Flexible tether with integrated sensors for dynamic instrument tracking

A system and method are provided for tracking a functional part of an instrument during an interventional procedure and displaying dynamic imaging corresponding to a functional part of the instrument. The system comprises: at least one instrument; a system for acquiring anatomical images relevant to guiding the instrument; a tether connected to the imaging system at a fixed end and connected to the instrument at a distal end, the tether comprising at least one longitudinal optical fiber with a plurality of optical shape sensors; an optical console that interrogates the sensors and detects reflected light; and a processor that calculates local curvature at each sensor location to determine the three-dimensional shape of the tether and determines the location and orientation of the instrument relative to the images using the local curvatures of the tether and the location of the fixed end of the tether.

The invention relates to the field of medical imaging and more particularly to tracking a functional part of an instrument and providing dynamic imaging corresponding to the functional part of the instrument.

Imaging systems are increasingly used to guide instruments during intervention procedures. In current practice, volumetric imaging performed with modalities such as Magnetic Resonance Imaging (MRI), Computed Tomography (CT), or XperCT (e.g. live fluoroscopy images co-registered with flat detector CT images) can be used to identify the locations of tissue targets prior to a procedure and to identify sensitive tissues surrounding the targets in order to minimize complications resulting from collateral tissue damage. These image volumes may be acquired with different modalities than those used to guide instruments used in a procedure in real-time. For example, CT may be used for pre-procedural imaging, and ultrasound may be used for real-time image guidance.

Accurate localization of the functional parts of instruments (for instance the blade of a scalpel) relative to structures that were identified on pre-procedural images is critical to physicians. Often there is limited information available for real-time image guidance. The available information may be limited because the use of imaging techniques is kept to a minimum (e.g. to reduce patient exposure to ionizing radiation when using x-ray fluoroscopy). The available information also may be limited due to inherent limitations of the imaging technique (e.g. lack of contrast for some lesions on ultrasound). Therefore, physicians often experience uncertainties about the locations of the instruments relative to the anatomy revealed by the image volumes. These uncertainties can result in increased patient risks as well as elevated procedural costs.

A number of marker-based approaches for instrument tracking have been proposed. One such marker-based approach is optical tracking. In optical tracking, markers are placed on an instrument in such a way that they are visible with optical detectors. In this method, objects that block, obscure, or otherwise limit the field-of-view and line-of-sight of the detectors can disable the algorithm or degrade its tracking performance.

Another marker-based approach is electromagnetic (EM) guidance. This method requires placing EM sensors on the instrument. While line-of-sight problems encountered with optical tracking do not apply to this method, tracking accuracy and precision can be degraded by external EM fields due to spatiotemporal variations in the EM environment.

In both of the above-mentioned marker-based tracking approaches, the position of the markers must be registered to the coordinate system of the image volumes. Errors can arise in cases where there are mis-registrations between these coordinate systems. Mis-registrations can arise when the EM system moves slightly within the room, for example.

Another approach is the use of optical shape sensing to determine the shape of an elongated flexible instrument, such as a catheter within an anatomical structure. Optical shape sensing in this context refers to the delivery of light to optical fiber cores positioned in the instrument and the collection of light from optical fiber cores positioned in the instrument; signals pertaining to collected light are processed to infer the shape or aspects of the shape of the instrument or aspects of the shape of this instrument. Optical shape sensing can involve backscattering from Fiber Bragg Gratings (“FBGs”) as well as Rayleigh scatterers in the cores or cladding of optical fibers, for instance. This shape sensing is described in conjunction with a marker-based approach. In this approach, a marker is placed on the instrument for tracking the instrument's location and optical shape sensing is used to determine the shape of the instrument within an anatomical structure.

A system and method are provided for tracking a functional part of an instrument during an intervention procedure by determining the three-dimensional shape of a tether connecting the instrument to an imaging system, and displaying dynamic imaging corresponding to the functional part of the instrument.

