Abstract:
Systems and associated methods are provided for improving detection and measurement of elements in a medium, particularly the measurement of gaseous bubbles in liquid medium, such as blood injected into a patient&#39;s body. The systems include a radiation emitter to emit radiation for traversing through a medium, and an analyzer subsystem to receive and to analyze the traversed radiation for presence and/or absence of gaseous elements in the medium. The methods include receiving at least one collection of data corresponding to at least one emitted radiation traversed through a medium, analyzing said collection of data for at least one predetermined condition; and generating a response upon detection of at least one predetermined condition.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application claims priority of U.S. Provisional Application Serial No. 60/269,033, filed Feb. 15, 2001, whose contents are fully incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention is generally directed to detectors. More particularly, the present invention relates to detectors used in medical devices for detecting the presence and/or lack of predetermined elements in a medium while increasing the precision in the dimensional measurements of the elements.  
         BACKGROUND OF THE INVENTION  
         [0003]    Presently, many medical procedures with the goal of providing fluids to a patient&#39;s body through external tubing make use of detection mechanisms to monitor the presence of undesirable elements such as gaseous bubbles in the provided fluid. For example, one such commonly used procedure is for conducting dialysis. During dialysis, a patient&#39;s blood is generally circulated extracorporeally through an artificial kidney machine, such as a dialysis machine, where harmful and other undesirable elements in the blood are largely filtered from the blood. The filtered blood is then returned to the patient&#39;s body, generally through tubing connected directly to a blood vessel. The returned blood, however, may still contain undesirable elements, such as undissolved gaseous bubbles or columns of air that can be harmful if allowed to enter a patient&#39;s body. In order to prevent or minimize gaseous bubbles from entering the body, a detection device is commonly used to monitor the blood for the gaseous bubbles prior to the bubbles entering the patient&#39;s body. An example of one such air-bubble detector is set forth in U.S. Pat. No. 5,583,280, the disclosure of which is herein incorporated by reference.  
           [0004]    Currently, ultrasonic air bubble detectors are used for monitoring blood for gaseous bubbles and other undesirable elements. The details of one such ultrasonic air bubble detector are set forth in U.S. Pat. No. 5,394,732 to Johnson et al, the disclosure of which is herein incorporated by reference.  
           [0005]    Conventional ultrasonic air bubble detectors generally transmit an ultrasonic wave from a transmitter through the tubing containing the flowing blood. An ultrasonic wave receptor/detector collects the transmitted wave at the opposite side of the tubing and the waveform is then translated into a signal and analyzed. The analysis generally involves a study of the changes in the ultrasonic waveform characteristics, such as attenuation, resulting from passage through a fluid medium, such as blood. These changes are then compared to predetermined settings indicating the presence of gaseous bubbles in the blood. Other changes in the blood affecting propagation of the ultrasonic wave, such as increased or decreased blood density, are also analyzed and fed back to the transmitter. The transmitter then re-calibrates various waveform parameters, such as intensity and/or frequency, to account for any changes in the blood, thus enabling the detector to continuously detect gaseous bubbles.  
           [0006]    In addition to fluid changes, other factors may also affect and/or compromise bubble detection capabilities using ultrasound. For example, it is generally well known that sound waves are susceptible to noise, both ambient and internal. As a result, there exists the potential that any noise detected by the receiver, together with the waveform signal, may cause an erroneous bubble-detection reading. In addition, a sound wave&#39;s relatively large wavelength may limit a detector&#39;s degree of precision in detecting and/or measuring bubble sizes. In particular, small bubbles of air, for example on the order of several micro-liters, may flow through the tubing undetected by the detector and enter the patient&#39;s circulatory system. Such an occurrence would obviously be very harmful, and likely fatal, to the patient.  
           [0007]    Although presently available bubble detection devices are well accepted by the medical profession, it is desirable to have a detector that can further minimize and better detect the number of bubbles that may be entering the body of a patient. In particular, it is desirable to have a detector that can detect smaller bubbles of air and with greater degree of precision, while providing for faster recalibration of the detector in the event of sudden changes in the fluid medium.  
         SUMMARY OF THE INVENTION  
         [0008]    In view of the foregoing, it is the object of the present invention to provide a bubble detection system that addresses the obstacles and disadvantages associated with current bubble detectors.  
