WO2011033422A1

WO2011033422A1 - Mr imaging system comprising physiological sensors

Info

Publication number: WO2011033422A1
Application number: PCT/IB2010/054051
Authority: WO
Inventors: Cornelis Leonardus Gerardus Ham; Gabriele Marianne Beck; Miha Fuderer
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2009-09-17
Filing date: 2010-09-08
Publication date: 2011-03-24

Abstract

The invention relates to a magnetic resonance imaging system comprising a main magnet coil (2) for generating a uniform, steady magnetic field within an examination volume, a number of gradient coils (4, 5, 6) for generating switched magnetic field gradients in different spatial directions within the examination volume, at least one RF coil unit (9, 11, 12, 13) for generating RF pulses within the examination volume and/or for receiving MR signals from an object (10) positioned in the examination volume, a control unit (16) for controlling the temporal succession of RF pulses and switched magnetic field gradients, and a reconstruction unit (17) for reconstructing a MR image from the MR signals. The invention proposes that the at least one RF coil unit (9, 11, 12, 13) incorporates at least one physiological sensor (19) for receiving physiological signals from the object (10).

Description

MR imaging system comprising physiological sensors

FIELD OF THE INVENTION

The invention relates to the field of magnetic resonance (MR) imaging. It concerns a MR imaging system comprising at least one physiological sensor for receiving physiological signals from the body of a patient placed in an examination volume of the MR imaging system.

Image-forming MR methods which utilize the interaction between magnetic fields and nuclear spins in order to form two-dimensional or three-dimensional images are widely used nowadays, notably in the field of medical diagnostics, because for the imaging of soft tissue they are superior to other imaging methods in many respects, do not require ionizing radiation and are usually not invasive.

BACKGROUND OF THE INVENTION

According to the MR method in general, the body of the patient to be examined is arranged in a strong, uniform magnetic field whose direction at the same time defines an axis (normally the z-axis) of the co-ordinate system on which the measurement is based. The magnetic field produces different energy levels for the individual nuclear spins in dependence on the magnetic field strength which can be excited (spin resonance) by application of an electromagnetic alternating field (RF field) of defined frequency (so-called Larmor frequency, or MR frequency). From a macroscopic point of view the distribution of the individual nuclear spins produces an overall magnetization which can be defiected out of the state of equilibrium by application of an electromagnetic pulse of appropriate frequency (RF pulse) while the magnetic field extends perpendicular to the z-axis, so that the magnetization performs a precessional motion about the z-axis. The variation of the magnetization can be detected by means of receiving RF coils which are arranged and oriented within an examination volume of the MR device in such a manner that the variation of the magnetization is measured in the direction perpendicular to the z-axis. In order to realize spatial resolution in the body, linear magnetic field gradients extending along the three main axes are superposed on the uniform magnetic field, leading to a linear spatial dependency of the spin resonance frequency. The signal picked up in the receiving coils then contains components of different frequencies which can be associated with different locations in the body. The signal data obtained via the receiving coilscorresponds to the spatial frequency domain and is called k-space data. The k-space data usually includes multiple lines acquired with different phase encoding. Each line is digitized by collecting a number of samples. A set of k-space data is converted to an MR image, e.g., by means of Fourier transformation.

In some applications, it is necessary to remotely monitor the patient undergoing a MR imaging scan, for example in order to determine the patients heartbeat, the ECG, the respiration, the body temperature, or the blood oxygenation. Remote monitoring systems comprising physiological sensors to be used in a MR imaging environment are known in the art, see for example WO 2006/099011 Al . Known monitoring systems provide physiological sensors arranged on or in close proximity to the patient placed in the examination volume of the MR apparatus. The physiological sensors are connected by electrical or optical cables to a monitoring unit outside of the examination volume. A drawback of the known patient monitoring systems is that the comparably long cable connections between the physiological sensors and the remote monitoring unit are cumbersome and can interfere with access to the patient. Moreover, dangerous currents may be induced in the cables by the RF radiation generated during the MR imaging procedure. Wireless techniques of monitoring the patient in the examination volume are known in the art, however, the radio transmission between the physiological sensors and the remote monitoring unit is also problematic in the MR imaging environment. On the one hand, this is because the examination volume of the MR imaging system is surrounded by a RF shielding restricting the transmission of radio signals for patient monitoring. On the other hand, the RF pulses being part of the MR imaging procedure can interfere with the wireless transmission. Moreover, a major drawback of known patient monitoring systems for MR applications is that the setup of the physiological sensors on or near the patient requires a considerable preparation effort and time for each individual MR imaging session.