According to one embodiment the system comprises: at least one instrument; a system for acquiring anatomical images relevant to guiding the instrument; a tether connected to the imaging system at a fixed end, connected to the instrument at a distal end, and comprising at least one longitudinal optical fiber with a plurality of optical sensors comprising optical fiber cores with scattering sources such as Fiber Bragg Gratings or Rayleigh scatterers; an optical console that interrogates the sensors and detects reflected light, and a processor that calculates local curvature along the lengths of the sensors to determine the three-dimensional shape of the tether and determines the location and orientation of the instrument relative to the images using the three-dimensional shape of the tether and the location of the fixed end of the tether. In one embodiment there are four fiber cores with one fiber core on-axis and the others arranged in a helical fashion around the on-axis fiber core. Although the invention is discussed herein with regard to FBGs, it is understood to include fiber optics for shape sensing or localization generally, including, for example, with or without the presence of FBGs or other optics, sensing or localization from detection of variation in one or more sections in a fiber using back scattering, optical fiber force sensing, fiber location sensors or Rayleigh scattering.

According to one embodiment the imaging system constructs a three-dimensional image space and displays an appropriate view of the image space for the instrument, showing the functional part of the instrument in the image space.

In one embodiment the instrument is selected from a plurality of instruments. In this embodiment, the system further comprises an instrument identification unit identifying a selected one of the plurality of instruments. The identification unit may be an RFID receiver, wherein an RFID transmitter identifying the instrument is disposed on the instrument or on packing for the instrument. Alternatively, the identification unit may be a bar code reader, wherein a bar code identifying the instrument is disposed on the instrument or on packing for the instrument. According to another alternative embodiment, the identification unit is an electrical sensor and an electrical signal identifying the instrument is provided by the instrument or by packaging for the instrument. In yet another alternative embodiment the identification unit is a keypad for manual entry of an identification indication.

According to one embodiment the processor is an image processor of the imaging system.

According to one embodiment the instrument is removably connected to the distal end of the tether by a mechanical connection, such as a collar or threaded engagement. Alternatively, the instrument may be removably connected to the distal end of the tether by a magnetic connection or an adhesive.

The imaging system may be an XperCT system, wherein the tether is connected to a C-arm body of the XperCT system. Alternatively, the imaging system may be a combined X-ray breast mammography and biopsy system, wherein the tether is connected to an X-ray source, an X-ray detector, or a biopsy system.

According to one embodiment at least two tethers are connected to the imaging system. This allows for tracking two instruments simultaneously.

According to one embodiment, at least one marker is disposed on the tether or on the instrument to provide real-time reference points for calculating the shape of the tether.

The marker may be a radio-opaque marker. Alternatively, the marker may be an electromagnetic or optical marker. The optical fiber cores are integrated in the tether. Preferably there are four optical fiber cores, with one fiber core on-axis and the others arranged in a helical fashion around the on-axis fiber core. It should be noted that the four cores could either be contained within a single fiber (thereby sharing the cladding) or in separate fibers mechanically connected (e.g. glued).

According to one embodiment a method is provided for tracking a functional part of an instrument and displaying dynamic imaging corresponding to a functional part of the instrument. The method comprises: receiving imaging data from an imaging machine; constructing an image volume; determining a three-dimensional shape of a flexible tether having one end fixed at a known location relative to the imaging machine and having an instrument connector disposed at an opposite end; determining a location of the functional part of the instrument using the known location of the fixed end of the tether, the three-dimensional shape of the tether, and a pre-determined size and shape of the instrument; and displaying a dynamic image corresponding to the instrument and showing the functional part of the selected instrument in the image volume.

According to one embodiment the flexible tether comprises fiber optic cores disposed longitudinally in the tether. A plurality of optical scatterers (e.g. Fiber Bragg Gratings or Rayleigh scatterers) are disposed in optical fiber cores or claddings. The reflectivity at different locations along the tether is measured. From these length-resolved reflectivity measurements, length-resolved strain and curvature calculations are made. From the latter, the three dimensional shape of the tether is calculated.

According to one embodiment the instrument is selected from a plurality of instruments. The method of this embodiment further comprises receiving identification of a selected instrument attached to the instrument connector selected from a plurality of instruments. In one embodiment, the instrument is removed, a new instrument is attached to the tether, and the new instrument is identified by the instrument identification unit.

According to one embodiment, the method further comprises refining the shape calculations for the tether using real-time imaging.

The present invention provides a method and system for markerless tracking of an instrument during an intervention procedure and for displaying an image space corresponding to the selected instrument and showing the functional part of the selected instrument in the image space.

