APPARATUS AND METHOD FOR TISSUE BIOPSY
20230181176 · 2023-06-15
Inventors
Cpc classification
A61B10/0275
HUMAN NECESSITIES
A61B10/025
HUMAN NECESSITIES
A61B17/32053
HUMAN NECESSITIES
A61B2010/0208
HUMAN NECESSITIES
A61B90/30
HUMAN NECESSITIES
International classification
A61B10/02
HUMAN NECESSITIES
A61B90/30
HUMAN NECESSITIES
Abstract
Exemplary embodiments of an apparatus can be provided for obtaining portions or samples of tissue from a target region of a biological tissue. One or more needles can be provided that have a small internal diameter, e.g., about 1 mm or less, and the needles can be configured to extract the tissue portions when the needles are inserted into and withdrawn from the tissue. Windows and/or markings can be provided on the wall of the needles to facilitate access to the sample. The needles can be provided in an enclosure, and an actuator can be provided to direct the needles into the tissue and/or withdraw them. A plurality of tissue portions having known relative locations in the target region can be obtained, and extraction of the tissue portions can be well-tolerated by the tissue as compared with conventional punch biopsies or the like.
Claims
1-16. (canceled)
17. An apparatus for obtaining at least one portion of a biological tissue for analysis, comprising: an enclosure with a lower surface; a hollow needle mechanically coupled to the enclosure and configured to be at least partially inserted into the biological tissue, the hollow needle containing a central lumen, a distal end configured to facilitate extraction of a portion of the tissue within the central lumen when the hollow needle is withdrawn from the tissue, and a window in a wall thereof configured to facilitate access to and a direct visual observation of the tissue portion while the tissue is located within the lumen; and an actuating mechanism configured to protrude the distal portion of the hollow needle a predetermined and optionally adjustable distance beyond the lower surface of the enclosure and retract the distal portion back into the enclosure.
18. The apparatus of claim 17, wherein the central lumen has a diameter of less than about 2 mm.
19. The apparatus of claim 18, wherein the central lumen has a diameter of less than about 1 mm.
20. The apparatus of claim 19, wherein the central lumen has a diameter of less than about 0.5 mm.
21. The apparatus of claim 17, wherein the window is one of a plurality of windows.
22. The apparatus of claim 17, wherein the hollow needle includes a plurality of markings provided on a surface thereof.
23. The apparatus of claim 17, further comprising a substrate, wherein the hollow needle is coupled to the substrate, and wherein a position of the substrate is adjustable relative to a position of the hollow needle.
24. The apparatus of claim 23, wherein the hollow needle is removably coupled to the substrate.
25. The apparatus of claim 24, wherein the hollow needle is configured to be decoupled from the substrate without direct contact from an operator.
26. The apparatus of claim 23, wherein the hollow needle is one in an array of hollow needles arranged over the substrate.
27. The apparatus of claim 26, wherein the substrate is one of a square, circular, rectangular, ovoid, or triangular shape.
28. The apparatus of claim 26, wherein the array of hollow needles includes a non-uniform density throughout the array of needles.
29. The apparatus of claim 26, wherein a distance between adjacent hollow needles of the plurality of hollow needles is between about 1 mm and about 20 mm.
30. The apparatus of claim 17, wherein the hollow needle comprises an identifying characteristic of at least one of a color, a shape, or a size of the at least one needle.
31. The apparatus of claim 17, further comprising a covering arrangement adapted to cover at least a portion of a distal end of the enclosure, wherein the covering arrangement comprises at least one of a film, a cap, or a plug.
32. The apparatus of claim 17, further comprising a positioning arrangement configured to facilitate a placement of at least one portion of the apparatus over a particular location on a surface of the biological tissue, wherein the positioning arrangement comprises at least one of an optical lens, a prism, or an optical reflector.
33. The apparatus of claim 32, further comprising an illuminating arrangement adapted to direct light onto the surface of the biological tissue.
34. The apparatus of claim 17, wherein the hollow needle comprises at least one of a plastic, a polymer, an acrylic, or an epoxy.
35. The apparatus of claim 17, wherein the diameter of the central lumen is the same as that of a conventional hypodermic needle having a gauge size greater than 16 gauge.
