Title of Invention

A RADIATION DIAPHRAGM TO NARROW AN X-RAY BEAM PRODUCED BY AN X-RAY TUBE OF AN X-RAY FACILITY AND X-RAY FACILITY THEREOF

Abstract

The invention relates to a radiation screen (30) for an X-ray device (1), comprising at least one radiation limiting means which is displaceably mounted and is embodied as a diaphragm. According to the invention, the radiation limiting means is displaceably mounted on a plane in a perpendicular manner in relation to a defining bundle of rays (6), and comprises a plurality of differently shaped diaphragm apertures (40 ... 51, 60 ... 66) for continuously limiting the different bundle of rays (6). It can, for example, be embodied as an essentially rotation-symmetrical perforated disk. In another embodiment, the radiation screen comprises two radiation defining means which are arranged in an overlapping manner in the direction of the bundle of rays (6) which are to be defined.

Full Text

Description The invention relates to a radiation diaphragm for an x-ray facility and an x-ray facility with such a radiation diaphragm. Radiation diaphragms are used in x-ray facilities to narrow an x-ray beam bundle produced by an x-ray tube to form a useful beam bundle. Regions outside the useful beam bundle are masked out by the radiation diaphragm, so that its form decides the residual contour of the useful beam bundle. It is expedient to vary the contour as a function of the respective task. When examining patients or bodies, the aim is to achieve a contour of the useful beam bundle that is tailored as precisely as possible to the volume to be examined, to avoid exposing the surrounding region to an unnecessary radiation dose. Radiation diaphragms disposed in immediate proximity to the x-ray tube are also referred to as primary radiation diaphragms. They frequently have a number of individual diaphragms, disposed at different distances from the x-ray tube. An initial rough narrowing of the x-ray beam is frequently effected by means of a diaphragm disposed first in the beam path, sometimes referred to as a collimator, which brings about an approximately rectangular definition of the beam bundle by means of one or two pairs of diaphragm plates. Finer definition, the contour of which is not necessarily set as rectangular in form, then takes place by means of a similarly adjustable diaphragm disposed in the further beam path. It is known from EP 0 485 742 that the further diaphragm can be embodied as an iris diaphragm. Generally iris diaphragms produce an approximately circular definition of the x-ray beam bundle, the diameter or typical size of which can be adjusted extremely finely, usually in a continuous manner. One disadvantage of iris diaphragms however is that they have a relatively large number of moving parts and are therefore both complex to construct and expensive to produce. Iris diaphragms have louvers, which are mounted in a displaceable manner and bring about the actual masking of regions of the x-ray beam bundle that are not of interest. An additional disadvantage is that both the louvers themselves and also their mounting are susceptible to damage due to the louver movement. A radiation diaphragm for a portable x-ray facility is known from BE 100 9333, being designed as a perforated diaphragm. It has a radiation defining means, formed as a cylinder and disposed concentrically in relation to the x-ray tube. It has a plurality of diaphragm apertures, each being able to be positioned by rotating the radiation defining means in front of the beam emission window. One disadvantage of this is that the cylindrical form of the radiation defining means has to be tailored to the x-ray tube, around which it is disposed. It is also disadvantageous that the radiation defining means cannot be disposed freely but requires an arrangement that is concentric to the x-ray tube. It is also disadvantageous that this arrangement also requires a complex rotational mounting, since the x-ray tube is disposed in the center of the radiation defining means, where a rotation axis should advantageously be disposed. The object of the invention is to specify a radiation diaphragm, which allows fine adjustment of the contour of the useful beam bundle, but which is at the same time simple to construct and economical to produce. A further object of the invention is to specify an x-ray facility with such a radiation diaphragm. The invention achieves this object by means of a radiation diaphragm with the features of the first claim and by means of an x-ray facility with the features of the eleventh claim. A basic concept of the invention consists of specifying a radiation diaphragm, having at least one radiation defining means mounted in a displaceable manner and being embodied as a perforated diaphragm, which is mounted in a displaceable manner in a plane perpendicular to a beam bundle to be limited, and which has a plurality of differently formed diaphragm apertures for the respectively differently contoured definition of the beam bundle. This has the advantage that the arrangement and mounting of the radiation defining means is independent to the greatest possible extent of the form and position of the x-ray tube producing the beam bundle. This means that the form and mounting can be designed as simply as possible, thereby also keeping production costs as low as possible. A perforated diaphragm can also be produced particularly simply, in particular compared with an iris diaphragm. In one advantageous embodiment of the invention the radiation defining means is mounted in a rotatable manner in the plane perpendicular to the beam bundle. A rotational mounting can for example be realized with little outlay in the form of a simple rotation axis; also rotational movement can be driven and controlled in a particularly simple manner. In a further advantageous refinement of the invention the radiation