According to one embodiment of the present invention, an instrument tracking system10comprises an imaging system100used to acquire and display an image space showing anatomical structures proximate to an intervention procedure to be performed. The imaging system100may be a C-arm flat-detector CT imaging system as shown inFIG. 1. Alternatively, the imaging system may be an MRI, CY, X-ray, ultrasound, or any other type of imaging system appropriate for acquiring images of anatomic structures for use in guiding an instrument during an intervention procedure. According to one embodiment, the imaging system100is an imaging system capable of providing a three-dimensional image volume.

The instrument tracking system10also comprises an instrument200for use in an intervention procedure. The instrument may be any instrument used during an intervention, including but not limited to: a mechanical scalpel (lancet), a laser scalpel, an endoscope, microscopic imaging probes, a surgical stapler, a retractor, a cautery device (electrical or optical), a catheter, a chisel, a clamp, a probe, a trocar, scissors, or the like. The instrument200is manipulated by a physician to perform an intervention procedure. In many intervention procedures, a physician will use more than one instrument. Therefore, according to one embodiment, the instrument tracking system comprises more than one instrument.

The instrument200(or one of the instruments) is connected to a connection point101on the imaging system100by a tether300. The connection point101is a point that can be registered to the coordinates of the image space of the imaging system100. According to one embodiment, the connection point is at an optical connector110. In the illustrated embodiment, the optical connector110is fixed on the C-arm body of the CT imaging system.

The instrument200is connected to the tether300by a connector310. According to one embodiment, the connector300uses clamping force to hold the instrument firmly in place. The connector310comprises a cylinder311fixedly connected to the tether300by crimping, adhesive, or any other appropriate fastening method. The cylinder may be plastic or any other suitable radiolucent structural material. The cylinder311has an external thread which is engaged with an internal thread on a collar312. The collar may also be plastic or any other suitable radiolucent structural material. A tapered flexible wrap313extends into the collar opposite the tether300and is affixed to the cylinder311by adhesive, clamping, or any other suitable fixation method. The flexible wrap may be rubber or any other radiolucent flexible material suitable for deforming and clamping an instrument. The instrument200is placed into the open tapered flexible wrap313and may be abutted to a flange on the cylinder311for precision location of the instrument200relative to the tether300. The collar312is rotated about the cylinder311advancing the collar312along its axis away from the tether300and pressing on the tapered flexible wrap313to securely hold the instrument200in place.

The connector310allows a physician to attach any one of a plurality of instruments200to the tether300. Moreover, the connector310allows the physician to change instruments during an intervention procedure, as will be described hereafter.

According to alternative embodiments, the instrument200may be connected to the tether300by adhesive, a magnetic connection, threaded engagement of the instrument directly to the tether300or a threaded member attached to the tether, or any other suitable connection method.

The tether300comprises optical fiber cores324(FIG. 3), which together with an optical console400(FIG. 1) form a shape sensing system320that provides strain information. This strain information can be used to determine the precise location of the instrument200and to present the instrument location on an image from the imaging system100.

Within the tether300, at least one and preferably four optical fibers324extend along the tether axis325as shown inFIG. 3. Preferably one fiber core is on-axis and the others arranged in a helical fashion around the on-axis fiber core. It should be noted that the four cores could either be contained within a single fiber (thereby sharing the cladding) or in separate fibers mechanically connected (e.g. glued). According to one embodiment, the optical fibers324are symmetrically arranged around the tether axis325. A plurality of optical scatterers are provided in the optical fiber cores or claddings in a plurality of locations along the length of the tether300(a single Fiber Bragg grating is shown inFIG. 4).

A Fiber Bragg Grating is a segment of an optical fiber that reflects particular wavelengths of light and transmits all other wavelengths of light. This is achieved by adding a periodic variation of the refractive index in the fiber core, which generates a wavelength-specific dielectric mirror. A Fiber Bragg Grating can therefore be used as an inline optical filter to block certain wavelengths, or as a wavelength-specific reflector.

As shown inFIG. 4, the core of the optical fiber324has a refractive index of n2along most of its length. However, the refractive index is periodically changed to a different refractive index n3at a spacing of λB/2neff(where neffis the effective refractive index of the optical mode).FIGS. 5A-5Cshow the spectral response of a broadband light signal to the Bragg Grating. As shown inFIG. 5A, a broad spectrum light signal is input to the optical fiber324. The light is split into light that is not at a wavelength λBwhich is transmitted through the Bragg Grating (shown inFIG. 5B) and light at a wavelength of λBwhich is reflected by the Bragg Grating (shown inFIG. 5C).

