DETERMINING A LOCATION OF AN APPARATUS IN AN MRT SYSTEM

Abstract

A method for determining a location of an apparatus inside an imaging volume of an MRT system surrounded by a basic field magnet for creating a static basic magnetic field along a longitudinal axis and by a gradient coil is provided. The apparatus has a first conductor loop that runs within a loop plane. The method includes creating a magnetic alternating field in the imaging volume using the gradient coil. At least one measured value that depends on an induction voltage that is induced by a component of the alternating field at right angles to the longitudinal axis in the at least one conductor loop is determined using the at least one first conductor loop. A location of the apparatus inside an imaging volume is determined at least partly as a function of the at least one measured value and a predetermined magnetic field model for the gradient coil.

Claims

1. A method for determining a location of an apparatus inside an imaging volume of a magnetic resonance tomography (MRT) system, wherein the imaging volume is surrounded by a field magnet for creating a static basic magnetic field along a longitudinal axis and by a gradient coil of the MRT system, and wherein the apparatus comprises at least one first conductor loop that runs within a first loop plane, the method comprising: creating a magnetic alternating field in the imaging volume using the gradient coil; determining at least one first measured value that depends on a first induction voltage using the at least one first conductor loop, the first induction voltage being induced by a first component of the magnetic alternating field at right angles to the longitudinal axis in the at least one first conductor loop; determining a location of the apparatus inside the imaging volume at least partly as a function of at least one first measured value and a predetermined magnetic field model for the gradient coil; detecting a magnetic resonance (MR) signal from an object to be examined in the imaging volume by the at least one first conductor loop; and creating an MR image as a function of the MR signal.

2. The method of claim 1 wherein to determine the at least one first measured value, the MR signal is suppressed.

3. The method of claim 1, wherein the apparatus is positioned in the imaging volume such that the first loop plane is at least approximately parallel to the longitudinal axis.

4. The method of claim 1, wherein the apparatus further comprises at least one second conductor loop that runs within a second loop plane, and wherein the method further comprises: determining, using the at least one second conductor loop, at least one second measured value that depends on a second induction voltage that is induced by a second component of the alternating field at right angles to the longitudinal axis in the at least one second conductor loop; and determining the location of the apparatus at least partly as a function of the at least one first measured value, the at least one second measured value, and the magnetic field model for the gradient coil.

5. The method of claim 4, wherein the apparatus is positioned in the imaging volume such that the second loop plane is at least approximately parallel to the longitudinal axis.

6. The method of claim 4, wherein the apparatus has at least one third conductor loop that runs within a third loop plane, wherein the method further comprises: determining, using the at least one third conductor loop, at least one third measured value that depends on a third induction voltage that is induced by a third component of the alternating field at right angles to the longitudinal axis in the at least one third conductor loop; determining a first location of the at least one first conductor loop inside the imaging volume at least partly as a function of the at least one first measured value and the magnetic field model; determining a third location of the at least one third conductor loop inside the imaging volume at least partly as a function of the at least one third measured value and the magnetic field model; and determining a relative location of the at least one third conductor loop with regard to the at least one first conductor loop as a function of the first location and the third location.

7. The method of claim 2, wherein the apparatus is positioned in the imaging volume such that the first loop plane is at least approximately parallel to the longitudinal axis.

8. The method of claim 7, wherein the apparatus further comprises at least one second conductor loop that runs within a second loop plane, and wherein the method further comprises: determining, using the at least one second conductor loop, at least one second measured value that depends on a second induction voltage that is induced by a second component of the alternating field at right angles to the longitudinal axis in the at least one second conductor loop; and determining the location of the apparatus at least partly as a function of the at least one first measured value, the at least one second measured value, and the magnetic field model for the gradient coil.

9. The method of claim 8, wherein the apparatus is positioned in the imaging volume such that the second loop plane is at least approximately parallel to the longitudinal axis.

10. The method of claim 8, wherein the apparatus has at least one third conductor loop that runs within a third loop plane, wherein the method further comprises: determining, using the at least one third conductor loop, at least one third measured value that depends on a third induction voltage that is induced by a third component of the alternating field at right angles to the longitudinal axis in the at least one third conductor loop; determining a first location of the at least one first conductor loop inside the imaging volume at least partly as a function of the at least one first measured value and the magnetic field model; determining a third location of the at least one third conductor loop inside the imaging volume at least partly as a function of the at least one third measured value and the magnetic field model; and determining a relative location of the at least one third conductor loop with regard to the at least one first conductor loop as a function of the first location and the third location.

