GB2586596A

GB2586596A - Headphones for an MR device

Info

Publication number: GB2586596A
Application number: GB1912074.0A
Authority: GB
Inventors: Alexis Henrik
Original assignee: Elekta Ltd
Current assignee: Elekta Ltd
Priority date: 2019-08-22
Filing date: 2019-08-22
Publication date: 2021-03-03
Anticipated expiration: 2039-08-22
Also published as: GB201912074D0; GB2586596B

Abstract

A wearable head device for use within a treatment volume of a magnetic resonance linear accelerator machine, the head device comprising: at least one ear cup 210 comprising a cup wall 212 having internal and external surfaces 214,216 defining a cup wall thickness therebetween that’s equal to, or less than, 3mm. Preferably the internal surface 214 is shaped such that a hollow cavity 218 is formed between the cup wall 212 and a wearer. Cup wall 212 may comprises a perimeter region around an end of the cup wall 212, the perimeter region having a cushion material 240 that forms an acoustic seal between the wearer and perimeter region. Cup wall 212 may be formed of a synthetic fibre material that’s possibly glass fibre or Kevlar®. Cup wall 212 may have a density equal, or less than, 2kg/dm3. The head device may comprise two ear cups connected by a strap 230, the strap 230 comprising internal and external surfaces defining a strap thickness therebetween, which may be equal, or less than, 3mm. The head device may further comprise a hollow communication tube 251 connected to the at least one ear cup 210 providing an air communication pathway to a wearer.

Description

Intellectual Property Office Application No. GII1912074.0 RTM Date:21 January 2020 The following terms are registered trade marks and should be read as such wherever they occur in this document: Kevlar Intellectual Property Office is an operating name of the Patent Office www.gov.uk /ipo Headphones for an MR device This disclosure relates to radiotherapy apparatus, and in particular to headphones for a patient undergoing treatment in a radiotherapy apparatus.

Background

Radiotherapy can be described as the use of ionising radiation, such as X-rays, to treat a human or animal body. Radiotherapy is commonly used to treat tumours within the body of a patient or subject. In such treatments, ionising radiation is used to irradiate, and thus destroy or damage, cells which form part of the tumour.

A radiotherapy device typically comprises a gantry that supports a beam generation system which is rotatable around a patient. For example, for a linear accelerator (linac) device, the beam generation system may comprise a source of radio frequency energy, a source of electrons, an accelerating waveguide, beam shaping apparatus, etc. During treatment of a patient, a healthcare professional, typically located in a different room from the radiotherapy device, may need to communicate with the patient. For example, a healthcare professional may need to communicate instructions or provide reassurance to the patient during treatment. In addition, the patient may be subjected to noise requiring ear protection, for example when a magnetic resonance (MR) scanner is used for imaging. Moreover, a patient may wish to hear a sound recording, such as music, during treatment to alleviate anxiety or boredom.

Conventionally, headphones can be used by a patient in a treatment apparatus, such as an MR scanner, which allows music to be played to the patient, protects the patient's ears, and allows a healthcare professional to communicate with the patient.

Headphones for use by patients need to be designed to be compatible with the relevant treatment apparatus. For example, a known headset for use with an MR imaging scanner employs air tubes for communicating sound to the patient's ears, since conventional metal wires would be visible to the MR imaging scanner, and thus adversely affect the imaging. In addition, substantial cushioning is provided in ear cups around the patient's ears to achieve the necessary ear protection from the noise from the MR imaging scanner, which may be up to 130 dB. This leads to bulky ear cups.

However, the known headphones for use with an MR imaging scanner are not suitable for use with a radiotherapy device such as a linac device, especially (although not exclusively) when treating the patient's head. In particular, the headset is made from a number of different materials having different shapes and thicknesses, and the known designs present sharp edges between the different materials. This makes it difficult to plan the therapeutic radiation dose to be delivered by the linac device from different positions, and thus in different beam directions, around the patient. In particular, different materials and thicknesses are presented by the headset in the path of the beam dependent up the beam direction. These different materials and thicknesses attenuate the therapeutic radiation differently. Such differences in attenuation of the beam are challenging to model accurately in order to define a treatment plan. In addition, any sharp edges between different materials or parts of the headset may be noticeable in the MR signal of an MR imaging scanner during imaging of the head. Furthermore, the bulky design of the headset is not compatible with a head restraint, such as a mask, that is used during treatment of the head to keep the patient's head in the desired position without movement.