defining means is embodied as a perforated disk with a round periphery. The space requirement of a circular disk is particularly small, in particular during rotational movement of the same. In a further advantageous refinement of the invention the radiation diaphragm has at least two radiation defining means, which are disposed in a mutually overlapping manner in the direction of the beam bundle to be defined. This allows the required, differently formed diaphragm apertures to be distributed over the more than one radiation defining means. This allows a space-saving arrangement of the diaphragm apertures on the respective radiation defining means, so that a smaller periphery results, in particular in the case of round radiation defining means and the overall surface can be utilized in a more optimum manner. This becomes apparent, when one considers that to double the number of diaphragm apertures, which have to be disposed on an identical radius of a round perforated disk, it would be necessary approximately to double the perforated disk radius (because circumference = 2 * n * r), with the surface content of the perforated disk however being quadrupled (because surface -n* r2). However if the double number of diaphragm apertures is distributed over two perforated disks, there is only a doubling of the overall surface of the perforated disks. Further space-saving results in that the radiation defining means are disposed in an overlapping manner, thereby reducing their overall surface extension by the sum of the mutual overlap. In a further advantageous refinement of the invention each of the radiation defining means disposed in a mutually overlapping manner has at least two diaphragm apertures, each being able to be disposed completely within the periphery of at least one diaphragm aperture of the respectively other radiation defining means. This allows the diaphragm apertures to be positioned in such a manner that the beam bundle passes respectively through a diaphragm aperture of each radiation defining means and at the same time gives the greatest possible diversity of variation for the contours of the defined beam bundle to be achieved. Further advantageous refinements of the invention will emerge from the dependent claims and the description which follows of exemplary embodiments with reference to the figures, in which: Figure 1 shows an x-ray facility with radiation diaphragm, Figure 2 shows a first flat disk of the radiation diaphragm, Figure 3 shows a second perforated disk of radiation diaphragm, Figure 4 shows a mutually overlapping arrangement of the perforated disks to achieve a first diaphragm aperture, Figure 5 shows a mutually overlapping arrangement of the perforated disks to achieve a second diaphragm aperture, Figure 6 shows a mutually overlapping arrangement of the perforated disks to achieve a third diaphragm aperture Figure 7 shows a mutually overlapping arrangement of the perforated disks to achieve a fourth diaphragm aperture. Figure 1 shows a schematic diagram of an x-ray facility 1 with radiation diaphragm 30. A patient to be examined 7 is supported on a patient bed 2. Below the patient bed 2 is an image receiver 5 along with associated scattered radiation grids 16 for recording x-ray images. The patient bed 2 is attached to a gantry 3. Also attached to the gantry 3 is an x-ray radiation source 4. The x-ray radiation source 4 has an x-ray tube 18 for producing x-ray radiation and a (conventional) primary diaphragm 17 for rough definition of the x-ray beam bundle 6. The primary diaphragm 17 has two diaphragm plates, allowing an essentially right-angled definition. After passing through the primary diaphragm 17 the x-ray beam bundle 6 is defined further to the required contour by the perforated disks 19 and 22, which together form a space-saving and structurally simple second radiation diaphragm. It is also possible here to achieve contours that are not rectangular and it is also possible to set a number of dimensions for the contour. The primary diaphragm 17 and the second diaphragm formed by the perforated disks 19 and 22 together form the radiation diaphragm 30. The x-ray radiation source 4 and radiation diaphragm 30 are supplied with the necessary operating voltage and control signals by way of a supply line 8. The necessary electrical signals are supplied by a switchgear cabinet 9, which has a high voltage generator 10 for generating the x-ray voltage required to operate the x-ray tube 18 in addition to switching means (not shown) for generating the control signals. The switchgear cabinet 9 in turn is connected by way of a data cable 13 to a control facility 12 and is controlled by this. The control facility 12 has a display device 15, at which current operating data and parameter settings can be displayed. A data processing facility 11 serves to process operator inputs, supplies preset x-ray programs for predefined recording situations and generates the control signals for the switchgear cabinet 9. The data processing facility 11 also accesses a diaphragm memory 14, which has information for adjusting the second diaphragm formed by the perforated disks 19 and 22. More precisely the diaphragm memory 14 has information, based on which, when an operator or x-ray program selects a required contour for the x-ray beam bundle 6, the setting for the respective perforated disk 19, 22 is determined, which allows the selected contour to be best achieved. Figure 2 shows the first perforated disk 19 of the second diaphragm schematically viewed from above. It has a circular periphery and is mounted in a rotatable manner in a centrally disposed axis support 20. It can be installed in a simple manner within the radiation diaphragm 30 using the axis support 20. A plurality of diaphragm apertures 60, 61 66 of differing forms and sizes are provided, allowing diverse contouring of an x-ray beam bundle. The perforated disk 19 is made from a material that does not allow the passage of x-ray radiation, e.g. lead or another element with a high atomic number, so that a passing x-ray beam is blocked by the perforated disk 19 and can only pass through a respective diaphragm aperture 60, .... 