the like. The inductive sensor can, in particular, be configured to transmit the measurement data, especially the position information, to the determining unit in order to determine the patient's distance, in particular from the inductance data determined by the inductive sensor.

[0032] An inductive sensor as a sensor unit advantageously enables simple, fast and contactless distance measurement, especially the determination of position information.

[0033] In particular, an inductive sensor is typically insensitive to environmental influences such as dirt, dust, humidity, or temperature. Furthermore, an inductive sensor can achieve high resolution and accuracy in distance measurement, especially if the object being detected, particularly patient tissue, has a sufficient metal content. In addition, inductive sensors are typically compact, robust, and durable.

[0034] According to one possible aspect of the invention, the sensor unit comprises a capacitive sensor.

[0035] In particular, the distance sensor can be designed as a capacitive sensor.

[0036] A capacitive sensor is typically a sensor that measures the capacitance of an electrical capacitor whose plates are separated by a dielectric. The capacitive sensor can, for example, consist of two parallel plates, particularly metal plates, to which a constant voltage is applied. The capacitance between the plates is specifically influenced by the size of the plates, the distance between them, and the dielectric material. If an object, particularly patient tissue, is located near the sensor, this can cause a change in the dielectric and thus a change in capacitance. By measuring this change in capacitance, the distance between the object and the capacitive sensor can be determined.

[0037] The capacitive sensor can, in particular, measure the change in voltage across the capacitor plates to determine position information. The capacitive sensor can be mounted, in particular, on the inner wall of the magnet unit, especially the inner wall of the magnet opening of the magnet unit, and / or on the magnet unit itself, especially on an outer wall. The capacitive sensor can, for example, be configured to detect the distance, in particular the position information, between the sensor and a surface of a body part of the patient, especially without the use of additional equipment. The capacitive sensor can, in particular, be configured to transmit the measurement data, in particular position information, to the determining unit in order to calculate the patient distance, in particular from the capacitance data.

[0038] A capacitive sensor offers the advantage of contactless, hygienic, and non-contact distance measurement, particularly for determining positional information. Specifically, a capacitive sensor can achieve high resolution and accuracy in distance measurement, especially when the object being detected, particularly patient tissue, has a high dielectric constant. Furthermore, a capacitive sensor can exhibit low power consumption and low heat output, which in turn can extend the lifespan of the magnetic resonance imaging (MRI) device. In addition, capacitive sensors are typically easy to design, calibrate, and integrate.

[0039] According to one possible aspect of the invention, the sensor unit comprises a pressure sensor.

[0040] A pressure sensor is typically a sensor designed to detect a force acting on a surface. The pressure sensor may, for example, comprise a membrane that deforms under the influence of pressure. By measuring this deformation, it is possible, in particular, to detect contact with the sensor by the patient. The pressure sensor may be attached to the inner wall of the magnetic unit and / or to the magnetic unit itself. The pressure sensor may, for example, be designed to detect the pressure exerted by a part of the patient's body on the inner wall of the magnetic unit, in particular the inner wall of the magnetic opening of the magnetic unit. The pressure sensor may, in particular, be designed to transmit the measurement data, especially position information, to the determining unit in order to calculate the patient's distance, in particular from the detected pressure data.

[0041] A pressure sensor offers the advantage of simple, robust, and cost-effective distance measurement. In particular, a pressure sensor can achieve high sensitivity and reliability in pressure measurement, especially when the object being measured, particularly a patient, exerts high pressure on the inner wall. Furthermore, a pressure sensor can exhibit low susceptibility to electromagnetic interference, thus potentially improving the accuracy of magnetic resonance imaging (MRI). In addition, pressure sensors are typically compact, lightweight, and require little maintenance.

[0042] According to one possible aspect of the invention, the sensor unit comprises an optical sensor. In particular, the optical sensor comprises a camera.

[0043] In particular, the distance sensor can be designed as an optical sensor.

[0044] An optical sensor is typically a sensor designed to measure the optical properties of an object and / or to determine a distance, in particular positional information, between the object and the sensor. The optical sensor may, for example, include a camera designed to capture image and / or video data of a patient, in particular a part of the patient's body. The optical sensor may, for example, include a laser distance sensor designed to emit laser light and detect laser light reflected from the patient, in particular a part of the patient's body. By evaluating images or videos captured by the optical sensor as positional information, a distance, in particular the patient's distance, between the body part and the inner wall of the magnetic unit, in particular the inner wall of the magnetic opening of the magnetic unit, can be determined by the measuring unit.The optical sensor can, for example, be configured to detect distance, particularly positional information, by detecting and / or analyzing the size, shape, color, texture, or other characteristics of the body part. The optical sensor can, in particular, be configured to transmit the measurement data, especially positional information, to the determining unit in order to calculate the patient distance, specifically based on the acquired image data.

[0045] An optical sensor offers the advantage of non-contact, hygienic, and contactless distance measurement. In particular, an optical sensor can achieve high resolution and accuracy in distance measurement, especially when the object being detected, particularly patient tissue, has high optical contrast. Furthermore, an optical sensor exhibits low susceptibility to electromagnetic interference, which in turn can improve the accuracy of magnetic resonance imaging. In addition, optical sensors are typically flexible, versatile, and easy to integrate.

