Patent Publication Number: US-2023164471-A1

Title: Magnetic-Resonance Compatible Earphone, Magnetic-Resonance Compatible Intercom System and Head Coil Apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to and the benefit of China patent application no. CN 202111415536.6, filed on Nov. 25, 2021, the contents of which are incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The disclosure relates to an earphone and, in particular, to a magnetic-resonance compatible earphone, as well as a magnetic-resonance compatible intercom system and head coil apparatus comprising the same. 
     BACKGROUND 
     Magnetic resonance imaging (MRI) is a medical imaging technology that can be used to diagnose diseases. When an examination subject is located in the detection region of a magnetic resonance imaging system and undergoing examination, the operator needs to issue action instructions to the examination subject through an intercom system. However, traditional earphones (such as moving coil or moving iron earphones) do not meet the compatibility requirements of the main magnetic field and RF magnetic field of magnetic resonance due to the inclusion of permanent magnet components. 
     SUMMARY 
     An object of the present disclosure is to provide a magnetic-resonance compatible earphone having magnetic resonance compatibility. Another object of the present disclosure is to provide a magnetic-resonance compatible intercom system having magnetic resonance compatibility. Still another object of the present disclosure is to provide a head coil apparatus that has the function of an earphone having magnetic resonance compatibility. 
     The disclosure provides a magnetic-resonance compatible earphone comprising an earphone body, a diaphragm, and a drive coil. The diaphragm is arranged on the earphone body and configured to generate sound through vibration. The drive coil is arranged on the earphone body and configured to receive audio current. The drive coil that has received the audio current is configured to generate a Lorentz force under the action of a main magnetic field of a magnetic resonance imaging system. The drive coil is configured to drive the diaphragm to vibrate by means of the Lorentz force generated by the drive coil. 
     The magnetic-resonance compatible earphone utilizes the main magnetic field of the magnetic resonance imaging system to cause the drive coil to generate a Lorentz force, thereby driving the diaphragm to vibrate. The magnetic-resonance compatible earphone does not need to use permanent magnet components, and has good magnetic resonance compatibility. 
     In another embodiment of the magnetic-resonance compatible earphone, the magnetic-resonance compatible earphone further comprises an elastic sheet and a transmission member. The elastic sheet is provided on the earphone body. The drive coil is fixed to the elastic sheet. The drive coil is configured to drive the elastic sheet to elastically deform by means of the Lorentz force generated by the drive coil. The transmission member connects the elastic sheet and the diaphragm. The elastic sheet is configured to drive the transmission member to move through elastic deformation. The moving transmission member is configured to drive the diaphragm to vibrate. This structure is simple, with good stability. 
     In yet another embodiment of the magnetic-resonance compatible earphone, the elastic sheet is in the form of a sheet and arranged perpendicular to an output direction. An edge of the elastic sheet is fixed to the earphone body. The elastic sheet has a connecting portion, the connecting portion being configured to move in a direction parallel to the output direction as the elastic sheet deforms elastically. The transmission member extends in the output direction, having one end connected to the connecting portion and another end connected to the diaphragm. This structure is simple, with good stability. 
     In a further embodiment of the magnetic-resonance compatible earphone, the drive coil has at least one annular winding unit. The winding unit is wound along a plane perpendicular to the output direction. One end of the winding unit is disposed in a set (i.e. predetermined) magnetic field direction perpendicular to the output direction, which is fixed to the connecting portion, and the winding unit extends toward the edge of the elastic sheet in a direction parallel to the set magnetic field direction. This structure is simple and easy to process. 
     In yet another embodiment of the magnetic-resonance compatible earphone, the drive coil has at least one pair of winding units. The pair of winding units are arranged as mirror images (i.e. symmetrically) across a plane perpendicular to the set magnetic field direction. Audio currents flow in opposite directions in the pair of winding units, so that the directions of the forces acting on the connecting portion are the same. 
     In yet another embodiment of the magnetic-resonance compatible earphone, the pair of winding units is formed by continuously winding a length of conductive wire. This allows induced potentials generated under gradient magnetic fields to cancel each other out. 
     In yet another embodiment of the magnetic-resonance compatible earphone, the diaphragm and the drive coil are integrated as a flexible circuit board. The overall structure can thereby be made more compact. 
