Patent ID: 12201466

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

With reference toFIG.1, a schematic view of a procedure room20is illustrated. A user24, such as a surgeon, can perform a procedure on a subject, such as a patient28. The subject may be placed on a support, such as a table32for a selected portion of the procedure. The table32may not interfere with image data acquisition with an imaging system36. In performing the procedure, the user12can use the imaging system36to acquire image data of the patient28to allow a selected system to generate or create images to assist in performing a procedure. Images generated with the image data, such as a model (such as a three-dimensional (3D) image), long views, single projections views, etc. can be generated using the image data and displayed as an image40on a display device44. The display device44can be part of and/or connected to a processor system48that includes an input device52, such as a keyboard, and a processor56, which can include one or more processors or microprocessors incorporated with the processing system48along with selected types of non-transitory and/or transitory memory58. A connection62can be provided between the processor56and the display device44for data communication to allow driving the display device44to display or illustrate the image40. The processor56may be any appropriate type of processor such as a general purpose processor that executes instructions included in a program or an application specific processor such as an application specific integrated circuit.

The imaging system36can include an O-Arm® imaging system sold by Medtronic Navigation, Inc. having a place of business in Louisville, CO, USA. The imaging system36, including the O-Arm® imaging system, or other appropriate imaging systems may be in use during a selected procedure, such as the imaging system described in U.S. Patent App. Pubs. 2012/0250822, 2012/0099772, and 2010/0290690, all incorporated herein by reference.

The imaging system36, when, for example, including the O-Arm® imaging system, may include a mobile cart60that includes a controller and/or control system64. The control system64may include a processor and/or processor system66(similar to the processor56) and a memory68(e.g. a non-transitory memory). The memory68may include various instructions that are executed by the processor66to control the imaging system36, including various portions of the imaging system36.

The imaging system36may include further addition portions, such as an imaging gantry70in which is positioned a source unit (also referred to as an assembly)74and a detector unit (also referred to as an assembly)78. The gantry70is moveably connected to the mobile cart60. The gantry70may be O-shaped or toroid shaped, wherein the gantry70is substantially annular and includes walls that form a volume in which the source unit74and detector78may move. The mobile cart60may also be moved, and can be moved from one operating theater to another and or another room. The gantry70can move relative to the cart60, as discussed further herein. This allows the imaging system36to be mobile and moveable relative to the subject28thus allowing it to be used in multiple locations and with multiple procedures without requiring a capital expenditure or space dedicated to a fixed imaging system.

The processor66may be a general purpose processor or a specific application processor. The memory system68may be a non-transitory memory such as a spinning disk or solid state non-volatile memory. In various embodiments, the memory system may include instructions to be executed by the processor66to perform functions and determine results, as discussed herein.

In various embodiments, the imaging system36may include an imaging system that acquires images and/or image data by the use of emitting x-rays and detecting interactions and/or attenuations of the x-rays with the subject28. Thus, x-ray imaging may be an imaging modality. It is understood that other imaging modalities are possible.

Thus, the imaging system36that includes the source unit74may be an x-ray emitter that can emit x-rays through the patient28to be detected by the detector78. As is understood by one skilled in the art, the x-rays emitted by the source74can be emitted in a cone90along a selected main vector94and detected by the detector78, as illustrated inFIG.2. The source74and the detector78may also be referred to together as a source/detector unit98, especially wherein the source74is generally diametrically opposed (e.g. 180 degrees apart) from the detector78within the gantry70.

The imaging system36may move, as a whole or in part, relative to the subject28. For example, the source74and the detector78can move in a 360° motion around the patient28. The movement of the source/detector unit98within the gantry70may allow the source74to remain generally 180° opposed (such as with a fixed inner gantry or rotor or moving system) to the detector78. Thus, the detector78may be referred to as moving around (e.g. in a circle or spiral) the subject28and it is understood that the source74is remaining opposed thereto, unless disclosed otherwise.

Also, the gantry70can move isometrically (also referred as “wag” relative to the subject28generally in the direction of arrow100around an axis102, such as through the cart60, as illustrated inFIG.1. The gantry34can also tilt relative to a long axis106of the patient28illustrated by arrows110. In tilting, a plane of the gantry70may tilt or form a non-orthogonal angle with the axis106of the subject28.

The gantry70may also move longitudinally in the direction of arrows114along the line106relative to the subject28and/or the cart60. Also, the cart60may move to move the gantry70. Further, the gantry70can move up and down generally in the direction of arrows118relative to the cart30and/or the subject28, generally transverse to the axis106and parallel with the axis102.

The movement of the imaging system60, in whole or in part is to allow for positioning of the source/detector unit (SDU)98relative to the subject28. The imaging device36can be precisely controlled to move the SDU98relative to the subject28to generate precise image data of the subject28. The imaging device36can be connected with the processor56via a connection120, which can include a wired or wireless connection or physical media transfer from the imaging system36to the processor56. Thus, image data collected with the imaging system36can be transferred to the processing system56for navigation, display, reconstruction, etc.

The source74, as discussed herein, may include one or more sources of x-rays for imaging the subject28. In various embodiments, the source74may include a single source that may be powered by more than one power source to generate and/or emit x-rays at different energy characteristics. Further, more than one x-ray source may be the source74that may be powered to emit x-rays with differing energy characteristics at selected times.

According to various embodiments, the imaging system36can be used with an un-navigated or navigated procedure. In a navigated procedure, a localizer and/or digitizer, including either or both of an optical localizer130and/or an electromagnetic localizer138can be used to generate a field and/or receive and/or send a signal within a navigation domain relative to the subject28. The navigated space or navigational domain relative to the subject28can be registered to the image40. Correlation, as understood in the art, is to allow registration of a navigation space defined within the navigational domain and an image space defined by the image40. A patient tracker or dynamic reference frame140can be connected to the subject28to allow for a dynamic registration and maintenance of registration of the subject28to the image40.

