Abstract:
The invention relates to a treatment room for a particle therapy system that has a treatment room isocenter, which can be set variably during treatment and forms an origin of a coordinate system, and a patient positioning apparatus for automatically positioning the patient with reference to the set treatment room isocenter.

Description:
[0001]    The present patent document is a nationalization of PCT/EP2006/068308, filed Nov. 9, 2006, designating the United States, which is hereby incorporated by reference. This application also claims the benefit of EP 05024743.6, filed Nov. 11, 2005, which is hereby incorporated by reference. 
       BACKGROUND 
       [0002]    The present embodiments relate to a particle therapy system for irradiating a volume of a patient that is to be irradiated with high energy particles. The present embodiments may also relate to the planning and carrying out of irradiation in a treatment room of a particle therapy system. 
         [0003]    A particle therapy system has at least one treatment room with a beam exit from which a particle beam emerges in order to interact with the patient positioned in an irradiation position. Usually, the irradiation position is given with reference to an irradiation isocenter of the particle therapy system. Furthermore, the particle therapy system usually has an imaging apparatus for verifying the position of the target volume with reference to the particle beam, and a patient positioning apparatus with which, for the purpose of irradiation, the patient can be brought into the irradiation position. 
         [0004]    Various irradiation systems and techniques are known from H. Blattmann in “Beam delivery systems for charged particles”, Radiat. Environ. Biophys. (1992) 31:219-231. A particle therapy system is disclosed, for example, in EP 0 986 070. 
         [0005]    A particle therapy system usually has an accelerating unit and a high energy beam guiding system. Acceleration of the particles, for example, protons, pions, helium, carbon or oxygen ions, is performed, for example, with the a synchrotron or cyclotron. 
         [0006]    The high energy beam transport system guides the particles from the accelerating unit to one or more treatment rooms. A distinction is made between fixed beam treatment rooms, in which the particles strike the treatment site from a fixed direction, and gantry-based treatment rooms. In the case of the latter, it is possible to direct the particle beam on to the patient from various directions. 
         [0007]    A control and safety system of the particle therapy system ensures that a particle beam characterized by the requested parameters is guided into the appropriate treatment room. The parameters are defined in a treatment or therapy plan. The treatment or therapy plan specifies how many particles are to strike the patient from which direction and with which energy. 
         [0008]    The therapy plan is usually generated with imaging methods. For example, a 3D data record is generated using a computed tomography unit. The tumor is localized inside this image data record, and the required radiation doses, directions of incidence, and types of particle are fixed. 
         [0009]    During the irradiation, the patient is positioned in the irradiation position on which the therapy planning is based. This is performed, for example, using fixing masks. In addition, before the irradiation the patient&#39;s position is checked using an imaging device. In this case, the current irradiation position is matched to the image data record on which the therapy planning is based. 
         [0010]    During this so called position verification, images from various directions are matched with, for example, projections from the CT planning data record before an irradiation. Fluoroscopic images are obtained for this purpose in the beam direction and orthogonal thereto. The recordings of these images are carried out in the irradiation position near the beam exit. Only limited space is available for imaging. 
         [0011]    In general, there are imaging methods for obtaining 3D image data records which are based on the fact that fluoroscopies are carried out from various directions. 3D-type image data records can be obtained from the image data in a fashion similar to a CT picture. One possibility for such an imaging apparatus is an imaging robot that can be aligned freely about a patient to be X-rayed. X-raying the patient from various directions requires availability of appropriately sufficient space. Another possibility for obtaining 3D pictures is, for example, a C-arm X-ray machine. 
         [0012]    Such imaging devices for obtaining 3D image data records require sufficient space to be able to X-ray the patient from various directions. It must be possible to move elements of the imaging unit about the patient in order to take images at an adequate spacing. 
         [0013]    In general, the patient is positioned close enough to the beam exit to keep the expansion of the beam through scattering as slight as possible. A customary spacing between the isocenter of an irradiation site and the beam exit is approximately 60 cm. 
         [0014]    The preferred spacing, addressed above, of the irradiation isocenter from the beam exit constrains the imaging of the position verification to imaging apparatuses that occupy correspondingly little space. 