11. A magnetic resonance tomography (MRT) system comprising: a field magnet operable to create a static basic magnetic field along a longitudinal axis, and a gradient coil, wherein the field magnet and the gradient coil surround an imaging volume of the MRT system; an apparatus with at least one first conductor loop that runs within a first loop plane; a control unit that is configured to activate the gradient coil, such that a magnetic alternating field is created in the imaging volume; a measurement unit that is connected to the at least one first conductor loop and is configured, as a function of a first induction voltage that is induced by a component of the alternating field at right angles to the longitudinal axis in the at least one first conductor loop, to determine at least one first measured value; and at least one evaluation unit that is configured to determine a location of the apparatus inside an imaging volume at least partly as a function of at least one first measured value and a predetermined magnetic field model for the gradient coil, wherein the at least one evaluation unit is configured, depending on a magnetic resonance (MR) signal from an object to be examined in the imaging volume, to create an MR image.

12. The MRT system of claim 11, further comprising a local MR receive coil arrangement that contains the apparatus.

13. The MRT system of claim 12, wherein the local MR receive coil arrangement is configured as a flexible surface coil array.

14. The MRT system of claim 11, further comprising a device for medical treatment of a patient, wherein the at least one first conductor loop and the device have a predetermined spatial location in relation to one another.

15. The MRT system of claim 11, wherein the apparatus comprises: a tuning capacitance that is arranged between a first terminal of the at least one first conductor loop and a second terminal of the at least one first conductor loop; and an inductive component that is arranged electrically in parallel to the tuning capacitance.

16. The MRT system of claim 13, wherein the apparatus comprises: a tuning capacitance that is arranged between a first terminal of the at least one first conductor loop and a second terminal of the at least one first conductor loop; and an inductive component that is arranged electrically in parallel to the tuning capacitance.

17. The MRT system of claim 14, wherein the apparatus comprises: a tuning capacitance that is arranged between a first terminal of the at least one first conductor loop and a second terminal of the at least one first conductor loop; and an inductive component that is arranged electrically in parallel to the tuning capacitance.

18. The MRT system of claim 15, wherein the measurement unit comprises an amplifier that is connected to the first terminal and the second terminal, and wherein the measurement unit is configured to provide the at least one measured value at an output of the amplifier, which is connected to the at least one evaluation unit.

19. The MRT system of claim 18, wherein the measurement unit comprises a filter circuit that is arranged between the first terminal and a first input of the amplifier, and between the second terminal and a second input of the amplifier, and wherein the filter circuit is configured to suppress an MR signal acquired by the at least one first conductor loop.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0082] The invention will be explained in greater detail below with the aid of concrete exemplary embodiments and associated schematic diagrams. In the figures the same elements or elements with the same function are provided with the same reference character. The description of the same elements or elements with the same function may not be repeated with regard to different figures. In the figures:

[0083] FIG. 1 shows a schematic diagram of an embodiment of a magnetic resonance tomography (MRT) system;

[0084] FIG. 2 shows a schematic diagram of a magnetic field;

[0085] FIG. 3 shows a schematic diagram of an apparatus of a further embodiment of an MRT system;

[0086] FIG. 4 shows a schematic diagram of an apparatus of a further embodiment of an MRT system;

[0087] FIG. 5 shows a schematic diagram of an apparatus of a further embodiment of an MRT system;

[0088] FIG. 6 shows a schematic diagram of an apparatus of a further embodiment of an MRT system;

[0089] FIG. 7 shows a schematic diagram of an apparatus of a further embodiment of an MRT system;

[0090] FIG. 8 shows a schematic diagram of an apparatus of a further embodiment of an MRT system;

[0091] FIG. 9 shows a schematic diagram of an apparatus of a further embodiment of an MRT system; and

[0092] FIG. 10 shows a schematic diagram of possible basic forms of a local MR receive coil.