SUMMARY OF THE INVENTION

From the foregoing it is readily appreciated that there is a need for an improved MR imaging system comprising physiological sensors. It is consequently an object of the invention to provide a MR imaging system which enables effective and reliable patient monitoring during the MR imaging procedure. In accordance with the present invention, a magnetic resonance imaging system is disclosed. The system comprises:

a main magnet coil for generating a uniform, steady magnetic field within an examination volume,

a number of gradient coils for generating switched magnetic field gradients in different spatial directions within the examination volume,

at least one RF coil unit for generating RF pulses within the examination volume and/or for receiving MR signals from an object positioned in the examination volume, wherein the at least one RF coil unit incorporates at least one physiological sensor for receiving physiological signals from the object,

a control unit for controlling the temporal succession of RF pulses and switched magnetic field gradients, and

a reconstruction unit for reconstructing a MR image from the MR signals.

Preferably, the object from which MR signals and physiological signals are acquired in accordance with the invention is a body of a human patient or an animal undergoing medical MR imaging.

The gist of the invention is the incorporation of one or more physiological sensors into the at least one RF coil unit of the MR imaging system. The sensor setup being integrated into the RF coil unit has the advantage that patient monitoring can be performed via the integrated physiological sensors without any additional preparation effort and time. The physiological signals of interest can always be detected without any time penalties. A further advantage is that no additional wire-connected or wireless signal transmission lines are required for transmission of the received physiological signals from the physiological sensors to the remote monitoring hardware of the MR imaging system. Instead, the signal transmission lines (wire-connected or wireless) that are present anyway for transmitting the received MR signals from the RF coil unit to the remote signal acquisition and processing hardware of the MR imaging system are used for transmitting the received physiological signals as well. In accordance with the invention, integration of at least one physiological sensor means that the transducer of the sensor and/or the sensor electronics are physically incorporated in or at least electrically connected to the respective RF coil unit.

In future MR imaging systems, the RF coils will be "digital". This means that the MR imaging systems comprises one or more RF coil units, each of which comprises one or more RF antennae for picking up MR signals from the body of the examined patient, one or more low-noise amplifiers for amplifying the picked up MR signals and one or more analog-to-digital converters for converting the amplified MR signals into digital signal samples. The digital signal samples are provided to a signal transmission interface enabling the transmission of the digitized MR signals via a digital data network to a data acquisition system. In this architecture, the RF coil units consitute nodes within the digital data network. The data acquisition system (DAS) is used to buffer the raw data received from the RF coil units. The digital raw data are accessible in the data acquisition system for the reconstruction unit of the MR imaging system for reconstructing MR images from the digital raw data. In a typical modern MR imaging environment, the data acquisition system is a separate computer. The RF coil units communicate with the data acquisition system, for example, via a hub in the digital data network. The physical connections of the digital data network, i.e. the signal transmission lines for transmitting the received MR signals to the further signal processing hardware of the MR imaging system, may be fiber-optic links or wireless links according to per se known standards in the field of digital data network communication.

According to a preferred embodiment of the invention, the physiological signals received via the at least one physiological sensor are also transferred via the digital data network interconnecting the at least one RF coil unit and the data acquisition system. In this way, the data acquisition system is enabled to collect both the received MR signals and the physiological signals for further processing.

However, it has to be noted that the basic idea of integrating one or more physiological sensors into the at least one RF coil unit is, of course, likewise applicable to 'analog' RF coils in conventional MR systems.

As an alternative solution of the above-mentioned problem, the invention discloses a MR imaging system, in which the at least one physiological sensor is not incorporated into the at least one RF coil unit but is separately connected to the digital data network to enable the data acquisition system to handle both the received MR signals as well as the physiological signals. The digital data network being present anyway for

interconnecting the at least one RF coil unit and the data acquisition system is

advantageously used for transmission of the physiological signals in this embodiment as well. Separate signal transmission lines for patient monitoring can likewise be avoided in this way.

