A Radiation Shield for use in a Radiotherapy Machine
A Radiation Shield for use in a Radiotherapy Machine
The radiation shield has a shell (22) of a first radiation opaque material such as lead containing discrete components (23) for example rods or spheres of a second radiation opaque material such as tungsten of higher density than the first radiation opaque material within a radiation opaque medium (24) of lower density than the discrete components (23). The shell or casing (22) is manufactured from a material which is easily worked and formed into different intricate or complex shapes while the discrete components 23 provide the required high degree of shielding.
Inventors:
Kublik, Tadeusz Jan (GB)
Application Number:
EP19930200317
Publication Date:
08/18/1993
Filing Date:
02/05/1993
Export Citation:
Assignee:
PHILIPS ELECTRONICS UK LTD (GB)
PHILIPS NV (NL)
International Classes:
A61N5/10; A61N5/10; G21F1/00; G21F1/12; G21F3/00; G21F3/00
European Classes:
G21F1/12; G21F3/00
View Patent Images:
Other References:
PATENT ABSTRACTS OF JAPAN vol. 3, no. 135 (E-150)10 November 1979 & JP-A-54 113 385 ( TOKYO SHIBAURA DENKI ) 4 September 1979
PATENT ABSTRACTS OF JAPAN vol. 14, no. 79 (E-888)(4022) 14 February 1990 & JP-A-01 292 767 ( KERU ) 27 November 1989
DATABASE WPI Week 7643, Derwent Publications Ltd., London, GB; AN 76-80172X & JP-A-51 101 706 (TOKYO SHIBAURA ELEC) 9 September 1976
Claims:
1. A radiation shield for use in a radiotherapy machine to shield against extraneous radiation, the radiation shield comprising a shell of a first radiation opaque material containing discrete components of a second radiation opaque material of higher density than the first radiation opaque material within a radiation opaque medium of lower density than the discrete components.
2. A radiation shield according to Claim 1, wherein the radiation opaque medium comprises lead.
3. A radiation shield according to Claim 1 or 2, wherein the second radiation material comprises tungsten.
4. A radiation shield according to Claim 1,2 or 3, wherein the discrete components comprise balls of the second radiation opaque material.
5. A radiation shield according to any one of Claims 1 to 4, wherein the discrete components comprise rods of the second radiation material.
6. A radiation shield according to any one of Claims 1 to 3, wherein the discrete components comprise at least one layer of rods of the second radiation material and at least one layer of balls of the second radiation material.
7. A radiation shield according to any one of the preceding claims, wherein the discrete components comprise shaped plates of the second material.
8. A radiation shield according to any one of the preceding claims, wherein the discrete components are coated with a coating material which is wettable by the radiation opaque medium.
9. A radiation shield according to any one of the preceding claims, wherein the radiation opaque medium comprises the same material as the shell.
10. A method of manufacturing a radiation shield for use in a radiotherapy machine to shield against extraneous radiation, which method comprises providing a shell of a first radiation opaque material, placing discrete components of a second radiation opaque material of higher density than the first radiation opaque material within the shell and then filling the shell with a radiation opaque medium of lower density than the discrete components.
Description:
This invention relates to a radiation shield for use in a radiotherapy machine and to a method of manufacturing such a radiation shield.
Radiotherapy machines provide collimated high energy beams of radiation, generally X-ray radiation, which are directed at precise target areas within the human body with the aim of destroying cancerous cells at the target area. Typically, a radiotherapy machine may provide an X-ray radiation beam with an energy of from, for example, 4 to 25 mega-electron volts (MeV).
Inevitably part of the radiation beam will be scattered by component parts of the machine and may leak out of the machine to impinge upon areas which it is not desired to irradiate. The accidental irradiation of otherwise healthy human tissue by such scattered radiation may result in secondary tumours. It is therefore extremely important that any areas of the radiotherapy machine from which such scattered radiation may leak are identified during manufacture of the machine and shielding provided to prevent such leakage.
In some areas radiation shields formed of a relatively low density (as compared to a relatively high density material such as tungsten) radiation opaque material such as lead which is relatively easily cast and machined to the required shape may be sufficient to prevent leakage.