DETAILED DESCRIPTION

[0093] FIG. 1 is a schematic of an embodiment of a magnetic resonance tomography (MRT) system 1.

[0094] The MRT system 1 also has a field magnet (not shown) that creates a static magnetic field for alignment of nuclear spins of a sample (e.g., of a patient) in an imaging volume 3 in the z direction that may be referred to as the longitudinal axis of the MRT system. The imaging volume 3 is characterized by a very homogeneous static magnetic field in the z direction. The field magnet may, for example, involve a superconducting magnet that may provide magnetic fields with a magnetic flux density of up to 3 T or more. For smaller field strengths, however, permanent magnets or electromagnets with normally conducting coils may also be used.

[0095] Further, the MRT system 1 has a gradient coil 2 and also a control unit 5 for activating the gradient coil 2 that is configured, for spatial differentiation of the imaging regions acquired in the imaging volume 3, to overlay the static magnetic field with magnetic fields of which the amount may change, depending on location, along all three spatial directions x, y, z. The gradient coil 2 may, for example, be configured as a coil of normally conducting wires.

[0096] The MRT system 1 may, for example, have a body coil 30 as a send antenna that is configured to radiate a radio frequency signal supplied via a signal line into the imaging volume 3.

[0097] The control unit 5 may supply the gradient coil 2 and the body coil 30 with different signals. The control unit 5 may, for example, have a gradient controller that is configured to supply the gradient coil 2 via supply lines with variable currents that, temporally coordinated, may provide the desired gradient fields in the imaging volume 3.

[0098] The control unit 5 may also have a radio frequency unit that is configured to create radio frequency pulses or excitation pulses with predetermined temporal waveforms, amplitudes, and spectral power distribution for exciting a magnetic resonance of the nuclear spin in the patient. In such cases, pulse powers in the range of kilowatts may be employed. The excitation pulses may be radiated into the patient via the body coil 30 or via one or more local send antenna. The control unit 5 may also contain a controller that may communicate via a signal bus with the gradient controller and the radio frequency unit.

[0099] The body coil 30, in some forms of embodiment, may also be used to receive resonance signals (e.g., magnetic resonance (MR) signals) emitted by the patient, and output the resonance signals via a signal line. The body coil 30 in such forms of embodiment may thus serve as both a receive antenna and also as a send antenna.

[0100] Optionally, a local MR receive coil (not shown), also referred to as a local coil, of the MRT system 1 may be arranged in the immediate vicinity of the patient, which may be linked via a connecting line to a measurement unit 6. The measurement unit 6 may also be part of the control unit 5. Depending on form of embodiment, the local coil, as an alternative or in addition to the body coil 30, may serve as a receive antenna.

[0101] The MRT system 1 may also have an evaluation unit 7 that is connected to the control unit 5 (e.g., to the radio frequency unit). The evaluation unit 7 may evaluate the MR signals and, based thereon, reconstruct an MR image according to known methods. The control unit 5 may also be part of the evaluation unit 7.

[0102] The MRT system 1 has an apparatus with at least one conductor loop 4 that runs within a loop plane and, for example, is arranged in the imaging volume 3 such that the loop plane is essentially oriented in parallel to the z direction.

[0103] As described, the gradient coil 2, activated by the control unit 5, creates a magnetic alternating field in the imaging volume 3. This magnetic alternating field generally has magnetic field components in all three spatial directions x, y, z. As a consequence, an induction voltage is brought about in the at least one conductor loop 4, even when the loop plane is oriented essentially in parallel to the z direction.

[0104] The measurement unit 6 is connected to the at least one conductor loop 4 and is configured, depending on the induction voltage, to determine at least one measured value. The evaluation unit 7 is configured to determine, at least partly, a location of the apparatus inside an imaging volume 3 as a function of the at least one measured value and a predetermined magnetic field model for the gradient coil 2.

[0105] In forms of embodiment with a local MR receive coil, this may include the apparatus or the at least one conductor loop 4. The location of the apparatus then thus corresponds to the location of the local MR receive coil. As an alternative, the apparatus may be used as a self-contained location sensor, with which, for example, the location of a medical device (not shown) in the imaging volume 3 may be at least partly determined, especially when the relative location of the medical device in relation to the at least one conductor loop 4 is known.