According to a further preferred embodiment of the invention, the magnetic resonance imaging system comprises a digital computer device, such as a display (for example a LCD screen), a communication device (comprising, for example, a speaker and a microphone), an input device (for example a keyboard or a joystick), or a digital camera, wherein the digital computer device is connected to the digital data network either directly or via the at least one RF coil unit. A variety of functionalities can be made available in the examination volume of the MR imaging system in this way.

The digital computer device comprises digital components producing spurious signals that may disturb the MR signal acquisition. Therefore, the digital computer device may advantageously be RF-shielded. However, the RF-shielding may be problematic in the MR environment because of eddy currents induced by switched magnetic field gradients during the MR imaging procedure. Hence, instead of RF-shielding, the control unit of the MR imaging system may be configured to synchronize the operation of the digital computer device and the MR signal acquisition.

According to another preferred embodiment of the invention, the at least one

RF coil unit is adapted to be positioned directly on or adjacent to the body of the patient. In this embodiment, the RF coil unit is a 'local' RF coil unit which can be used for MR signal acquisition from limited regions of the body of the patient. A set of such local RF coil units forming a coil array may be placed contiguous to the region selected for imaging. Since the RF coil unit is positioned directly on or adjacent to the body of the patient, reception of the physiological signals from the body via the at least one physiological sensor, which is incorporated into the RF coil unit, is facilitated.

The physiological sensor of the MR imaging system according to the invention may be configured to receive physiological signals indicating patient motion, temperature, respiration, blood oxygenation, blood pressure or pulse. The physiological sensor may, for example, be an ECG or VCG sensor, wherein the ECG or VCG signals are picked up from the body of the patient via electrodes that are connected to the RF coil unit. The specific ECG or VCG sensor electronics are advantageously integrated into the RF coil unit. Alternatively, the physiological sensor may be a motion sensor, realized as, for example, a compression sensor, an acceleration sensor or a position sensor, wherein the motion sensor generates motion signals that can be used for motion correction in the MR imaging procedure. A motion sensor physically integrated into the RF coil unit positioned directly on the body of the patient in the region to be imaged can advantageously be used to detect motion of the body of the patient in the respective region of interest.

In case the physiological sensor is a motion sensor, as discussed before, which is adapted for detecting signals related to motion of the body in at least one spatial direction, the magnetic resonance imaging system may be advantageously configured to a) acquire a calibration MR signal data set by subjecting at least a portion of the body to a calibration imaging sequence comprising at least one RF pulse and switched magnetic field gradients,

b) acquire motion signals from the motion sensor during acquisition of the calibration MR signal data set,

c) derive motion estimates from the calibration MR signal data set,

d) translate the motion signals acquired from the motion sensor into quantitative displacement values by correlating the motion signals with the derived motion estimates.

In this embodiment, a calibration scan is applied to enable the translation of the motion signals detected via the motion sensor into quantitative displacement values of the examined moving portion of the body. These quantitative displacement values can then be used to correct for patient motion in MR signal data acquisition and/or MR image reconstruction. It is well known that motion is a major problem in MR imaging leading to blurring and ghosting in the reconstructed images. The physical integration of a motion sensor into the RF coil unit according to the invention provides a useful tool for consistently enforcing motion compensation in a reproducible way with a minimum patient preparation time. In this way, image quality can be significantly improved.

Optionally, a number of two or more motion sensors may be integrated into one RF coil unit. In this way, motion information collected via the different sensors may be combined in a motion model used for motion compensation. Alternatively, one sensor having the highest sensitivity may be selected automatically from the set of integrated sensors in the respective application.

According to yet another preferred embodiment of the invention, the physiological sensor is an optical sensor including a light source for illuminating the surface of the body, and a light sensor for detecting the light reflected from the surface of the body, wherein the optical sensor is configured to translate the signals of the light sensor into motion of the surface of the body relative to the light source. The optical sensor illuminates the surface of the examined body, using for example a LED or a laser diode. Changes between successively detected light reflection patterns are processed and translated into motion signals indicating the motion of the surface of the body relative to the light source. The operation principle of the described optical sensor corresponds to the operation principle of known optical computer mouse devices. The optical sensor may be used preferably in the case that the RF coil unit is not directly attached to the body of the patient. The enclosed drawings disclose preferred embodiments of the present invention. It should be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings

Fig. 1 shows a MR imaging system according to the invention;

Fig. 2 schematically shows a first embodiment of RF coil units interconnected with a data acquisition system according to the invention via a digital data network;

Fig. 3 schematically shows a second embodiment of RF coil units and a data acquisition system interconnected via a digital data network;

Fig. 4 schematically illustrates a digital data network interconnecting a RF coil unit, a digital acquisition system, and further digital computer devices;

Fig. 5 shows a diagram illustrating the operation of a digital computer device synchronized with RF irradiation and MR signal acquistion in accordance with the invention.