The patient tracking device or dynamic registration device140and an instrument144can then be tracked relative to the subject28to allow for a navigated procedure. The instrument144can include a tracking device, such as an optical tracking device148and/or an electromagnetic tracking device152to allow for tracking of the instrument144with either or both of the optical localizer130or the electromagnetic localizer138. A navigation/probe interface device158may have communications (e.g. wired or wireless) with the instrument144(e.g. via a communication line156), with the electromagnetic localizer138(e.g. via a communication line162), and/or the optical localizer60(e.g. via a communication line166). The interface158can also communicate with the processor56with a communication line168and may communicate information (e.g. signals) regarding the various items connected to the interface158. It will be understood that any of the communication lines can be wired, wireless, physical media transmission or movement, or any other appropriate communication. Nevertheless, the appropriate communication systems can be provided with the respective localizers to allow for tracking of the instrument144relative to the subject28to allow for illustration of a tracked location of the instrument144relative to the image40for performing a procedure.

One skilled in the art will understand that the instrument144may be any appropriate instrument, such as a ventricular or vascular stent, spinal implant, neurological stent or stimulator, ablation device, or the like. The instrument144can be an interventional instrument or can include or be an implantable device. Tracking the instrument144allows for viewing a location (including x,y,z position and orientation) of the instrument144relative to the subject28with use of the registered image40without direct viewing of the instrument144within the subject28.

Further, the imaging system36, such as the gantry70, can include an optical tracking device174and/or an electromagnetic tracking device178to be tracked with the respective optical localizer130and/or electromagnetic localizer138. Accordingly, the imaging device36can be tracked relative to the subject28as can the instrument144to allow for initial registration, automatic registration, or continued registration of the subject28relative to the image40. Registration and navigated procedures are discussed in the above incorporated U.S. Pat. No. 8,238,631, incorporated herein by reference. Upon registration and tracking of the instrument144, an icon180may be displayed relative to, including overlaid on, the image40.

With continuing reference toFIG.2, according to various embodiments, the source74can include a single x-ray tube assembly190that can be connected to a switch194that can interconnect a first power source198via a connection or power line200. As discussed above, X-rays can be emitted from the x-ray tube190generally in the cone shape90towards the detector78and generally in the direction from the x-ray tube190as indicated by arrow, beam arrow, beam or vector94. The switch194can switch power on or off to the tube190to emit x-rays of selected characteristics, as is understood by one skilled in the art. The vector94may be a central vector or ray within the cone90of x-rays. An x-ray beam may be emitted as the cone90or other appropriate geometry. The vector94may include a selected line or axis relevant for further interaction with the beam, such as with a filter member, as discussed further herein.

The subject28can be positioned within the x-ray cone94to allow for acquiring image data of the subject28based upon the emission of x-rays in the direction of vector94towards the detector78.

The x-ray tube190may be used to generate two dimension (2D) x-ray projections of the subject28, including selected portions of the subject28, or any area, region or volume of interest, in light of the x-rays impinging upon or being detected on a 2D or flat panel detector, as the detector78. The 2D x-ray projections can be reconstructed, as discussed herein, to generate and/or display three-dimensional (3D) volumetric models of the subject28, selected portion of the subject28, or any area, region or volume of interest. As discussed herein, the 2D x-ray projections can be image data acquired with the imaging system36, while the 3D volumetric models can be generated or model image data.

For reconstructing or forming the 3D volumetric image, appropriate algebraic techniques include Expectation maximization (EM), Ordered Subsets EM (OS-EM), Simultaneous Algebraic Reconstruction Technique (SART) and Total Variation Minimization (TVM), as generally understood by those skilled in the art. The application to perform a 3D volumetric reconstruction based on the 2D projections allows for efficient and complete volumetric reconstruction. Generally, an algebraic technique can include an iterative process to perform a reconstruction of the subject28for display as the image40. For example, a pure or theoretical image data projection, such as those based on or generated from an atlas or stylized model of a “theoretical” patient, can be iteratively changed until the theoretical projection images match the acquired 2D projection image data of the subject28. Then, the stylized model can be appropriately altered as the 3D volumetric reconstruction model of the acquired 2D projection image data of the selected subject28and can be used in a surgical intervention, such as navigation, diagnosis, or planning. The theoretical model can be associated with theoretical image data to construct the theoretical model. In this way, the model or the image data40can be built based upon image data acquired of the subject28with the imaging device36.

With continuing reference toFIG.2, the source74may include various elements or features that may be moved relative to the x-ray tube190. In various embodiments, for example, a collimator220may be positioned relative to the x-ray tube190to assist in forming the cone90relative to the subject28. The collimator220may include various features such as movable members that may assist in positioning one or more filters within the cone90of the x-rays prior to reaching the subject28. Further, as discussed further herein, various filters may be used to shape the x-ray beam, such as shaping the cone90, into a selected shape prior to reaching the subject28. In various embodiments, as discussed herein, the x-rays may be formed into a thin fan or plane to reach and pass through the subject28and be detected by the detector78.

Accordingly, the source74including the collimator220may include a filter assembly224. The filter assembly224may include one or more portions that allow for moving a filter relative to the x-ray tube190to shape and/or position the x-rays prior to reaching the subject28. For example, with reference toFIG.3, the filter assembly224may include a stage228. The stage228may be positioned relative to the x-ray tube190and may substantially block all x-rays and/or define an initiation of the cone90as the x-rays pass through a stage exposure opening232. The stage opening232may be an opening or passage through the stage228that allows x-rays to exit the x-ray tube190and form the cone90.

As illustrated inFIG.3, a filter holding assembly240may include a movable filter holder or ladder244. The filter ladder244may include one or more filter holding positions such as a first open position246, a first filter or solid filter member250, and a third or slot filter member260, as discussed further herein. The filter ladder244may move on one or more rails, such as a first rail264and a second rail266. The filter ladder244may be connected with one or more carrier members, such as a ladder car including a first carrier268that moves along the first rail264and a second carrier member270that moves along the second rail266. It is understood that opposite or opposing carrier members may also be provided to ensure smoothness and/or selected planar movement of the filter ladder244, therefore including a third carrier274and a fourth carrier276. The third and fourth carriers274,276may ride on the respective rails264,266as the first and second carriers268,270. Accordingly, the filter ladder244may generally move in the direction of the double headed arrow280to selectively position the open filter portion246, the solid filter portion250, or the slot filter portion260relative to the aperture or passage opening232to allow x-rays to form the beam90or otherwise impinge on the subject28, as discussed further herein. The filter assembly224may be used to augment an emission of x-rays from the x-ray tube190to assist in generating an image or image data of the subject28, as discussed further herein.

