Patent Application
20050272990
The present invention relates to a method and apparatus for non-invasively monitoring the concentration of a target substance in a body. The invention is particularly useful for measuring the concentration, or changes in the concentration, of glucose within the blood of a person, and is therefore described below with respect to that application, but it will be appreciated that the invention could advantageously be used in many other applications.
Frequent monitoring of blood glucose level is critical for those suffering from diabetes. Currently, glucose measurements are generally performed by the individual, by pricking a finger tip and applying a drop of blood to a test strip composed of chemicals sensitive to the glucose in the blood sample. However, this method is very painful and usually inconvenient, particularly when done many times (e.g., 4-7 times) per day as recommended.
It is presently estimated that over 18 million people in the USA suffer from diabetes, and that this number will dramatically increase, to about 24 million in 2010. Considerable research and development has been conducted along many different avenues in an attempt to develop an effective non-invasive glucose monitoring device, as shown by the many technical articles that have been published on this subject and the many patents that have issued. Nevertheless, despite this dramatically increasing need for a method for monitoring blood glucose levels in a non-invasive, painless and convenient manner, and despite the considerable research and development efforts that have been devoted to developing such a device, no such device is yet commercially available, insofar as we are aware, having the accuracy, reliability and repeatability needed for general use.
While this problem is particularly acute with respect to monitoring blood glucose levels, the problem is also present in monitoring the concentration of other constituents of blood, such as cholesterol, or the constituents of urine, or of other biological fluids, industrial fluids, other bodies, etc.
An object of the present invention is to provide a new, non-invasive method of measuring the concentration, or change in concentration, of a target substance within a body. Another object of the invention is to provide a method particularly useful for measuring the concentration, or change in concentration, of glucose within the blood of a person. A further object is to provide novel apparatus for non-invasively measuring the concentration, or change in the concentration, of a target substance, particularly blood glucose.
According to one aspect of the present invention, there is provided a method of non-invasively measuring the concentration, or change in concentration, of a target substance within a body, comprising the operations: activating a pulse source to apply to the body a series of pulses of energy highly absorbable by the target substance, as compared to other substances, to heat the body and to generate therein, by the photoacoustic effect, a series of acoustic waves propagated through an acoustic channel in the body at a frequency corresponding to that at which the energy pulses are applied to the body; detecting the acoustic waves to produce an electrical signal having a frequency corresponding to the frequency of the acoustic waves generated by the photoacoustic effect, and thereby to the frequency at which the energy pulses are applied to the body; controlling the pulse source to change the frequency at which the energy pulses are applied to the body, and thereby the frequency of the acoustic waves, such that the detector detects a whole integer number of wavelengths in the acoustic channel irrespective of variations in the target substance concentration within the body; and utilizing a measurement of the frequency, or change in frequency, of the pulses to produce a measurement of the concentration, or change in concentration, of the target substance.
The “photoacoustic effect” utilized in the above method is well known and has long been used for non-invasively producing various types of measurements, e.g. temperature, pressure, composition, etc. It has also been proposed for use in non-invasively monitoring blood glucose levels, as described for example in U.S. Pat. Nos. 5,348,002, 5,348,003, 5,941,821, 6,833,540, and 6,846,288 Insofar as we are aware, however, a method utilizing this effect has not yet been implemented in a commercially-available device or in a device which has obtained FDA approval.
As will be described more particularly below, the present invention utilizes the “photoacoustic effect”, together with a method, herein referred to as the Frequency-Change by Wavelength-Control (or FCWC) method described in U.S. Pat. No. 6,621,278 (Israel Patent 129651), assigned to the same assignee as the present application, for producing a glucose monitoring device capable of achieving high reliability without a need for frequent recalibration as compared to other known methods.
