Patent Description:
Radiotherapy uses ionising radiation to treat a human or animal body. In particular, radiotherapy is commonly used to treat tumours within the human or animal body. In such treatments, cells forming part of the tumour are irradiated by ionising radiation in order to destroy or damage them. However, in order to apply a prescribed dose of ionising radiation to a target location or target region, such as a tumour, the ionising radiation will typically also pass through healthy tissue of the human or animal body. Therefore, radiotherapy has the desirable consequence of irradiating and damaging a target region, but can also have the undesirable consequence of irradiating and damaging healthy tissue. In radiotherapy treatment, it is desirable to align the dose received by the target region with a prescribed dose and to minimise the dose received by healthy tissue. For example, document <CIT> is directed to a treatment system for a patient that includes a treatment couch to position the patient. The treatment couch includes a couch top and one or more stages to pitch the couch top about a lateral axis and/or roll the couch top about a longitudinal axis, translate the couch top along lateral directions and/or longitudinal directions, rotate the couch top about a vertical axis, and translate the couch top along vertical directions.

Modern radiotherapy treatment uses techniques to reduce the radiation dose to healthy tissue and thereby provide a safe treatment. For example, one approach to minimising a radiation dose received by healthy tissue surrounding a target region is to direct the radiation towards the target region from a plurality of different angles, for example by rotating a source of radiation around the patient by use of a rotating gantry. In this case, the angles at which radiation is applied are selected such that each beam of radiation passes through the target region. In this way, a cumulative radiation dose may be built up at the target region over the course of a treatment arc in which the radiation source rotates through a certain angle. Radiation is emitted in a radiation plane which is coincident with the plane of the gantry around which the radiation source rotates and radiation may thus be delivered to a radiation isocenter at the centre of the gantry regardless of the angle to which the radiation head is rotated around the gantry. Because the radiation is applied from a plurality of different angles, the same, high, cumulative radiation dose is not built up in the healthy tissue since the specific healthy tissue the radiation passes through varies with angle. Therefore, a unit volume of the healthy tissue receives a reduced radiation dose relative to a unit volume of the target region. Treatments that utilise rotation of the gantry in this manner are known as coplanar. However, after the radiation source has been rotated <NUM>°, it will be appreciated that any subsequent radiation beams begin to pass through regions of healthy tissue which have already been irradiated. This increases the radiation dose applied to healthy tissue. Accordingly, when using such a method the volume of healthy tissue available to spread the radiation dose is relatively small, thus imposing restrictions on the treatment which can be provided by such devices.

Therefore, an alternative approach to minimising the radiation dose received by healthy tissue surrounding a target region is to rotate the patient relative to the plane of radiation. As the angle of the patient varies relative to the plane of the gantry, so does the healthy tissue the radiation passes through. In order to further reduce the radiation dose relative to a unit volume of the target region, it is desirable to provide a treatment that combines both of these rotations. An example of a known device that combines the rotation of the patient with the rotation of the radiation source is shown in <FIG>. This shows that the patient <NUM>, who is supported on the subject support surface <NUM>, which is also referred to herein as a patient support surface <NUM>, can be rotated whilst the gantry <NUM> may also rotate about the patient support surface <NUM>. The gantry <NUM> shown in <FIG> is a C-arm gantry or open gantry. The rotation mechanism <NUM> rotates the gantry <NUM> about a fixed axis <NUM>. As the gantry <NUM> is rotated, radiation emitted by a radiation source <NUM> can sweep out a circle. Radiation can be applied to the patient <NUM> from a plurality of angles around the circle. The circle may be described as lying in a radiation plane. The radiation axis lies in the radiation plane. The radiation axis makes an angle of <NUM>° with respect to the fixed axis <NUM>.

The rotation mechanism <NUM> for the patient support surface <NUM> is located underneath the gantry <NUM> of the radiotherapy device, while a rotation mechanism for the gantry <NUM> is located opposite the patient support surface <NUM>. The rotation mechanism <NUM> for the patient support surface <NUM> is located underneath the gantry <NUM> so that the axis of rotation <NUM> of the patient support surface <NUM> will be in the radiation plane. In particular, the axis of rotation <NUM> of the patient support surface passes through the isocenter <NUM> of the radiotherapy device, so that the patient support surface <NUM> is rotated about the isocenter <NUM>. When the patient support surface <NUM> is in its neural position, the axis of rotation of the patient support surface <NUM> is substantially vertical (perpendicular to the plane of the floor) and this can also be called a vertical axis <NUM>. The longitudinal axis <NUM> is parallel to long side of the patient support surface <NUM> in its neutral position and the transverse axis <NUM> is parallel to the short end of the patient support surface <NUM> in its neutral position. The rotation mechanism <NUM> is located within the plane of radiation. Treatments utilising both the rotation of the radiation and the patient <NUM> are known as non-coplanar treatments.

Some recently developed radiotherapy devices comprise ring-based gantries (or bores), such as that shown in <FIG>. Typically, the bore of a radiotherapy device is cylindrical. A patient support surface <NUM> is positioned in the bore such that radiation can be directed toward a patient <NUM> positioned on the support surface <NUM>. The bore of the apparatus can be formed by a framework, which may otherwise be described as a chassis, a shielding structure, a shell, or a casing. The framework defines the outer surface of the device which the patient <NUM> sees upon entering the treatment room, as well as defining the inner surface of the bore which the patient <NUM> sees when positioned inside the bore. The framework also defines a hollow region of annular cross-section in which the gantry <NUM> can be both rotated and tilted. Thus, the patient <NUM> is shielded from the rotatable gantry <NUM>. Movement of the gantry <NUM> is hidden from the patient's view, reducing intimidation and distress which may otherwise be caused if the patient <NUM> were able to see rotation of the large gantry <NUM>, as they would for an open gantry as shown in <FIG>, and also reducing the likelihood that the patient can accidentally touch or otherwise interfere with the movement of the gantry <NUM>. This means that the gantry <NUM> can be rotated quickly, efficiently and safely. Ring-based gantries are also desirable because they increase device stability. The ring-based gantry is supported by the floor and rests upon it. However, the geometry of a ring-based gantry and its connection to the floor makes it impossible to rotate the subject support surface <NUM> using known systems in such a way as to maintain a portion of the subject support surface <NUM> substantially at the isocenter <NUM>.

Specific embodiments are now described, by way of example only, with reference to the drawings, in which:.

By providing a radiotherapy apparatus for delivering radiation to a subject, the apparatus comprising a source of radiation configured to rotate about an isocenter and emit radiation in a radiation plane containing said isocentre, a subject support surface including a portion configured to be located substantially at the isocenter, the subject support surface comprising a subject support surface rotation mechanism configured to rotate the subject support surface about an axis of rotation parallel to and spaced from an axis that passes through the isocenter and a first section configured to move from a first position to a second position along at least one of a longitudinal and lateral direction, and the apparatus further comprising a processor configured to control the longitudinal and/or lateral movement of the first section as a function of the rotation of the subject support surface to maintain the portion of the subject support surface substantially at the isocenter, a number of benefits are provided.

For example, when the subject support surface/couch is used to support a patient as part of a treatment, the rotation of the subject support surface by the rotation mechanism means that the radiation dose that forms part of the treatment can be spread through the healthy tissue of the patient. Therefore, the total radiation dose received by a particular bit of healthy tissue surrounding a target region can be minimised. At the same time, controlling the movement of the first section as a function to maintain the portion of the subject support surface substantially at the isocenter makes it possible to maximise the amount of radiation that passes through the target region in particular, which increases the efficiency of the treatment. This improves patient wellbeing. The apparatus described herein and locating the rotation mechanism outside the plane of radiation enables the use of a couch kick (rotatable couch) in a ring gantry based linac system.

When administering a treatment to a subject or patient <NUM> with a radiotherapy apparatus comprising a source of radiation <NUM> configured to rotate about an isocenter <NUM> and emit radiation in a radiation plane containing said isocenter <NUM>, rotating the subject whilst maintaining the subject substantially at the isocenter <NUM> allows the dose received by healthy tissue during the radiotherapy treatment to be minimised. This can be achieved by providing a subject support surface rotation mechanism <NUM> connected to the subject support surface <NUM> and configured to rotate the subject support surface <NUM> about an axis of rotation parallel to and spaced apart from an axis that passes through the isocenter <NUM>, whilst moving a top section <NUM> of the subject support surface <NUM> to compensate for the relative movement of a particular portion of the subject support surface <NUM> that is caused by the rotation of the subject support surface <NUM>. In particular, the top section can be moved in a longitudinal and/or lateral direction as a function of the rotation of the subject support surface <NUM> so as to maintain a portion of the subject support surface <NUM> substantially at the isocenter <NUM>. By rotating the subject support surface whilst also maintaining a portion of the subject support surface <NUM> substantially at the isocenter <NUM> using the movement of a first section (which may be a top section of the subject support surface that is configured to move from a first position to a second position along at least one of a longitudinal and lateral direction independently from the rest of the subject support surface) a number of advantageous effects are achieved. For example, when the apparatus is used for treatment of a patient <NUM>, the radiation dose can be spread through the healthy tissue of the patient <NUM> so that the radiation dose received by healthy tissue surrounding a target region is minimised. At the same time, it is possible to ensure that the maximum amount of radiation passes through the target region, thereby increasing the efficiency of the treatment. This improves patient <NUM> wellbeing. If the first section <NUM> was not configured to move as a function of the rotation of the subject support surface <NUM> to maintain the portion of the subject support surface <NUM> substantially at the isocenter <NUM>, then the location of the target region would move with respect to the isocenter <NUM> (and focus of the radiation) and, accordingly, this would result in an increased dosage of radiation being received by healthy tissue. Furthermore, this would result in a longer treatment time because the target region would not receive the intended dosage of radiation.