With reference to Figure 1 , a MR imaging system 1 is shown. The system comprises superconducting or resistive main magnet coils 2 such that a substantially uniform, temporally constant main magnetic field is created along a z-axis through an examination volume.

DETAILED DESCRIPTION OF EMBODIMENTS

A magnetic resonance generation and manipulation system applies a series of RF pulses and switched magnetic field gradients to invert or excite nuclear magnetic spins, induce magnetic resonance, refocus magnetic resonance, manipulate magnetic resonance, spatially and otherwise encode the magnetic resonance, saturate spins, and the like to perform MR imaging.

More specifically, a gradient pulse amplifier 3 applies current pulses to selected ones of whole-body gradient coils 4, 5 and 6 along x, y and z-axes of the

examination volume. A RF transmitter 7 transmits RF pulses or pulse packets, via a send- /receive switch 8, to a whole-body volume RF coil 9 to transmit RF pulses into the examination volume. A typical MR imaging sequence is composed of a packet of RF pulse segments of short duration which taken together with each other and any applied magnetic field gradients achieve a selected manipulation of nuclear magnetic resonance. The RF pulses are used to saturate, excite resonance, invert magnetization, refocus resonance, or manipulate resonance and select a portion of a body 10 positioned in the examination volume. The MR signals can also be picked up by the whole-body volume RF coil 9.

For generation of MR images of limited regions of the body 10, a set of local RF coil units 11, 12, 13 are placed contiguous to the region selected for imaging. The RF coil units 11, 12, 13 can be used to receive MR signals induced by body-coil RF transmissions.

The RF coil units 11, 12, 13 are 'digital' coils, which means that each RF coil unit 11, 12, 13 incorporates one or more RF antennae for picking up the MR signals from the body 10, and receiving electronics for amplification, demodulation and analog-to-digital conversion of the picked up MR signals. Moreover, each of the RF coil units 11, 12, 13 includes a signal transmission interface connected to the RF antennae via the receiving electronics, wherein the signal transmission interface establishes the connection of the RF coil units 11, 12, 13 to a digital data network 14.

MR signals picked up by the whole body volume RF coil 9 are demodulated and converted into digital signal samples by means of a separate receiver 15. The receiver 15 is connected to the digital data network via a corresponding signal transmission interface as well. The receiver 15 is connected to the whole body volume RF coil 9 via the send-/receive switch 8.

A control and data acquisition system (DAS) 16 controls the gradient pulse amplifier 3 and the transmitter 7 to generate any of a plurality of MR imaging sequences, such as echo planar imaging (EPI), echo volume imaging, gradient and spin echo imaging, fast spin echo imaging, and the like. For the selected sequence, a single or a plurality of MR data lines are received via the RF coil units 11, 12, 13 and/or via the whole body volume RF coil 9 in rapid succession following each RF excitation pulse. The DAS 16 is connected to the digital data network 14 and collects and buffers the digital MR signal samples. The DAS 16 is a separate computer which is specialized in the control of the MR imaging system and in the buffering of the digital raw data.

Ultimately, the digital raw image data is reconstructed into an image representation by a reconstruction processor 17 which applies a Fourier transform or other appropriate reconstruction algorithms. The MR image may represent a planar slice through the patient, an array of parallel planar slices, a three-dimensional volume, or the like. The image is then stored in an image memory where it may be accessed for converting slices, projections, or other portions of the image representation into appropriate format for visualization, for example via a video monitor 18 which provides a man-readable display of the resultant MR image. In the depicted embodiment, the reconstruction processor 17 is directly connected to the DAS 16.

