MRI DISPLAY OUTPUT REFLECTING CONTRAST AGENT CONCENTRATION AS A FUNCTION OF TIME

Abstract

A magnetic resonant imaging (MRI) review workstation includes a control processor, and a display integrated or otherwise operatively coupled with the control processor, wherein the control processor is configured to receive and analyze magnetic resonant imaging information pertaining to an imaged volume of tissue, and to cause to be displayed on the display output information that reflects or is otherwise indicative of an absorption rate of a contrast agent in the volume of tissue.

Claims

1-20. (canceled)

21. A computer-implemented method for processing magnetic resonant imaging (Mill) data, the computer-implemented method comprising: receiving, at a MM workstation, respective electronic MRI data of an imaged tissue volume acquired by different Mill scanners over respective periods of time after a respective contrast agent is introduced into a patient; converting, by a control processor, a plurality of signal enhancement ratio curves associated with the different Mill scanners into an absorption rate curve, the absorption rate curve describing absorption rates of the respective contrast agent in the imaged tissue volume and compensating for a non-linear relationship between an Mill signal generated by an Mill scanner during imaging of the imaged tissue volume and a concentration of the respective contrast agent over time; deriving a signal intensity ratio for the imaged tissue volume based on an actual absorption rate of a respective contrast agent in the imaged tissue volume for all of the different Mill scanners; normalizing the signal enhancement ratio curves for the imaged tissue volume so that a signal enhancement ratio is independent of the MRI scanners used to generate the electronic Mill data; and deriving an absorption rate the respective contrast agent in the image tissue volume.

22. The computer-implemented method of claim 21, wherein the respective electronic MRI data is received at the MM workstation while at least a portion of the patient is positioned within the respective different MRI scanners.

23. The computer-implemented method of claim 21, further comprising presenting, by a display of the MM workstation operably coupled to the control processor and to a user of the MM workstation, the converted absorption rates of the respective contrast agent in the imaged tissue.

24. The computer-implemented method of claim 21, the respective electronic MM data comprising first electronic MM data acquired by a first Mill scanner, second electronic Mill data acquired by a second Mill scanner different from the first Mill scanner, and third electronic MRI data acquired by a third MM scanner different from the first Mill scanner and the second MM scanner, wherein the Mill workstation receives the respective first, second and third electronic MRI data from the respective first, second and third MM scanners.

25. The computer-implemented method of claim 21, wherein the converted absorption rate curve is presented to a user of the MM workstation during acquisition of respective electronic MM data by an MM scanner.

26. The computer-implemented method of claim 21, wherein the converted absorption rate curve is based at least in part upon a pre-contrast relaxation value of the imaged tissue volume as determined by the different MM scanners.

27. The computer-implemented method of claim 26, wherein the pre-contrast relaxation value of the imaged tissue volume is a value obtained using a reference tissue, wherein the reference tissue is pectoral muscle tissue or local fatty tissue, and the tissue volume is breast tissue.

28. The computer-implemented method of claim 26, wherein the pre-contrast relaxation value of the imaged tissue volume is a value obtained by direct measurement prior to introduction of the respective contrast agent into the tissue volume.

29. The computer-implemented method of claim 26, wherein the pre-contrast relaxation value of the imaged tissue volume is based on a predetermined approximation.

30. The computer-implemented method of claim 23, further comprising presenting, by the display of the MM workstation and to the user, an absolute value of absorption of the respective contrast agent in the imaged tissue volume.

31. The computer-implemented method of claim 21, wherein the respective contrast agent are introduced into the patient by injection thereof into the patient's vasculature.

32. The computer-implemented method of claim 31, wherein the respective electronic Mill data is acquired by a respective Mill scanner while a respective contrast agent travels through the patient's vasculature.

33. The computer-implemented method of claim 21, wherein the converted absorption rate curve compensates for the non-linear relationship between the Mill signal and the concentration of the respective contrast agent over time caused by at least one operating parameter of the Mill scanner that generates the Mill signal.

34. The computer-implemented method of claim 33, wherein the at least one operating parameter is at least one of repetition time (TR), echo time (TE), and flip angle of an alpha pulse.

35. The computer-implemented method of claim 21, wherein the converted absorption rate curve provides an accurate indication of whether a wash out of the respective contrast agent has occurred in the imaged tissue volume during acquisition of the respective electronic Mill data by the different Mill scanners.