The portion of the subject support surface that is maintained substantially at the isocenter <NUM> may correspond to a portion of a patient <NUM> such as a target region of a patient <NUM>. Thus, by maintaining a portion of the subject support surface substantially at the isocenter <NUM> it is possible to maintain a target region substantially at the isocenter <NUM>. Locating the subject support surface rotation mechanism <NUM> outside the radiation plane allows the dose received by healthy tissue of the subject <NUM> during the radiotherapy treatment to be minimised for a wide range of radiotherapy apparatuses with different geometries. In particular, the disclosed subject support surface <NUM> is well suited for radiotherapy apparatuses that comprise a bore for receiving the subject <NUM>.

In accordance with one embodiment, <FIG> depicts a radiotherapy device suitable for delivering 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 <FIG> is in accordance with the present disclosure and is suitable for use with the disclosed systems and apparatuses, although not all of the features are necessarily present, or as depicted in <FIG>. While the device in <FIG> is an MR-linac, the implementations of the present disclosure may be any radiotherapy device, for example a linac device. <FIG> shares features common with known devices such as Versa HD™ in particular, the features involved in producing the treatment beam <NUM>. The embodiment shown in <FIG> is modified over known devices in accordance with the invention by the provision of a subject support surface rotation mechanism <NUM>, as will be described in more detail below.

The device depicted in <FIG> is an MR-linac. The device comprises both MR imaging apparatus <NUM> and radiotherapy (RT) apparatus which may comprise a linac device. In operation, the MR scanner produces MR images of the patient <NUM>, 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 usual 'housing' which would cover the MR imaging apparatus <NUM> and RT apparatus in a commercial setting such as a hospital is not depicted in <FIG>.

The MR-linac device depicted in <FIG> comprises a source of radiation <NUM>. The source of radiation <NUM> may comprise beam generation equipment, such as one or more of: a source of radiofrequency waves <NUM>, a circulator <NUM>, a source of electrons <NUM>, a waveguide <NUM>, and a target (not shown)The MR-linac may also comprise a collimator <NUM> such as a multi-leaf collimator configured to collimate and shape the beam, MR imaging apparatus <NUM>, and a patient support surface <NUM>. The device also comprises a housing which, together with the ring-shaped gantry defines a bore. The moveable subject support surface <NUM> can be used to move a patient, or other subject, into the bore when an MR scan and/or when radiotherapy is to commence or during treatment. The MR imaging apparatus <NUM>, 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 <NUM> and a radiation detector (not shown). Typically, the radiation detector is positioned diametrically opposed to the radiation source <NUM>. 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 <NUM> defines the point at which the treatment beam <NUM> is introduced into the bore. The radiation source <NUM> may comprise a beam generation system, which may comprise a source of RF energy <NUM>, an electron gun <NUM>, and a waveguide <NUM>. The beam generation system is attached to the rotatable gantry <NUM> so as to rotate with the gantry <NUM>. In this way, the radiation source <NUM> is rotatable around the patient <NUM> so that the treatment beam <NUM> can be applied from different angles around the gantry <NUM>. In a preferred implementation, the gantry <NUM> is continuously rotatable. In other words, the gantry <NUM> can be rotated by <NUM> degrees around the patient, and in fact can continue to be rotated past <NUM> degrees. The gantry <NUM> rotates about a mechanical isocenter, which is the point in space about which the gantry <NUM> rotates and about a fixed axis <NUM> as shown in <FIG>. The radiation isocenter can be defined as the point where the radiation beams intersect. These two isocenters <NUM> need not be the same, although it may be desirable that they should be. In this disclosure, the term isocenter <NUM> can refer to either or both of these. The isocenter <NUM> is located within the radiation plane. The gantry <NUM> may be ring-shaped. In other words, the gantry <NUM> may be a ring-gantry with a bore. The gantry <NUM> may also not be ring-shaped and may instead be an open gantry such as that shown in <FIG>.

The source <NUM> of radiofrequency waves, such as a magnetron, is configured to produce radiofrequency waves. The source <NUM> of radiofrequency waves is coupled to the waveguide <NUM> via circulator <NUM>, and is configured to pulse radiofrequency waves into the waveguide <NUM>. Radiofrequency waves may pass from the source <NUM> of radiofrequency waves through an RF input window and into an RF input connecting pipe or tube. A source of electrons <NUM>, such as an electron gun, is also coupled to the waveguide <NUM> and is configured to inject electrons into the waveguide <NUM>. 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 <NUM> is synchronised with the pumping of the radiofrequency waves into the waveguide <NUM>. The design and operation of the radiofrequency wave source <NUM>, electron source and the waveguide <NUM> is such that the radiofrequency waves accelerate the electrons to very high energies as the electrons propagate through the waveguide <NUM>.

The source of radiation <NUM> is configured to direct a beam <NUM> of therapeutic radiation toward a patient positioned on the patient support surface <NUM>. The source of radiation <NUM> 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 <NUM>. 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 <NUM>, before it passes into the patient as part of radiotherapy treatment.

In some implementations, the source of radiation <NUM> 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 radiotherapy apparatus / device depicted in <FIG> also comprises MR imaging apparatus <NUM>. The MR imaging apparatus <NUM> is configured to obtain images of a subject positioned, i.e. located, on the subject support surface <NUM>. The MR imaging apparatus <NUM> may also be referred to as the MR imager. The MR imaging apparatus <NUM> may be a conventional MR imaging apparatus <NUM> operating in a known manner to obtain MR data, for example MR images. The skilled person will appreciate that such a MR imaging apparatus <NUM> 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 <NUM>; 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.

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.

The patient support surface <NUM> may serve to support an object. The object may be a human body (such as a patient), an animal body or a material sample. The subject support surface <NUM> is configured to move parallel to the longitudinal axis <NUM> between a first position substantially outside the bore, and a second position substantially inside the bore. In the first position, a patient <NUM> or subject can mount the subject support surface <NUM>. The subject support surface <NUM>, and patient <NUM>, can then be extended inside the bore, to the second position, in order for the patient <NUM> to be imaged by the MR imaging apparatus <NUM> and/or imaged or treated using the RT apparatus. The terms subject and patient are used interchangeably herein such that the subject support surface <NUM> can also be described as a patient support surface <NUM>. The subject support surface <NUM> may also be referred to herein as a patient support surface and a moveable or adjustable couch or table.

The present invention is distinguished over known devices as follows. The subject support surface <NUM> is connected to a subject support surface rotation mechanism <NUM>. The rotation mechanism <NUM> is configured to rotate the subject support surface <NUM> (which is also described herein as a couch <NUM>, patient support surface <NUM>, or patient positioning system <NUM>) about an axis of rotation parallel to and spaced from an axis that passes through the isocenter 124of the gantry <NUM>. The rotation mechanism <NUM> can be attached to the floor or, for example, can be attached to the device housing or gantry <NUM> (as shown in, for example, Fig. 4a). The patient support surface <NUM> or part thereof can be rotated around (or about) the longitudinal axis <NUM> (roll) of the couch <NUM>, around the transverse axis <NUM> (pitch) of the couch <NUM>, or about an axis perpendicular to the floor <NUM> (yaw) of the couch <NUM>, whether the couch <NUM> is in a neutral or a rotated orientation, or any combination of these. These axes are referenced relative to the couch <NUM>, regardless of its orientation at the time, unless specified otherwise.