36. The apparatus of claim 17, wherein the diameter of the central lumen is the same as that of a conventional hypodermic needle having a gauge size between 21 gauge and 25 gauge.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Further objects, features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying figures showing illustrative examples, results and/or features of the exemplary embodiments of the present invention, in which:
[0018]
[0019]
[0020]
[0021]
[0022] Throughout the drawings, the same reference numerals and characters, unless otherwise stated, are used to denote like features, elements, components, or portions of the illustrated embodiments. Moreover, while the present invention will now be described in detail with reference to the figures, it is done so in connection with the illustrative embodiments and is not limited by the particular embodiments illustrated in the figures. It is intended that changes and modifications can be made to the described embodiments without departing from the true scope and spirit of the present invention as defined by the appended claims.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0023] Exemplary embodiments of the present invention are directed to exemplary methods, devices, and apparatus for reliably removing small tissue samples in a punch biopsy procedure. For example, a cross-sectional view of an exemplary apparatus 100 for removing a tissue sample according to a first exemplary embodiment of the present invention is shown in
[0024] Walls of the exemplary needle 120 can be optionally be provided with one or more windows, holes, or openings 130 therethrough, as illustrated in
[0025] In yet further exemplary embodiments of the present invention, the exemplary apparatus 100 can optionally include a plurality of calibrated markings 150 spaced along the longitudinal direction of the needle 120. Such markings 150 can facilitate an identification of distances and/or depths in the tissue sample that can be observed through the openings 130. The markings 150 can also facilitate placement of the handle or substrate 140 at a particular location to provide a predetermined protrusion length of the needle 120 beyond the distal end of the handle or substrate 140, in exemplary embodiments where the position of the handle or substrate 140 relative to the needle 120 is adjustable.
[0026] The exemplary apparatus 100 can optionally include a handle or substrate 140 provided at a proximal portion of the needle 120. The handle or substrate 140 can facilitate holding and manipulation of the needle 120, e.g., by a user, and can be provided in various sizes and shapes. The handle or substrate 140 can also be removable from the needle 120 after the tissue sample has been obtained. Further, a distal end of the handle can be wider than the outside diameter of the needle 120, as shown in
[0027] In a further exemplary embodiment, the position of the handle or substrate 140 relative to the needle 120 can be adjustable. The handle or substrate 140 can be affixed to the needle 120 using, e.g., a friction fit, a conventional threaded coupling, a clamping mechanism, or the like. Such an adjustable arrangement can be used, for example, to vary or alter the length of the needle 120 projecting below the handle or substrate 140 for particular uses, e.g., to sample specific tissue structures or to obtain tissue samples down to a predetermined depth below the tissue surface. For example, a penetration depth of the needle 120 when the apparatus 100 is inserted into tissue to be sampled can be varied by varying the projection length. In further embodiments, a plurality of handles 140 having different lengths can be provided and affixed to a needle 120 having a particular size, where the choice of handle size can determine the protrusion length of the needle 120 beyond the distal end of the particular handle or substrate 140.
[0028] The length of the needle 120 protruding from the lower portion of the handle or substrate 140 can generally be, e.g., between about 1 mm and about 5 mm. This exemplary effective length of the needle 120 can be determined based on the intended use. For example, a shorter needle 120 having a length between about 1 and 3 mm can be used to obtain tissue samples from the epidermis or near the surface of skin tissue. Longer needle lengths can be provided to obtain tissue samples from structures located deeper below the surface of the tissue. For example, longer protrusion lengths can be provided in the exemplary apparatus 100, e.g., lengths greater than 5 mm. Tissue samples relatively close to the surface can be obtained with such longer needles 120 by inserting only a portion of the needle 120 into the tissue being sampled and then withdrawing it. An insertion depth can be determined, e.g., using the markings 150 and/or positions of the windows 130, if such optional features are provided on the apparatus 100.
[0029] A distal end 110 of the needle 120 can be sharpened and/or otherwise configured/structured to facilitate (i) a penetration of the needle 120 into the region of interest of the tissue, and (ii) a separation of the tissue sample from the surrounding tissue. For example, the distal end 110 of the needle 120 can be provided with a sharpened or tapered edge. According to certain exemplary embodiments, the distal end 110 of the needle 120 can be provided with a plurality of sharp points to facilitate an insertion of the needle 120 into the biological tissue and/or removal of the tissue sample when the needle 120 is withdrawn.