The present invention seeks to address these and other disadvantages encountered in the prior art.

Summary

Aspects of the present disclosure are defined in the appended independent claims.

In accordance with an aspect, a wearable head device is provided. The wearable head device is suitable for use by a patient within a treatment volume of a magnetic resonance linear accelerator (MR linac) machine, which exposes the treatment volume, in use, to therapeutic radiation and a magnetic field. The wearable head device comprises at least one ear cup comprising a cup wall. The cup wall has an internal surface and an external surface defining a cup wall thickness therebetween.

The cup wall thickness is substantially equal to or less than 3 mm.

Since the cup wall has a thickness substantially equal to or less than 3 mm, attenuation of the therapeutic radiation beam of the MR Linac machine is reduced. For example, attenuation may be substantially less than or equal to 2.5%. This facilitates planning of the radiation dose delivered by the MR linac machine to the patient during treatment.

The cup wall thickness may be substantially uniform. For example, the variation in thickness of the cup wall is less than 7.5%. Thus, attenuation of the therapeutic radiation beam is substantially the same for beams travelling from different positions, and thus in different directions, around the patient and passing through the ear cup.

The external surface of the at least one ear cup may have a substantially constant curvature. Thus, the ear cup does not produce sharp gradients or visible edges in the MR signal during imaging by the

magnetic field.

The cup wall may be formed of a material that has low attenuation of the therapeutic radiation beam. For example, the cup wall may be formed of a synthetic fibre material, such as glass fiber or Kevlar. The density of the material of the cup wall may be substantially equal to or less than 2 kg/dm 3.

The internal surface of the at least one ear cup is shaped such that, in use, a hollow cavity is formed between the cup wall and the wearer of the head device. For example, the internal surface may be concave. Thus, sound can be conveyed into the hollow cavity and heard by the patient, allowing the patient to listen to a sound recording, such as music, or voice communication from a healthcare professional.

A cushioning material may be arranged around a perimeter region of the cup wall. The perimeter cushion, in use, is arranged to form an acoustic seal between the wearer and the perimeter region of the cup wall. The cushioning material of the perimeter cushion may be a low density foam. For example, the density of the cushioning material may be substantially equal to or less than 0.5 kg/dm3. For example, the cushioning material may have a density of 0.1 kg/dm3 (100 kg/m3). Thus, the perimeter cushion ensures an acoustic seal around the patient's ear, which provides ear protection from external noise from the MR linac machine.

In embodiments, the wearable head device comprises two ear cups connected by a strap. Thus, the wearable head device forms a stereo headset, wherein, in use, the ear cups cover respective ones of the patient's ears and are held in place by the strap arranged around the top of the patient's head.

The strap may comprise an internal strap surface, arranged to be placed around the wearer's head, and an external strap surface, the internal strap surface and external strap surface defining a strap thickness therebetween. The strap thickness may be substantially equal to or less than 3 mm. Thus, attenuation of the therapeutic radiation beam is reduced. For example, attenuation may be substantially less than or equal to 2.5%. The strap wall may be formed of the same material as the cup walls of the ear cups. The strap wall thickness may be substantially uniform. For example, the variation in thickness of the strap is less than 7.5%. Thus, attenuation of the therapeutic radiation beam is substantially the same for different beam directions passing through the strap. The external surface of the strap may have a substantially continuous curvature with the external surfaces of the cup walls of the ear cups.

A hollow communication tube may be connected to the at least one ear cup. The hollow communication provides an air communication pathway for sound to the wearer of the wearable head device. An aperture may be provided in the at least one ear cup. The aperture may be in communication with the hollow communication tube. The hollow communication tube may be formed of foam with a central cavity or hole to provide an air tube for the communication of sound.