Although in <FIG> the plane of the rotation of the patient support surface <NUM> is illustrated as being parallel to the illustrated floor (as is defined by the xy plane, which corresponds to the plane of the patient support surface <NUM> in its neutral position where x is the longitudinal axis <NUM> and y is the transverse axis <NUM>), with rotation as yaw about the axis <NUM> of couch <NUM> in neutral position, by way of example, the angle of the plane of rotation relative to the floor (tilt) could be at an angle of <NUM>, <NUM>, <NUM> or <NUM> degrees to the floor. However, for reasons of patient comfort, the angle will usually be kept fairly low. It is also possible for the tilt to be changed either prior to, or during, treatment. The rotation mechanism <NUM> and/or the patient support surface <NUM> may also be connected to an additional rotation mechanism (not shown) configured to rotate the rotation mechanism <NUM> and/or the patient support surface <NUM> in a different plane. In this way, the patient support surface <NUM> may be connected to more than one rotation mechanism <NUM>, each configured to move the patient support surface <NUM> in a different plane. Alternatively, a single rotation mechanism <NUM> may be configured to rotate the patient support surface <NUM> in more than one plane with the axis of rotation of each of the rotation planes of the patient support surface <NUM> being parallel to and spaced from an axis that passes through the isocenter <NUM>.

Simply rotating the couch <NUM> about an axis of rotation parallel to and spaced from an axis that passes through the isocenter <NUM> (also referred to herein as off isocenter rotation) from a first rotational position to a second rotational position would cause a portion of the couch <NUM> located at the isocenter <NUM> when the couch <NUM> is in its first rotational position to move away from the isocenter <NUM> when the couch <NUM> is in its second rotational position. In a treatment context, this would cause the target region of a patient <NUM> on the couch <NUM> to move away from the isocenter <NUM> when rotating the couch <NUM>, which would result in an increased dosage of radiation being received by healthy tissue. Furthermore, this would result in a longer treatment time because the target region would not receive the intended dosage of radiation.

Accordingly, the subject support surface <NUM> is configured to move a particular section of the subject support surface <NUM> within a plane that is perpendicular to the axis of rotation separately from the rest of the subject support surface <NUM> and in such a way as to enable a portion of the couch <NUM> to be maintained substantially at the isocenter <NUM>. In particular, the subject support surface comprises one or more sections <NUM>, <NUM> which is/are configured to move from a first position to a second position along at least one of a longitudinal <NUM> and lateral <NUM> direction, or a direction oblique to these. These directions are referred to relative to the couch <NUM>, regardless of the rotational orientation of the couch <NUM> at the time. The movement of this section of the couch <NUM> can be used to compensate for the relative displacement of a particular portion of the couch <NUM> away from the isocenter <NUM> that is caused by the off isocenter rotation of the couch <NUM>. In particular, a section <NUM>, <NUM> of the couch <NUM> can be moved in such a way as to maintain a particular portion of the subject support surface <NUM> substantially at the isocenter <NUM> whilst the couch <NUM> itself is rotated. The movement of the section <NUM>, <NUM> of the couch <NUM> is controlled by a processor as a function of the rotation of subject support surface <NUM> so as to maintain the portion of the subject support surface <NUM> substantially at the isocenter <NUM>.

For example, when a couch <NUM> is in a neutral rotational position (in which its longitudinal axis <NUM> is parallel to the fixed axis <NUM> (of the gantry <NUM> in its neutral position)), a portion of the couch <NUM> is located at the isocenter <NUM>. When the couch <NUM> is rotated by the rotation mechanism <NUM> to a rotated position, for example of <NUM> degrees clockwise, this portion moves away from the isocenter <NUM>. The apparatus also comprises a memory, which stores information such as the dimensions of the couch <NUM>, different sections of the couch <NUM>, <NUM>, <NUM>, the position of the isocenter <NUM>, the dimensions of the gantry <NUM> and gantry cover, the location of the axis of rotation of the couch <NUM> and its position relative to the isocenter <NUM>, and other useful information. The processor can use this information in a collision matrix to ensure that the system knows when and how collisions can appear and controls the movement and rotation of the couch <NUM> to avoid this. The processor can use such information to calculate the movement of the portion of a couch <NUM> that is or will be caused by a particular amount of rotation. The processor then calculates the amount of movement of the couch <NUM> in one or more of a longitudinal and lateral direction (relative to the couch <NUM> in its particular rotated position) that would be required in order to return (or maintain) the portion of the couch <NUM> back to the isocenter <NUM>. The processor then controls the movement of a section <NUM>, <NUM> of the couch <NUM> according to the calculated amount in such a way that the portion of the couch <NUM> is maintained (or returned) to the isocenter <NUM>.

The processor can also be configured to control the rotation of the couch <NUM>. The processor can be configured to calculate movement of the section <NUM>, <NUM> that will be necessary or desired, before the rotation actually occurs. For example, the processor can plan the rotation of the couch <NUM> and corresponding movement of the section <NUM>, <NUM> as part of a treatment plan. The rotation and the movement can therefore occur simultaneously to ensure that the portion of the couch <NUM> is maintained substantially at the isocenter <NUM> in a first rotational position in a second rotational position and in every rotational position between these positions. Alternatively, the rotation of the couch <NUM> can occur by manual operation (e.g. by an operator) and the processor can then calculate and command the necessary movement of a section <NUM>, <NUM> of the couch <NUM> reactively, although, due to fast processing times, this may appear to an observer to be occurring in real time. The processor can be comprised within the couch <NUM> or can be located separately, for example, in a control room. The processor can also use information such as the dimensions and relative configuration of the gantry <NUM> to determine a maximum rotation angle possible for a particular couch <NUM> configuration without interference, and thereby ensure that the rotation does not result in the couch <NUM> contacting the gantry <NUM> in an unwanted manner.

The processor that controls the movement of the section <NUM>, <NUM> may be the same processor as for the MR imaging apparatus <NUM> or RT apparatus and thus can also be configured to control the emission and rotation of the radiation source <NUM>. In this way, the rotation of the couch <NUM> can be planned as part of a broader treatment plan and can be coordinated with the operation of the RT apparatus more generally in such a way as to optimise the treatment by reducing treatment times and minimising damage to healthy tissue.

Because the axis of rotation is parallel to and spaced from an axis that passes through the isocenter <NUM>, it is not necessary to locate the rotation mechanism <NUM> within the plane of the radiation, as is shown in <FIG>, in order to get the benefits of true isocentric rotation. Instead, it is possible to use a large variety of rotation mechanisms <NUM>, such as those that are located outside of the plane of the gantry <NUM> and therefore the plane of radiation, or isoline. This is particularly useful for ring gantry/bore solutions or devices with <NUM>° rotation of the gantry <NUM>, for which it is problematic to position the rotation mechanism <NUM> within the radiation plane without interfering with the gantry <NUM>. However, this disclosure is applicable to any radiotherapy device. Whilst the disclosure is not limited to bore solutions (ring gantries), bore solutions offer improved device stability. Furthermore, bore solutions are less imposing or alarming for patients. Bore solutions therefore may be desirable. The disclosure provides means to supply non-coplanar treatments (in which both gantry <NUM> and patient support surface <NUM> are rotated) in a radiotherapy device with a bore solution. Positioning the rotation means outside the plane of radiation also minimises radiation interference.

In this way, it is possible to maintain a portion of the couch <NUM> (and therefore a target region of a patient <NUM>) substantially at the isocenter <NUM> whilst rotating the couch <NUM> (and patient <NUM>) so that the radiation dose can be spread through the healthy tissue and meaning that the radiation dose received by healthy tissue surrounding a target region is minimised. This improves patient <NUM> wellbeing. The disclosure also provides an apparatus that utilises rotation means <NUM> which are located outside of the plane of the gantry <NUM> and therefore the plane of radiation, or isoline. Positioning the rotation means <NUM> outside the plane of radiation minimises radiation interference.

Examples of specific linkages and structures will now be described.

One embodiment is shown from different perspectives and in different positions in <FIG>, <FIG> <FIG> and <FIG>. These figures show a subject support surface <NUM> supported by and connected to a rotation mechanism <NUM>. The rotation mechanism <NUM> comprises a rigid hinge <NUM> with the longitudinal axis of the hinge parallel to the vertical axis <NUM>, a rotatable bracket <NUM> and two vertical sliders or guide rails <NUM>. The rotatable bracket <NUM> is configured to rotate about the hinge <NUM> and therefore is configured to rotate about the vertical axis. The rotation of the hinge can be driven by one or more motors, such as electric motors, although in some examples it can also be rotated manually, for example by certain increments. The hinge <NUM> is attached directly to the gantry <NUM> (or gantry cover) and is fixed in relation to the gantry <NUM>. The rotatable bracket <NUM> is rotatably connected to the hinge <NUM>, for example, by a mechanical pivot, so that it is configured to rotate about an axis of rotation that passes through the longitudinal axis of the hinge <NUM>. The hinge <NUM> is spaced from the isocenter <NUM> and therefore, by rotating about the hinge <NUM>, the couch <NUM> is configured to rotate about an axis of rotation parallel to and spaced from an axis that passes through the isocenter <NUM>. The whole rotation mechanism <NUM> is located outside the plane of the gantry <NUM> and outside the plane of radiation. The rotating bracket <NUM> is configured to hold the two guide rails <NUM>, which are bolted on to the rotating bracket <NUM> as can be seen in <FIG>. The couch <NUM> is connected directly to the rotation mechanism <NUM> or via an intermediary and can be connected by any suitable means, for example, mechanically. The rotation is controlled by a processor which may be comprised in the patient support surface <NUM> or may be located elsewhere. For example, the processor can control the speed of rotation or the angle of rotation of the couch <NUM>.