36. The computer-implemented method of claim 21, wherein the respective electronic Mill data of the imaged volume of tissue acquired by the different Mill scanners correspond to the disparate signal enhancement ratio curves comprising a first signal enhancement ratio curve and a second signal enhancement ratio curve obtained for the same imaged tissue volume by the different MM scanners, wherein the respective first and second signal enhancement curves are associated with respective Type I-III curves for the imaged tissue volume, a Type I curve indicating benign tissue, a Type II curve being suggestive of potential cancer and a Type III curve being most indicative of cancer compared to the Type I curve and the Type II curve.

37. The computer-implemented method of claim 36, the converted absorption rate curve comprising the signal enhancement ratio curve that is normalized to take into account the actual absorption rate of the respective contrast agent in the imaged tissue volume and that indicates whether a wash out of the respective contrast agent occurred in the imaged tissue volume during acquisition of the respective electronic MRI data.

38. The computer-implemented method of claim 21, further comprising generating the respective electronic MM data by activation of at least one MRI scanner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 is a captured MRI workstation display screenshot of a graph depicting relative signal intensity as a function of time.

[0032] FIG. 2 is a graph reproduced from Kuhl et al 2, depicting exemplary signal intensity curves types I, II and III.

[0033] FIG. 3 is a table showing the MRI systems and imaging protocols used in the Jansen et al. study.

[0034] FIGS. 4A-4C are respective pie charts illustrating a proportion of cases in data sets exhibiting Types I, II and III curves for the respective different imaging systems used in the Jansen et al. study.

[0035] FIG. 5A depicts signal enhancement as a function of concentration for different values of T.sub.10, and FIG. 5B depicts the signal enhancement ratio versus contrast agent concentration, respectively, from the 3 systems in Newstead et al with T.sub.10 selected at 1200 ms.

[0036] FIG. 6 is a graph depicting a first, hypothetical concentration curve exhibiting high initial uptake followed by rapid washout or type II, and a second, signal enhancement curve derived therefrom exhibiting high initial uptake followed by a plateau or Type II.

[0037] FIG. 7 is a pie chart in which the data depicted in FIG. 4C is corrected to accurately represent the distribution of curve types which is differentiated by washout ratio from peak enhancement.

[0038] FIGS. 8A and 8B are graphs depicting T.sub.10 estimation using the Reference Tissue method.

[0039] FIG. 9A-D are respective graphical depictions of example signal enhancement ratio curves being “normalized” based on actual contrast agent absorption.

[0040] FIG. 10 is a flow diagram depicting an MRI imaging acquisition and analysis method carried out according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE DISCLOSED INVENTIONS

[0041] In describing the depicted embodiments of the disclosed inventions illustrated in the accompanying figures, specific terminology is employed for the sake of clarity and ease of description. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner. It is to be further understood that the various elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other wherever possible within the scope of this disclosure and the appended claims.

[0042] In contrast to the prior art display modalities, a new display provided in accordance with one aspect of the disclosed inventions plots a concentration of contrast agent as a function of time, making the indirect connection between signal and concentration irrelevant. As explained herein, the concentration may be computed from the known physics of the MRI acquisition and the known acquisition parameters. Embodiments of the display are to be used with (as part of) an MRI display workstation, in which the time plot of contrast agent concentration may supplement or replace the presently used signal intensity plot depicted in FIG. 1, in order to more provide more accurate information to the medical professional for evaluating patient MRI information.

[0043] The difficulties resulting from the non-linear relationship between the signal and the concentration of contrast agent are demonstrated in Jansen et al [1], which describes a study performed of 601 patients, including 497 malignant and 185 benign lesions viewed on three different scanner/protocol combinations. The three data sets produced were called “System 1-3” by the authors, each group indicating which of the three scanner/protocol combinations was used for each individual case. The table shown in FIG. 3 summarizes the MRI systems and Protocols used in the study. The present inventors believe the parameters most responsible for differences are shown in the TR/TE row and the Flip angle. The finding of this study was that only 47% of Invasive ductal carcinoma (IDC) lesions imaged with System 3 exhibited washout type curves, compared with 75% and 74% of those imaged with System 1 and System, 2. These differences are shown graphically in the pie charts of FIGS. 4A-4C, in which:

[0044] FIG. 4A depicts the respective proportion of data sets exhibiting Type III washout (40a), Type II plateau (44a), and Type I persistent (42a) for System 1;

[0045] FIG. 4B depicts the respective proportion of data sets exhibiting Type III washout (40b), Type II plateau (44b), and Type I persistent (42b) for System 2; and FIG. 4C depicts the respective proportion of data sets exhibiting Type III washout (40c), Type II plateau (44c), and Type I persistent (42c) for System 3.

