US 20050113656 A1
The present invention discloses a novel, user-wearable system for monitoring the oxygen concentration, or oxygenation trend, in the tissue of a subject undergoing aerobic stress. The system comprises a lightweight detector, worn against the skin surface of the subject, at the site being monitored. The system further includes wearable power pack and display means for displaying information indicative of the metabolic condition of the region being monitored. The detector preferably employs a continuous wave spectrophotometer having one or more sources of electromagnetic radiation with wavelengths between about 760 and 800 nanometers directed into the tissue of the subject. The detector utilizes photon migration to detect the portion of the transmitted radiation arriving at an adjacent skin region. The present invention also discloses methods for displaying the aerobic metabolic condition of a subject.
40. A tissue oximeter comprising a support, a detector fixed to the support and a light source mounted in an adjustable manner to the support to enable selection of the spacing between light source and detector for adjusting the mean depth of tissue to which the oximeter responds.
41. A tissue oximeter in combination with means connected to receive tissue oxygen readings from the oximeter, determine the rate of change of said readings, said rate of change serving as a quantifiable indication of the state of the metabolic process of the tissue.
42. The oximeter of
43. An oximeter disposed on an endoscope, catheter, guidewire or the like for insertion via a body passage to internal tissue, and including means such as an inflatable balloon to press the oximeter sensor against the localized tissue of interest.
44. The oximeter of
45. The oximeter of
46. The oximeter of
47. The oximeter of
48. The oximeter of
49. The oximeter of
In one aspect, the present invention relates to wearable apparatus for noninvasive determinations of the concentration of oxygen in a specific target region of tissue. More specifically, the present invention discloses a user-wearable system for monitoring the oxygen concentration, or oxygenation trend, in the tissue of a subject undergoing aerobic stress, such as an exercising person.
The increasing popularity of all forms of exercise over the last several decades has also lead to an increased interest in the measurement of individual athletic performance. However, at the present time, athletes are limited to obtaining heartbeat and blood pressure data while they are exercising. Although of some use, these data do not reflect peripheral circulatory capacity or the oxygenation state of specific muscle tissue.
In order to measure oxygen delivery to the capillary bed of the muscles, an athlete must be tethered to electrocardiogram apparatus and have blood samples drawn while running on a treadmill. These are essentially operating room apparatus and procedures, which do not simulate the actual conditions of exercise. The measurement of aerobic efficiency by analyzing the oxygenation state of a particular muscle while exercising is important due to a variety of reasons. For example, as a casual jogger strives to become a marathon runner, the efficiency at which he/she uses oxygen can severely impact performance; data reflecting the utilization of oxygen can provide information which allows an athlete to change pacing strategies or otherwise adjust their activity to produce better results. Other athletes, such as swimmers, cyclists and rowers would also find this information useful for evaluating performance. However, the use of blood oxygenation data is not limited to competitive athletes; even geriatrics who undergo mild aerobic exercise to maintain and improve their health can benefit from data concerning the changes in blood oxygenation brought about by exercise or other activity. Other animals, such as racehorses, can also benefit from this type of performance data. By measuring the oxygen delivery to the muscles, both the quality of training and the natural ability to exercise may be evaluated.
In addition to monitoring and maximizing athletic performance, information pertaining to the delivery of oxygen to the limbs and the brain is important in military and space applications where changes in gravity and other stresses may result in fatigue, and ultimately, blackouts.
Although apparatuses which measure the oxygenation content of blood using data collected from a fingertip or ear lobe are available, these devices do not actually measure the oxygenation state of nearby muscle groups or the brain. To monitor athletic performance, or the condition of exerted muscles, data collection must be performed at the site of interest. For example, runners will wish to be provided with this information during a race, not in a laboratory. Therefore, for an apparatus measuring the metabolic condition of an athlete to be truly useful, a rugged, lightweight, user-wearable system must be provided.
One method by which the oxygen level in a muscle may be measured is tissue spectrometry. For example, red and near-red light, having wavelengths between about 600-800 nanometers (nm), will harmlessly penetrate body tissues. As the light penetrates the tissue, it migrates and is absorbed by deoxygenated hemoglobin in small blood vessels. Normally, tissue receives oxygen from hemoglobin contained in red blood cells, which circulate in the major blood vessels and eventually into the capillary bed, supplying muscle tissue with oxygen. Aerobic activity can cause the level of oxygen use to rise, causing a commensurate rise in the level of deoxyhemoglobin which is compensated for by increased blood flow in trained individuals. Near-red light is absorbed by tissue that is not receiving as much oxygen as the surrounding tissue due to increased levels of deoxyhemoglobin in less trained individuals. Thus, by determining the amount of incident radiation absorbed, the oxygenation state of a specific area of tissue, and the training level of an individual, can be determined.
The present invention also relates to a study of the linkage between cerebral activity and oxygen delivery and oxidative metabolism in the brain tissue. During a brain activity, blood flow can be studied using PET or NMR. Faster electrical and magnetic responses can be measured using EEG and MEG. While these techniques eventually might be able to provide examination and screening for neuronal deterioration and/or deterioration of brain function, they are relatively expensive and not suitable for emergency treatment situations wherein the diagnostic equipment should be taken to a patient. Optical techniques, on the other hand, might provide a suitable, cost effective alternative for examination and screening of a tissue of an organ.
