Patent Publication Number: US-2022233885-A1

Title: Radiation therapy system

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a national filing in the US of International Patent Application No. PCT/EP2020/000031, filed Jan. 31, 2020 which claims benefit of Great Britain Patent Application No. 1905568.0, filed Apr. 18, 2019. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to radiation therapy systems. The invention relates particularly, but not exclusively, to hadron beam therapy systems. 
     BACKGROUND TO THE INVENTION 
     Treatment of cancer and other illnesses using charged particles such as protons and ions is known but is currently prohibitively expensive. The main cost drivers of proton and ion beam therapy are the proton and ion accelerators and beam transport systems, which typically require very large gantries and large, typically multi-storey, buildings. The gantries themselves require high-tech engineering, with low production volume and are therefore expensive. The placement of the treatment rooms, which tend to be spread out over a large area also increases the overall cost. Single treatment room systems have also been proposed, but these are also housed in large buildings with large complex gantries, and are relatively expensive because of the provision for only one treatment room. Particle accelerators can weight in excess of 100 tonnes, which is beyond the lifting capabilities of modern robots, and so the particle accelerators tend to be static during use, the radiation beam being transported to the treatment room by a beam transport system comprising a relatively long beam transport line terminating with a delivery nozzle. The foot print of the building is determined by the length and shape of the beam line feeding the various treatment rooms, and the beam line requires shielding along its entire length. Moreover, the beam lines invariably bend to reach their destination and this complicates the system, increasing its expense and reducing its efficiency. In addition, with conventional treatment systems it is difficult to make efficient use of the radiation equipment given the relatively long times required to set up the equipment for each patient and for organising the patients themselves. Unfortunately therefore the benefits of, in particular, proton therapy have been overshadowed by the relatively high cost of conventional hospital based facilities. 
     SUMMARY OF THE INVENTION 
     It would be desirable to provide a radiation therapy system that mitigates at least some of the problems outlined above and makes hadron therapy less expensive than is conventionally achievable. 
     An aspect of the invention provides a radiation therapy system comprising a treatment pod having an internal treatment room and a beam delivery system comprising a particle accelerator for generating a radiation beam. The beam delivery system is carried by the treatment pod and is configured to deliver the radiation beam to the treatment room. The said beam delivery system is movable with respect to the treatment pod in order to adjust the position of the radiation beam with respect to the treatment room. 
     The beam delivery system may be moveable, at least partly and optionally fully, around the pod and around the treatment room, preferably in an orbital manner. Said beam delivery system may be rotatable about an axis of said treatment pod, preferably the longitudinal axis of said treatment pod. 
     The particle accelerator may be located externally of the treatment pod. 
     In typical embodiments, the beam delivery system includes a beam delivery nozzle, and the beam delivery nozzle is located inside said treatment room. 
     The treatment pod typically comprises a hollow body structure that defines the treatment room, the beam delivery system being carried by the body structure. Preferably, the beam delivery system is coupled to the treatment pod, conveniently to the body structure, with the particle accelerator located outside of the body structure and the beam delivery nozzle extending through the body structure. The body structure may comprise a solid sleeve-like wall extending around a longitudinal axis of the pod. 
     In some embodiments, the body structure includes a rotatable section, the beam delivery system being coupled to said rotatable section, and wherein, typically, the body structure includes first and second end sections, said rotatable section being located between and rotatable with respect to said first and second end sections. 
     Typically, the pod has first and second ends, either one or both of which are open to provide access to the treatment room. 
     The treatment pod may include a counterbalance, which is preferably located externally of the pod, the counterbalance being arranged to counterbalance movement of the beam delivery system with respect to the treatment pod, the counterbalance preferably being arranged to counterbalance rotational movement of the beam delivery system about a rotation axis, the rotation axis preferably being the longitudinal axis of the pod. The counterbalance is preferably rotatable around the pod together with the beam delivery system, and is preferably oppositely disposed to the beam delivery system with respect to the rotational axis. 
     The counterbalance may be coupled to the body structure, preferably to a rotatable section of said body structure, and is preferably located outside of the body structure. 
     Optionally, said counterbalance comprises a second beam delivery system comprising a second particle accelerator for generating a second radiation beam, and being configured to deliver said second radiation beam into said treatment room, said second particle accelerator preferably being located externally of said pod. 
     In some embodiments, the system includes a plurality of waiting rooms, said treatment pod being aligned with, or movable into alignment with, each of said waiting rooms to allow access to the treatment room from each waiting room. The treatment pod and beam delivery system are movable together as an assembly. Advantageously, the waiting rooms are arranged in at least one pair of oppositely disposed waiting rooms, the respective waiting rooms of the, or each, pair being spaced apart with their respective doorway facing each other, and wherein said treatment pod is locatable between the respective waiting rooms of the, or each, pair to allow access to the treatment room from either of the respective waiting rooms. 
     In some embodiments, there is a single pair of oppositely disposed waiting rooms, the treatment pod being located between, and aligned with, each waiting room. In other embodiments, there are multiple pairs of oppositely disposed waiting rooms, and wherein said treatment pod is movable into alignment with any one of said pairs of waiting rooms. The multiple pairs of waiting rooms may be arranged to define a common passage between opposing waiting rooms, and wherein said treatment pod is located in and movable along said passage. The multiple pairs of waiting rooms may be arranged in a linear array such that said common passage is linear. The multiple pairs of waiting rooms may be arranged such that said common passage is circular or curvilinear. 