The filter carrier or filter ladder244may be moved by selected mechanisms, such as servos or drive motors that are associated with the respective carriers268,270,274,276, or other appropriate mechanisms. Moving the filter ladder244may be controlled by the user24, such as through manual input, and/or instructions provided to the imaging system26. For example, the control system64may execute selected instructions to move the filter carrier244in a selected manner. Further, the control system64may move the filter carrier244at a selected time based upon selected inputs, such as inputs from the user24, regarding selected images or image data to be acquired of the subject28. Accordingly, the filter assembly224may be controlled by the controller64and/or any other appropriate controller, such as the processor system48.

With reference toFIG.4A,FIG.4B, andFIG.4Cthe slot filter assembly260is illustrated in greater detail. The slot filter assembly260may include a filter assembly that is formed of one or more members. It is understood, however, that the slot filter assembly may be formed of a single member including only the slot filter body352, as discussed further herein. In various embodiments, the slot filter assembly260includes a slotted member or portion300that may be sandwiched between or placed between a first member or sheet304and a second member or sheet308. It is understood, however, that the slotted member is not placed between the first member304and the second member308. The first and second members304,308may both be placed on a single side and/or incorporated into a single member placed on a single side of the slotted member300. In various embodiments, however, the first and second members304,308are solid and assist in ensure that slots340,344,348(discussed further herein) remain free and clear of debris.

The first sheet304may be formed of a selected material, such as substantially pure aluminum (i.e. pure aluminum as generally available to one skilled in the art), aluminum alloy, or other appropriate aluminum material. The top member304may include a first or exterior side312and a bottom or contact side314. The two sides or surfaces312,314may be substantially planar. The bottom or second side314may contact a first side320of the slotted member300. The second side314may be adhered to the first side320, such as with a selected adhesive or bonding member, such as an adhesive transfer tape. The thickness, or distance between the first side312and the second side314may be about 0.01 inches (in) to about 0.05 in, including about 0.02 in (about 0.5 millimeters (mm)).

The second layer or member308may include a first surface324that may be an exterior surface and a second surface or interior surface326. The second surface326may contact a bottom or second surface330of the slotted member300. The second layer308, however, may include or be formed as a dual material construction formed of an aluminum portion309(formed of the same or similar aluminum materials as discussed above) and a copper portion310(e.g. substantially pure copper). In various embodiments, the first portion may be 0.5 mm thick 1100 series aluminum bonded to 0.1 mm 99% pure copper with a selected material, such as Scotch brand adhesive 924. The entire second layer, however, may have a thickness of about 0.01 inches (in) to about 0.05 in, including about 0.02 in (about 0.5 millimeters (mm)). The sheets304,308will generally have a parameter that is generally coextensive with edges of the slotted member300.

The slotted member300may include dimensions, as discussed further herein. The slotted member300may be formed of a selected material such as tungsten carbide having a selected amount of tungsten, such as about 90% minimum tungsten. In various embodiments, the tungsten carbide is ANSI grade C2 tungsten carbide. For example, the tungsten carbide may be TECHMET grade TMK-22 tungsten carbide having a about 94% tungsten carbide and 6% cobalt. In various embodiments, the grain size of the of the tungsten carbide component may be on the order or microns or sub-micron in size, for example about 0.5 micrometers to about 2 micrometers, and including about 1.0 micrometers to about 1.4 micrometers, and further including about 1.2 micrometers. The slotted member300further includes a selected number of slots or slits that are formed through the slotted member300, such as a first slot340, a second or middle slot344, and a third slot348. The slots340,344,348may be used to form selected x-ray beams, volumes, or areas, such as fans, when positioned over the aperture232of the stage228. As discussed above, and further herein, the slotted filter260may be used to generate or form a beam of x-rays relative to the subject28for collecting image data thereof.

Generally, the slotted filter260may be positioned such that the first sheet304is positioned away from the subject28and generally near the source of the x-rays (e.g. the x-ray tube190). Accordingly, the x-rays may generally pass through the slotted filter member assembly260generally in the direction of the vector or arrow94first engaging the first layer member304and finally engaging or passing through the second layer sheet308. Generally, the slotted member300will block all or substantially all of the x-rays that pass through the first sheet304save for the x-rays that pass through the slots340,344,348. Accordingly, x-rays that engage the detector78when passing through the slotted filter member260are limited to only those x-rays that pass through the slots340,344,348. It is understood, however, at noted above the members304,308may be placed in any appropriate manner relative to the slotted member300. Further, the materials selected for the first and second members304,308may assist in refining and/or selecting spectral content of the x-rays that pass through the filter assembly260.

The slot filter assembly260includes the slotted member300, as discussed above. As illustrated inFIGS.4B and4Cthe slotted member300includes various features including the slots340,344,348. The slotted filter300includes a main body or member352through which the slots340,344,348are formed. The main body352may have a selected thickness354, the thickness354may be about 0.01 in to about 1 in, including about 0.01 in to about 0.1 in, and further including about 0.07 in to about 0.1 in and further about 0.09 in (about 2.2 mm). It is understood that the thickness354of the main body352, either alone or in combination with the other filtered layers304,308, may be used to form or define the x-rays that pass through the filter assembly260. The main body352may include further dimensions for various purposes, however, these dimensions may be based upon the size of the aperture232, the size of the filter assembly224, or other appropriate constrictions. Nevertheless, in various embodiments, the main plate352may include a length dimension356between terminal ends of about 0.5 in to about 2 in, and including about 1.4 in (35 mm). A width dimension360may be about 0.1 in to about 2 in, and further including about 0.9 in (22 mm). The main plate352of the slot filter member300may include various configurations, such as chamfered or angled corners364that may form an angle of about 45 degrees relative to the ends of the main body352. Again, it is understood, that the filter assembly260may include various configuration for fitting in a selected imaging system, such as the imaging system36, and specific shapes of the exterior may be based upon configurations of the imaging system36. The thickness354, however, may be selected to ensure minimal or no x-ray radiation passes through the filter assembly260other than through the slots340,344,348.

