the present invention relates generally to a tissue oximetry device for measuring oxygen saturation in a local tissue volume . more specifically , the present invention relates to a wireless , handheld , tissue oximetry device that has self - contained optics ( lights sources and detectors ), computer processing , a display , a power - supply , and a tissue marker for marking tissue as the tissue is probed by the self - contained optics . fig1 a and 1b are a simplified perspective view and a top view , respectively , of a tissue oximetry device 100 according to one embodiment . the figures show an enclosure or housing of an oximeter probe device . tissue oximetry device 100 is configured to make tissue oximetry measurements , such as intraoperatively and postoperatively . in an implementation , the tissue oximetry device is handheld device and can make tissue oximetry measurements and display these measurements , without needing to connect to another external component either via a cable or wirelessly . the electronics to make measurements and calculations is contained entirely within the housing of the tissue oximetry device . the device may be a standalone handheld tissue oximetry device , without a cable or wireless connection . tissue oximetry device 100 may be a handheld device that includes a tissue oximetry probe 115 ( also referred to as a sensor head ), which may be positioned at an end of a sensing arm 114 . tissue oximetry device 100 is configured to measure the oxygen saturation of tissue by emitting light , such as red and near - infrared light , from tissue oximetry probe 115 into tissue , and collecting light reflected from the tissue at the tissue oximetry probe . tissue oximetry device 100 may include a display 112 or other notification device ( e . g ., a speaker for audible notification ) that notifies a user of oxygen saturation values measured by the tissue oximetry device . while tissue oximetry probe 115 is described as being configured for use with tissue oximetry device 100 , which is a handheld device , tissue oximetry probe 115 may be used with other tissue oximetry devices , such as a modular tissue oximetry device where the tissue oximetry probe is at the end of a cable device that couples to a base unit . the cable device might be a disposable device that is configured for use with a single patient and the base unit might be a device that is configured for repeated use . such modular tissue oximetry devices are well understood by those of skill in the art and are not described further . tissue oximetry device 100 does not require a pulsing blood flow to make an oxygen saturation measurement as compared with pulse oximeters that require a pulsing blood flow to make such measurements . while the description of the example embodiments is directed toward tissue oximetry probes that do not require a pulsing blood flow for oxygen saturation measurements , embodiments of the present invention are not so limited and may be utilized with pulse oximeters . fig1 c is a block diagram that shows tissue oximetry device 100 in further detail according to one embodiment . the components of device 100 are contained in a single enclosure or housing . tissue oximetry device 100 may include display 112 , a processor 116 , a memory 117 , a speaker 118 ( described briefly above ), one or more input devices 119 ( e . g ., one or more switches , input buttons , keypad , display 112 , if for example , the display is a touch screen , or the like ), a set of light sources 120 , a set of detectors 125 , a power source 127 , and a tissue marker 130 . processor 116 may be a microcontroller , a microprocessor , control logic , a multicore processor , or the like , and may control the operation of light sources 120 and detectors 125 . processor 116 may also control the operation of tissue marker 130 . memory 117 may include a variety of memories , such as a volatile memory 117 a ( e . g ., a ram ), a nonvolatile memory 117 ( e . g ., a disk , flash , prom , or others ), or both . user input may be by way of the input devices 119 ( e . g ., switches , touchpad , or the like ). power source 127 can be a battery , such as a disposable battery . disposable batteries are discarded after their stored charge is expended . some disposable battery chemistry technologies include alkaline , zinc carbon , or silver oxide . the battery has sufficient stored charged to allow use of the tissue oximetry device for several hours . after use , the tissue oximetry device is discarded . in other implementations , the battery can also be rechargeable where the battery can be recharged multiple times after the stored charge is expended . some rechargeable battery chemistry technologies include nickel cadmium ( nicd ), nickel metal hydride ( nimh ), lithium ion ( li - ion ), and zinc air . the battery can be recharged , for example , via an ac adapter with cord that connects to the handheld unit . the circuitry in the tissue oximetry device can include a recharger circuit ( not shown ). batteries with rechargeable battery chemistry may be sometimes used as disposable batteries , where the batteries are not recharged but disposed of after use . aspects of the invention may include software executable code or firmware ( e . g ., code stored in a read only memory or rom chip ). the software executable code or firmware may embody algorithms used in making oxygen saturation measurements of the tissue . the software executable code or firmware may include code to implement a user interface by which a user uses the system , displays results on the display , and