A physiological sensor 19 configured to receive signals indicating motion of the body 10 of the patient is incorporated into RF coil unit 11. The RF coil unit 11 is positioned adjacent to the body 10 of the patient. The sensor element of the motion sensor 19 (such as, e.g., an acceleration sensor) is fixated on the shoulder of the patient as indicated in figure 1. The sensor element is connected to the RF coil unit 11 via a cable connection. The specific sensor electronics of the motion sensor is integrated into the RF coil unit 11. An optical sensor physically integrated into the RF coil unit 11 may be used likewise for motion detection. Such an optical sensor includes a light source for illuminating the surface of the body 10, and a light sensor for detecting the light reflected from the surface of the body 10, wherein the optical sensor is configured to translate the signals of the light sensor into motion of the surface of the body relative to the light source. The operation principle of the optical motion sensor corresponds to the operation principle of known optical computer mouse devices. The sensor element may also be physically integrated into the RF coil unit, for example, within a foam sheath covering the RF antenna of the RF coil unit 11. In this case, the RF coil unit 11 with the integrated motion sensor 19 can be positioned directly on the body 10 of the patient in order to detect motion of the body 10 in the region from which the MR signals are acquired.

The motion sensor 19 is adapted for detecting signals related to motion of the body 10 in at least one spatial direction. The detected motion signals are transmitted via the digital data network 14 to the DAS 16 for further processing.

As mentioned above, motion of the body 10 can adversely affect image quality in a variety of MR imaging applications. Acquisition of sufficient MR data for reconstruction of an image takes a finite period of time. Motion of the body 10 to be imaged during that finite acquisition time typically results in motion artifacts in the reconstructed MR image. In the case of medical MR imaging, motion artifacts can result for example from cardiac cycling, respiratory cycling, and other physiological processes, as well as from patient motion. The motion of the body 10 during MR signal data acquisition leads to different kinds of blurring, mispositioning and deformation artifacts.

The so-called navigator technique has been developed to overcome problems with respect to motion by prospectively adjusting the imaging parameters defining the location and orientation of the field of view within the imaging volume. In the navigator technique, a MR signal data set is acquired from a pencil- shaped volume (navigator beam) located within the region of interest. The navigator beam is placed in such a way that the position of the anatomical structure of interest can be reconstructed from the acquired MR signal data set and used for correction of the field of view in real time. The navigator technique is for example used for minimizing the effects of breathing motion in cardiac examinations.

A drawback of the navigator technique is that it requires extra scan time. The actual MR signal acquisition has to be interrupted for acquisition of the navigator signals.

The integration of the motion sensor 19 into the RF coil unit 11 according to the invention is particularly well-suited for motion correction in MR imaging. Motion detection is enforced by the integration of the motion sensor 19 in a reproducible way with a minimum patient preparation effort and time. The detected motion signals can be used for rejection or reacquisition of MR signal data or for motion correction in order to achieve an improved image quality.

For example, motion in MR imaging of the shoulder basically consists of breathing motion of the patient mainly in the feet-head direction and incidental shoulder motion in all directions. Fixation of the motion sensor 19 on the shoulder, as indicated in figure 1, integrated in the corresponding shoulder RF coil unit 11 enables the reproducible detection of breathing motion with optimal motion sensitivity as well as the detection of incidental motion of the shoulder. The detected motion signals can be used for appropriate rejection or reacquisition of MR signal data as well as for prospective motion correction in a manner which is known per se in the art.

In carotid artery MR imaging applications (not depicted) the motion of the body of the patient consists of pulsation, breathing motion and also incidental swallowing motion. Fixation of the motion sensor integrated in the left and/or right carotid RF coil unit near the throat of the patient enables detection of incidental swallowing motion and corresponding motion correction.

A motion calibration scan may be applied in order to enable translation of the motion signals received via the motion sensor 19 into quantitative displacement values, which are needed for motion correction in MR imaging. During such a calibration scan, for example the above-described navigator technique may be employed, wherein the navigator beam is placed at or near the location of the motion sensor 19. In this way, quantitative displacement values can directly be obtained from the MR signal data set acquired during the calibration scan. A motion model may improve the translation of the motion signals from the motion sensor 19 into quantitative displacement values for prospective motion correction (see for example Manke et al, Magnetic Resonance in Medicine 2003, vol. 50, issue 1, pages 122-131).