The present invention provides a novel, wearable system for determining the metabolic condition of an aerobically stressed portion of the muscle tissue of an exercising person. The system comprises a lightweight rugged detector, worn against the skin surface of the subject, adjacent to the muscle being monitored. The system of the present invention thus minimizes any performance impairment. The preferred system further comprises a wearable power pack and a wearable display means for displaying information indicative of the aerobic metabolic condition of the region being monitored. In a preferred embodiment intended for use while running or engaged in similar athletic activities, the display is worn on the wrist and displays information from a leg-mounted detector. In another embodiment, intended to provide information to coaches, a telemetry system is employed to transmit a signal carrying the data from the detector to a remote location, for processing and display.
The detector of the present invention preferably employs a continuous wave spectrophotometer having one or more sources of electromagnetic radiation with wavelengths between about 760 nanometers and about 800 nanometers directed into the tissue of the subject. The detector is efficiently coupled to the body tissue and utilizes the principle of photon migration to detect the portion of the transmitted radiation arriving at an adjacent skin region.
The present invention also discloses methods for displaying the aerobic metabolic condition of a subject. The percentage of deoxyhemoglobin in the blood of the subject is determined, and a signal representative of this percentage is converted into a graphic representation. The display may preferably be a digital display, a bar graph or a series of deoxyhemoglobin levels, placed on a time scale.
It is an object of the present invention to provide methods and apparatus which allow a rapid determination of the oxygenation state of tissue, such as muscle tissue, located beneath the surface of the skin of a subject, such as an athlete, without requiring the subject to be tethered or physically connected to laboratory or operating room monitoring equipment.
It is also an object of the present invention to provide apparatus which may be attached to a user which would determine the oxygenation state of a portion of the user's body and provide that information in a readily understandable form.
It is a further object of certain embodiments of the present invention to provide information pertaining to the oxygenation state of tissue directly to a user wearing the apparatus of the present invention.
It is another object of certain embodiments of the present invention to transmit information pertaining to the oxygenation state of tissue to a remote observer.
According to one aspect of the invention, an oximeter is provided for determining the oxygenation state of localized body tissue per se, constructed to be worn over a period of activity by a user and comprising a flexible, body-conformable support member which supports, adjacent the skin of a user, over the localized tissue of interest, at least a pair of spaced apart light sources, and intermediate thereof, at least a pair of wavelength-specific photo detectors, each light source exposed to transmit wavelengths of both of the specific wavelengths toward the localized tissue of interest lying below the skin and below the associated subcutaneous fat layer of the user, and each detector exposed to receive photons of the respective specific wavelength that have originated from each light source, and scattered from the localized tissue and passed back to the detectors through the subcutaneous fat layer and skin of the user, the support member including conformable barrier means disposed between each light source and the detectors, the barrier means being of substance capable of conforming to the contour of the wearer and preventing light energy proceeding laterally in the region of the barrier means from reaching the detectors.
Somewhat more generally, according to another aspect of the invention, an oximeter is provided for determining the oxygenation state of localized body tissue per se, constructed to be worn over a period of activity by a user and comprising a flexible support member which supports, over the localized tissue of interest, at least a pair of spaced apart light sources, and intermediate thereof, at least a pair of wave length-specific light detectors (e.g., photo detectors), each light source exposed to transmit wavelengths of both of the specific wavelengths toward the localized tissue of interest, and each detector exposed to receive photons of the respective specific wavelength that have originated from each light source, and scattered from the localized tissue and passed back to the detectors.
Preferred embodiments of these aspects of the invention have one or more of the following features.
The light sources comprise broad spectrum CW light sources.
The light sources comprise tungsten filament lamps.
The oximeter includes control means for simultaneously flashing the light sources to enable each detector to pick up light energy at its specific wavelength simultaneously from each light source.
Means are provided to flash the light sources at selected intervals unrelated to the interval of heart beats of the user.
According to another aspect of the invention, an oximeter is provided comprising a flexible support member comprised of a molded-elastomeric backing member, the backing member mounting at least one light source means capable of producing one or more (e.g., two) selected wavelengths and oriented to direct the light to tissue of a user and the backing member also mounting detector means capable of separately detecting energy at each of the wavelengths scattered by tissue of the user, integral elastomeric portions of the backing member defining a barrier exposed for conformable contact with an exposed surface of the user, in position to prevent lateral movement of light in subcutaneous layers from the source means to the detector means.
According to another aspect of the invention, an oximeter is provided comprising a flexible support member, the support member mounting at least one light source means capable of producing two selected wavelengths and oriented to direct the light to tissue of a user and the support member mounting detector means capable of separately detecting energy at each of the wavelengths scattered by tissue of the user, the support member supporting a barrier member exposed for conformable contact with an exposed surface of the user in position to prevent lateral movement of light from the source means to the detector means, the barrier comprising a member having an edge sized and positioned to indent skin and the flesh of the user thereby to intercept light migrating laterally in the subcutaneous fat layer and prevent such light from reaching said detector means.
Preferred embodiments of these aspects of the invention have one or more of the following features.
The barrier member is elastomeric, adapted to conform to the contour of the skin of the wearer.
The flexible support member comprises a molded-elastomeric backing member and the barrier member is integral with the backing member.
The member defining the flesh-indenting edge is about 0.5 cm thick in the region that engages the skin.
The barrier member comprises a rib-form member.
There are in series at least one (e.g., two) barrier members, one closely adjacent to the light source means and one closely adjacent to the detector means.
The support member mounts at least one (e.g., two) spaced-apart light sources and at least one (e.g., a pair) of detectors are disposed parallel to each other, disposed laterally relative to the line between the light sources and equal distance from each of the light sources.
The light sources comprise broad spectrum CW light sources.
Electronic control circuitry for the light source and the detector means are provided in which the circuitry is disposed upon a miniature semiconductor chip carried by the support member.