Further features and advantages of embodiments will be appreciated from the following detailed description with reference to the accompanying drawings.

Figures Specific embodiments are now described, by way of example only, with reference to the drawings, in which: Figure 1 depicts a radiotherapy device or apparatus according to the present disclosure; Figure 2 is a perspective view of a wearable head device according to an embodiment; Figure 3 is a cross section of the wearable head device taken along the line X -X of Figure 2, and Figure 4 is a cross section of the wearable head device taken along the line Y Y of Figure 2.

Detailed Description

Figure 1 depicts a radiotherapy device suitable for delivering, and configured to deliver, a beam of radiation to a patient during radiotherapy treatment. The device and its constituent components will be described generally for the purpose of providing useful accompanying information for the present invention. The device depicted in figure 1 is in accordance with the present disclosure and is suitable for use with the disclosed systems and apparatuses. While the device in figure 1 is a magnetic resonance linear accelerator (MR linac), the implementations of the present disclosure may be any radiotherapy device, for example a linear accelerator (linac) device.

The device depicted in figure 1 is an MR-linac. The device comprises both magnetic resonance (MR) imaging apparatus 112 and radiotherapy (RT) apparatus which may comprise a linac device. In operation, the MR scanner produces MR images of the patient, and the linac device produces and shapes a beam of radiation and directs it toward a target region within a patient's body in accordance with a radiotherapy treatment plan. The depicted device does not have the usual 'housing' which would cover the MR imaging apparatus 112 and RT apparatus in a commercial setting such as a hospital.

The MR-linac device depicted in figure 1 comprises a source of radiofrequency waves 102, a circulator or other form of RF waveguide 118" a source of electrons such as an electron gun 106, an electron waveguide 104, a collimator 108 such as a multi-leaf collimator configured to collimate and shape the beam, MR imaging apparatus 112, and a patient support surface 114. Together, the source of RF 102, the circulator 118, the electron gun 106, the waveguide 108 and a target such as a heavy metal target (not shown) may be referred to as a beam generation apparatus, beam generation system, or a source of radiation. Alternative configurations and sources of radiation will be known to the skilled person and may be used in conjunction with the methods and devices

described in this disclosure.

The device also comprises a housing which, together with the ring-shaped gantry defines a bore. The moveable support surface 114 can be used to move a patient, or other subject, into the bore when an MR scan and/or when radiotherapy is to commence. The MR imaging apparatus 112, RT apparatus, and a subject support surface actuator are communicatively coupled to a controller or processor. The controller is also communicatively coupled to a memory device comprising computer-executable instructions which may be executed by the controller.

The RT apparatus comprises a source of radiation and a radiation detector (not shown). Typically, the radiation detector is positioned diametrically opposed to the radiation source. The radiation detector is suitable for, and configured to, produce radiation intensity data. In particular, the radiation detector is positioned and configured to detect the intensity of radiation which has passed through the subject. The radiation detector may also be described as radiation detecting means, and may form part of a portal imaging system.

The radiation source defines the point at which the treatment beam 110 is introduced into the bore. The radiation source is attached to the rotatable gantry 116 so as to rotate with the gantry 116. In this way, the radiation source is rotatable around the patient so that the treatment beam 110 can be applied from different angles around the gantry 116. In a preferred implementation, the gantry is continuously rotatable. In other words, the gantry can be rotated by 360 degrees around the patient, and in fact can continue to be rotated past 360 degrees. The gantry may be ring-shaped. In other words, the gantry may be a ring-gantry.

The source 102 of radiofrequency waves, such as a magnetron, is configured to produce radiofrequency waves. The source 102 of radiofrequency waves is coupled to the waveguide 104 via circulator 118, and is configured to pulse radiofrequency waves into the waveguide 104. Radiofrequency waves may pass from the source 102 of radiofrequency waves through an RF input window and into an RF input connecting pipe or tube. A source of electrons (not shown), such as an electron gun 106, is also coupled to the waveguide 104 and is configured to inject electrons into the waveguide 104. In the source of electrons, electrons are thermionically emitted from a cathode filament as the filament is heated. The temperature of the filament controls the number of electrons injected. The injection of electrons into the waveguide 104 is synchronised with the pumping of the radiofrequency waves into the waveguide 104. The design and operation of the radiofrequency wave source 102, electron source and the waveguide 104 is such that the radiofrequency waves accelerate the electrons to very high energies as the electrons propagate through the waveguide 104.

