Patent Application
20150226816
This application claims the benefit of DE 102014202301.7, filed on Feb. 7, 2014, which is hereby incorporated by reference in its entirety.
The invention relates to magnetic resonance tomography.
When patients are being examined in a magnetic resonance tomograph, an exchange of information with the patient is frequently required. Patients are given instructions about holding their breath or the like. On the other hand, communication between the patient and other people may soothe anxieties and uncertainties, especially when a magnetic resonance tomograph with a relatively narrow bore is used. Transmission of acoustic information to a patient and from a patient is relatively complex however. On the one hand, hearing protection for patients, which attenuates acoustic signals, is frequently used during magnetic resonance tomography examinations. On the other hand, high magnetic fields may be attained in magnetic resonance tomography, which is why the use of sound transducers with permanent magnets is not possible. In addition, the use of long conducting structures without sheath current protection in a patient communication system may also be avoided in order to be compatible with a magnetic resonance tomograph.
Because of these factors, a compressed-air hose is typically used for communication with the patient. Sound waves are transmitted through the hose via the medium of air to a passive headset. However, these types of compressed-air hoses are frequently perceived as disruptive by patients and/or by operators.
The scope of the present invention is defined solely by the appended claims and is not affected to any degree by the statements within this summary.
The present embodiments may obviate one or more of the drawbacks or limitations in the related art. For example, the disclosed embodiments may provide a magnetic resonance tomograph with a component on which the head of a patient rests in a contact area during imaging. The disclosed embodiments may also provide a patient communication device for communicating information to the patient.
The patient communication device includes a control device and also an actuator assigned to the contact area. The actuator, on activation with electric control signals by the control device, imparts vibrations to the surface of the contact area.
Sound is transmitted to the patient by using the coupling of bone sound into a head bone of the patient instead of transmitting sound through air. In this method the actuator serves as a sound transducer. In contrast with a normal sound transducer, the actuator does not convert an electric signal into air pressure differences, but rather into vibrations that are coupled into the head bone of the patient. In order to achieve the best possible coupling-in, the coupling-in may occur in an area in which the bone is covered by minimal skin and/or tissue. Therefore, the patient may be supported such that the patient contacts the contact area with an area of the frontal bone and/or of the temporal bone, such as in the area of the mastoid process of the temporal bone.
In using bone sound, the sound vibrations through the bone are perceived while bypassing the outer and the middle ear. Therefore, a sound deadening mechanism used in magnetic resonance tomography to suppress noises developed by the gradient coils does not lead to an attenuation of the coupled-in sound. At the same time, with a coupling-in of bone sound, an acoustic perception is achieved that largely corresponds to that which may be perceived when hearing corresponding sound waves. The actuator may thus essentially be actuated with the same signals with which a loudspeaker may be controlled. In such cases, sound may be transmitted by the actuator over the entire range of human hearing, such as, for example, between 2 Hz and 30 kHz, and between 20 Hz and 20 kHz. In such cases, the frequency range typically used by speech may be transmitted, such as the range from 80 Hz to 12 kHz.
The patient communication device may include a microphone for picking up an information signal supplied to the actuator as a control signal by the control device. In some cases, the signal may be exclusively buffered or amplified by the control device. However, a preprocessing of the information signal may also be provided. Preprocessing may include analog-digital/digital-analog conversion, in which a filtering and/or a frequency compensation may be implemented.
As an alternative or in addition to the information signal being picked up via a microphone, the signal may also be digitally stored. In this case, corresponding information is selected through a control input of a user or a device controlling the examination, converted into an information signal and may be supplied to the actuator as a control signal. Such information may involve recorded voice information, however any other stimuli, such as low-frequency vibrations for example, may be transmitted in order to give instructions to the patient.
In this case, the component may be configured as a local coil carrier or a head support. The component may be a carrier of a head coil. A head support in this case provides a support and stabilization function for the head of the patient, such as to prevent a movement of the head during the examination. In such cases, the support may be made of plastic for example or of a sufficiently rigid foam cushion wedge.
The component may however also be configured as a fixing element for fixing the supported patient, for example as webbing or as a headset. The fixing element is disposed on the patient's head and initiates or facilitates a coupling to the head coil. The component may be a sound protection component, such as a sound protection headset that, for example, has additional support surfaces behind the ear that rest on the head surfaces and may be configured to vibrate by an actuator.
In order to provide simple cabling between the actuator and the control device, the magnetic resonance tomograph may include a multi-pin connector for connecting the head coil with a measurement and/or control device assigned to the head coil. The control signal for the actuator is routed through the connector. Connectors are used for easy coupling and uncoupling of local coils to a magnetic resonance tomograph. The connectors may be connected to the head coil via a cable. The connector may be arranged directly on the head coil. In such cases, a connector format may be specified for the connectors in which, when a head coil is used, one or more pins may be unassigned. Therefore one or more of these pins may be used for activating the actuator. In such cases, as well as a pin for a control signal, an additional pin for a ground connection of the actuator may be provided. The actuator and the head coil may also use a common ground. The use of a common connector for the actuator and the head coil on the one hand achieves simple cabling. On the other hand, shared sheath current protection for the measurement and/or control signals of the head coil and for the control signals of the actuator may be used in such cases.
