Multi-channel non-invasive tissue oximeter

Abstract

A method and apparatus for spectrophotometric in vivo monitoring of blood metabolites such as hemoglobin oxygen concentration at a plurality of different areas or regions on the same organ or test site on an ongoing basis, by applying a plurality of spectrophotometric sensors to a test subject at each of a corresponding plurality of testing sites and coupling each such sensor to a control and processing station, operating each of said sensors to spectrophotometrically irradiate a particular region within the test subject; detecting and receiving the light energy resulting from said spectrophotometric irradiation for each such region and conveying corresponding signals to said control and processing station, analyzing said conveyed signals to determine preselected blood metabolite data, and visually displaying the data so determined for each of a plurality of said areas or regions in a comparative manner.

The invention claimed is: 
     
       1. A method for comparative spectrophotometric in vivo monitoring and display of selected blood metabolites present in a plurality of different internal regions of the same test subject on a continuing and substantially concurrent basis, comprising the steps of:
 applying separate spectrophotometric sensors to a test subject at each of a plurality of separate testing sites and coupling each of said sensors to a control and processing station;   operating a selected number of said sensors on a substantially concurrent basis to spectrophotometrically irradiate at least two separate internal regions of the test subject during a common time interval, each of said regions being associated with a different of said testing sites;   separately detecting and receiving light energy resulting from said spectrophotometric irradiation for each of said at least two separate internal regions, and conveying separate sets of signals to said control and processing station which correspond to the separately detected light energy from said at least two separate internal regions;   separately and concurrently analyzing said conveyed separate sets of signals to separately determine quantified data representative of a blood metabolite in each of said at least two separate internal regions; and   concurrently visually displaying said separately determined quantified data for each of said at least two separate internal regions for direct concurrent mutual comparison, wherein said sensors are applied to a head of the test subject and are used to monitor two mutually separate regions within a brain of the test subject.   
     
     
       2. The method of  claim 1 , wherein said step of analyzing comprises quantitative determination of blood oxygenation levels within each of said at least two separate internal regions. 
     
     
       3. The method of  claim 2 , wherein said analyzing step includes producing separate quantitative value determinations for hemoglobin oxygen saturation for each of said at least two separate internal regions. 
     
     
       4. The method of  claim 3 , wherein said analyzing step includes production of ongoing graphical traces representing a plurality of said quantitative value determinations made at successive points in time. 
     
     
       5. The method of  claim 4  including the step of visually displaying a plurality of said graphical traces at substantially the same time and in predetermined relationship to one another to facilitate rapid and accurate visual comparison. 
     
     
       6. The method of  claim 5 , including the step of visually displaying a plurality of said quantitative value determinations at substantially the same time and in predetermined relationship to one another to facilitate rapid and accurate visual comparison. 
     
     
       7. The method of  claim 3 , including the step of visually displaying a plurality of said quantitative value determinations at substantially the same time and in predetermined relationship to one another to facilitate rapid and accurate visual comparison. 
     
     
       8. The method of  claim 1 , wherein said metabolite comprises hemoglobin oxygen. 
     
     
       9. The method of  claim 1 , wherein said sensors are positioned in locations proximate to different brain hemispheres and said two mutually separate regions are located in a different brain hemisphere. 
     
     
       10. The method of  claim 9 , wherein said metabolite comprises cerebral blood hemoglobin oxygenation. 
     
     
       11. An apparatus for concurrent comparative spectrophotometric in vivo monitoring of selected blood metabolites present in each of a plurality of different internal regions on a continuing basis, comprising:
 a plurality of spectrophotometric sensors, each attachable to a test subject at different test locations and adapted to separately but concurrently spectrophotometrically irradiate at least two different internal regions within the test subject associated with each of said test locations;   a controller and circuitry coupling each of said sensors to said controller for separately and individually but concurrently operating certain of said sensors to spectrophotometrically irradiate each of said different internal regions within the test subject associated with each of said test locations;   said sensors each further adapted to receive light energy resulting from the separate spectrophotometric irradiation of said sensors' associated one of said at least two different internal regions on a substantially concurrent basis with other said sensors, and to produce separate signals corresponding to the light energy received, said circuitry acting to convey said separate signals to said controller for separate analytic processing;   said controller adapted to analytically process said conveyed signals separately and determine separate quantified blood metabolite data therefrom for each of said sensors and said sensors' associated one of said at least two different internal regions; and   a visual display coupled to said controller and adapted to separately but concurrently display the quantified blood metabolite data determined for each of said sensors in a mutually-comparative manner, wherein said sensors are adapted to be applied to a head of the test subject and to monitor a brain of the test subject.   
     