The rotation mechanism <NUM> also comprises sliding covers <NUM> which cover the guide rails <NUM> to prevent anything becoming caught in the vertical motion mechanism and to prevent pinching hazards. The sliding covers <NUM> are configured to accommodate the rotation of the bracket <NUM>. In one example, the sliding covers <NUM> are made of a flexible material such as rubber, that can accommodate this rotation. Alternatively, the sliding covers <NUM> may be separate from the rotation mechanism but attached to the gantry <NUM> in such a way as to still protect the vertical guide rails <NUM> when the couch <NUM> is in both a non-rotated and rotated position.

The couch <NUM> comprises bottom section <NUM>, a middle section <NUM> and a top section <NUM>. The bottom section <NUM> is movably connected to the two vertical guide rails <NUM> in such a way that the bottom section <NUM> is configured to move from a first position to a second position along a vertical direction (along a vertical axis <NUM> that is an axis perpendicular to the floor). In one example, the bottom section <NUM> comprises carrier cars (guide rail cars) <NUM> that are configured to slide along linear guides (guide rails) <NUM> that are connected to the rotatable bracket <NUM>. This movement is driven by one or more motors that can be located either on the rotatable bracket <NUM> or on the bottom section <NUM>. The vertical direction <NUM> may also be described as the Z direction <NUM> or just vertically. For example, the bottom section <NUM> can be moved vertically from a lowered position (as shown in <FIG>) to a raised position. The top section <NUM> is supported by the middle section <NUM>, which is supported by the bottom section <NUM>. Thus, when the bottom section <NUM> is raised or lowered, the middle and top sections <NUM>, <NUM> are also raised or lowered. In this way, the whole of the couch <NUM> can be raised or lowered (moved vertically from a first position to a second position) along the vertical sliders of the rotation mechanism <NUM>.

The middle section <NUM> (which may be described as a first or second section) is configured to move independently from the bottom section <NUM> in a lateral direction (along a transverse axis <NUM> of the patient support surface <NUM>) from a first position to a second position. In one example, the middle section <NUM> is configured to move along guide rails and this movement can be powered by one or more electric motors and, for example, a ball screw, belt drive or other suitable means. The lateral or transverse direction <NUM> may be described as the X direction <NUM>. The top section <NUM> is supported by the middle section <NUM> and, accordingly, when the middle section <NUM> is moved in a lateral direction <NUM>, the top section <NUM> is also moved in a lateral direction with it. In one example, the middle section <NUM> is configured to move in a lateral direction when the bottom section <NUM> is in a raised position.

The top section <NUM> (which may be described as a first or second section) is configured to move independently from the bottom and middle sections <NUM>, <NUM> in a longitudinal direction (along a longitudinal axis <NUM> of the patient support surface <NUM>) from a first position to a second position. In one example, the top section <NUM> is configured to move along guide rails and this movement can be powered by one or more electric motors and, for example, a ball screw, belt drive or other suitable means. The longitudinal direction <NUM> may be described as Y direction <NUM>.

In one example, the top section <NUM> and the middle section <NUM> are in fact the same section, and this combined section (which may be described as a first section) is configured to move independently from the bottom section <NUM> from a first position to a second position along at least one of a longitudinal <NUM> and lateral <NUM> direction or in a direction oblique to these.

A processor is configured to control the movement of the bottom, middle and top sections <NUM>, <NUM>, <NUM>. In the present example, this processor is the same as the processor that controls the rotation of the couch <NUM>.

As stated previously, the hinge <NUM> is spaced from the isocenter <NUM> and the rotatable bracket <NUM> and thus the couch <NUM> (which is connected to the bracket <NUM>) are configured to rotate about the hinge <NUM>. Thus, the couch <NUM> is configured to rotate about an axis of rotation parallel to and spaced from an axis that passes through the isocenter <NUM>. As explained previously, this results in a portion of the couch <NUM> that is located at the isocenter in the non-rotated position of the couch <NUM>, moving away from the isocenter <NUM> when the couch <NUM> is rotated. The apparatus also comprises a memory in which it can store information such as the dimensions of the different sections <NUM>,<NUM>,<NUM> of the couch <NUM>, the position of the hinge <NUM> relative to the isocenter <NUM>, the dimensions of the gantry <NUM> and gantry cover and other information useful to performing a treatment. The processor uses information such as this to calculate how much the previously mentioned portion of the couch <NUM> will have moved for a particular rotation angle of the couch <NUM>. The processor then calculates how much lateral and/or longitudinal movement is needed in order to maintain the portion of the couch <NUM> at the isocenter <NUM> for the rotation angle. In this example, the processor then executes commands causing the couch <NUM> to rotate to the particular angle, the middle section <NUM> to move by the needed lateral amount, and the top section <NUM> to move by the needed longitudinal amount.

In this example, the processor is also used to control the rotation and emission of the radiation and could also be used to control other operation of the radiotherapy device. This allow the rotation of the couch <NUM> to be synchronized with the operation of the radiotherapy device or delivery of the radiotherapy treatment. One example of a treatment shall now be described.

The couch <NUM> starts in a lowered and neutral position (the bottom section <NUM> is lowered, the middle and top sections <NUM>, <NUM> are not extended, and the couch <NUM> is not rotated), as illustrated in <FIG>. A patient <NUM> then lies on the couch <NUM> on top of the top section <NUM>, which is made easy for the patient <NUM> by virtue of the couch <NUM> being lower to the ground. An operator then starts the treatment, for example, by pressing a start button. The operator may also input a number of treatment parameters in a computer, which can then be used by the processor to control the treatment. First the bottom section <NUM> is raised (thereby raising the couch <NUM> and the patient <NUM>), as illustrated in <FIG>. The movement of the bottom section <NUM> is controlled by one or more guide rail cars <NUM>, which are configured to move up and down the guide rails <NUM>, which are bolted to the rotatable bracket <NUM>. <FIG> depicts the subject support surface <NUM> in a raised, non-extended and non-rotated position.

Once the couch <NUM> has been raised, the top section <NUM> with the patient <NUM> on it is extended into a bore of the gantry and into the plane of radiation. Alternatively, the couch <NUM> may be rotated without extending the top section <NUM> first, as illustrated in <FIG>. Then, after the couch <NUM> has been rotated, the top section <NUM> can then be extended as shown in <FIG>. The approximate position of a target region of the patient <NUM> is known prior to the treatment and so it can estimated by the operator or processor how far to extend the patient <NUM> into the bore so as to position the target region approximately at the same point as the isocenter <NUM>. This initial positioning (which includes the amount of vertical and longitudinal movement of the couch) can be performed by an operator using a control pad connected to the couch <NUM> or located remotely, and may be assisted by the use of lasers or markers on the patient's body. In one example, where the target region is on one side of the patient's body, the movement of the middle section <NUM> in a lateral direction can also be controlled at this stage to position the target region in the desired position.

In one example, the patient <NUM> is then scanned using the MR imaging apparatus <NUM> which allows the exact position of the target region, for example a tumour, to be determined. The operator or processor can then make any necessary small adjustments to the positioning of the different sections of the couch <NUM> according to the determined location of the target region in situ, so that the target region can be precisely located at the isocenter <NUM> or other desired location. When the couch <NUM> (and therefore the patient <NUM>) is in the correct starting position for the treatment, this position is recorded by the operator indicating that it is in the correct position, and the processor then stores this position and the relative positions of all of the sections in the processor memory as the start position.

The processor can then control the radiotherapy device by controlling the source of radiation <NUM> in such a way as to emit a treatment beam <NUM> and by rotating the gantry <NUM> so as to rotate the source of radiation <NUM> about the isocenter <NUM>, thus exposing the target region to a desired amount of radiation from a range of different angles, as is known in the art. In this example, once the patient <NUM> has been exposed to a desired level of radiation from the angles in the current plane of radiation, the source of radiation <NUM> is then temporarily stopped. In one example, the processor then instructs the rotation mechanism <NUM> to rotate from the first neutral position to a second rotated position, for example <NUM> degrees clockwise, which results in the couch <NUM> rotating to an angle of <NUM> degrees clockwise to a couch kick position. <FIG> and <FIG> illustrates the couch <NUM> in its raised, rotated and extended position. It should be noted that the rotation and the extension can occur one after another, in either order, or at the same time. At the same time, the processor is configured to instruct the middle and top sections <NUM>, <NUM> to extend laterally and/or longitudinally by the amount that is required in order to maintain the target region substantially at the isocenter <NUM>, whilst the couch <NUM> is in the rotated position. The rotation and the movement of the different sections <NUM>, <NUM> are executed simultaneously and in one example, are controlled at a speed that results in the same time for completion of each of the sections' movements and for the rotation, so that the patient <NUM> is moved smoothly into the rotated position, with minimal juddering that would be caused by the rotation and the sections moving sequentially. This maximises patient comfort <NUM> during the rotation.

