MAGNETIC RESONANCE IMAGING SYSTEM WITH INTENTIONAL GRADIENT NOISE

Abstract

The present invention relates to a magnetic resonance imaging system (10), comprising at least one gradient coil (20), and a processing unit (30). The processing unit is configured to control a gradient coil to produce intentional noise for sedation monitoring of a patient.

Claims

1. A magnetic resonance imaging system, comprising: at least one gradient coil; and a processing unit; wherein, the processing unit is configured to control a gradient coil to produce intentional noise for sedation monitoring of a patient; wherein production of the intentional noise for sedation monitoring of a patient comprises the processing unit being configured to produce intentional noise in addition to a magnetic resonance imaging sequence; and wherein the intentional noise comprises one or more of: music, a synthetic representation of a human voice, clicks, noise having one or more specific pitches, noise having one or more specific tones, noise having one or more specific durations, one or more beeps, noise having one or more specific degrees of loudness.

2. The magnetic resonance imaging system according to claim 1, wherein the processing unit is configured to control a waveform of a current applied to the gradient coil to produce the intentional noise for the sedation monitoring of the patient.

3. The magnetic resonance imaging system according to claim 1, wherein the magnetic resonance imaging system comprises at least one gradient coil drive amplifier, and wherein the processing unit is configured to control a gradient coil drive amplifier to drive the gradient coil to produce the intentional noise for the sedation monitoring of the patient.

4. The magnetic resonance imaging system according to claim 1, wherein control of the gradient coil to produce intentional noise comprises utilization by the processing unit of audio relevant information about the patient, wherein the audio relevant information comprises one or more of: an indication of a hearing capability of the patient, information on hearing habits of the patient, information on preferred types of music of the patient.

5. The magnetic resonance imaging system according to claim 1, wherein the magnetic resonance imaging system is configured to acquire at least one patient response to the intentional noise for the sedation monitoring of the patient; and wherein the processing unit is configured to determine a sedation state of the patient comprising utilization of the at least one patient response to the intentional noise for the sedation monitoring of the patient.

6. The magnetic resonance imaging system according to claim 5, wherein the magnetic resonance imaging system comprises at least one sensor device; wherein the at least one sensor device is configured to acquire the at least one patient response to the intentional noise for the sedation monitoring of the patient.

7. The magnetic resonance imaging system according to claim 5, wherein the processing unit is configured to control MR imaging such that image data acquired by the magnetic resonance imaging system is useable to determine the at least one patient response to the intentional noise for the sedation monitoring of the patient.

8. The magnetic resonance imaging system according to claim 5, wherein the processing unit is configured to control and/or modify and/or alter a scan sequence on the basis of the determined sedation state of the patient.

9. The magnetic resonance imaging system according to claim 1, wherein production of the intentional noise for sedation monitoring of a patient comprises the processing unit being configured to modify a magnetic resonance imaging sequence.

10. The magnetic resonance imaging system according to claim 9, wherein modification of the magnetic resonance imaging sequence comprises an interruption of sequence steps such that a continuous pattern of noise of a standard sequence is interrupted.

11. The magnetic resonance imaging system according to claim 1, wherein production of the intentional noise for sedation monitoring of a patient comprises the processing unit being configured to re-order steps of a magnetic resonance imaging sequence.

12. The magnetic resonance imaging system according to claim 11, comprising utilization of a particularly loud parts of scans as audio stimulus at an appropriate time point, for example, without any modification of their waveforms.

13. A method of sedation monitoring of a patient, comprising: controlling by a processing unit a gradient coil of a magnetic resonance imaging system to produce intentional noise for sedation monitoring of a patient; wherein producing the intentional noise for sedation monitoring of a patient comprises the processing unit controlling the gradient coil to produce intentional noise in addition to a magnetic resonance imaging sequence; and wherein the intentional noise comprises one or more of: music, a synthetic representation of a human voice, clicks, noise having one or more specific pitches, noise having one or more specific tones, noise having one or more specific durations, one or more beeps, noise having one or more specific degrees of loudness.