Fiber Bragg Gratings involve Fresnel reflections at each of the interfaces where the refractive index changes. For some wavelengths, the reflected light of the various periods is in phase with one another so that constructive interference exists for reflection and consequently, destructive interference for transmission.

The Bragg wavelength is sensitive to strain as well as to temperature. This means that Bragg gratings can be used as sensing elements in fiber optic sensors. In a FBG sensor, the measurand causes a shift in the Bragg wavelength λB. The relative shift In the Bragg wavelength, ΔλB/λB, due to an applied strain (∈) and a change in temperature (ΔT) is approximately given by:
δλB/λB=CS∈+CTΔT(1)

The coefficient CSis called the coefficient of strain and its magnitude is usually around 0.8×10−6/μ∈ (or in absolute quantities about 1 pm/μ∈). The coefficient CTdescribes the temperature sensitivity of the sensor; it is made up of the thermal expansion coefficient and the thermo-optic effect. Its value is around 7×10−6/K (or in absolute quantity 13 pm/K).

A plurality of optical scatterers330(e.g. Fiber Bragg Gratings or Rayleigh scatterers) can be distributed over the length of an optical fiber in the core or cladding to form sensors or gauges to measure strain. Incorporating at least four fiber optic cores with various sensors (gauges) along the length of a fiber that is embedded in a structure allows for the three-dimensional form of the structure to be precisely determined. As shown inFIG. 6, scatterers330are located at each of a plurality of positions along the length of the tether300. The local curvature of the tether300can be determined from the length-resolved strain and curvature measurements acquired from the tether300. The total three-dimensional form of the tether300is determined from the plurality of strain and curvature measurements.

According to one embodiment, multiple tethers can be used to simultaneously track multiple instruments in the coordinates of the image volume acquired from the imaging system100.

Returning toFIG. 1, an optical console400is connected to the optical fiber cores324of the tether300at the connection point101. In the illustrated embodiment, the optical console is mounted within the C-arm body of the imaging system100. The optical console400delivers light to the optical fibers and/or fiber optic cores and receives light from them. In the case where Fiber Bragg Gratings are utilized, the optical console400can determine the Bragg wavelength λBfor different portions of each Fiber Bragg Grating322.

According to one embodiment, an attachment means150is disposed on the C-arm of the imaging system100to secure the loose end of the tether300during rotational scans. The attachment means may be any mechanical connection device suitable for securing the tether300.

FIG. 7is a block diagram of the instrument guidance system10shown inFIG. 1. A processing unit500comprises a processor510which is operably connected to a memory520. According to one embodiment, they are connected through a bus530. The processor510may be may be any device capable of executing program instructions, such as one or more microprocessors. The memory may be any volatile or non-volatile memory device, such as a removable disc, a hard drive, a CD, a Random Access Memory (RAM), a Read Only Memory (ROM), or the like.

A display540is also operably connected to the processor510. The display may be any monitor, screen, or the like suitable for presenting a graphical user interface (GUI) capable of presenting medical images.

An imaging unit120, such as the C-arm102(inFIG. 1) of an imaging system100, is operably connected to the processor510. The imaging unit provides imaging data to the processor510for processing to create an image volume of anatomical features. The image volume is then presented on the display540. The processing unit500and the imaging unit120together form an imaging system100.

A shape determining unit550provides strain and curvature data from the tether300to the processor510. The shape determining unit comprises the optical shape sensor (including optical fiber cores324that are located in the tether300along its longitudinal axis325). The shape determining unit550further comprises an optical console400, which interrogates the optical fiber cores sending a broadband light signal along each optical fiber core and measuring the reflected wavelengths to determine length-resolved strain and curvature in each optical fiber core. Alternatively, the reflection spectrum may be obtained from a narrow band light source whereby the wavelength is swept in time. The localized curvatures are used to determine the shape of the tether300within the image space.