With continuing reference toFIG.4AandFIG.4B, and particular reference toFIG.4C, the main slot filter body member352has a thickness354. The thickness354is defined by or between the two surfaces320and330. In various embodiments, the surface320may be a surface that is positioned closest to the source of the x-ray radiation while the second surface330is the surface positioned closest to the subject28. It is understood that the surfaces may also be referred to, respectively, as the top surface320and the bottom surface330. It is understood, however, that top and bottom are merely exemplary and not intended to define an absolute position of the filter body member352.

The filter body member352including the three slots includes the middle slot344and two edge slots340,348. Each of the slots are formed to between and through the two sides320,330, as discussed further herein. Each of the three slots may be formed through the member352in an appropriate manner, such as electrical-discharge machining or other appropriate tool (e.g. a router or punch). It is further understood that the slots may be forged or otherwise cut into the member352. Nevertheless, near or at the first surface320each of the three slots340,344,348are formed by two respective side walls each, for example the first slot340is formed between the side walls370and374; the second slot344is formed between the side walls378,382; and the third slot348is formed between the side walls386and390. It is understood, as illustrated inFIG.4C, that the side walls extend between two ends357and358of the member352. The side walls for each of the slots340,344,348are generally equal distances apart and substantially parallel along the length of the respective slots. Further, the slot walls are generally straight and parallel relative to one another. It is understood, however, that certain tooling cause various portions of the slots to be of a slightly different dimension, such as an entry or exit plunge cut to initiate or end the slot. However, each of the slots340,344,348are generally formed to have a dimension398of about 0.001 in to about 0.1 in, including about 0.009 in to about 0.03 in, and further including about 0.025 in to about 0.01 in, and further including about 0.02 in (about 0.5 mm). The width398of the slots340,344,348may be substantially identical for each of the slots is generally a dimension between the interior surfaces of the respective opposed walls of the respective slots.

The respective walls forming the respective slots at the first surface320may each have a center between the respective walls. For example the slot340may have a center line or axis400, the second slot344has a center axis404and the third slot348has a center axis408. Each of the axes400,404,408may be of a point that is at a center between the respective walls and substantially perpendicular to the surface320. The center points or axes400,404,408are generally or substantially perpendicular the surfaces320,330and may be spaced a selected distance apart such as a distance412. The distance412may be the same between each of the slots and may be about 0.01 in to about 1 in, and further about 0.1 in to about 4 in, and further about 0.318 in to about 0.322 in (8.0 mm to about 8.2 mm) apart. The distance412may be selected based upon various parameters, such as the size of the slot member352, the size of the aperture232in the filter stage228, or other appropriate considerations. Accordingly, the distance412may be selected based upon various parameters. It is understood, however, that the spacing412between the respective slots340,344,348may be a substantially precisely selected for various imaging gathering techniques and/or stitching, as discussed further herein.

The respective central axes400,404,408, as discussed above, are defined or may be defined by a point that is at a center between the respective walls at the first side320and substantially orthogonal to the first side320. The central or second slot344may have the side walls378,382that are substantially parallel with the central axis404and substantially perpendicular to the surface320. Accordingly, the central axis404may extend through the plate member352substantially parallel with the side walls378,382. The distance or width398, therefore, may be substantially split in half or divided by the central axis404.

The edge slots340and348, however, may have respective central axes420and424that extend substantially parallel to the respective side walls370,374and386,390and not perpendicular to the surface320. The central axes420,424may form an angle relative to the respective center point axis400,408. For example, the first slot340having the central axis420may form an angle428relative to the center point axis400. The angle428may be about 5 degrees to about 10 degrees and further about 6 degrees to about 8 degrees, and further about 7 degrees. The central axis424may also form an angle432relative to the center point axis408. The angle432may be about 5 degrees to about 10 degrees, and further about 6 degrees to about 8 degrees, and further about 7 degrees. Accordingly, the angles428,432may be substantially similar or identical as an internal angle between the respective central axes420,424and the center point axes400,408. The angles428,432may also be formed relative to either of the surfaces320,330as the center point axes are substantially perpendicular to both surfaces320,330.

The angles428,432may assist in allowing x-rays to pass from the source190, as schematically illustrated inFIG.4C, through the respective slots340,344,348without any or substantial distortion due to interaction with the respective side walls370,374,379,382,386,390. As illustrated inFIG.4Cand as discussed above, the x-rays may be emitted from the source tube190in substantially a cone shape. Accordingly, x-rays that travel substantially normal to the surface320will pass through the central slot344along the central axis404without substantial or any interaction with the side walls378,382. Also due to the respective angles428,432, the x-rays that are near an edge of the cone90may pass through the edge slots340,348without substantial interaction with the respective side walls370,374,386,390due to the respective angles428,432.

The slot filter member300of the slot filter assembly260, according to various embodiments, may allow for a formation of three x-ray fans or areas of x-rays including a first fan440, a second fan444, and a third fan448due to the respective slots340,344,348. The three fans are formed by the slot filter260, including the main member300, filter x-rays from the source190save for the area of the slots340,344,348. In other words, the slot filter260filters the x-rays from the source190and allows the x-rays to pass through the slots340,344,348to form the fans440,444,448. In various embodiments, the slot filter assembly260, such as the main body300, is a distance450from the source190. The distance450may be about 50 mm to about 100 mm, including about 60 mm to about 80 mm, further including about 68 mm to about 72 mm.

As discussed further herein, the three fans440,444,448allow for generation of selected image projections due to an imaging area on the detector78. Further, due to the angles428,432, as discussed above, the first and third fans440,448are not substantially distorted due to interaction of x-rays with the plate member352. It is further understood that the numbering of the slots340,344,348and the respective fans440,444,448is merely for clarity of the current discussion, and not intended to require any particular order. Further, it is understood, that the filter member352may include a selected number of slots, such as less than three or more than three and three is illustrated and discussed for the current disclosure. It is understood, however, that the three slots340,344,348allow for the generation of a long view in an efficient and fast manner, as discussed further herein. Including a selected different number of slots may allow for a generation of a different number of intermediate images as discussed herein, but is not required.