     
       12. The apparatus of  claim 11 , wherein said controller is adapted to analyze said data to quantitatively determine blood oxygenation within said at least two different internal regions. 
     
     
       13. The apparatus of  claim 12 , wherein said controller is adapted to produce separate numeric value designations for hemoglobin oxygen saturation for said at least two different internal regions. 
     
     
       14. The apparatus of  claim 13 , wherein said controller and said display are adapted to produce ongoing graphical traces representing a plurality of said numeric value designations for the same region taken over a period of time. 
     
     
       15. The apparatus of  claim 14 , wherein said controller and said display are adapted to visually display at least two of said graphical traces on a substantially concurrent basis and in predetermined relationship to one another to facilitate rapid and accurate visual comparison. 
     
     
       16. The apparatus of  claim 15 , wherein said controller and said display are adapted to visually display at least two of said numeric value designations as well as at least two of said graphical traces on a substantially concurrent basis and in proximity to one another to facilitate rapid and accurate visual comparison. 
     
     
       17. The apparatus of  claim 13 , wherein said controller and said display are adapted to visually display at least two of said numeric value designations on a substantially concurrent basis and in predetermined relationship to one another to facilitate rapid and accurate visual comparison. 
     
     
       18. The apparatus of  claim 11 , wherein said sensors are adapted to provide signals to said controller which comprise at least two separate data sets that cooperatively define at least portions of a particular area within a given one of said at least two different internal regions. 
     
     
       19. The apparatus of  claim 18 , wherein said data sets provided by said sensors include a first set characterizing a first part of said particular area and a second set characterizing a second part of said particular area. 
     
     
       20. The apparatus of  claim 19 , wherein said second part of said particular area characterized by said second set includes at least part of said first part of said area. 
     
     
       21. The apparatus of  claim 11 , wherein said controller is adapted to determine blood oxygenation saturation in said brain. 
     
     
       22. The apparatus of  claim 11 , wherein at least two of said sensors are adapted to be positioned in locations associated with mutually different hemispheres of the brain and each of said sensors is operable to separately monitor at least portions of each of said different hemispheres. 
     
     
       23. The apparatus of  claim 22 , wherein said controller is adapted to determine cerebral blood oxygenation saturation within each of said different hemispheres. 
     
     
       24. The apparatus of  claim 22 , wherein said sensors are adapted to provide signals to said controller which comprise at least two data sets that cooperatively define at least portions of a particular area within the same hemisphere of said brain. 
     
     
       25. The apparatus of  claim 11 , wherein said sensors are adapted to be applied to the outside periphery of the test subject and to operate non-invasively. 
     
     
       26. A method for concurrent comparative in vivo monitoring of blood metabolites in each of a plurality of different internal regions in a selected test subject, comprising the steps of:
 spectrophotometrically irradiating each of a plurality of different testing sites on said test subject;   detecting light energy resulting from said spectrophotometric irradiation of said testing sites, and providing separate sets of signals to a control and processing station which are representative of the light energy received by each of said testing sites and which cooperatively define blood metabolite data for an individual one of at least two different internal regions;   analyzing said separate signals to determine quantified blood metabolite data representative of at least one defined region within said at least one test subject associated with each of at least two different of said testing sites, each said defined region being different from the other; and   concurrently displaying data sets for each of said at least two different internal regions at substantially the same time for direct mutual comparison, wherein said at least two different internal regions are located within different brain hemispheres of said test subject.   
     
     
       27. The method of  claim 26 , wherein said data sets include a first set which characterizes a first zone within one of said at least two different internal regions and a second set which characterizes a second zone that is at least partially within the same one of said at least two different internal regions. 
     
     
       28. The method of  claim 26 , wherein said spectrophotometric irradiation comprises application of at least two different wavelengths applied in an alternating sequence of timed pulses, and wherein detection of light energy corresponding to each of said at least two different wavelengths is done on a timed periodic basis using detection periods whose occurrence generally corresponds to that of said applied spectrophotometric irradiation. 
     
     
       29. The method of  claim 28 , wherein the duration of each of said detection periods is limited to a length which is less than that of each pulse of applied spectrophotometric irradiation. 
     
     
       30. The method of  claim 29 , wherein the duration of each of said detection periods is less than half that of a pulse of said applied spectrophotometric irradiation. 
     
