Abstract:
A system for treating a patient by proton therapy, also called gantry, includes a proton beam guide involving, in particular, magnets, quadropoles, and the like and having an outlet aperture for guiding and directing the proton beam to the side in the patient that is to be treated. In addition, a patient table that cab en displaced in a controllable manner is provided for moving the patient into a desired position relative to the proton beam. The inventive proton beam guide and control device is mounted down from the patient table in the direction of the beam guide in a supported manner whereby being able to rotate or pivot about a horizontal axis.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   The present application is a continuation of international application PCT/CH03/00618, filed on Sep. 15, 2003, which designated the United States; and further claims priority to Swiss patent application 1579/02, filed Sep. 18, 2002; the both of which are herein incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to an arrangement for treating a patient by means of proton therapy according to the pre-characterizing clause of claim  1  as well as uses of said arrangement. 
   Although proton radiation therapy is advantageous particularly for the irradiation of tumors, it is still only used to a very limited extent because of high costs and the large amount of space required for such installations. 
   Proton therapy is nowadays preferably applied with the aid of a rotating beam delivery system, referred to as the gantry. 
   The system is mounted on a rotating structure and can therefore be rotated around the patient table. This configuration enables the beam to be applied sequentially to the patient (lying in his immobilization device on the patient table) from several irradiation directions. 
   For the treatment of deep-seated tumors using proton therapy, the required energy of the proton beam is between 70 and 250 MeV. Because of the considerable beam rigidity, the gantry requires a large amount of space (using normal magnets, the minimum deflection radius which can be applied to the beam is at least 1.3 m) and is correspondingly heavy. Gantries for photon therapy are typically 10 m long, have a diameter of 4 to 12 m and weigh up to a hundred tonnes. 
   A modern gantry system is expected to enable the patient table also to be rotated about the vertical axis in the horizontal plane (in addition to the axial rotation of the gantry). The aim of this is to ensure that virtually all irradiation directions to the patient lying on the table can be selected from the system (ideally a 4π solid angle). The rotation of the patient table and gantry are therefore equally justified in functional terms. The new concept of this work is to limit the rotation of the gantry to +/−90° and to utilize the full 360° rotation capability of the table for this purpose (like the latitudinal and longitudinal division of world geography). For historical reasons, this relationship has been implemented the other way round in all previous systems, i.e. rotation of the gantry through 360° and of the table only through 180° maximum. 
   Today&#39;s commercially available systems are based on the concept that the gantry can be rotated completely through 360° about the longitudinal beam axis. The principle of a conventional system of this kind will now be described schematically and in detail with reference to  FIG. 1 . 
   The Paul Scherrer Institute has already made a significant contribution to the development of proton therapy. PSI&#39;s Gantry 1 is the world&#39;s second oldest photon gantry after Loma Linda in California. In operation since 1996, it is still the only gantry employing dynamic beam-scanning. It remains the gantry with the smallest diameter anywhere (4 m). A number of features derived from the PSI system have already been used in modified form for industrial patents. Such systems are described, for example, in the two European patents EP 0 911 964 and EP 0 864 337. 
   Experience with the present system has shown us the importance of good accessibility to the patient table in each radiation phase. 
   International patent application WO 01/00276 on this subject from the year 2000 (priority 1999) describes a device for performing proton therapy wherein the proton beam guiding and controlling device is implemented so that it can pivot or rotate only through a maximum angle of 270°, so that, as required, good accessibility to the patient table is ensured in each phase of radiation. WO 01/00276 will not be described in detail here, but a proton radiation arrangement similar to WO 01/00276 will be described schematically in further detail with reference to  FIG. 2 . 
   Although the requirement for accessibility to the patient table is met in the arrangement according to WO 01/00276, the requirement for dimensional reduction and simplification of the gantry remains. One object of the present invention is therefore to propose a different arrangement for performing proton therapy which, on the one hand, ensures continuous accessibility to the patient table without penalties in terms of functionality and, on the other, allows further simplification and increased accuracy in performing proton therapy, as well as in particular a further reduction in the dimensions of gantry components and of the gantry itself. 
   This object is achieved according to the invention primarily by means of an arrangement as set forth in claim  1 . 
   SUMMARY OF THE INVENTION 
   According to the invention it is proposed that the proton beam guiding and controlling device, hereinafter referred to as the gantry, is mounted downstream of the patient table in the beam guiding direction and is supported in a rotatable or pivotable manner about a horizontal axis, the essential feature remaining that at all times the patient table is accessible and the patient can be attended to from one side. 
