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 transmitter, a first detector, a second detector, and a third detector, the transmitter being adapted to transmit light having at least two different wavelengths into the region of human tissue;   the first detector forming a near detector grouping with the transmitter, the first detector being adapted to detect the at least two different wavelengths of the light transmitted by the transmitter;   the second detector and the third detector each being adapted to detect the at least two different wavelengths of the light transmitted by the transmitter, the second detector and the third detector each being located farther from the transmitter than the first detector to form far detector groupings;   the first detector, the second detector, and the third detector being configured to produce a set of signals indicative of the light detected by the first detector, the second detector, and the third detector; and   an oximeter unit configured to receive the set of signals and to determine at least a regional blood oxygen saturation value for the region of human tissue based at least in part on the set of signals.   
     
     
       51. The system of claim 50, wherein a line passing through a midpoint of the transmitter and a midpoint of the first detector is spaced apart from a midpoint of the second detector and a midpoint of the third detector. 
     
     
       52. The system of claim 50, wherein a line defined between a center of the transmitter and a center of the first detector forms an acute angle with a line defined between the center of the transmitter and a center of the second detector. 
     
     
       53. The system of claim 52, wherein the acute angle is a first acute angle, the line defined between the center of the transmitter and the center of the first detector forms a second acute angle with a line defined between the center of the transmitter and a center of the third detector, and the second acute angle is substantially similar to the first acute angle. 
     
     
       54. The system of claim 50, wherein the light transmitted by the transmitter has at least four different wavelengths and the first, second, and third detectors are adapted to detect each of the wavelengths. 
     
     
       55. The system of claim 50, wherein the light is a first light, the transmitter is a first transmitter, the set of signals is a first set of signals, the region of tissue is a first region of tissue, and the regional blood oxygen saturation value is a first regional blood oxygen saturation value, the system further comprising:
 a second transmitter, a fourth detector, a fifth detector, and a sixth detector, the second transmitter being adapted to transmit a second light having at least two different wavelengths into a second region of human tissue;   the fourth detector forming a near detector grouping with the second transmitter, the fourth detector being adapted to detect the at least two different wavelengths of the second light transmitted by the second transmitter;   the fifth detector and the sixth detector each being adapted to detect the at least two different wavelengths of the second light transmitted by the second transmitter, the fifth detector and the sixth detector each being located farther from the second transmitter than the fourth detector to form far detector groupings;   the fourth detector, the fifth detector, and the sixth detector being configured to produce a second set of signals indicative of the second light detected by the fourth detector, the fifth detector, and the sixth detector; and   the oximeter unit being configured to receive the second set of signals and to determine at least a second regional blood oxygen saturation value for the second region of tissue based at least in part on the second set of signals.   
     
     
       56. The system of claim 55, 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 over a time period. 
     
     
       57. The system of claim 50, wherein the oximeter unit is adapted to interconnect to a remote device for downloading data using a data output interface. 
     
     
       58. The system of claim 50, wherein the oximeter unit includes a processor configured to transmit timing signals to cause the transmitter to transmit the light. 
     
     
       59. The system of claim 58, further comprising a pre-amp configured to condition the set of signals before transmitting the conditioned set of signals to the oximeter, the pre-amp being configured to condition the set of signals using timing signals from the processor of the oximeter unit. 
     
     
       60. A method for evaluating oxygen saturation levels in a tissue region of a human, the method comprising:
 detecting, with a first detector, at least two different wavelengths of a light propagated from a transmitter through the tissue region, the transmitter being located a first distance from the first detector;   detecting, with a second detector, at least two different wavelengths of the light propagated from the transmitter through the tissue region, the second detector being located a distance from the transmitter greater than the first distance;   detecting, with a third detector, at least two different wavelengths of the light propagated from the transmitter through the tissue region, the third detector being located a distance from the transmitter greater than the first distance;   generating, with the first detector, the second detector, and the third detector, a set of signals associated with the light detected by the first detector, the second detector, and the third 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 tissue region based at least in part on the set of signals.   
     