The FCWC method, as described in U.S. Pat. No. 6,621,278, is capable of measuring with extremely high precision the transit time of an energy wave (compressional or electromagnetic) moving through a transmission channel. The method thus enables measuring, with extremely high precision, virtually any parameter or condition having a known relation to, or influence on, the transit time of movement of an energy wave through a medium. Briefly, this is done by: (a) transmitting a cyclically-repeating energy wave through a transmission channel in the medium; (b) changing the frequency of the transmission according to changes in the monitored condition, while maintaining the number of wavelengths in the transmission channel as a whole integer; and (c) utilizing the changes in frequency of the transmission to provide a measurement of the monitored condition. The change in frequency thus reflects the change in transit time of the energy wave attributed to the monitored condition. This change in transit time may result from a change in the transit velocity, and/or a change in the transit distance of the energy wave through the transmission channel. Further details of the FCWC method are available in U.S. Pat. No. 6,621,278.
When the FCWC method is used in the present invention, the energy wave transmitted through the transmission channel is the acoustic wave generated by the “photoacoustic effect”; and the medium of the channel is the body containing the target substance to be monitored, e.g. glucose in a patient's blood.
Embodiments of the present invention are described below which utilize the FCWC (Frequency-Change by Wavelength-Control) method described in the above-cited U.S. Pat. No. 6,621,278, to produce a precise measurement of the transit time of an acoustic wave through a transmission channel, and thereby of the concentration of the target substance being monitored to the extent that it changes this transit time by a change in the transit velocity and/or the transit distance. This aspect of the present invention utilizes the selective absorption of energy by the target substance, and particularly the “photoacoustic effect”, for generating the acoustic waves used in the FCWC method. Accordingly, the present invention enables changes in glucose concentration to be measured with a high degree of accuracy, reliability and repeatability.
The invention, however, can also be implemented by using the FCWC method without the “photoacoustic effect”, in order to measure the concentration of the glucose (or other target substance) according to the heat generated by the target substance, since such generated heat also changes the transit time of an acoustic wave through an acoustic channel.
According to another aspect of the present invention, therefore, there is a provided a method of non-invasively measuring the concentration of a target substance within a body, comprising: transmitting acoustic waves through an acoustic wave transmission channel in the body to a detector at the opposite end of the acoustic wave transmission channel; applying to the body in the acoustic wave transmission channel energy highly absorbable by the target substance, as compared to other substances, to heat the portion of the body within the acoustic wave transmission channel according to the concentration of the target substance in the body; detecting the acoustic waves in the transmission channel to output an electrical signal having a frequency corresponding the frequency of the acoustic waves transmitted through the channel by the acoustic wave transmitter; controlling the acoustic wave transmitter to change the frequency thereof such that the detector detects a whole integer number of wavelengths irrespective of variations in the target substance concentration with the body; and utilizing the frequency of the detector output signal to produce a measurement of the target substance concentration. The magnitude of the detector output signal may also be used in producing the measurement of the target substance concentration.
An advantage of this aspect of the present invention is that it enables the FCWC method to be used in two independent manners for measuring the concentration of the target substance. Thus, it uses the selective heating by the target substance to produce, by the “photoacoustic effect”, the acoustic waves used in the FCWC method. It also enables the increase in temperature produced by the selective heating to be precisely measured by the FCWC method to provide a measurement of the glucose concentration. In both cases, the FCWC method enables precisely measuring the change in transit time of the acoustic wave, and thereby any condition such as the change in temperature and/or composition, affecting the transit velocity of the acoustic wave. Thus, both techniques can be used in any particular monitoring operation, in order to improve the accuracy and reliability of the final result by executing one technique to extract data from the monitored site useful to determine concentration by the other techniques, or to corroborate the results produced by the other technique.
The present invention also enables a number of acoustic channels to be established through the monitored region for extracting therefrom various types of information which can be used to reduce the extraneous influences, and thereby to provide a more accurate measurement of the concentration of the target substance within the body.
According to another aspect of the present invention, therefore, there is provided a method of non-invasively measuring the concentration, or change in concentration, of a target substance within a body, comprising: transmitting acoustic waves through at least two separate acoustic channels in the body; applying to one of the channels energy which is selectively absorbable by the target substance to thereby heat the respective channel according to the concentration of the target substance therein; and measuring the difference in temperature between that in the one channel with respect to that in the other channel, to thereby provide a measure of the concentration, or change in concentration, of the target substance in the body.