[0030] In an exemplary operation, the tissue region to be examined can be numbed, cooled, and/or partially or completely frozen using conventional procedures. The exemplary apparatus 100 can then be inserted into this tissue region, such that the distal end 110 of the needle 120 penetrates the tissue to a desired depth. In certain exemplary embodiments, this depth can correspond to a protrusion distance of the needle 120 beyond the distal end of the handle or substrate 140, as described herein. Alternatively, the insertion depth can be determined using the markings 150 and/or window locations 130, if either is present, as a guide.
[0031] The exemplary apparatus 100 can then be removed from the tissue such that the sample of the tissue to be analyzed is retained within the hollow needle 120. The exemplary apparatus 120 can be twisted slightly around the longitudinal axis thereof to facilitate an insertion into the tissue and/or the separation of the tissue sample from the surrounding tissue. The tissue sample can be held within the hollow center of the needle 120. Accordingly, the needle 120 can facilitate the protection and/or stabilization of the tissue sample enclosed therein, and can also maintain a known orientation of the tissue sample based on the direction in which the needle 120 was inserted into the surrounding tissue.
[0032] The tissue region to be sampled can be on or near the skin surface, in which case the tissue sample can be removed by inserting the exemplary apparatus 100 directly through the skin surface and then removing it. Biopsy samples from tissue regions located deeper within the body can be obtained by first providing an incision to access the tissue region, then inserting the exemplary apparatus 100 into this deeper tissue, and removing it to obtain the tissue sample.
[0033] According to one exemplary procedure according to the present invention, the exemplary apparatus 100 can be inserted into a region of the tissue to be analyzed, optionally twisted or rotated to facilitate insertion and/or separation of a tissue sample from the surrounding tissue, and then removed from the tissue such that a small tissue sample is retained within the distal portion of the needle 120. Such samples having a small diameter can be more easily separated from the surrounding tissue than the larger tissue samples, which have a larger area beneath them that can still remain attached to underlying tissue after the sides of the tissue sample are cut or separated. The depth of the tissue sample thus obtained can be easily selected and monitored using the markings 150 provided on the needle 120.
[0034] After the exemplary apparatus 100 is removed from the region of tissue, the needle 120 that includes the tissue sample therein can be placed in a small vial or sleeve that can include formaldehyde or another solution or liquid that can preserve and stabilize the tissue sample. The handle or substrate 140, if provided, can also be removed prior to placing the needle 120 into the vial. For example, the handle or substrate 140 can be attached to the needle 120 using a spring-loaded latch or the like. The apparatus 100 can be manipulated by holding the handle or substrate 140, and the needle 120 can then be released from the handle 120 and dropped into the vial without being handled directly. After the needle 120 containing the tissue sample is placed in the vial, the vial can be sealed and sent to a laboratory or other facility for analysis.
[0035] According to another exemplary embodiment of the present invention, an exemplary apparatus 200, illustrated in
[0036] For example, the actuating mechanism 220 can include a spring-loaded actuator or the like that can be configured or structured to extend the distal portion of the needle 120 into the tissue when activated. In a further exemplary embodiment of the present invention, the actuating mechanism 220 can include a plunger, piston, or the like. The actuating mechanism 220 can be manually activated, e.g., by applying a force to the plunger or piston, or to a trigger or switch coupled to the actuating mechanism 220. The needle 120 can be affixed or coupled directly to the actuating mechanism 220. In further embodiments, the needle 120 can be affixed directly to a substrate 140 (not shown in
[0037] The protrusion distance of the needle 120 beyond the lower surface of the enclosure 210 can be predetermined and optionally adjustable, such that the needle 120 penetrates a known distance into the tissue when the exemplary apparatus 200 is placed on the surface of the region of the tissue to be sampled and the actuating mechanism 220 is subsequently activated. For example, a threaded arrangement can be provided to affix or mechanically couple the needle 120 to the actuating mechanism 220 and/or to a first portion of the enclosure 210, such that the protrusion distance of the needle 120 can be adjusted by twisting the actuating mechanism 220 and/or the first portion of the enclosure 120 relative to a second portion of the enclosure. In further exemplary embodiments, the actuating mechanism 220 can include a plurality of stops that are configured to control the protrusion distance of the needle 120 beyond the lower portion of the enclosure 210, for example, when the actuating mechanism 220 is activated.