Electronic control circuitry is provided comprised of entirely non-magnetic components enabling use of the device in conjunction with nuclear magnetic resonance imaging.
The oximeter is combined with a real-time readout device constructed to be worn by the user and having a display responsive to the oximeter disposed for viewing by the user.
The oximeter is associated with means securing it to an appendage of the user and the readout device is constructed to be worn by a user.
The oximeter is combined with radio frequency telemetry means for transmitting oximeter data on a real time basis to a station remote from the user or to a receiver in a readout device constructed to be worn by a user.
The oximeter includes electronic control circuitry for the light source and the detector means, the circuitry disposed upon a miniature semiconductor chip carried by the support member in combination with radio frequency telemetry means controlled by the circuitry for transmitting oximeter data on a real time basis to a station remote from the user.
Means are provided for battery-operation of the oximeter and to record oximetry data in internal digital memory for subsequent display or data analysis on a computer.
The oximeter includes electronic control circuitry for the light source and the detector means, the circuitry disposed upon a miniature semiconductor chip carried by the support member, and means for battery-operation of the oximeter and means to record oximetry data in internal digital memory for subsequent display or data analysis on a computer.
According to still another device aspect of the invention, an oximeter is provided comprising a support mounting a light source and detector means at fixed spacing, and electronic control circuitry for the light source and the detector means, the circuitry disposed upon a miniature semiconductor chip carried by the support member, the oximeter encapsulated in biocompatible, water impermeable material, the oximeter constructed and arranged for implantation under the skin of a user for monitoring internal tissue oxygen trends.
The invention also features a number of methods. The method is provided of monitoring the derivative or rate of change of the time based curve representing detected change of tissue oxygen levels and blood volume and employing these rates as a quantitative standard of measurement of tissue oximetry.
The method is provided of assisting an aviator or other person engaged in activity that can subject the person to high G-forces including providing to the person a comfortable oximeter sensor suitable to be worn about the head (e.g., either integrally in a helmet or helmet lining) and capable of responding to tissue oxygen level and blood volume of brain tissue on a real time basis, employing the oximeter sensor to monitor oxygen level of brain tissue of the wearer as the wearer engages in the activity, comparing the monitored value to a standard and generating a signal, such as a warning or control signal, in the event the monitored level(s) violate(s) a pre-established standard.
Preferably, the oximeter is constructed to monitor the trend of oxygen level in the brain, and means are provided to evaluate the rate of change being detected and using the rate of change as the control value and alarm reference.
The method is provided of monitoring a person suspect of sleep apnea or sudden infant death syndrome including providing to the person a comfortable oximeter sensor capable of automatically responding to oxygen level of the person while permitting the person to sleep, automatically monitoring the output of the oximeter by comparing it to a standard and generating a signal, such as a warning or control signal, in the event the monitored level violates a pre-established standard. Preferably the oximeter sensor is taped comfortably to the head for monitoring. Also, preferably the method is used in conjunction with impedance pneumography (breathing rate measurement using chest-wall impedance) and/or EKG to provide an effective in-home apnea monitor to alarm the patient or other individuals in the area so as to wake the patient and prevent hypoxic tissue damage during sleep.
The method is provided of monitoring the cerebral tissue oxygen rate of change as a means of triggering alarm to awaken a subject in danger of infarct due to hypoxia.
The method is provided of monitoring both tissue oxygen level and blood volume in skin flaps such as are produced either by wound or surgery, as the flaps heal, the separation between the source and the detector being established in relation to the thickness of the skin flap to ensure tissue of the flap per se is being monitored.
The method is provided of emergency monitoring of cerebral tissue oxygen level and blood volume in an emergency care situation with the implantable device, in this case, preferably a stand-alone oximeter carried on a backing member with micro-circuitry to monitor the brain or other tissues in peril of damage due to hypoxia.
The method is provided of employing the device of any of the configurations described above wherein the oxygen levels, blood volume and/or rate of charge are measured in cancerous tissue to indicate the activity and viability of the tissue. Also preferably the method includes monitoring of the viability of a tumor following treatment intended to wipe out the cancerous tissue.
Another aspect of the invention is a helmet into which is molded a tissue oximeter in position to engage the head of the wearer when the helmet is put on, the oximeter being of the NIR type, comprising light source means for transmitting near infrared light into the head, detector means held in spaced position relative to the light source means for receiving light scattered by brain tissue and a barrier disposed to engage the head between the light source means and the detector means to prevent light traveling laterally from the light source means from reaching the detector means. Preferably the oximeter has other features described above. In particular, preferably, the oximeter in the helmet includes control circuitry on a miniature chip and preferably means are provided for determining the rate of change of oximetry readings and for comparing the rate of change to a standard and, e.g. producing an appropriate alarm and/or control signal.
Another feature of the invention is a tissue oximeter comprising a support, a detector fixed to the support and a light source mounted in an adjustable manner to the support to enable selection of the spacing between light source and detector for adjusting the mean depth of tissue to which the oximeter responds.
Still another feature of the invention is a tissue oximeter in combination with means connected to receive tissue oxygen readings from the oximeter, and to determine the rate of change of the readings, the rate of change serving as a quantified indication of the state of the charging metabolic process of the tissue.
Another feature of the invention is an oximeter as described, disposed on an endoscope, catheter or guidewire or the like for insertion via a body passage to internal tissue, and including means such as an inflatable balloon to press the oximeter sensor against the localized tissue of interest. Another feature includes providing a water impermeable coating over the device for use in the presence of water.
