Abstract:
A system and method for measuring glucose levels in a user&#39;s blood without having to draw a blood sample. A wave energy source emits wave energy. A modified ceramic coaxial resonator is provided that receives the wave energy and produces a frequency oscillation. An opening is formed in a conductive layer surrounding the ceramic coaxial resonator. Skin tissue is pressed against the opening. The sample tissue alters the frequency oscillation created by the ceramic coaxial resonator. At least some of the altered frequency oscillation is indicative of blood glucose levels within the sample tissue.

Description:
BACKGROUND OF INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    In general, this invention relates to blood glucose measuring devices and techniques. More particularly, this invention relates to systems and methods that can measure blood glucose in the body without the need to draw a blood sample. 
         [0003]    2. Prior Art Description 
         [0004]    Diabetes is a chronic disease without a cure. Over twenty five million people in the United States of America have diabetes. Diabetes is the seventh leading cause of death in the United States. Currently, diabetes is estimated to cost the United States health care system over one-hundred billion dollars annually. 
         [0005]    Diabetes creates high blood glucose levels due to a deficiency of insulin production and action. This failure leads to hyperglycemia. Persistent hyperglycemia causes a variety of serious symptoms and life threatening long term complications such as dehydration, diabetic coma, cardiovascular disease, and poor blood circulation. 
         [0006]    Many diabetics are required to take insulin in order to control the glucose levels in their blood. However, having insulin levels in the blood that are too high are just as dangerous as having insulin levels in the blood that are too low. Consequently, it is critical that diabetics who use insulin precisely monitor the level of glucose in their bodies. 
         [0007]    The most common and accurate glucose monitoring techniques require that a blood sample be drawn from the body. This is typically done by pricking the skin with a needle or lancet to obtain a small droplet of blood. The blood is placed upon a chemically treated strip of paper. The strip of paper is then placed in a glucometer, which tests the blood and provides a glucose level reading. 
         [0008]    Pricking the skin can be painful. Areas of the skin can also experience increased sensitivity to pain if those areas are repeatedly pricked over long periods of time. Furthermore, many diabetics have blood circulation problems. As a result, these diabetics can only draw blood from certain parts of the body, such as the fingertips, where good blood flow remains. Unfortunately, the areas of the body that have good blood flow often correspond to the areas of the body that have a high concentration of nerve endings, thus increasing the pain associated with obtaining such a blood sample. The result often is that diabetics are deterred from testing and consequently test their blood glucose levels far less often than they should. 
         [0009]    For the reasons stated above, there has been a long standing need for a glucose monitoring device that can detect the level of glucose in a diabetic without the need for a drawn blood sample. In the prior art, certain devices have been produced that claim that they can meet this need. For instance, in U.S. Patent App. Pub. No. 2010/0112614 to Axelrod, entitled Coupled Antenna Impedance Spectroscopy, a methodology is presented for measuring blood glucose levels. However, the technique does not produce accurate results in comparison to common blood drawn testing techniques. More importantly, such methodologies require the use of a spectroscope. Consequently, such testing systems are limited to use in hospitals and labs that have spectroscopes. Such testing systems cannot be made into low-cost portable devices using known technologies. 
         [0010]    In U.S. Pat. No. 9,078,606, to Bharj, the Applicant presented an earlier design for a passive glucose monitoring system that measures blood glucose levels using a microwave resonance chamber. However, in order for the system to function properly, a mass of skin has to be pressed against a hole in the microwave resonance chamber so that some of the skin and body tissue bulges through the hole and into the microwave resonance chamber. This requirement mandates that the resonance chamber be relatively large in order to receive the tissue needed for an accurate test. As such, the system cannot be miniaturized to any significant degree without causing adverse affects to the monitoring accuracy. 
