Abstract:
A lamella collimator, in particular for a beam therapy appliance, is provided. The lamella collimator has a plurality of lamellae, which can be moved by a motor or motors in a movement direction in order to preset a countour of a beam path on an X-ray beam. Each lamella has a position measurement apparatus with a movable measurement element, which is attached directly to the respective lamella.

Description:
[0001]    The present patent document claims the benefit of the filing date of DE 10 2006 039 793.2, filed Aug. 24, 2006, which is hereby incorporated by reference. The present patent document also claims the benefit of the filing date of PCT/EP2007/057908 filed Jul. 31, 2007, which is also incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The present embodiments relate to a lamella collimator. In particular, the present embodiments relate to a beam therapy appliance, and to a beam therapy appliance with a lamella collimator. 
         [0003]    A lamella collimator is used in radiation therapy for the treatment of tumors. DE 196 39 816 A1 and WO 00/46813 describe lamella collimators. During radiation therapy, a tumor is irradiated with high-energy beams, generally with high-energy X-ray radiation from a linear accelerator. The lamella collimator may be placed in the beam path of the X-ray beam. The lamella collimator includes a plurality of lamellae that can be displaced against each other by a motor to define an aperture with a contour corresponding to the contour of the tumor. Only the tumor is irradiated with the X-rays; not the adjacent healthy body tissue. Two sets of lamellae may be arranged in relation to each other in such a way that their end faces can be moved toward and away from each other. As a result, virtually any tumor contour may be modeled. 
         [0004]    Each of these lamellae can be individually displaced by an electric motor. During the positioning of a lamella, there can be slight deviations between a desired value and the actual set position of the lamella. Each lamella includes a position measurement apparatus with which the actual position set can be determined. 
         [0005]    Particularly narrow lamellae are used to model very fine contours. DE 196 39 861 A1 describes a lamella collimator with narrow lamellae. In addition, the lamellae of the lamella collimator are often arranged in a semicircular shape in the beam direction and slightly inclined toward each other. This is a reliable way of avoiding narrow gaps between the individual lamellae, which greatly reduce the shielding effect of the lamella collimator in this region and would result in the irradiation of healthy body tissue. 
         [0006]    With the lamella collimator described in DE 196 39 861 A1, the individual lamellae are provided on their upper edges on the side facing way from the beam side with oblong connecting cords, the other end of which engage the cords of a position measurement apparatus, which is not shown, for example by ball connectors. For reasons of space, as seen from the direction of travel of the lamellae, the connecting cords spread out in a fan shape, like that in a mechanical typewriter. 
         [0007]    The mechanical connection of the individual position measurement apparatuses to individual lamellae is very complicated. 
       SUMMARY AND DESCRIPTION 
       [0008]    The present embodiment may obviate one or more of the limitations or drawbacks inherent in the related art. For example, in one embodiment, a lamella collimator includes a simplified and easy-to-maintain position measurement apparatus. A beam therapy appliance may include the lamella collimator. 
         [0009]    In one embodiment, for each lamella, the lamella collimator may include a position measurement apparatus with a movable measuring element that is attached directly to the associated lamella. A structural connection between a lamella and the associated position measurement apparatus may not be needed using an intermediate element, such as, for example, a strip-like connecting cord. According to the prior art, these connecting elements have an oblong design and spread out in a fan shape, there is always also the risk of the individual connecting elements interlocking. This risk of interlocking no longer exists when the position measurement apparatus is directly connected to a lamella. The operational reliability of the lamella collimator is also increased. There is no need for the complex mechanical alignment of the individual connecting cords during production. 
         [0010]    In one embodiment, the attachment of the measurement element to the lamella is a joint. With lamellae that are obliquely inclined toward each other, the connection of the position measurement apparatus is simplified. The use of a joint avoids or at least greatly reduces mechanical stresses. The joint is, for example, a ball-and-socket joint or as a hinge joint. 
         [0011]    In one embodiment, the measurement element and the lamella are attached to each other by a connection including a bolt and a bolt holder. A bolt connection is simple to make. A bolt can be made in such a way that it is constructed no wider than the lamella. Therefore, the measurement element can be attached directly behind the lamella in a particularly space-saving way. If the bolt holder is also embodied rotatably in the longitudinal direction of the bolt, the measurement element can be moved against the lamella in the manner of a hinge. 
         [0012]    The bolt includes a detent groove for latching and fixing in the bolt holder. Therefore, the connection between the bolt and the bolt holder is secured in such a way that the bolt is unable to slip out of the bolt holder. This reliably prevents any failure of the position measurement apparatus. 
         [0013]    In one embodiment, the position measurement apparatus includes a measuring plate as a measurement element and a plate holder for holding this measuring plate. An essentially plate-shaped measurement element is particularly simple to make. If the corresponding plate holder is provided with side walls aligned parallel to each other, the measuring plate can slide back and forth in this plate holder with virtually no friction resistance when the lamella is displaced in the movement direction. As a result, the displacement of the lamella is not impeded. The measuring plate lies flat on the wall of the plate holder and achieves good contact between the measurement element and the plate holder. 