However in other areas, especially those very close to the actual path of the direct beam, a relatively low density material such as lead will not provide adequate shielding. In such areas it is generally necessary to form the radiation shield of a high density material such as tungsten and normally a heavy metal tungsten alloy is used. Such high density materials are however extremely difficult to work and radiation shields formed of such materials are difficult to manufacture. In particular, tungsten has a very high melting point and the conventional sintering process by which the radiation shields are formed from tungsten powder can be very time-consuming and costly especially where large area shields are required.
In addition, tungsten is a very difficult material to machine so that the formation of the rather intricately shaped shields needed to fit around the functional components within the radiotherapy machine if the shields are to be placed close to the direct beam path is difficult and costly. This may result in the radiation shield having to be placed further from the direct beam path than is actually desirable so that the shield can have a more simple and more easily manufacturable shape.
It is an aim of the present invention to provide a radiation shield in which the above-mentioned problems are overcome or at least mitigated.
According to one aspect of the present invention, there is provided a radiation shield for use in a radiotherapy machine to shield against extraneous radiation, the radiation shield comprising a shell of a first radiation opaque material containing discrete components of a second radiation opaque material of higher density than the first radiation opaque material within a radiation opaque medium of lower density than the discrete components.
In another aspect of the present invention, there is provided a method of manufacturing a radiation shield for use in a radiotherapy machine to shield against extraneous radiation, which method comprises providing a shell of a first radiation opaque material, placing discrete components of a second radiation opaque material of higher density than the first radiation opaque material within the shell and then filling the shell with a radiation opaque medium of lower density than the discrete components.
As used herein, the term 'radiation opaque material' means a material which acts to block or absorb radiation such as high energy electrons or X-rays so that when such radiation is incident on one surface of the material it does not pass through the material.
The present invention thus provides a radiation shield having a shell or casing which can be manufactured from a radiation opaque material which is easily worked and which contains discrete components of a higher density radiation opaque material within a radiation opaque medium. For example, the shell may be formed of a material such as lead or a lead alloy, or where additional strength is required steel, which can be cast and/or machined relatively easily while the discrete components may be formed of a material such as tungsten which has a high density and is a much more effective radiation shield. A radiation shield which is a much more effective radiation shield than a lead shield yet which is much more easily manufactured than a tungsten shield can thus be obtained.
The radiation opaque medium may be lead or a lead alloy which takes the advantage of the low melting point of lead enabling the radiation opaque medium to be poured into the shell in a molten state. The use of lead containing about 4% by weight antimony is particularly advantageous because the shrinkage or contraction of the lead upon cooling is compensated for by the expansion of the antimony so that the volume of the radiation opaque medium is maintained as it cools from the molten state in which it is introduced into the shell.
The discrete components may be formed as balls, that is spheres or close approximations thereto, which have the advantage of packing closely together to provide a high radiation opacity while being able to fill complex and awkward shapes.
The discrete components may be formed as rods which may have the advantage, at the expense of the space-filling properties of balls, of making the overall shield more flexible and thus less susceptible to cracking. A combination of balls for space-filling and rods for improved flexability may be used. Thus, for example a layer of rods may be followed by one or more layers of balls.
The discrete components could also be formed as shaped plates which may be provided within the shell so as to form one larger complicated shape. Such shaped plates may be used in combination with rod or ball like discrete components and have the advantage of enabling a very high radiation capacity to be provided precisely where required. Two or more such shaped plates may be joined together within the shell to form a larger, possibly more complex,shape. For a given radiation opaque material, such relatively small shaped plates can be manufactured much more economically than large complex shaped one-piece radiation shields.
The discrete components may be coated with a coating material which is wettable by the radiation opaque medium so as to improve the coverage by the radiation opaque medium of the discrete components and thus improve the filling of the shell by the radiation opaque medium. Where the radiation opaque medium comprises lead or a lead alloy then the discrete components may be coated with a lead solder. Such a coating may also assist in locating the discrete components within the shell especially where the discrete components comprise rods or shaped plates.
The formation of the radiation opaque medium and the shell of lead where the discrete components are formed of tungsten may have an added advantage in that, in contrast to tungsten, lead has a very short radiation half-life and the lead will thus serve as shield for radiation which may be later emitted by the tungsten after it has been subjected to prolonged bombardment by the scattered radiation from the beam of the radiotherapy machine.