As discussed above, the slot filter assembly260may be used in the imaging system36to acquire images of the subject28. Returning reference toFIG.2, the SDU98may be moved around the subject28within the gantry70. It is understood that the SDU98may be moved in any appropriate manner, and that the imaging system36is exemplary. Nevertheless, in various embodiments, the SDU may be rotated from a first position to a second position, such as about 90 degrees apart. For example, as illustrated inFIG.2, a first position of the SDU98may include the source74directing the x-rays along the cone90for the detector78which may be generally an anterior to posterior (AN) orientation relative to the subject28. The SDU90may be rotated 90 degrees, such that the source is at a second source position74′ and the detector may be moved to a different position such as at a second detector position78′. The SDU98may be positioned at either or both of the positions and a line scan of the subject78may be formed.

The line scan may include moving the gantry70, including the SDU98, along the long axis106of the subject28which may also be referred to as a Z axis or Z direction of the imaging system36generally in the direction of the double headed arrow114, as illustrated inFIG.1. The detector78may, therefore, be moved in a linear direction substantially with movement only in the direction of the double headed arrow114along a Z axis. The acquired image data may be used to form a long film or long view of the subject28with the image data acquired at one or both of the positions of the detector78,78′ as illustrated inFIG.2. The use of a slot filter260may be used to generate a plurality of views along the Z axis, as discussed further herein.

As illustrated inFIG.4Cand with further reference toFIG.5AandFIG.5B, the slot filter assembly260may be used to form the three fans440,444,448that reach or have attenuations that are detected by the detector78. Each of the fans440,444,448directly or have attenuations that impinge or contact the detector78at a substantially narrow position or area. As illustrated inFIG.5B, the detector78may include a plurality of excitable or detector regions or portions460. The detector regions460may also be referred to as pixels and may relate to a single picture element (pixel) that is illustrated on the display44in the image40.

The entire cone90from the source74may have an area that would excite or impinge upon the entire surface of the detector78. However, the individual fans440,444,448generally impinge upon only a narrow band of the pixels460. It is understood that the number of pixels excited may include an entire width464of the detector78, but limited to only a selected length468of the detector. For example, the respective fans440,444,448may impinge upon, assuming that no object or subject is within the path of the x-rays (e.g. an air scan), about 10 about 100 pixels. The number of pixels excited in the dimension468on the detector78, however, may be augmented or adjusted depending upon the distance from the detector78of the filter assembly260, the width of the slots (340,344,348), or other appropriate considerations. Nevertheless, as illustrated inFIG.5AandFIG.5B, each of the respective fans440,444,448will impinge upon the detector78at a substantially narrow position and excite a length468of pixels that may be along a substantially entire width464of the detector78. The width of the slots398that causes the length of pixels468to be excited (e.g. generate image data) limits or eliminates parallax distortion within the image portion collected with the imaging system using the slot filter300, as discussed herein.

Further, as illustrated inFIG.5AandFIG.5B, the detector78may be impinged upon by the three fans440,444,448substantially simultaneously from a single position of the source tube190along the Z axis generally in the direction of the double headed arrow114. The detector78, therefore, may output three different images or image data for three different positions of the x-ray at each single position of the source tube190. Movement, of the source tube190of the source74generally in the direction of the double headed arrow114, however, may create a plurality of three views along the Z axis, as discussed further herein. Each of the fans440,444,448may be separated by a selected distance, which may also be an angular distance472.

The imaging system36may be used to generate images of the subject28, for various purposes. As discussed above, the images may be generated of the subject28for performing a procedure on the subject28, such as a spinal fusion and/or implants relative to or adjunct to a spinal fusion. In various embodiments, therefore, user24may evaluate the subject28by viewing and evaluating images of the subject28for determination of placement of selected implants, such as pedicle screws. Accordingly, the imaging system36may be used to acquire an image of the subject28. The image system36may be used to acquire one or a plurality of projections. As further discussed above, the detector78detects x-rays that pass through or are attenuated by the subject28. Generally, however, the detector78detects a single projection at a time. The imaging system36, including the control system64, either alone or in combination with the processor system48may generate a long film or long view of the subject28by accumulating (e.g. stitching) a plurality of projections of the subject28. In various embodiments, the imaging system36, therefore, may be operated to acquire a plurality of images.

Turning reference toFIG.6, a method500of acquiring images, such as a long view of the subject28, is illustrated. The method500may include or start in start block510. The method500may then include positioning of the subject28in block514. Positioning the subject28in block514may include positioning the subject28, which may be a human patient, on the support32relative to the imaging system36. Also, as discussed above, the imaging system36may be a mobile imaging system, thus positioning the subject28in block514may include moving the imaging system36relative to the subject28. In particular, positioning the subject28may include positioning the subject28relative to a center or isocenter of the imaging system36such as within the gantry70and between the source74and the detector78.

After positioning the subject28in block514, acquisition parameters may be set or input in block518. Inputting acquisition parameters may include the selected length of the view of the subject28, the resolution required or selected, specific movement parameters of the imaging system36, or other appropriate input parameters. For example, the user24may input a length or number of vertebrae to be imaged. The controller64may then determine an amount of movement, such as a length in the axial direction along the long axis106of the patient and the direction of the double headed arrow114. Further, the user24may select to acquire image data that may be reconstructed into a three-dimensional model, as discussed herein. Accordingly the user24, either manually or automatically with the control system64, or other appropriate control or processor system, may determine acquiring images of the subject28along at least the AP view and a lateral view to allow for reconstruction of a three-dimensional model. It may further be understood that only a selected two-dimensional view may be acquired or selected of the subject28and therefore only a single line scan may be acquired. It is further understood that the imaging system36may be used to acquire any appropriate type of image of the subject28and that a line scan for long view is merely exemplary. Nevertheless, a line scan may be acquired of the subject28by moving the SDU98in a generally linear manner or direction from a start point to an end point. In various embodiments, an AP view may be collected in a first direction along the arrow114and the SDU98may be rotated90degrees to collect a lateral view on a return path for the same length along the arrow114.