As an alternative to the use of a separate pin, a common signal line may carry both a measurement or control signal of the head coil and also the control signal of the actuator. The common signal line may be used in cases in which the measurement or control signals of the head coil and the control signals of the actuator lie in different (e.g., markedly different) frequency ranges. In such cases measurement signals of a magnetic resonance tomograph typically lie in the megahertz range and audio signals with which the actuator is activated typically lie in the hertz or low kilohertz range. The frequency range of control signals for the head coil depends on the actual application.
For transmission over a common signal line the measurement or control signal of the head coil may be mixed in various ways with the control signal of the actuator. In one case the signals may be summed The signals may be separated by filters. As an alternative, mixing using non-linear mixing processes, for example, frequency or amplitude modulation with corresponding demodulation, may be used.
The actuator may be a piezoelectric actuator. Magnetic components may thus be avoided. In addition, piezoelectric actuators may have relatively small surfaces, such that a low induction of eddy currents in the magnetic resonance tomograph is to be expected. In this case the actuator may be formed from at least one piezoelectric layer disposed on at least one side on a membrane or a housing section of the component. The membrane or the housing section is bendable by a changing shape of the piezoelectric layer. This allows flexural vibrations of the membrane or of the housing section to be created. The excitation of the flexural vibration may be performed in such cases in accordance with the monomorphic or bimorphic principle, in which the piezoelectric layer contracts or expands depending on the control signal, while the expansion of the membrane or of the housing section remains essentially the same. This leads to the bending of the membrane or of the housing section. In order to amplify this effect a piezoelectric layer may be disposed on both sides of the membrane or of the housing section. The two piezoelectric layers are operated with different polarities, such that a control signal that leads to the expansion of one of these layers, leads to contraction of the other layer. Thus the two piezoelectric layers act together in order to create a bending. The use of a piezoelectric layer for bending a membrane or a housing section provides a flat actuator with a large stroke.
Actuators may be used in the contact area to detect information. The actuators may detect (e.g., pick up) vibrations and thus also bone sound caused by the patient speaking. The actuator or a further actuator disposed on the component may serve as a sensor for picking up vibrations as a measurement signal. The control device is configured to control a sound transducer as a function of the measurement signal. Thus a microphone function of the actuator, such as for picking up bone sound, is achieved. In this case the sound transducer may be external, e.g., outside the magnetic resonance tomograph or disposed at a distance from the magnetic resonance tomograph. The control device may be configured such that picking up the measurement signals is only undertaken at times at which no sound output, i.e. no output of control signals, is occurring.
If the separate lines are used for picking up the measurement signal from those used for transmission of the control signals to the actuator, the lines may be routed via the coil connector of a head coil. As described above for the control signals, this may be achieved both via one or more separate pins or also by mixing the signal with a measurement or control signal of the head coil.
A method is also provided for transfer of acoustic information to a patient in a magnetic resonance tomograph. A patient is supported in the magnetic resonance tomograph such that the head of the patient is in mechanical contact with the contact area of a component of the magnetic resonance tomograph. Information is transferred through the component by activation of an actuator by a patient communication device with an electric signal representing the information. In this case the patient may be supported such that his or her head is in contact with the contact area in the area of the frontal bone and/or of the temporal bone, such as in the area of the mastoid process of the temporal bone. The information may be detected (e.g., picked up) acoustically, such as by a microphone. In this case, as described above for the magnetic resonance tomograph, bidirectional communication may be achieved if the actuator is additionally used as a microphone for head sound. The method may be achieved using a magnetic resonance tomograph as described herein.
Disposed in the contact area 6 is an actuator not shown in
Information signals, such as voice inputs of a person, are picked up by the microphone 8. These are supplied by the control device 7 to the actuator. Accordingly the actuator vibrates such that the acoustic information picked up by the microphone 8 is transmitted as bone sound to the skull of the patient 4. The patient thus hears voice inputs that have been made at the microphone 8.
If the patient 4 himself or herself speaks, then the skull of the patient is made to vibrate by the speech of the patient 4, which in turn makes the actuator vibrate. While the actuator is not being controlled by a control signal, the control device 7 may therefore pick up the vibrations of the actuator as a measurement signal and activate the sound transducer 9, which is configured as a loudspeaker, in accordance with this measurement signal, in order to output at the loudspeaker speech of the patient 4 detected by the actuator.
In addition, a control element 10 is also provided on the magnetic resonance tomograph 1, with which an operator may retrieve acoustic information stored in the control device 7. The control element 10 may cause the information to be sent as control signals to the actuator. Thus for example previously recorded speech phrases or acoustic signals that do not represent speech may be reproduced.
The actuator 14 in this case includes a piezoelectric layer disposed on one side on a covering of the padding 13. By activation of the piezoelectric layer with tensions a flexural vibration of the cover may be created which, depending on the control signals of the control device 7, transmits vibrations to the head 15 of the patient. If the actuator 14 is activated with control signals that describe acoustic signals, then the signals are transmitted via the skull of the patient by bone conduction, which makes the audio information audible to the patient.
The further structure of the patient communication device corresponds to the structure in accordance with
Both in
As an alternative, a shared signal line may be used both for the control signal of the actuator 14 and also for the measurement signal of the head coil 17. In this case corresponding filters for signal separation may be provided on the connector 19 and on the connector 18.
It is to be understood that the elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent, and that such new combinations are to be understood as forming a part of the present specification.
While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications may be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102014202301.7 | Feb 2014 | DE | national |