selects or specifies parameters that affect the operation of the system . the components may be linked together via a bus 128 , which may be the system bus architecture of tissue oximetry device 100 . although this figure shows one bus that connects to each component , the busing is illustrative of any interconnection scheme serving to link these components or other components included in tissue oximetry device 100 . for example , speaker 118 , according to one specific implementation , could be connected to a subsystem through a port or have an internal direct connection to processor 116 . the foregoing listed components may be housed in a mobile housing ( see fig1 a ) of tissue oximetry device 100 . however , different implementations of tissue oximetry device 100 may include alternative housing ( such as the cables and the base units of modular oximeters described briefly above ) and may include any number of the listed components , in any combination or configuration , and may also include other components not shown . fig2 a is a simplified end view of tissue oximetry probe 115 according to one embodiment . tissue oximetry probe 115 is configured to contact tissue ( e . g ., a patient &# 39 ; s skin ) for which a tissue oximetry measurement is to be made . tissue oximetry probe 115 includes the set of light sources 120 and the set of detectors 125 . the set of light sources 120 may include two or more light sources , such as light sources 120 a and 120 b . light sources 120 may be linearly positioned across tissue oximetry probe 115 and detectors 125 may be arranged in an arc or a circle ( i . e ., circular arrangement ) on the tissue oximetry probe . more specifically , light sources 120 may be arranged linearly , such as on a line ( e . g ., a diameter ) that bisects a circle on which detectors 125 may be arranged . the light sources 120 a and 120 b are spaced a distance d1 apart where d1 may range from about 3 millimeters to about 10 millimeters . that is , the circle on which detectors 125 are arranged may have a diameter of about 3 millimeters to about 10 millimeters ( e . g ., 4 millimeters according to one specific embodiment ). while detectors 125 are described as being arranged in an arc or circle , tissue oximetry device 100 may have other configurations of detectors , such as linear , square , rectangular , ovoid , pseudo - random , or others . propagation depth increases with increasing source - to - detector distance , with 4 - 5 millimeters generally being a sufficient upper limit between light sources 120 a and detectors 125 to ensure few detected photons propagated in lower tissue layers . for example , these distances between light sources 120 and detectors 125 limits reflectance data to light that propagated within the top layer of tissue where little or no underlying subcutaneous fat or muscular layers contributes to the reflectance data . the set of detectors 125 may include four or more detectors . according to a specific embodiment , the set of detectors 125 includes eight detectors 125 a , 125 b , 125 c , 125 d , 125 e , 125 f , 125 g , and 125 h as shown . detectors 125 are solid - state detectors and may be mounted to a pcb ( not shown ). further , detectors 125 may be combined devices or discrete devices . in a specific implementation , detectors 125 are positioned with respect to outer light sources 120 a and 120 c such that four or more ( e . g ., fourteen ) unique source - to - detector distances are created . with greater numbers of source - to - detector distances , this can be used to obtain greater accuracy , faster calibration , and redundancy ( when duplicate source - to - detector distances are provided ). at least two source - to - detectors distances are 1 . 5 millimeters or closer , and at least two more two source - to - detectors distances are 2 . 5 millimeters or farther . in other words , a first source - to - detector distance is about 1 . 5 millimeters or less . a second source - to - detector distance is about 1 . 5 millimeters or less . a third source - to - detector distance is about 2 . 5 millimeters or greater . a fourth source - to - detector distance is about 2 . 5 millimeters or greater . there can be various numbers of sources and detector arrangements to obtain these four source - to - detector distances , such as one source and four detectors , two sources and two detectors , one detector and four sources , or other arrangements and combinations . for example , an implementation includes at least two sources and at least two detectors , where a maximum distance between a source and a detector is about 4 millimeters ( or about 5 millimeters ). at least two source - to - detector are about 2 . 5 millimeters or greater . at least two source - to - detector distances are about 1 . 5 millimeters or less . when a greater number of sources and detectors are used , greater numbers of source - to - detector distances are available . as discussed , these can be used to provide greater accuracy , faster calibration , or redundancy , or a combination . the arrangement of the sources and detectors can be in circular pattern , such as at points along the arc of a circle with radius ( e . g ., 4 millimeters , or 5 millimeters ). in an implementation , a tolerance of the detector or source positions on the arc is within 10 microns of the arc curve . in other implementations , the tolerance is within about 0 . 