     In some embodiments, said plurality of waiting rooms are arranged in a linear, circular or curvilinear array, said treatment pod being movable into alignment with any one of said waiting rooms to allow access to the treatment room from each waiting room. 
     In some embodiments, the system includes conveyancing means for moving said treatment pod into alignment with any one of said waiting rooms, or any two oppositely disposed waiting rooms. 
     Optionally, said waiting rooms are arranged in multiple storeys, said system including a lift device for moving said treatment pod between said storeys. 
     In some embodiments, the system includes a bay, or other housing structure, for housing the treatment pod, the treatment pod being supported above a floor of the bay to provide space below the treatment pod to accommodate the particle accelerator as the beam delivery system rotates. The bay typically provides said passage. 
     In some embodiments, the system further includes a radiation shielding structure that at least partly surrounds the treatment pod and the beam delivery system. The radiation shielding structure may comprise a top shield section located so as to provide radiation shielding above the treatment pod and beam delivery system; first and second side shield sections located so as to provide radiation shielding at opposite sides, respectively, of the treatment pod and the beam delivery system, and first and second end shield sections located so as to provide radiation shielding at opposite ends, respectively, of the treatment pod and the beam delivery system. 
     The radiation shielding structure may enclose the treatment pod and the beam delivery system at least from above, at opposite sides and at opposite ends. 
     The radiation shielding structure may comprise at least one doorway aligned with a respective doorway of the treatment pod, each doorway having a respective door formed at least partly from radiation shielding material. 
     Another aspect the invention provides a system that may be the same or similar to the system of the prior aspect except that the beam delivery system may be any other type of therapy delivery system, not necessarily a particle or hadron therapy system, and therefore not necessarily including a particle accelerator. 
     From yet another aspect the invention provides a system that may be the same or similar to the system of the prior aspects except that the beam delivery system may be in a fixed location with respect to the pod. 
     Although embodiments of the invention are described herein in the context of a radiation therapy system having a beam delivery system comprising a particle accelerator for generating a radiation beam, the invention may alternatively be used with other beam delivery systems that do not include a particle accelerator, instead comprising means for generating other types of beam, e.g. an ultrasound beam. Alternatively, the beam delivery system may be replaced by an alternative patient treatment system or patient scanning system, e.g. MRI scanning equipment or CT scanning equipment. 
     Other advantageous aspects of the invention will be apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments and with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are now described by way of example and with reference to the accompanying drawings in which like numerals are used to denote like parts and in which: 
         FIG. 1  is a first perspective view of a radiation therapy system embodying one aspect of the present invention, some of the components of the system being shown as transparent in order not to obscure other components from view; 
         FIG. 2  is a second perspective view of the radiation therapy system of  FIG. 1 ; 
         FIG. 3  is a third perspective view of the radiation therapy system of  FIG. 1 ; 
         FIG. 4  is a side sectioned view of the radiation therapy system of  FIG. 1 ; 
         FIG. 5  is an end sectioned view of the radiation therapy system of  FIG. 1 ; 
         FIG. 6  is a first view of a waiting room and a treatment room, each room being part of the radiation therapy system of  FIG. 1 ; 
         FIG. 7  is a second view of the waiting room and the treatment room of  FIG. 6 ; 
         FIG. 8  is a perspective view of an alternative embodiment of a radiation therapy system according to the invention; 
         FIG. 9  is a sectioned end view of the system of  FIG. 8 ; and 
         FIG. 10  is a sectioned plan view of the system of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring now in particular to  FIGS. 1 to 5  of the drawings there is shown, generally indicated as  10 , a radiation therapy system embodying one aspect of the present invention. The system  10  includes a radiation beam delivery system  12  and may be described as an external beam radiotherapy (EBRT) system. The beam delivery system  12  comprises a particle accelerator  16 . The particle accelerator  16  may comprise any suitable conventional particle accelerator, for example a linear accelerator, a cyclotron, a synchro-cyclotron, a synchrotron, or a laser based accelerator, and produces a radiation beam (not illustrated) for use in patient treatments, in particular tumour RT. The radiation beam typically comprises ionizing radiation. The nature of the radiation beam depends on the radiation source (not shown) with which the particle accelerator  16  is used. In preferred embodiments, the radiation source comprises a source of protons. As such the radiation beam comprises a proton beam and the system  10  may be described as a proton therapy system. Alternatively, the radiation source may comprise other suitable particles, especially but not exclusively charged particles, for example ions (e.g. Carbon ions, Helium ions or Neon ions), atoms, photons or other sub-atomic particles such as electrons, alpha particles, beta particles, negative pi mesons or neutrons, or any particle suitable for use in particle therapy or hadron therapy. Hence, in alternative embodiments the radiation beam may comprise, for example, an ion beam, electron beam (especially a relativistic electron beam), a neutron beam, photon beam gamma-ray beam or X-ray beam. The radiation source may be incorporated into the particle accelerator  16  or connected to it in any convenient conventional manner. 