[0046] According to one possible aspect of the invention, the sensor unit is arranged at a position on the inner wall of the magnet unit, in particular the magnet opening of the magnet unit, where a local field strength of the body coil exceeds a threshold value.

[0047] The local field strength of the body coil is characterized in particular by the intensity of the local field, especially an RF field, generated by the body coil at a specific point on the inner wall of the magnet unit, specifically the magnet opening of the magnet unit. The local field strength can vary depending on the shape, size, and number of turns of the body coil, as well as its distance from the center of the body coil. The position and / or area of ​​maximum local field strength corresponds in particular to an area on the inner wall of the magnet unit where the potential danger to the patient from contact with the inner wall of the magnet unit, especially the inner wall of the magnet opening of the magnet unit, is highest.It is known that with increasing local field strength, the potential risk of overheating or burning of the patient upon contact with the inner wall of the magnet unit, especially the inner wall of the magnet opening of the magnet unit, also increases.

[0048] The threshold value, in particular, defines a limit for the local field strength that should not be exceeded to avoid potential harm to the patient. The threshold value can be set, for example, based on the specific absorption rate (SAR), which describes the power absorbed per unit volume of tissue. The threshold value can also depend on factors such as the frequency of the magnetic resonance imaging (MRI), the type of tissue, and the duration of exposure. The threshold value can be defined, for example, as a constant value, a relative value, or a functional value.

[0049] Positioning the sensor unit at the point of maximum local field strength of the body coil is particularly advantageous for measuring the distance, and especially the positional information, between the patient and the inner wall at the point where the greatest risk of injury to the patient exists. By arranging the sensor unit specifically in this position, patient safety can be advantageously improved by enabling precise distance measurement at this point and preventing potential overheating or burns.

[0050] According to one possible aspect of the invention, the sensor unit comprises a sensor. The sensor is arranged outside the patient reception area, in particular on an end face of the magnetic unit. The sensor unit particularly comprises an optical sensor.

[0051] The sensor can be attached, for example, to an outer wall and / or end face of the magnetic unit or at one end of the patient tunnel. The sensor unit comprises, in particular, an optical sensor in the form of a camera and / or a camera system. The sensor, in particular the camera system, can be configured to determine and / or monitor the distance, in particular the positional information, between the patient and the inner wall of the magnetic unit from a position outside the patient's field of view. This can be achieved, for example, by two sensors, in particular cameras, arranged along a z-direction, in particular the cylinder axis of the magnetic unit, or at a shallow angle along the z-direction, in particular the cylinder axis of the magnetic unit, and configured to capture a field of view within the patient's field of view.In particular, a first sensor of the sensor unit can be arranged on and / or at a first end face of the magnet unit, and a second sensor of the sensor unit can be arranged on and / or at a second, in particular opposite, end face of the magnet unit. In particular, the sensor unit can be configured to determine a patient's position, in particular position information, on the patient table, especially before the patient is moved into the patient admission area (or when the patient is positioned on the patient table outside the patient admission area).

[0052] Positioning the sensor unit outside the patient reception area, particularly outside the magnetic opening of the magnet unit, ensures that the sensor is not affected or disturbed by the magnetic field of the body coil. Furthermore, positioning the sensor unit outside the patient reception area can advantageously increase the accuracy and reliability of the distance measurement between the patient and the inner wall of the magnet unit's opening by avoiding potential distortion or reflection of the optical radiation by the magnetic field of the body coil.

[0053] According to one possible aspect of the invention, the sensor unit comprises a transmitter and a receiver. The transmitter of the sensor unit is arranged at a first opening of the magnetic unit, in particular at a first end face of the magnetic unit. The receiver of the sensor device is arranged at a second opening of the magnetic unit, in particular at a first end face of the magnetic unit. The transmitter of the sensor unit is configured to emit electromagnetic radiation. The receiver is configured to receive the electromagnetic radiation.

[0054] The sensor unit comprises a transmitter and a receiver, preferably arranged opposite each other at opposite openings of the magnetic unit. In particular, the transmitter and receiver can be arranged on the front face of the magnetic unit, especially on a housing unit, particularly an outer surface of the magnetic unit. The transmitter is configured to emit electromagnetic radiation that does not penetrate the patient within the patient reception area. The receiver is configured to receive electromagnetic radiation that is not absorbed by the patient and / or is reflected or scattered by the patient. The intensity and / or position of the received radiation can be dependent on the distance between the patient and the inner wall of the magnetic unit.The determination unit can be designed in particular to determine the distance, especially the patient distance, between the patient and the inner wall of the magnetic unit based on the intensity and / or spatial position / orientation of the received radiation.

[0055] The transmitter can emit infrared, ultrasound, or radar waves, which can be reflected or absorbed by the patient. The receiver can, in particular, receive the reflected waves and / or the unabsorbed waves and determine the patient's position based on the travel time, intensity, or frequency change of the received waves.

[0056] In particular, the transmitter can be configured to emit a laser beam. In particular, the receiver can be configured to receive a laser beam. The sensor unit can be configured, by means of the transmitter and receiver, to generate a laser beam covering a line, area, and / or region of the inner wall of the magnetic unit. In other words, the sensor unit can function like a light barrier by means of the transmitter and receiver.