[0106] An example for the magnetic field model is shown schematically in FIG. 2. Contrary to the usual simplified assumption, the gradient fields created by the gradient coil 2 in the imaging volume 3 are not aligned exactly parallel to the direction of the static magnetic field (e.g., the z direction). Instead, the gradient coil 2 creates additional field components that are aligned orthogonally to z (e.g., along the x or y axis), and the amplitude of which is also comparable with the z component. Since the components of the alternating field along the x or y axis are very much smaller than the static basic magnetic field, these components may be ignored for the regular MRT imaging. For this reason, the components of the alternating field along the x-axis and the y-axis have in the past also not been taken into consideration for other possible applications. Since the components of the alternating field, unlike the static basic magnetic field, are time-dependent, the components of the alternating field contribute significantly to the induction in the conductor loop 4 and may therefore be used for location determination in accordance with the present embodiments.

[0107] FIG. 2, by way of example, shows the cartesian components of the magnetic field, as are acquired inside the gradient coil 2, which is operated in the static mode (e.g., with a constant current). No basic magnetic field of the field magnet is present. At each sampling point, three field values that correspond to the three orthogonal field components Bx, By and Bz have been measured with a vector magnetometer that was attached to a robot arm and was positioned at 480 spatial positions that are distributed over the surface of a sphere. Based on these measured values, with the aid of a calibrated magnetic field model, the magnetic field at any given place within the imaging volume 3 may be computed. The at least one conductor loop 4, which is located in the imaging volume 3 of the MRT system 1, thus acquires a signal induced by the pulsed gradient fields, even if the loop plane is essentially oriented in parallel to the z direction.

[0108] Through the present embodiments, it is not absolutely necessary to use additional sensors for determination of the location of a local MR receive coil. Instead, the conductor loops of the local MR receive coil already present may be employed both for detection of the weak radio frequency MRT signals and also for detection of the signals induced by the gradient pulses in the low-frequency range.

[0109] The voltage that is induced in a conductor loop when the magnetic flux through the region surrounded by the conductor loop changes is produced by an integration of the change of the magnetic vector field B over the surface A enclosed by the loop (e.g., by application of Faraday’s law of induction):

[00001]$\text{U}={\displaystyle \int \frac{\text{d}\stackrel{.fwdarw.}{\text{B}}}{\text{dt}}\cdot \text{d}\stackrel{.fwdarw.}{\text{s}}}$

[0110] Shown in FIG. 3 to FIG. 5 are schematic implementations of the apparatus with the at least one conductor loop 4 for different embodiments of the MRT system 1 (e.g., of the MRT system 1 from FIG. 1).

[0111] Through these apparatuses, the MRT system 1 is capable of simultaneously receiving the radio frequency MR signals and the low-frequency signals for location determination induced by pulsing gradient fields.

[0112] A multi-channel MR receive coil may be embodied, for example, as a two-dimensional flexible array that consists of a number of receive elements, such as 2 to 32 or even 64 receive elements. Such a receive element is shown in FIG. 3 to FIG. 5. The receive element has the at least one conductor loop 4 (e.g., configured as at least one copper loop), as well as tuning devices (e.g., tuning capacitors 9a, 9b) that are arranged between a first terminal 21a and a second terminal 21b of the at least one conductor loop 4. Detuning devices 10 may also be provided, which, for example, contain a detuning capacitor 12 and a series circuit arranged in parallel thereto with a detuning inductance 13 and a diode 14.

[0113] A preamplifier circuit 18 that is connected on an input side via a matching circuit 16 to the terminals 21a, 21b and on an output side to an analog-to-digital converter 19, which may be linked via a data bus 20 to the evaluation unit 7 or a computer, may be provided. The tuning capacitors 9a, 9b are, for example, distributed along the at least one conductor loop 4 in order to reduce the electrical fields that otherwise occur over long line conductor segments and may possibly lead to dielectric losses and thus to a reduced signal-to-noise ratio. The capacitances of the tuning capacitors 9a, 9b are, for example, tuned such that the tuning capacitors 9a, 9b resonate with the inductance of the at least one conductor loop 4 at the Larmor resonant frequency of the MRT system 1, which, depending on field strength, may have a high frequency, for example, in the range of 1 MHz to 500 MHz.