Figure 2 shows the RF coil units 11, 12, 13, wherein each coil unit 11, 12, 13 comprises two or more RF antennae 21 for picking up the MR signals. The RF antennae 21 of each RF coil unit 11, 12, 13 are connected to an electronics module 22 including the electronics necessary for amplifying, demodulating, and sampling the picked up MR signals. The RF coil units 11, 12, 13 are interconnected by a digital data link 23 in a daisy-chained manner. The digital data network 14 interconnects the RF coil units 11, 12, 13 to the data acquisition system 16. In the embodiment shown in figure 2, VCG-electrodes 24 are plugged into the RF coil unit 11. The specific VCG sensor electronics are integrated into the electronics module 22 of the RF coil unit 11.

Figure 3 shows an alternative embodiment, in which the VCG-electrodes 24 are connected to a separate electronics module 25. The electronics module 25 is connected via a digital data link 23 to the electronic module 22 of the RF coil units 12.

In both embodiments shown in figures 2 and 3, the RF coil unit 13 may be connected directly to the digital data network 14 or indirectly via an appropriate network node, such as, for example, a hub. In principle, an arbitrary number of RF coil units can be connected to the data acquisition system 16 of the magnetic resonance imaging system in this way.

In another embodiment (not depicted) a physiological sensor may be directly connected to a digital interface located in or near the examination volume of the MR imaging system. The digital interface is connected to the digital data network 14 and enables transmission of the physiological signals to the data acquisition system 16. The digital interface provides communication between the data acquisition system 16 as well as power supply of the physiological sensor.

Figure 4 schematically illustrates an embodiment, in which a digital computer device 26 is connected to the RF coil unit 11. A further digital computer device 27 is directly connected to the digital data network 14, for example via a hub (not depicted). The digital computer devices 26, 27 may be displays, communication devices, input devices, digital cameras or the like. One of the digital computer devices 26 or 27 may be a 'nurse call' device, which enables the examined patient to contact the medical staff during a MR imaging session. The status of this device can easily be communicated to the data acquisition system 16 and to the console of the operator of the MR imaging system. In order ensure a fail-safe operation of the 'nurse-call' device, a polling mechanism may be implemented in order to verify that the communication between the patient and the operator is functioning.

The data link between the digital computer device 26 or 27 and the RF coil unit 11 or the digital data network 14 may be a USB link or a Firewire link.

The computer devices 26, 27 contain digital components producing spurious signals that might interfere with the MR signal acquisition. The upper diagram in figure 5 illustrates the succession of RF irradiation and MR signal acquisition during an MR imaging session. The lower diagram illustrates a control signal, which is provided to the digital computer devices 26, 27 via the digital data network 14 in order to synchronize the operation of the digital computer devices 26, 27 with the MR data acquisition. As can be seen in the diagrams, the digital computer devices 26, 27 are switched between an 'active' mode and a 'silent' mode. In the 'silent' mode the digital computer devices 26, 27 are in a mode of operation, in which they do not produce undesirable spurious signals. The digital computer devices 26, 27 are switched into the 'silent' mode during the MR signal acquisition phases of the MR imaging procedure. Typically, around 30% of the total scan time is used for the actual MR signal acquisition. This means that the digital computer devices 26, 27 are operable during the major part of the scan time.

Claims

CLAIMS:

1. Magnetic resonance imaging system comprising:

a main magnet coil (2) for generating a uniform, steady magnetic field within an examination volume,

a number of gradient coils (4, 5, 6) for generating switched magnetic field gradients in different spatial directions within the examination volume,

at least one RF coil unit (9, 11, 12, 13) for generating RF pulses within the examination volume and/or for receiving MR signals from an object (10) positioned in the examination volume, wherein the at least one RF coil unit (9, 11, 12, 13) incorporates at least one physiological sensor (19) for receiving physiological signals from the object (10),

a control unit (16) for controlling the temporal succession of RF pulses and switched magnetic field gradients, and

a reconstruction unit (17) for reconstructing a MR image from the MR signals.

2. Magnetic resonance imaging system according to claim 1, further comprising:

a data acquisition system (16) for collecting the received MR signals and the physiological signals as digital raw data for further processing,

a digital data network (14) interconnecting the at least one RF coil unit (9, 11, 12, 13) and the data acquisition system (16),

wherein the reconstruction unit (17) is configured to process the digital raw data received from the data acquisition system (16).