According to still further aspects, the invention also provides apparatus for non-invasively measuring the concentration, or change in the concentration, of a target substance within a body according to the above methods.
In the described preferred embodiments, the pulse source is a laser having a wavelength selectively absorbable by the target substance; and the target substance is a constituent of the blood of a person, particularly the glucose in the person's blood. It will be appreciated, however, that the invention can use other pulse sources and can be used for determining the concentration, or change in concentration, of other target substances within other bodies.
Further features an advantages of the invention will be apparent from the description below.
The invention is described below, for purposes of example only, with respect to the accompanying drawings, wherein:
It is to be understood that the foregoing drawings, and the description below, are provided primarily for purposes of facilitating understanding the conceptual aspects of the invention and possible embodiments thereof, including what is presently considered to be a preferred embodiment. In the interest of clarity and brevity, no attempt is made to provide more details than necessary to enable one skilled in the art, using routine skill and design, to understand and practice the described invention. It is to be further understood that the embodiments described are for purposes of example only, and that the invention is capable of being embodied in other forms and applications than described herein.
The Embodiment of
The apparatus illustrated in
The apparatus illustrated in
The frequency of activation of laser 3, and thereby the frequency of generation of the acoustic waves 5 by the photoacoustic effect, is controlled by detector 7 via a control lines 8 and 9, and a control and measuring system, generally designated 10. System 10 is constructed as described in the above-cited U.S. Pat. No. 6,62,278 and is illustrated in
As shown in
The Control and Measuring System of
Initially, laser 3 is activated via line 9 by an oscillator 11 under the control of a switch 12 until the acoustic waves 5 are received by detector 7. Once these waves are received, switch 12 is opened, so that the received waves are thereafter used for controlling the activation of laser 3, and thereby the generation by the photoacoustic effect of the acoustic waves 5.
As shown in
The output of comparator 13 is fed to a monostable oscillator 14 which is triggered to produce an amplified output signal at each fiducial point in the output signal from detector 7. The signals from monostable oscillator 14 are fed via an OR-gate 15 to control line 9 controlling the activation of laser 3.
It will thus be seen that laser 3 is activated at a frequency such that the photoacoustic waves 5, generated in channel 6 by the absorption of its energy by the targetted glucose TS, is a while integer. The changes in frequency of activation of laser 3, to maintain the number of waves 5 in channel 6 as a whole integer, thus represent a precise measurement of the changes in transit time of the waves 5 from the targetted glucose TS to the detector 7 resulting from the changes in the concentration of the glucose.
The precise measurement of the transit time of the glucose-generated acoustic waves to the detector 7 thus enables a precise measurement to be made of any parameter or condition affecting that transit time. The transit time depends on the transit velocity and the transit distance. Where the transit distance is known or determinable, the measured transit time will be a measure of the transit velocity, and thereby a measure of any factors, such as the heat generated by the glucose, on the transit velocity. Since the heat generated corresponds to the concentration of the glucose, the measured transit time will thus be a measure of the concentration of the glucose at the monitored site.
In addition to heat, other factors, such as changes in composition other than in the glucose concentration, may also affect the transit time of the acoustic wave through channel 6, but such influences for the large part can be determined beforehand or independently, in order to compensate for their influences on the measurements made.
Further details of the construction, use and other possible applications of the system illustrated in
The Embodiment of
The apparatus illustrated in
The inner surface of each of plate 21, 22 carries three vertically-spaced acoustic transducers 31, 32, 33, and 41, 42, 43 respectively, aligned with each other when the sensor assembly 20 is mounted to the person's ear lobe. Thus, as shown in
Plate 21 of sensor assembly 20 also carries a laser 50 on its outer surface in alignment with acoustic transducer 31 on the inner surface of the plate. Transducer 31 is formed with a central opening to accommodate an optical fiber 51 extending from laser 50 to the inner face of plate 21 to be in contact with the outer surface of ear lobe EL.