     The present disclosure also provides a magnetic-resonance compatible intercom system comprising a sound receiving unit and a sound transmitting unit. The sound receiving unit comprises a microphone, a first audio codec, and a first audio processor. The microphone is configured to convert a sound signal into an analog signal. The first audio codec is configured to generate a digital signal based on the analog signal generated by the microphone. The first audio processor is configured to generate an output signal based on the digital signal generated by the first audio codec. The sound transmitting unit comprises a second audio processor, a second audio codec, and a magnetic-resonance compatible earphone as described above. The second audio processor is configured to generate an input signal based on the output signal generated by the first audio processor. The second audio codec is configured to generate an analog signal based on the input signal. The magnetic-resonance compatible earphone is configured to emit sound according to the analog signal generated by the second audio codec. The magnetic-resonance compatible earphone of the magnetic-resonance compatible intercom system utilizes the main magnetic field of the magnetic resonance imaging system to cause the drive coil to generate a Lorentz force, thereby driving the diaphragm to vibrate. The magnetic-resonance compatible earphone does not need to use permanent magnet components, so the magnetic-resonance compatible intercom system has good magnetic resonance compatibility. 
     In another embodiment of the magnetic-resonance compatible intercom system, the magnetic-resonance compatible intercom system further comprises a first wireless communication module and a second wireless communication module. The first wireless communication module is connected to the first audio processor. The second wireless communication module is connected to the second audio processor. The first audio processor and the second audio processor are configured to transmit signals by wireless communication via the first wireless communication module and the second wireless communication module. This enables wireless intercom functionality. 
     In yet another embodiment of the magnetic-resonance compatible intercom system, the sound transmitting unit further comprises a noise reduction module. The noise reduction module is configured to collect ambient noise and convert the ambient noise into a digital signal. The noise reduction module is connected to the second audio processor. The second audio processor is configured to generate the input signal based on the digital signal generated by the noise reduction module, so that the magnetic-resonance compatible earphone can emit a sound wave with the same amplitude as but opposite phase to the ambient noise. This enables active noise reduction. 
     In yet another embodiment of the magnetic-resonance compatible intercom system, the sound transmitting unit further comprises a constant-current audio amplifier. The constant current audio amplifier has an input end connected to the second audio codec and an output end connected to the magnetic-resonance compatible earphone. This enables interference from induced currents caused by gradient magnetic fields to be effectively reduced. 
     The present disclosure also provides a head coil apparatus comprising a body, two airbags, and two magnetic-resonance compatible earphones as described above. The body is used for accommodating an examination subject&#39;s head and for receiving magnetic resonance signals of the examination subject&#39;s head. The two airbags are provided on the body and respectively correspond to the two ears of the examination subject. Each one of the magnetic-resonance compatible earphones is connected to one of the air bags and used to transmit sound to the examination subject&#39;s ear. The airbag is configured to be inflated and deflated to adjust the distance between the magnetic-resonance compatible earphone and the examination subject&#39;s ear. This arrangement not only realizes the function of immobilizing the examination subject&#39;s head, but also that of the magnetic-resonance compatible earphone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings below illustrate and explain the present disclosure schematically, without limiting the scope thereof. 
         FIG.  1    is an example structural diagram of a magnetic-resonance compatible earphone, in accordance with an embodiment of the present disclosure. 
         FIG.  2    illustrates an example drive coil of the magnetic-resonance compatible earphone shown in  FIG.  1   , in accordance with an embodiment of the present disclosure. 
         FIG.  3    illustrates another example drive coil, in accordance with an embodiment of the present disclosure. 
         FIG.  4    illustrates an example structural diagram of another magnetic-resonance compatible earphone, in accordance with an embodiment of the present disclosure. 
         FIG.  5    illustrates an example structural block diagram of a magnetic-resonance compatible intercom system, in accordance with an embodiment of the present disclosure. 
         FIG.  6    illustrates an example structural diagram of a head coil apparatus, in accordance with an embodiment of the present disclosure. 
     
    
    
     KEY TO LABELS 
     
         
         
           
               10  headphone body 
               20  diaphragm 
               30  drive coil 
               31  winding unit 
               40  elastic sheet 
               41  connecting portion 
               50  transmission member 
               60  body 
               70  airbag 
               75  headrest 
               80  sound receiving unit 
               81  microphone 
               82  first audio codec 
               83  first audio processor 
               84  first wireless communication module 
               90  sound transmitting unit 
               91  second audio processor 
               92  second audio codec 
               93  second wireless communication module 
               94  noise reduction module 
               95  constant-current audio amplifier 
               100  magnetic-resonance compatible headphone 
             F 1  output direction 
             F 2  set magnetic field direction. 