The design of the waveguide 104 depends on whether the linac accelerates the electrons using a standing wave or travelling wave, though the waveguide typically comprises a series of cells or cavities, each cavity connected by a hole or 'iris' through which the electron beam may pass. The cavities are coupled in order that a suitable electric field pattern is produced which accelerates electrons propagating through the waveguide 104. As the electrons are accelerated in the waveguide 104, the electron beam path is controlled by a suitable arrangement of steering magnets, or steering coils, which surround the waveguide 104. The arrangement of steering magnets may comprise, for example, two sets of quadrupole magnets.

Once the electrons have been accelerated, they may pass into a flight tube. The flight tube may be connected to the waveguide by a connecting tube. This connecting tube or connecting structure may be called a drift tube. The electrons travel toward a heavy metal target which may comprise, for example, tungsten. Whilst the electrons travel through the flight tube, an arrangement of focusing magnets act to direct and focus the beam on the target.

To ensure that propagation of the electrons is not impeded as the electron beam travels toward the target, the waveguide 104 is evacuated using a vacuum system comprising a vacuum pump or an arrangement of vacuum pumps. The pump system is capable of producing ultra-high vacuum (UHV) conditions in the waveguide 104 and in the flight tube. The vacuum system also ensures UHV conditions in the electron gun 106. Electrons can be accelerated to speeds approaching the speed of light in the evacuated waveguide 104.

The source of radiation is configured to direct a beam 110 of therapeutic radiation toward a patient positioned on the patient support surface 114. The source of radiation may comprise a heavy metal target toward which the high energy electrons exiting the waveguide are directed. When the electrons strike the target, X-rays are produced in a variety of directions. A primary collimator may block X-rays travelling in certain directions and pass only forward travelling X-rays to produce a treatment beam 110. The X-rays may be filtered and may pass through one or more ion chambers for dose measuring. The beam can be shaped in various ways by beam-shaping apparatus, for example by using a multi-leaf collimator 108, before it passes into the patient as part of radiotherapy treatment.

In some implementations, the source of radiation is configured to emit either an X-ray beam or an electron particle beam. Such implementations allow the device to provide electron beam therapy, i.e. a type of external beam therapy where electrons, rather than X-rays, are directed toward the target region. It is possible to 'swap' between a first mode in which X-rays are emitted and a second mode in which electrons are emitted by adjusting the components of the linac. In essence, it is possible to swap between the first and second mode by moving the heavy metal target in or out of the electron beam path and replacing it with a so-called 'electron window'. The electron window is substantially transparent to electrons and allows electrons to exit the flight tube.

The subject or patient support surface 114 is configured to move between a first position substantially outside the bore, and a second position substantially inside the bore. In the first position, a patient or subject can mount the patient support surface. The support surface 114, and patient, can then be moved inside the bore, to the second position, in order for the patient to be imaged by the MR imaging apparatus 112 and/or imaged or treated using the RT apparatus. The movement of the patient support surface is effected and controlled by a subject support surface actuator, which may be described as an actuation mechanism. The actuation mechanism is configured to move the subject support surface in a direction parallel to, and defined by, the central axis of the bore. The terms subject and patient are used interchangeably herein such that the subject support surface can also be described as a patient support surface. The subject support surface may also be referred to as a moveable or adjustable couch or table.

The radiotherapy apparatus/device depicted in figure 1 also comprises MR imaging apparatus 112. The MR imaging apparatus 112 is configured to obtain images of a subject positioned, i.e. located, on the subject support surface 114. The MR imaging apparatus 112 may also be referred to as the MR imager. The MR imaging apparatus 112 may be a conventional MR imaging apparatus 112 operating in a known manner to obtain MR data, for example MR images. The skilled person will appreciate that such a MR imaging apparatus 112 may comprise a primary magnet, one or more gradient coils, one or more receive coils, and an RF pulse applicator. The operation of the MR imaging apparatus is controlled by the controller.