     
       61. The method of claim 60, wherein the light is a first light, the tissue region is a first tissue region, the transmitter is a first transmitter, and the regional blood oxygen saturation value is a first regional blood oxygen saturation value, the method further comprising:
 detecting, with a fourth detector, at least two different wavelengths of a second light propagated from a second transmitter through a second tissue region, the fourth transmitter being located a second distance from the second transmitter;   detecting, with a fifth detector, at least two different wavelengths of the second light propagated from the second transmitter through the second tissue region, the fifth detector being located a distance from the second transmitter greater than the second distance;   detecting, with a sixth detector, at least two different wavelengths of the second light propagated from the second transmitter through the second tissue region, the sixth detector being located a distance from the second transmitter greater than the second distance;   generating, with the fourth detector, the fifth detector, and the sixth detector, a second set of signals associated with the second light detected by the fourth detector, the fifth detector, and the sixth 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 tissue region based at least in part on the second set of signals.   
     
     
       62. The method of claim 61, wherein the first distance is approximately equal to the second distance. 
     
     
       63. The method of claim 61, further comprising a step of substantially simultaneously displaying a first indicator of the first regional blood oxygen saturation value on a monitor of the oximeter unit and a second indicator of the second regional blood oxygen saturation value on the monitor of the oximeter unit. 
     
     
       64. The method of claim 61, wherein the step of determining, with 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 second light propagates before being detected by the fourth detector. 
     
     
       65. The method of claim 60, wherein the light detected at the first detector includes at least four different wavelengths and the first, second, and third detectors are adapted to detect each wavelength of the light. 
     
     
       66. A regional oximeter system comprising:
 a first transmitter, a first detector, a second detector, and a third detector;
 the first transmitter being adapted to transmit at least a first light having at least four different wavelengths into a first tissue region; 
 the first detector forming a near detector grouping with the first transmitter, the first detector being configured to detect the at least four different wavelengths of the first light; 
 the second detector and the third detector each being configured to detect the at least four different wavelengths of the first light, the second detector and the third detector each being located farther from the first transmitter than the first detector to form far detector groupings with the first transmitter; and 
 the first detector, the second detector, and the third detector being configured to produce a first set of signals indicative of the first light detected by the first detector, the second detector, and the third detector; 
   a second transmitter, a fourth detector, a fifth detector, and a sixth detector;
 the second transmitter being adapted to transmit at least a second light having at least four different wavelengths into a second tissue region; 
 the fourth detector forming a near detector grouping with the second transmitter, the fourth detector being configured to detect the at least four different wavelengths of the second light; 
 the fifth detector and the sixth detector each being configured to detect the at least four different wavelengths of the second light, the fifth detector and the sixth detector each being located farther from the second transmitter than the fourth detector to form far detector groupings with the second transmitter; and 
   the fourth detector, the fifth detector, and the sixth detector being configured to produce a second set of signals indicative of the second light detected by the fourth detector, the fifth detector, and the sixth detector;   a first pre-amp unit configured to condition the first set of signals produced by the first sensor;   a second pre-amp unit configured to condition the second set of signals produced by the second sensor;   a processor configured to receive the conditioned first set of signals from the first pre-amp and the conditioned second set of signals from the second pre-amp and to process those signals to determine regional oxygen saturation values for the first tissue region and for the second tissue region; and   a display configured to receive the regional oxygen saturation values for the first and second tissue regions from the processor and to simultaneously display numerical indicators for those values.   
     
     
       67. The regional oximeter system of claim 66, wherein the processor is further configured to produce timing signals to control the conditioning of the sets of signals by the first and second pre-amp units and to transmit the timing signals to the first pre-amp unit and to the second pre-amp unit, the first pre-amp unit and the second pre-amp unit being configured to condition the first set of signals and the second set of signals, respectively, using the timing signals. 
     
     
       68. The regional oximeter system of claim 66, wherein the first transmitter and the second transmitter are adapted to transmit the first light into the first tissue region and the second light into the second tissue region, respectively, based on timing signals from the processor that control light excitation sources for the first light and the second light. 
     
     
       69. The regional oximeter system of claim 66, wherein the display is configured to depict the regional oxygen saturation values of the first tissue region and the second tissue region using superimposed traces and event markers.