         [0014]    In one embodiment, in the longitudinal direction and parallel to the movement direction of the lamella collimator, the measuring plate comprises at least one guide rail as a guide element to guide it along a contour of the corresponding plate holder. As a result, there is particularly reliable guidance of the measuring plate in the plate holder. 
         [0015]    At least two guide rails are arranged opposite to each other on the measuring plate in the transverse direction and perpendicularly to the beam direction and to the movement direction. Since both these guide rails are guided by a contour of the corresponding plate holder, fail-safe guidance of the measuring plate is achieved. 
         [0016]    In one embodiment, the position measurement apparatus is a potentiometer. A potentiometer may be used to measure a resistance proportional to the position of the lamella. The resistance measurement can be implemented in a cost-effective way. 
         [0017]    In one embodiment, the measuring plate includes at least one contact element and the plate holder sliding contact corresponding to the contact element. With a flat embodiment of both the contact element and the corresponding sliding contact, the position measurement apparatus, embodied as a potentiometer, can achieve a reliable and precise measurement. 
         [0018]    Each contact element is attached to the measuring plate by at least one fixing element. For example, the at least one fixing element is a stud onto which the contact element provided with a stud holder can be simply plugged. The contact element can be assembled or replaced easily so that the ease-of-maintenance of the position measurement apparatus of the lamella collimator is greatly increased. 
         [0019]    In one embodiment, the plate holder and the measuring plate guided and held are essentially arranged in the beam direction above the upper transverse side or below the lower transverse side of the lamella. As a result, the displacement of the individual lamellae in the movement direction is not impeded and, a plurality of plate holders can be combined in the form of a module so that the assembly of this module inside the lamella collimator is greatly simplified and that it may be replaced quickly in the event of an error. The production of plate holders arranged next to each other in module form reduces the production costs enormously. 
         [0020]    In one embodiment, the measuring plate is made of plastic. A measuring plate made of plastic has a low moving mass. As a result, the risk of interlocking and blocking of the measuring plate and the lamella during displacement is greatly reduced. The production of the measuring plate from a plastic can be achieved in a particularly cost-effective manner. 
         [0021]    In one embodiment, the position measurement apparatuses of adjacent lamellae are arranged in the beam direction in alternation above the upper transverse sides and below the lower transverse sides. In the case of lamellae with a particularly narrow design, the associated measuring plates with their measuring holders are designed wider than the individual lamellae. The alternating arrangement enables, viewed over the width, twice as many plate holders to be accommodated, which are then arranged respectively above the upper and below the lower transverse sides of the lamellae. 
         [0022]    The object is also achieved by a beam therapy appliance with a lamella collimator. The advantages described for the preferred embodiments with respect to the lamella collimator may also be transferred to a beam therapy appliance with a lamella collimator of this kind. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  illustrates a schematic top view of a lamella collimator, 
           [0024]      FIG. 2  illustrates another schematic view of a position measurement apparatus view from the rear end face of the lamella collimator, 
           [0025]      FIG. 3  illustrates the upper end of the side of a lamella facing away from the beam with a bolt, 
           [0026]      FIG. 4  illustrates another view of the end the lamella facing away from the beam with a measuring plate pushed onto the bolt measuring plate, 
           [0027]      FIG. 5  illustrates a plurality of measuring plates in plate holders arranged next to each other and 
           [0028]      FIG. 6  illustates a schematic view of a beam therapy appliance with a lamella collimator. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]      FIG. 1  shows is a schematic top view of a lamella collimator  2  including a plurality of plate-type lamellae  4  arranged essentially parallel to each other. These lamellae  4  can be displaced in the movement direction  6  by a motor. For the displacement, in each case, the front end faces  8  of two lamellae  4  lying opposite to each other are moved toward or away from each other. As a result, it is possible to set virtually any contour  10  for the irradiation of a tumor with an X-ray beam passing through the lamella collimator  2  in the beam direction  12 . In  FIG. 1 , viewed from the image plane, this X-ray beam  12  passes from top to bottom through the irradiation contour  10  through the lamella collimator  2 . 
         [0030]      FIG. 2  illustrates a plurality of lamellae in a slightly angled alignment viewed from their rear end faces  14 . Viewed over the entire width, all the lamellae  4  are aligned in a slightly semi-circular shape with respect to each other. This avoids gaps, which would result in the passage of X-ray radiation outside the contour  10 .  FIG. 2  shows the beam direction  12  running from top to bottom. However, the X-ray beam also passes outside the image plane in the region of the front end faces  8  of the lamellae  4 . 
         [0031]    At each rear end face  14  of a lamella  4 , a position measurement apparatus  18  is attached directly by a joint  16 . For purposes of clarity, the drawing only shows only two position measurement apparatuses  18 . These position measurement apparatuses  18  are arranged on the lower transverse sides  20  of the lamellae  4 , viewed from the beam direction. 
         [0032]      FIGS. 3 to 5  show the embodiment of a position measurement apparatus  18  in more detail. 