[0046] It is believed that many if not most medical professional base their diagnosis of the malignancy of a lesion largely on which of these curve types is characteristic of its time curve, with Type III being most indicative of cancer, Type I indicative of benign tissue, and Type II either suggestive or ambiguous. There is an intuitive explanation of why a malignant lesion would be expected to have a Type III curve having to do with the vascularity of lesions and vessel permeability. Breast cancer has increased vascularity with an increased permeability leading to an early uptake and early washout behavior, i.e., Type III. However, the results of the Jansen et al study, as summarized in the pie charts in FIGS. 4A-C, suggest that cases may be placed into different types or classifications, due of differences in scanner/protocol parameters used in the signal acquisition, not only because of underlying likelihood of malignancy. This would appear to be a very serious disadvantage of the present method of analyzing kinetic behavior.

[0047] The present inventors believe this problem occurs as a result of the non-linear relationship between the MRI signal and the contrast agent concentration, in particular, in a signal of the type shown in FIG. 1, and not the concentration being observed and classified into Types I-III. In the spoiled gradient echo sequence, the standard method used in dynamic breast MRI, the signal intensity can be expressed as a function of tissue and acquisition parameters by equation 1 [3,4]:

[00001]$\begin{array}{cc}S\left(t\right)=\mathrm{PD}\times \sin \alpha \times \frac{1-\exp \left(-\mathrm{TR}/T_1\right)}{1-\cos \mathrm{\alpha exp}\left(-\mathrm{TR}/T_1\right)}& \left(1\right)\end{array}$

where P is the proton density, D is the scanner gain, α is the flip angle, and T1 is the tissue relaxation time, a characteristic of the tissue being examined.

[0048] The tissue relaxation time T.sub.1 is related to the pre-contrast relaxation time T.sub.10 and the local tissue relaxation rate R.sub.1. This is assumed to be in a linear fashion as shown in equation 2 [5,6]:

[00002]$\begin{array}{cc}\frac{1}{T_1}=\frac{1}{T_{10}}+R_{1\mathrm{CA}}C\left(t\right)& \left(2\right)\end{array}$

where R.sub.ICA is treated as a known constant, uniquely determined by the choice of contrast agent [Rohrer et al 7].

[0049] Introducing equation 2 into equation 1, the relative signal enhancement is given by equation 3:

[00003]$\begin{array}{cc}E\left(t\right)=\frac{S\left(t\right)-S\left(0\right)}{S\left(0\right)}=\frac{\left[1-\exp \left(-\mathrm{TR}/T_{10}\right)\cos \alpha \right]\left(1-\exp \left\{-\mathrm{TR}\left\{1/T_{10}+R_1{C}_t\left(t\right)\right\}\right\}\right)}{\left(1-\exp \left\{-\mathrm{TR}\left[1/T_{10}+R_1{C}_t\left(t_0\right)\right]\right\}\cos \alpha \right)\left[1-\exp \left(-\mathrm{TR}/T_{10}\right)\right]}-1& \left(3\right)\end{array}$

[0050] Relative signal enhancement allows the proton density to cancel out. This is the fundamental relationship between signal intensity E(t) and contrast agent concentration C(t), and it depends on many parameters that change between protocols, such as TR and flip angle α, and on parameters that depend on the tissue T.sub.10. Specifically, this demonstrates a highly non-linear relationship between S(t) and C(t), meaning that the shape of the C(t) curve will not in general be preserved when transformed to S(t).

[0051] By way of demonstrative example, FIG. 5A depicts signal enhancement as a function of concentration for different values of T.sub.10, and FIG. 5B depicts the signal enhancement ratio versus contrast agent concentration from the 3 systems in Newstead et al with T.sub.10 selected at 1200 ms. One skilled in the art will be able to observe the non-linearity of the curves in FIG. 5A. In particular, the curve for System 3 even shows saturation at approximately 200%, i.e., the concentration can increase greatly without a significant increase in signal.