Once the couch <NUM> is in its rotated and adjusted position, the processor instructs then controls the radiotherapy device in a similar manner to that described previously. The plane of radiation will then pass through a different part of the patient's body, except for at the isocenter <NUM>, at which the target region is located, which will be exposed to a second dose of radiation. Again, once the patient <NUM> or target region has been exposed to a desired amount of radiation, the radiation is stopped. The couch <NUM> can then be rotated to another angle with the sections <NUM>, <NUM> compensating for this rotation as described previously, and the process then repeated. This can be done for any number of different rotation angles (although in this example, limited by obstruction of the gantry cover to an angle of <NUM> degrees clockwise and anticlockwise of neutral). As described above, the treatment starts in the neutral position and then moves <NUM> degrees clockwise, which may then be followed by <NUM> and <NUM> degrees clockwise before <NUM>, <NUM> and <NUM> degrees anticlockwise (taken from neutral), thus resulting in a total of <NUM> doses of radiation at <NUM> different angles. Alternatively, the treatment could start by rotating the couch <NUM> to the maximum rotation angle in one direction and then only moving in one direction until the treatment was ready to finish. Many other such treatment plans are also possible.

Once the patient <NUM> has been exposed to the desired level of radiation from all the desired angles, the rotation mechanism <NUM> returns to its neutral, non-rotated, position, the sections <NUM>, <NUM> return to their neutral (retracted/non-extended) positions and the couch <NUM> is then vertically lowered, to enable the patient <NUM> to easily dismount. Being able to start with the couch <NUM> in a lowered position enables a low get on/get off height for the patient <NUM>, which can be an advantage for less mobile (for example overweight) patients <NUM>.

The couch <NUM> can be made out of many different materials. In one example, the table top <NUM> is made of or comprises a composite, such as carbon fibre or similar strength fibre such as Kevlar. The rotatable bracket <NUM>, the hinge <NUM>, the bottom section <NUM> and the middle section <NUM> can be made of a metal, such as steel, cast iron or aluminium or another appropriate material. In one example, the rotatable bracket <NUM> and the hinge <NUM> are made of steel, the bottom section <NUM> is made of steel or cast aluminium and the middle section <NUM> is made of aluminium, which could be cast, milled or a combination.

By mounting the rotation mechanism <NUM> directly to the gantry <NUM>, it enables the apparatus to be pre-aligned in a factory during manufacture. It also maintains an open floor area underneath the couch <NUM> which, for example, enables a patient <NUM> to more easily mount the couch <NUM>. It does not need extra space around the couch and therefore does not interfere with the radiotherapist (operator) during patient <NUM> positioning. Furthermore, this apparatus provides a couch kick (rotatable couch <NUM>) with a regular size of top and base. There is therefore no bulky construction to obstruct the radiotherapist.

As described in the embodiment above, the couch <NUM> comprises three different sections <NUM>, <NUM>, <NUM> all of which are responsible for a different axis of movement. However, it is also possible for the top and middle sections <NUM>, <NUM> to in fact only be one upper section that is configured to move in both directions, or at an angle oblique to these, as shall be described in more detail with reference to other embodiments.

The rotation of the patient support system <NUM> can occur before, during or after treatment. Rotation can be continuous or discrete/static. Rotation of the couch <NUM> may also occur with the top section <NUM> extended or not extended. Movement of the different sections <NUM>, <NUM>, <NUM> of the couch <NUM> can occur at the same time as each other and as the rotation of the couch <NUM>, or separately, sequentially. The speeds of the movement(s) can be controlled so that the time for a particular movement is the same as the time of a corresponding rotation at a particular speed. One or more of the movements of the sections <NUM>, <NUM>, <NUM> or the rotation of the rotation mechanism <NUM> can also be controlled manually by the operator, with the processor calculating and compensating for such a movement.

The couch <NUM> may include a number of rollers or other parts as well as the sections <NUM>, <NUM>, <NUM>. In these figures, the rotation mechanism <NUM> is connected directly to the gantry <NUM> but it could be connected to a floor, a wall or other support structure instead or as well. For example, when referring to the portion of the couch <NUM> being maintained substantially at the isocenter <NUM>, this could be actually at the isocenter <NUM> or within <NUM> to <NUM>, more preferably <NUM>, <NUM> to <NUM>, more preferably <NUM>, <NUM> to <NUM>, more preferably <NUM>, <NUM> to <NUM>, more preferably <NUM>, <NUM> to <NUM>, more preferably <NUM>, <NUM> to <NUM>, more preferably <NUM>, <NUM> to <NUM>, more preferably <NUM>, or another distance of the isocenter <NUM>.

Another embodiment is illustrated in <FIG>, <FIG>, <FIG>. These show a patient support surface <NUM> supported by and connected to a rotation mechanism <NUM>. The rotation mechanism <NUM> comprises a swivel arm <NUM>. The swivel arm <NUM> has two rotation axis and comprises first and second points of rotation <NUM>, <NUM>. The swivel arm <NUM> is connected to the floor towards the end of the swivel arm <NUM> closest to the radiotherapy device at the first point of rotation <NUM>. The swivel arm <NUM> can be connected directly to the floor at the first point of rotation <NUM>, or via an intermediary, such as a cog-wheel, and can be connected by any suitable means, for example, by a mechanical pivot. In one example, at the first point of rotation <NUM>, the swivel arm <NUM> is connected to the floor by a first cog-wheel rigidly connected to the floor. The swivel arm <NUM> is pivotally connected to the first cog-wheel. The swivel arm <NUM> is configured to rotate around the centre of the first cog-wheel, which is located at the first point of rotation <NUM>. The first cog-wheel is located underneath the swivel arm <NUM> (in other words, between the swivel arm <NUM> and the floor) but could instead be located above the swivel arm <NUM>.

The swivel arm <NUM> is connected towards the end further from the radiotherapy device, to the couch <NUM> at the second point of rotation <NUM>. The couch <NUM> can be connected directly to the swivel arm <NUM> at the second point of rotation <NUM>, or via an intermediary, such as a cog-wheel, and can be connected by any suitable means, for example, by a mechanical pivot. In one example, at the second point of rotation <NUM>, the swivel arm <NUM> is connected to the couch <NUM> by a second cog-wheel rigidly connected to the upper part of the couch <NUM>. The swivel arm <NUM> is pivotally connected to the second cog-wheel. The second cog-wheel and the couch <NUM> are rigidly connected and do not rotate relative to one another but are both configured to rotate together about the second point of rotation <NUM> and relative to the swivel arm <NUM>. The second cog-wheel is located underneath the swivel arm <NUM> (in other words, between the swivel arm <NUM> and the floor) but could instead be located above the swivel arm <NUM>.

The swivel arm <NUM>, first and second points of rotation <NUM>, <NUM> are all located outside of the plane of the gantry <NUM> and the plane of radiation. Accordingly, the rotation mechanism <NUM> is located outside the plane of the gantry <NUM> and outside the plane of radiation.

The swivel arm <NUM> may comprise a belt, chain wheel, cog or other suitable feature located at the first and second points of rotation <NUM>, <NUM>. The first and second rotation points <NUM>, <NUM> and the features located at these points may be connected by a connecting belt or chain <NUM>, as shown in <FIG>. The length of the swivel arm <NUM> (as given by the distance between the centres of the points of rotation) is half the distance between the isocenter <NUM> and the second rotation point <NUM>. The two rotation points are connected with a gear ratio of <NUM>:<NUM> between the first and second rotation points <NUM>, <NUM> respectively. This is achieved by a variety of suitable means, for example the use of cog-wheels located at the rotation points, as described above. In one example, at each of the first and second rotation points <NUM>, <NUM>, there is a steel shaft, two (angular-contact) bearings and a chain or cogged belt wheel. The connection between the two rotation points <NUM>, <NUM> may be a chain or cogged belt.

The two cog-wheels, chain wheels or other features located at the rotation points act as transmission components, which facilitate a co-ordinated rotation of the swivel arm <NUM> with respect to the floor and the couch <NUM> with respect to the swivel arm <NUM>. For example, a first wheel is rigidly connected to the floor at the first rotation point <NUM> and a second wheel is rigidly connected to the couch <NUM> at the second rotation point <NUM>. The swivel arm <NUM> is pivotally connected to the first wheel and to the second wheel. In one mode of operation, the couch is rotated by the application of an external force (for example it is pushed manually by an operator). With the wheels serving as transmission points for the rotation, the rotation mechanism <NUM> enables the couch <NUM> to automatically rotate about an axis that is parallel to and spaced from an axis that passes through the isocenter <NUM>, without even needing a motor to drive the rotation.