The optical console400may have a processor (not shown) separate from the processor510in the processing unit500. Moreover, the optical module400may perform some or all of the calculations for wavelength shift, strain, and curvature; and provide wavelength measurements, shift calculations, strain calculations, or curvature data to the processor510. The processor510processes imaging data to form an image space which is presented on the display540. The data from the shape determining unit550is processed, as necessary to calculate curvatures over the length of the tether300. This shape data is used by the processor510, together with the known registration point101at the fixed end of the tether300(FIG. 1) to determine the location and orientation of the tether300at the connection310, and therefore the location and orientation of the instrument200in the image space.

An Instrument Identification Unit (IIU)560is operably connected to the processor510in the processing unit500. The IIU560comprises means for identifying one of a plurality of instruments200in use by a physician during an intervention procedure. The identifying means may comprise a Radio Frequency Identification (RFID) receiver, with each instrument200or its packaging having an RFID transmitter attached to it. Alternatively, the identifying means may be a bar code reader, with each instrument200or its packaging having a bar code printed on it. According to another embodiment, a resistance code or microchip may be embedded in or attached to each instrument200. According to yet another embodiment, the identifying means may be a keyboard or keypad, with the physician manually entering an identification indication, such as a code, or selecting from a menu, or the like. The identifying means may be integral with the connector310such that the identification information is transmitted through the tether300. Alternatively, the identifying means may be disposed at another location, such as the processing unit with the instrument200brought to the identifying means for identification.

Referring now toFIG. 8, a flow diagram is shown for a method for dynamically tracking an instrument in an image space. A patient is positioned on an imaging system100(step810). Patient positioning is performed according to known procedures in the art. According to one embodiment, the patient is positioned on an XperCT imaging system within the C-arm body as shown inFIG. 1.

A three-dimensional rotational XperCT scan is performed on the patient (step820). The scan is performed according to known procedures in the art. It should be understood that alternate embodiments are contemplated using forms of imaging other than the three-dimensional rotational XperCT scan. Moreover, a scan may be performed before a procedure, during a procedure, or both.

The processor510constructs an image volume from the scan data (step830). The image volume is constructed using procedures known in the art showing anatomical structures.

A physician connects the tether300to the imaging unit of the imaging system100at the connection point101(step840). Connection point101is a location that can be registered to the image volume. That is, the location of the connection point is known relative to the image volume. An optical connector110is provided at the connection location101. According to one embodiment, the connection point101is located on the C-arm body of a XperCT imaging system. In another embodiment, a connection point may be at a source or detector for an imaging system.

The physician connects the tether300to the imaging system100(step850). The tether is installed in the optical connector110, which is connected by optical fibers to the optical console400. According to one embodiment, the tether300is connected after the scan is performed. According to another embodiment, the tether300is connected prior to a scan and secured to the imaging system100at its distal end using attachment means150.

An instrument identification unit560identifies a selected instrument200(step860). As previously described, the instrument identification unit560may be an RFID receiver, a bar code reader, a keyboard or keypad, an electrical sensor, or any other means suitable for providing a code or signal to indicate a selected one of a plurality of instruments200. The RFID transmitter, bar code, or the like may be provided on the selected instrument200or on its packaging. In the RFID example, the physician takes the instrument200or packaging with the RFID transmitter and places it in proximity to the RFID receiver of the instrument identification unit560. The RFID receiver of the instrument identification unit560receives the RFID signal and transmits the RFID code to the processor510. Alternatively, a processor separate from the imaging processor510may receive the identification code. In an alternative embodiment, the physician enters an instrument200identification code using a keyboard, keypad, or the like.

The processor510determines the shape of the tether300(step870). Using known calculation methods, the known connection point101, and the curvature data from each sensor triplet330along the length of the tether300, the imaging processor510calculates the complete three-dimensional shape of the tether and registers it to the image volume. According to alternate embodiments, a processor separate from the image processor510determines the shape of the tether300. Also, according to various embodiments, the strain calculations and curvature calculations may be performed by the imaging processor510, another processor, or a combination thereof. Alternatively, the processor could calculate the complete three-dimensional shape of a portion of the tether that is clinically relevant; this portion of the tether could be localized relative to the imaging system or another structure by means of one or more markers that are positioned on the tether and tracked with known methods that do not involve the optical fibers or optical fiber cores described in this invention (e.g. EM tracking).

The processor510determines the location and orientation of the functional part of the selected instrument200(step880). Once the three-dimensional shape of the tether, the connection point101, and the identification of the selected instrument200are known, the image processor510determines the location of the functional part of the selected instrument200and the orientation of the selected instrument200in the image space. This determination is performed using a preprogrammed shape and size for the selected instrument200.