It should be noted that US-A-4825454 describes an X-ray imaging apparatus with a concentric collimator having concentric wall sections which may be made of tungsten, tantalum, depleted uranium or lead or compounds or mixtures of those elements while WO 89/02645 describes apparatus for slit radiography in which one or more elastic X-ray radiation absorbing strips formed of, for example, silicone rubber containing tungsten, lead or tantalum powder extend parallel to the slit and may carry absorption elements or plates which may be made of, for example, tungsten or formed of two small plates of, for example, tantalum and lead.
Neither document discloses or suggests a radiation shield which comprises a shell of a first radiation opaque material containing discrete components of a second radiation opaque material of higher density than the first radiation opaque material within a radiation opaque medium of lower density than the discrete components.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic simplified side view of a radiotherapy machine; Figure 2 is a schematic simplified part-sectional top view of part of the arm of the radiotherapy machine to show the location of some radiation shielding; Figure 3 is a schematic simplified part-sectional side view of the part shown in Figure 2; Figure 4 is a cross-sectional view of one example of a radiation shield in accordance with the invention; Figure 5a is a cross-sectional view similar to Figure 4 of a second example of a radiation shield in accordance with the invention; Figure 5b is a top plan view of a shell of the radiation shield shown in Figure 5a to show a stage in the manufacture of the radiation shield;
Figure 6 is a top plan view of the shell of a third example of a radiation shield illustrating a stage in the manufacture of the shield; Figure 7a is a cross-sectional view of a fourth example of a radiation shield in accordance with the invention; and Figure 7b is a cross-sectional view taken along the line 7-7 in Figure 7a.
It should of course be understood that the drawings, especially Figures 1 to 3, are much simplified and are not to scale. Like components are referred to by like reference numerals throughout.
Referring now to Figure 1, there is illustrated a very schematic side view of a radiotherapy machine 1.
As shown in Figures 1 to 3, the radiotherapy machine 1 comprises a gantry arm 2 mounted to a support 3 by a bearing system (not shown) so as to be rotatable through substantially 360 about a horizontal axis 4.
The gantry arm 2 houses and supports an electron source 5, a linear accelerator (LINAC) 6 which accelerates electrons along a waveguide 6a to an energy which is, typically, in the range 4 to 25MeV (Mega-electron volts), and a beam deflection system 7 incorporating deflection coils and bending magnets 7b for deflecting electrons travelling along a drift or flight tube 7a coupled to the output of the waveguide 6a of the LINAC 6 through an angle, which is in this case greater than 90 , so that the beam of electrons is directed normally of the axis 4 into a collimator head 8 carried by the free end of the gantry arm 2.
The linear accelerator 6 and deflection system 7 focus the electron beam substantially to a point focus onto an X-ray target mounted within the collimator head 8 from which is provided a high energy X-ray radiation collimated beam. In some circumstances, the X-ray target may be omitted so that the radiotherapy machine provides a high energy electron beam.
The patient 9 to be treated by the beam of radiation emitted by the collimator head 8 is supported on a patient table 10 and the entire machine 1 is precisely aligned in known manner using coordinates derived from earlier treatment planning and verification processes to position the target area 11 within the patient 9 precisely at the isocentre I so that maximum radiation is delivered to the target area 11 with minimum possible irradiation of surrounding healthy tissue.
There are many examples of commercially available radiotherapy machines which operate in the manner described above. One such example is the SL 25 manufactured by Philips Radiotherapy Systems at Crawley, England.
As indicated above, the radiotherapy machine 1 is set up with great precision for the particular patient to minimise irradiation of healthy tissue outside the target area 11 as this could cause secondary tumours or cancers. It is therefore important to ensure that there is no leakage of radiation from the radiotherapy machine 1 which could cause inadvertent radiation damage within the patient 9. Accordingly it is necessary to ensure that all areas within the radiotherapy machine 1, especially within the gantry arm 2 and the collimeter head 8 where radiation may be scattered from component parts of the machine, are adequately shielded with radiation opaque material to avoid such leakage.
Figures 2 and 3 are part-sectional views from the top and side respectively of part of the gantry arm 2 to illustrate some of the areas where radiation shielding is required. It will be appreciated that, in the interests of clarity and ease of understanding, these Figures are much simplified.