The controller is a computer, processor, or other processing apparatus. The controller may be formed by several discrete processors; for example, the controller may comprise an MR imaging apparatus processor, which controls the MR imaging apparatus 112; an RT apparatus processor, which controls the operation of the RT apparatus; and a subject support surface processor which controls the operation and actuation of the subject support surface. The controller is communicatively coupled to a memory, i.e. a computer readable medium which may be a non-transitory computer readable medium.

The linac device also comprises several other components and systems as will be understood by the skilled person. For example, in order to ensure the linac does not leak radiation, appropriate shielding is also provided.

Figure 2 shows a wearable head device, for use with the MR linac device of figure 1, according to the present disclosure. In particular, the wearable head device comprises a headset 200 also referred to as headphones. The headset is compatible for use with a machine exposing a wearer to therapeutic radiation and/or a magnetic field (e.g., an MR linac device) during therapeutic treatment within a treatment volume of the machine, including treatment of the wearer's head.

Headset 200 comprises a pair of ear cups 210, 220 located at respective ends of a resilient strap 230 to form stereo headphones. In particular, a first ear cup 210 is located at one end of strap 230 and a second ear cup 220 is located at the other end of strap 230. Strap 230 has a U-shaped curvature so that first ear cup 220 faces second end cup 230 with a spacing for a wearer's head therebetween. Thus, in use, strap 230 forms a headband that is placed around the top of the wearer's head, and first and second ear cups 210, 220 cover respective ears of the wearer, with the wearer's head positioned in the spacing therebetween. The shape of the headset 200 is configured to conform closely to a wearer's head. The resilient strap 230 forms a spring that biases the first and second ear cups 210, 220 towards each other such that the first and second ear cups 210, 220 are held in position tightly over the wearer's ears.

First ear cup 210 has a first cup wall 212 defined between an internal surface 214 and an external surface 216. Similarly, second ear cup 220 has a second cup wall 222, defined between an internal surface 224 and an external surface 226. The thickness of the first cup wall 212 may be substantially equal to or less than 3 mm. Similarly, the thickness of the second cup wall may be substantially equal to or less than 3 mm. Resilient strap 230 has a strap wall 232 defined between an internal surface 234 and an external surface 236. The thickness of the strap 230 may be substantially equal to or less than 3 mm. First cup wall 212, second cup wall 222 and strap wall 232 may each have a substantially uniform thickness. In particular, the variation in thickness of the first cup wall 212, the second cup wall 222 and/or the strap wall 232 may be equal to or less than 7.5% of the overall thickness and is typically up to 5%.

In the embodiment depicted in figure 2, the first and second ear cups 210, 220 and the strap 230 are integrally formed of a thin synthetic fibre material layer or "skin". In particular, the synthetic fibre material layer may have a thickness substantially equal to or less than 3 mm. The synthetic fibre material layer may have a uniform thickness, in particular with a variation of less than 7.5% of the overall thickness. Typically, the thickness of the synthetic fibre material layer has a tolerance of about 5%.

The synthetic fibre material layer forming first cup wall 212, second cup wall 222 and strap wall 232 is "radiation hard" and hence resistant to damage by ionising radiation so that the headset 200 can be reused multiple times. The synthetic fibre material may be glass fibre, Kevlar or a similar material with long fibers so as to enable strap 230 to function as a spring. The material and thickness of the synthetic fibre material layer may be selected so that attenuation of a therapeutic radiation beam travelling therethrough is less than 2.5%. The synthetic fibre material may be a thin glass fibre skin of 3 mm or less.

The external surfaces 216, 226 and 236 of headset 200 have a substantially continuous curvature, so as to provide a smooth and consistent external profile. In particular, the boundaries between the ear cups 210, 220 and the respective ends of the strap 230 are substantially straight or smoothly curved to provide a continuous external surface profile. In the embodiment depicted in figure 2, the width of the first and second ear cups 210, 220 is slightly greater than the width of the strap 230, although this is not essential.