25 millimeters . turning now to tissue marker 130 , tissue oximetry probe 115 includes at least a dispenser portion of tissue marker 130 . fig2 shows an end view of the dispenser that can dispense a marking material on a local tissue region ( e . g ., of an extended portion of tissue ) that has been probed by tissue oximetry device 100 . the location of the marking material on tissue allows a user to subsequently identify the particular , local tissue region that has been probed . the dispenser may be located at a variety positions on the face of tissue oximetry probe 115 . according to one specific embodiment , the dispenser is located between light sources 120 a and 120 b , and may be located at the approximate center of the circular arrangement of detectors 125 . with the dispenser at the approximate center of light sources 120 and detectors 125 , a mark made by the dispenser will be substantially at a center of the local tissue region that has been probed by tissue oximetry device 100 . with the mark at the center of the probed tissue region , the mark is not displaced from the location on the local tissue region probed . according to one implementation , tissue marker 130 includes one or more dispensers that may be located at different positions on the head of tissue oximetry probe 115 . fig2 b shows an embodiment where two dispensers are located “ outside ” of light sources 120 and detectors 125 . that is , the dispensers are located at the ends of radii that are longer than the radii of light sources 120 and detectors 125 . further , the dispensers may lie on a line that passes through the center of the circle of the circular arrangement of dispensers 125 . with the dispensers located along such a line , marks made by these dispensers allow a user to readily identify the region between the marks as the local tissue region that has been probed by tissue oximetry device 100 . while the dispensers shown in fig2 a and 2b are shown as relatively localized devices ( e . g ., pen , pens , inker , inkers , and the like ) that may be configured to mark tissue with relatively small marks ( e . g ., dots ), a dispenser may be an extended device configured to make an extended mark , such as a line . for example , a dispenser may be an extended device configured to mark tissue with a circle or other closed shape , or may mark tissue with an open shape , such as a u - shape , a v - shape , or others . the dispenser may be fixed within tissue oximetry probe 115 or may be configured to be lowered when tissue is marked . various mechanical or electromechanical devices may be utilized by tissue oximetry probe 115 for lowering the dispenser . such mechanical and electro - mechanical devices are well understood by those of skill in the art and are not described in detail herein . tissue marker 130 may mark tissue with a variety inks having a variety of colors , such as gentian violet , which is the tissue marking ink approved by the fda . variations in the gentian violet chemistry constituents can give different characteristics to the ink and cause changes in color or shade . any of these colors or shades of gentian violet may be utilized by tissue marker 130 . one or more of the ink colors utilized by tissue oximetry device 100 may indicate one or more oxygen saturation ranges . for example , tissue marker 130 might be configured to : ( i ) mark tissue with a first color of ink if the tissue &# 39 ; s oxygen saturation is at or below a first threshold , ( ii ) mark the tissue with a second color of ink if the tissue &# 39 ; s oxygen saturation is above the first threshold and at or below a second threshold , and ( iii ) mark the tissue with a third color of ink if the tissue &# 39 ; s oxygen saturation is above the second threshold . the foregoing example describes the use of three colors of ink for marking tissue for visually identifying three ranges of oxygen saturation , however more or fewer colors may be utilized by tissue marker 130 for identifying more or fewer oxygen saturation ranges . processor 116 may determine the oxygen saturation of a local tissue region based on an analysis of the reflection data that has been generated by detectors 125 , and may control tissue marker 130 to mark the local tissue region with a select color of ink that identifies the range that the oxygen saturation is within . tissue marker 130 may include a variety of devices that provide marking material having one or more colors , such as ink reservoirs , pens , or the like . u . s . patent application ser . no . 12 / 178 , 359 , filed jul . 23 , 2008 , of heaton , titled “ oximeter with marking feature ”, which is incorporated by reference in its entirety , describes a variety of devices that are configured for marking tissue with one or more colors of marking material . a reservoir of the marking device can be connected to the dispenser , such as through tubing or channels , and is contains ink or other fluid ( e . g ., ink ) dispensed through the dispenser . ink can be urged from the reservoir to and through the dispenser and deposited on skin through pressure or low - frequency sound ( such using a piezoelectric transducer ). the reservoir is contained within the same housing as the processor , battery , sources , detectors , and other components of the oximeter probe . for the disposable probe , the reservoir is not refillable . according to one alternative , tissue marker 130 , under control of processor 116 , marks tissue for one or more oxygen saturation ranges , but does not mark the tissue for one or more other oxygen saturation regions . for example , tissue marker 130 might mark a local tissue region if the oxygen saturation of the local tissue region is at or below a threshold level , or alternatively might not mark