[0057] A sensor unit comprising a transmitter and a receiver can advantageously improve the determination of the patient's position within the patient acquisition area. The transmitter can, in particular, generate electromagnetic radiation that partially or completely covers the inner wall of the magnetic unit. The receiver can, in particular, detect the radiation reflected or scattered by the patient. This allows the sensor unit to determine the distance between the patient and the inner wall of the magnetic unit, especially in critical areas where contact with the inner wall by the patient is possible. This type of position determination can be independent of ambient lighting or contrast.

[0058] According to one possible aspect of the invention, a first sensor of the sensor unit is arranged outside the patient reception area on the magnetic unit. A second sensor of the sensor unit is arranged inside the patient reception area on the magnetic unit.

[0059] The sensor unit may include additional sensors located outside the patient detection area and / or additional sensors located within the patient detection area. The first sensor is specifically designed to record the patient's position within a first area. The second sensor is specifically designed to record the patient's position within a second area. The first area is, in particular, larger than the second area. For example, the first area may encompass the entire patient detection area. The second area may, for example, comprise a predetermined sub-area of ​​the patient detection area, such as an interior wall section, where contact by the patient within the patient detection area is possible, particularly in a sub-area where, in particular, a patient limb is located.The determining unit can be configured, in particular, to determine the distance between the patient and the inner wall of the magnetic unit based on the position information from the sensors of the sensor unit, especially the first and second sensors. The determining unit can, for example, be configured to determine the patient distance by comparing or combining the position information.

[0060] Advantageously, arranging a first sensor outside and a second sensor inside the patient acquisition area enables comprehensive and accurate acquisition of positional information and / or determination of the patient's distance. This arrangement can also allow for sensor redundancy, i.e., different data sources for positional information. In particular, positional information from various perspectives, angles, and / or positions can be supplied to the determination unit. The described arrangement of two or more sensors can also increase the robustness and reliability of the patient distance determination, for example, by compensating for and / or reducing potential disturbances or distortions caused by the magnetic field of the body coil and / or other environmental factors.

[0061] According to one possible aspect of the invention, the sensor unit comprises a motion sensor. The motion sensor is configured to detect movement information from the patient. The determination unit is configured to determine the distance between the patient and the inner wall of the magnetic unit based on this movement information.

[0062] In particular, position information can include movement information. In particular, movement information can include position information.

[0063] The motion sensor is specifically designed to detect the patient's movement within the patient acquisition area. The motion sensor may, for example, comprise an infrared sensor, an ultrasonic sensor, or a laser beam sensor. The motion sensor may be configured to transmit motion information to the determination unit. The determination unit may, for example, be configured to calculate the distance between the patient and the inner wall of the magnetic unit, specifically the patient distance, based on the motion information and initial position information of the patient. The motion sensor may be arranged, in particular, within the patient acquisition area, specifically on / in the inner wall of the magnetic unit. Alternatively, the motion sensor may be arranged, in particular, outside the patient acquisition area, specifically at an opening in the magnetic unit.The determination unit can be specifically configured to determine position information based on motion information. The motion sensor can be specifically configured to acquire one and / or more position information, particularly information acquired at different times. The determination unit can be specifically configured to determine motion information from one and / or more position information. In particular, the testing unit can be configured to test the motion information. In particular, the testing unit can be configured to output a warning and / or control signal when patient movement is detected. In particular, the testing unit can be configured to test the motion information against a threshold value for the motion information.

[0064] A motion sensor offers the advantage of continuous monitoring of the patient's position. This sensor can detect critical patient movements, particularly before direct contact occurs between the patient and the inner wall of the magnetic unit. Furthermore, the motion sensor can be configured to detect patient movement during imaging and trigger appropriate warnings or corrections.

[0065] According to one possible aspect of the invention, the magnetic resonance device comprises a patient posture detection unit. The patient posture detection unit is configured to detect the patient's posture on the patient table. The testing unit is configured to check the patient's posture against a predetermined position.

[0066] The patient posture detection unit is specifically designed to detect the patient's posture, orientation, and / or shape on the treatment table. The patient posture detection unit may include, for example, a camera, an infrared sensor, a 3D scanner, or a combination of sensors.

[0067] The patient posture detection unit can be trained to record the patient's posture on the examination table, specifically the orientation and position of body parts such as the head, arms, legs, or torso. The patient posture detection unit can be trained to send posture information to the verification unit. The verification unit can, for example, be trained to use this posture information to check whether the patient is assuming a predetermined posture.

[0068] A predetermined posture may, in particular, be a patient posture that could increase or cause contact with the inner wall of the magnetic unit. The critical posture may, for example, include lateral tilting, extension, and / or angulation of a body part. The test unit may be configured to store a plurality of predetermined postures, in particular in a database, especially one included in the test device. The test unit may, in particular, be configured to compare the detected patient posture with the plurality of stored predetermined postures. The test unit may, in particular, be configured to output a warning and / or control signal when the patient posture is detected and / or verified as a predetermined posture.