3. Magnetic resonance imaging system comprising:

at least one RF coil unit (9, 11, 12, 13) for generating RF pulses within the examination volume and/or for receiving MR signals from an object (10) positioned in the examination volume, wherein the at least one RF coil unit (9, 11, 12, 13), at least one physiological sensor (19) for receiving physiological signals from the object (10),

a control unit (16) for controlling the temporal succession of RF pulses and switched magnetic field gradients,

a reconstruction unit (17) for processing the digital raw data and for reconstructing a MR image therefrom, and

a digital data network (14) interconnecting the at least one RF coil unit (9, 11, 12, 13), the at least one physiological sensor (19) and the data acquisition system (16).

4. Magnetic resonance imaging system according to claim 2 or 3, further comprising a digital computer device (26, 27) connected to the at least one RF coil unit (9, 11, 12, 13) or to the digital data network (14).

5. Magnetic resonance imaging system according to claim 4, wherein the digital computer device (26, 27) is a display, a communication device, an input device, or a digital camera.

6. Magnetic resonance imaging system according to claim 4 or 5, wherein the digital computer device (26, 27) is RF-shielded.

7. Magnetic resonance imaging system according to any one of claims 4-6, wherein the control unit (16) is configured to synchronize the operation of the digital computer device (26, 27) and the temporal succession of RF pulses.

8. Magnetic resonance imaging system according to any one of claims 1-7, wherein the at least one RF coil unit (9, 11, 12, 13) is adapted to be positioned directly on or adjacent to the object (10).

9. Magnetic resonance imaging system according to any one of claims 1-8, wherein the physiological sensor (19) is configured to receive physiological signals indicating motion, temperature, respiration, blood oxygenation, blood pressure or pulse.

10. Magnetic resonance imaging system according to any one of claims 1-9, wherein the physiological sensor (19) is an optical sensor including a light source for illuminating the surface of the object (10), and a light sensor for detecting the light reflected from the surface of the object (10), wherein the optical sensor is configured to translate the signals of the light sensor into indicating motion signals of the surface of the object (10) relative to the light source.

11. Magnetic resonance imaging system according to any one of claims 1-10, wherein the physiological sensor (19) is a motion sensor adapted for detecting signals related to motion of the object (10) in at least one spatial direction, the system being configured to a) acquire a calibration MR signal data set by subjecting at least a portion of the object (10) to a calibration imaging sequence comprising at least one RF pulse and switched magnetic field gradients,

c) derive motion estimates from the calibration MR signal data set,

d) translate the motion signals acquired from the motion sensor into quantitative displacement values by correlating the motion signals with the derived motion estimates. 12. Magnetic resonance imaging system according to claim 11, wherein the control unit (16) and/or the reconstruction unit (17) are configured to employ the quantitative displacement values to correct for patient motion in MR signal data acquisition and/or MR image reconstruction. 13. Magnetic resonance imaging system according to any one of claims 1-12, wherein one RF coil unit (9, 11,

12,

13) incorporates two or more motion sensors.

14. RF coil unit (11, 12, 13) for a MR imaging system, comprising: at least one RF antenna (21) for picking up MR signals from an object (10);

at least one physiological sensor (19) for receiving physiological signals from the object (10),

a signal transmission interface connected to the RF antenna (21) and the physiological sensor (19) for transmitting the MR signals and the physiological signals via a signal transmission line (14, 23) to a remote signal acquisition and processing hardware (16, 17) of the MR imaging system.

15. Method of magnetic resonance imaging of an object (10) placed in an examination volume of a magnetic resonance imaging system (1), the method comprising the steps of

a) acquiring a calibration MR signal data set by subjecting at least a portion of the object (10) to a calibration imaging sequence comprising at least one RF pulse and switched magnetic field gradients,

wherein at least one RF coil unit (9, 11, 12, 13) of the magnetic resonance imaging system (1) is used for generating RF pulses within the examination volume and/or for receiving MR signals from the object (10),

b) acquiring motion signals from a motion sensor (19) during acquisition of the calibration MR signal data set, wherein the motion sensor (19) is incorporated into the at least one RF coil unit (9, 11, 12, 13),

c) deriving motion estimates from the calibration MR signal data set,

d) translating the motion signals acquired from the motion sensor (19) into quantitative displacement values by correlating the motion signals with the derived motion estimates.