   According to a preferred embodiment variant, the inventive arrangement or gantry is pivotally mounted via a small roller at its frontmost point, the gantry being disposed so that it can pivot or rotate upward and downward through up to 135° in each case from a horizontal plane, essentially running through the axis of rotation, similarly to the implementation according to WO 01/00276. Obviously, the total angle of 270° mentioned can also be selected smaller, depending on the design of the gantry, but must not be less than ±90° from the horizontal plane or 180° in total. 
   An advantage of the proposed arrangement according to the invention is that at least part of the cabling can be connected from the front of the gantry, which allows a clean, local separation of the cable runs for measurement signals and monitoring sensors from the magnetic feed. This eliminates any interference between the signals, thereby also enabling the proton beam guiding accuracy to be increased, as the sensitive measurement devices are unaffected by the magnetic feeds. 
   According to another embodiment variant, the heavy part of the proton beam guiding and control unit or gantry, such as the 90° magnet, is concealed so that only the nozzle of the proton beam is visible to the patient. The term “nozzle” denotes the housing and the radiation apparatus contained therein at the beam exit of the gantry immediately in front of the patient. Also located there are e.g. the measuring systems for monitoring the beam (measurement of the beam position and intensity), the range modulator, laser and TV cameras for positioning the patient and adjusting the beam, etc. This part is visible to the patient. On the other hand, the heavy part with the 90° magnet, which can weigh as much as 20 t and may have recesses 2 m high and 1 m wide or more, can be well concealed in the present arrangement by implementing the radiation chamber, according to a further embodiment variant, as a semi-open space, e.g. the size of a room, the lateral wall being absent from the accessibility side only. 
   The main advantages of the proposed arrangement according to the invention are as follows:
         The configuration of the radiation chamber is simpler;   The costs and complexity for implementing a movable auxiliary floor are eliminated;   The patient table is accessible at all times;   Smaller dimensioning of the gantry is possible, or the pit below the patient table can be made less deep.   Simpler and cheaper system;   Higher reliability and accuracy;   Smaller diameter of the system or rolling device by mounting of the front roller   The new arrangement is suitable not only for centric systems as described in WO 01/00276 but also for eccentric systems (gantry) like the present system (gantry) of the Paul Scherrer Institute (PSI).       

   Other preferred embodiment variants of the arrangement according to the invention are set forth in the dependent claims. 
   The arrangement according to the invention is particularly suitable for treating a patient using proton therapy, a person lying on the patient table being positioned by moving the patient table and proton beam delivery system (gantry) in such a way that the proton beam can irradiate the site to be treated in the patient&#39;s body from any desired direction and that the patient table remains accessible from one side at all times. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The invention will now be explained in greater detail using examples and with reference to the accompanying drawings, in which: 
       FIGS. 1   a  and  1   b  schematically illustrate a commercially available compact proton gantry with conventional mechanics, sectioned longitudinally and along the line A-A, 
       FIGS. 2   a  and  2   b  schematically illustrate a compact proton gantry sectioned longitudinally and along the line B-B, in accordance with WO 01/00276, 
       FIGS. 3   a  and  3   b  schematically illustrate a front-supported proton gantry arrangement according to the invention, sectioned longitudinally and along the line C-C, 
       FIG. 4  is a lateral perspective view of a centric gantry according to the invention, 
       FIG. 5  is a lateral perspective view of an eccentric gantry according to the invention, and 
       FIGS. 6   a  thru  6   c  schematically illustrate another embodiment variant of a proton gantry arrangement according to the invention, sectioned longitudinally and along the lines C-C and D-D. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   To facilitate understanding of the present invention, a currently commercially available system based on the concept that the proton beam system or gantry can be rotated completely through 360° about the longitudinal beam axis will first be described schematically with reference to  FIGS. 1   a  and  1   b.    
   A patient  10  is treated in a cylindrical chamber, the radiation chamber  2 . The gantry  3  is installed outside the chamber. Only the last part, the so-called nozzle  4 , with the measuring equipment for checking the spatial distribution of the dose, extends into the chamber (the patient must be able to be placed as near as possible to the nozzle). 
   The whole arrangement is carried by a rotating structure  5 , including the counterweight  6  of the gantry. Item  16  shows the position of the wheels  16  on which the gantry rotates via two rollers. The rear roller  17  can be kept relatively small with a radius of approximately 1 m. The front roller is the radiation chamber itself. Item  18  shows the cable drum where the gantry cabling is connected. 
   The patient table  7  is used to position the patient in the isocenter  8  of the machine (isocenter=point of impact of the beam during gantry rotation). Because the radiation chamber and nozzle rotate together with the gantry, the table is anchored directly in front of the chamber. The table top with the patient lying thereon extends from outside into the chamber. 