Somewhat more generally, according to another aspect of the invention, a cognition spectrophotometer system for transcranial examination of brain activity by measuring changes in electromagnetic radiation scattered and absorbed in a migration path in the brain is provided. The cognition system comprises a light source adapted to introduce electromagnetic radiation of a selected wavelength into the brain at an input port placed at a selected location on the exterior of the head; a detector adapted to detect, at a detection port placed at a selected location on the exterior of the head, radiation of the selected wavelength that has migrated in the brain; stimulation means adapted to cause stimulation of a brain activity while introducing the selected wavelength and while detecting radiation at the detection port; processing means adapted to process signals of the detected radiation that has migrated in the brain to create processed data, and evaluation means adapted to determine a characteristic of the brain activity by correlating the processed data with the caused stimulation of the brain activity.
Preferred embodiments of this aspect of the invention have one or more of the following features. Processing means adapted to process detected radiation that has migrated in the brain in the migration path between the input port and the output port being separated by a predetermined distance and being located at different locations on the exterior of the head.
The input port and the output port are located on the frontal bone, parietal bone, temporal bone or occipital bone, wherein the input port and the output port being separated by a predetermined distance in order to localize the migration of the radiation to a selected region of the brain. The predetermined distance can be 4 centimeters.
The system can also have a second light source adapted to introduce electromagnetic radiation of the selected wavelength into the brain at a second input port placed at a second selected location on the exterior of the head; a second detector adapted to detect, at a second detection port placed at a selected location on the exterior of the head, radiation of the selected wavelength that has migrated along the migration path in the brain from the second input port to the second detection port, and processing means adapted to process signals of the detected radiation that has migrated in the brain from the second input port to the second detection port to create second processed data, wherein the evaluation means determine the characteristic of the brain activity by correlating both first mentioned and the second processed data with the caused stimulation of the brain.
This system is adapted to introduce the radiation simultaneously at the two input ports or sequentially at the first input port and detected at the first detection port, and subsequently introduce the radiation at the second input port and detected at the second detection port.
According to another aspect of the invention a cognition spectrophotometer system for transcranial examination of brain activity by measuring changes in electromagnetic radiation scattered and absorbed in a migration path in the brain is provided. The cognition system comprises a first light source and a second light source adapted to introduce electromagnetic radiation of a selected wavelength into the brain simultaneously at a first input port and at a second input port; the first input port and the second input port being placed at a first selected location and a second selected location on the exterior of the head, respectively; a first detector and a second detector adapted to detect simultaneously, at a first detection port placed at a selected location on the exterior of the head, radiation that has migrated in the brain from the first input port to the first detection port and, at a second detection port placed at second selected location on the exterior of the head, radiation that has migrated in the brain from the second input port to the second detection port; stimulation means adapted to cause stimulation of a brain activity while introducing the radiation at the first and second input ports and while detecting radiation at the first and second detection ports; processing means adapted to process signals of the detected radiation that has migrated in the brain to create processed data; and evaluation means adapted to determine a characteristic of the brain activity by correlating the processed data to the caused stimulation of the brain activity.
Preferred embodiments of this aspect of the invention have one or more of the following features. The system has the first input port and the first output port located on one parietal bone (or temporal bone), separated by a predetermined distance, in order to localize migration of the radiation in a selected region of the respective hemisphere of the brain, and the second input port and the second output port located on the other parietal bone (or temporal bone), separated by a predetermined distance, in order to localize migration of the radiation in a selected region of the other hemisphere of the brain.
The system's processing means are further adapted to compare electromagnetic radiation detected at the first and second detection ports to create processed data representing a differential signal.
The processing of the detected radiation can comprise Fourier transformation.
The stimulation means are adapted to cause visual stimulation, acoustic stimulation, or sensorimotor stimulation.
The evaluation means can be adapted to examine pathophysiological properties of the brain tissue or cognitive function of a selected region of the brain based on correlation between the processed data and the caused stimulation of the brain activity.
The system's first and second light sources are tungsten lamps or light emitting diodes. The first or second detectors are silicon diodes or light-to-frequency convertors each with an interference filter adapted to detect the radiation of the selected wavelength.
The processing means comprise differential counter adapted to register differential signals received from the light-to-frequency convertors, clocking means adapted to route signals of the detected radiation from the light-to-frequency convertors to the differential counter, a frequency-to-voltage converter adapted to convert signals from the differential counter and/or a fast Fourier transformer adapted to process differential signal from the frequency-to-voltage converter.
The evaluation means comprise a storage oscilloscope adapted to analyze the Fourier transformed differential signal of the fast Fourier transformer, and/or computational means adapted to analyze the differential signal.
According to another aspect of the invention a cognition spectrophotometer system for transcranial examination of brain activity by measuring changes in light scattered and absorbed in a migration path in the brain is provided. The system comprises the above-described oximeter, stimulation means adapted to cause stimulation of a brain activity while introducing the light using the light source and while detecting the light that migrated in the localized tissue of interest of the brain, processing means adapted to process signals of the detected light that has migrated in the brain to create processed data, and evaluation means adapted to determine a characteristic of the brain activity by correlating the processed data to the caused stimulation of the brain activity.
According to another aspect, the invented system enables examination of a tissue of an organ by measuring changes in electromagnetic radiation scattered and absorbed in a migration path in the organ. The examination is performed by the steps of (a) introducing electromagnetic radiation of a selected wavelength into the organ simultaneously at a first input port and at a second input port; the first input port being placed at a first selected location, and a second selected location, respectively; (b) detecting simultaneously, at a first detection port placed at a selected location on the exterior of the head, radiation that has migrated in the organ from the first input port to the first detection port and, at a second detection port placed at second selected location on the exterior of the organ, radiation that has migrated in the brain from the second input port to the second detection port; (c) processing signals corresponding to radiation detected at the first and second detection port that have migrated in the brain to create first and second processed data, respectively; and (d) determining a selected property of the organ tissues by correlating the processed first and second data.