[0114] In parallel to the tuning capacitors 9a, 9b and to the detuning capacitor 12 in each case is an inductive component 11a, 11b, 11c, so that the low-frequency signals induced by the gradient fields in the range of a few kHz may be acquired. The inductivity of inductive components 11a, 11b, 11c is chosen so that, for the induced radio frequency MR signals, these have a high impedance and in practice correspond to an open circuit. By contrast, the electrical impedance of the inductive components 11a, 11b, 11c at low frequencies is essentially equivalent to a short circuit, which closes the at least one conductor loop 4 for the signals induced by the pulsing gradient fields. The values of these inductances depending on the Larmor frequency may, for example, lie in the range of a few hundred .Math.H to many mH.

[0115] In some forms of embodiment, a signal preamplifier 17 may be connected on the input side via a filter circuit 15 that may be configured, for example, as a lowpass filter, to the terminals 21a, 21b and, on the output side, to a further input of the analog-to-digital converter 19 or to a further analog-to-digital converter (not shown). The signals induced by the pulsed gradients and acquired by the at least one conductor loop 4 may then be read out via the data bus 20 and be further used by the signal processing algorithms, in order to extract the information about the location of the at least one conductor loop 4. In a similar way, the location of further receive elements may also be determined, and thus, the form of the flexible multi-channel MR receive coil may be described.

[0116] FIG. 4 shows schematically a receive element of an apparatus in a further form of embodiment of the MRT system 1 for a newer type of MR receive coil that uses distributed tuning capacitances 9 instead of discrete capacitors, which are formed by parasitic capacitances between conductor segments of at least one conductor loop 4. In this case, the separate conductor segments are effectively short circuited by the inductive components 11a, 11b, 11c for lower frequencies, so that the conductor segments form a double loop. Also indicated in FIG. 4 is a supply voltage 8 for the preamplifier circuit 18.

[0117] FIG. 5 shows schematically a receive element of an apparatus in a further embodiment of the MRT system 1. The receive element is based on the receive element shown in FIG. 3.

[0118] The receive element of FIG. 5, in corresponding forms of embodiment, fulfills a function referred to as local shimming. For example, the evaluation unit 7 or another computer connected to the receive element, for example, may adapt a direct current through the at least one conductor loop 4, in order to compensate for local inhomogeneities of the static magnetic field. The desired digital value of the direct current is, for example, transferred via a further data bus 25 to a further digital-to-analog converter 24, of which the output outputs a corresponding signal to a constant current driver 23. The constant current driver 23 may transmit the signal, for example, via a further lowpass filter 22 to the at least one conductor loop 4.

[0119] The further lowpass filter 22 in this case is, for example, configured so that the further lowpass filter 22 transmits the direct current value from the constant current driver 23 to the at least one conductor loop 4 and, in doing so, blocks the low-frequency alternating current signals induced by the pulsed gradient fields as well as the radio frequency MR signals. The filter circuit 15 may then, for example, be configured as a bandpass filter that may let the alternating current signals induced by the pulsing gradient fields pass and suppresses the direct current component and also the radio frequency MR signals. In a similar way, a receive element with distributed tuning capacitances 9 may be adapted as in FIG. 4.

[0120] The spatial location of objects within the imaging volume 3 may be determined, for example, through the processing of the signals, which are dependent on orthogonal coils that are attached to the object as a function of the voltages induced by the pulsing gradient fields. One method may begin with an initial estimation and then iteratively adapt the object position and alignment until the specific convergence criteria are fulfilled. In another method, a translation matrix is calibrated in a pre-training step, in which a test object moves in steps, an image volume is acquired for each step at the same time, and the gradient activity is measured. These methods may also be combined with the aid of the method of the present embodiments, of the MRT system 1 of the present embodiments, or of the apparatus of the MRT system 1 of the present embodiments in order to achieve the advantages explained.

[0121] This is a method that may be used for recognizing the shape and position of local flexible MR receive coils 28, as shown schematically in FIG. 6 to FIG. 9 and for recognizing the patient movement. In this case, the advantages already explained may be utilized.