Laser 50, and the three pairs of acoustic transducers 31-33 and 41-43, respectively, are connected to a control and measuring system 60. System 60 corresponds to the control and measuring system 10 illustrated in
The illustrated sensor assembly 20 defines two further acoustic channels, namely a third channel AC3 within a lower part of the ear lobe between the two transducers 32, 42; and a fourth channel AC4 in the space (air) between the two transducers 33 and 43 below the ear lobe. It will also be seen that the length of acoustic channel AC3 is equal to that of AC4 and is also equal to the sum of the two acoustic channels AC1 and AC2.
Each of the above four acoustic channels AC1-AC4 is controlled by the control and measuring system 60 in the same manner as system 10 described above with respect to
Information Extractable from Channel AC,
As indicated above, the transmitter in acoustic channel AC1 is the targetted glucose TS generating the photoacoustic waves which are detected by acoustic detector 31. Since the transit time of a laser beam from laser 50 to the target substance TS is negligible when compared to the transit time of acoustic waves generated by the glucose, the frequency of activation of laser 50 would be controlled by detector 31, via the control and measuring system 60, in the manner as described above with respect to
The frequency of activation of laser 50, and therefore the frequency of the output signal from detector 31, is thus a precise measurement of the transit time in channel AC1. This frequency can be used to provide information as to the transit distance, i.e., the length of channel AC1 between the target substance TS and its detector 31. It can also be used to provide information as to any conditions influencing the transit velocity of the generated acoustic waves through channel AC1.
The magnitude of the output signal from detector 31 is also a measure of the concentration of the glucose in the monitored site. Since the magnitude measurement is an analog signal, it is inherently less accurate than the frequency-change digital signal produced by the FCWC method described above with respect to
Nevertheless, since the magnitude of the output signal at detector 31 represents a measure of the glucose concentration at the transmitter end of channel AC1, reduced by the transit distance to the detector 31, and by the acoustic impedance of the medium in channel AC1, it can also provide information useful in determining the glucose concentration at the monitored site. Thus, the transit distance is determinable with high accuracy from the other information extractable from all the channels AC1-AC4 as will be described more particularly below. The acoustic impedance within the channel is influenced not only by the composition of the medium (constituted of tissue plus blood, including the targetted glucose constituent), but also by the temperature of the medium of channel AC1. As more particularly described below, the latter influences are also determinable by the information extractable from the monitored site by the activation of a selected combination of the channels AC1-AC4.
Information Extractable from Channel AC2
The transmitter in acoustic channel AC2 is also the targetted glucose TS generating the photoacoustic waves, but in this channel such waves are detected by detector 41. This channel would be activated by the control and measuring system 60 as described above, except that in this case, detector 41 (rather than detector 31) controls the activation of laser 50 to produce a whole integer number of wavelengths within channel AC2 irrespective of variations in the glucose concentration in that channel. It will therefore be seen that, as described above with respect to channel AC1, the frequency of the output signal from detector 41 would be a measure of the transit time of the acoustic signal in channel AC2 (and thereby transit distance and the factors influencing transit velocity in channel AC2); and that the magnitude of the output signal from detector 41 would be a measure of the glucose concentration, diminished by the transit distance and the acoustic impedance of that channel.
Information Extractable from Combined Channel AC1 plus AC2
As indicated above, detector 31 may be operated as an acoustic transmitter to generate acoustic waves propagated through both channels AC1 and AC2 to the detector 41. In such an operation, the acoustic waves would be generated by transducer 31, rather than by the photoacoustic effect described above; and the length of the respective channel would be the sum of the lengths of channels AC1 plus AC2 During this operation, detector 41 would control, via control and measuring system 60, transmitter transducer 31 to maintain a whole integer number of acoustic waves within the combined channel AC1 plus AC2.