     The particle accelerator  16  has an output device, typically comprising a nozzle  24 , for delivering the radiation beam to the radiation target, i.e. a patient  26  (see  FIGS. 6 and 7 ). The nozzle  24  may be configured to bend, scan, focus or otherwise manipulate the radiation beam at the point of delivery, and to this end may include one or more bending, scanning and/or focusing magnets (and/or other beam forming and/or beam manipulating and/or energy selection components as required) for energy selection, bending, scanning and/or focusing the radiation beam at the point of delivery as required. Optionally, the nozzle  24  may be extendible in its longitudinal direction. The nozzle  24  may comprise any conventional radiation therapy beam delivery nozzle. Typically, the nozzle  24  is fixed with respect to the particle accelerator  16  so that it moves with the particle accelerator  16 . In preferred embodiments there is no beam transport system between the particle accelerator  16  and the nozzle  24 , in particular no beam transport system that bends the radiation beam between the particle accelerator  16  and the nozzle  24 . This may be achieved by aligning the nozzle  24  with the particle beam produced by the accelerator  16 . This arrangement simplifies the beam delivery system  12 , reducing cost and increasing reliability. It will be seen that in preferred embodiments, positioning the particle beam with respect to the patient  26  involves moving the whole accelerator  16 , and therefore the nozzle  24 . 
     The system  10  includes a treatment structure, or treatment pod  20 , that is shaped and dimensioned to define an internal treatment room  22  for receiving the patient  26 . The term pod is intended to embrace any structure, typically comprising an enclosure or chamber, that is shaped and dimensioned, and/or otherwise configured, to define an internal treatment room  22  for receiving the patient. The treatment pod  20  comprises a hollow body structure  28  that defines the treatment room  22 . The preferred body structure  28  comprises a solid sleeve-like wall extending around a longitudinal (or end-to-end) axis of the pod  20  and enclosing the treatment room around the longitudinal axis. Alternatively, the body structure  28  may be open or partially open, e.g. being cage-like or comprising an open or partially open frame. The longitudinal, or end-to-end, axis of the pod  20  typically corresponds with the longitudinal, or end-to-end axis of the room  22 . At least one longitudinal end  29 A,  29 B of the body structure  28  is open to provide access to the treatment room  22  for a patient, medial worker and/or equipment as required. The, or each, end  29 A,  29 B may be completely open, or open in that a doorway is defined, as desired. The, or each, end  29 A,  29 B may optionally include one or more closable doors for allowing or preventing access to the room  22  via the respective end  29 A,  29 B. Accordingly, one or both ends  29 A,  29 B of the pod  20  may service as an entrance to and exit from the room  22 . In the illustrated embodiment, both ends  29 A,  29 B are open. Alternatively, one end  29 A,  29 B may be closed by a wall or other solid structure. The body structure  28 , or at least part of it, may be substantially cylindrical in shape, but may alternatively take any other desired shape. The body structure  28  may be formed from any suitable material, for example metal, plastics or a composite material. Optionally, the body structure  28  is formed form, or is cladded with, radiation shielding material. 
     The beam delivery system  12  is carried by the treatment pod  20  and arranged to deliver the radiation beam to the treatment room  22 , and in particular towards a treatment location in the room  22 . In particular, the nozzle  24  (at least its delivery end) is located within the treatment room  22 , and is arranged to direct the particle beam into the treatment room  22 , in particular towards the treatment location in the room  22 . In use, a patient support apparatus is located at the treatment location and a patient supported thereby is targeted by the nozzle  24  in order to receive particle beam therapy. The nozzle  24  is preferably arranged to deliver the radiation beam radially into the room  22 , i.e. towards a centrally located point or axis, e.g. the central longitudinal, or end-to-end, axis of the room  22  or pod  20 . Advantageously, the particle accelerator  16  is located externally of the treatment pod  20 . In preferred embodiments, the beam delivery system  12  is mounted on, or otherwise coupled to, the body structure  28 , preferably with the particle accelerator  16  located outside of the body structure  28  and the nozzle  24  extending through the body structure  28  such that its delivery end is located in the treatment room  22 . Alternatively, the pod  20  may include a support structure (not illustrated), which may be separate from the body structure  28 , for supporting the beam delivery system  12 , and in particular for supporting the particle accelerator  16  externally of the body structure  28 . In any event, the beam delivery system  12 , including the particle accelerator  16  is carried by the pod  20 . 
     Advantageously, the beam delivery system  12 , including the particle accelerator  16 , is movable with respect to the pod  20 , and in particular with respect to the treatment room  22 . This enables the position, preferably the orientation, of the radiation beam to be adjusted with respect to the treatment room  22 , and in particular the treatment location. The preferred arrangement is such that the beam delivery system  12  is moveable, at least partly and optionally fully, around the pod  20  and around the treatment room  22 , preferably in an orbital manner, and in particular around the treatment location in the treatment room. In preferred embodiments, the particle accelerator  16  is correspondingly movable around the outside of the treatment room  22 . The nozzle  24  is movable correspondingly around the inside of the treatment room  22 . The preferred arrangement is such that the nozzle  24  (and in particular its delivery end) is movable around the treatment location within the treatment room  22 , preferably along an arc-like or circular path. The beam delivery system  12  may be coupled to the pod  20 , preferably to the body structure  28 , by any conventional coupling mechanism(s) that allow the desired movement of the beam delivery system  12  with respect to the pod. In the illustrated embodiment, the beam delivery system  12  is moveable in a single plane around the pod  20 , but in alternative embodiments may be rotatable around the pod  20  in more than one plane. 