[0038] One or more markers can optionally be provided on the enclosure 210, the needle 120, and/or the actuating mechanism 220 in any of the exemplary embodiments described herein to facilitate the adjustment and/or control of the protrusion length of the needle 120 when the actuating mechanism 220 is activated.
[0039] In further exemplary embodiments, the actuating mechanism 220 can be adapted, configured and/or structured to retract the needle 120 back into the enclosure 210 after the needle 120 has been inserted into the tissue to be sampled. The distal end of the enclosure 210 can optionally be provided with a covering arrangement 215. The covering arrangement 215 can be, for example, a film, e.g., a sheet of foil, plastic, or another thin material that the needle 120 can easily penetrate when the needle 120 is advanced so it protrudes from the housing 210, e.g., when the actuating mechanism 220 is activated. In certain exemplary embodiments, the optional covering arrangement 215 can be a solid cap, a plug, or a stopper that is either fixed in place (e.g., adhered to the housing 210 or formed as a part thereof) or removable (e.g., affixed to the distal end of the enclosure 210 with screw threads, a frictional fitting, or the like). The covering arrangement 215 can be adapted to cover the retracted needle 120 within the enclosure 210, to secure the needle 120 within the enclosure 210, to seal the interior volume of the enclosure 210, to protect the tissue sample within the needle 120 from contamination, etc. The covering arrangement 215 can optionally be provided with a hole aligned with the needle 120 and located such that the needle 120 can pass through the hole when the needle is extended, e.g., when the actuating mechanism 220 is activated.
[0040] According to certain further exemplary embodiments of the present invention, a fluid can be provided in the enclosure 210 after the needle 120 containing a tissue sample is retracted. Such fluid can include a biological preservative or the like configured to preserve and/or prevent deterioration or degradation of the tissue sample. For example, the fluid can be provided in a vial (not shown) that is affixed to the enclosure 210 or in fluid communication with the interior volume of the enclosure 210. In still further exemplary embodiments, the actuating mechanism 220 can be configured and/or structured to eject the needle 120 containing the tissue sample into a vial containing such fluid or another such container, to facilitate preservation and transportation of the tissue sample, e.g., prior to analysis of the tissue sample in a remote facility.
[0041] According to another exemplary embodiment of the present invention, an optional positioning arrangement 230 can be provided on or proximal to the enclosure 210. The positioning arrangement 230 can facilitate a deployment of the needle 120 into a particular location of the tissue when the actuating mechanism 220 is activated. For example, the location where the tissue sample is to be obtained can be marked on the tissue surface by the user or practitioner using any conventional tissue marking technique. The positioning arrangement 230 can then be used to align the exemplary apparatus 200 with the tissue surface such that the needle 120 can enter the tissue at the marked location when the apparatus 200 is activated to propel the needle 120 into the tissue. Although the apparatus 200 is shown with such positioning arrangement 230 in
[0042] The exemplary positioning arrangement 230 can include one or more optical elements affixed to and/or formed as part of the enclosure 210. For example, the positioning arrangement 230 can include one or more lenses configured to facilitate the viewing of a portion of the surface of the tissue beneath the apparatus 200 when the apparatus 200 is placed on the surface of the tissue. The positioning arrangement 230 can further include one or more reflecting surfaces to facilitate such viewing of the surface of the tissue from different angles and/or positions. A set of crosshairs or the like can be provided in the positioning arrangement 230 to identify the precise location where the needle 120 will enter the tissue when the actuating mechanism 220 is activated.
[0043] In additional exemplary embodiments of the present invention, the positioning arrangement 230 can further include an illumination source to facilitate the viewing of the surface of the tissue beneath the apparatus 200. In some exemplary embodiments, at least a portion of the enclosure 210, e.g., a portion proximal to the distal end thereof, is formed using a transparent or translucent material to facilitate such viewing and/or to allow ambient light to illuminate the tissue surface beneath the distal end of the apparatus 200. The positioning arrangement 230 or a portion thereof can be provided as an assembly separate from the housing 210, e.g., an illumination source and/or one or more lenses or reflectors, which can be reused with a plurality of housings 210 and needles 120. The positioning arrangement 230 or a portion thereof can optionally be formed as part of the housing 210 or permanently affixed thereto.