66. To this end the latter must simply be positioned in the x-ray beam. The differing forms and sizes of the diaphragm apertures 60 66 are only shown schematically. The round apertures can for example have a respective diameter of 10 mm, 14 mm, 18 mm, 19 mm, 20 mm and 21 mm; other individual sizes can similarly be realized without further ado. A rectangular diaphragm aperture 66 is also provided, the form and size of which are tailored to an x-ray film cassette in such a manner that this can be fully exposed by the x-ray radiation defined using this diaphragm aperture 66. To allow precise positioning of a respective diaphragm aperture 60, ..., 66 as controlled by positioning facilities, positioning marks 21, 21', 21", ... are provided on the periphery of the perforated disk 19. The position of each positioning mark 21, 21', 21", ... thereby correlates to the position of a respective diaphragm aperture 60, ..., 66, in other words the positioning marks 21, 21', 21",... enclose the same midpoint angles or arcs as the positions of the diaphragm apertures 60 66. A specific position of a respective positioning mark 21, 21', 21", ... therefore corresponds to a specific position of the respectively associated diaphragm aperture 60,..., 66. This allows precise machine positioning. Figure 3 shows the second perforated disk 22 schematically viewed from above. It is embodied in a similar manner to the perforated disk 19 described above in Figure 2 and can also be mounted in a rotatable manner in a central axis support 23. It has a plurality of diaphragm apertures 40, ..., 51 in differing sizes and therefore positioning marks 24, 24', 24", ... correlating in respect of the respective position. The individual sizes of the diaphragm apertures 40 51 are shown schematically and can have diameters for example from 5 mm to 16 mm in 1 mm steps and can also have a diameter of 30 mm for the largest diaphragm aperture 51. Figure 4 shows a schematic top view of the interaction of the perforated disks 19 and 22, which are disposed in a mutually overlapping manner in the direction of the beam path in the radiation diaphragm 30. The perforated disks 19 and 22 should be disposed in the beam bundle in such a manner that the midpoint of the mutual overlap of the two disks is disposed in the midpoint of the beam bundle. In the rotation position shown in Figure 4 the diaphragm aperture 60 of the perforated disk 19 and the diaphragm aperture 40 of the perforated disk 22 are positioned at this point. Since the diaphragm aperture 40 has the smaller diameter, it predetermines the contour and diameter of the x-ray radiation beam passing through it. The diaphragm aperture 40 is therefore of significance to the diaphragm setting actually achieved. In the embodiment of the perforated disks shown the diaphragm apertures 41, 42, 43 and 44 of the perforated disk 22 also have smaller diameters than the diaphragm aperture 60 of the perforated disk 19. Therefore with concentric positioning with the diaphragm aperture 60 they would be respectively determining factors in respect of the effective diaphragm setting. Figure 5 shows a positioning of the perforated disks 19 and 22, wherein the diaphragm aperture 45 of the perforated disk 22 and the diaphragm aperture 60 of the perforated disk 19 are disposed at the midpoint of the overlap. The diaphragm aperture 60 has a smaller diameter compared with the diaphragm aperture 45 and is therefore a determining factor for the x-ray beam bundle passing through it. The diaphragm aperture 60 therefore represents the effective diaphragm setting. Figure 6 shows a further positioning of the perforated disks 19 and 22, wherein the diaphragm apertures 51 and 64 are positioned at the midpoint of the x-ray beam bundle. Because of its comparatively small diameter, the diaphragm aperture 64 is a determining factor for the effective diaphragm setting. Figure 7 shows a further positioning of the perforated disks 19 and 22, wherein the diaphragm apertures 51 and 66 are positioned at the midpoint of the x-ray beam bundle. The rectangular diaphragm aperture 66, the contour and dimensions of which can for example be matched to an x-ray film cassette to be exposed, is disposed completely within the periphery of the diaphragm aperture 51 and therefore has smaller dimensions than this latter. It is therefore a determining factor for the effective diaphragm setting. It is clear from Figures 4 to 7 described above that the selected distribution of the diaphragm sizes over the two perforated disks 19 and 22 and their mutual overlap allows an extremely compact structure of the diaphragm thus formed to be achieved, which at the same time ensures a wide diversity of variation of the possible effective diaphragm settings. The relatively dense arrangement of the diaphragm apertures 40, ..., 51, 60 66 on the respective perforated disks 19 and 22 in particular is clear, allowing efficient utilization of the respective perforated disk surface. The invention can be summarized as follows: the invention relates to a radiation diaphragm 30 for an x-ray facility 1 with at least one radiation defining means, which is mounted in a displaceable manner and embodied as a perforated disk. According to the invention the radiation defining means is mounted in a displaceable manner in a plane perpendicular to a beam bundle to be defined 6 and has a plurality of differently formed diaphragm apertures 40,... 51, 60,... 