     In preferred embodiments, the beam delivery system  12  is rotatable about an axis of the pod  20 . The axis is spaced apart from the beam delivery system  12 , and in particular the particle accelerator  16 , such that the rotation is of an orbital nature. Preferably, the rotation axis is the longitudinal axis or other end-to-end axis, of the pod  20  or treatment room  22 , preferably the central longitudinal or end-to-end axis. Preferably, the beam delivery system  12  is rotatable through 360° around the axis. However, the beam delivery system  12  may be rotatable by any amount up to 360° around the axis depending on the requirements of the application. Correspondingly, the nozzle  24  may target the patient from any direction through up to 360° around the axis. In preferred embodiments the arrangement is such that, as the beam delivery system  12  rotates, the particle accelerator  16  revolves around the outside of the pod  20  while the nozzle  24  correspondingly revolves around the inside of the pod  20  in the treatment room  22 . 
     In preferred embodiments, the beam delivery system  12  is coupled to an annular section  28 C of the body structure  28  that is rotatable about the longitudinal axis of the pod  12 . The beam delivery system  12  may be mounted on the rotatable section  28 C so that it rotates with the rotatable section  28 C. The rotatable section  28 C may be located between, and rotatable with respect to, first and second non-rotatable end sections  28 A,  28 B of the body structure  28 . The rotatable section  28 C may be coupled to each end section  28 A,  28 B by any conventional rotatable coupling mechanism  27 , which may for example comprise a slewing bearing. In preferred embodiments, the particle accelerator  16  is mounted on the outside of the rotatable body section  28 C, and the nozzle  24  extends through the rotatable body section  28 C such that its beam delivery end is located inside the body section  28 C. 
     The beam delivery system  12  may be mounted on the rotatable body section  28 C by any conventional mounting means. In the illustrated embodiment, the particle accelerator  16  is mounted on the external surface of the body section  28 C by one or more supports  25 A,  25 B. The particle accelerator  16  may be fixed with respect to the body section  28 C. Alternatively, the particle accelerator  16  may be rotatable with respect to the body section  28 C about a central axis of the accelerator  16  that runs parallel with the longitudinal axis of the pod  20 . For example, the accelerator  16  may be fixedly or rotatably mounted between supports  25 A,  26 B as desired. 
     In alternative embodiments (not illustrated), the whole body structure  28  may be rotatable as described above in respect of the body section  28 C, in which case the beam delivery system  12  may be coupled to the body structure  28  for rotation with the body structure  28  as described above with respect to the body section  28 C. In such embodiments, the pod  20  may include a support structure for the body structure  28 , the body structure  28  being rotatably coupled to the support structure by any conventional rotating coupling mechanism(s) to allow rotation about the longitudinal axis of the pod  20 . Alternatively still, the body structure  28  may be static and the beam delivery system  12  may move around the body structure  28 , and therefore around the treatment room  22 . In such embodiments, the pod  20  may include a support structure for the beam delivery system  12 , the beam delivery system  12  being movably coupled to the support structure by any conventional coupling mechanism(s) to allow movement of the beam delivery system  12  around the body structure  28  and therefore around the treatment room  22 . 
     In preferred embodiments, the pod  20  includes a floor structure  30  within the body structure  28 , providing a floor for the treatment room  22 . The floor structure  30  is fixed with respect to the pod  20  such that as the beam delivery system  12  moves, it moves with respect to the floor structure  30 , and therefore with respect to the treatment room  22 . The floor structure  30  may be supported by the end sections  28 A,  28 B of the body structure  28 , or by any other convenient support structure. Depending on the embodiment, all or part  28 C of the body section may rotate with respect to the floor structure  30 . 
     In preferred embodiments, the movement of the beam delivery system  12  around the pod  20  is counterbalanced. The preferred treatment pod  20  includes a counterbalance  32  arranged to counterbalance the beam delivery system  12  with respect to the longitudinal axis of the pod  20 , or other axis about which it is rotatable or pivotable. In preferred embodiments, the counterbalance  32  counterbalances the rotational movement of the beam delivery system  12  around the pod  32 , in particular about the longitudinal axis of the pod  20 . The mass and location of the counterbalance  32  is such that it provides a counterbalancing moment to that imparted the beam delivery system  12  with respect to the rotational axis, which is conveniently the longitudinal axis of the pod  12 . This facilitates rotation of the beam delivery system  12  in that less driving force is required to rotate the beam delivery system  12  than would be required if there was no counterbalance. It is noted that an exact counterbalancing moment is preferred, but the counterbalance  32  does not need to exactly counterbalance the beam delivery system  12 . 
     In preferred embodiments, the counterbalance  32  is rotatable about the longitudinal axis of the pod together with the beam delivery system  12 , and is preferably located opposite to the beam delivery system  12  with respect to the longitudinal axis of the pod  20 . As such the beam delivery system  12  and counterbalance  32  may be radially spaced-apart around the longitudinal axis of the pod  20  by 180°, or approximately 180°. In preferred embodiments, the counterbalance  32  is mounted on, or otherwise coupled to, the body structure  28 , and is preferably located outside of the body structure  28 . In preferred embodiments, the counterbalance  32  is mounted on the rotatable section  28 C so that it rotates with the rotatable section  28 C. In the illustrated embodiment, the counterbalance  32  is mounted on the external surface of the body section  28 C by one or more supports  31 A,  31 B. In typical embodiments, substantially all of the weight of the beam delivery system  12  is provided by the particle accelerator  16  and so it may be said that the counterbalance  32  counterbalances the particle accelerator  16 . Typically, the counterbalance  32  is located externally of the pod  20 , opposite the particle accelerator  16  with respect to the longitudinal axis of the pod  20 . 