         [0033]      FIG. 3  shows a lamella  4  in the region of its rear end face  14  and the upper transverse side  22 . A bolt holder  24  is attached counter to the beam direction  12  above the upper transverse side  22 . One end of a bolt  26  is held and fixed in the bolt holder  24  by a fixing bore. During a displacement of the lamella  4  in the movement direction  6  toward the beam region, the end face  28  of the bolt holder  24  facing the X-ray beam in the movement direction  6  serves as an end stop so that the lamella  4  cannot be further moved. 
         [0034]    The cylindrical bolt  26  extends from the rear end face  14  of the lamella  4  parallel to the movement direction  6  from the rear end face. It has an assembly stop  30  and a detent groove  32  for fixing a measuring plate shown in  FIG. 4 . 
         [0035]      FIG. 4  shows a lamella  4  in the region of its rear end face  14  and its upper transverse side  22 . A measuring plate  34 , with a bolt holder  36  embodied as a hollow cylinder, is pushed onto the bolt  26 . The measuring plate  34  is pushed on as far as the assembly stop  30  of the bolt  26  so that the detent groove  32  of the bolt latches in a contour of the bolt holder  3 . The measuring plate  34  is attached directly to the lamella  4  by the bolt  26 . In the movement direction  6  of the lamella  4 , no movement of the measuring plate  34  relative to the lamella  4  is possible. However, the measuring plate  34  can be swiveled about the central longitudinal axis  38  of the bolt  26  in the manner of a hinge. 
         [0036]    The measuring plate  34  includes a plate body  40  counter to the beam direction above the bolt holder  36 . Close to the bolt holder  36 , the plate body  40  includes two opposing guide rails  42  extending in its transverse direction parallel to the upper transverse side  22  of the lamella  4  and perpendicular to the movement direction  6 . The plate body  40  includes, at its end lying opposite to the bolt holder  36 , a further two opposing guide rails  42 . Attached to both sides of the surface of the plate body  40  are in each case four lug-like fixing elements  44  to each of which a contact element can be latched, the contour  46  of which is indicated in  FIG. 4 . 
         [0037]    Each measuring plate  34  is pushed into a corresponding plate holder  48  as shown in  FIG. 5 . 
         [0038]      FIG. 5  shows a plurality of plate holders  48  arranged next to each other, into each of which a measuring plate  34  is inserted and held. The side walls  50  of the plate holders  48  are aligned parallel to each other. Inserted in the side walls  50  of the plate holders  48  in  FIG. 5  are guide contours, so that each measuring plate  36  is reliably held and guided in the plate holder  48  by its two pairs of guide rails  42 . 
         [0039]    The position measurement apparatus  18  functions according to the principle of a potentiometer. Each contact element  46  of a measuring plate  34  comes into contact with a sliding contact arranged on one of the two side walls  50  of a plate holder  48 . The combination of the contact element  46  and the sliding contact forms a potentiometer circuit. A displacement of the measuring plate  34  in the corresponding plate holder  48  causes the resistance of the potentiometer circuit to change. The change in the resistance is proportional to the local position of the lamella  4  in the movement direction  6 . A potentiometer circuit of this kind can be established in a particularly simple and cost-effective way. 
         [0040]      FIG. 5  is summary of a plurality of plate holders  48  in a measuring module  52 . 
         [0041]    The measuring plate  34  with its guide rails  42  is wider than a lamella  4 . In addition, the width of the side walls  50  of the plate holder  48  takes up space. Only every second lamella  4  has a position measurement apparatus  18  to be positioned above its upper transverse side  22 . The intermediate lamellae  4  include a position measurement apparatus  18  arranged similarly to the depiction in  FIG. 2  on its lower transverse side  20 . 
         [0042]    A measuring module  52  with plate holders aligned parallel to each other is arranged above the upper transverse sides  22  of the lamellae. A measuring module  52  is arranged below the lower transverse sides  20  of the lamellae. 
         [0043]    This enables the direct connection of the position measurement apparatuses  18  to the lamellae  4  even in the case of lamellae  4  with a narrow design. In the event of a fault, a measuring module  52 , including a plurality of plate holders  48 , can easily be exchanged as a whole. No complex adjustment work, such as that in the case of the connection of position measurement apparatuses via connecting cords to the lamellae, is required. Despite the inclination of the lamellae  4 , due to the position measurement apparatus  18  attached by a joint  16  to each lamella  4 , the parallel alignment of the side walls  50  of the plate holders  48  is possible, since the joints  16  counteract the occurrence of mechanical stresses. This in turn reduces the production costs. 
         [0044]      FIG. 6  shows a schematic side view of a beam therapy appliance  54  including a holding device  56  and a lamella collimator  2  arranged in a housing. By a focusing mimic, the X-ray beam  58  passes through the lamella collimator  2  in the beam direction  12 . The lamella collimator  2  defines a contour  10  for the irradiation of a tumor by its individual movable lamella  4 . 
         [0045]    Various embodiments described herein can be used alone or in combination with one another. The forgoing detailed description has described only a few of the many possible implementations of the present invention. For this reason, this detailed description is intended by way of illustration, and not by way of limitation. It is only the following claims, including all equivalents that are intended to define the scope of this invention.