           
         
       
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     To enable a clearer understanding of the technical features, objectives, and effects of the disclosure, particular embodiments of the present disclosure are now explained with reference to the accompanying drawings, in which identical labels indicate structurally identical components or components with similar structures but identical functions. 
     As used herein, “schematic” means “serving as an instance, example or illustration”. No drawing or embodiment described herein as “schematic” should be interpreted as a more preferred or more advantageous technical solution. 
     As used herein, “first” and “second”, etc. do not indicate order or degree of importance, etc., merely being used to indicate a distinction between parts, to facilitate document descriptions. 
     To make the drawings appear uncluttered, only those parts relevant to the present disclosure are shown schematically in the drawings; they do not represent the actual structure thereof as a product. 
       FIG.  1    is an example structural diagram of a magnetic-resonance compatible earphone, in accordance with an embodiment of the present disclosure. As shown in  FIG.  1   , the magnetic-resonance compatible earphone  100  comprises an earphone body  10 , a diaphragm  20 , and a drive coil  30 . 
     The diaphragm  20  is disposed on the earphone body  10  and is configured to generate sound through vibration. The drive coil  30  is disposed on the earphone body  10  and is configured to receive audio current. The drive coil  30  that has received the audio current is configured to generate a Lorentz force under the action of the main magnetic field of the magnetic resonance imaging system. The drive coil  30  is configured to drive the diaphragm  20  to vibrate by means of the Lorentz force generated by the drive coil. 
     Specifically, and as shown in  FIG.  1   , in this embodiment the magnetic-resonance compatible earphone  100  further comprises an elastic sheet  40  and a transmission member  50 . The elastic sheet  40  is disposed on the earphone body  10 . The drive coil  30  is fixed to the elastic sheet  40 . The drive coil  30  is configured to drive the elastic sheet  40  to elastically deform by means of the Lorentz force generated by the drive coil. The transmission member  50  connects the elastic sheet  40  and the diaphragm  20 . The elastic sheet  40  is configured to drive the transmission member  50  to move through elastic deformation. The moving transmission member  50  is configured to drive the diaphragm  20  to vibrate. 
     Further, and as shown in  FIG.  1    and  FIG.  2   , in this embodiment, the elastic sheet  40  is in the form of a sheet and is arranged perpendicular to an audio output direction F 1 . The elastic sheet  40  is, for example, in the form of a circular sheet or rectangular sheet. An edge of the elastic sheet  40  is fixed to the earphone body  10 . The elastic sheet  40  has a connecting portion  41  (for the convenience of description, the connecting portion  41  is schematically circled by a dotted line in the figure, but this is not used to limit the present disclosure). The connecting portion  41  can move in a direction parallel to the output direction F 1  as the elastic sheet  40  deforms elastically. The transmission member  50  extends in the output direction F 1 , having one end connected to the connecting portion  41  and another end connected to the diaphragm  20 . 
     In the present embodiment, the drive coil  30  has several pairs of winding units  31 , which are stacked in the output direction F 1 ; only one of these pairs of winding units  31  is shown in  FIG.  2    by way of example and not limitation. Each winding unit  31  is wound along a plane perpendicular to the output direction F 1 . One end of the winding unit  31  in a set of winding units is fixed to the connecting portion  41 . The magnetic field direction F 2  is perpendicular to the output direction F 1 , and the winding unit  31  extends toward the edge of the elastic sheet  40  in a direction parallel to the set magnetic field direction F 2 . A pair of winding units  31  are arranged as mirror images (i.e. symmetrically arranged) across a plane perpendicular to the set magnetic field direction F 2 . Audio currents flow in opposite directions in the pair of winding units  31 ; i.e. in  FIG.  2   , one audio current is clockwise and the other audio current is counterclockwise. 
     In use, the set magnetic field direction F 2  may be roughly parallel to the direction of the main magnetic field of the magnetic resonance imaging system, and the winding unit  31  that has received the audio current generates a Lorentz force parallel to the output direction F 1  under the action of the main magnetic field of the magnetic resonance imaging system. Since the Lorentz forces generated by two ends of the winding unit  31  in the set magnetic field direction F 2  are in opposite directions, these act to drive the connecting portion  41  to move in a direction parallel to the output direction F 1 , thereby causing the elastic sheet  40  to deform elastically, and in turn driving the diaphragm  20  to vibrate by means of the transmission member  50  to emit sound corresponding to the audio current. 