         [0011]    Many diabetics carry insulin pumps that automatically pump insulin into the bloodstream at a selected rate. Insulin pump systems are designed to be as small and discrete as possible so that the systems can be comfortably worn without being seen. Insulin pump systems typically rely upon a person&#39;s average blood sugar levels, as monitored over time. The problem is that many diabetics fluctuate from their averages as they rest, exercise, eat, and drink. Insulin pumps can be made much more effective if the system were capable of constantly monitoring blood sugar levels in real time. In this manner, the system could inject insulin only when insulin was needed. To monitor blood levels in this manner, a passive blood monitoring system is required that does not require blood contact and can be made small enough so as to not to increase the size of insulin pumps to any significant degree. 
         [0012]    This need is met by the present invention as described and claimed below. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention is a system and method for measuring glucose levels in a user&#39;s blood without having to draw a blood sample. Rather, the glucose level of the blood is tested in a non-invasive manner through the skin using RF energy waves in the ISM frequency bands that are passed through a modified ceramic coaxial resonator. To test a user&#39;s blood, an RF electromagnetic (EM) energy source is provided that has an RF source frequency. The RF source frequency is determined by the modified ceramic coaxial resonator. The RF source frequency is selected to be a quarter wavelength, or odd multiple wavelength, of the modified ceramic coaxial resonator being used. The modified ceramic coaxial resonator has a central hollow surrounded by a body of dielectric material that can have a square or round cross-section. The dielectric material is covered with a conductive sheathing. One or more slots are formed in the conductive sheathing that exposes the dielectric material. 
         [0014]    The wave energy source causes the modified ceramic coaxial resonator to produce a frequency oscillation. Contact of skin tissue with the dielectric material exposed in the slot on the modified ceramic coaxial resonator alters the frequency oscillation in correlation to glucose levels in the skin and surrounding tissue. 
         [0015]    Circuitry is provided that converts the frequency oscillation into a display signal. As such, glucose levels can be read instantly and/or continuously from the display after merely touching the modified ceramic coaxial resonator with a segment of skin that has blood tissue underneath. No drawing of blood is required. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    For a better understanding of the present invention, reference is made to the following description of exemplary embodiments thereof, considered in conjunction with the accompanying drawings, in which: 
           [0017]      FIG. 1  shows a perspective view of an exemplary embodiment of a blood glucose monitor; 
           [0018]      FIG. 2  is a block diagram schematic illustrating the functional components of the present invention blood glucose monitor; 
           [0019]      FIG. 3  is a perspective view of a modified ceramic coaxial resonator utilized by the present invention blood glucose monitor; 
           [0020]      FIG. 4  is a cross-section of the embodiment of  FIG. 3  vied along section line  4 - 4 ; 
           [0021]      FIG. 5  is a top view of a first alternate embodiment of a modified ceramic coaxial resonator; 
           [0022]      FIG. 6  is a top view of a second alternate embodiment of a modified ceramic coaxial resonator; 
           [0023]      FIG. 7  is a block flow diagram illustrating the methodology of performing a test using the present invention blood glucose monitor; 
           [0024]      FIG. 8  is an exemplary view of an insulin pump assembly containing the present invention blood glucose monitor; 
           [0025]      FIG. 9  shows a body with straps that illustrates positions on the body where the present invention blood glucose monitor can be attached; and 
           [0026]      FIG. 10  shows an alternate embodiment of the modified ceramic coaxial resonator adapted to receive and analyze a liquid sample. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. References to the invention described are for illustrations and understanding and should not be taken as limiting. 
         [0028]    Although the present invention glucose monitoring sensor and system can be embodied in many ways, only a few embodiments of the sensor and system have been selected for illustration and discussion. The illustrated embodiments, however, are merely exemplary and should not be considered a limitation when interpreting the scope of the claims. 
         [0029]    Referring to  FIG. 1  in conjunction with  FIG. 2 , a blood glucose monitor  10  is illustrated. The blood glucose monitor  10  is very small and can be embodied in a unit only slightly thicker than a credit card. In this manner, the blood glucose monitor  10  can be readily carried in the wallet, pocket, or purse of a diabetic. 