After setting acquisition parameters in block518, the projections of the subject are acquired in block522. The acquisition of the projections may include acquiring a slot or fan projection in a line scan of the subject28. The acquisition of the projections may include acquiring the three fan projections at a plurality of locations of the source and detector and the SDU98along the line path, such as along the longitudinal axis106of the subject28. The number of acquisitions may be selected based upon the quality desired or selected for the final long view, including insuring an appropriate focus, minimizing or eliminating distortions (e.g. edge distortions), or other appropriate considerations.

After the acquisition of the projections in block522, a reconstruction of a long view also referred to as a long film, is made in block526. The reconstruction of the long view may include various sub-steps and sub-algorithms, as discussed further herein, to form a selected reconstruction, such as long view of the subject28. The reconstruction may include various features such as ensuring an appropriate focus, iterating the plurality of projections, or the like. The plurality of projections may then be stitched together into a long view, either sequentially or to provide a plurality of long views, as discussed herein.

The long view may then be optionally saved in block530. Saving the long view in block530may be saving the long view in any appropriate memory, such as the imaging system memory68and/or the processing system memory58. It is understood that saving the long view is optional and is not required. The long view may then be displayed on a selected display device in block534, such as on the display device44. The image40may include the long view reconstructed in block536or include only the long view reconstructed in block526. The displaying of the image in block534, however, may also be used to illustrate the position of the instrument144, such as with the instrument icon or representation180that is discussed above.

The procedure500may then end in end block540. Ending in block540may include stopping operation of the imaging system36and allowing a procedure to continue, as discussed above. In various embodiments, the acquisition of the long view may be used for planning a procedure on the subject28, such as prior to a procedure or in an operating room made during an intermediate step of the procedure. Further the long view may be acquired for various purposes, such as conformation of a step of the procedure (e.g. placement of a first pedicle screw or other appropriate number of pedicle screws), or other steps. Accordingly, ending in block540may be ending the acquisition of projections and reconstruction of a long view for display and use by the user24, or other appropriate user.

With continuing reference toFIGS.1-6, and additional reference toFIG.7the reconstruction of the long view in block526, illustrated inFIG.6, may include various sub-steps and/or sub-portions as illustrated inFIG.7. Accordingly,FIG.7illustrate details of the reconstruction of the long view in block526and may be incorporated into the method500, discussed above. The method500, therefore, may include the sub-portions as illustrated inFIG.7.

With continuing reference toFIG.7, the reconstruction of the long view (also referred to herein as reconstructed long view) generally includes the portions or sub-portions, as illustrated in block526. It is understood that various features and steps may be included as instructions, such as with an algorithm, that are executed by one or more processor or processor systems. For example, the imaging system processor66and/or the processing system48having a processor56, may execute instructions to generate the long view based upon the plurality of acquired projections from block522. As discussed above, operation of the imaging system36may acquire the plurality of projections in block522, such as with the slot filter assembly260. Accordingly, the imaging system36may generate projections that are based upon x-rays detected by the detector78. Inputting the acquired projections in block550may initiate the reconstruction process526, as discussed above and herein, the input of projections from three slots is exemplary and more or less is possible.

The x-ray projections may be acquired at the detector78with each of the three slots that generate the respective fans440,444,448. With continuing reference toFIG.7, and additional reference toFIG.8each of the three fans440,444, and448will generate three separate series of images or projections560,564,568, respectively. Each of the series of projections includes a plurality of projections that are acquired substantially simultaneously. For example, the first series560may include a first image slice560ithat will be acquired at the same position of the SDU98as a first image564iand568iof each of the respective fans440,444,448. As the SDU98moves in the selected direction, such as along the axis106in the direction of the arrow114, a plurality of projections are acquired through each of the slots due to each of the fans440,444,448. Accordingly, three series560,564,568of projections are acquired due to movement of the imaging system36along a selected line scan. These series of projections560,564,568are the input projections in block550from each of the three slots. As discussed further herein, although each of the slots and the respective fans440,444,448are used to generate respective series of projections560,564,568, all of the image projections may be used to generate the long view that is reconstructed in block526. Accordingly, the input of the x-ray projections from all three slots in550may include input of all three series of projections560,564,568which may be analyzed or evaluated separately, in various portions of the reconstruction of526, and then combined to form the final long view, as discussed further herein. Each of the image slices for each of the series (e.g.560i,564i,and569i) generally and/or substantially are free of parallax distortion due at least in part to the width of the slot398and the corresponding length468excited on the detector. Thus, the slices may be clearer and have less error or distortion due to the slice width398.

The procedure526, further includes an input of a motion profile of the imaging system36in block578. The input of the motion profile of the imaging system in block578may include the distance traveled, time of distance traveled, distance between acquisition of projections, and other motion information regarding the imaging system36. The motion profile information may be used to determine and evaluate the relative positions of the projections for reconstruction, as discussed herein.

After the input of the x-ray projections from block550, a plane of focus may be set, such as arbitrarily, at a selected axis or line such as focus plane (fp)=0 in block 590. A fp=0 may be defined as the isocenter of the imaging system36. With continuing reference toFIG.7andFIG.8, the fp may be defined relative to a portion being imaged, such as a spine28sof the subject28. The FP=0 may be an arbitrary position and used to stitch together or put together the series of projections into selected intermediate images for each slot in block600.

The generation of the intermediate images at the selected FP may generate the intermediate images for each of the series560,564,568, as illustrated inFIG.8. Accordingly, a first intermediate image610may be generated based upon the first series of projections560. A second intermediate image614may be based upon the series of projections564and a third intermediate image618may be based upon the third series of projections568. Each of the intermediate images610,614,618may be stitched together using generally known techniques such as image blending, registration, and view manipulations. These may include blending various portions of images that are near matches (e.g. determined to be similar portions) to achieve continuity. Registration includes matching or identifying identical portions of two or more images. Manipulations allow for altering different images or portions thereof, as discussed herein.