     The magnetic-resonance compatible earphone uses the main magnetic field of the magnetic resonance imaging system to cause the drive coil  30  to generate a Lorentz force, thereby driving the diaphragm to vibrate. The magnetic-resonance compatible earphone does not need to use permanent magnet components, and has good magnetic resonance compatibility. 
     In other embodiments, the drive coil  30  may be provided with only one pair of winding units  31  as required. 
     In the present embodiment, since the audio currents flow in opposite directions in the pair of winding units  31 , the directions of the forces which they exert on the connection portion are the same. However, this is by way of example and not limitation. In other embodiments, the drive coil  30  may be provided with only one winding unit  31  as needed. 
     In the present embodiment, the pair of winding units  31  are respectively formed by winding two lengths of conductive wire (these two lengths of conductive wire will eventually be connected in series). However, this is by way of example and not limitation. In other schematic embodiments, as shown in  FIG.  3   , the pair of winding units  31  can also be formed by continuous winding of one length of conductive wire, the winding path thereof being similar to the writing of the number “8”. This allows for induced potentials that are generated under gradient magnetic fields to cancel each other out. 
       FIG.  4    illustrates an example structural diagram of another magnetic-resonance compatible earphone, in accordance with an embodiment of the present disclosure. As shown in FIG.  4 , in this embodiment the magnetic-resonance compatible earphone  100  comprises an earphone body  10 , a diaphragm  20 , and a drive coil  30 . 
     The diaphragm  20  and the drive coil  30  are integrated as a flexible circuit board and disposed on the earphone body  10 . The diaphragm  20  comprises a flexible substrate of the flexible circuit board, and is configured to generate sound through vibration. The drive coil  30  comprises a circuit in the flexible circuit board, and is configured to receive audio current. Having received the audio current, the drive coil  30  is configured to generate a Lorentz force under the action of the main magnetic field of the magnetic resonance imaging system. The drive coil  30  is configured to drive the diaphragm  20  to vibrate by means of the Lorentz force generated by the drive coil. This structure is more compact. 
       FIG.  5    illustrates an example structural block diagram of a magnetic-resonance compatible intercom system, in accordance with an embodiment of the present disclosure. As shown in  FIG.  5   , the magnetic-resonance compatible intercom system comprises a sound receiving unit  80  (e.g. a sound receiver) and a sound transmitting unit  90  (e.g. a sound transmitter). 
     The sound receiving unit  80  comprises a microphone  81 , a first audio codec  82 , and a first audio processor  83 . The microphone  81  is configured to convert a sound signal into an analog signal. The first audio codec  82  is configured to generate a digital signal based on the analog signal generated by the microphone  81 . The first audio processor  83  is configured to generate an output signal based on the digital signal generated by the first audio codec  82 . 
     The sound transmitting unit  90  comprises a second audio processor  91 , a second audio codec  92 , and a magnetic-resonance compatible earphone  100  as shown in  FIG.  1    or  FIG.  4   . The second audio processor  91  is configured to generate an input signal based on the output signal generated by the first audio processor  83 . The second audio codec  92  is configured to generate an analog signal based on the input signal. The magnetic-resonance compatible earphone  100  is configured to emit sound according to the analog signal generated by the second audio codec  92 . 
     In use, the sound receiving unit  80  is, for example, located outside the detection region of the magnetic resonance imaging system, and has no magnetic resonance compatibility requirements. The second audio processor  91  and second audio codec  92  of the sound transmitting unit  90  are, for example, disposed on the earphone body  10  of the magnetic-resonance compatible earphone  100 , and are, for example, located in the detection region of the magnetic resonance imaging system when in use. 
     The magnetic-resonance compatible earphone of the magnetic-resonance compatible intercom system utilizes the main magnetic field of the magnetic resonance imaging system to cause the drive coil to generate a Lorentz force, thereby driving the diaphragm to vibrate. The magnetic-resonance compatible earphone does not need to use permanent magnet components, so the magnetic-resonance compatible intercom system has good magnetic resonance compatibility. 