The organ can be the brain, breast, limb, etc. If the organ is the brain, then the first input port and the first output port are located on one parietal bone (or temporal bone), separated by a predetermined distance, in order to localize migration of the radiation in a selected region of the respective hemisphere of the brain, and the second input port and second output port are located on the other parietal bone (or temporal bone), separated by a predetermined distance, in order to localize migration of the radiation in a selected region of the other hemisphere of the brain.
A preferred embodiment of the apparatus of the present invention is illustrated in
Power is provided to the detector unit 10 from a replaceable battery pack 30. The replaceable power pack 30 is preferably designed to be of minimal dimensions and weight. Most preferably, the battery pack 30 would be designed to last only for the duration of the activity, e.g., several minutes of sprinting, several hours for a marathon runner, etc. In competitive sports applications, the life of the battery pack is preferably based upon the interval between substitutions or other interruptions between periods of competition.
The embodiment illustrated in
It will be appreciated that the range of the % Hb scale may be adjusted depending upon the range expected to occur during the activity. Since the precision of the present invention is limited by that of the indicator, the range which is displayed is an important variable parameter. In the most accurate embodiment of the present invention, with the endpoints of the % Hb scale set at 20% and 40%, the apparatus would have an accuracy of about 6%, which is about the limit of precision which can be obtained from a moving limb. One of ordinary skill will realize that the gain of the apparatus is preset, depending upon the intensity of the activity expected. In a most preferred embodiment, a button placed on the arm indicator 40 allows the gain to be set.
Referring now to
Thus, superficial light rays from the skin are, in effect, blocked by the opaque barrier 11 from entering the detectors 16,18. This blocking action by the barrier 11 of these superficial rays enables the system to determine the oxygenation state of hemoglobin within the muscle rather than at the skin surface. The rays that migrate deep within the tissue are received by the detectors 16,18. The light rays that migrate superficially “escape” through the skin surface and will be absorbed by the opaque barrier 11. When, for example, a 760 nm impulse is applied, the deoxygenated hemoglobin (Hb) within the muscle is detected and when an 800 nm signal is applied, the oxygenated and deoxygenated hemoglobin (HbO2 and Hb) within the tissue region are detected. The system is able to ignore the oxygenation state at the skin surface and determine that within the tissue.
The lamps 12,14 may be, for example, ˝ W flashlight bulbs that are periodically illuminated in the NR region. The lamps are provided with cutoff filters 13,15 so that only energy of a specified wavelength illuminates the tissue. The silicon diode detectors 16,18 are sensitive to 760±20 nm and 800±20 nm (or 850±20 nm) wavelengths, respectively.
In a preferred embodiment, the lamps 12,14 are light emitting diode (LED) sources, which emit light having a wavelength of about 760±150 nanometers and about 800±150 nanometers (or 850±150 nanometers), respectively. In either embodiment, the lamps are flashed or pulsed at a predetermined repetition rate. The repetition rate of sampling, i.e., the rate at which the lamps are flashed determines the rate at which data may be collected. Thus, for a long distance runner, the lamps are flashed slowly; the output is commensurately changed for a sprinter, the lamps flashed rapidly to produce sufficient data to evaluate an exercise having a duration on the order of seconds. The selection of LEDs as sources of electromagnetic radiation provides a further advantage, since these sources produce a signal-to-noise ratio (S/N) approximately one order of magnitude greater than previously disclosed optical coupling systems using optical light fiber sources.
Referring now to
Another configuration of the present invention is illustrated in
The configuration illustrated by
In any of the embodiments of the present invention, it is preferred that the data be integrated over at least about ten seconds to smooth out irregularities which normally occur in the concentration of deoxyhemoglobin during exercise. However, it will be understood that the period integration can be varied, depending upon the duration of the activity being monitored.
Although manual balancing of the apparatus of the present invention is required, in a preferred embodiment, the balancing is accomplished by depressing a button, which will normalize the output of the two wavelengths. Automatic balancing performed by an intelligent gain control CPU is also envisioned.
Another preferred embodiment of the oximeter is shown in
On the rubber supporting member 101 there are a number of integral raised members 103, 104, 105 and 106. Raised rib 105, which extends about the perimeter, both prevents external light from interfering with the reading and serves to support comfortably the backing member 101 on the subject. Rib 104 extending laterally, adjacent the lamp, and disposed across the line projected between the lamp 100 and the detectors 102, serves as a second light barrier to prevent interfering light transmission between light source 101 and detectors 102. Rib 103 closely surrounds the detectors, and serves as a primary eliminator of environmental light interference, and also serves to absorb light migrating along subcutaneous fat and other subsurface interposed layers, etc. All of these ribs are on the order of ˝ centimeter high and ˝ centimeter thick. Their outside flesh-engaging edges are rounded for comfort to the wearer. The supporting member 101 and its associated ribs are manufactured in one piece of molded rubber. A suitable mold is provided and black silicone rubber is poured into the mold, cured and dried, leaving the subsequent rubber backing 101 with integral ribs and structures. Suitable mounting sites are provided in the backing into which the detectors 102 and the lamp 100 are mounted during final manufacturing. The backing member for the oximeter sensor of
Small L2 spacings of as low as one centimeter are also appropriate for monitoring tissue flaps, though the best configuration of the sensor for flaps is that shown in
In the currently preferred embodiment, the light sources 100 are lamps having tungsten filaments, are broad band light sources which eliminating the problem of matching the light sources to the detector filters.
