Method and system for monitoring a motion of a subject, and corresponding computer program product

1. A method for monitoring a motion of a subject, the method comprising:

generating a monitoring signal;

coupling out a part of the monitoring signal to provide a reference monitoring signal as intended for transmission;

emitting, by an emitter, a respective remaining part of the monitoring signal towards a corresponding receiver;

receiving, by the corresponding receiver, the emitted monitoring signal to provide a received monitoring signal;

comparing, by a signal processing unit, the reference monitoring signal and the received monitoring signal; and

detecting, by the signal processing unit, the motion of the subject based on a change between the reference monitoring signal and the received monitoring signal,

wherein the respective remaining part of the monitoring signal is emitted toward the corresponding receiver: using a spread-spectrum technique, using an M-to-N multi-antenna emitter-receiver system with a set of M transmitting antennas and a set of N receiving antennas, or a combination thereof.

2. The method of claim 1 , wherein a phase and an amplitude of the emitted monitoring signal are determined as a reference for the detecting of the motion of the subject.

3. The method of claim 1 , wherein, when the monitoring signal is emitted using the spread-spectrum technique, the monitoring signal is generated through modulation with a predetermined pseudo-random spreading code.

4. The method of claim 1 , wherein the motion monitoring is combined with a magnetic resonance imaging of the subject, and

wherein a frequency of the monitoring signal is set to overlap a frequency band of a magnetic resonance imaging signal.

5. The method of claim 4 , wherein a coil used for the magnetic resonance imaging of the subject is also used for the emitting of the monitoring signal, the receiving of the monitoring signal, or a combination thereof.

6. The method of claim 5 , wherein the monitoring signal is emitted by at least one transmitting antenna,

wherein the monitoring signal is received by at least one magnetic resonance local coil,

wherein the at least one transmitting antenna is separate from at least one magnetic transmitting coil.

7. The method of claim 6 , wherein the magnetic resonance local coil comprises an array of multiple spatially distributed magnetic resonance local coils.

8. The method of claim 4 , wherein the monitoring signal is uniformly spread out over a predetermined frequency band using the spread-spectrum technique,

wherein a signal level of the monitoring signal is set so that, at each frequency, the signal level is at or below a noise level of a received magnetic resonance echo signal, and

wherein the received monitoring signal is separated from the received magnetic resonance echo signal through signal averaging over at least one time period that is longer compared to a measurement period defined in a respective MR imaging sequence.

9. The method of claim 8 , wherein the at least one time period is at least 100 milliseconds.

10. The method of claim 4 , wherein the received monitoring signal and a magnetic resonance echo signal are measured together and, for separating out the received monitoring signal, a weighting factor for minimizing a correlation between two signal parts is determined and applied to the measured signal.

11. The method of claim 4 , wherein a signal reception chain through which a magnetic resonance echo signal is received and processed is continuously or regularly calibrated during the magnetic resonance imaging and the motion monitoring based on detected variations in the received monitoring signal that are not associated with the motion of the subject.

12. The method of claim 4 , wherein a length of a predetermined pseudo-random spreading code used to spread out the monitoring signal as part of the spread-spectrum technique is set so that the monitoring signal is spread out across a full bandwidth of a magnetic resonance imaging receiving coil or coils or a full width of the frequency band used for the magnetic resonance imaging.

13. The method of claim 4 , wherein the monitoring signal is emitted and received at least between pulses of a magnetic resonance imaging sequence that is applied for imaging the subject.

14. The method of claim 1 , wherein the motion monitoring using the M-to-N multi-antenna emitter-receiver system is combined with a magnetic resonance imaging of the subject, and

wherein a frequency of the monitoring signal is set to be outside of a frequency band used for the magnetic resonance imaging.

15. The method of claim 1 , wherein the monitoring signal is emitted using the spread-spectrum technique and using multiple emitters of the M-to-N multi-antenna emitter-receiver system at a same time, and

wherein different modulations that are orthogonal with respect to each are used for emitting the monitoring signal through the multiple emitters.

16. The method of claim 15 , wherein the different modulations that are orthogonal with respect to each other are based on orthogonal spreading codes.

17. A system configured to monitor a motion of a subject, the system comprising:

an emitter configured to emit a part of a monitoring signal to provide an emitted monitoring signal, wherein a remaining part of the monitoring signal is configured to be coupled out to provide a reference monitoring signal as intended for transmission;

a receiver configured to receive the emitted monitoring signal to provide a received monitored signal; and

a signal processor configured to compare the reference monitoring signal and the received monitoring signal detect the motion of the subject based on a change between the reference monitoring signal and the received monitoring signal,

wherein the part of the monitoring signal is configured to be emitted towards the corresponding receiver: (a) using a spread-spectrum technique, (b) using an M-to-N multi-antenna emitter-receiver system with a set of M transmitting antennas and a set of N receiving antennas, or a combination thereof.

18. A non-transitory computer program product comprising instructions, wherein the instructions, when executed by a processor, cause a system to:

emit a part of a monitoring signal towards a corresponding receiver to provide an emitted monitoring signal, wherein a remaining part of the monitoring signal is coupled out to provide a reference monitoring signal as intended for transmission;

receive, by the corresponding receiver, the emitted monitoring signal to provide a received monitoring signal;

compare, by a signal processing unit, the reference monitoring signal and the received monitoring signal; and

detect, by the signal processing unit, a motion of a subject based on a change between the reference monitoring signal and the received monitoring signal,

wherein the part of the monitoring signal is emitted towards the corresponding receiver: using a spread-spectrum technique, using an M-to-N multi-antenna emitter-receiver system with a set of M transmitting antennas and a set of N receiving antennas, or a combination thereof.