The plurality of projections, also referred to as image data portions, in each of the series, such as the first series560, are taken at a selected rate as the SDU98moves relative to the subject28. As illustrated inFIG.8, the subject28may include the spine28s.As the SDU98moves, for example, the fan440is moved a selected distance, such as 1 centimeters (cm) per projection acquisition. Accordingly, each of the image projections, such as the image projection560i,may be the width on the detector of the fan440and a second image projection560iimay be 1 cm from the first image projection560iand also the width of the fan440on the detector78. A selected amount of overlap may occur between the two image projections560iand560iithat allows for stitching together into the intermediate projection or image610, as is generally known in the art. Each of the series of projections560,564,568(which may each include image data portions), therefore, may be stitched together at the respective focus plane to generate the intermediate images610,614,618. As discussed above, the focus plane may be initially set at 0 or arbitrarily set at 0 which is generally the isocenter of the imaging system36that acquired the plurality of projections560,564,568.

After the intermediate images are generated at the FP=0 for each slot in block600, a registration of the intermediate images for each slot and determine a translation d occurs in block680. With continuing reference toFIG.7and additional reference toFIG.9AandFIG.9B, the intermediate images are generated based upon the plurality of projections due to movement of the SDU98. As illustrated inFIG.9A, a schematic representation of a first movement or distance d1is illustrated. d1may be the d, discussed above. d1is the distance that the source74may move from a first position74ito a second position74ii. The slot filter260may also, therefore, move from a first position260ito a second position260ii. As illustrated inFIG.9A, the second fan444at the first position of the slot filter260iand the first fan440at the second position of the slot filter260iimay intersect or cross at a focus plane FP=1.

As illustrated inFIG.9B, the source74may move from the second position74iito a third position74iiiand respectively the slot filter may move from the second position260iito a third position260iii. In this movement, a distance d2may occur. The movement illustrated inFIG.9Bmay include the middle or second fan444and the first fan440intersect at a second focus plane FP=2. It is also understood that each of the other respective fans may also intersect at different positions, and the illustration of the two fans are merely exemplary and discussion of the other fans will not be repeated, but is understood by one skilled in the art.

The position of an intersection of the fans (i.e. a distance from the source tube190) at the point being imaged may depend upon the position of the object being imaged, such as the spine28s,from the source tube190. It is understood by one skilled in the art, the spine28smay not be a straight line or extend along a straight line that is substantially parallel to the long axis106of the subject28, even if an isocenter of the imaging system36moves along the axis106. Accordingly, the focus plane FP may move between different positions of the source74and the slot filter260, as illustrated inFIG.9AandFIG.9B. Thus, the first distance d1which may be different from the distance d2and may also alter the focus plane of the image or projections acquired with the imaging system36. Nevertheless, the first intermediate image generated in block600may assume that the focus plane is at the isocenter of the imaging system36.

With continuing reference toFIG.9Aand additional reference toFIG.9B, the first intermediate image610and the second intermediate image614are displayed. The intermediate images may include all of the intermediate images, including the intermediate images610,614,618and the discussion of only the first intermediate image610and the second intermediate image614is merely for clarity of the current discussion. Nevertheless, the intermediate images610and614may be registered to one another to determine or generate a registered image640.

The registered image640may include a first end644that is equal to a first end648of the first intermediate image610and a second end654that is equivalent to a second end660of the second intermediate image614. Accordingly, the registered image640may be a composite or overlay of the first intermediate image610and the second intermediate image614. In particular, an area of overlap664may be determined or identified between the first intermediate image610and the second intermediate image614. The overlap664may be identified such as through feature based registration, mutual information based registration, or other appropriate registration or image matching methods.

As illustrated inFIG.9B, the second intermediate image614has the second end660that is a distance668from a second end670of the first intermediate image610. The distance668may be used or be identified as the distance d of movement of the imaging system and may be used to alter or determine a plane of focus for each of the intermediate images, or a mutual plane of focus for the intermediate images. Accordingly, due to the registration image640that is determined by registering the first intermediate image610and the second intermediate image614the distance d may be determined in block680.

After determining the distance d, which may be a translation distance and is related to the slot filter spacing (e.g. distance412), focus plane and region of interest in the subject to be imaged (e.g. anatomical region of interest such as a specific vertebrae or spinous process of a vertebrae), in block680, an updated plane of focus FP including the distance d may be made in block684. The distance d, as illustrated inFIG.9B, may relate to a distance of an adjustment of distance to achieve an alignment of registered elements (e.g. a spinous process) between two or more intermediate images, such as image610and614to generate the registered image640. Also, the distance between slots, such as the distance412, may be used to determine the translation distance d to achieve the registered image640. The image portions acquired through different slots, even at the same location of the slot filter260, are at different positions along the subject.

The updated FP, based on the analysis discussed above, including the position of the portion of interest within the subject (e.g. anatomy of interest), may then be input or iterated to generate updated intermediate images with the updated FP in block690. The updated FP for the iteration to generate the updated image may account for a position of the subject or region of interest from the source74between two different intermediate images (e.g. image portions). The generation of the updated intermediate images may be substantially similar to the generation of the intermediate images in block600, except that the focus plane has been updated based upon the determined translation d. Thus the focus of the intermediate images may be increased or refined due to a determination of the focus plane in light of the translation of the images, as determined above as illustrated inFIG.9B. The generated updated images in block690may then be combined in the combining of intermediate images with a weighting function in block700. As discussed above and herein, including three intermediate images based on three slots is merely exemplary, and more or less may be allowed or used.

Prior to the generation of the combining in block700, however, a determination of whether further updated intermediate images may be made in block692. For example, at least two iterations may occur to determine if a selected minimum is reached. If a minimum is not reached, a further iteration may occur. Regardless of the determination, a decision of whether a further update of the fp may be made in block692. If an update is made, a YES path694may be followed and the fp place may be updated in block684and the process may iterate. If no further update is needed or selected, a NO path696may be followed to combine the three intermediate images in block700.

With continuing reference toFIG.7and additional reference toFIG.10, the intermediate images that are updated in block690may include the first updated intermediate image610u,a second updated intermediate image614u,and a third updated intermediate image618u.As discussed above, each of the three intermediate images610u,614u,and618umay then be combined to generate a first or initial long view or long film image704.