       SUMMARY AND DESCRIPTION 
       [0015]    The present embodiments may obviate one or more of the drawbacks or limitations inherent in the related art. For example, in one embodiment, an irradiation of a patient is planned and carried out, such that the performance of a high precision therapy system that can be flexibly used, is exploited. In another example, in one embodiment, particle therapy has various types of particles by a scanning technique and with a highly accurate position verification. A particle therapy system t includes imaging techniques that take up space to be used in verifying position. 
         [0016]    In one embodiment of the treatment room, the treatment room has a treatment room isocenter that can be set variably during treatment and forms an origin of a coordinate system, and a patient positioning apparatus for automatically positioning the patient with reference to the set treatment room isocenter. The treatment room isocenter for irradiation, such as the irradiation isocenter, can be set variably. 
         [0017]    The treatment room isocenter is the origin of a coordinate system in the treatment room. Positionings, for example, of the patient support apparatus, of the patient, of an imaging unit and/or of a particle beam path are defined in the treatment room with reference to the isocenter. The isocenter&#39;s position along the particle beam path defines the beam parameters present in the irradiation, such as beam diameter and beam profile, in particular the steepness of the drop in the beam profile. 
         [0018]    If the treatment room isocenter can be set, the treatment room isocenter is no longer fixed to a point in the treatment room, but that it can be selected and set freely, for example, in a fashion limited to one region. The treatment room isocenter can be identified in space by an appropriately alignable laser cross. In addition or as an alternative, the treatment room isocenter or its position or coordination in the treatment room may be stored as stored information in, for example, a therapy control center, and to make use of it in controlling an irradiation procedure. The stored information is transmitted, for example, to the positioning apparatus and/or used as a basis for driving the positioning apparatus when a therapy plan isocenter is to be set with reference to the treatment room isocenter. Furthermore, the stored information can be transmitted to an imaging unit and/or be used as a basis for driving the imaging unit when, for example, imaging is to be carried out in a fashion centered around the treatment room isocenter. 
         [0019]    The beam parameters, such as beam diameter and beam profile, in particular, the steepness of the drop in the beam profile, are a function of the type of particle and the position of the treatment room isocenter in the beam path. The treatment room isocenter can be set in an appropriately flexible fashion. 
         [0020]    An optimum spacing of the treatment room isocenter from a beam exit can be set in the treatment room for each irradiation procedure, for example, for each type of particle and for each irradiation direction. Together with an appropriately settable small beam diameter, such a beam then additionally has, for example, a steep radial drop in the particle distribution. A highly accurate and precise irradiation can be optimally repositioned. A raster scanning technique may be used to obtain the highly accurate and precise irradiation. 
         [0021]    Furthermore, given an appropriate selection of the treatment room isocenter 3D imaging can also be carried out with an imaging apparatus that makes corresponding demands on space. A very precise irradiation with a particle beam can thereby be carried out with regard to the verification of position, since the verification of position is performed with 3D data records, or at least data records of 3D type. 
         [0022]    In one embodiment of the treatment room, the settable treatment room isocenter can be set along a beam central axis of the particle beam, for example, for irradiation procedures. The beam central axis is, for example, the beam path given by the zero position of a raster scanning apparatus. 
         [0023]    In one embodiment, the distance between the treatment room isocenter for irradiation and for imaging is equal to or less than 2 m and, if possible, less than 0.5 m, and so the verification of position can also be undertaken repeatedly when possible during an irradiation without great loss of time owing to long travel paths. Maintaining the distance is possible, for example, whenever the movement path of the patient is kept as small as possible, that is to say when, for example, the imaging device has, or virtually has the minimum spacing from the beam exit. 
         [0024]    In one embodiment, a patient positioning system (apparatus) includes a robotically driven patient table. The patient positioning system (apparatus) is preferably driven by a therapy control unit of the particle therapy system. The parameters for carrying out a change in position can be stored in the therapy plan that forms the basis of the therapy control unit for controlling the irradiation. 
         [0025]    In one embodiment, a therapy plan includes at least two procedures for irradiating and/or imaging with identical and/or different therapy plan isocenters, the procedures being assigned at least two spatially different treatment room isocenters. A therapy plan isocenter is a point (volume element) in an image data record of the patient to be irradiated which forms the basis of planning. With reference to this point, an irradiation procedure, for example, is planned. Geometric information for the irradiation, such as irradiation direction or a volume to be irradiated/imaged, is referred to this point. A relationship of the therapy plan isocenter to the treatment isocenter as is desired during the carrying out of the procedure is defined. Desired beam parameters that are given by the position of the treatment room isocenter are also taken into account during planning. 