Alternatively, the rotation of the chain wheels can be driven by one or more motors in such a way that, when the first wheel, located at the first point of rotation <NUM> is rotated, the second wheel, located at the second point of rotation <NUM> rotates at half the speed. This, together with the distances identified above, causes the couch <NUM> to rotate about an axis that is parallel to and spaced from an axis that passes through the isocenter <NUM> in such a way that the longitudinal axis of the couch <NUM> always points towards the isocenter <NUM>, as illustrated in <FIG>.

It is apparent that there are other examples of configurations that would result in a similar rotation of the couch <NUM>. For example, if the first cog-wheel is rigidly connected to the swivel arm <NUM> and pivotally connected to the floor or the second cog-wheel is rigidly connected to the swivel arm <NUM> and pivotally connected to the couch <NUM>.

The patient support system <NUM> may include a number of rollers, a top (or upper) section <NUM>, a bottom section <NUM>, or other parts. As illustrated in <FIG>, the couch <NUM> can extend vertically and/or longitudinally to enable optimised positioning of the patient <NUM> under the treatment beam <NUM>, by maintaining a portion of the subject support surface <NUM> substantially at the isocenter <NUM>. When the couch <NUM> is rotated, the position of the couch <NUM> relative to the isocenter <NUM> varies for a given rotation angle, as described previously. This is illustrated in <FIG> which show the isocenter <NUM> located at a different part of the couch <NUM> for the two different rotation angles shown. Accordingly, the couch <NUM> (or a portion thereof in the form of a top section <NUM>) is extended along the longitudinal axis <NUM> of the couch <NUM> in its rotated position, to compensate for this change of distance. This extension can be performed manually or can be controlled by a processor, such as a processor that also controls the rotation of the couch <NUM>. The extension of the couch <NUM> or portion thereof can therefore be synchronised with the rotation of the couch <NUM> in such a way as to maintain optimised positioning of the patient <NUM> under the treatment beam <NUM>.

Furthermore, the couch <NUM> or top section <NUM> can be rotated around the axis of the bore (rolled), and/or pivoted, as well as extended. In this way, it is possible to achieve six axis degree of freedom with regard to positioning a patient <NUM>. In order for the couch <NUM> to extend the top section <NUM>, electrical power can be supplied to the couch <NUM> via a cable <NUM> running from a power source and through the swivel arm <NUM>. It is also possible for other cables to be passed through the swivel arm <NUM>, for example, for sending control signals to the couch <NUM>.

The first rotation point <NUM> of the swivel arm <NUM> is located at a position along the axis of the bore <NUM>. When the swivel arm <NUM> is parallel to the axis of the bore, the second rotation point is also located at a position along the axis of the bore <NUM>. Accordingly, in the neutral position of the couch <NUM>, the isocenter <NUM> and the first and second points of rotation (<NUM>, <NUM>) are all aligned, as illustrated in <FIG> shows the axis <NUM> of the longitudinal centreline of the couch <NUM> passing through the isocenter <NUM> when the couch <NUM> is in a rotated position. This rotation is caused automatically due to the configuration of the rotation mechanism <NUM>, as described above.

The rotation of the patient positioning system <NUM> can occur before, during or after treatment. Rotation can be continuous or discrete/static. Rotation of the couch <NUM> may also occur with the top section <NUM> extended or not extended. Rotation of the couch <NUM> can also occur at the same time as top section <NUM> is being extended. In one example, a patient <NUM> lies on the couch <NUM> in its non-extended position. The couch <NUM> is then extended, the patient <NUM> is scanned and exposed to radiation. The radiation is then stopped, the couch <NUM> is rotated (yawed) by rotating the swivel arm <NUM> about the first and second rotation points <NUM>, <NUM> as shown in <FIG> and the patient <NUM> is then exposed to further radiation. In another example, the radiation is not stopped and the rotation of the couch <NUM> happens automatically and at the same time as the patient <NUM> is exposed to radiation.

The rotation about the first point of rotation <NUM> may be clockwise or anticlockwise. The rotation of the second point of rotation <NUM> is in the opposite direction to that of the first rotation point <NUM>. It should be understood that when talking about the first and second points of rotation <NUM>, <NUM>, reference may be made to whatever physical entity is located at the point of rotation, such as an axle, motor or cog. The speed of rotation at the second point of rotation <NUM> is half that at the first point of rotation <NUM>. This rotation may be caused by any appropriate means. For example, rotation of the first point of rotation <NUM> can be caused by a motor. The speed of the rotation at the first point of rotation <NUM> may be controller by a processor, which may be comprised in the patient support surface <NUM> or may be found elsewhere, for example in a control room. The rotation at the second point of rotation <NUM> may then be caused by a mechanical or physical connection with the first point of rotation <NUM>.

Alternatively, the speed of rotation at both points of rotation <NUM>, <NUM> may be controlled by the processor. For example, the processor might send a signal to a motor configured to cause rotation of the swivel arm <NUM> at the first point of rotation <NUM> and instruct the motor to cause rotation at a speed of <NUM> revolution per minute. The processor may also send a signal to a different motor configured to cause rotation of the swivel arm <NUM> at the second point of rotation <NUM> to cause rotation of the couch <NUM> on top of the swivel arm <NUM> at a speed of <NUM> revolutions per minute. These speeds are only examples and other speeds are possible. The speed of rotation should not be so great as to cause patient <NUM> discomfort but not slow as to be inefficient and increase treatment times. The placement of the motor, if used, is not essential for the function of the apparatus. There could be one or more motors located at any of the first rotation point <NUM>, the second rotation point <NUM> or even somewhere in between the rotation points acting directly on the belt or chain connecting these rotation points. Alternatively, as described above, there may not be any motor and the couch <NUM> is rotated manually, whilst using the configuration of the apparatus to achieve the particular rotation of the couch <NUM>.

The same processor may also be used to control the radiation emission or other operation of the radiotherapy device. This allows the rotation of the couch <NUM> to be synchronized with the delivery of the radiotherapy treatment. Alternatively, the operation of the radiotherapy device and the radiotherapy treatment may be controlled by a different, separate processor.

When installing the rotation mechanism <NUM> and the couch <NUM>, the position of the couch <NUM> may be calibrated before use. This can be done by, for example, positioning the couch <NUM> in a neutral position with the longitudinal axis <NUM> of the couch <NUM> in its neutral position parallel to the longitudinal axis of the swivel arm <NUM>. This may be set as <NUM><NUM> of rotation and the subsequent rotation of the couch <NUM> can be measured about this position. The neutral position is when the longitudinal axis <NUM> of the couch <NUM> is aligned with the axis of the bore of the gantry <NUM> (which may be perpendicular to the radiation plane in some configurations, and parallel to the floor (as shown in <FIG>). When the patient support system <NUM> is fully extended into the bore, there may be less rotation possible compared to when the patient support system <NUM> is not extended, or only partially extended, into the bore. As a result, this system is particularly well suited to treatments for head and neck.

The swivel arm <NUM> can by made from one or more different materials, for example, steel such as a welded steel sheet metal structure, cast iron, aluminium, titanium, composite, or any other material with high rigidity that is suitable to support the required loads.

Another embodiment is illustrated in <FIG>. These show a patient support surface <NUM> supported by and connected to a rotation mechanism <NUM>. The rotation mechanism <NUM> comprises a first sliding base <NUM> located on a first side of the gantry <NUM>, a second sliding base <NUM> located on a second side of the gantry <NUM>, a first support member <NUM>, a second support member <NUM> and a third support member <NUM>. The first sliding base <NUM> is connected to and supports the first support member <NUM> and the second support member <NUM>. The second sliding base <NUM> is connected to and supports the third support member <NUM>. The couch <NUM> is connected to and supported by the first and second support members <NUM>, <NUM> at the proximal end of the couch <NUM>. The couch <NUM> is connected to and supported by the third support member <NUM> at the distal end of the couch <NUM>. The section of the couch <NUM> that is connected to the first, second and third support members <NUM>, <NUM>, <NUM> may also be referred to as a bridge or bottom section.