Accordingly, during this combined-channel mode of operation of the illustrated apparatus, the frequency of the output signal from detector 41 would be a precise measurement of the transit time of the acoustic wave from transmitter 31 to detector 41, and thereby a measure of the transit distance and/or the transit velocity within this combined acoustic channel. The transit distance, during this operation, is the sum of the transit distances of channels AC1 and AC2 referred to in the above-described operations for extracting information from these two channels when individually activated. The transit velocity, on the other hand, would depend on the factors, including the nature of the medium (tissue plus blood including its glucose constituent), and the temperature of the medium, influencing the transit velocity of the acoustic waves through this combination channel.
It is to be noted that this combination channel (AC1 plus AC2) can be selectively heated by the activation of laser 50. This mode of operation of the apparatus, therefore, permits laser 50 to be energized or not energized during a glucose monitoring operation. Thus, by activating laser 50 merely to heat the medium within the channel (and not to produce the above-described photoacoustic waves), the temperature of the medium within this combination channel will be raised according to the glucose concentration. Therefore, the magnitude of the output signal from detector 41 also provides useful information since it will be a measure of the glucose concentration diminished by the transit distance to the detector 41, and the factors influencing the acoustic impedance in this combination channel.
Accordingly, this combination channel (AC1 plus AC2) may be activated without energizing laser 50 to define a baseline or reference for comparison. This combination channel may also be activated while laser 50 is energized to apply a controlled or measured amount of energy to the medium within this combination channel. Such a two-stage activation of the combination channel thus enables the extraction of information from the monitored site useful in determining the heat influence on the transit time (represented by the frequency of the output signal from detector 41), or on the glucose concentration (represented by the magnitude of the signal output from detector 41), produced by the laser energy absorbed by the targetted glucose within this combination channel.
Information Extractable from Channel AC1
Acoustic channel AC3 does not use the photoacoustically generated waves as the transmitter, as in channels AC1 and AC2, when individually activated, but rather utilizes acoustic transducer 32 as a transmitter for transmitting acoustic waves through channel AC3 for reception by detector 42. Therefore, detector 42 would control, via system 60, the frequency of transducer 32 as described above to maintain the number of wavelengths in channel AC3 as a whole integer. Since the transit distance of this channel is known or can be determined as indicated above, channel AC3 can also be used for extracting information from the monitored site as to conditions influencing the transit velocity or acoustic impedance of the acoustic waves through that channel. The combination channel AC1 plus AC2, however, provides the additional advantage of permitting a two-stage activation of that channel, one stage including heating by the laser, as described above.
Information Extractable from Channel AC4
Acoustic channel AC4, defined by transducers 33 and 43, includes the space (air) below the ear lobe. It may therefore be used for providing reference information for determining the precise transit distances of the other three channels as described above, or for determining the influences on the transit times, the transit velocity, or the acoustic impedance imposed by the ear lobe to the acoustic waves transmitted therethrough via the other channels, as described above.
Using the Laser to Produce Acoustic Waves by the Photoacoustic Effect
Acoustic channel AC1 could be activated by utilizing detector 31 to control the frequency of activation of laser 50 in order to produce a whole integer number of photoacoustic waves in channel AC1 by the photoacoustic effect as described above. In this case, the frequency of activation of the laser would be influenced by the transit distance (length of channel AC1) and the transit velocity through channel AC1. Thus, the frequency of the output signal from detector 31 would be a precise measurement of the transit time of the acoustic wave through channel AC1. The magnitude of the output signal from detector 31 would be a measure of the amount of laser energy absorbed by the targetted glucose, and thereby a measure of the glucose concentration as diminished by the transit distance and acoustic impedance within channel AC1.
With respect to the measured transit time as represented by the frequency of the output signal from detector 31, this transit time would depend on the transit distance and the transit velocity of the acoustic wave within channel AC1.
The transit distance is the length of channel AC1. This can be determined with extremely high accuracy from the other information extractable from the monitored site via the other channels, as described herein.