     
       31. The method of  claim 30 , wherein a plurality of said detection periods are used during pulses of said applied spectrophotometric irradiation, and a corresponding energy detection occurs during each of a plurality of said detection periods. 
     
     
       32. The method of  claim 31 , further including the steps of averaging a selected number of energy detection event values to obtain a resultant value therefor, and using said resultant value to compute a metabolite value which is representative thereof. 
     
     
       33. The method of  claim 32 , wherein said display includes said computed representative metabolite value. 
     
     
       34. The method of  claim 33 , wherein said display is refreshed periodically by using a sequence of computed representative metabolite values which are based upon and represent the averaged detection event values produced during the different time intervals corresponding to the intervals of said periodic display refreshment. 
     
     
       35. Apparatus for spectrophotometric in vivo monitoring of a selected metabolic condition in each of a plurality of different test subject regions on a substantially concurrent basis, comprising:
 a plurality of spectrophotometric emitters, each adapted to separately spectrophotometrically irradiate a designated region within a test subject from a test location on said test subject;   a controller and circuitry coupling each of said emitters to said controller for individually operating selected ones of said emitters to spectrophotometrically irradiate at least two particular regions within the test subject;   a plurality of detectors, each adapted to separately receive light energy resulting from the spectrophotometric irradiation of said at least two particular regions, and to produce at least one separate set of signals for each one of said at least two particular regions; and circuitry acting to convey said at least one separate set of signals to said controller for analytic processing;   said controller adapted to analytically process said at least one separate set of signals to determine separate sets of quantified data representative of a metabolic condition in said at least two particular regions; and   a visual display coupled to said controller and adapted to display separate representations of said separate sets of quantified data for each of said at least two particular regions in a mutually-comparative manner and on a substantially concurrent basis, wherein at least two of said at least two particular regions are located in mutually separate regions of a brain of said test subject.   
     
     
       36. The apparatus of  claim 35 , wherein said controller includes a computer programmed to analyze said signals to separately determine a blood oxygenation state within each of said at least two particular regions. 
     
     
       37. The apparatus of  claim 36 , wherein said computer comprises a processor, data buffers, and a timing signal generator, said data buffers adapted to store data representative of said blood oxygenation state and said timing signal generator adapted to control actuation of said emitters and detectors. 
     
     
       38. The apparatus of  claim 36 , wherein said controller comprises a unitary device which includes said computer and said display. 
     
     
       39. The apparatus of  claim 38 , wherein said unitary device further includes a keyboard interface to said computer. 
     
     
       40. The apparatus of  claim 38 , wherein said unitary device further includes a data output interface. 
     
     
       41. The apparatus of  claim 40 , wherein said unitary device further includes an integral keyboard interface to said computer. 
     
     
       42. The apparatus of  claim 38 , wherein said display comprises a flat electroluminescent visual display screen. 
     
     
       43. The apparatus of  claim 42 , wherein said unitary device further includes an integral keyboard interface to said computer. 
     
     
       44. The apparatus of  claim 35 , wherein at least certain of said detectors and certain of said emitters comprise operational pairs, and said controller is arranged to operate the emitters and detectors of at least certain of said operational pairs in predetermined timed relationship while maintaining the emitters and detectors of other of said operational pairs in a non-operating condition. 
     
     
       45. The apparatus of  claim 44 , wherein said controller is adapted to sequence the operation of said at least certain of said operational pairs. 
     
     
       46. The apparatus of  claim 45 , wherein at least one of said operational pairs include a plurality of said detectors arranged at mutually spaced locations which are spaced at differing distances from the emitter of said at least one of said operational pairs. 
     
     
       47. The apparatus of  claim 46 , wherein said controller is adapted to operate the emitter and a selected number less than all of the detectors of at least one of said operational pairs substantially in unison while holding the other detectors of said at least one of said operational pairs in a non-operating condition, and said controller is further arranged to operate said other detectors substantially in unison with said emitter at another time during which said selected number of said detectors are maintained in a non-operating condition. 
     
     
       48. The apparatus of  claim 44 , wherein at least one of said operational pairs includes a first detector and a second detector, and wherein the first detector is located nearer the emitter than the second detector to thereby provide near and far detector groupings for said at least one of said operational pairs. 
     
     
       49. The apparatus of  claim 48 , wherein said controller is adapted to sequence the operation of said at least one of said operational pairs. 
     