66 for respectively differently contoured definition of the beam bundle 6. It can for example be embodied as an essentially rotationally symmetrical perforated disk. In a development of the invention there are two radiation defining means, which are disposed in a mutually overlapping manner in the direction of the beam bundle to be defined 6. We claim: 1. A radiation diaphragm (30)operative to narrow an x-ray beam produced by an x-ray tube of an x-ray facility (1) to form a narrowed beam and to mask out regions outside the narrowed beam, the radiation diaphragm (30)comprising: at least two radiation defining devices, wherein the at least two radiation defining devices are mounted on different central axis supports in a displace-able manner in planes perpendicular to the x-ray beam, and each of the at least two radiation defining devices includes a plurality of different diaphragm apertures (40...51, 60...66) with different shapes for differently contoured definition of the x-ray beam, wherein the plurality of different diaphragm apertures (40...51, 60...66) adjust the contour of the narrowed beam, and wherein each diaphragm aperture of one of the at least two radiation defining devices is disposable within the periphery of at least one diaphragm aperture of another of the at least two radiation defining devices. 2. The radiation diaphragm (30) as claimed in claim 1, wherein each of the at least two radiation defining devices extends in an essentially flat manner. 3. The radiation diaphragm (30) as claimed in claim 1, wherein each of the at least two radiation defining devices is mounted in a rotatable manner in one of the planes perpendicular to the x-ray beam. 4. The radiation diaphragm (30) as claimed in claim 1, wherein each of the at least two radiation defining devices is a perforated disk (19,22). 5. The radiation diaphragm (30) as claimed in claim 4, wherein the perforated disk (19,22)includes a round periphery. 6. The radiation diaphragm (30)as claimed in claim 1, wherein each of the at least two radiation defining devices has positioning marks(21, 21',....,24,24',.. ) that are disposed so that the radiation defining device is positionable based on a position of the radiation defining device such that a respective diaphragm aperture is disposed in the x-ray beam. 7. The radiation diaphragm (30)as claimed in claim 6, wherein the positioning marks(21, 21',....,24,24',.. ) are disposed on a round periphery of the perforated disk(19,22). 8. The radiation diaphragm (30) as claimed in claim 7, wherein each of the at least two radiation defining devices is disposed so that the x-ray beam passes through one diaphragm aperture of each of the at least two radiation defining devices. 9. An x-ray facility (1) comprising: at least two radiation diaphragms that include a plurality of different diaphragm apertures (40...51, 60...66), the plurality of different diaphragm apertures (40...51, 60...66) operable to define a shaped beam in different contours, wherein each of the at least two radiation diaphragms is displaceable in a plane perpendicular to the shaped beam, wherein each of the at least two radiation diaphragms is operative to narrow an x-ray beam produced by an x-ray tube of the x-ray facility (1) to form the shaped beam and to mask out regions outside the shaped beam, wherein the at least two radiation diaphragms are mounted on different central axis supports, wherein the plurality of different diaphragm apertures (40...51, 60...66)) adjust the contour of the shaped beam, and wherein each diaphragm aperture of one of the at least two radiation diaphragms is disposable within the periphery of at least one diaphragm aperture of another of the at least two radiation diaphragms. 10. The x-ray facility (1) as claimed in claim 9, wherein each of the at least two radiation diaphragms includes a first perforated radiation defining device that includes at least one aperture, and a second perforated radiation defining device that includes at least one aperture, and wherein the first perforated radiation defining device and the second perforated radiation defining device are operative to be moved to provide different contours of the shaped beam. 11. The x-ray facility (1) as claimed in claim 10, comprising: a data processing facility (11) and a diaphragm memory (14)that includes data, wherein the data processing facility (11) has access to the diaphragm memory (14)and the diaphragm memory (14)data, the data processing facility (11) being operable to determine a position of at least one of the first perforated radiation defining device and the second perforated radiation defining device. 12. The x-ray facility (1) as claimed in claim 11, wherein the data processing facility (11) is connected to each of the at least two radiation diaphragms and is operable to control the positioning of at least one of the first perforated radiation defining device and the second perforated radiation defining device in a suitable position. 13. The x-ray facility (1) as claimed in claim 10, wherein the first perforated radiation defining device and the second perforated radiation defining device include a circular periphery. 14. The x-ray facility (1) as claimed in claim 11, wherein the data processing facility (11) is operable to determine the position based on the diaphragm memory (14)data. 15. The radiation diaphragm (30)as claimed in claim 1, wherein the plurality of different diaphragm apertures (40...51, 60...66)) comprises openings with different diameters. 16. The x-ray facility (1) as claimed in claim 9, wherein the plurality of different diaphragm apertures (40...51, 60...66)) comprises openings with different diameters. 17. The radiation diaphragm (30)as claimed in claim 14, wherein the first perforated radiation defining device and the second perforated radiation defining device have different aperture patterns. 18. The radiation diaphragm (30)as claimed in claim 1, wherein the plurality of different diaphragm apertures (40...51, 60...66)) are open spaces that do not contain any material.