14. A computer program comprising machine executable instructions stored on a non-transitory computer readable medium such that when executed on a magnetic resonance system having at least one gradient coil; and a processing unit; the computer program causes the processing unit to perform a method of controlling by the processing unit the gradient coil of the magnetic resonance imaging system to produce intentional noise for sedation monitoring of a patient; wherein producing the intentional noise for sedation monitoring of a patient comprises the processing unit controlling the gradient coil to produce intentional noise in addition to a magnetic resonance imaging sequence; and wherein the intentional noise comprises one or more of: music, a synthetic representation of a human voice, clicks, noise having one or more specific pitches, noise having one or more specific tones, noise having one or more specific durations, one or more beeps, noise having one or more specific degrees of loudness.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Exemplary embodiments will be described in the following with reference to the following drawing:

[0036] FIG. 1 shows a schematic set up of an example of magnetic resonance imaging system.

DETAILED DESCRIPTION OF EMBODIMENTS

[0037] FIG. 1 shows an example of a magnetic resonance imaging system 10. The system 10 comprises at least one gradient coil 20, and a processing unit 30. The processing unit is configured to control a gradient coil to produce intentional noise for sedation monitoring of a patient.

[0038] In an example, the intentional noise comprises music.

[0039] In an example, the intentional noise comprises a synthetic representation of a human voice.

[0040] In an example, the intentional noise comprises clicks.

[0041] In an example, the intentional noise comprises noise having one or more specific pitches.

[0042] In an example, the intentional noise comprises noise having one or more specific tones.

[0043] In an example, the intentional noise comprises noise having one or more specific durations.

[0044] In an example, the intentional noise comprises one or more beeps.

[0045] In an example, the intentional noise comprises noise having one or more specific degrees of loudness.

[0046] According to an example, the processing unit is configured to control a waveform of a current applied to the gradient coil to produce the intentional noise for the sedation monitoring of the patient.

[0047] In an example, the applied current has a high maximum current amplitude.

[0048] In an example, the waveform comprises a bipolar trapezoidal gradient waveform.

[0049] According to an example, the magnetic resonance imaging system comprises at least one gradient coil drive amplifier 40. The processing unit is configured to control one or more gradient coil drive amplifiers to drive one or more gradient coils to produce the intentional noise for the sedation monitoring of the patient.

[0050] According to an example, control of the gradient coil to produce intentional noise comprises utilization by the processing unit of audio relevant information about the patient.

[0051] In an example, the audio relevant information comprises an indication of a hearing capability of the patient.

[0052] In an example, the audio relevant information comprises information on hearing habits of the patient.

[0053] In an example, the audio relevant information comprises information on preferred types of music of the patient.

[0054] According to an example, the magnetic resonance imaging system is configured to acquire at least one patient response to the intentional noise for the sedation monitoring of the patient. The processing unit is configured to determine a sedation state of the patient comprising utilization of the at least one patient response to the intentional noise for the sedation monitoring of the patient.

[0055] In an example, the apparatus comprises an output unit configured to output the sedation state of the sedated patient.

[0056] In other words, a sedation level determination system is provided that can determine the sedation level of a patient for utilization in for example a medical scan procedure.

[0057] In an example, output unit can be used to adapt a medical scan procedure based on the responses.

[0058] According to an example, the magnetic resonance imaging system comprises at least one sensor device 50. The at least one sensor device is configured to acquire the at least one patient response to the intentional noise for the sedation monitoring of the patient.

[0059] In an example, the at least one sensor device comprises: a camera, an EMG sensor, a movement sensor, a tilt sensor, an accelerometer, a microphone, and the at least one sensor device can be the magnetic resonance image acquisition unit itself when operating in an image acquisition mode.

[0060] In an example, the at least one patient response comprises: face expression or expressions, eye blinks, body part movement.