[0044] In yet another exemplary embodiment of the invention, an apparatus 300 can be provided as shown in
[0045] In yet further embodiments, some of the needles 120 can be adjustably attached or affixed to the base 140, e.g., by a threaded coupling or screw arrangement, a friction fitting, a clamp, or the like as described above, which can facilitate variation of the protrusion length of the needles 120 below the lower surface of the base 140. The protrusion length of individual needles 120 can be separately adjustable, or this length may be adjustable simultaneously for all needles 120 in the apparatus 300. For example, at least two of the needles 120 in the exemplary apparatus 300 can have different protrusion lengths.
[0046] The apparatus 300 can include any number of needles 120, for example, between about 2 and 12 needles 120. Larger numbers of needles 120 can also be used in certain embodiments, e.g., between 2 and about 25 needles 120, or between 2 and about 100 needles 120. The number of needles 120 provided in the apparatus 300 can be determined based on the intended use. For example, if tissue samples are desired from a small structure such as a typical pigmented lesion or carcinoma, or a biological structure of indeterminate shape or inexact location, a smaller number of the needles 120, e.g., between about 2 and 12 needles 120, can be provided in the exemplary apparatus 300 to ensure that a portion of the structure would be present in at least one tissue sample removed by the needles 120. If it is desirable to determine a spatial variation in tissue characteristics or to obtain tissue samples from a diffuse structure such as, for example, from a lentigo maligna melanoma, an angioscarcoma, or a desmoplastic tumor, a larger number of the needles 120 can be provided to obtain more tissue samples when the exemplary apparatus 300 is applied to a target area of tissue. The apparatus 300 can include more than 12 needles 120 for certain uses, for example, up to about 30 needles 120, to obtain tissue samples from moderate-sized structures and/or provide a more detailed spatial sampling of the structure, or even up to about 100 needles 120. The apparatus 300 can be adapted such that the plurality of needles 120 are inserted substantially simultaneously into the biological tissue and/or simultaneously withdrawn therefrom.
[0047] The spacing and/or separation distance between the needles 120 in the exemplary apparatus 300 can be between about 1 mm and about 20 mm. The exemplary apparatus 300 having smaller separation distances between the needles 120 can be used, e.g., to obtain a plurality of tissue samples from a particular target area or a small biological structure. Larger separation distances can be provided to obtain tissue samples over a larger target area or from different portions of a larger biological structure. Needle separation distances greater than about 20 mm can also be provided in further exemplary embodiments of the present invention, e.g., for obtaining tissue samples over a very large target area or from a large biological structure, or to obtain a higher spatial density of tissue samples from a particular biological feature or portion thereof.
[0048] The width of the substrate 140, which can correspond to e.g., a side length or diameter for a substantially square or circular substrate 140, respectively, can be between about 3 mm and about 30 mm. Other substrate shapes can be provided in further exemplary embodiments of the invention such as, e.g., rectangular, ovoid, triangular, or the like. The exemplary shape of the substrate can be determined at least in part by characteristics of the target region of tissue and/or the biological structure from which tissue samples are to be taken from. A plurality of needles 120 can be provided in any one of various spacings or patterns over the substrate 120. For example, the needles 120 can be arranged in a regular square or triangular array. In other embodiments, the needles 120 can be spaced closer together in one portion of the substrate 140 than in another portion thereof, e.g., a non-uniform density of needles 120 can be provided. An apparatus 300 having such non-uniformity can be used, e.g., to obtain more tissue samples from a particular identified biological structure and fewer samples from proximal areas of tissue.
[0049] In further embodiments, one or more of the needles 120 in the exemplary apparatus 300 can be provided with one or more identifying characteristics, such as a distinct coloration, marking, shape, size or diameter, or the like. Such identifying characteristics can be used to assess the orientation of the needles 120 and tissue samples or portions contained therein, e.g., after the exemplary apparatus 300 is withdrawn from the tissue. The target region of tissue can optionally be labeled with one or more identifying markings. Such markings can facilitate identification of the orientation and/or location of the plurality of needles 120 and tissue samples they may contain, relative to the target region of tissue. The relative location of the tissue portions within the target region can be determined based on the relative locations of the needles 120 in the apparatus 300.