     The counterbalance  32  may comprise any convenient object or objects with a suitable mass. Optionally, the counterbalance  32  may comprise a second beam delivery system (not illustrated), which may be the same as or similar to the beam delivery system  12 , and may be coupled to the treatment pod  20  in the same or a similar manner. In particular, the counterbalance  32  may comprise the particle accelerator of a second beam delivery system. The particle accelerator of the second beam delivery system may be of the same type as the particle accelerator  16  of the first beam delivery system  12 , or may be of a different type, i.e. capable of providing the same type or a different type of therapy. Providing a second beam delivery system allows a patient in the treatment room  22  to be treated by either or both beam delivery systems, simultaneously or in turn as desired, as well as allowing the patient to be subjected to two different types of therapy in the same session. The first and second beam delivery systems are radially spaced apart around the longitudinal axis of the pod  20 , preferably by 180°, or approximately 180°. This spacing allows the patient to be treated from corresponding different directions by the respective nozzles  24 . Also, the spacing allows one or other of the nozzles  24  to target the patient from any direction through 360° around the longitudinal axis without either of the beam delivery systems having to be rotated through more than 180°. Optionally, therefore, the rotation of the beam delivery systems about the longitudinal axis may be restricted to 180°, or approximately 180°. 
     More generally, in alternative embodiments (not illustrated), two or more beam delivery systems may be coupled to the treatment pod  20 , radially spaced apart around the longitudinal axis of the pod  20 . The beam delivery systems are preferably provided with a respective counterbalance, optionally as one or more counterbalancing pair of beam delivery systems, as described above. Each beam delivery system may be the same as or similar to the beam delivery system  12 , and may be coupled to the treatment pod  20  in the same or a similar manner as described above. 
     In preferred embodiments, the treatment pod  20  includes at least one drive mechanism for moving the beam delivery system  12  around the pod  20 , which typically involves rotating the beam delivery system  12  about the longitudinal axis of the pod  20 . The drive mechanism(s) may take any suitable conventional form. In the illustrated embodiment, a drive mechanism  34  is coupled between the rotatable body section  28 C and one of the end sections  28 B, and is arranged to rotate the body section  28 C with respect to the end section  28 B. In this example, the drive mechanism  34  comprises a motor  34 A mounted on the rotatable body section  28 C, and a rotatable driving head  34 B coupled to the end section  28 A, whereby rotation of the driving head  34 B causes rotation of the rotatable body section  28 C with respect to the end section  28 B. 
     In preferred embodiments, the radiation therapy system  10  includes a bay structure  60 , or other housing structure, typically a building structure, for housing the treatment pod  20 . Preferably, the treatment pod  20  is supported, by any convenient conventional support means, above the floor  61  of the bay  60  to provide sufficient space below the treatment pod  20  to accommodate the particle accelerator  16  and/or the counterbalance  32  as the beam delivery system  12  rotates. 
     The preferred radiation therapy system  10  includes a plurality of waiting rooms  14 . The preferred arrangement of the system  10  is such that a patient  26  ( FIGS. 6 and 7 ) can be transferred directly from any one of the waiting rooms  14  into the treatment room  22 . Each waiting room  14  has a doorway  17 , and optionally a door  19  for opening and closing the doorway  17 . In embodiments where the waiting room  14  has a door  19 , the or each open end  29 A,  29 B of the pod  20  does not require a door, although may have a door (not illustrated) if desired. In embodiments where the or each end  29 A,  29 B of the pod  20  has a door, the doorway  17  of each waiting room  14  does not require a door, although may have a door  19  if desired. The door  19  and/or the door provided on the pod  20  (when present) may comprise radiation shielding. 
     In preferred embodiments, the treatment pod  20  is open to provide user access from each end  29 A,  29 B, and the waiting rooms  14  are arranged in one or more oppositely disposed pairs  14 A,  14 B. The waiting rooms  14 A,  14 B of the, or each, pair are spaced apart with their respective doorway  17  facing each other, and preferably in register with one another. The spacing between the opposing waiting rooms  14 A,  14 B is sufficient to allow the treatment pod  20  to be located between the opposing rooms  14 A,  14 B, with one end  29 A facing one of the waiting rooms  14 A and the other end  14 B facing the other waiting room  14 B. When the treatment pod  20  is located between the opposing waiting rooms  14 A,  14 B, the open end  29 A is aligned with the doorway  17  of waiting room  14 A, and the open end  29 B is aligned with the doorway  17  of waiting room  14 B. The preferred arrangement (e.g. the relative length of the pod  20  and the gap between the waiting rooms  14 A,  14 B) is such that the respective pod opening and waiting room doorway  17  are adjacent one another such that there is direct access between the respective waiting room  14 A,  14 B and the treatment room  22  via the respective pod end  29 A,  29 B. 