[0061] According to an example, the processing unit is configured to control MR imaging such that image data acquired by the magnetic resonance imaging system is useable to determine the at least one patient response to the intentional noise for the sedation monitoring of the patient.

[0062] According to an example, the processing unit is configured to control and/or modify and/or alter a scan sequence on the basis of the determined sedation state of the patient.

[0063] According to an example, production of the intentional noise for sedation monitoring of a patient comprises the processing unit being configured to produce intentional noise in addition to a magnetic resonance imaging sequence.

[0064] According to an example, production of the intentional noise for sedation monitoring of a patient comprises the processing unit being configured to modify a magnetic resonance imaging sequence.

[0065] According to an example, modification of the magnetic resonance imaging sequence comprises an interruption of sequence steps.

[0066] In an example, sequence steps are interrupted in a rhythmic manner.

[0067] According to an example, production of the intentional noise for sedation monitoring of a patient comprises the processing unit being configured to re-order steps of a magnetic resonance imaging sequence.

[0068] According to an example, production of the intentional noise for sedation monitoring of a patient comprises the processing unit being configured to utilize a particularly loud scan sequence or part of a scan sequence.

[0069] From the above description, it is clear that the MRI system can be utilized in a method of sedation monitoring of a patient, where this method comprises controlling by a processing unit a gradient coil of the magnetic resonance imaging system to produce intentional noise for sedation monitoring of the patient.

[0070] In an example, the method comprises controlling by the processing unit control a waveform of a current applied to the gradient coil to produce the intentional noise for the sedation monitoring of the patient.

[0071] In an example, the magnetic resonance imaging system comprises at least one gradient coil drive amplifier. The method can then comprise controlling by the processing unit a gradient coil drive amplifier to drive the gradient coil to produce the intentional noise for the sedation monitoring of the patient.

[0072] In an example, controlling of the gradient coil to produce intentional noise comprises the processing unit utilizing audio relevant information about the patient.

[0073] In an example, the method comprises acquiring by the magnetic resonance imaging system at least one patient response to the intentional noise for the sedation monitoring of the patient. The method can then comprise determining by the processing unit a sedation state of the patient utilizing the at least one patient response to the intentional noise for the sedation monitoring of the patient.

[0074] In an example, the magnetic resonance imaging system comprises at least one sensor device. The method can then comprise using the at least one sensor device to acquire the at least one patient response to the intentional noise for the sedation monitoring of the patient.

[0075] In an example, the method comprises controlling by the processing unit MR imaging such that image data acquired by the magnetic resonance imaging system is useable to determine the at least one patient response to the intentional noise for the sedation monitoring of the patient.

[0076] In an example, the method comprises controlling and/or modifying and/or altering by the processing unit a scan sequence on the basis of the determined sedation state of the patient.

[0077] In an example, producing the intentional noise for sedation monitoring of a patient comprises the processing unit controlling the gradient coil to produce intentional noise in addition to a magnetic resonance imaging sequence.

[0078] In an example, producing the intentional noise for sedation monitoring of a patient comprises the processing unit controlling the gradient coil to modify a magnetic resonance imaging sequence.

[0079] In an example, modifying the magnetic resonance imaging sequence comprises interrupting sequence steps.

[0080] In an example, producing the intentional noise for sedation monitoring of a patient comprises the processing unit controlling the gradient coil to re-order steps of a magnetic resonance imaging sequence.

[0081] In an example, producing the intentional noise for sedation monitoring of a patient comprises the processing unit controlling the gradient coil to produce a particularly loud scan sequence or part of a scan sequence.

[0082] The following provides details relating to specific embodiments, and how an understanding of operational characteristics of MRI systems led to a development of such MRI systems to provide a new technique for sedation monitoring, making use of intentional noise generated by the MRI system itself.