     
       50. A system for evaluating oxygen saturation levels in a region of human tissue, the system comprising:
 a first emitter, a second emitter, a first detector, and a second detector, the first emitter being adapted to emit at least a first light into the tissue region, the second emitter being adapted to emit at least a second light into the tissue region;   the first detector being located a first distance from the first emitter and a second distance from the second emitter greater than the first distance, the first detector being further configured to detect at least two different wavelengths of the first light and at least two different wavelengths of the second light;   the second detector being located a third distance from the first emitter and a fourth distance from the second emitter less than the third distance, the second detector being further configured to detect at least two different wavelengths of the first light and at least two different wavelengths of the second light;   the first detector and the second detector being configured to produce a set of signals indicative of the first light and the second light detected by the first detector and the second detector; and   an oximeter unit configured to reduce cross-talk between the first emitter and the second emitter by driving the first emitter and the second emitter in sequence on a substantially simultaneous basis, the oximeter unit further configured to receive the set of signals and to determine at least a regional blood oxygen saturation value for the tissue region based at least in part on the set of signals.   
     
     
       51. The system of claim 50, wherein the first emitter, the second emitter, the first detector, and the second detector are aligned within a plane. 
     
     
       52. The system of claim 50, wherein a line defined between a center of the first detector and a center of the second emitter partially overlaps with a line defined between a center of the second detector and a center of the first emitter. 
     
     
       53. The system of claim 50, wherein the third distance is longer than the first distance and is longer than the fourth distance. 
     
     
       54. The system of claim 50, wherein the second distance is approximately equal to the third distance. 
     
     
       55. The system of claim 54, wherein the first distance is approximately equal to the fourth distance. 
     
     
       56. The system of claim 50, wherein the first and second emitters alternately emit the first light and the second light along a paring of mean paths. 
     
     
       57. The system of claim 50, wherein the oximeter unit is capable of removing one or more effects attributable to portions of the tissue region through which the first light propagates before being detected by the first detector and through which the second light propagates before being detected by the second detector. 
     
     
       58. The system of claim 50, wherein the first light and the second light each include at least four different wavelengths and wherein the first detector and the second detector are adapted to detect each of the four different wavelengths. 
     
     
       59. The system of claim 50, wherein the first emitter comprises:
 a first narrow-bandwidth light-emitting diode (LED) configured to output a first center output wavelength of the first light;   a second narrow-bandwidth LED configured to output a second center output wavelength of the first light, the second center output wavelength being different than the first center output wavelength;   a third narrow-bandwidth LED configured to output a third center output wavelength of the first light, the third center output wavelength being different than the first center output wavelength and the second center output wavelength; and   a fourth narrow-bandwidth LED configured to output a fourth center output wavelength of the first light, the fourth center output wavelength being different than the first, second, and third center output wavelengths, wherein the first detector and the second detector are adapted to detect each of the four center output wavelengths of the first light.   
     
     
       60. The system of claim 50, wherein the tissue region is a first tissue region, the set of signals is a first set of signals, and the regional blood oxygen saturation value is a first regional blood oxygen saturation value, the system further comprising a third emitter, a fourth emitter, a third detector, and a fourth detector, the third emitter being adapted to emit at least a third light into a second tissue region, the fourth emitter being adapted to emit at least a fourth light into the second tissue region;
 the third detector being located a fifth distance from the third emitter and a sixth distance from the fourth emitter, the third detector being further configured to detect at least two different wavelengths of the third light and at least two different wavelengths of the fourth light;   the fourth detector being located a seventh distance from the third emitter and an eighth distance from the fourth emitter, the fourth detector being configured to detect at least two different wavelengths of the third light and at least two different wavelengths of the fourth light;   the third emitter being closer to the third detector than the fourth detector and the fourth emitter being closer to the fourth detector than the third detector;   the third detector and the fourth detector being configured to produce a second set of signals indicative of the third light and fourth light detected by the third detector and the fourth detector; and   the oximeter unit being configured to reduce cross-talk between the third emitter and the fourth emitter by driving the third emitter and the fourth emitter in sequence on a substantially simultaneous basis, the oximeter unit further configured to receive the second set of signals and to determine at least a second regional blood oxygen saturation value for the second tissue region based at least in part on the second set of signals.   
     
     
       61. The system of claim 60, wherein the oximeter unit includes a display configured to convey one or more superimposed trace lines indicative of at least the first regional blood oxygen saturation value and the second regional blood oxygen saturation value. 
     