           [0009]    A further object of the present invention is to provide a bubble detector system that can accommodate a variety of tubing designs and fluids having various volumes, concentrations, viscosities, etc.  
           [0010]    A further object of the present invention is to provide a cost-effective system with reliable and repeatable detection capabilities, thereby eliminating false air-detect readings/signals.  
           [0011]    The present invention attempts to address these objects and other objects not specifically enumerated herein through the use of a detector system that includes at least one radiation emitter subsystem to emit at least one radiation emission for traversing through a medium and at least one analyzer subsystem to receive and analyze the traversed radiation for presence and/or absence of gaseous elements in the medium. The system may detect gaseous elements in both stationary and flowing fluid.  
           [0012]    Another embodiment the present invention contemplates a method for analyzing data to determine presence and/or absence of predetermined conditions in a medium. The method includes receiving at least one collection of data corresponding to at least one emitted radiation traversed through a medium, analyzing the collection of data for at least one predetermined condition and generating a response upon detection of at least one predetermined condition.  
           [0013]    Another embodiment of the present invention contemplates a method for sensing as used in a detector. The method includes emitting at least one radiation emission traversing through a medium, receiving and analyzing the traversed radiation for presence and/or absence of gaseous elements in the medium and generating data based on the analysis.  
           [0014]    In one embodiment of the present invention, a graphical user interface having internal power, input panels with preset command and display of status lines is used to better aid the user with the operations of the present invention. The interface may communicate with the present invention in either parallel or serial mode. In addition, multiple emitters may also be used in combination to increase the accuracy of the detection and/or calibration process.  
           [0015]    This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description and drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    Other features and advantages of the present invention will be seen as the following description of particular embodiments progresses in conjunction with the drawings, in which:  
         [0017]    [0017]FIG. 1 illustrates one embodiment of the overall system architecture of the present invention;  
         [0018]    [0018]FIG. 2 illustrates in greater detail the flow of the operations of one embodiment of the present invention;  
         [0019]    [0019]FIG. 3 is one embodiment of a circuit diagram of one subsystem of the present invention illustrated in FIG. 2;  
         [0020]    [0020]FIG. 4 is one embodiment of a circuit diagram of another subsystem of the present invention illustrated in FIG. 2;  
         [0021]    [0021]FIG. 5A is one embodiment of a flow chart of the operations of a subsystem of the present invention illustrated in FIG. 2; and  
         [0022]    [0022]FIG. 5B is another embodiment of a flow chart of the operations of a subsystem of the present invention as illustrated in FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    The present invention is directed to improving the detection capability and detection time by which the presence and/or absence of predetermined elements is detected in a medium while also increasing the precision in the dimensional measurements of the predetermined elements. The present invention may be utilized with various systems. Examples of systems included within the scope of the present invention include, but are not limited to, the systems disclosed in U.S. Pat. No. 6,221,045, U.S. Pat. No. 6,004,292, U.S. Pat. No. 5,988,587, U.S. Pat. No. 4,650,465, U.S. Pat. No. 5,451,211, U.S. Pat. No. 5,456,670, U.S. Pat. No. 4,695,271, U.S. Pat. No. 5,865,805, U.S. Pat. No. 5,925,022, U.S. Pat. No. 5,899,885, U.S. Pat. No. 6,042,565, U.S. Pat. No. 6,063,052, U.S. Pat. No. 6,090,064, U.S. Pat. No. 6,149,627, the disclosures of which are hereby incorporated by reference in their entirety into the present application.  
         [0024]    Although the present invention is described with reference to radiation, the term radiation, as used herein, includes, but is not limited to, light, ultrasound, electromagnetic and other energy forms known in the art.  
         [0025]    [0025]FIG. 1 illustrates the overall system architecture of one embodiment of the present invention. The system includes a radiation emitter subsystem  100 , detector subsystem  200 , signal conditioning subsystem  101 , multi-stage differentiating subsystem  102 , and recalibration subsystem  106 . This non-invasive system does not contact fluid or require a break in tubing to detect the presence of air.  