         [0030]    The blood glucose monitor  10  has an interface surface  12 . Positioned upon the interface surface  12  is a test structure  14  upon which a person places his/her fingertip  16  or another segment of body tissue. The test structure  14  includes a modified ceramic coaxial resonator  20  and inert supports  18  that surround the modified ceramic coaxial resonator  20 . The inert supports  18  ensure that the modified ceramic coaxial resonator  20  is protected from lateral contact that may dislodge or otherwise damage the electrical and waveguide connections that lead to the modified ceramic coaxial resonator  20 . The test structure  14  has an open top  21  that exposes the top surface  22  of the modified ceramic coaxial resonator  20 . The modified ceramic coaxial resonator  20  can be very small and has a preferred length of less than 1.5 centimeters and a preferred width of less than 0.5 centimeters. As such, the open top  21  need only be a few square millimeters in area, and can a variety of shapes. In this manner, the open top  21  is far smaller than the average person&#39;s fingertip. Accordingly, if a person were to place his/her fingertip  16  or another segment of body tissue over the open top  21 , the body tissue would easily cover the open top  21  and the tissue would contact the top surface  22  of the modified ceramic coaxial resonator  20 . 
         [0031]    The dimensions of the modified coaxial resonator  20  regulate its frequency of oscillation. The modified coaxial resonator  20  is sized in relation to the RF source frequency being used so that the RF source frequency is a quarter wavelength, or a multiple of the quarter wavelength, of the resonance frequency of the modified coaxial resonator  20 . 
         [0032]    The portion of the body tissue that physically touches the top surface  22  of the modified ceramic coaxial resonator  20  is considered the test sample for the blood glucose monitor  10 . Since only a small portion of a person&#39;s fingertip  16  touches the modified ceramic coaxial resonator  20 , it will be understood that the size of a person&#39;s fingertip  16  does not matter. Rather, regardless of whether the user is large or small, thin or fat, the test sample that actually touches the modified ceramic coaxial resonator  20  remains relatively constant. Microwave frequencies around 1 GHz penetrate the body by a few centimeters. In the present invention, microwave power levels of only 1 mW are needed. As such, the microwave exposure is low-power and non-ionizing. 
         [0033]    The modified ceramic coaxial resonator  20  has a high degree of temperature stability at the frequency of oscillation. However, in requirements where temperature stability requirements are very high, a second similar resonator can be incorporated as a reference and circuits can be designed to negate any difference in temperature. 
         [0034]    In  FIG. 2 , the small amount of body tissue that touches the modified ceramic coaxial resonator  20  is shown as the sample tissue  24 . The sample tissue  24  consists primarily of skin, behind which is blood and muscle tissue. As has been previously stated, the size of the sample tissue  24  remains very consistence across a wide patient population. The sample tissue  24  touches the top surface  22  of the modified ceramic coaxial resonator  20 . 
         [0035]    Referring to  FIG. 3  and  FIG. 4  in conjunction with  FIG. 2 , it can be seen that a first embodiment of a modified ceramic coaxial resonator  20  is shown that has a rectangular structure with a ceramic dielectric body  26 . An inner hollow  28  extends through the ceramic dielectric body  26 . The exterior of the ceramic dielectric body  26  is covered with a conductive sheathing  30 , such as a plating of a silver alloy. On the top surface  22  of the modified ceramic coaxial resonator  20 , the conductive sheathing  30  is removed along a slot  32 . As such, the ceramic dielectric material  26  is directly exposed within the slot  32 . When the sample tissue  24  touches the top surface  22  of the modified ceramic coaxial resonator  20 , the sample tissue  24  contacts the slot  32  and contacts the exposed ceramic dielectric material  26  that is exposed by the slot  32 . Consequently, the sample tissue  24  is not shielded by the conductive sheathing  30 . As such, the sample tissue  24  is exposed to the electromagnetic fields created by the modified ceramic coaxial resonator  20 . 