[0069] A patient posture detection unit offers the advantage of early detection of potentially hazardous patient postures and / or potentially dangerous situations. The unit can trigger a warning or a correction of the patient's position before they touch the inner wall of the magnetic unit. It can also prevent or reduce contact between the patient and the magnetic unit's inner wall, for example, by stopping, adjusting, or retracting the patient table. Furthermore, the unit can enhance patient safety by calculating the specific absorption rate (SAR) for the patient based on their posture, particularly based on posture information, and verifying it against a predefined SAR limit.

[0070] According to one possible aspect of the invention, the determination of the patient distance by the determining unit comprises determining a distance, in particular a patient distance, between the patient and an area, in particular a contact area, of the inner wall of the magnetic unit. The area, in particular the contact area, of the inner wall of the magnetic unit comprises a region between 0 and 30 cm extending from a patient support surface in a first and / or second vertical direction. The patient support surface is in particular encompassed by the patient table. The patient support surface corresponds in particular to the area on which the patient is positioned during a magnetic resonance examination.

[0071] The determination of the patient distance by the measuring unit can, for example, include determining a distance, in particular the patient distance, between the patient and an area, in particular the contact area, of the inner wall of the magnetic unit. In other words, contact between the patient and the inner wall of the magnetic unit is more likely to occur in this area, in particular the contact area, than in other parts of the patient reception area. This area, in particular the contact area, of the inner wall of the magnetic unit can, for example, be an area of ​​preferably 20 cm in a first vertical direction, in particular opposite to the force of gravity. This area, in particular the contact area, of the patient tunnel can, for example, be defined by a sensor arrangement, in particular several pressure sensors, arranged in this area.The area, in particular the contact area of ​​the inner wall of the magnet unit, can comprise a region extending in a first and / or a second direction from a flat plane, which in particular runs parallel to the longitudinal axis of the patient table and is located at the point where the magnet opening has its greatest horizontal width. The extent of the region in each direction corresponds in particular to a value between 10 and 30 cm, preferably 20 cm.

[0072] Advantageously, specifying and / or focusing the patient distance measurement on the aspect-related area within the patient tunnel that is particularly susceptible to contact with the patient allows for higher sensitivity and selectivity in detecting a potentially dangerous patient position. Furthermore, this area within the patient tunnel (or an arrangement of sensors within this area) can enable better adaptation of the magnetic resonance sequence to the patient's position, for example, by optimizing the specific absorption rate (SAR). This can improve the efficiency and effectiveness of the magnetic resonance device.

[0073] According to one possible aspect of the invention, the sensor unit is configured to detect a patient extremity, in particular a hand or a foot. The sensor unit is configured to determine the positional information for the patient's extremity on the patient table.

[0074] A patient extremity is typically a part of the human body located at the end of an arm or leg, such as a hand or foot. In particular, a patient extremity can move or shift during a magnetic resonance imaging (MRI) scan, thereby changing the patient's distance. The sensor unit is therefore specifically designed to detect a patient extremity, especially a hand or foot. The sensor unit may be specifically designed to detect the patient extremity based on its shape, temperature, and / or other characteristics. The sensor unit may also be specifically designed to identify the patient extremity based on a recognition object, such as a glove (worn by the patient during the MRI scan).The sensor unit is preferably configured to determine the positional information for the patient's limb on the patient table. This positional information can include, for example, the location, orientation, speed, or acceleration of the limb. The determination unit and / or the testing unit can be specifically configured to use the positional information of the patient's limb to determine the distance between the limb and the inner wall of the magnetic unit and / or to check whether a distance limit is being met or exceeded.

[0075] The use of a sensor unit designed to detect a patient limb is advantageous, as it enables precise and reliable determination of the patient distance. The patient limb can significantly influence the patient distance, particularly if it is located near or moving towards the inner wall of the magnetic unit. The magnetic resonance device is specifically designed to continuously monitor the patient distance using the positional information of the patient limb and, upon detection of a potential risk to the patient, to reduce this risk by modifying or terminating the magnetic resonance sequence.Furthermore, the detection of the patient limb, particularly by determining the positional information of the patient limb, can enable the improvement of image quality by reducing or avoiding artifacts caused by the movement of the patient limb.

[0076] According to one possible aspect of the invention, the test unit is designed to check a magnetic resonance sequence for compliance with an absorption limit value based on the patient distance.

[0077] The absorption limit is, in particular, a maximum permissible value for the specific absorption rate (SAR), which indicates how much energy is absorbed by the patient's body. The test unit is therefore designed to check a magnetic resonance imaging (MRI) sequence for compliance with an absorption limit based on the patient's distance. For example, the test unit may be designed to adjust and / or interrupt the MRI sequence if the absorption limit is exceeded or is about to be exceeded. Furthermore, the test unit may be designed to issue a warning or instruction to the operator or the patient to correct or verify the patient's position. The maximum permissible absorption limit for the SAR is established, particularly according to international standards and guidelines, to ensure patient safety.

[0078] A test unit that checks a magnetic resonance sequence for compliance with an absorption limit based on the patient's distance can advantageously increase patient safety. The test unit can be advantageously designed to avoid or reduce potential overheating of the patient's tissue by controlling the magnetic resonance sequence.

[0079] Furthermore, a method for checking the positioning of a patient for compliance with a distance limit value in a magnetic resonance device according to one of the described aspects is proposed.