The processor510displays the image volume of the patient corresponding to the selected instrument showing the instrument in the image volume (step890). Different views of the image volume would be more appropriate for different instruments200. For example, for a procedure that involves a needle insertion, an image volume in which critical structures such as blood vessels are segmented and highlighted might be appropriate. As another example, for a procedure that involves removing brain tumor tissue with a scalpel or suction device, an image volume in which tumor tissue is segmented and highlighted might be appropriate. The processor510displays an image most useful or corresponding to which instrument200is selected. The processor510shows the selected instrument200in the image.

The displayed image may be from a pre-procedural scan or a scan performed during a procedure. For example, a pre-procedural image may be acquired using CT or MRI. Following the imaging, the patient is moved to a surgical table, where an XperCT image is acquired (rotational C-arm scan). The XperCT image is co-registered with the CT and/or MRI images. Two-dimensional flouroscopic images may be acquired in real-time and registered with the pre-procedural and XperCT images, such as for tracking (or refining) the depth of a scalpel.

In another example, no pre-procedural images are acquired. The patient is moved to a surgical table, where an XperCT image is acquired before the procedure starts (rotational C-arm scan), and potentially at different time points during the procedure. Optionally, fluoroscopic images may be acquired in real-time and registered to the XperCT images.

In another example, no pre-procedural images are acquired. The patient is moved to a surgical table with an open MRI. A MRI image is acquired before the procedure and potentially at different time points during the procedure.

In each of the foregoing procedures, the functional part of the instrument200can be registered to any of the acquired images, because the tether300is fixed at a location that is defined relative to the images (being a fixed location on the imaging equipment) and the three-dimensional shape of the tether300can be calculated, giving the location of the instrument200. The selected instrument200is identified, so that the size and shape can be retrieved from memory and used to determine the precise location of the functional part of the instrument. Also, the selected instrument200may change during a procedure. For example, a physician may switch from a scalpel to a stapler. Since the new selected instrument200is identified, as previously described, the location of the functional part of the new selected instrument200can be determined with respect to the image space and an appropriate image can be presented showing the new selected instrument200.

According to an alternative embodiment, at least one radio-opaque marker is disposed on the tether300or on the selected instrument200. The radio-opaque marker is visible under two-dimensional fluoroscopy. When 2D fluoroscopy is utilized during a surgical intervention, the position of the marker(s) in a plane perpendicular to the x-ray detector-emitter axis can be determined in real-time. This determination can be performed by digital analysis of the fluoroscopic images, using image pattern recognition algorithms that are well-known in the scientific community. The marker positions can be utilized as reference points to improve the accuracy at which the 3D shape of the tether300and location of the instrument200are calculated.

According to another alternate embodiment, at least one electromagnetic (EM) or optical marker is disposed on the tether300or on the selected instrument200. The marker positions, as determined by EM or optical sensors, are utilized as reference points to improve the accuracy at which the 3D shape of the tether300and/or instrument200is calculated.

Referring now toFIG. 9, a shape-sensing tether300is rigidly attached to a combined X-ray breast mammography/biopsy system900. The tether is connected at either the X-ray source910, the detector920, the biopsy system, or any other rigid transformation point.

Breast mammography systems are able to obtain depth information on tumor nodules by performing tomosynthesis imaging, which involves moving a camera and detector around an object (in this case a breast). Based on images created using this procedure, depth information on tumor location is obtained which is later used for guided or automated breast biopsy.

Using a shape-sensing tether300, a conventional, markerless, biopsy needle is tracked and placed with excellent accuracy based on the previously acquired tomosynthesis images. Since the tether300is mechanically connected to the combined imaging/biopsy system900, the position of the instrument connector310, and therefore the biopsy needle, as calculated with the shape determining algorithm is automatically registered to the coordinates of the tomosynthesis X-ray images.

The use of an optical shape sensing system in this particular application has the significant advantage that it is not sensitive to EM distortions that occur when using EM tracking. EM distortions occur due to metal, which is omnipresent in current X-ray mammography/biopsy systems.

The preceding description and accompanying drawing are intended to be illustrative and not limiting of the invention. The scope of the invention is intended to encompass equivalent variations and configurations to the full extent of the following claims.