         [0026]    The relationship of the therapy plan isocenter to the treatment room isocenter, for example, laying the two isocenters one upon the other, is then produced during execution, for example, by positioning the patient or the imaging apparatus, and/or setting the treatment room isocenter appropriately. 
         [0027]    A therapy plan is a data record that has been compiled, for example, with a computer unit and in which patient-related data are stored. By way of example, this can include a medical image of the tumor to be treated, and/or selected regions to be irradiated in the body of a patient, and/or risk organs whose radiation burden is to be kept as low as possible, and/or other information. Furthermore, by way of example this includes parameters that characterize the particle beam and that specify how many particles are to strike the patient or specific regions to be irradiated, from which direction and with which energy. The energy of the particles determines the depth of penetration of the particles into the patient, for example, the location of the volume element at which the maximum of the interaction with the tissue occurs during the particle therapy. In other words, the location at which the maximum of the dose is deposited. The therapy control unit can use the therapy plan to determine the control instructions required for controlling the irradiation. The therapy plan takes into account that the treatment room isocenter for the irradiation can be set variably. 
         [0028]    Even when planning the therapy, the therapy freedom can be introduced into an optimized particle therapy via the spatial selection of the treatment room isocenters to be used, that is to say the isocenters spacing from the beam exit, for example. The verification of position can be performed independently, for example, of the position of a treatment room isocenter set for an irradiation, or treatment room isocenters can be selected as a function of the incidence angle and of the sorts of particles used. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is a schematic of an embodiment of a particle therapy system, 
           [0030]      FIG. 2  an exemplary flowchart for illustrating an irradiation procedure in accordance with a therapy plan, and 
           [0031]      FIGS. 3 to 5  show schematics of a treatment room with variably settable treatment room isocenters. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]      FIG. 1  shows a particle therapy system  1  for irradiating a volume, to be irradiated, of a patient with high energy particles. A particle accelerating unit  3  emits a particle beam  7  from a beam exit  5 . The particle therapy system includes, for example, a raster scanning apparatus  9  that scans a scanning region of 20 cm×20 cm. A treatment room isocenter  11  may be set on a beam central axis that runs centrally in relation to the scanning region. The particle beam diverges because of scattering processes in the beam or with the matter being X-rayed. The closer a treatment room isocenter is arranged to the beam exit  5 , the smaller the beam diameter of the particle distribution in the particle beam, and the more sharply defined the lateral drop in the particle distribution. A spacing of 60 cm may be selected in the case of irradiation with protons. At this spacing, the beam diverges to a desired beam diameter adopted in the therapy plan; for example, the irradiation is performed using a raster scanning method with a beam diameter of approximately 5 mm. 
         [0033]    Furthermore, the particle therapy system  1  has an imaging apparatus  13  that may generate a 3D data record of the patient in the region of the volume to be irradiated. The imaging apparatus  13  is intended to be used to verify the position of the volume to be irradiated with reference to the particle beam. The imaging apparatus  13  has an imaging center  15 . As a result of the design, such as the dimensions and structure, of the imaging apparatus  13 , the spacing of the imaging center  15  from the beam exit  5  is greater than the spacing of the treatment room isocenter  11  provided for irradiation from the beam exit  5 . For imaging purposes, a treatment room isocenter, such as the imaging center  15  in  FIG. 1 , is arranged on the beam central axis. The spacing between the treatment room isocenter  11  and the treatment room isocenter for imaging (imaging center  15 ) is kept as small as possible. For example, the spacing of the imaging center  15  from the beam exit  5  is 100 cm. A displacement of 40 cm in or against the beam direction can be carried out quickly and without stressing the patient even during an irradiation session. 
         [0034]      FIG. 2  shows an irradiation session  21  that is carried out on the basis of a therapy plan  23 . In addition to the required beam parameters, the therapy plan  23  has the particle energy, the particle intensity, and direction of incidence, for various volume elements of the volume to be irradiated and for various irradiation procedures from various directions, for example. In addition, the therapy plan  23  includes information relating to the position (X, Y, Z) of the treatment room isocenters for irradiation, and/or the position (X i , Y i , Z i ) of the treatment room isocenters for imaging, and/or possibly a displacement vector  25  that specifies by how much a patient or an imaging apparatus must be displaced so that therapy plan isocenters are matched with treatment room isocenters. 