The internal surfaces 214, 224 of the first and second ear cups 210, 220 may have a substantially concave shape. Thus, first and second hollow cavities 218, 228 are formed between respective first and second cup walls 212, 222 and the head of the wearer of the head device. Each hollow cavity 218, 228 is configured to accommodate a corresponding one of the wearer's ear and provide an air space for the passage of sound conveyed into the respective ear cup 210, 220, as described below. In the embodiment depicted in figure 2, the first and second ear cups 210, 220 are generally ovoid in shape or outline, so as to substantially conform to the shape of a wearer's ears, and are sized to entirely cover the wearer's ears.

Each of the cup walls 212, 222 has a perimeter region adjacent the edge of the respective ear cups 210, 220. A perimeter cushion 240 comprising a cushioning material is provided on at least the perimeter region of the respective cup walls 212, 222. In use, the perimeter cushion 240 provides an acoustic seal around the hollow cavity 218, 228 between the wearer and the headset 200. Perimeter cushion 240 may also be configured provide comfort for the wearer.

The cushioning material of perimeter cushion 240 comprises a low density foam that is "radiation hard". For example, the cushioning material may be a foam (e.g. polyurethane (PU), polyethylene (PE) or other synthetic foam material) having a density substantially equal to or less than 0.5 kg/dm', such as 0.1 kg/dm3. The cushioning material has a thickness sufficient to provide comfort to the wearer without adding bulk to the ear cup. For example, the cushioning material of the perimeter cushion 240 may have a thickness or about 10 mm. Since the attenuation influence of the cushioning material is so low, the variation in thickness may be 10-15 %.

In the embodiment depicted in figure 2, and as shown in cross section in figures 3 and 4, perimeter cushion 240 extends around the entire perimeter region of each of the first and second ear cup walls 212, 222. In particular, perimeter cushion 240 overlaps the edges (i.e. end surfaces) of the cup walls 212, 222 and a perimeter region of each of the first and second internal surfaces 214, 224 of the respective cup walls 212, 222. In addition, an optional cushion ring 245 is provided on each of the first and second internal surfaces 214, 224 of the respective ear cup walls 212, 222 in an annular region centred around the middle of each ear cup 210, 220. In use, the cushion ring 245 is positioned adjacent the entrance to the ear canal of the wearer's ear to communicate sound and provide additional comfort to the wearer. Cushion ring 245 may comprise the same cushioning material as the perimeter cushion 240, such as the above described low density foam. The thickness of the cushioning material of the cushion ring 245 may be greater that the thickness of the cushioning material of the perimeter cushion 240. For example, the thickness of the cushioning material of the cushion ring 245 may be about 25 mm. As shown in figure 4, the additional thickness of the cushion ring 245 corresponds to the depth of the hollow cavity of the ear cup. Thus, the inner-facing surfaces of the perimeter cushion 240 and cushion ring 245 are substantially aligned so as present a common cushioning surface against the wearer's ears.

As depicted in figures 2 and 4, cushion ring 245 and perimeter cushion 240 may be integrally formed as one piece, with connector cushions 244, 246 therebetween, although this is not essential.

However, the use of connector cushions 244, 246 between the cushion ring 245 and perimeter cushion 240 facilitates adjustment of the position of the cushion ring 245 for the wearer according to the ear shape, allowing the angle and depth of the cushion ring 245 to be varied, so that the perimeter cushion 240 is held in contact with the head and is comfortable for the wearer. Whilst the same cushioning material is used in the illustrated embodiments, in other embodiments cushioning materials of different densities may be chosen for different parts, such as for the perimeter cushion 240 and the cushion ring 245, to adjust the damping and/or sound performance.