the local tissue region if the oxygen saturation level is above the threshold level . markings that are made on tissue according to the above method allow a user to relatively quickly identify tissue that might have a low chance of viability if the threshold level is relatively low . alternatively , tissue marker 130 might mark a local tissue region if the oxygen saturation of the local tissue region is at or above a threshold level , and might not mark the local tissue region if the oxygen saturation level is below the threshold level . marks made from this method allow a user to relatively quickly identify tissue that might have a relatively high chance of viability if the threshold level is relatively high . information for the foregoing described threshold levels ( i . e ., ranges ) may be stored in memory 117 and accessed by processor 116 for use . the threshold levels may be stored in memory 117 during manufacture of tissue oximetry device 100 , or may be stored in the memory thereafter . for example , tissue oximetry device 100 may be configured to receive a user input for one or more user defined threshold levels and store information for these threshold levels in memory 117 . one or more input devices 119 ( or the like ) may be configured to receive a user input for a user defined threshold level and for storing the user defined threshold level in memory 117 . fig3 is a high - level flow diagram of a method for marking tissue to indicate ranges of oxygen saturation of the tissue . the high - level flow diagram represents one example embodiment . steps may be added to , removed from , or combined in the high - level flow diagram without deviating from the scope of the embodiment . at 300 , tissue oximetry probe 115 contacts the tissue . light ( e . g ., near - infrared light ) is emitted from one or more of the light sources 120 , step 305 , into the tissue and at least some of the light is reflected back by the tissue . each detector 125 receives a portion of the light reflected from the tissue , step 310 , and each detector generates reflectance data ( i . e ., a response ) for the portion of reflected light received , step 315 . at 320 , processor 305 determines an oxygen saturation value for the tissue based on the reflectance data . at 325 , processor 116 determines a range of oxygen saturation from a plurality of ranges of oxygen saturation in which the oxygen saturation lies . at 330 , processor 116 controls tissue marker 130 to mark the tissue with ink based on a range in which the oxygen saturation is in . for example , the processor may be configured to control the dispenser to mark the tissue with ink if the oxygen saturation is in a first range of oxygen saturation , but not mark the tissue if the oxygen saturation in a second range of oxygen saturation where the first range and second range are different , such as not overlapping ranges . while the foregoing example embodiment , discusses the utilization of two ranges of oxygen saturation by the tissue oximetry device , the tissue oximetry device may utilize more than two ranges of oxygen saturation for determining whether to mark the tissue with ink . according to one embodiment , the processor may control the dispenser to mark the tissue with a specific color of ink based on the range of oxygen saturation that the oxygen saturation is in . the particular color of ink allows a user to relatively quickly determine the ranges of oxygen saturation for the tissue without the need for re - probing the tissue or looking at a chart of the tissue that includes oxygen saturation values and matching the chart to the tissue . tissue oximetry device 100 may be configured to allow a user to manually control the tissue oximetry device to mark tissue , allow processor 116 to control marking the tissue , or both . for example , one of input devices 119 may be configured to control tissue marker 130 to mark a local tissue region if a user activates the input device . the input device may be conveniently located for a user to operate tissue oximetry device 100 to make an oxygen saturation measurement , and operate the input device without moving tissue oximetry probe 115 from the local tissue region that was probed . tissue oximetry device 100 may be switched between the processor controlled method of marking tissue and the manually controlled method ( e . g ., activating one of the switches ) of marking tissue . one or more other of input devices 119 may be configured for switching tissue oximetry device 100 between these two methods of marking tissue . this description of the invention has been presented for the purposes of illustration and description . it is not intended to be exhaustive or to limit the invention to the precise form described , and many modifications and variations are possible in light of the teaching above . the embodiments were chosen and described in order to best explain the principles of the invention and its practical applications . this description will enable others skilled in the art to best utilize and practice the invention in various embodiments and with various modifications as are suited to a particular use . the scope of the invention is defined by the following claims .
an intraoperative tissue oximetry device includes a tissue marker that includes one or more pens or one or more similar ink sources , such that the tissue marker can mark tissue according to oxygen saturation measurements made by the tissue oximetry device , thereby visually delineating regions of potentially viable tissue from regions of potentially nonviable tissue .