     As shown in  FIG.  5   , in an embodiment, the magnetic-resonance compatible intercom system further comprises a first wireless communication module  84  (e.g. wireless communication circuitry) and a second wireless communication module  93  (e.g. wireless communication circuitry). The first wireless communication module  84  is connected to the first audio processor  83 . The second wireless communication module  93  is connected to the second audio processor  91 . The first audio processor  83  and the second audio processor  91  are configured to transmit signals by wireless communication via the first wireless communication module  84  and the second wireless communication module  93 . This enables wireless intercom functionality. The second wireless communication module  93  is provided, for example, on the earphone body  10  of the magnetic-resonance compatible earphone  100 . 
     As shown in  FIG.  5   , in an embodiment, the sound transmitting unit  90  further comprises a noise reduction module  94  (e.g. noise reduction circuitry). The noise reduction module  94  is configured to collect ambient noise and convert the ambient noise into a digital signal. The noise reduction module  94  is connected to the second audio processor  91 . The second audio processor  91  is configured to generate an input signal according to the digital signal generated by the noise reduction module  94 , so that the magnetic-resonance compatible earphone  100  emits a sound wave with the same amplitude as but opposite phase to the ambient noise. This enables active noise reduction. 
     As shown in  FIG.  5   , in an embodiment, the sound transmitting unit  90  further comprises a constant-current audio amplifier  95 . An input end of the constant-current audio amplifier  95  is connected to the second audio codec  92 , and an output end is connected to the magnetic-resonance compatible earphone  100 . Since the constant-current audio amplifier  95  uses current as negative feedback, the constant-current audio amplifier  95  can effectively reduce interference from induced currents caused by gradient magnetic fields. 
     In other embodiments, a battery may also be provided in the sound receiving unit  80  and/or the sound transmitting unit  90  to provide electrical energy, or a crystal oscillator may be provided in the sound receiving unit  80  and/or the sound transmitting unit  90  to improve the signal stability. 
       FIG.  6    illustrates an example structural diagram of a head coil apparatus, in accordance with an embodiment of the present disclosure. As shown in  FIG.  6   , the head coil apparatus comprises a body  60 , two airbags  70 , and two magnetic-resonance compatible earphones  100  as shown in  FIG.  1    or  FIG.  4   . The body  60  is used for accommodating the examination subject&#39;s head and receiving magnetic resonance signals of the examination subject&#39;s head. The two airbags  70  are disposed on the body  60  and correspond to the two ears of the examination subject, respectively. Each magnetic-resonance compatible earphone  100  is connected to one airbag  70 , and is used to transmit sound toward the examination subject&#39;s ear. The airbag  70  can be inflated and deflated to adjust the distance between the magnetic-resonance compatible earphone  100  and the examination subject&#39;s ear, so as to immobilize the examination subject&#39;s head by a squeezing action. The airbag  70  may be, for example, an extending/retracting airbag. Such a design not only realizes the function of immobilizing the examination subject&#39;s head, but also provides the functionality of the magnetic-resonance compatible earphone described above. 
     In a schematic embodiment, the head coil apparatus further comprises, for example, a pair of headrests  75  for assisting in immobilizing the examination subject&#39;s head. 
     It should be understood that although the description herein is based on various embodiments, it is by no means the case that each embodiment contains just one independent technical solution. Such a method of presentation is adopted herein purely for the sake of clarity. Those skilled in the art should consider the description in its entirety. The technical solutions in the various embodiments could also be suitably combined to form other embodiments understandable to those skilled in the art. 
     The series of detailed explanations set out above are merely particular explanations of feasible embodiments of the present disclosure, which are not intended to limit the scope of protection thereof. All equivalent embodiments or changes made without departing from the artistic spirit of the present disclosure, such as combinations, divisions or repetitions of features, shall be included in the scope of protection of the present disclosure. 
     The various components described herein may be referred to as “units,” “apparatuses,” or “modules”. Such components may be implemented via any suitable combination of hardware and/or software components as applicable and/or known to achieve the intended respective functionality. This may include mechanical and/or electrical components, processors, processing circuitry, or other suitable hardware components, in addition to or instead of those discussed herein. Such components may be configured to operate independently, or configured to execute instructions or computer programs that are stored on a suitable computer readable medium. Regardless of the particular implementation, such devices, units, and facilities, as applicable and relevant, may alternatively be referred to herein as “circuitry,” “processors,” or “processing circuitry,” or alternatively as noted herein.