         [0026]    As illustrated in FIG. 1, the radiation emitter (or transmitter) subsystem  100  emits a radiation waveform  107  that traverses through tubing  105  containing a fluid medium such as blood. The radiation waveform  107  is received by receiver or detector  200 , converted into an electro-optical signal and forwarded to the signal conditioning subsystem  101 . Although the emitter  100  and detector  200  illustrated in FIG. 1 are in linear alignment with each other, other configurations including, but not limited to, angled alignment or parallel alignment, are also included within the scope of the present invention. The signal conditioning subsystem  101  filters out undesirable components of the signal, such as noise and ambient light, before forwarding the signal to the multistage differentiating subsystem  102 .  
         [0027]    The multi-stage differentiating subsystem  102  subsequently determines whether any undesirable elements  108 , such as undissolved gaseous bubbles or columns of air, exist in the fluid medium. Other determinations, such as presence of tubing, absence of tubing, empty tubing, fluid filled tubing, stagnant air bubbles and/or sensor door state, may also be performed. The results of these determinations are outputted, such as in the form of a bubble detect signal  103  or a column (e.g., air column) detect signal  104 , to microprocessor  240 . If the microprocessor and its algorithms  240  detect the presence of any undesirable elements  108 , flow of operation may be interrupted and/or warnings to the user may be generated. The results of these determinations are also forwarded to the recalibration subsystem  106  in the form of a feedback signal. Based on the feedback data, the recalibration subsystem  106  can then recalibrate the radiation emitter subsystem  100  to a desired setting by altering the characteristics of the emitted radiation waveform, such as changing the intensity and/or frequency of the waveform. The recalibration is required for numerous reasons including: temperature drift, LED degradation, mechanical alignment (including tubing position, tubing clarity, etc.) and change in fluid medium (e.g., blood (opaque) to saline (clear)).  
         [0028]    In one embodiment of the present invention, a user interface, such as a parallel user interface  250  or serial user interface  251 , can be coupled to the system for ease of use by a user. In addition, the system may also be configured for low power, possible battery operation, and small over-all size.  
         [0029]    [0029]FIGS. 2, 3 and  4  illustrate in greater detail the flow of operations (FIG. 2) and associated circuitry (FIGS. 3 and 4) of the present invention.  
         [0030]    As illustrated in FIG. 2, the radiation emitter subsystem  100  includes a constant current source subsystem  120  and a light emitting diode subsystem  130 . The programmable adjustable constant current source subsystem  120  controls the flow and characteristics of the waveform to be generated and emitted by the light emitting diode subsystem  130 . The light emitting diode subsystem  130  includes a light emitting diode (LED)  131  and a LED circuit  132 . The LED circuit  132  (shown in FIG. 3) receives control-instructions from the light emitting diode subsystem  130  and accordingly activates the LED  131  to emit the desired radiation waveform  107 . As illustrated in the circuit diagram in FIG. 3 and discussed in greater detail below, the radiation waveform  107  emitted by the LED  131  can be recalibrated by the recalibration subsystem  106 .  
         [0031]    Referring more particularly to FIG. 2, the radiation waveform  107  emitted by the LED  131  traverses through tubing  105  containing a fluid medium, such as blood, and is received by detector  200 . The detector  200  converts the received waveform into an electro-optical signal for forwarding to the signal conditioning subsystem  101 . In an exemplary embodiment illustrated in the circuit diagram of FIG. 3, the LED circuit  132  can be used to both send signals to the LED  131 , such as from pins  1  and  3 , and receive subsequent signals from detector  200 , such as in pin  2 , for forwarding to the signal conditioning subsystem  101 , such as from pin  4 . In an exemplary embodiment of the present invention, multiple radiation waveforms  107  emitted from one or multiple radiation emitter subsystems  100  stationed at the same or axially different angles to the fluid medium may be used. Each waveform can then be analyzed and matched against the results of the other to increase the accuracy and precision of the subsequent analysis.  
         [0032]    Returning to FIG. 2, the signal conditioning subsystem  101  includes ambient-light sample-and-hold (ALSH) subsystem  201 , summation circuit subsystem  202 , gain stage amplifier subsystem  203 , a sample and hold subsystem  204 , buffer subsystem  205  and interface unit  206 .  