[0080] The procedure for checking patient positioning for compliance with a distance limit in a magnetic resonance device may preferably comprise the following steps: - Determining the position of the patient on a patient table using a sensor unit. - Determining the patient distance between the patient and an inner wall of the magnetic resonance device's magnet unit based on position information using a determination unit - checking the patient distance to ensure compliance with a distance limit value using a test unit.

[0081] Optionally, the procedure may also include one or more of the following steps: - checking the magnetic resonance sequence for compliance with an absorption limit based on the patient distance - Determining movement information of the patient on the patient table, in particular of a patient limb, and determining position information based on the movement information and / or checking the patient's distance based on the movement information - recording a patient's posture, in particular a patient's limb, on the patient table using a patient posture recording unit and a

[0082] Determining position information based on patient posture and / or checking patient distance based on patient posture.

[0083] The advantages of the proposed method essentially correspond to the advantages of the previously proposed magnetic resonance device, which are described in detail below. Features, advantages, or alternative embodiments mentioned therein can also be applied to the other claimed items and vice versa.

[0084] Furthermore, a computer program product is proposed that comprises a program and can be directly loaded into the memory of a programmable system control unit of a magnetic resonance device, and includes program resources, such as libraries and auxiliary functions, to execute a proposed method when the computer program product is executed in the system control unit of the magnetic resonance device. The computer program product may comprise software with source code that still needs to be compiled and bound or that only needs to be interpreted, or executable software code that only needs to be loaded into the system control unit for execution.

[0085] The proposed method can advantageously be executed quickly, identically, and robustly by the computer program product. The computer program product is preferably configured to execute the proposed method steps via the system control unit. The system control unit possesses the necessary prerequisites, such as sufficient main memory, a suitable graphics card, or a suitable logic unit, so that the respective method steps can be executed efficiently.

[0086] 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 system control unit, which may be directly connected to the magnetic resonance device or be formed as part of the magnetic resonance device. Furthermore, control information of the computer program product may be stored on an electronically readable data carrier. The control information of the electronically readable data carrier may be designed such that, when the data carrier is used in a system control unit of a magnetic resonance device, it executes a proposed procedure.

[0087] Examples of electronically readable data carriers include a DVD, a magnetic tape, or a USB flash drive, on which electronically readable control information, in particular software, is stored. If this control information is read from the data carrier and stored in a system control unit of the magnetic resonance device, all proposed embodiments of the previously described methods can be carried out.

[0088] Further advantages, features, and details of the invention will become apparent from the exemplary embodiments described below and from the drawings. Corresponding parts are designated with the same reference numerals in all figures.

[0089] They show: Fig. 1 a magnetic resonance device in a schematic representation in a first embodiment with a sensor positioned within the patient recording area, Fig. 2 a magnetic resonance device in a schematic representation in a second embodiment with a sensor positioned outside the patient recording area, Fig. 3 a magnetic resonance device in a schematic representation in a third embodiment, Fig. 4 a magnetic resonance device in a schematic representation in a fourth embodiment, Fig. 5 a block diagram of a procedure for checking the positioning of a patient for compliance with a distance limit.

[0090] In Fig. Figure 1 schematically depicts a magnetic resonance device 10. The magnetic resonance device 10 comprises a magnetic unit 11, which includes a main magnet 12 for generating a strong and, in particular, time-constant main magnetic field 13. The magnetic resonance device 10 also has a magnetic opening 14 for receiving a patient 15; that is, the magnetic opening 14 can be considered the patient receiving area. The magnetic opening 14 is in the form of a cylinder with a central axis z in the z-direction and is circumferentially surrounded by the magnetic unit 11. The magnetic opening 14 is bounded by an inner wall W of the magnetic unit 11. The patient 15 can be moved into the magnetic opening 14 by means of a patient positioning device 16 of the magnetic resonance device 10. For this purpose, the patient positioning device 16 has a patient table 17 that is movably designed within the magnetic opening 14.

[0091] The magnetic unit 11 further comprises a gradient coil unit 18 with at least one gradient coil for generating magnetic field gradients, which are used for spatial encoding during imaging. The gradient coil unit 18 is controlled by a gradient control unit 19 of the magnetic resonance device 10. The magnetic unit 11 further includes a high-frequency antenna unit 20 with at least one transmitting antenna, which in the present embodiment is designed as a whole-body coil permanently integrated into the magnetic resonance device 10. The high-frequency antenna unit 20 is controlled by a high-frequency antenna control unit 21 of the magnetic resonance device 10 and transmits high-frequency magnetic resonance sequences, in particular RF transmit pulses, into a patient acquisition area, which is essentially formed by the area of ​​the magnetic aperture 14 of the magnetic resonance device 10.This causes the main magnetic field 13 generated by the main magnet 12 to excite atomic nuclei by deflecting nuclear spins from their resting position. The relaxation of the excited atomic nuclei generates magnetic resonance signals. The high-frequency antenna unit 20 can, in principle, be configured to receive these magnetic resonance signals.