Each detector is comprised of interference filter 110 which blocks out all light except for that which is desired, each of two detectors having a separate wavelength of interest. At this time 760 nm and 850 nm are preferred, although one can envision that changing, depending upon the application. Beneath the filter is a photosensitive detector which picks up the light and transduces it to an electrical signal which is amplified in the circuit 108 and later transmitted to the control circuitry represented in either
In the presently preferred embodiment, the interference filter is manufactured by Omega, Inc., and the photodiode beneath it is Part No. F1227-66BR, available from Hamamatsu, having a large sensitive area for favorable signal to noise ratio and an NIR wavelength sensitivity. The sensitive area is approximately 6 millimeters squared.
In the present embodiment the filter and detector are epoxied together around and an electronic shield 115 surrounds the diode/filter pair 110 and 111. This surrounding electronic shield eliminates or reduces extraneous electronic interference. It is presently preferred to form this shield of copper in the form of a windowed box which surrounds the detector filter pair.
Once the two separate filter diode pairs are constructed, they are soldered together and then mounted directly to the circuit board 108. Connected also to circuit board 108 is an ultra low noise operational amplifier with high gain, which converts the current signal from the diodes to a voltage applicable to the control circuitry of
Referring now to
The embodiment of
The overall length L1 is determined chiefly as a result of the source 100 to detector 102 spacings L2. The spacing determines the depth of penetration of the light which is scattered and migrated through the tissue. The farther the source is from the detector, the deeper the mean penetration. So for shallow penetrations, one would envision a short L2 and thereby L1. The penetration desired depends upon the muscle of interest. For a large muscle, for example, in the thighs or the calf, which tend to be fairly large, one needs a substantial separation to both (a) penetrate the thicker fat layer and (b) to sense deeper into the larger muscle.
For such muscles, a common dimension for L2 would be 3 to 5 centimeters and L1 would thereby be 7 to 11 centimeters.
The width of the sensor is chiefly dependent upon the size of the detectors 102. In the configuration of the presently preferred embodiment wherein each detector has a photosensitive area of approximately 6 millimeters squared, the width is dependent almost entirely upon those two dimensions. As the photodetectors reduce in dimension width W decreases.
The larger photodetector units provide better signal to noise ratio and thereby enable more accurate representation of the oxygenation state of the tissue. As improvements in technology occur and better photodetectors and initial amplification circuitry are developed, the detector size will decrease, with consequent decrease in W.
The embodiment of
The embodiment pictured in
The smaller sensor sizes improve the flexibility of the device to correspond to perhaps smaller target muscles and smaller regions of interest.
For this adjustability, a slide mechanism is employed in manner to keep L2 equal on both sides, in dependent motion such that as the spacing of one varies, the spacing of the other will also change.
The embodiments of
As previously mentioned, backing member 101 holds in fixed relation the light source 100 and the detectors 102. The length L1 is solely dependent upon a single L2 between the single source and the dual detectors. The spacing depends chiefly upon the muscle location internally of the organ which is being studied. As previously mentioned, from ˝ centimeter or 1 centimeter to 5 centimeters may be appropriate, depending upon the application. Applications envisioned are horse muscle studies.
For application, the physician makes an incision in the skin and slips the oximeter sensor underneath the skin and cutaneous fat layer. There are suture points 113, e.g., biocompatible webbing, surrounding the backing member 101. A coating over the entire sensor is comprised of a biocompatible base material 112, which protects the circuitry from the human system, and protects the human from the invasive nature of the circuitry.
The thickness of the device is of the order of 1 to 2 centimeters maximum. That depth dimension will diminish as technology changes. In
By employing a radio signal to transmit the information from within the body to a receiver outside the body there is no need for wires and the like puncturing the skin.
The sum circuit 124 takes a weighted sum of the 760 nm and 850 nm signals, weighting being chosen appropriate to the fact that the signal variation due to oxygenation or deoxygenation is greater for 760 nm than it is for 850 nm. Because these contrabestic wavelengths tend to cancel the signal due to the difference in oxygenation, the sum shows independent of the difference and is taken as representative of the blood volume changes in the tissue.
The derivative circuit 125 takes the simple derivative to show the rate of change of both of the signals. This is useful, as described above, to trigger alarm circuitry based upon established standards, wherein the higher the rate of the change, and the more sustained that rate of change, the more potentially dangerous the rate of change. This is useful, as mentioned, for example in monitoring aviators for possible black-out conditions and for apnea.
The outputs of these units 123, 124 and 125 are applied to the control circuit which controls where the signals are directed and how they are displayed and/or sent to a computer. The control circuit may be simply embodied as a switch to switch the output to an LCD display, for example. The analog signal from control circuit can be digitized in the display unit 127 and displayed as a digital number. Additionally it can be digitized and sent to a computer or sent in analog form to a computer for digitization.
The oscillator 121 is an independent source for determining the frequency of lamp flashing. Lamps flash at frequency of ˝ Hz or 2 flashes per second or greater. This frequency may be independent of heart rate or any other external factor and is set externally by the user, and may be dependent upon application as mentioned earlier. For example, during exercise, the frequency chosen for the lamp will depend upon the frequency of the exercise, such as the revolutions per minute on a bicycle. If one is expected to encounter a slow change in oxygenation due to the nature of the exercise or the muscle of interest, one can employ a fairly low flashing rate. There is no need for high resolution measure of the rate of change as is required in pulse oximetry.