The first sliding base <NUM> in one example is mounted directly to the gantry <NUM> or a portion of the gantry, which protrudes <NUM>-<NUM> underneath the level of the floor so that the first sliding base <NUM> is mounted on the part of the gantry <NUM> that is underneath the floor. The first sliding base <NUM> is configured to move from a first position to a second position in a lateral direction along a guide rail mounted to the portion of the gantry <NUM> beneath the floor. Alternatively, the first sliding base <NUM> is supported by the floor itself and is configured to move from a first position to a second position in a lateral direction <NUM> along the floor. Similarly, the second sliding base <NUM> in one example is mounted directly to the gantry <NUM> or a portion of the gantry, which protrudes <NUM>-<NUM> underneath the level of the floor so that the second sliding base <NUM> is mounted on the part of the gantry <NUM> that is underneath the floor. The second sliding base <NUM> is configured to move from a first position to a second position in a lateral direction along a guide rail mounted to the portion of the gantry <NUM> beneath the floor. Alternatively, the second sliding base <NUM> is supported by the floor itself and is also configured to move from a first position to a second position in a lateral direction <NUM> along the floor. In one example, the first and second sliding bases <NUM>, <NUM> are guided during this lateral movement by guide rails that are set into the floor and supported by the portion of the gantry that is beneath the floor. In another example, the first and second sliding bases <NUM>, <NUM> are guided by first and second elongated slots in the floor, along which the sliding bases <NUM>, <NUM> are configured to slide. The longitudinal axis of the elongated slots is aligned with the lateral axis <NUM> of the couch <NUM> in its neutral position (neutral lateral axis <NUM>), which means that the sliding bases <NUM>, <NUM> are configured to slide, parallel to each other, along a neutral lateral axis <NUM>. For example, the first and second sliding bases <NUM>, <NUM> move along linear movement guide rails and are driven by motors controlled by a processor and/or operated with, for example, one or more buttons.

The first and second support members <NUM>, <NUM>, which are both connected to the first sliding base <NUM>, are both aligned along the neutral lateral axis <NUM> and are spaced apart from one another but both equidistant from the centre point of the first sliding base <NUM>. The third support member <NUM> is connected to the second sliding base <NUM> and is located at the centre point of the second sliding base <NUM>.

The couch <NUM> comprises a bottom section <NUM> (bridge) and a top section <NUM>, which is supported by the bottom section <NUM>. The bottom section <NUM> is connected to the rotation mechanism <NUM> at three points. The second support member <NUM> is rotatably connected to the bottom section <NUM> at connection point <NUM>. For example, this connection can be a ball and socket joint, as shown in <FIG>, with the ball comprised as part of the second support member <NUM> and the socket comprised in the bottom section <NUM> of the couch <NUM> or vice versa. In this way, the bottom section <NUM> may be rotated about an axis of rotation that passes through the second support member <NUM> and the connection point <NUM>.

In order to enable such a rotation, the first support member <NUM> is movably connected to the bottom section <NUM> at a point that varies as the bottom section <NUM> is rotated about the second support member <NUM>. To enable this point of connection to the bottom section <NUM> to move, the bottom section <NUM> comprises a curved slot/guide <NUM> (as shown in <FIG>), which is along an arc of a circle lying in the plane of the bottom section <NUM>, wherein the circle has its centre point at the connection point <NUM>. The bottom section <NUM> is movably connected to the first support member <NUM> by a ball and slot (elongated socket) in a kinematic joint configuration or equivalent other type of connection. Other kinematic joint configurations are also possible so long as they allow motion in some directions and constrain it in others. This connection enables rotation, longitudinal and lateral movement to accommodate the rotation of the couch <NUM> or bridge. The first support member <NUM> is prevented from passing through the bottom section <NUM> because the opening of the slot <NUM> in the bottom section <NUM> is smaller than the size of the ball on the top of the first support member. In another example, the slot <NUM> does not go all the way through the bottom section <NUM> but is instead only exposed on the underside of the bottom section <NUM>.

The bottom section <NUM> also comprises an elongated slot/guide <NUM> located at a portion of the longitudinal centre line of the bottom section <NUM>. The elongated slot <NUM> is contained within the bottom section <NUM> and is substantially located at the distal end of the couch <NUM> but may extend through the plane of the gantry <NUM> in some configurations. The third support member <NUM> is movably connected to the bottom section <NUM>. In one example, they are connected by a ball and slot in a kinematic joint configuration but can also be connected by another equivalent joint. The third support member <NUM> is prevented from passing through the bottom section <NUM> because the opening of the slot <NUM> in the bottom section <NUM> is smaller than the size of the ball on the top of the third support member <NUM>. When the bottom section <NUM> is rotated (about the connection point <NUM>), the elongated slot <NUM> enables the third support member <NUM> to move from a first position to a second position along the longitudinal axis <NUM> of the couch <NUM>. This movement accommodates the relative longitudinal extension of the bottom section <NUM> that is caused by the rotation of the couch <NUM>.

<FIG> shows a view from underneath the level of the couch <NUM> and clearly illustrates the connection between the first sliding base <NUM>, which is set into the floor, and the first and second support members <NUM>, <NUM>. As illustrated by the arrows at the connection points <NUM>, <NUM>, <NUM>, these connections allow <NUM> degrees of freedom so that the couch <NUM> can be rotated, tilted and pitched whilst remaining connected to the first, second and third support members <NUM>, <NUM>, <NUM> at the connection points <NUM>, <NUM>, <NUM>.

The sliding bases <NUM>, <NUM> can both be moved in sync and in the same direction to produce pure lateral movement of the couch <NUM>, as shown in <FIG>. In one example, the lateral movement of the couch <NUM> can be controlled as part of a treatment plan, and may be controlled in conjunction with a rotation of the couch <NUM> and/or a movement of the top section <NUM>. The rotation of the couch <NUM> is driven by the lateral movement of only one of the sliding bases <NUM>, <NUM>, or both of the sliding bases <NUM>, <NUM> moving in the same direction but at different rates, or both of the sliding bases <NUM>, <NUM> moving in opposite directions, at the same or different rates, resulting in a rotated configuration as shown in <FIG>. The movement of the sliding bases <NUM>, <NUM> can be at the same time or at different times, whatever the direction. Moving the sliding bases <NUM>, <NUM> in opposite directions enables the couch <NUM> to be rotated to the maximum possible angle. For example, if the first sliding member <NUM> moves in a first direction (along the neutral lateral axis <NUM>) and the second sliding member <NUM> moves in the opposite direction, this will cause the couch <NUM> to rotate because it is connected to the second support member <NUM> at the point <NUM> and the second support member <NUM> is connected to the first sliding member <NUM>. The curved slot <NUM> and the elongated slot <NUM> are configured to accommodate the rotation of the couch <NUM>. The movement of the sliding bases <NUM>, <NUM> is controlled by a processor, which can be the same that controls any or all other functions of the apparatus. By controlling the movement of the sliding bases <NUM>, <NUM>, the processor can cause the couch <NUM> to rotate and can control the effective rotation of the couch <NUM> by controlling the relative movement of the sliding bases <NUM>, <NUM>. The processor can also control the movement of the couch <NUM> along the neutral lateral axis <NUM>.

The top section <NUM> is configured to move from a first position to a second position along at least one of a longitudinal direction <NUM> and a lateral direction <NUM>. When the couch <NUM> is rotated by the rotation mechanism <NUM>, as described above, the axis of rotation of the couch <NUM> passes through the longitudinal axis of the second support member <NUM>, which is itself moved along the neutral lateral axis <NUM>. Accordingly, the rotation mechanism <NUM> is configured to rotate the couch <NUM> about an axis of rotation parallel to and spaced from an axis that passes through the isocenter <NUM>. As explained previously, this causes a portion of the couch <NUM> to move away from the isocenter <NUM>. This can be compensated for by moving the third support member <NUM>, supported by the sliding base <NUM> in the opposite direction from the movement of the sliding base <NUM>. The lateral movement of the couch <NUM> can also be used to compensate for the movement of the portion away from the isocenter <NUM> that is caused by the rotation of the couch <NUM>. The top section <NUM> can also be used to compensate for the movement of this portion of the couch <NUM> in such a way as to maintain the portion of the subject support surface <NUM> substantially at the isocenter <NUM>. The amount of movement required by the top section <NUM> so as to maintain a portion of the subject support surface <NUM> substantially at the isocenter <NUM> is proportional to the rotation and the lateral movement of the couch <NUM>. Accordingly, the top section <NUM> can be moved in, for example, a longitudinal direction as a function of the rotation of the subject support surface <NUM> and/or a function of the lateral movement of the couch <NUM> or a particular one of the sliding bases <NUM>, <NUM>. The movement of the top section <NUM> of the couch <NUM> is controlled by a processor as a function of the rotation of subject support surface <NUM> so as to maintain the portion of the subject support surface <NUM> substantially at the isocenter <NUM>. In one example, where the neutral longitudinal axis <NUM> of the couch is initially aligned with the axis of the bore and the rotation of the couch <NUM> by the rotation mechanism <NUM> involves moving the first and second sliding bases <NUM>, <NUM> by an equal amount but in opposite directions, no movement of the top section <NUM> may be necessary to maintain a particular portion of the couch <NUM> substantially at the isocenter <NUM>.

The processor is configured to determine the present location of the first and second sliding bases <NUM>, <NUM> and therefore the position of the first, second and third support members <NUM>, <NUM>, <NUM>, the rotation angle of the couch <NUM> and the extension/position of the top section <NUM>. The processor can use this information to calculate the amount of compensation that is needed for a particular rotation angle. The processor then instructs the top section <NUM> to move by the required amount.