Figures 2 and 3 illustrate the end part of the accelerator tube or waveguide 6a of the LINAC 6. An outlet manifold 6b of the waveguide 6a is coupled to the drift tube 7a at the flange connection 12. The passageway for the electron beam decreases considerably in cross-section, typically from a 20cm diameter passageway within the accelerator tube 6a down to an 8cm slot in the drift tube 7a, at the flange connection 12. Accordingly, the potential for scattering of the electrons and thus leakage is very high around this area.
Figures 2 and 3 also show the vacuum pump pipe 13 leading from the outlet of the accelerator tube 6a to the vacuum pump (not shown). Where the LINAC 6 is of the travelling wave type, then the accelerator tube 6a also has an rf outlet pipe 14 which supplies the rf output power (via a connection which is not shown) either to an rf load or back to the inlet of the LINAC 6 in known manner. In addition to the components illustrated very schematically in Figures 2 and 3, the gantry arm 2 will incorporate various pieces of conventional mechanical and electrical machinery necessary for the functioning of the radiotherapy machine 1.
In order to provide the most effective shielding and to avoid unnecessary further scattering or spreading of the scattered electrons, the radiation shielding should be placed as close as possible to the sources of leakage which may be identified in known manner by covering the suspected areas with electron or X-ray sensitive photographic film as appropriate.
The main areas which require shielding to prevent leakage of radiation from the gantry arm are indicated by the blocks 20 which are shown hatched in Figures 2 and 3. As can be seen from the Figures, these areas include the area around the outlet manifold 6b and the area of maximum curvature of the flight tube 7a. In order to maximise the shielding effect, it is desirable for the radiation shielding to fit as closely as possible to the potential leakage areas. This requires, as can be seen from the very schematic views of Figures 2 and 3, that the radiation shielding 20 follow the curved surfaces and corners of, for example, the vacuum and rf outlet pipes 13 and 14 and most especially the outlet manifold flange connection 12.
Although the radiation shielding 20 is shown in Figures 2 and 3 as solid blocks in practice the radiation shielding will be formed of a number of separate radiation shields which are mounted to the housing 2a of the gantry arm 2 or other appropriate fittings within the gantry arm. Furthermore, in an actual radiotherapy machine such as the one mentioned above, the radiation shields have be able to fit into far more tortuous and intricate spaces than those shown in Figures 2 and 3. Thus, the radiation shielding has to be able to fit around and accommodate all the electrical and mechanical parts of the machine 1 not shown in Figures 1 to 3, including moving parts. It is therefore very often necessary that a radiation shield have a very complex curved shape to fit into a desired area.
Such complex shapes are very difficult to manufacture as solid blocks of a high density material such as tungsten.
Figures 4 to 7 illustrate various different examples of radiation shields 21 in accordance with the invention for use in the radiotherapy machine 1 shown in Figures 2 and 3. The radiation shields in each case comprise a shell 22 of a first radiation opaque material containing discrete components 23 of a second radiation opaque material of higher density than the first radiation opaque material within a radiation opaque medium 24 of lower density than the discrete components 23.
A radiation shield 21 in accordance with the invention thus has a shell or casing 22 which can be manufactured from a radiation opaque material which is easily worked and thus easily formed into the required different intricate or complex shapes. The required high degree of shielding is provided by the discrete components 23 within the shell 22 which do not, however, need to be manufactured in the intricate shapes required if the shield 21 is to fit closely to the area of leakage. Thus good shielding materials with high densities such as tungsten can be used without the need for the difficult and time-consuming processing which would be required to manufacture the radiation shield from a single solid piece of tungsten.
In the examples to be illustrated below with reference to Figures 4 to 7, the discrete components 23 are formed of tungsten while the shell is formed of lead and the radiation opaque material is also lead or a lead alloy. The tungsten discrete components 23 may be formed of pure (99%) tungsten which has a density of 19 gcm <-> <3> or, where the strength properties of the discrete components 23 are important a heavy metal alloy of tungsten, generally tungsten containing one or more of nickel, iron and copper, which has a density of 17.8-18.0 gcm <-> <3>. The radiation opaque material 24 may be provided by lead containing about 4% antimony.
The use of such a material has advantages in that the contraction of lead on cooling from the molten to the solid state is compensated for by the expansion of the antimony so that the volume of the radiation opaque medium 24 remains substantially constant.