The transit velocity is influenced by the physical nature of the medium in channel AC1 and also by the temperature of the medium in that channel. The medium is the portion of the ear lobe between transducers 31 and 41. It is constituted mainly of tissue and blood containing the targetted glucose whose concentration is to be determined. Information regarding the influence of the targetted glucose, of the tissue, and of the temperature, on the transit velocity of the acoustic waves within channel AC1 is extractable from the other channels by independently performed tests, such as to enable assessing the magnitude of these influences on the transit velocity, and thereby on the glucose concentration measurements.
Acoustic channel AC2 could be similarly activated by using detector 41 for controlling laser 50. The frequency and magnitude of this output signal from detector 41 would provide similar information as in channel AC1 with respect to the factors in influencing the transit velocity of the acoustic waves through that channel.
The combined channel (AC1 plus AC2) could also be independently activated, by using transducer 31 as a transmitter and transducer 41 as a detector, and controlling the activation of detector 31 by the output signal from detector 41. Laser 50 could be selectively operated to influence the transit velocity by the selective heating of the combined channel as described above. Such operation would also enable extracting from the monitored site information useful with the other information for determining the medium and/or heat influences on the transit velocity.
Channel AC3 can be similarly activated for extracting useful information from the monitored site. Thus, by using transducer 42 as a detector for controlling transducer 32 used as a transmitter, the information obtainable from channel AC3 would depend on the transit distance and transit velocity in that channel. Since the transit distance AC3 is equal to the sum of the transit distances in the two channels AC1 and AC2, and since the transit velocity in channel AC3 is influenced primarily by the ear lobe tissue and not by the heat generated by the targetted glucose upon activation of the laser 50, information as to these influences is also obtainable from channel AC3. Such information can be used with the information obtainable when activating the other channels to assess the magnitude of these influences on the transit velocity, and thereby on the determination of the concentration of the glucose in the monitored site.
Acoustic channel AC4, may also be activated to provide further useful information enabling a precise measurement of the length of channel AC4 and thereby of the lengths of channel AC1, AC2 and AC3. Channel AC4 is not affected by the heat generated by target substance TS or by the ear lobe tissue medium, influencing the transit velocity in the above-described channels AC1-AC3. Accordingly, the information obtainable from channel AC4 could also be useful to assess the medium and/or heat influences on the transit velocity, and thereby to enable a more precise measurement of the glucose concentration to be made.
Using the Laser Merely as a Heat Source to Heat the Monitored Site
The apparatus illustrated in
Thus, the FCWC (Frequency-Change by Wavelength-Control) method described above with respect to
The frequency of transmitter 31 would, therefore, depend on the transit distance and transit velocity between transmitter 31 and detector 41. The transit distance is known, or determinable as described above. The transit velocity varies with the heat generated by the glucose TS absorbing the laser energy. Since the heat so generated depends on the concentration of the glucose, the difference in frequency of transmitter 31 to maintain the number of wavelength as a whole integer in the combination channel AC1 plus AC2 (a) when this channel is activated with the activation of the laser, and (b) when this channel is activated without the activation of the laser, would be a measure of the heat generated within that channel by the glucose, and thereby a measure of the concentration of the glucose in the monitored site.
Such a measurement of the glucose concentration is not dependent on the photoacoustic effect. It therefore can be used alone for determining glucose concentration. Alternatively, it can be used together with above-described method utilizing the photoacoustic effect in order to corroborate the results produced by that measurement, or to extract information from the monitored site useable to increase the reliability and repeatability of the measurements based on the photoacoustic effect.
It will further be seen that another independent measurement of the glucose concentration can be made using the laser merely to heat the monitored site by utilizing the magnitude, rather than the frequency, of the output signal from detector 41. In that case, the magnitude of the output signal would be a measure of the glucose concentration, reduced by the transit distance influence and the acoustic impedance influence to detector 31, as described above. This can be done by activating the combined channel AC1 plus AC2 (a) without activating the laser, and then (b) while activating the laser to introduce a measured amount of energy converted to heat by the glucose according to its concentration, and comparing the magnitude of the detector output for both cases. Such an independent measurement of the glucose concentration, although less precise than the measurement based on frequency change, could nevertheless be made to corroborate a frequency-change measurement, and/or to extract from the monitored site information useful in increasing the precision and repeatability of the measurement made by the frequency-change method.