         [0036]    The dimensions of the slot  32  are not as important as its exposed area. Many different shaped slots can be used. Slots of generally equal area will provide similar results. In  FIGS. 3 and 4 , a single oblong the slot  32  is used. This single slot  32  can have a variety of peripheral shapes. Likewise, as is shown in  FIG. 5 , the exposed area can be contained in two separate slots  32   a ,  32   b  that have a combined area equal to that of the single slot  32  in  FIG. 3 . Likewise, as is indicated in  FIG. 6  a matrix of exposed slots  32   c  can be provided. 
         [0037]    Returning to  FIG. 2  and  FIG. 3 , it will be understood that regardless to the shape and number of exposed slots on the modified ceramic coaxial resonator  20 , a wave energy source  34  emits wave energy into the modified ceramic coaxial resonator  20 . The modified ceramic coaxial resonator  20  produces an oscillation frequency from the wave energy that is dependent upon the bias potential and the physical characteristics of the modified ceramic coaxial resonator  20 . In the preferred embodiment, wave frequencies in the ISM (Instrument, Scientific and Medical) bands are used. Preferably, the wave energy source  34  is a high Q factor microwave source. Such a microwave source provides a very stable (UHF) signal within environmental conditions. However, a millimeter wave (EHF) transmitter can also be used effectively. 
         [0038]    The wave energy source  34  uses a temperature stable crystal oscillator  36  in a phase locked loop, and an emission control circuit  38  to ensure that the wave energy source  34  provides a stable frequency regardless of changes in temperature, humidity, and battery strength. 
         [0039]    The dimensions of the modified ceramic coaxial resonator  20  are known, as is the resonance frequency it normally produces when not in contact with a secondary object. Consequently, when nothing touches the slot  32  on the modified ceramic coaxial resonator  20 , the oscillation frequency produced remains essentially constant. However, when the sample tissue  24  touches the slot  32  on the modified ceramic coaxial resonator  20 , the presence of the sample tissue  24  loads the modified ceramic coaxial resonator  20  and changes the oscillation frequency. As has been previously stated, the sample tissue  24  consists primarily of skin and blood. The skin has a fairly consistent dielectric constant that varies very little from day to day and person to person. However, it has been found that the effect of the blood on the oscillation frequency of the modified ceramic coaxial resonator  20  is significant. The dielectric constant of the blood can vary between 30 and 74 depending upon the wave frequency being used. Of the many components contained in human blood, it has been discovered that the level of glucose contained in the blood has a significant effect on the dielectric constant attributed to that blood. Other blood chemistry elements, such as iron, tend to be constant in most individuals. 
         [0040]    Since contributing elements to the dielectric constant of the sample tissue  24 , such as skin and non-glucose blood chemistries, tend to be constant in any one diabetic patient, the changes in the oscillation frequency created by these elements can be considered constant background noise and can be electronically filtered. What is left is a variation in the oscillation frequency that is caused primarily by the glucose level of the blood flowing through the sample tissue  24 . The changes in the oscillation frequency are significant enough to detect changes in blood glucose levels corresponding to at least one milligram per deciliter. This level of accuracy mimics that of traditional glucometers that test drawn blood samples. 
         [0041]    The oscillation frequency of the modified ceramic coaxial resonator  20  is detected in a traditional manner, wherein the oscillation frequency corresponds to an analog signal. The analog signal is processed by a central processing unit  40  and is converted into a voltage signal. The voltage signal is shown as a number on a display  42  on the interface surface  12  of the blood glucose monitor  10 . The change of frequency into voltage can be accomplished by means of digital phase locked loop, analog phase locked loop or frequency discriminators in the control circuitry. 
         [0042]    The central processing unit  40  is also connected to user controls  44  on the interface surface  12  of the blood glucose monitor  10 . The user controls  44  include an on/off control as well as input controls that enable a user to calibrate the blood glucose monitor  10  as well as initiate various preprogrammed subroutines. 