[0052] A hypothetical case demonstrates how a concentration curve with the suspicious time dependence of Type III can be turned into the ambivalent signal curve of Type II by this non-linear transformation. Curve 62 in FIG. 6 shows the hypothetical concentration curve exhibiting high initial uptake followed by rapid washout. The y-axis for concentration is shown at left and is in units of mmol/liter. Curve 60 shows the signal enhancement derived from this with the transformation shown in FIG. 6. The y-axis is on the right is in units of %. The peak concentration point occurring near time point 3 is depressed relative to later points due to the saturation of the concentration—signal curve. This tends to make a “peaking” distribution (Type III), flatter, or more like Type II. Clearly, in this case, shown in FIG. 6, the signal enhancement exhibits plateau behavior in spite of a clear Type III behavior of the concentration.

[0053] Similarly, a continuously increasing concentration of the Type I curve type can artificially plateau because of the saturation of the Signal/Concentration curve, and become a Type II signal curve. In retrospect it is believed that the intuitive expectation of the curve types is actually an expectation of the curve shape for concentration enhancement, which is generally assumed to be equivalent to the curve shape for signal enhancement, but this would only be true if the transformation from the former to the later were linear, which it is not.

[0054] Notably, the present inventors used the average peak signal enhancement ratio of malignant cancers in the UC data, and converted the ratio into contrast agent concentration to simulate the change in the pie chart shown in FIG. 4C. This is depicted in FIG. 7, which shows much closer agreement to System 1 and System 2, consistent with the proposition by the present inventors that the non-linear transformation from concentration to signal is responsible for the different proportions shown in FIG. 4C. Thus, one advantage of proving a display of kinetic information in the form of Contrast as a function of time, rather than signal versus time, is that contrast is the quantity that is directly related to the physiology of the lesion, independent of scanner parameters such as TR and TE and flip angle α, and thus avoids the adverse effects caused by non-linearity.

[0055] Having described and explained the advantage of displaying C(t) versus time over the traditional S(t) display, we now discuss in detail how the concentration can be obtained from the known physics of the MRI acquisition process and the known acquisition parameters.

[0056] The physics of the acquisition, given in Equation 4, repeated here:

[00004]$\begin{array}{cc}E\left(t\right)=\frac{S\left(t\right)-S\left(0\right)}{S\left(0\right)}=\frac{\left[1-\exp \left(-\mathrm{TR}/T_{10}\right)\cos \alpha \right]\left(1-\exp \left\{-\mathrm{TR}\left\{1/T_{10}+R_1{C}_t\left(t\right)\right\}\right\}\right)}{\left(1-\exp \left\{-\mathrm{TR}\left[1/T_{10}+R_1{C}_t\left(t_0\right)\right]\right\}\cos \alpha \right)\left[1-\exp \left(-\mathrm{TR}/T_{10}\right)\right]}-1& \left(4\right)\end{array}$

[0057] This well-known equation, sometimes called the “FLASH” equation, is correct for the spoiled gradient echo sequence, which is the most commonly used sequence for breast MRI [8]. Other sequences, such as “TURBO FLASH”, although rarely used in breast MRI applications, will have other known equations relating Signal E(t) to Concentration C(t). In this equation, the repetition time TR and flip angle α are parameters set by the operator of the scanner. R.sub.1 is the rate constant, measured in other experiments to be 4.3 to 6.7 L/mml s, depending on the type of Gadolineum Chelate used [7]. The remaining parameter in this equation is T.sub.10, the pre-contrast value of tissue T.sub.1. Although “textbook” values for T.sub.10 may be taken from published measurements of “typical tissue,” these numbers can have significant errors when applied to different individuals, and do not adequately take into account the variability observed in an actual tissue lesion.

[0058] Alternative methods of measuring the T.sub.10 value at each voxel of the imaged volume from the individual patient include T1 mapping, which requires at least one, and preferably two extra volume acquisitions prior to injection of CA, each acquisition using a different flip angle α. This method can be understood by considering the signal equations for the commonly used scanner sequences used in breast imaging (SPGR, FFE, or FLASH). In these sequences a series of low flip angle RF pulses are used within a short TR period. The signal from an FFE sequence with flip angle α across the whole slice is given by equation 5:

[00005]$\begin{array}{cc}\rho \left(a\right)={\rho }_0\frac{1-e^{\mathrm{TR}/T_1}}{1-\cos a\times e^{\mathrm{TR}/T_1}}\sin a& \left(5\right)\end{array}$

[0059] A computationally simple method for estimating T1 can be obtained by manipulating equation 4 and rearranging into the form shown below in equation 6.