Documents:

4856-DELNP-2007 Correspondence-Form-1(20.08.2014).pdf

4856-DELNP-2007 Petition under Rule 137(20.08..2014).pdf

4856-DELNP-2007-Abstract-(03-08-2012).pdf

4856-delnp-2007-abstract.pdf

4856-delnp-2007-Claims-(02-09-2014).pdf

4856-DELNP-2007-Claims-(03-08-2012).pdf

4856-delnp-2007-claims.pdf

4856-delnp-2007-correspondece-others.pdf

4856-delnp-2007-Correspondence Others-(02-09-2014).pdf

4856-DELNP-2007-Correspondence Others-(03-08-2012).pdf

4856-DELNP-2007-Correspondence(20.08.2014).pdf

4856-delnp-2007-correspondence-others 1.pdf

4856-delnp-2007-description (complete).pdf

4856-delnp-2007-drawings.pdf

4856-DELNP-2007-Form-1-(03-08-2012).pdf

4856-delnp-2007-form-1.pdf

4856-DELNP-2007-Form-13(20.08.2014).pdf

4856-delnp-2007-form-18.pdf

4856-DELNP-2007-Form-2-(03-08-2012).pdf

4856-delnp-2007-form-2.pdf

4856-delnp-2007-form-26.pdf

4856-DELNP-2007-Form-3-(03-08-2012).pdf

4856-delnp-2007-form-3.pdf

4856-delnp-2007-form-5.pdf

4856-delnp-2007-pct-304.pdf

4856-DELNP-2007-Petition-137-(03-08-2012).pdf

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