[0083] MRI patients are routinely subjected to high sound pressure levels, averaging around 95-105 dB, for some MR pulse sequences increasing up to 130 dB. See for example Moelker. A. et al. Importance of Bone-Conducted Sound Transmission on Patient Hearing in the MR Scanner. J Magn Reson Imag 2005; 22:163-169. The noise is due to strong time-varying currents in the gradient coils required to realize the spatial resolution of MR imaging. Lorentz forces on these coils due to the main magnetic field produce the noise. Specifically, the waveform of the currents in the gradient coils (slew rate, maximum strength, shape) in combination with a characteristic scanner-specific transfer function directly determine the pitch, sound, and the noise level. Fast sequences usually require fast switching of gradients, thus, result in high noise levels. In general, MRI scanner noise depends on and varies considerably with the type of scan sequence (TSE, FFE, EPI, Spiral, Cardiac triggered sequences, DWI).

[0084] It was realised by the inventors that the noise produced by the gradient coils of the MRI system could itself be used for sedation monitoring. Standard MRI systems have three independent gradient coils X,Y,Z, and each coil consists of several coil parts connected in series so that all parts carry the same current are driven by one of the gradient coil amplifiers X,Y,Z. The inventors realised that the noise produced by these coils could be intentionally utilized for sedation monitoring a patient during an MRI scan, where parts of an MRI image acquisition unit could be utilized and with modifications further beneficial effects could be provided.

[0085] Therefore, the MR gradient systems have high fidelity amplifiers that can produce arbitrary current waveforms to be applied to the gradient coils. These waveforms are defined in the MR scan software, and the gradient coils can be driven to produce arbitrary sounds, and even to essentially use the MR gradients as a loudspeaker. Thus, these generated custom sounds are adapted to be useful as an audio stimulus for the measurement of sedation depth. Examples are short and loud beeps, or even a human voice addressing the patient. Frequencies may be used for the beeps where the human ear is particularly sensitive.

[0086] It was also realised by the inventors, that the MR scans can be modified such that they provide clearly hearable and characteristic sounds that gain the attention of a patient. For this purpose, the continuous pattern of noise of a standard sequence may be interrupted in a characteristic, e.g. rhythmic way as part of sedation monitoring. Additionally, because standard sequences vary considerably with respect to the loudness of MR noise during different parts of the scan, it was realised that different parts of a scan could be re-ordered as necessary, such that a particularly loud scans or parts of scans can be used as audio stimulus at an appropriate time point for example, without any modification of their waveforms.

[0087] With respect to the generation of intentional noise, the strong currents that are applied to the MR gradient coils to induce noise for sedation monitoring, such as a beep or beeps or synthetic human voice, can have waveforms of currents are interleaved with the waveforms of the scan sequence used for MRI.

[0088] FIG. 2 shows a schematic representation of the gradient coils for an MR imaging acquisition unit or scanner. Every gradient coil and coil part produces a characteristic magnetic field distribution that results from the spatial arrangement of the coil leads. These gradient coils (X,Y, or Z) can be used alone, or in combination, to produce the required noise for sedation monitoring.

[0089] The response of the patient to the intentional noise can be measured by a number of known methods. Examples are face expressions/eye blinks or other reflexes observed by cameras or sensors, or patient motion can be measured by suitable sensors or can be measured by the MRI system itself.

[0090] It is known that patient's hearing capabilities and responses to various types of audio stimuli varies considerably. Thus, the type of stimulus and its loudness to the patient can take into account the specific patient undergoing examination. In this respect, prior knowledge of hearing capabilities/disabilities and other information such as age, hearing habits, preferred types of music can be made use of.