The Embodiment on
In all other respects, the apparatus illustrated in
The Embodiment of
Thus, as shown in
In one operation, the three transducers 71-73 may be used as detectors for detecting the so-generated acoustic waves. Thus, a separate acoustic channel is established between the targetted glucose TS and each of the three detectors 71-73. The illustrated apparatus further includes a control and measuring system 80, similar to system 10 (
Each of the detectors 71-73, which defines a separate acoustic channel with the targetted glucose TS, may control the laser 76, via control system 80, such that the frequency of the acoustic waves generated in the respective channel is a measure of the transit time of the acoustic wave in that channel. As described above, the transit time is dependent on the transit distance and the transit velocity in the respective channel. Since the locations of the three detectors 71-73 are known relative to each other, the transit distance (e.g., the length of the respective channel) can easily be determined from the data extracted from the three channels of the monitored site. As also described above, the transit velocity in the respective channel is influenced by the nature of the medium (e.g., tissue plus blood including the glucose), and the temperature of the medium. By using three (or more) such channels as illustrated in
In another operation, one transducer (e.g., 72) could be used as a transmitter of acoustic waves (instead of the targetted glucose by the photoacoustic effect) to the other transducer, and the laser could be used merely to selectively heat the respective acoustic channels. Thus, by selectively activating the two channels via the above-described FCWC method, with and without activating laser 76, information may be obtained useful in determining the influences of the heat and the channel medium on the transit velocity of the acoustic waves at the monitored site.
The Embodiment of
The two monitoring sites in the embodiment of
For purposes of example,
For example, one sensor assembly may be operated according to the above-described “photoacoustic mode”, wherein the laser is used to produce acoustic waves by the photoacoustic effect, while the other sensor assembly is operated according to the above-described “heating mode”, wherein the laser is used merely to heat the monitored site. Another option would be to activate the laser of one sensor assembly in order to generate heat by the selective absorption of the laser energy according to the glucose concentration at the respective site, while the laser in the other sensor assembly is not energized. Thus, the results of the test in the latter site could be used as a baseline or reference for the test results produced in the former site in assessing the influence of the heat absorbed by the glucose in the former site, which absorbs heat in accordance with its concentration.
Many of the other options described above with respect to a single site would also be available in the two-site arrangement of
As indicated above, various monitoring sites could be used. If an ear lobe is used for the monitoring site, the electrode assembly could be constructed as a separate unit for mounting to the ear lobe, whereas the control and display system could be in a separate unit wire-connected to the sensor unit. Another alternative would be to have the control and display unit incorporated in a wristband for mounting on the wrist of the person, and to have wireless communication with the sensor unit mounted on the person's ear lobe.
It will be appreciated that in all of the above-described embodiments, the laser wave length is selected according to the target substance of interest. Thus, if the target substance of interest is blood glucose, the laser wave length would be selected to have a frequency, or combination of frequencies, to generate the maximum level of acoustic waves by the photoacoustic effect in glucose, as described for example in the above-cited US patents. It will be further appreciated that excitation means other than lasers can be used, e.g. microwaves, X-rays, ion-beams, etc, and that other target substances may be monitored, such as other blood constituents, urine constituents, constituents of other biological fluids, and constituents of industrial fluids, solid bodies, etc.
Therefore, while the invention has been described with respect to several preferred embodiments, it is to be expressly understood that these are set forth merely for purposes of example, and that many other variations, modifications and applications of the invention may be made.
| Number | Date | Country | Kind |
|---|---|---|---|
| 166760 | Feb 2005 | IL | national |
The present application is a continuation-in-part of U.S. patent application Ser. No. 10/844,398, filed May 13, 2004, and also includes subject matter of Israel Patent Application 166,760 filed Feb. 8, 2005, the priority date of which is also claimed.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10844398 | May 2004 | US |
| Child | 11125189 | May 2005 | US |