First and second hollow communication tubes 251, 252 are provided for respective first and second ear cups 210, 220, and each forms an air tube to communicate sound into the respective first or second hollow cavity 218, 228. Each of the first and second air tubes 251, 252 extends through an aperture in the respective ear cup wall 212, 222 that forms a primary communication hole 254 into the respective first or second hollow cavity 218, 228. In the embodiment depicted in figures 2, 3 and 4, first and second air tubes 251, 252 further extend up to, or through, a corresponding aperture in the cushion ring 245 that forms a secondary communication hole 256 into the part of the respective first or second hollow cavity 218, 228 inside the cushion ring 245. First and second air tubes 251, 252 may be fastened inside the primary and/or secondary communication holes 254, 256, for example by an adhesive or glue, to retain them in position and prevent unwanted movement during use.

Each of the first and second air tubes 251, 252 is formed of a foam with a cavity or hole running centrally along its length. The foam used to form the first and second air tubes 251, 252 may comprise the same low density foam cushioning material as the perimeter cushion 240, as described above, or may comprise a different foam material having similar properties.

Thus, one open end of each of the first and second air tubes 251, 252 is inside the respective first or second hollow cavity 218, 228 or is in communication therewith through the primary communication hole 254 and, in the embodiment of figures 2, 3 and 4, also the second communication hole 256. Sound originating from a source (not shown) at the other open end of each of the first and second air tubes 251, 252 is thus conveyed through the air in the cavity or hole running through the respective first and second air tubes 251, 252 and into the first or second hollow cavity 218, 228, in particular inside the cushion ring 245, of the respective first and second ear cups 210, 220 where it is audible to the wearer.

The wearable head device 200 of figures 2, 3 and 4 has a number of advantages for use in radiotherapy (RT) apparatus such as a linac device and/or MR imaging apparatus.

In particular, the thickness of the strap wall and cup walls is substantially equal to or less than 3 mm.

This thickness reduces attenuation of the therapeutic radiation beam of a linac machine by the material of the headset to acceptable levels. For example, attenuation may be substantially less than or equal to 2.5%. This facilitates planning of the radiation dose to be delivered by a linac machine to a particular patient during treatment. In practice, the attenuation caused by the headphones can be 'ignored' or considered to be negligible by the treatment planning software. Furthermore, the smooth change in attenuation from different angles means that the placement of the headset on the wearer's head is not critical for planning or during treatment. Thus, changes in the headset position between planning and treatment have negligible impact.

Furthermore, the strap wall and cup walls are formed of a material that has low attenuation of the therapeutic radiation beam. For example, the walls may be formed of a synthetic fibre material, such as glass fiber or Kevlar. The density of the material of the walls may be substantially equal to or less than 2 kg/dm3. The use of a low attenuation material further facilitates radiation dose planning. For example, attenuation of the therapeutic radiation beam by glass fiber of 3 mm in thickness may be about 2.22 %, whilst attenuation by Kevlar of the same thickness may be about 1.8%.

In addition, the thickness of the strap wall and cup walls is substantially uniform. For example, the variation in thickness of the strap and cup walls is less than 1%. This means that the headset presents substantially the same amount of material to the radiation beam, irrespective of the angle or direction of the beam. In consequence, attenuation of the therapeutic radiation beam is substantially the same for beams travelling in different directions around the patient and passing through the headset.

Moreover, the external surface of the headset, comprising the external surfaces of the strap wall and cup walls, has a substantially constant curvature. Thus, the headset has a continuous external profile, with substantially straight or smoothly curved boundaries between the strap and ear cups, and so does not produce sharp gradients or visible edges in the MR signal of an MR imaging apparatus. Indeed, appropriate selection of the materials, thicknesses and shape of the headset reduces, and can even eliminate, the influence on the MR signal, so that the headset is not visible in the MR images.

In addition, the ear cups are provided with cushioning material, comprising a perimeter cushion and a ring cushion, which forms an acoustic seal. This provides adequate protection of the wearer's ears from the loud noises, for example arising from an MR imaging apparatus. In addition, sound can be conveyed into the hollow cavity by air tubes and heard by the patient, allowing the patient to listen to a sound recording, such as music, or voice communication from a healthcare professional. The use of foam air tubes, that provide air communication pathways for sound to the wearer, also enables compatibility with MR imaging apparatus including MR linac devices, since such air tubes are not visible to the MR signal.