     In one embodiment, the system  10  has a single pair of waiting rooms  14 A,  14 B and the treatment pod  20  is statically installed between them in the manner described above. 
     In preferred embodiments, the treatment pod  20  is movable with respect to the treatment rooms  14 , so that it may be aligned with one or two treatment rooms  14  at a time, depending on the configuration of the system  10 . In preferred embodiments, and as illustrated in the embodiment of  FIGS. 1 to 5 , the treatment pod  20  is movable so that it may be aligned with any one pair of a plurality of pairs of opposing treatment rooms  14 A,  14 B. When aligned with a pair of treatment rooms  14 A,  14 B, the pod  20  is located between them as described above to allow access to the treatment room  22  from either of the waiting rooms  14 A,  14 B with which it is aligned. 
     In the illustrated embodiment, three pairs of opposing waiting rooms  14 A,  14 B are shown, although in alternative embodiments there may be more or fewer pairs of opposing waiting rooms  14 A,  14 B. The pairs of opposing waiting rooms  14 A,  14 B are preferably arranged in a linear array to define a common linear passage  63  running between all of pairs of opposing waiting rooms  14 A,  14 B. The pod  20  is located in the linear passage  63  and is movable along the linear passage  63  so that it may align with any one of the opposing pairs of waiting rooms  14 A,  14 B. In preferred embodiments, the bay  60  is shaped and dimensioned to provide the linear passage  63 , with opposing waiting rooms  14 A,  14 B being located along opposite sides of the passage  63 . In an alternative embodiment (not illustrated), a plurality of waiting rooms  14  may be provided along one side of the passage  63  only, the pod  20  being movable along the passage  63  to align with only one waiting room  14  at a time, in which case the pod  20  may be closed at its other end. Alternatively still, one or more waiting rooms  14  may be provided on each side of the passage  63 , but not necessarily arranged in opposing pairs, in which case the pod  20  is only able to align with one waiting room  14  at a time. 
     The passage  63  need not necessarily be linear. In alternative embodiments, the bay  60  may be shaped to define a circular, semi-circular passage or otherwise curved or curvilinear passage (not illustrated). In any case, one or more waiting rooms  14  may be provided along either one or both sides of the passage  63 , and the pod  20  is movable along the passage  63  to align with one or two waiting rooms at a time. In cases where waiting rooms  14  are provided on both sides of the passage  63 , it is preferred that they are arranged in opposing pairs so that the pod  20  can align with two waiting rooms simultaneously. 
     The treatment pod  20  may be movable along the passage  63  by any conventional conveyancing means. In typical embodiments, conveyancing means comprises a carriage  64  on which the treatment pod  20  is mounted. The carriage  64  may be of any conventional type, for example comprising wheels, rollers, runners or tracks, as is convenient. The bay  60  may include one or more tracks  66  along which the carriage  64  may run. In the illustrated embodiment, a respective track  66 A,  66 B runs along each side of the passage  63 . The carriage  64  may comprises first and second parts  64 A,  64 B, one for each of the tracks  66 A,  66 B. The tracks  66 A,  66 B are preferably located above the floor level of the bay  60  such that the carriage  64  supports the pod  20  above the floor level of the bay  60 . Hence, the conveyancing means can conveniently provide the support means for supporting the treatment pod  20  above the floor  61  of the bay  60  to provide sufficient space below the treatment pod  20  to accommodate the particle accelerator  16  and/or the counterbalance  32  as the beam delivery system  12  rotates. One or more drive mechanisms  68  may be provided for moving the carriage  64  along the passage  63 . The drive mechanisms  68  may be of any suitable conventional type. 
     In alternative embodiments (not illustrated), any other suitable conveyancing means may be used to move the treatment pod  20  with respect to the waiting rooms  14 . For example, the conveyancing means may comprise a movable gantry, or a gantry crane, or a jib, or an arrangement of linear actuators, e.g. hydraulic actuators. 
     In alternative embodiments (not illustrated), the bay  60  need not necessarily define a passage for the pod  20  to move along. For example, the bay  60  may comprise a room around which the pod  20  is movable by any suitable conveyancing means. A plurality of waiting rooms  14  may be arranged around the outside of the bay room, the pod  20  being movable around the bay room so that it aligns with any one of the waiting rooms  14  at a time. The room may be circular, or at least have an arc-shaped wall, so that the waiting rooms  14  are arranged in a circle or arc around the bay room. The pod  20  may be carried by a rotatable support that is configured to move the pod  20  from waiting room to waiting room. For example, one end of the pod  20  may be coupled to the support in a cantilevered or jib manner, so that rotation of the support moves the other end of the pod in an arc, or circle, from room to room. 
     In the illustrated embodiment, the waiting rooms  14  are provided in a single level or storey. In alternative embodiments (not illustrated), the waiting rooms  14  may be provided in a multi-storey structure. Accordingly, the treatment pod  20  may be carried by a lift device for raising and lowering the pod  20  between storeys. Any conventional lift device may be used for this purpose. The arrangement of the bay and waiting rooms of each storey may be the same or similar to any of the arrangements described above. 
     The waiting rooms  14  and bay  60  are typically provided in a building structure, such as a hospital or clinic. 