The lamp rate is tied to the control circuit. The oscillator establishes the timing for the sum and difference circuits because the sum, difference and derivative circuits need to be synchronous. In operation, the lamp flashes, the signal is picked up by the photodetectors and while the lamps are on, the difference, sum and derivative are calculated and are thereby stored in the appropriate memories, and via the control circuit can be directed to the display and to the computer.
The derivative system is the basis of the alarm system. Output from the derivative is compared to a standard within the alarm circuitry, which then determines if there is, for example, a normal rate of change, represented say by a green light, a cautionary rate of change, which may be represented by a yellow light, and a fairly rapid and/or sustained rate of change, which would be for example shown by a red light, an alarm or a buzzer or the like, which would alarm both the wearer or act remotely for example to warn the parents of a neonate in the case of SIDS (Sudden Infant Death Syndrome).
The embodiment shown in
In another preferred embodiment, digital version of the circuitry depicted in
The data after it has been manipulated in 145 will be stored, appropriately transmitted and/or displayed. In addition the alarm is set off if necessary at this point. Then finally an independent timer or delay would be introduced. The processor is delayed for a set period to obtain desired lampflash/data collections frequency.
The sequence is thus: lamp on, collect sample data, lamp off, collect noise data, average sample, calculate sum, difference and derivative, then transmit, display etc., wait if necessary, and then turn on the lamp again and repeat the whole procedure.
Referring now to
Referring now to
Another preferred embodiment of the present invention is a cognition spectrophotometer system, shown diagrammatically in
The display module of
The cognition spectrophotometer system, in one embodiment, measures the low frequency and power spectra of fluctuations of absorbances attributed to the blood concentration changes in the frontal region of the brain. The low frequency recurrences of brain activity are linked to blood concentration increases and are detected in human subjects with an optical device. The spectrophotometer employs wavelengths of light sensitive to oxygenation/deoxygenation of hemoglobin in the red region of the spectrum, i.e., absorbency changes at 760 nm are balanced against those at 850 nm in equal proportions. The difference in the absorbency changes is highly sensitive to the oxygenation/deoxygenation of hemoglobin (HbO2/Hb) and is insensitive to the changes of blood concentration. The sum of the absorbency changes of these two wavelengths is sensitive to the blood concentration changes and insensitive the hemoglobin to oxygenation/deoxygenation of hemoglobin changes (approximately one-half of the 760 nm signal is added to the 850 nm signal). The data reported in
The cognition spectrophotometer of
No analogies were presented during the “rest” intervals. The Fourier transformations of the optical data for two successive 11-minute intervals were recorded and subtracted and were entitled “rest”-“rest” (
The sensor module used in this study consisted of two tungsten flashlight bulbs placed 4 cm each from the two silicon diodes (4 mm×10 mm), each equipped with an interference filter transmitting a 10 nm wide band centered at 760 nm and 850 nm. Thus, this system provided two photon migration paths with input-output separation of 4 cm. A preamplifier coupled the optical signals to an amplifier unit that took the sum and difference of the signals suitably corrected as described above. The tungsten lamps were pulsed at 3 Hz so that absorbance measurements were time shared with background measurements and the one was subtracted from the other to provide background light correction via sample and hold techniques for the difference circuit.
In a response speed test, the output of the filtered sum response reached 70% in 1 sec, as shown in
The ideal study control would repeat every feature of the study except the specific changes due to recognition of the analogies given to the subjects. Thus, the study was repeated with two intervals of “rest” of duration equal to that of the “rest”-“test” study. The “test”-“test” was not considered appropriate because the double duration of the “test” might have led to accommodation in the responses, and because the response to different “tests” could be different. This study had the sensor module placed in one location during the test interval; however, mapping of the “test” response by locating the sensor module in different locations on the exterior of the head is feasible.
Each recurrent signal is indicated by a peak at a particular frequency (Hz) in the illustrations. Peaks present in the “rest” recording are usually related to arterial pulse and related frequencies. Additional frequencies are usually observed in the “test” interval, and the Fournier transforms are readily subtracted by the instrument (“test”-“rest”). Some recurrent frequencies may also contribute to the increasing intensity of the spectra in the low frequency region. Peak size, as well as the 1/f noise is increasing as the frequency decreases.
Both the “test” and “rest” signals contain a signal of the arterial pulse of the brain tissue. At “rest” and “test”, signals at 1-2 Hz and related harmonics are often observed. At “rest”, a low frequency component is detected at various locations on the forehead and tracks closely the frequency of arterial pulse as detected on the wrist. However, these signals nearly completely cancel in the “rest”-“rest” difference Fourier and are thus attributed to the arterial pulse in the brain tissue. Occasionally, the “test”-“rest” shows a difference signal due to altered arterial pulse rate during the “test”.
The difference of the two Fourier transforms designated “test”-“rest” shows a recurrence of signals at particular frequencies associated with presentation of analogies. There is a preponderance of the 0.8, 1.6 and 1.8 Hz peaks and a small contribution of a 2.8 Hz peak. The largest peak corresponds to 1% of the total signal. Of interest from the theoretical standpoint is a large component of 1/f noise in the “test”-“rest” diagram suggesting that recurrence at the very low frequencies is less probable than at the higher frequencies. In a repetition of this study (#25), a 2.3 Hz peak was observed (see Table I) and the doublet peaks at 1.7 and 1.9 Hz were again observed in “test”-“rest”.
Another frequency spectrum of a female subject (B) is shown in
The intensity value at the particular frequency gives the power spectrum of
A more detailed plot of the data of Table I, including those that exhibited three or more frequencies, indicated that this ensemble exhibited equal maxima at the harmonic frequencies 0.8 and 1.6 Hz and approximately equal peaks at 1.2, 2.6 and 4.2 Hz respectively, a rough approximation to harmonics of frequencies of 0.08 and 1.2 Hz. However, there was no peak at 3.0, 2.1 Hz at the exact harmonic frequencies.