[0092] The magnetic resonance imaging (MRI) device 10 includes a system control unit 22 for controlling the main magnet 12, the gradient control unit 19, and the high-frequency antenna control unit 21. The system control unit 22 centrally controls the MRI device 10, for example, by performing a predetermined imaging gradient echo sequence. The system control unit 22 also includes an evaluation unit (not shown) for evaluating the magnetic resonance signals acquired during the MRI scan. Furthermore, the MRI device 10 includes a user interface 23 connected to the system control unit 22. Control information, such as imaging parameters, and reconstructed MRI images can be displayed on a display unit 24, for example, on at least one monitor, via the user interface 23 for medical personnel.Furthermore, the user interface 23 has an input unit 25 by means of which information and / or parameters can be entered by the medical operating personnel during a measurement process.

[0093] The transmission of RF pulses by the high-frequency antenna unit 20 can cause the tissue of patient 15 to heat up, which can be described by the specific absorption rate (SAR). Particularly in the immediate vicinity of the high-frequency antenna unit 20, local intensity maxima can occur, potentially leading to burns in the patient 15 in the worst cases. According to the current state of the art, the transmission power of the high-frequency antenna unit 20 is therefore limited by a so-called touch protection mechanism, which is based on conservative assumptions about the actual position of patient 15 in the magnetic opening 14. To eliminate these assumptions, it would be desirable to obtain more precise information about the actual position of patient 15.

[0094] The magnetic resonance device 10 also includes a patient identification unit 30, which is located in Fig. Figure 1 is shown schematically. The patient determination unit 30 serves to detect the position of the patient 15 in the patient reception area, or the magnetic opening 14, and to check whether a predefined distance limit between the patient 15 and the inner wall W of the magnetic unit 11 is maintained. This distance limit is intended to ensure that the patient 15 does not accidentally come into contact with the high-frequency antenna unit 20 (or the inner wall W enclosing the high-frequency antenna unit 20) or is overheated by it. The patient determination unit 30 has a determination unit 31, which is connected to the system control unit 22. The determination unit 31 is designed to determine the position of the patient 15 based on the position information obtained by the sensor unit 33.

[0095] The determination unit 31 receives position information to determine the patient distance, i.e., the position of the patient 15 relative to the inner wall W. The patient determination unit 30 also includes a test unit 32, which is connected to the determination unit 31 and the system control unit 22. The test unit 32 is designed to check whether the position of the patient 15 determined by the determination unit 31, in particular the patient distance, meets or falls below a distance limit. If the distance limit is exceeded, the test unit 32 can send a warning message to the user interface 23 to inform the medical operating personnel. The patient determination unit 30 may also include a sensor unit 33, which can be arranged on and / or in the inner wall W.The sensor unit 33 can, in particular, detect direct contact between the patient 15 and the high-frequency antenna unit 20 and send corresponding information to the test unit 32. The sensor unit 33 is designed to determine the position of the patient 15 within the patient reception area 14 and send position information to the determination unit 31.

[0096] Fig. Figure 2 shows a schematic representation of a magnetic resonance device 10, which differs in some aspects from the one in Fig. The one shown differs. A key difference is that in Fig. 2. The contact area 9 is highlighted, in which the patient determination unit 30 checks the position of the patient 15. The contact area 9 can be the area around the maximum horizontal extent (in the x-direction) of the inner wall W of the magnetic unit 11. The contact area 9 can extend between 0 and 30 cm in the y-direction and / or opposite y-direction from the maximum horizontal extent. The contact area 9 can be the area around the patient support surface P. The contact area 9 can be between 0 and 30 cm high in the y-direction from the patient support surface P. In the contact area 9, the strength of the main magnetic field 13 can vary considerably, and the high-frequency antenna unit 20 can have a high transmission power. The contact area 9 is therefore a potential danger zone for the patient 15, in which the patient should always maintain a minimum distance from the inner wall W.

[0097] Unlike in the Fig. In the embodiment shown in Figure 1, in which the sensor unit 33 is attached to the inner wall W of the magnet unit 11, the sensor unit 33 is in Fig. 2 is positioned outside the magnetic opening 14 on the magnetic unit 11. The sensor unit 33 can thus determine the position of the patient 15 without direct contact with the patient 15 or the inner wall W, for example by transmitting and receiving electromagnetic signals. The sensor unit 33 can be designed, for example, as an integrated camera or as a separate sensor device. To determine the position of the patient 15, the sensor unit 33 can, for example, include one or more cameras or other optical and / or acoustic sensors that can detect the patient 15 or parts of the patient's body. The sensor unit 33 sends position information to the determination unit 31, which is included in the system control unit 22.The determination unit 31 calculates the patient distance from the position information, particularly within the contact area 9, and transmits the patient distance to the test unit 32, which can also be encompassed by the system control unit 22, as shown. The determination unit 31 and the test unit 32 are in . Fig. 2 are therefore included by the system control unit 22, while they are in Fig. 1 are represented as separate units. This means that the functions of the determination unit 31 and the test unit 32 can be integrated into the system control unit 22. In particular, the test unit 32 can be configured to compare the patient distance with a distance limit value and to trigger a warning or an action if the distance limit value is not met.