[0122] Flexible MR receive coils 28, for example, have a relatively large number of receive elements with corresponding conductor loops that, when attached to the body of the patient 29, may change their shape, as shown in FIG. 6 to FIG. 9, in order to follow the contours of the body of the patient 29, and that possibly also move because of the breathing movement or the heartbeat of the patient 29.

[0123] Shown in FIG. 6 is a flexible MR receive coil 28 with a number of receive elements that have corresponding conductor loops 4, where the receive elements may, for example, be embedded in a flexible plastic material 26 and may be connected to a controller 27. FIG. 7 shows schematically a flexible MR receive coil 28 for imaging the head of the patient 29, FIG. 8 shows a flexible MR receive coil 28 for imaging the knee of the patient 29, and FIG. 9 shows a flexible MR receive coil 28 for imaging the abdomen of the patient 29.

[0124] In order to describe a flexible MR receive coil 28 mathematically with high degree of accuracy, mathematical models for quadric surfaces may be used. Quadric surfaces include spheres, ellipsoids, cylinders (e.g., circular cylinders or elliptic cylinders), elliptic paraboloids, parabolic cylinders, cones, hyperbolic cylinders, double-layer hyperboloids, hyperbolic paraboloids, single-layer hyperboloids, hyperboloids of one or two sheets, and so forth, as shown schematically in FIG. 10 in order from top left to bottom right. Viewed mathematically a quadric surface is the graph of a second-order equation in the three variables x, y, z. The general form of the equation is:

[00002]$\begin{array}{c}\text{A}*{\text{x}}^2+\text{B}*{\text{y}}^2+\text{C}*{\text{z}}^2+\text{D}*\text{x}*\text{y}+\text{E}*\text{y}*\text{z}+\text{F}*\text{x}*\text{z}\\ +\text{G}*\text{x}+\text{H}*\text{y}+\text{I}*\text{z}+\text{J}=0,\end{array}$

where A to J 10 represent coefficients that may be varied to adapt the shape of the coil. Based on this observation, shape and location of the flexible MR receive coil 28 may be determined with the aid of the measured voltages that are induced by temporally variable gradient fields in the receive elements. For example, the following acts may be carried out: a) initialization of the quadric surface to an initial estimated shape by allocation of initial values to the coefficients A to J; b) initialization of the offset (x.sub.0, y.sub.0) of the coil and of the angle of rotation of the coil with regard to the x axis; c) adaptation of the arrangement of the receive elements (e.g., of the conductor loops 4 to the quadric surface); d) computation of the voltages induced in the conductor loops 4, taking into account the current shape of the coil and the gradient strengths as described above; e) use of a gradient descent method in order to adapt the values of the coefficients A to J, the offset (x.sub.0, y.sub.0), and the angle of rotation, so that the mean quadric error between the voltages computed in act d) and the measured voltages is reduced; f) iterative repetition of the acts c), d), and e) until the mean quadric error falls below a specific threshold value.

[0125] Different acts of this method may also be further optimized. With a flexible MR receive coil 28 such as is shown in FIG. 6, the initial shape may, for example, be restricted so that the shape corresponds to the surface of a cylinder or of a parabolic cylinder oriented along the axis. A parabolic cylinder that is symmetrical along the x axis is described mathematically by a very simple equation: A*y.sup.2 = 0.

[0126] For other MR receive coils 28, the shape of one or more hyperbolic paraboloids may be more suitable. For this, the simplified equation: A*x.sup.2 - B*y.sup.2 + z = 0 applies.

[0127] This type of pre-optimization speeds up the speed of conversion of the iterative algorithm, in that the pre-optimization reduces the number of coefficients A to J and sets a starting point that lies closer to the eventual solution. The same consideration applies for the coil offset and the coil rotation. The numerical range in which these parameters may change may be restricted here and, in this way, forces the iterative algorithm to remain close to the eventual solution.

[0128] The present embodiments may also be applied for wireless coils that combine an analog-to-digital converter on the coil with a wireless digital transmission.

[0129] The methods described above are variable with already known methods for recognition of the patient movement, such as by Hall sensors, 2D or 3D video cameras, or MR movement navigators being able to be combined in order to further refine and to improve the results.

[0130] The elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent. Such new combinations are to be understood as forming a part of the present specification.

[0131] While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.