   The medical requirement that the patient table be rotatable around the tumor in the horizontal plane (in the isocenter of the machine—about the A-A axis according to  FIG. 1   a ) means that the inner radius  11  of the cylindrical radiation chamber shall be at least 2 m (length of the human body). In order to clearly illustrate the rotation and the space requirement necessary for that purpose for head irradiation, the patient  10  in  FIG. 1  has been drawn in a front and side elevation perpendicular to the point of observation in each case. 
   The height of the patient table surface  7  above the floor of the radiation chamber is therefore also fixed at approximately 2 m. Without additional equipment, access by personnel  12  to the patient in the irradiation position is thus unsatisfactory. The need for a flat false floor  13  inside the chamber is highlighted in the front view in  FIG. 1  where the position of the assistant with  15  and without  14  an auxiliary floor of this kind is illustrated. 
   The construction of a flat floor  13  inside the cylindrical radiation chamber is rather complicated for various reasons. 
   If the beam is applied from below, the false floor must open and match the rotation of the nozzle (movable part of the cover for the nozzle  13   a ). Also the remaining parts of the floor, part behind  13   c  and part in front of  13   b,  cannot be anchored directly into the chamber because the radiation chamber rotates with the gantry but the floor is designed to remain horizontal. 
   The front part  13   b  of the floor can be supported from outside the chamber. However, the main problem is in the rear part of the chamber, in part  13   c,  which is “cut off” by the movement of the nozzle. The problem can be solved here using a built-in counter-rotation  19  to the rotation of the gantry in the rear part of the chamber, according to the principle used for installing the patient table in the PSI&#39;s Gantry 1. 
   This idea (of counter-rotation) has been subsequently adopted for supporting the false floor. Commercial systems currently in existence all have either no floor in the cylindrical chamber or a floor which is constructed according to the principle outlined above (rear support with counter-rotation, front support fixed). 
   Although a movable floor inside the cylindrical radiation chamber is feasible, it is certainly neither cheap nor easy. 
   The object of WO 01/00276 of the PSI was to offer a better solution ensuring better accessibility to the patient table, without penalties in terms of functionality, and with the floor  13   b  and  13   c  installed in a fixed manner without counter-rotation. 
     FIGS. 2   a  and  2   b  schematically illustrate the gantry arrangement proposed in WO 01/00276 sectioned longitudinally and along the line B-B. It should be noted that  FIGS. 2   a  and  2   b  employ the same reference characters to denote the corresponding parts in  FIGS. 1   a  and  1   b.    
   The difference between the gantry described in  FIGS. 2   a  and  2   b  and the corresponding system shown in  FIGS. 1   a  and  1   b  is primarily that the rotation of the gantry is limited to ±90° (+180°, −120°) in the vertical plane on one side of the gantry only. This is particularly evident from the illustration according to  FIG. 2   b.  The non-settable angles of the gantry are selected mirror-symmetrically and achieved using rotation of the patient table through 180° in the horizontal plane. In principle, if the rotation of the table in the horizontal plane is fully available, no limitations in the selection of the irradiation direction are likely at least theoretically. The space gained on the opposite side of the gantry can therefore be utilized for the fixed installation of the patient table  7  and of the fixed floor  13  in the hole of the pit.  FIGS. 2   a  and  2   b  likewise clearly illustrate that accessibility to the patient table is provided in a much easier and better manner compared to the arrangement shown in  FIGS. 1   a  and  1   b.    
   However, as is also evident from  FIG. 2   a,  the system is very large because of the use of the large rotating disk  20  and requires a large amount of space. The approximately 7 m rotating disk is difficult to construct and to transport. The required precision of the isocenter of better than 1 mm is correspondingly difficult to implement. It should additionally be noted that the wheels  16  in  FIG. 2  are below the large roller  20  and therefore the pit is made deeper than that shown in  FIGS. 1   a  and  1   b.    