[0098] Fig. Figure 3 shows another embodiment of a magnetic resonance device 10, which differs in some aspects from those in Fig. 1 and Fig. The embodiment shown in Figure 2 differs from the one shown in Figure 2. In this embodiment, the sensor unit 33 is arranged outside the magnetic opening 14. According to this embodiment, the sensor unit 33 consists of two sensors: a transmitter 33a and a receiver 33b. The transmitter 33a can, for example, emit infrared, ultrasound, or radar waves, which can be reflected or absorbed by the patient 15. The receiver 33b can receive the reflected waves and / or the unabsorbed waves and determine the position of the patient 15 based on their travel time, intensity, or frequency change. The sensor unit 33 sends position information to the test unit 32, which is not included by the system control unit 22, as shown. This means that the functions of the test unit 32 can be executed independently of the system control unit 22, although the test unit 32 can be connected to the system control unit 22.The test unit 32 includes the determination unit 31, which calculates the patient distance, particularly within a predetermined area, a contact area, and / or a critical area (not shown), from the positional information. The test unit 32 may, for example, have its own user interface or memory to communicate or document the warning or action to the medical operating personnel.

[0099] Fig. Figure 4 shows another embodiment of a magnetic resonance device 10, which differs in some aspects from those in Fig. 1 to Fig. Figure 3 differs from the embodiment shown. In this embodiment, the sensor unit has several separate sensors 33a, 33b, 33c arranged at different positions inside or outside the magnetic opening 14. The sensor unit can, for example, include a motion sensor 33a, a patient posture detection unit 33b, and an optical sensor 33c. The motion sensor 33a and the patient posture detection unit 33b are positioned inside the magnetic opening 14, while the optical sensor 33c is arranged outside the magnetic opening 14. The motion sensor 33a can be configured to detect movement information of the patient 15 and / or a body part of the patient 15 by, for example, measuring the change in the position or orientation of the patient 15 and / or a body part of the patient 15 over a period of time.The patient posture detection unit 33b can be configured to determine patient posture information of patient 15 or a body part of patient 15 by, for example, detecting the shape or orientation of patient 15 or a body part of patient 15. The optical sensor 33c can be configured to determine optical information of patient 15 or a body part of patient 15 by, for example, capturing an image or video sequence of patient 15 or a body part of patient 15.

[0100] The magnetic resonance device 10 also has two determination units 31a and 31b, each connected to one or more sensors 33a, 33b, 33c. Determination unit 31a is connected to the motion sensor 33a and the patient posture detection unit 33b and may, for example, include one or more evaluation units configured to evaluate the data acquired by these sensors. Determination unit 31a may, in particular, be configured to determine motion information or patient posture information based on the acquired data and to transmit this information to the test unit 32. Determination unit 31b is connected to and / or encompassed by sensor 33c and may, for example, include a processing unit configured to calculate a patient distance from the data measured by sensor 33c.The determination unit 31b can in particular be designed to determine a patient distance based on the measured data and to send this to the test unit 32.

[0101] The test unit 32 can be connected to the determination units 31a and 31b as well as to the system control unit 22. The test unit 32 can, for example, include a warning or control unit configured to check whether the information determined by the determination units 31a and 31b complies with one or more limit values. In particular, the test unit 32 can be configured to check whether the patient distance complies with or falls below a distance limit value, or whether the movement information or patient posture information indicates a predetermined and / or critical position or posture of the patient 15. If a limit value is exceeded, the test unit 32 can send a warning message to the user interface 23 or perform an appropriate action, such as adjusting or aborting the magnetic resonance measurement.

[0102] In Fig.5 is a method for checking the positioning of a patient 15 for compliance with a distance limit value in a magnetic resonance device 10. This method is preferably carried out during a magnetic resonance measurement of the patient 15 by the magnetic resonance device 10.

[0103] In process step S40, the patient's position on a patient table is determined using a sensor unit (or multiple sensor units). This determination of position information can, for example, involve the acquisition of position data using an ultrasonic sensor located within the patient reception area on an inner wall of the magnetic unit.

[0104] In process step S41, the patient distance between the patient and an inner wall of the magnetic resonance device's magnet unit is determined using position information via a determination unit. The determination unit can, for example, include an evaluation unit designed to evaluate received sensor signals, particularly the position information. For instance, determining the patient distance can involve converting the position information using a reference value and / or reference information.

[0105] In process step S42, the patient distance is checked for compliance with a distance limit value using a test unit. The distance limit value can, for example, define a minimum distance between the patient and an inner wall of the magnetic unit, which should not be undercut to prevent excessive heating or burns to the patient. The test unit can, for example, include a warning or control unit designed to issue a warning or initiate appropriate action if the patient distance violates the distance limit value.

[0106] Optionally, the procedure may also include one or more of the following steps: In process step S50, the magnetic resonance sequence is checked for compliance with an absorption limit based on the patient distance. The absorption limit can, for example, define a specific absorption rate (SAR) that must not be exceeded to prevent excessive heating of the patient. Checking the magnetic resonance sequence may result in adjustments to the transmit power or the pulse shape of the radio frequency antenna unit to ensure compliance with the absorption limit.

[0107] In process step S43, patient movement information on the patient table, particularly of a patient limb, is determined, and position information and / or patient distance are verified based on this movement information. The movement information can be determined, for example, by continuously or periodically repeating steps S40 to S41, whereby position information from different positions within the patient reception area can be compared using the test unit over a predetermined observation period. The movement information can be transmitted directly from a motion sensor to the test unit and / or the determination unit.