In each of the examples shown in Figures 4 to 7, the shell 22 is first cast using a conventional lead casting process to the required shape although a certain amount of machining may be required later. Where as shown in Figure 4, mounting connection holes 26 such as bolt holes are required in the shell to enable the shield 21 to be mounted to part of the radiotherapy machine 1, these may be formed in conventional manner by casting the shell 22 to define pillars 27 extending within the space defined by the shell 22 and each having a mounting hole 26 extending therethrough. Alternatively or additionally such mounting or connection holes may be drilled after completion of the shield 21 or the shell 22 may have outer flanges (see Figure 7) which provide mounting holes.
The discrete components 23 are then placed in the shell 22. The discrete components 23 may be coated beforehand by a coating material which is wettable by the lead-antimony alloy. Typically, the coating material may be a lead or silver solder and may be applied simply by passing the discrete components through a solder bath. The coating material serves to ensure that the possibility of voids in the radiation opaque medium 24 is reduced to a minimum and may also enable the discrete components to adhere to the shell 22.
After the discrete components 23 have been placed within the shell 22, the lead-antimony alloy 24, which has been heated so as to become molten (approximately 350 C (degrees Celsius)), is poured into the shell 22 to cover the discrete components 23. Depending upon the desired shield construction this step may completely fill the shell 22. Where the shell 22 is filled then the radiation shield 21 is completed and, after cooling, any final machining of the easily worked lead shell 22 can be carried out. Alternatively if the shell 22 is not filled, then the above process may be repeated, for example using different shaped discrete components 23, until the shell 22 is filled.
The formation of the radiation opaque medium 24 and the shell 22 of lead where the discrete components are formed of tungsten has an added advantage in that, in contrast to tungsten, lead has a very short radiation half-life and the lead will thus serve as shield for radiation which may be later emitted by the tungsten after it has been subjected to prolonged bombardment by the scattered radiation from the beam of the radiotherapy machine.
In the example illustrated in Figure 4, the shell 22 is generally rectangular in cross-section and has walls 22' of generally uniform thickness, the inner periphery of the shell 22 being illustrated by the dashed line 30 in Figure 4. The shell 22 may be cast to have any desired shape when viewed in plan that is when looking down one of the major surfaces 21' of the shield. The precise final shape of the shield 21 may be obtained by machining of the outer surface of the easily workable lead shell 22 either before or after the shell 22 has been filled. The discrete components are formed as balls 23a of pure tungsten which are generally spherical and which are placed in the shell 22 so as to adopt a close-packed arrangement.
The balls 23a may have a diameter of about 3mm and typically a radiation shield 21 manufactured using this form of discrete component may have an average density of about 16 gcm <-> <3> for an overall thickness of about 40mm. The average density will however depend on the particular thickness of the shield 21 and will increase with thickness because the proportion of tungsten in the shield 21 increases with the thickness of the shield. In the interests of simplicity only some of the balls 23a are shown in Figure 4, although the area indicated by the reference numeral 31 will also be filled with balls 23a. Also, in the interests of clarity those balls 23a which are actually shown are not cross-hatched.
The use of the balls 23a as shown in Figure 4 has the advantage that the balls will pack closely together to fill almost any desired shape or space.
Figures 5a and 5b illustrate another example of a radiation shield 21a in accordance with the invention. Figure 5a is a cross-sectional view similar to Figure 4 while Figure 5b shows a top plan view of the shell 22 (shown, in the interests of simplicity only, as being rectangular in shape in the plan view) at a stage during the manufacture of the shield 21a.
In this example, two types of discrete components 23 are used. Thus, first, as shown in Figure 5b, a layer of tungsten rods 23b is provided within the shell 22 so that the rods 23b extend parallel to one another and along almost the entirety of one dimension of the shell 22. The rods 23b may have any desired cross-section but a circular cross-section may be preferred for ease of manufacture and packing within the shell 22. A thin layer 24a of the lead-antimony alloy or of a suitable lead solder may be provided within the shell prior to the tungsten rods 23b to facilitate adhesion to the shell 22. Desirably, the tungsten rods 23b are coated with a coating material such as a lead solder which is wettable by the lead-antimony alloy 24.
One or more layers of tungsten balls 23a are then provided, as shown in Figure 5a, on top of the layer of tungsten rods 23b and the shell 22 then filled with the molten lead antimony alloy 24. When the alloy 24 has cooled, the radiation shield 21a is complete and any final machining of the easily worked lead shell or casing 22 may then be carried out.