[0091] Having monitored the patient, a known sedation depth, determined from the patient's response to the intentional noise, can be utilized to adapt the MR examination to avoid image artefacts. Specifically, the noise characteristics of MR imaging sequences can be changed, or at least the order in which they are executed during an MR examination may be changed. This is done such that patients who are awake or who are only mildly sedated are not subjected to very loud scans, which may cause patient motion and result in image artefacts. The adaptation of the MR sequence based on the sedation depth to avoid image artefacts can proceed as follows. Based on the progression of the sedation depth (shallow), the MR sequence can be adapted for a scan, such that noise stimulus is avoided to a patient who is awake in order not to disrupt the scan. This means that “identifying” specific noise level and converting into corresponding stimulus proportionate to the sedation depth level can be performed in such a way that stimulus is always lower for a specific sedation depth level. For example, if N1 level of noise is a stimulant for sedation depth D1, where a person will not wake-up for N1 noise. Then all the sequences that generates noise less than N1 level can be used.

[0092] To augment the monitoring of sedation of a patient, the intentional noise produced by the MRI system can form part of a multi-modal stimuli system that is used to monitor sedation of a patient. Thus, the MR noise can form one sensory stimulus, that can be combined with other sensory stimuli in order to provide a more reliable mechanism to determine the sedation state of the patient. The different stimuli can be provided simultaneously, to provide for an improved ability to determine the sedation state of the patient from how they respond to such congruent multimode stimuli. The different modes of stimuli can be applied in a similar manner, for example having similar or the same frequency waveforms, amplitude waveforms, and can target different sensory organs of the patient. Thus, the MRI system can generate intentional noise, and other stimulation devices are configured to provide stimuli including: mechanical haptic stimuli; TENS stimuli; visual stimuli; nerve and/or muscle stimuli via the Magnetic Resonance Imaging unit itself; questions posed via synthetic generated as part of the “noise” from the MRI system; taste stimuli; fragrance stimuli; balance related stimuli (rocking of the head for example). The sensors used to monitor the multi-modal stimulation can be the same as that used to monitor the patient who is being stimulated just be the MRI system intentionally generated noise. Thus, sensor device can includes one or more of: a camera, an EMG sensor, a movement sensor, a tilt sensor, an accelerometer, a microphone, and for the nerve and/or the Magnetic Resonance Imaging unit/system itself.

[0093] In another exemplary embodiment, a computer program or computer program element is provided that is characterized by being configured to execute the method steps of the method according to one of the preceding embodiments, on an appropriate system.

[0094] The computer program element might therefore be stored on a computer unit, which might also be part of an embodiment. This computing unit may be configured to perform or induce performing of the steps of the method described above. Moreover, it may be configured to operate the components of the above described apparatus and/or system. The computing unit can be configured to operate automatically and/or to execute the orders of a user. A computer program may be loaded into a working memory of a data processor. The data processor may thus be equipped to carry out the method according to one of the preceding embodiments.

[0095] This exemplary embodiment of the invention covers both, a computer program that right from the beginning uses the invention and computer program that by means of an update turns an existing program into a program that uses the invention.

[0096] Further on, the computer program element might be able to provide all necessary steps to fulfill the procedure of an exemplary embodiment of the method as described above.

[0097] According to a further exemplary embodiment of the present invention, a computer readable medium, such as a CD-ROM, USB stick or the like, is presented wherein the computer readable medium has a computer program element stored on it which computer program element is described by the preceding section.

[0098] A computer program may be stored and/or distributed on a suitable medium, such as an optical storage medium or a solid state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems.

[0099] However, the computer program may also be presented over a network like the World Wide Web and can be downloaded into the working memory of a data processor from such a network. According to a further exemplary embodiment of the present invention, a medium for making a computer program element available for downloading is provided, which computer program element is arranged to perform a method according to one of the previously described embodiments of the invention.

[0100] It has to be noted that embodiments of the invention are described with reference to different subject matters. In particular, some embodiments are described with reference to method type claims whereas other embodiments are described with reference to the device type claims. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters is considered to be disclosed with this application. However, all features can be combined providing synergetic effects that are more than the simple summation of the features.

[0101] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing a claimed invention, from a study of the drawings, the disclosure, and the dependent claims.

[0102] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items re-cited in the claims. The mere fact that certain measures are re-cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.