[00006]$\begin{array}{cc}\frac{\rho \left(a\right)}{\sin a}=e^{-\mathrm{TR}/T_1}\frac{\rho \left(a\right)}{\tan a}+{\rho }_0\left(1-e^{-\mathrm{TR}/T_1}\right)& \left(6\right)\end{array}$

[0060] Note that a plot of p/(sinα vs ρ/tanα) at different values of flip angle forms a straight line with slope a=exp(−TR/T1). T1 can therefore be obtained as:

T1=−TR/1n(α)  (7)

[0061] To obtain the slope then requires at least two sequences with different flip angles, or, for better accuracy, three flip sequences with different flip angles. T1 mapping therefore requires extra volume acquisitions, each one adding approximately a minute to the total patient procedure. It may happen that this extra scanning time is prohibitively expensive for many medical facilities, and for this reason the present inventors prefer a further alternative approach using reference tissue instead of textbook values or T1 mapping. In particular assuming, as in conventional DCE-MRI protocols, the use of short TR and small flip angle, the relative signal S(0)/S.sub.ref(0) (as opposed to the absolute signal S(0) of a lesion) is relatively insensitive to the actual protocol adjustment of MRI system. In this case the following linear relation can be used to estimate the pre-contrast relaxation T.sub.10.

[00007]$\begin{array}{cc}\frac{S\left(0\right)}{S_{\mathrm{ref}}\left(0\right)}=\frac{.Math.1-\exp \left(-\mathrm{TR}/T_{10\mathrm{ref}}\right)\cos \alpha .Math.\left(1-\exp \left(-\mathrm{TR}/T_{10\mathrm{ref}}\right)\right)}{\left[1-\exp \left(-\mathrm{TR}/T_{10\mathrm{ref}}\right)\cos \alpha \right]\left(1-\exp \left(-\mathrm{TR}/T_{10\mathrm{ref}}\right)\right)}\approx \frac{T_{10\mathrm{ref}}}{T_{10}}& \left(8\right)\end{array}$

[0062] where S.sub.ref(0) is the signal intensity of muscle tissue prior to contrast agent injection and T.sub.10ref is a T.sub.1 relaxation time of muscle tissue before contrast agent injection. S(0) and T.sub.10 are the signal and T.sub.10 value respectively of the tissue of interest.

[0063] As depicted in FIGS. 8A and 8B, by assuming the measured value for breast pectoral muscle of the T.sub.1 relaxation time of 607 ms [9], the T.sub.10 estimated from equation 4 using a standard DCE-MRI protocol (TR/TE:5.2/2.5 ms, FA:10 as recommended by the QIBA panel) results in less than 0.3% error in a range from 400 ms to 2000 ms of true T.sub.10 values. The graph of FIG. 8B shows the maximum error occurring at very large values of T1, but with most of the T1 range with a much smaller error. Brix's [9] study also confirms the viability of using the relative signal ratio (S(0)/S.sub.fat(0)) to estimate the lesion T1 relaxation value.

[0064] Two uncertainties in this method might include B1 inhomogeneity and what literature value of T.sub.10 of normal pectoral muscle [9] tissue is used. The present inventors believe the former is not a concern and that the Reference Tissue method is robust to B1 inhomogeneity error because of the low flip angle used in the DCE-MRI protocol for breast. For example, using the same imaging protocol as in FIG. 8, but with a large B1 inhomogeneity that results in a 50% change in the signal still yields less than 3% of error in the T.sub.10 estimation. Thus, while obtaining the pre-contrast value T.sub.10 using the above-described “Reference Tissue” method can result in a possible error due an erroneous literature value of T.sub.10, such error (especially if pectoral muscle is chosen as the reference tissue), should not substantially impact on the accuracy of the estimated and displayed contrast agent in the patient tissue volume as a function of time.