     Referring now in particular to  FIGS. 6 and 7 , the inside of a typical waiting room  14  is shown. It will be understood that specific equipment and furnishings are shown by way of example only. The waiting room  14  aligned with the treatment pod  20  and the door  19  is open to allow access between the waiting room  14  and the treatment room  22 . 
     At least one patient support apparatus  38  is provided, preferably at least one for each waiting room  14 . The patient support apparatus  38  may take any conventional form, typically comprising a chair, couch, platform or bed, for accommodating the patient  26 . The preferred support apparatus  38  provides at least one of, and may be operable between any two or more of, the following configurations: a standing configuration (in which it supports the patent in a standing position), a sitting configuration (in which it supports the patient in a sitting position), a fully reclined configuration (in which it supports the patient in a fully reclined position), and one or more semi-reclined configurations. In the illustrated embodiment, the patient support apparatus  38  comprises a platform on which the patient  26  can lie flat. In  FIG. 6 , the platform  38  is shown supported on a trolley  39 . 
     The preferred system  10  includes at least one actuation apparatus  40  for moving the patient support apparatus  38  between the waiting room  14  and the treatment room  22  (as illustrated in  FIG. 7 ). The actuation apparatus  40  is preferably operable to move the patient support apparatus  38  to a treatment location in the treatment room  22  where the nozzle  24  of the, or each, beam delivery system  12  can direct its beam onto the patient  26 . 
     In the illustrated embodiment, the actuation apparatus  40  is provided in the treatment room  22  and is operable to extend out of the treatment room  22  into the waiting room  14  to fetch the patient support apparatus  38 . Alternatively, the patient support apparatus  38  may be integrally formed with the actuation apparatus  40  and the actuation apparatus may be operable to extend out of the treatment room  22  into the waiting room  14  to fetch the patient  26 . These arrangements allow the door(s) between the treatment room  22  and waiting room  14  to be closed during therapy. In preferred embodiments where the pod  20  may be accessed from both ends  29 A,  29 B, a respective actuation apparatus  40  (with or without an integral patient support apparatus) may be provided for each end  29 A,  29 B, as illustrated in  FIGS. 6 and 7 . Alternatively, the actuation apparatus  40  may be provided in the waiting room  14  and be operable to extend into the treatment room  22 . In alternative embodiments, the actuation apparatus may be omitted and the patient support apparatus  38  may be installed in the treatment room  22 , preferably at the treatment location. 
     The actuation apparatus  40  may be configured in any conventional manner in order to achieve the desired movability of the patient support apparatus  38 . By way of example, in the illustrated embodiment the actuation apparatus  40  comprises an articulated arm  44 . Typically, the actuation apparatus  40  is power operated, e.g. by one or more power operated actuators (not shown), which may for example be electrically or hydraulically operated as is convenient, and may be linear or rotary as required. 
     When in the treatment location, it is preferred that the patient support apparatus  38  is adjustable to adjust the position of the patient  38  with respect to the nozzle(s)  24 . In preferred embodiments, the patient support apparatus is operable to move the patient  26  linearly along any one or more of the three orthogonal Cartesian axes, and/or to rotate the patient  26  about any one or more of the three orthogonal Cartesian axes. The supported movements may be effected by the patient support apparatus  38  self, and/or by the actuation apparatus  40  as is convenient. In addition, the nozzle(s)  24  is movable with respect to the treatment location, and therefore the patient  26 , by rotating the beam delivery system  12  as described above, and/or by adjustment of the nozzle  24 . This facilitates a wide range of relative angles and positions of the delivered radiation beam relative to the patient support apparatus when in the treatment location. In preferred embodiments, the adjustability of the patient support apparatus  38  and/or of the beam delivery system  12  individually or together allow the radiation beam to be delivered in a precise and highly adjustable manner (advantageously in up to 6 cartesian dimensions (x,y,z,θ,ϕ, ψ)) to a target zone in the treatment location. In particular it is preferred the radiation beam may be targeted at the target zone 3 dimensionally. Advantageously, the adjustability of the beam delivery system  12  is configured to provide isocentric delivery of the radiation beam to the target zone (which target zone coincides in use with a patient on the relevant patient support apparatus  38 ). Advantageously, during use the relative positions and angles of the system  10  may be adjusted to achieve isocentric irradiation of the target zone. Advantageously, the system  10  allows substantially full 3-D Isocentric irradiation of a patient, suitable for intensity modulated therapy or spot scanning. Scanning of the radiation beam about at least one and preferably two perpendicular axes (e.g. a vertical axis and a perpendicular horizontal axis running transversely of the room) may be supported, conveniently by incorporation of scanning magnets in the nozzle  24 . 
     Systems  10  embodying the invention typically include a control system (not shown), which may be located in a separate room. The control system may include equipment for controlling and monitoring any aspect of the system  10  and may take any suitable conventional form, typically including suitable programmed computing device(s). The control system typically includes means for controlling and/or monitoring the operation of any one or more of the beam delivery system  12  (including its rotation and its beam delivery), pod conveyancing means, the actuation apparatus  40 , the patient support apparatus  38  and the doors  19  as applicable. The control system may include components (e.g. scanner(s), visual display unit(s) and user interface device(s)) of an imaging system for controlling and/or monitoring operation of the system  10 . The imaging system may comprise any one or more of an MRI system, PET system, SPECT system or CT system. The control system may be configured to control any one or more components of the system  10  collectively or individually. 