Furthermore, the design of the headset depicted in figures 2, 3 and 4 has additional advantages when treating the head and/or neck of the wearer. In particular, the headset is sufficiently small and streamlined such that it can to be accommodated under a mask, which is conventionally used with an RT apparatus for treating the head and/or neck. In particular, the thicknesses of the strap wall and cup walls, even when combined with the cushioning material, is small enough to be accommodated under a mask that is positioned over and shaped (e.g., by heat moulding) to conform with the patient's head and face during treatment. The external surfaces of the strap wall and/or cup walls may be roughened to increase friction between the headset and the mask, to prevent relative movement. The use of headphones with such a mask for use with a linac device has not been possible to date.

As the skilled person will appreciate, many variations and modifications may be made to the described embodiments. For example, whilst the described embodiment comprises stereo headphones with two ear cups, a mono headphone with a single ear cup is possible. Furthermore, changes to the headset design, such as the shape, dimensions and materials of the strap and ear cups may be made according to application requirements. It is intended to include all such changes, modifications and equivalents that fall within the scope of the present disclosure. The above implementations have been described by way of example only, and the described implementations and arrangements are to be considered in all respects only as illustrative and not restrictive. It will be appreciated that variations of the described implementations and arrangements may be made without departing from the scope of the invention.

Claims

CLAIMS1. A wearable head device for use within a treatment volume of a magnetic resonance linear accelerator (MR-linac) machine, the MR-linac machine exposing the treatment volume, in use, to therapeutic radiation and a magnetic field, the wearable head device comprising: at least one ear cup comprising a cup wall, the cup wall having an internal surface and an external surface defining a cup wall thickness therebetween, wherein the cup wall thickness is substantially equal to or less than 3 mm.
2. The wearable head device of claim 1, wherein the internal surface is shaped such that, in use, a hollow cavity is formed between the cup wall and a wearer of the wearable head device.
3. The wearable head device of claim 1 or 2, wherein the cup wall thickness is substantially uniform.
4. The wearable head device of any preceding claim, wherein the external surface has a substantially constant curvature.
5. The wearable head device of any preceding claim, wherein the internal surface is concave.
6. The wearable head device of any preceding claim, wherein the cup wall comprises a perimeter region around an end of the cup wall, the perimeter region having a cushion material thereon arranged such that, in use, an acoustic seal is formed between a wearer of the wearable head device and the perimeter region.
7. The wearable head device of claim 6, wherein the cushion material is a foam.
8. The wearable head device of claim 6 or 7, wherein the cushion material has a density substantially equal to or less than 0.5 kg/dm3.
9. The wearable head device of claim 8, wherein the density of the cushion material is 0.1 kg/dm 3.
10. The wearable head device of any preceding claim, wherein the cup wall is formed of a synthetic fibre material.
11. The wearable head device of claim 10, wherein the synthetic fibre material is glass fiber or Kevlar.
12. The wearable head device of any preceding claim, wherein the cup wall has a density substantially equal to or less than 2 kg/dm3.
13. The wearable head device of claim 12, wherein the density of the cup wall is 1.5 kg/dm3.
14. The wearable head device of any preceding claim, comprising two of the at least one ear cup, the two ear cups connected by a strap.
15. The wearable head device of claim 14, wherein the strap comprises an internal strap surface arranged to be placed around a wearer's head, and an external strap surface, the internal strap surface and the external strap surface defining a strap thickness therebetween.
16. The wearable head device of claim 15, wherein the strap thickness is substantially equal to or less than 3 mm.
17. The wearable head device of claim 15 or 16, wherein the strap thickness is substantially uniform.
18. The wearable head device of any of claims 14 to 17, wherein the strap is formed of a synthetic fibre material.
19. The wearable head device of claim 18, wherein the synthetic fibre material is glass fiber or Kevlar.
20. The wearable head device of any preceding claim, further comprising a hollow communication tube connected to the at least one ear cup and arranged to provide an air communication pathway to a wearer of the wearable head device.
21. The wearable head device of claim 20, wherein the internal surface of the cup wall comprises a communication hole in communication with the hollow communication tube.