         [0035]    The irradiation session  21  may begin with a verification of position  27 . Verification may positioning the patient in the imaging position in the treatment room isocenters for imaging (X i , Y i , Z i ), in accordance with the therapy planning. Subsequently, a displacement  29  is carried out in accordance with the displacement vector  25 . The patient is now in the irradiation position. A first irradiation procedure  31  is carried out in this position. 
         [0036]    It however, the suspicion arises during the irradiation that the patient&#39;s position has changed, a second displacement  33  back into the imaging position can now be performed in order to carry out a further verification of position  35 . 
         [0037]    Such verifications of position can occur repeatedly because of suspected changes in position, for safety reasons, or in order to undertake a further irradiation, for example, from another direction of incidence. 
         [0038]    The therapy plan  23  for the irradiation session  21 , which possibly has a number of irradiation and/or imaging procedures, is performed, for example, in a number of acts. In one act, an imaging procedure is planned in which a therapy plan isocenter of the volume to be irradiated lies at the imaging center of the imaging apparatus. In this position (the imaging position), the imaging is to be carried out in order to verify the position of the patient in accordance with the irradiation planning. No beam is planned or applied in this imaging position. 
         [0039]    An irradiation procedure is planned in another act. To this end, one or more treatment room isocenters are fixed, and one or more irradiation fields are planned. The planning of the irradiation procedure includes, for example, that at the beginning of the irradiation procedure the patient is positioned by the patient positioning apparatus such that the irradiation isocenter lies at an isocenter of the radiation location. An irradiation room isocenter is planned such that the patient is brought up as close as possible to the radiation exit without being in danger. For example, the treatment room isocenter is displaced from the imaging center to the position planned for the irradiation. The actual irradiation is then performed in this position (the irradiation position). 
         [0040]    The treatment room isocenter for irradiation can be set variably. 
         [0041]    Further imaging procedures and irradiation procedures, including under changed directions of incidence, depending on circumstances, may be planned. When use is made of a gantry, it is possible here for the different direction of beam incidence to require correspondingly matched treatment room isocenters. 
         [0042]      FIG. 3  shows an example of a treatment room with a beam exit  41 , a patient positioning apparatus  43  and an imaging apparatus  45  with an imaging volume  47 . The patient positioning apparatus  43  has a patient couch (support)  49  on which a patient  51  lies. The volume, to be irradiated, of the patient  51  lies, for example, inside a skull  53  of the patient  51 . The imaging volume  47  has an imaging center  55 . The imaging center  55  may be located on a beam central axis  57  of the particle beam, for example, at a distance of 100 cm from the beam exit  41 . A picture, preferably a 3D picture (representation) of the volume to be irradiated, is recorded with the imaging device (apparatus)  45  for the purpose of verifying position. The treatment room isocenter is set to the position provided in the therapy plan. The settability of the treatment room isocenter enables the imaging apparatus to be planned in the positions required for 3D imaging. 
         [0043]    The 3D picture is matched with pictures on which the therapy planning was based and, the patient  51  may be readjusted with the patient positioning apparatus  43  into the position on which the therapy planning is based. The patient is then located in the imaging position defined in the therapy plan. 
         [0044]    The patient  51  is moved from the imaging position into the irradiation position that is illustrated in  FIG. 4 . The treatment room isocenter is set to the position envisaged in the therapy plan. The volume previously situated around the imaging center  55  and to be irradiated now lies around the irradiation isocenter  61  and can, for example, be irradiated with a (raster) scanning apparatus in a fashion specific to volume element. 
         [0045]    In a departure from  FIG. 4 , in  FIG. 5  the beam exit has been adopted as part of a gantry, and rotated by an angle into a further irradiation position with another angle of incidence. A similar situation can be obtained for a treatment center with two beam exit possibilities. A treatment room isocenter  63  is indicated for irradiation with, for example, protons from this angle, and a treatment room isocenter  65  is indicated for irradiation with carbon ions. The treatment room isocenters can be optimized to the types of particles at the spacing from the beam exit. If the therapy plan includes an irradiation procedure with one of these types of particles at this angle, the patient is moved for irradiation such that the associated therapy plan isocenter is matched with the treatment room isocenter. The imaging unit is moved to this end, and the positioning unit  43  is driven in accordance with the respective treatment room isocenter.