         [0033]    Once the waveform  107  is converted into an electro-optical signal, it is forwarded to the signal conditioning subsystem  101  where it is received by both the ALSH subsystem  201  and summation circuit subsystem  202 . The two subsystems  201  and  202  effectively operate together to remove noise, such as ambient light components, from the received waveform  107 . For example, when traversing through tubing  105  containing a fluid medium such as blood and/or outside atmosphere, ambient light can be undesirably mixed into the emitted radiation prior to reception by detector  200  and, therefore, has to be removed prior to the signal analysis stage. To this end, the ALSH subsystem  201  periodically samples the signal to separate and hold the ambient light components from the signal. The sampled ambient light components are then forwarded to the summation circuit subsystem  202  where the separated ambient light components are continuously subtracted from the received signal, thereby generating the desired waveform  107  (i.e., free from noise) from the received signal.  
         [0034]    [0034]FIG. 3 illustrates an exemplary embodiment of the ALSH subsystem  201  circuitry, along with the summation circuit subsystem  202  which includes a pair of resistors  11 , 12 . As shown, the ALSH subsystem  201  circuitry includes the sample-and-hold circuit  312  and the inverted amplifier circuit  311 . The ambient light components of the signal are extracted in the form of a voltage differential and outputted to the inverted amplifier circuit  311  which then converts this voltage into a negative voltage. The negative voltage is then outputted to the summation circuit subsystem  202  and added to the received signal, thus effectively subtracting the ambient light from the received signal.  
         [0035]    Returning to FIG. 2, the waveform signal is then amplified by the gain stage amplifier subsystem  203  and forwarded to the sample-and-hold subsystem  204 . A sample of the waveform signal is periodically collected by the sample-and-hold subsystem  204  according to a desired, predetermined time interval, resulting in faster processing of the waveform signal by the recalibration subsystem  106  via software analysis. The sampled signal is collected with sufficient periodicity so that the interim changes in the waveform signal become negligible. One advantage of the foregoing feature of the present invention is improved analysis response time due to a reduction in the amount of data to be processed. In addition, it should also be noted that the sample-and-hold subsystem  204 , while desirable, is not essential to the overall operation of the present invention.  
         [0036]    Still referring to FIG. 2, the waveform signal is then passed through a protective buffer subsystem  205  and into the interface unit  206 , which forwards the signal to another interface unit  206  at the multi-stage differentiating subsystem  102 . In one embodiment of the present invention wherein multiple radiation waveforms/signals  107  are emitted from one or multiple radiation emitter subsystems, multiple interface units  206  may also be utilized in the signal conditioning subsystem  101  and/or differentiating subsystem  102  for faster transmission and reception of the multiple signals.  
         [0037]    As illustrated FIG. 2, the differentiating subsystem  102  includes interface unit  206 , gas-column detector (GCD) subsystem  260 , gas-bubble detector (GBD) subsystem  270 , and microprocessor  240 . The GBD subsystem  270  further includes a high-pass filter  222 , a first low pass filter  223 , gain stage amplifier  224 , a second low pass filter  225  and gas-bubble detect (GBD) comparator subsystem  226 . The GCD subsystem  260  includes gas-column detector comparator subsystem  230 .  
         [0038]    Referring more particularly to FIG. 2, the waveform signal transmitted from interface  206  in signal conditioning subsystem  101  is received at interface  206  in multistage differentiating subsystem  102  and forwarded to GCD subsystem  260  and GBD subsystem  270 . As described below in greater detail, the two subsystems  260  and  270  analyze the waveform signal to determine the presence and/or absence of any gaseous bubbles or columns in the fluid medium.  
         [0039]    In entering the GBD subsystem  270 , the waveform signal is passed through a high-pass filter  222  to minimize the noise in the signal. Next, the waveform signal is passed through a low-pass filter  223  to filter out changes in the signal considered too rapid in passage to be caused by gas bubbles, such as signal changes in excess of 20 megahertz. The two filters are placed in tandem to effectuate a band-pass filter that allows for passage of a signal having minimal low or high frequencies. FIG. 4 illustrates the circuitry details of one embodiment of a high-pass filter  222  that includes a pair of capacitors placed in parallel and a low-pass filter  223  that includes a pair of resistors placed serially and electrically connecting a pair of capacitors placed in parallel.  