   In order to further simplify the system, the inventive arrangement schematically illustrated in  FIGS. 3   a  and  3   b  has now been selected. The basic idea of the newly developed gantry consists in supporting the radiation unit or gantry only after the radiation chamber using a small roller  21 . This obviates the need for the correspondingly large-diameter rotating disk shown in  FIG. 2   a.  The other features of the arrangement according to  FIGS. 2   a  and  2   b  are essentially retained in the new concept.  FIG. 3   a  schematically illustrates the inventive arrangement sectioned longitudinally and  FIG. 3   b  shows a cross-section along the line C-C. It now becomes clear that the gantry  3  is rotatable in a laterally limited manner similar to the arrangement shown in  FIGS. 2   a  and  2   b.  The radiation chamber  2  is in turn accessible from one side of the gantry. The radiation chamber  2  is preferably a semi-open space the size of a room, measuring approximately 4.5 m long, approximately 4 m deep from the side and approximately 2.2 to 2.5 m high. For the patient, only the final element of the proton beam delivery system or nozzle is visible, the heavy part of the gantry such as the 90° magnet being concealed. The floor is installed in a fixed manner in the areas  13   c  and  13   b  similar to  FIGS. 2   a  and  2   b  apart from a slit (approximately 50 cm wide) for guiding the nozzle. This area can be covered e.g. using a bilateral rolling cover ( 13   a ). As already mentioned above, the clear advantages of the arrangement according to the invention lie in the following features:
         Probably the greatest advantage of this arrangement is that the manufacturing costs of the large roller  20  from  FIG. 2  are eliminated by supporting the gantry via a small roller at its frontmost position and the associated rotation.   In addition, the advantages of this solution remain the good accessibility to the patient table with an almost exclusively fixed floor.   The space around the patient table is large and can be conveniently configured, it also being possible to install further equipment on the fixed floor within range of the table, such as an anesthetics table, a computer tomograph (CT), a positron emission tomograph (PET), etc.   At least part of the cabling can be connected at the front of the gantry. This allows a clean, local separation of the cable runs for measurement signals or monitoring sensors from the magnetic feed.   The arrangement permits a space-saving design of the access labyrinth or shielding configuration.   The shielding on the walls of the radiation chamber can be reduced wherever these face away from the gantry.       

   A further advantage of the new concept is that it can be used not only for centric compact systems, as shown in  FIGS. 2   a  and  2   b,  but also for eccentric compact systems as shown in  FIG. 5 , for example. However, because of the eccentricity the radiation chamber must be suspended on the gantry e.g. in the sense of a counterweight and kept horizontal with the aid of the counter-rotation. 
   Moreover, conceptually the new solution is generally more flexible than the solution shown in  FIGS. 2   a  and  2   b.  Whereas the latter is only possible for a more compact gantry, the new system can be used both for compact, compact-eccentric and for “long throw gantries” as well as for beam application using scanning or scattering technologies. The large variability is attractive for commercial use, particularly if customer-oriented solutions are to be offered. 
     FIGS. 4 and 5  illustrate by means of perspective views the use of the arrangement according to the invention both in a compact centric system and also in an eccentric compact gantry system. 
     FIG. 4  is a perspective view of a centric gantry pivoted about the axis of rotation  1  via the two rollers  17  and  21 , radiation being applied from the top right (viewed from the patient). 
   The arrangement is called centric because the gantry is rotatable around the radiation chamber  2  disposed in a rigid or fixed manner whereby the chamber floor  13  is fixed. 
   In contrast, in the arrangement according to  FIG. 5  the radiation chamber is pivoted eccentrically in a circular motion about the axis of rotation  1 , the patient table  10  obviously having to perform a corresponding movement depending on the radiation position. In this case radiation is applied from top left. In order to ensure the accessibility of the chamber floor  13  for an attendant  12 , a movable e.g. stepped access  27  is necessary. For example, if the radiation is applied in the horizontal direction, the need for the steps  27  is eliminated, as the chamber floor  13  is on the same level as the surrounding area. However, if the radiation is applied from below, the chamber floor  13  is elevated accordingly and is therefore above the level of the surrounding area. 
     FIGS. 6   a  and  6   b  show another embodiment variant of a gantry arrangement or system according to the invention. The system illustrated in  FIGS. 6   a  and  6   b  differs from that shown in  FIGS. 3   a  and  3   b  in that the rear support of the gantry is not positioned at the end, but is oriented toward the interior or toward the radiation room  2 . Otherwise, the gantry in  FIG. 6   a  corresponds to that in  FIG. 3   a,  as does the section along the line C-C shown in  FIG. 6   b.  On the other hand,  FIG. 6   c  shows the section along the line D-D, i.e. the rear support of the gantry, the rear wheel  16  being supported laterally on the rear chamber wall  50  via an e.g. U-shaped frame  31 , i.e. the support is provided on the chamber floor  9 , unlike in  FIG. 3   a.  It is accordingly possible to implement the cable drum  18  in the central area of the gantry. The way the gantry is supported, as shown in  FIGS. 6   a  to  6   c,  shortens the structure and because of the shorter distance between rear and front roller  16 , better stability is achieved, i.e. there is less risk of sagging. The other advantages, as described with reference to  FIGS. 3   a  and  3   b,  are of course retained in the arrangement according to  FIGS. 6   a  to  6   c.    
   The representations in  FIGS. 1 to 6  are of course merely examples used to explain the present invention in more detail. 
   It is self-evidently possible to adapt the proton radiation arrangement in any number of ways, to modify it or to supplement it with further elements. Particular reference is made to WO 01/00276 whose content is an integral part of the present invention, and whose specific embodiments, likewise in combination with the features defined according to the invention, are part and parcel of the present invention.