The generation or merging of the various intermediate images, such as each of the three intermediate images610u,614u,and618u,may include various steps and features. In various embodiments, an initial deformation of various features may be made when generating each of the three intermediate images610u,614u,and618u.As noted above, each of the three intermediate images610u,614u,and618umay be generated based on a plurality of projections. Thus, each of the three intermediate images610u,614u,and618umay include a similar or same feature (e.g. vertebrae). The amount of deformation to generate each of the three intermediate images610u,614u,and618umay be determined and used in further merging procedures.

According to various embodiments, a weighting function710may be used to assist in the combining of the updated intermediate images610u,614u,and618uto generate the initial long view image704. The weighting function710is graphically illustrated inFIG.10. A first weighting function for the first fan440willustrates that pixels or image portions may be weighted more for the left most portion of the long view due to the position of the fan440. The intermediate or central fan444may have the function444wthat will weight the pixels for the middle of the long view704more from the updated image614udue to the position of the fan444. Finally, the fan448may have the function448wto weight the pixels furthest to the right or at the end due to the position of the fan448in the long view704. It is understood that other appropriate stitching functions may be used to generate the initial long view704and that the weighting function710is merely exemplary. Further, a greater weight may be given to the selected intermediate image610u,614u,and618uthat has the least deformation when generating the long view. Further, selected deformations, such as geometric deformations, may be made when generating the long view.

In various embodiments, the initial long view704may be output as the long view or a long view in block720. The long view output in block720may be saved, such as saving the long view in block530and/or displayed in block532, as discussed above in the process500illustrated inFIG.6. In various embodiments, however, various normalizations and/or processing may be applied to the initial long view704prior to the output of the long view in block720such as for image enhancement and/or clarity.

With continuing reference toFIG.7, various procedures may be performed prior to the output of the final 2D long film or long view image in block720. After the combination of the three intermediate images with the weighting functions, various processing steps may be performed prior to displaying and/or saving the long view image. For example, applying an air normalization in block730and/or further post processing for visualization in block740.

The air normalization may account for or minimize effects of the slot filter assembly260. As illustrated inFIG.5AandFIG.5Bthe fan, for example the fan448, contacts or impinges upon the detector78in the length distance468. The distance468is a small portion of the detector78. Further, due to the narrow dimension of the fan448and, therefore, the small number of pixels contacted on the detector78, an image or pixel intensity may drop off quickly, such as in a gaussian fashion as illustrated inFIG.11, from a peak intensity pixel or point744.

The peak intensity744may be at a center of the fan448, such as the center of the distance468at a pixel or point on the detector78. Within five pixels from the center pixel (i.e. a width of 10 pixels, including the peak intensity pixel) an intensity drop off of about 25% (e.g. the 6thpixel away may have an intensity of about 75% of the peak intensity pixel744) may be observed in the pixels outside of the 10 pixels centered on the pixel with the peak intensity744. Within 10 pixels from the center pixel (i.e. a width of 20 pixels, including the peak intensity pixel) an intensity drop off of about 66% is observed (e.g. the 11th pixel away may have an intensity of about 33% of the peak intensity pixel744). Accordingly, a narrow band of pixels may include all or substantially all of the intensity due to the fan448. It is understood, that each of the other fans440,444may include or have the similar pixel intensity drop off.

A mask may be applied to assist in reduce the effect of the intensity drop-off. A mask that is 40 pixels wide may be applied to each image acquired with each of the slots to account for and eliminate those pixels that has substantially no intensity due to the narrow fan widths440,444,448. The images that are acquired are thereby normalized in a reconstruction, such as due to the combination of the intermediate images in block700, to reduce or eliminate the distortion that may otherwise be observed. For example, upon stitching a plurality of narrow images, such as the image460iwith the image460iiif the normalization does not occur, the edges of the image may be substantially light or have nearly no pixel intensity relative to center pixels. Without the mask and normalization. when stitched or combined, the combined image may have a “ripple effect” that may be viewed in a stitched image. The ripple effect may alternate between dark and light bands due to the changing pixel intensity over a plurality of stitched images where the amount of pixel intensity drop off is substantial over a narrow ban or width of pixels.

Further post processing for visualization may occur in block740. Various post processing can include any appropriate post processing to assist in visualization of the combined image from block700. In various embodiments for example, a normalization or histogram averaging (e.g. of pixel intensities) of the image may occur. For example, the final reconstruction may have the stitched pixel values divided by a cumulative pixel value to assist in reducing or minimizing great variations between high contrast and low contrast areas in the combined image from block700. Thus the image may be prepared for viewing with further post processing in block740. The post-processing can include, but is not limited to, enhancing of anatomical features, highlighting anatomical features (e.g. masking), sharpening edges, etc.

Accordingly, in light of the above, the imaging system36may be used to acquire a plurality of projections of the subject28. The plurality of the projections of the subject28may be acquired in a linear manner, such as in a first line scan in an AP (anterior to posterior) direction and a second line scan in a lateral direction. The plurality of projections may then be stitched or combined into a single long view or long film view of the subject28. Various intermediate steps, such as those discussed above, may be performed to assist in performing or generating the single long view. For example, a plurality of slots in a filter may be used to generate a plurality of intermediate images that are then finally stitched together to form the single long view. Nevertheless, the imaging system36may be used to generate a long view of the subject28.

Further each of the slots in the slot filter260may allow for the acquisition of a different “view” of the subject28during scanning of the subject28. For example, each of the three fans440,444,448acquire a projection at a single position of the SUD98. Accordingly, at each view the perspective of the subject28may be different. According to various known techniques, therefore, a three-dimensional model of the subject28may be reconstructed using the plurality of views of the subject28acquired even during the line scans of the subject. A line scan of the subject, as discussed above, may be a substantially linear movement, such as generally parallel with the long axis106of the subject28. Thus the SDU98may not rotate around the subject28during the acquisition of the linear scan. Nevertheless, the plurality of projections from the various perspectives may be used to reconstruct a three-dimensional model of the subject28using the single or two line scans (e.g. AP and lateral line scans). These plurality of projections from various perspectives may also be used to localize items or features in high-contrast objects, such as bony anatomy or implants. The localized position from each of the more than one slot projections may also be used to generated a three-dimensional model of the subject that is imaged. The different position in the plane determined in each of the projections may be used to generate the 3D model, as is understood in the art.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.

It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device.

In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).

Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.