     During use, the control system may obtain treatment information in respect of the waiting room  14  to be serviced. The treatment information typically includes beam delivery vector(s) for targeting the beam on a target zone, and dosage information. The control system causes the pod  20  to align with the respective waiting room, and positions the particle accelerator  16 , including the nozzle  24 , in a desired position and/or orientation as determined from the treatment information, i.e. in order to deliver the radiation beam at the required delivery vector(s). 3D targeting of the radiation beam may be performed by a laser so that the radiation beam always impinges on the target zone as desired. 
     In preferred embodiments, the control system includes one or more devices (e.g. cameras and/or motion sensors and/or pressure sensors) for detecting movement of the patient when on the patient support apparatus  38 . The control system may be configured to use any detected movement of the patient to re-position one or more component of the system  10 , in particular of the beam delivery system  12 , to ensure that the radiation beam is correctly targeted on the patient, i.e. the delivery of the beam automatically tracks any detected movement of the patient during use. Optionally, if any detected movement exceeds a threshold level, then the control system may be configured to cease treatment. 
     The provision of a counterbalanced beam delivery system  12  is advantageous in that it allows the particle accelerator  16  to be easily moved in the manner described, which would be beyond the capability of conventional robots since particle accelerators can weigh between 100-200 tonnes and so are conventionally deployed statically. 
     Providing the nozzle  24  at the particle accelerator  16  without an intermediate beam transport system is advantageous since it avoids or reduces beam degradation and collateral residual radiation that can be caused by bending magnets and other components of a beam transport system. Moreover, as there is no long beam line or 2D gantry, the maintenance, energy requirements, size, scale and costs of the system are reduced in comparison with conventional systems. 
     Providing one or more beam delivery system  12  on a pod  20  that can service multiple waiting rooms  14  allows efficient use of the treatment room  22 , particularly since multiple patients can be prepared for therapy simultaneously and wait for the treatment room  22  to become available. 
       FIGS. 8 to 10  illustrate another radiation therapy system  110  embodying the invention. The radiation therapy system  110  is similar to the radiation therapy system  10 , like numerals being used to denote like parts and the same or similar description applying as would be apparent to a skilled person.  FIGS. 8 to 10  illustrated a preferred radiation shielding configuration for the radiation therapy systems embodying the invention. The system  110  includes a radiation shielding structure  170  that surrounds, or at least partly surrounds, the treatment pod  20  and the beam delivery system  12 , and is shaped and dimensioned accordingly. The preferred radiation shielding structure  170  has a top shield section  172  located so as to provide radiation shielding above the treatment pod  20  and beam delivery system  12 ; first and second side shield sections  174 ,  176  located so as to provide radiation shielding at opposite sides, respectively, of the treatment pod  20  and the beam delivery system  12 , and first and second end shield sections  178 ,  180 , located so as to provide radiation shielding at opposite ends, respectively, of the treatment pod  20  and the beam delivery system  12 . 
     The radiation shielding structure  170  may be box-like in shape, e.g. may be substantially rectangular in transverse and longitudinal cross-section. The preferred configuration is such that the radiation shielding structure  170  encloses the treatment pod  20  and the beam delivery system  12  at least from above, at opposite sides and at opposite ends. In the illustrated embodiment, the shield structure  170  is open at its bottom, i.e. below the treatment pod  20  and the beam delivery system  12 . 
     Alternatively, the radiation shield structure  170  may include a bottom section located to provide radiation shielding below the treatment pod  20  and the beam delivery system  12 . 
     In preferred embodiments in which the assembly of the treatment pod  20  and the beam delivery system  12  are movable, the radiation shielding structure  170  moves with the assembly. The conveyancing means  64  may be embedded within the structure  170 , or encased by it, or located outside of it as is convenient. 
     In preferred embodiments, the radiation shielding structure  170  comprises a doorway  182 A,  182 B aligned with each doorway of the treatment pod (i.e. the doorways at ends  29 A,  29 B in the illustrated embodiment) with a respective door  184 A,  184 B. The doors  184 A,  184 B are formed at least partly from radiation shielding material such that they serve as part of the radiation shielding structure  170 . For example, the doorways  182 A,  182 B and doors  184 A,  184 B may be incorporated in to a respective end section  178 ,  180  of the shielding structure  170 . Conveniently, the doors  184 A,  184 B serve as doors to the pod structure  20  and so additional doors at the ends  29 A,  29 B are not required. 
     The radiation shielding structure  170  may be formed from any suitable conventional radiation shielding material, e.g. polyethylene, borated polyethylene, concrete and water. 
     The radiation shielding structure  170  is advantageous in that it obviates the need to provide radiation shielding throughout the bay structure  60  or other structure that surrounds the assembly, and means that the each waiting room  14  does not need to have its own radiation shielding door. 
     Although embodiments of the invention are described herein in the context of a radiation therapy system having a beam delivery system comprising a particle accelerator for generating a radiation beam, the invention may alternatively be used with other beam delivery systems that do not include a particle accelerator, instead comprising means for generating other types of beam, e.g. an ultrasound beam. Alternatively, the beam delivery system may be replaced by an alternative patient treatment system or patient scanning system, e.g. MRI scanning equipment or CT scanning equipment. 
     The invention is not limited to the embodiment(s) described herein but can be amended or modified without departing from the scope of the present invention.