PROPOSED MRI REVIEW WORKSTATION

[0065] In view of the foregoing, the present invention provides an improved MRI review workstation display, in which output information is displayed in conjunction with the patient imaging data that reflects or is otherwise indicative of an absorption rate of a contrast agent in the volume of tissue. While the form and content of the output information may vary depending on the particular system display design and reviewer preferences, what is important is that the displayed output information provides an accurate indication of whether or not a “wash out” of the contrast agent occurred in the tissue volume during acquisition of the imaging information, regardless of a particular imaging system or imaging protocol employed to acquire the imaging information.

[0066] By way of non-limiting example, the output information may be a graphical representation of a concentration of the contrast agent in the tissue volume as a function of time during acquisition of the imaging information. Alternatively and/or additionally, the output information may be a graphical representation of a signal intensity ratio in the tissue volume as a function of time, wherein the signal intensity ratio is normalized to take into account an actual absorption rate of the contrast agent in the tissue volume. These options are shown in FIGS. 9A-D, which demonstrates how the imaging data reflected in what appear to be disparate signal enhancement ratio curves shown in FIGS. 9A and 9B obtained for the same tissue volume using different MRI systems into and/or imaging protocols can instead be reflected (i.e., converted) into the absorption rate curve shown in FIG. 9C, which in turn can be converted back to a signal enhancement ratio curve shown in FIG. 9D that has been “normalized” so that the displayed curve accurately reflects the tissue volume image data notwithstanding the differences in the imaging system and/or protocol used to acquire the imaging data.

[0067] Thus, as is depicted in FIGS. 9A-D, the MRI review workstation controller (aka “control processor”) of embodiments of the present invention is preferably programmed to compute the so-called normalized signal intensity ratio based, at least in part, upon a pre-contrast relaxation value of the tissue volume. Also, regardless of the particular form of the displayed output information, the contrast agent concentration as a function of time is preferably computed by the workstation control processor based, at least in part, upon a pre-contrast relaxation value of the tissue volume. As explained above, the pre-contrast relaxation value of the tissue volume may be obtained using any of (i) a Reference Tissue method, (ii) direct measurement, or (iii a predetermined approximation. In an embodiment in which the tissue volume being imaged is breast tissue, a Reference Tissue method is preferably employed, wherein the reference tissue is pectoral muscle tissue or local fatty tissue. It may also be desired to have the output information comprise), or otherwise include, an absolute value of absorption of the contrast agent in the tissue volume.

[0068] With reference to FIG. 10, in accordance with still another aspect of the disclosed inventions, a method is provided for acquiring and evaluating magnetic resonant imaging (MRI) information of a volume of tissue, such as but not limited to breast tissue. The method 100 includes, at step 102, obtaining a pre-contrast relaxation value for the tissue volume. This can be accomplished by any one of alternative steps 104, using a reference tissue method, 106, directly measuring the relaxation value prior to introducing the contrast agent, or 108, using a predetermined approximation for the respective tissue volume.

[0069] Thereafter, at step 110, the contrast agent is introduced into the subject's vasculature, e.g., by injection or other means. Then, at step 112, MRI imaging information of the tissue volume is acquired over the requisite time period. At step 114, the imaging information is analyzed/evaluated, i.e., by the review workstation processor, and at step 116, the workstation displays on a display integrated or otherwise operatively coupled with the workstation, output information that reflects or is otherwise indicative of an absorption rate of a contrast agent in the volume of tissue during the period of time, wherein the output information provides an indication of whether or not a wash out of the contrast agent occurred in the tissue volume during acquisition of the imaging information. As discussed above, the contrast agent concentration is computed as a function of time based, at least in part, upon a pre-contrast relaxation value of the tissue volume. As also discussed above, the output information may include displaying a graphical representation of a signal intensity ratio in the tissue volume as a function of time, wherein, as indicated at step 118 in FIG. 10, the signal intensity ratio is normalized to take into account an actual absorption rate of the contrast agent in the tissue volume.

[0070] Having described exemplary embodiments, it can be appreciated that the examples described above and depicted in the accompanying figures are only illustrative, and that other embodiments and examples also are encompassed within the scope of the appended claims. For example, while the flow diagrams provided in the accompanying figures are illustrative of exemplary steps; the overall image merge process may be achieved in a variety of manners using other data merge methods known in the art. The system block diagrams are similarly representative only, illustrating functional delineations that are not to be viewed as limiting requirements of the disclosed inventions. Thus the above specific embodiments are illustrative, and many variations can be introduced on these embodiments without departing from the scope of the appended claims.