         [0043]    An optional computer port  46  may also be coupled to the central processing unit  40 . The computer port  46  allows the central processing unit  40  to download data and/or upload data from an outside computer. In place of a physical computer port  46 , the system may transmit and receive data via BlueTooth, WiFi and other wireless communication techniques. 
         [0044]    The blood glucose monitor  10  is initially calibrated at the factory using blood samples from diabetic patients which are analyzed both by blood laboratories and by measurements using the blood glucose monitor  10 . A calibration correlation is conducted and stored in an EEPROM or similar memory device within the control circuitry. 
         [0045]    Referring now to  FIG. 7  in conjunction with  FIG. 2 , the method of operating the blood glucose monitor  10  is explained. As is indicated by Block  50 , a user initiates the blood glucose monitor  10  by pressing the appropriate user control  44 . Once initialized, a user places a tissue sample  24  over the slot  32  atop the modified ceramic coaxial resonator  20 . See Block  52 . The blood glucose monitor  10  automatically conducts a test by seeing how the sample tissue  24  touching the slot  32  affects the oscillation frequency produced by the modified ceramic coaxial resonator  20 . See Block  54 . The changed oscillation frequency is converted into a numerical display signal, which is presented on the display  42 . See Blocks  56  and  58 . The entire test sequence should take less than ten seconds. The glucose test monitor  10 , therefore, enables users to test their blood glucose levels many times a day without having to draw blood samples. 
         [0046]    Referring to  FIG. 8 , an alternate embodiment of the present invention glucose test monitor is shown. In this embodiment, the glucose test monitor of the present invention is integrated into the hardware and software of an insulin pump  60 . The insulin pump  60  has a primary unit  62  that is worn on the belt. The primary unit  62  contains stores of insulin, a pump and the various electronics needed for operation. A tether  64  of tubes and wires runs to an injection head  66 . The injection head  66  has a needle  68  that pierces the skin and enables insulin to be injected into the patient. The injection head  66  is held onto the skin of the patient with an adhesive pad  70 . 
         [0047]    The insulin pump  60  is modified. A relief  72  is formed in the adhesive pad  70  of the injection head  66 . Under the relief  72  is positioned a modified ceramic coaxial resonator  20   b . When the injection head  66  is attached to a person&#39;s skin, the modified ceramic coaxial resonator  20   b  is brought into contact with the skin. The modified ceramic coaxial resonator  20   b  can then monitor blood sugar levels in the manner previously described. The blood sugar levels being read are utilized by the primary unit  62  of the insulin pump. If blood sugar levels are high, then the insulin pump  60  will inject the appropriate dose of insulin. If sugar levels are low, the insulin pump  60  will refrain from injecting insulin. 
         [0048]    The use of the modified ceramic coaxial resonator  20   b , therefore, enables the insulin pump  60  to become self monitoring. This makes the insulin pump  60  more effective and less likely to cause insulin overdoses. 
         [0049]    In addition to being used in conjunction with an insulin pump, the present invention can be used as simply as a continuous glucose monitoring system. As us indicated in  FIG. 9 , the system can have a strap  80  that holds the system against the user&#39;s skin. The area of the skin is not of much importance. As such, the system can be worm around the leg, the arm, or the torso. 
         [0050]    It will also be understood that the present invention glucose monitoring system can be used to test glucose in material other than blood-rich body tissue. Referring to  FIG. 10 , it can be seen that a small receptacle  90  can be built over the slot  32  in the modified ceramic coaxial resonator  20 . The receptacle  90  is preferably made of quartz and is capable of holding a small volume of liquid  92 , such as urine saliva or blood. The presence of the liquid will affect the resonance frequency of the modified ceramic coaxial resonator  20  in the same manner as has been previously described. 
         [0051]    It will be understood that the embodiments of the present invention that are illustrated and described are merely exemplary and that a person skilled in the art can make many variations to those embodiments. For instance, the overall shape of the blood glucose monitor and/or insulin pump are a matter of design choice. All such embodiments are intended to be included within the scope of the present invention as defined by the claims.