         [0040]    Returning to FIG. 2, the filtered signal is then amplified by the gain stage amplifier  224  and passed through a second low-pass filter  225  to further minimize signal noise.  
         [0041]    Next, the signal is fed to the GBD comparator subsystem  226 . The GBD comparator subsystem  226  analyzes the received signal by comparing the data to adjustable, predetermined signals that indicate the presence and/or absence of gaseous bubbles in the medium and outputs a comparison result to the microprocessor  240 . In one embodiment of the present invention, the presence of a bubble in contrast or saline injected at, for example, more than 800 psi in a conventional 0.078-inch-diameter, 95-durometer, high-pressure tubing, is predetermined as a less than 10 micro-liter fluid displacement resulting in a voltage change greater than or equal to the programmable reference voltage. In this embodiment, the GBD comparator subsystem  226  compares the signal with the adjustable predetermined signal of a 20 milli-volt reference voltage provided by the reference voltage subsystem  480  to determine the presence and/or absence of gaseous bubbles in the medium and outputs a comparison result to the microprocessor  240 .  
         [0042]    [0042]FIG. 4 illustrates the circuitry details of one embodiment of the present invention&#39;s gain stage amplifier  224 , second low-pass filter  225 , and the voltage diode protector  460  that guard against excessive voltage from entering the microprocessor  240 . In one embodiment, as illustrated in FIG. 4, the GBD comparator subsystem  226  is housed within the microprocessor  240 . The reference voltage subsystem  480  generates adjustable predetermined signals, such as for example 20 milli-volts, for the GBD comparator subsystems  226 , 230 .  
         [0043]    In entering the GCD subsystem  260 , the waveform signal is passed through the gas-column detector comparator subsystem  230 . The gas-column detector comparator subsystem  230  analyzes the received signal by applying the appropriate algorithm for the fluid type in the application. The bubble/column determination is programmable within the microprocessor  240  and, in one embodiment, may be a set reference of 20 milli-volts. In one embodiment of the present invention, the presence of a gas column in fluid injected at, for example, more than 800 psi in a conventional 0.078-inch-diameter, 95-durometer, high-pressure tubing is predetermined as a 10 micro-liter or more fluid displacement resulting in a voltage change of equal to or exceeding 20 milli-volts. In this embodiment, the gas-column detector comparator subsystem  230  compares the signal with the adjustable predetermined signal of a 20 milli-volt reference voltage, provided by reference voltage subsystem  480 , to determine the presence and/or absence of gaseous columns in the medium and outputs a comparison result to the microprocessor  240 .  
         [0044]    The microprocessor  240 , which receives the comparison results from both GCD subsystem  260  and GBD subsystem  270 , is an interrupt-driven microprocessor. Flowcharts of the various operations or processes performed by the microprocessor  240  are illustrated in FIGS. 5A and 5B. After initial power-up S 500  and execution of internal operating instructions S 501 , initial predetermined conditions for the detection of various interrupts are accessed for future comparisons.  
         [0045]    In addition, the microprocessor  240  checks to determine whether a predetermined clock cycle has expired S 503 . Expiration of clock cycle S 503  prior to completion of a task prompts the microprocessor  240  to do any or all of the following: interrupt the flow of operations, issue recalibration instructions to the recalibration subsystem  106 , issue a warning to the user, and/or proceed with the next task in the task queue. In addition, as illustrated in FIG. 5B, setting the timer to zero S 503  may prompt the microprocessor  240  to update the state of optical channels S 503   a  and reset the watchdog and generic timers S 503   b.    
         [0046]    The results from the GCD comparator subsystem  226  are then analyzed S 504 . Detection of the presence of a gaseous column S 504   a  in the tubing results in the triggering/setting of a column-detect flag S 504   b . The microprocessor polls the column detect results S 504  for the presence of any flags. If any gaseous columns are found, then the microprocessor executes any or all of the following: interrupt the flow of operations, issue recalibration instructions to the recalibration subsystem  106 , and/or issue a warning to the user.  
         [0047]    The results from the GBD comparator subsystem  226  are also analyzed S 505  by the microprocessor  240 . Detection of the presence of a gaseous bubble S 505   a  in the tubing results in the triggering/setting of a bubble-detect flag S 505   b . The microprocessor polls the bubble detect results S 505  for the presence of any flags. If any gaseous bubbles are found, then the microprocessor executes any or all of the following: interrupt the flow of operations, issue recalibration instructions to the recalibration subsystem  106 , and/or issue a warning to the user.  