The cognition spectrophotometer system, used in this trial, utilizes only the sum of the 760 nm and 850 nm signals. The isosbestic point in the Hb/HbO2 spectrum is approximately at 800 nm, and thus the balanced sum of Hb/HbO2 absorbances at 760 and 850 nm measures the blood concentration. Hb/HbO2 is the principal absorber at these wavelengths since the signal is over 20 times that of cytochrome aa3. The fact that no significant results were obtained in the difference recording suggests that the oxygenation/deoxygenation of the frontal lobe tissue was not a predominant effect in these studies. Changes of light scattering are not separated from absorbance changes when using continuous light, and would be expected to uniformly affect both 760 and 850 nm.
Furthermore, results of the present trial are compatible with other studies using PET, SPEC, and MRI which also suggest existence of blood flow changes during brain stimulation and the fact that the arterial pulse is the strongest signal in both “rest” and “test”; this supports the interpretation attributing the measured signal to blood concentration changes.
It is expected that the metabolic activities induced by brain stimulation contain low frequency component signals. The cognition spectrophotometer system of
Our narrow band width and relatively short iteration time (<11 min.) in this trial was set by the characteristics of an available instrument, and the detected spectrum may be only a portion of the total frequency spectrum. As shown in
In the above described trial only a crude localization of the response was employed by placement of the input and output ports. The optical system was designed to respond optimally to blood concentration changes (in a volume of about 3-5 ml) in the frontal/temporal cortex, and the analogies were designed to stimulate activity in the frontal region. When left and right sides of the forehead were compared, the success rate of new peaks in the Fourier transform was two times greater in the left side.
An important aspect of future development of the optical methods is the rate at which data may be accumulated. The travel time of photon migration over a path length of one meter is 23 ns with a 4 cm input/output separation. The signal to noise ratio will determine the number of iterations of the test, which in these preliminary studies, was approximately 50 over a period of 11 minutes.
The photon migration kinetics are responsive to both light scattering and light absorption. Whilst absorption has been stressed in these studies, light scattering is much closer to the primary events of neuronal/axonal response than to the blood flow/blood concentration change, both in anatomy and in time.
In this trial, the low frequency recurrence of changes of blood concentration was measured in portions of the brain that are approximately 2 cm deep from the surface of the skull of the subjects. Application to other stimuli (for example, visual, acoustic, sensorimotor) that affect function in other regions of the brain may be possible. (Visual stimulation registered in the visual cortex was not used in the present trial because dense hair covered the surface of the back of the head in the population studied.) It is expected that the recurrence frequencies which are observed in the cognitive tests would be significantly diminished in cases of neuronal deterioration. Thus, the cognition spectrophotometer system enables simple non-invasive and rapid testing of cognitive function of different regions of the brain.
The cognition spectrophotometer system is designed to provide objective evaluation of functional activity of the brain with a simple and inexpensive device. The system enables a wide range of studies of the brain activity in responding to appropriate tasks and presents an alternative to several expensive techniques (for example, MEG and EEG) or ones that involve radioactive techniques. Thus, screening for neuronal deterioration and/or deterioration of brain function can be done conveniently and continuously.
In another embodiment, shown in
The cognition spectrophotometer, shown in
For high frequency measurements, the cognition spectrophotometer can use a fast lateralization detector, shown in
The fast lateralization detector measures a frequency difference between the two silicon detector converters 204. The signal of each detector is routed to a differential counter 212 using a 50 Hz clock 210. If the differential count is zero, both detectors are outputting the same frequency signal. If there is a difference in the signals detected at the two detectors, the differential count is not zero. The differential signal is processed by a frequency-to-voltage converter 214. Converter 214 operates in a low frequency range and detects frequency differences. The voltage output is Fourier transformed, stored and analyzed in view of a visual stimulus 218 or other brain activity stimulus.
The differential spectrophotometer introduces electromagnetic radiation of at least one selected wavelength (for example, 800 nm) into the brain simultaneously at a first and second input port of the 271 and 272 sensor modules. Both the first input port and the second input port are placed at a first selected location and a second selected location on the exterior of the head, respectively. Two detectors, placed at a first and second location on the exterior of the head, are simultaneously detecting radiation that migrated along the banana-shaped paths in the two brain hemispheres from the first and second input ports to the first and second output ports, respectively. Control module 274 collects the detector signals, corrects for the noise signals and sends the corrected signals to analyzer/display module 276 and to computer/printer module 278. Control module 274 can also create a differential signal, as described in
The system processes the signals of the two detectors and evaluates the processed data to determine whether the radiation migrated in a tissue of abnormal physiological or pathophysiological properties.
In another application, the differential spectrophotometer system can be used to determine physiological or pathophysiological properties of a breast tissue. Here, one sensor is placed on one breast and the other sensor on the other breast. Similarly as for the brain, breast tissue is examined by comparing the two signals of the radiation that migrated in the two paths in the respective breast.
The lateralized detection technique that simultaneously measures photon migration in two migration paths (
One of ordinary skill in the art will appreciate that the present invention is not limited to the particular embodiments described in detail. Modifications to the circuitry disclosed, and other aspects of the spectrophotometer configurations disclosed, as well as other modifications to the physical arrangement of the present apparatus will be obvious to those of ordinary skill. Further, the present invention is not limited to any of the uses described herein. In order to fully appreciate the scope of the present invention, reference should be made to the following claims.