In this example the tungsten rods 23b serve to provide the radiation shield 21a with a degree of flexibility and thus should reduce the possibility of stress fractures during use. It may be desirable to form at least the tungsten rods 23b from heavy metal tungsten so as to reduce the possibility of cracking of the rods 23b during use of the shield.
As an alternative to providing layers of balls 23a over the layer of rods 23b, further layers of rods 23b with the rods of each layer extending transversely of those of the adjacent layers may be used. Of course, alternate layers of rods 23b and balls 23a may be used.
Figure 6 is a top plan view, similar to Figure 5b, of a shell 22a during a stage of the manufacture of another example of a radiation shield 21b in accordance with the invention.
In the example illustrated in Figure 6, the shell 22a is cast and/or machined in a particularly intricate shape and the discrete components are each shaped tungsten plates 23c which are arranged next to one another. In the example shown, the plates 23c overlap slightly and are joined by a suitable solder, for example a silver solder. Alternatively several layers of plates 23c may be provided and arranged so that the abutting edges or joins in successive layers are staggered so as not to be directly on top of one another. The plates 23c may each have a relatively simple, for example as shown rectangular, shape but can be joined together to form a relatively complex shape as shown in Figure 6.
The relatively small simple-shape plates 23a can be formed at relatively low cost compared to a single one-piece tungsten slab having the intricate dimensions of the composite formed by the plates 23c.
The plates 23c may, as in the previous examples, be coated with the coating material and a layer 24a of suitable solder or the lead antimony alloy may be provided within the shell 22 before the plates 23c to improve adhesion. In addition locating pins 25, for example tungsten pins, may be moulded into the shell 22 during casting to ensure accurate location of the plates 23c with respect to shell 22. The example illustrated in Figure 6 may be particularly advantageous where a very high shielding effect is required and where the shape of the area to be shielded and the space within which the radiation shield has to fit has a shape which is far too complex for it to be economical to use a single one-piece or solid tungsten radiation shield.
Figures 7a and 7b illustrate an example of a radiation shield 21c in which the shell 22b does not have walls of constant thickness but is shaped to provide a particular outer peripheral shape for the shell 22b and a different inner shape for the area 23' within the shell 22b occupied by the discrete components 23. This area 23' is shown merely cross-hatched in Figure 7a but may be occupied by balls 23a (shown unhatched in Figure 7b) or any one or more of the types described above. In this case, the shell 22b surrounding the area 23' not only provides mounting holes 26 outside the area 23' but also provides some radiation shielding surrounding the area 23'. Such a radiation shield 21c may be useful where there is a particularly high radiation leakage from one region, that is the area 23', and a much lower yet still significant leakage from a surrounding area 22b.
The radiation shields 21 described above may be used in any appropriate location, for example, within or on the gantry arm 2, of the radiotherapy machine and may be easily cast so as to have the required intricate shape. In addition such radiation shields may be used to form at least part of the beam-shape or aperture defining diaphragms in the collimator head 8, for example to form at least part of the leaves of a multi-leaf collimator head.
Furthermore, as indicated in Figures 2 and 3, the body of the gantry arm 2 may, at least adjacent the parts where the possibility of radiation leakage is high as discussed above, be hollow and may itself form the shell 22'' of a radiation shield which is provided simply by pouring the discrete components, preferably tungsten balls 23, into the cavity 2b and then filling the cavity with the lead-antimony alloy 24. This arrangement may avoid or at least reduce the need for radiation shielding which would otherwise have to be specially designed to fit and then mounted to the outside of the gantry arm 2.
In addition to tungsten other high density, radiation opaque materials such as osmium or tantalum may be used and other suitable relatively low melting point radiation opaque materials may be used in place of the lead antimony alloy. Furthermore, the shell 22 could be formed from a material other than lead and, for example, where strength is an important characteristic the shell 22 may be machined from a suitable steel.
A radiation shield in accordance with the invention may be used with other radiation emitting devices in addition to radiotherapy machines, especially those devices where there is a need for radiation shielding which can be formed in intricate or complex shapes to fit in and around electrical and mechanical components, including moving parts, of the device.
From reading the present disclosure, other modifications and variations will be apparent to persons skilled in the art. Such modifications and variations may involve other features which are already known in the art and which may be used instead of or in addition to features already described herein. Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present application also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention.
The applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.
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