         [0048]    In addition, the microprocessor  240  checks to see whether a LED calibration button was pressed S 506 . The LED calibration button is used when a new LED  131  replaces an older unit or when the system is turned off and on. In the event of a new LED  131  replacing an older unit, recalibration is necessary since each manufactured LED  131  has an inherently different emitting spectrum or frequency and, thereby, voltage. A determination of such voltage is necessary to make an accurate reading of the resulting waveform signal for detection of gaseous bubbles and columns. LED calibration S 507  is initiated by repeatedly adjusting the input voltage in the LED S 508  until the emission voltage is found. Thereafter, the new emission voltage is used in place of the older one S 509 . In one embodiment of the present invention, the new emission voltage is stored in a memory medium such as an EEPROM so that the calibration routine does not have to be repeated when the system is turned off and on.  
         [0049]    Other predetermined events or conditions S 510  may also be monitored and analyzed by the microprocessor  240 . As such, if a predetermined event is detected S 510 , then the microprocessor  240  may execute any or all of the following: interrupt the flow of operations, issue recalibration instructions to the recalibration subsystem  106 , and/or issue a warning to the user. Examples of such events include, but are not limited to, presence of tubing, absence of tubing, empty tubing, fluid filled tubing, stagnant air bubbles and/or sensor door state.  
         [0050]    In addition, if the microprocessor  240  determines that a recalibration of the radiation emitter subsystem  100  is required, then the microprocessor  240  issues recalibration instructions in the form of a LED control signal  209 . In one embodiment of the present invention as illustrated in FIG. 2, the LED control signal  209  is sent to the interface unit  206  of the multi-stage differentiating subsystem  102 , is received at interface  206  in the signal conditioning subsystem  101  and forwarded to the recalibration subsystem  106 .  
         [0051]    The recalibration subsystem  106  includes the LED control unit  300  which, in turn, updates the controlling constant current source subsystem  120  of the recalibration changes based on LED control signal  209  received from the multi-stage filtering subsystem  102 . In one embodiment of the present invention, the recalibration instruction may, for example, include commands for the constant current source subsystem  120  to adjust the frequency and/or intensity of the emitted radiation from the LED unit  130 .  
         [0052]    In addition, the microprocessor  240  may similarly send operational instructions, such as actuation timing, and/or data to the ALSH subsystem  210  using ALSH control signal  208 , or to sample-and-hold subsystem  204  using detector sample-and-hold signal  207 .  
         [0053]    In general, based on the foregoing, the system of the present invention may detect a small bolus of air (i.e., on the order of several microliters measured at ambient pressure) when injected at 800-11,000 psi pressure with a flow rate from 0 ml/sec to 50 ml/sec in a 0.078 inch to 0.088 inch inner diameter, 95 durometer, high pressure tubing. As previously described, the system includes an auto-subtraction feature whereby ambient light and high artificial noise are subtracted or removed to prevent signal distortion and/or erroneous results. In addition, the auto-calibration or self-calibration mode of the system of the present invention zeros out effects of mechanical alignment (such as those affecting refraction), transceiver efficiency, tubing/fluid transmittance changes (e.g., tubing material change, fluid viscosity change), tubing/fluid reflectivity changes, tubing/fluid absorption changes, fluid color and other degenerating effects. To further ensure optimum performance, the system also includes a self-test mode that may be used to verify that the various components of the system (e.g., microprocessor, transmitter, receiver, cabling, etc.) are functioning properly.  
         [0054]    Although the system has been described with reference to particular features and components, other designs and configurations including, but not limited to, more accurate detection of bubble speed and size, quantified detection of bubble speed and size, additional system-compatible media and fluid types, media and fluid type detection, fail safe operation, and component/sensor self-test, are also included within the scope of the present invention.  
         [0055]    It is noted that the foregoing different embodiments of the present invention were illustrated separately at times for the purpose of brevity and reader convenience. As such, any process or system using one or more of the disclosed embodiments, including embodiments not specifically disclosed herein, is also included within the scope of the claimed invention.  
         [0056]    Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.