As well as controlling the movement of the top section <NUM> to maintain the portion of the subject support surface <NUM> substantially at the isocenter <NUM>, it is also possible to control the lateral movement of the rotation mechanism <NUM> (and thereby the couch <NUM> itself, which is supported by the rotation mechanism <NUM>) so as to help maintain the portion of the subject support surface <NUM> substantially at the isocenter <NUM>. As explained previously, this lateral movement can be achieved by moving the two sliding bases <NUM>, <NUM> in sync in a particular direction. This can be controlled by the processor.

In one example, the processor controls a longitudinal movement of the top section <NUM> at the same time as a lateral movement of the rotation mechanism <NUM> both as a function of the rotation angle of the couch <NUM> in such a way as to maintain a portion of the subject support surface <NUM> substantially at the isocenter <NUM>.

The first, second and third support members <NUM>, <NUM>, <NUM> are extendable or retractable in a vertical direction <NUM>. For example, each support member is a telescopic support, which can be extended by any appropriate means, for example an internal screw mechanism, a piston, linear motors or a belt drive. The extension of each of these support members <NUM>, <NUM>, <NUM> can be controlled independently by the processor. By controlling the extension of these support members <NUM>, <NUM>, <NUM>, the couch <NUM> can also be rotated around the longitudinal axis <NUM> of the couch <NUM> (rolled), and/or rotated about the lateral axis <NUM> of couch <NUM> (pivoted). Thus, the processor is configured to control the roll and tilt of the couch <NUM>, which can be controlled as part of a treatment or treatment plan. In this way, it is possible to position a patient <NUM> with six degrees of freedom. These additional types of rotations can occur whilst the couch is in a neutral rotational position (yaw) or when it is in a rotated position.

For example, as shown in <FIG>, the couch <NUM> can be pitched in such a way that the distal end of the couch <NUM> is raised and the proximal end of the couch <NUM> is lowered. This is achieved by extending the third support member <NUM> at the same time as retracting the first and second support members <NUM>, <NUM>. This can also be combined with an extension/retraction of the top section <NUM> of the couch <NUM> so that a part of the couch <NUM> is lowered beneath the height of the bottom of the bore and so as to enable a patient <NUM> to more easily climb onto the couch <NUM> (as shown in <FIG>). Pitch can also be used as part of a treatment to help spread the radiation through the healthy tissue, similarly to how this is achieved by rotating the couch <NUM>.

For a similar reason, it may be desirable to roll the couch <NUM> as part of the treatment, as shown in <FIG>. This can be achieved by, for example, retracting/lowering the height of the first support member <NUM> and extending/raising the height of the second support member <NUM>, which will cause the couch <NUM> to roll towards the first support member <NUM>. This can be performed as part of a treatment, although normally the roll angle will be kept low to maintain patient <NUM> comfort. In order to accommodate the roll and tilt of the couch <NUM>, the attachment points of the first, second and third support members <NUM>, <NUM>, <NUM> to the couch <NUM> are designed to enable such a movement. As described previously, in one example, the attachment point <NUM> is a ball and socket joint while the other connections are a ball and slot joint, in which the ball if contained within the slot but is free to move along it whilst also allowing for tilt and roll of the couch <NUM>.

In order to control the rotation, pitch and roll of the couch <NUM> as well as the lateral movement of the couch <NUM> and the extension of the top section <NUM>, it is necessary for the control system, which may be implemented by the processor, to have feedback regarding the positions/states of the different components including the first and second sliding bases <NUM>, <NUM>, the amount of extension or current height of the first, second and third support members <NUM>, <NUM>, <NUM> and the position of the top section <NUM> relative to the bottom section/bridge <NUM>. Therefore, a number of sensors may be used to provide this feedback. For example, an absolute encoder may be used to determine the amount of movement that a particular motor has caused in relation to one of the above measurements. There are many appropriate ways of receiving the feedback of the positions and any suitable means can be used.

The processor may also be configured to use data from a memory that stores information such as the dimensions and configuration of the components so that these can be used in the calculations controlling the movement of the assorted components and to prevent, for example, the couch <NUM> from colliding with the gantry <NUM>.

It should be noted that the various embodiments may be implemented in hardware, software or a combination thereof. The various embodiments and/or components, for example, components and controllers for these, also may be implemented as part of one or more computers or processors or field-programmable gate arrays (FPGAs). The computer or processor or FPGA may include a computing device, an input device, a display unit and an interface, for example, for accessing the Internet. The computer or processor may include a microprocessor. The microprocessor may be connected to a communication bus. The computer or processor or FPGA may also include a memory. The memory may include Random Access Memory (RAM) and Read Only Memory (ROM). The computer or processor or FPGA further may include a storage device, which may be a hard disk drive or a removable storage drive such as an optical disk drive, and the like. The storage device may also be other similar means for loading computer programs or other instructions into the computer or processor.

The disclosure of this embodiment is only exemplary and there are many variations possible that will result in the same or similar effects, as will be apparent to the skilled person. As one example, whilst the third support member <NUM> has been described as being in the middle of the second sliding base <NUM>, it could just as well be positioned off centre of the second sliding base <NUM> and the processor would account for this when controlling the movement. Thus, the above description comprises examples, often preferred examples, of the disclosed embodiments but strict literal compliance with the meaning of the words is not intended and there will be other variations apparent to the skilled person that result in substantially the same effect.

As has been described in the embodiments above, the couch <NUM> comprises means to allow it to move vertically in relation to the rotation mechanism <NUM>. The means to enable the vertical movement can be comprised within the couch <NUM>, within the rotation mechanism <NUM> or shared between these. Alternatively, the rotation mechanism <NUM> itself can be moved in a vertical direction so as to effectively raise or lower the couch <NUM>. The patient support surface <NUM> can move in any direction.

As well as rotating the couch <NUM> about a vertical axis <NUM>, the couch <NUM> or one or more sections <NUM>, <NUM>, <NUM> of the couch <NUM> can also be rotated around the longitudinal axis <NUM> of the couch <NUM> (rolled), and/or rotated about the lateral axis <NUM> of couch <NUM> (pivoted). In this way, it is possible to position a patient <NUM> with six degrees of freedom. These additional types of rotations can occur whilst the couch is in a neutral rotational position (yaw) or when it is in a rotated position. For reasons of patient <NUM> comfort and to prevent from them from having to be strapped to the couch <NUM>, the amount of roll and tilt will usually be limited to a small amount, for example, a tilt of <NUM> degrees forwards or backwards may be used in conjunction with the rotation about the vertical axis <NUM> that is described more generally herein. In some examples, the couch <NUM> of section thereof is pitched about an axis that is spaced apart from the isocenter <NUM> whilst a different section is moved to compensate and maintain a portion of the couch <NUM> substantially at the isocenter <NUM>. In this way, it is possible to maximise the spread of the radiation through the healthy tissue whilst maximising the dose of radiation that is received at the target region.

The radiation source or gantry <NUM> itself may also be partially rotated about the transverse axis of the short end of the patient support surface <NUM> in its neutral position (pitched), although not necessary when the patient support surface <NUM> is in its neutral position, either at the same time, or a different time, synchronously or separately to the patient support surface <NUM>. This can also be controlled by the same processor as part of a treatment.

The embodiments described above enable use of a couch kick (rotatable couch <NUM>) in a ring gantry based linac system. It effectively provides isocentric couch rotation but without requiring physical rotation about the isocenter <NUM>.

If a section of the couch was not moved as a function of the rotation of the couch <NUM> (given that the rotation is not about the isocenter <NUM>), then the location of the target region would move with respect to the isocenter <NUM> (and focus of the radiation) and, accordingly, this would result in an increased dosage of radiation being received by healthy tissue. Furthermore, this would result in a longer treatment time because the target region would not receive the intended dosage of radiation.

By rotating the couch <NUM> and hence the patient <NUM>, whilst maintaining a particular portion substantially at the isocenter <NUM>, the radiation dose can be spread through the healthy tissue so that the radiation dose received by healthy tissue surrounding a target region is minimised.

Claim 1:
A radiotherapy apparatus for delivering radiation to a subject, the apparatus comprising:
a source of radiation (<NUM>) configured to rotate about an isocenter (<NUM>) and emit radiation in a radiation plane containing said isocentre;
a subject support surface (<NUM>) including a portion configured to be located substantially at the isocenter, the subject support surface comprising:
a subject support surface rotation mechanism (<NUM>) configured to rotate the subject support surface about an axis of rotation parallel to and spaced from an axis that passes through the isocentre; and
a first section configured to move from a first position to a second position along at least one of a longitudinal and lateral direction; and the apparatus further comprising
a processor configured to control the longitudinal and/or lateral movement of the first section as a function of the rotation of the subject support surface to maintain the portion of the subject support surface substantially at the isocenter; wherein the rotation mechanism is distributed on both sides of the radiation plane, wherein the rotation mechanism is connected to: a proximal end of the subject support surface on one side of the radiation plane; and a distal end of the subject support surface on the other side of the radiation plane.