[0050]
[0051] The enclosure 210 can optionally include an actuating mechanism 220 configured to insert the needles 120 into the tissue to be sampled. The needles 120 can be coupled or affixed directly to the actuating mechanism 220, or they can be coupled or affixed directly to the handle or substrate 140, which can be further coupled to the actuating mechanism 220. The actuating mechanism 220 in the exemplary apparatus 400 can include any of the features that were described herein above with respect to the apparatus 200 shown in
[0052] The protrusion distances of the needles 120 beyond the lower surface of the enclosure 210 can be predetermined and optionally adjustable, such that the needles 120 penetrates a known distance into the tissue when the exemplary apparatus 400 is placed on the surface of the region of the tissue to be sampled and the actuating mechanism 220 is subsequently activated. Each of the needles 120 can be individually adjustable, and/or all of the needles 120 in the exemplary apparatus 400 can be adjustable simultaneously, using the exemplary arrangements and mechanisms described above with respect to the exemplary apparatus 200. In further exemplary embodiments, the exemplary apparatus 400 can be adapted, configured, and/or structured to retract the needles 120 back into the enclosure 210, similar to that described for the exemplary apparatus 200 herein.
[0053] The distal end of the enclosure 210 in the exemplary apparatus 400 can optionally be provided with the covering arrangement 215, e.g., a sheet of foil, plastic, or another thin material that the needles 120 can penetrate when they are advanced to protrude from the housing 210. In certain exemplary embodiments, the optional covering arrangement 215 can be a solid cap, plug or stopper that is removable (e.g., affixed to the distal end of the enclosure 210 with screw threads, a frictional fitting, or the like). The covering arrangement 215 can further be configured or structured to be placed over the distal end of the enclosure 210, e.g., to cover the retracted needles 120 within the enclosure 210, to secure the needles 120 within the enclosure 210, to seal the interior volume of the enclosure 210, to protect the tissue samples in the needles 120 from contamination, etc. The covering arrangement 215 can optionally include a plurality of small holes therethrough, e.g., where the diameter of the holes may be substantially the same as or slightly larger than the outside diameter of the corresponding needles 120. The holes can be located in the exemplary covering arrangement 215 such that the needles 120 can pass through the holes when the needles 120 are advanced and project from the enclosure 210, e.g., when the actuating mechanism 220 is activated.
[0054] The exemplary apparatus 400 can optionally include other features that are similar to or the same as those described for the exemplary apparatus 200 shown in
[0055] In any of the exemplary embodiments described herein and/or illustrated in
[0056] In further exemplary embodiments, the one or more needles 120 can be adapted to be fixed in an appropriate medium after tissue samples have been collected therein. The substrate 140 and/or enclosure 210, if provided, can be configured to facilitate such fixing, e.g., by providing a mold body or being adapted to attach to a mold. A embedding medium such as a paraffin or other wax, an acrylic, an epoxy, a resin, or a curable polymer, or any other conventional embedding medium can be used. Sectioning of the one or more needles 120 in the embedding medium can then be performed, e.g., using conventional sectioning techniques and devices. In further embodiments, at least a portion of the needle 120 can be formed using a material that is easily cut or abraded using conventional sectioning devices and systems. For example, at least a portion of the needle 120 can be formed using the same or a substantially similar material as a embedding medium that the needles 120 are fixed in. The needles 120 can be used to obtain and support tissue samples having small widths, and fixing the needles 120 in a medium and then sectioning and/or grinding them can provide accurate spatial identification of portions of the tissue samples during subsequent analysis.
[0057] The exemplary method and apparatus described herein can facilitate removal and stabilization of a small tissue sample using a small needle, and the handling and transfer of the small sample to an apparatus or remote facility for analysis. The exemplary apparatus 100/200/300/400 can also facilitate observation of, and access to, portions of the sample that are at a known depth and orientation relative to the surrounding tissue from which it was removed. The present invention thereby facilitates biopsy samples to be obtained and analyzed, where the tissue samples are smaller than those used in conventional biopsy procedures. The use of such smaller tissue samples can facilitate healing and avoid the removal of excess tissue and/or formation of scars or markings resulting from such removal.
[0058] The foregoing merely illustrates the principles of the invention. Other variations to the disclosed exemplary embodiments can be understood and effected by those skilled in the art in practising the claimed invention from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously. Any reference signs in the claims should not be construed as limiting the scope of the claims. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous techniques which, although not explicitly described herein, embody the principles of the invention and are thus within the spirit and scope of the present invention.