     
       62. The system of claim 60, wherein the first and second emitters are adapted to emit the first and second light, respectively, into a first brain hemisphere, the third and fourth emitters are adapted to emit the third and fourth light, respectively, into a second brain hemisphere, and the oximeter unit is capable of determining a regional blood oxygen saturation value of the first brain hemisphere and determining a regional blood oxygen saturation value of the second brain hemisphere. 
     
     
       63. The system of claim 50, wherein the first emitter and the first detector form a first near coupling, the second detector is separated from the first emitter by a distance that is greater than a distance between the first emitter and the first detector to form a first far coupling, the second emitter and the first detector form a second far coupling, and the second detector is separated from the second emitter by a distance that is less than a distance between the first emitter and the second detector to form a second near coupling. 
     
     
       64. The system of claim 50, wherein a distance between the first detector and the second detector is approximately equal to the first distance and to the fourth distance. 
     
     
       65. The system of claim 50, wherein the first detector is adapted to produce signals indicative of background light during a time that the first and second emitters are not emitting, and the oximeter unit is further configured to determine the regional blood oxygen saturation value using the signals indicative of the background light. 
     
     
       66. The system of claim 50, wherein the first emitter and the second emitter are secured within different sensor bodies. 
     
     
       67. A method for evaluating oxygen saturation levels in a region of human tissue, the method comprising:
 detecting, with a first detector, at least two different wavelengths of a first light propagated from a first emitter into the human tissue region and at least two different wavelengths of a second light propagated from a second emitter into the human tissue region, the first emitter and the second emitter emitting light sequentially and alternatingly with one another on a substantially simultaneous basis;   detecting, with a second detector, at least two different wavelengths of the first light propagated from the first emitter into the human tissue region and at least two different wavelengths of the second light propagated from the second emitter into the human tissue region;   the first emitter being closer to the first detector than the second detector and the second emitter being closer to the second detector than the first detector;   generating, with the first and second detectors, a set of signals indicative of the first light and the second light detected by the first detector and the second detector;   receiving, with an oximeter unit, the set of signals; and   determining, with the oximeter unit, at least a regional blood oxygen saturation value for the human tissue region based at least in part on the set of signals.   
     
     
       68. The method of claim 67, wherein the human tissue region is a first human tissue region, the set of signals is a first set of signals, and the regional blood oxygen saturation value is a first regional blood oxygen saturation value, the method further comprising steps of:
 detecting, with a third detector, at least two different wavelengths of a third light propagated from a third emitter into a second human tissue region and at least two different wavelengths of a fourth light propagated from a fourth emitter into the second human tissue region;   detecting, with a fourth detector, at least two different wavelengths of the third light propagated from the third emitter into the second human tissue region and at least two different wavelengths of the fourth light propagated from the fourth emitter into the second human tissue region, the third emitter and the fourth emitter emitting light sequentially and alternatingly with one another on a substantially simultaneous basis;   the third emitter being closer to the third detector than the fourth detector and the fourth emitter being closer to the fourth detector than the third detector;   generating, with the third and fourth detectors, a second set of signals associated with the third light and the fourth light detected by the third detector and the fourth detector;   receiving, with an oximeter unit, the second set of signals; and   determining, with the oximeter unit, at least a second regional blood oxygen saturation value for the second human tissue region based at least in part on the second set of signals.   
     
     
       69. The method of claim 68, further comprising a step of displaying a first indicator of the first regional blood oxygen saturation value on a monitor of the oximeter unit and a step of displaying a second indicator of the second regional blood oxygen saturation value on the monitor. 
     
     
       70. The method of claim 68, wherein the step of determining, at the oximeter unit, at least the first regional blood oxygen saturation value includes removing one or more effects attributable to a portion of the human tissue in which the first light propagates before being detected by the first detector. 
     
     
       71. The method of claim 70, wherein the step of determining, at the oximeter unit, at least the second regional blood oxygen saturation value includes removing one or more effects attributable to a portion of the human tissue through which the third light propagates before being detected by the third detector and through which the fourth light propagates before being detected by the fourth detector. 
     
     
       72. The method of claim 67, wherein the first light detected at the first detector includes a first center output wavelength, a second center output wavelength, a third center output wavelength, and a fourth center output wavelength, each of the four center output wavelengths being different from the other three center output wavelengths and each center output wavelength being generated by a separate narrow-bandwidth light-emitting diode.