[0108] In process step S44, a patient's posture, particularly that of a patient limb, is recorded on the patient table using a patient posture detection unit. Position information and / or distance are then determined and / or verified based on this posture. The patient posture detection unit may, for example, include an optical or acoustic unit designed to detect the orientation or shape of the patient or a patient limb. The patient posture determined by the patient posture detection unit can then be transmitted directly to the verification unit and / or the determination unit.

[0109] Procedure steps S40 to S42 are repeated periodically to ensure continuous monitoring of the patient's position within the patient acquisition area during a magnetic resonance imaging (MRI) scan. If the check of the position information or the patient distance in procedure step S42 yields a critical result, an appropriate countermeasure is triggered. Position information or the patient distance can be critical, in particular, if a minimum distance between the patient 15 and the inner wall W of the magnet opening 14 is not maintained. A countermeasure could, for example, be to terminate the measurement or to adjust the MRI scan, especially by adjusting parameters of the MRI sequence being used.

[0110] Finally, it should be noted once again that the methods described in detail above, as well as the illustrated magnetic resonance device, are merely exemplary embodiments which can be modified in various ways by those skilled in the art without departing from the scope of the invention. Furthermore, the use of the indefinite articles "a" or "an" does not preclude the possibility that the features in question may be present multiple times. Likewise, the term "unit" does not preclude the possibility that the components in question consist of several interacting sub-components, which may also be spatially distributed.

[0111] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

Claims

[1] Magnetic resonance device comprising a magnetic unit which surrounds a patient reception area, particularly one defined by a magnetic opening, and includes a body coil, a patient table who can be taken to the patient admission area, and a patient positioning device, which includes a sensor unit, a determination unit and a testing unit, wherein the sensor unit is designed to determine the positional information of a patient on the patient table, wherein the determination unit is designed to determine a patient distance between the patient and the inner wall of the magnetic unit based on the position information, the test unit is designed to check the patient's positioning for compliance with a distance limit based on the patient's distance. [2] Magnetic resonance device according to claim 1, wherein the sensor unit comprises a distance sensor for detecting the position information, wherein the magnetic unit comprises the distance sensor. [3] Magnetic resonance device according to one of the preceding claims, wherein the sensor unit comprises an ultrasonic sensor. [4] Magnetic resonance device according to one of the preceding claims, wherein the sensor unit comprises a pressure sensor. [5] Magnetic resonance device according to one of the preceding claims, wherein the sensor unit comprises an optical sensor, in particular a camera. [6] Magnetic resonance device according to one of the preceding claims, wherein the sensor unit is arranged at a position on the inner wall of the magnet unit where a local field strength of the body coil exceeds a threshold value. [7] Magnetic resonance device according to any of the preceding claims, wherein the sensor unit comprises a sensor, in particular an optical sensor, wherein the sensor is located outside the patient reception area, in particular on an end face of the magnetic unit. [8] Magnetic resonance device according to any one of the preceding claims, the sensor unit comprises a transmitter and a receiver, wherein the transmitter of the sensor unit is arranged at a first opening of the magnet unit and the receiver of the sensor device is arranged at a second opening of the magnet unit, wherein the transmitter of the sensor unit is configured to emit electromagnetic radiation, and the receiver is designed to receive the electromagnetic radiation. [9] Magnetic resonance device according to any one of the preceding claims, wherein a first sensor of the sensor unit is arranged outside the patient reception area on the magnet unit and wherein a second sensor of the sensor unit is arranged within the patient reception area on the magnet unit. [10] Magnetic resonance device according to any one of the preceding claims, the sensor unit includes a motion sensor, wherein the motion sensor is designed to capture movement information of the patient, and wherein the determination unit is designed to determine a patient distance between the patient and the inner wall of the magnetic unit based on the movement information. [11] Magnetic resonance device according to any one of the preceding claims, wherein the magnetic resonance device includes a patient posture detection unit, who is trained to assess a patient's posture on the examination table, and the testing unit is trained to check the patient's posture against a predetermined position. [12] Magnetic resonance device according to any one of the preceding claims, wherein the determination of the patient distance by the determination unit comprises a determination of a distance between the patient and an area of ​​the inner wall of the magnet unit, wherein the area of ​​the inner wall comprises a range between 0 and 30 cm extending from a patient support surface in a first and / or second vertical direction. [13] Magnetic resonance device according to any one of the preceding claims, wherein the sensor unit is designed to detect a patient extremity, in particular a hand or a foot and The sensor unit is designed to determine the position information for the patient's extremity on the patient table. [14] Magnetic resonance device according to one of the preceding claims, wherein the test unit is configured to test a magnetic resonance sequence for compliance with an absorption limit value based on the patient distance. [15] Computer-implemented method for checking the positioning of a patient for compliance with a distance limit in a magnetic resonance device according to any one of claims 1 to 14. [16] Computer program product which can be loaded directly into the patient positioning device of the magnetic resonance device according to any one of claims 1 to 14, comprising program code means for executing a computer-implemented method according to claim 15 when the computer program product is executed in the patient positioning device of the magnetic resonance device.

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