Patent Publication Number: US-2020275841-A1

Title: Non-contact core body temperature measurement systems and methods

Description:
RELATED APPLICATIONS 
     Any and all applications for which a domestic priority claim is identified in the Application Data Sheet of the present application are hereby incorporated by reference under 37 CFR 1.57. This application is related to U.S. application Ser. No. ______, filed on ______, having an attorney docket number MAS.1248A, titled “Respiratory Core Body Temperature Measurement Systems and Methods” and U.S. application Ser. No. 16/546,667, filed on Aug. 1, 2019, titled “Core Body Temperature Measurement,” entirety of which are incorporated by reference herein. 
    
    
     FIELD 
     The present disclosure relates to systems and methods of calculating estimated core body temperature. 
     BACKGROUND 
     Temperature is often a good indicator of patient health. Temperatures that are too low or high can negatively impact patient&#39;s metabolic rate, organ function, or cause tissue damage. Accurately measurement and monitoring of temperature of a patient, therefore, can be vital to care providers. Although one&#39;s temperature in peripheral regions (including, for example, hands, feet, legs, and arms) can vary (between 27° C. and 32° C.), the core temperature of deep tissues and internal organs remain relatively constant (between 36.5° C. and 37.2° C.). By measuring or observing changes in core temperature, harmful conditions such as infections, cardiac arrest, stroke, or other types of trauma can be observed. 
     SUMMARY 
     The present disclosure provides systems and methods of determining estimated core body temperature without direct physical contact with the patient. A sensor system can include a temperature sensor that determines skin temperature of a patient. In some examples, the sensor system also measures an ambient temperature. The sensor system can use the skin temperature or ambient temperature to calculate an estimated core body temperature. The sensor system can include a display module that can display the estimated core body temperature in different color schemes based on the estimated core body temperature reading. The sensor system can include one or more indicators that allow care providers to orient the sensor system at a correct distance away from the patient for more accurate measurements. 
     According to an aspect, a method for calibrating a sensor is disclosed. The method can include measuring, using a sensor, a first observed temperature of a first reference object having a first actual temperature, a second observed temperature of a second reference object having a second actual temperature, a third observed temperature of a third reference object having a third actual temperature, and a fourth observed temperature of a fourth reference object having a fourth actual temperature. The method can further include determining a difference between the first actual temperature and the first observed temperature as a first bias, a difference between the second actual temperature and the second observed temperature as a second bias, a difference between the third actual temperature and the third observed temperature as a third bias, and a difference between the fourth observed temperature and the fourth actual temperature as a fourth bias. The method can further include determining an offset for the sensor based at least on the first bias, the second bias, the third bias, and the fourth bias. 
     The first reference object can be a physical body at a thermal equilibrium. The second reference object can be a gallium triple point black body. The third reference object can be water in a water bath. The fourth reference object can be an infrared reference source with controlled temperature. 
     According to another aspect, a system for displaying a distance indicator associated with a distance between a temperature measurement system and a patient is disclosed. The system can include a first display module that can generate a first indicator. The first indicator can be projected at a first angle from a temperature measurement system towards a patient. The system can further include a second display module that can generate a second indicator. The second indicator can be projected at a second angle from the temperature measurement system towards the patient. The first indicator and the second indicator can intersect at a predetermined distance from the temperature measurement system such that the first indicator and the second indicator generate a third indicator projected on the patient when the temperature measurement system is positioned at the predetermined distance from the patient. The first indicator and the second indicator can be separately projected on the patient when the temperature measurement system is not positioned at the predetermined distance from the patient. 
     The first display module and the second display module can be positioned a first distance apart from each other. The first distance can be based at least on the first angle, the second angle, and the predetermined distance. The first indicator can be a first beam of light in a first color and the second indicator can be a second beam of light in a second color. The third indicator can be in a third color different from the first color and the second color. The first indicator and the second indicator can be associated with temperature of a patient. 
     According to another aspect, a system for displaying a distance indicator associated with a distance between a temperature measurement system and a patient is disclosed. The system can include one or more sensors that can collect a first plurality of data associated with temperature of a patient. The system can further include a processor that can calculate estimated core body temperature of the patient using the first plurality of data. The system can further include a first display module that can generate a first indicator that can be projected on the patient. The first indicator can display a first display when a temperature measurement system is at a first distance from a patient. The first indicator can display a second display when the temperature measurement system is at a second distance from the patient. The first indicator can be associated with the estimated core body temperature of the patient. The second distance can be different from the first distance. The first display can be illegible and the second display can be legible. 
     The first indicator can be in a first color. The first color can be based at least on the estimated core body temperature of the patient. 
     According to another aspect, a system for determining an estimated core body temperature is disclosed. The system can include a hardware processor programmed to execute software instructions. The hardware processor can cause the system to receive a first plurality of data from a first sensor. The hardware processor can further cause the system to discard a first subset of the first plurality of data based at least on signal density distribution of the first plurality of data. The hardware processor can further cause the system to discard a second subset of the first plurality of data based at least on signal quality index of the first plurality of data. The hardware processor can further cause the system to receive a second plurality of data from a second sensor. The second plurality of data can be associated with ambient temperature. The hardware processor can further cause the system to calculate an estimated core body temperature based at least on a remainder of the first plurality of data and the second plurality of data. 
     The first plurality of data can be associated with skin temperature of a patient. The first subset of the first plurality of data can represent data within the first plurality of data that is not within a predetermined range of signal density of the first plurality of data. The second subset of the first plurality of data can represent data within the first plurality of data that has signal quality index lower than a predetermined value. 
     According to another aspect, a system for generating a display associated with temperature of a patient is disclosed. The system can include one or more sensors that can generate a plurality of data associated with temperature of a patient. The system can further include a processor operatively connected to the one or more sensors to receive the plurality of data from the one or more sensors. The processor can be programmed to execute software instructions to calculate an estimated core body temperature of the patient. The system can further include a display module operatively connected to the processor. The display module can generate and display an indicator associated with the estimated core body temperature. The indicator can include a first variable characteristic based at least on the estimated core body temperature. 
     The first variable characteristic can be a color of the indicator. The indicator can have a second variable characteristic based at least on the estimated core body temperature. The second variable characteristic can be a frequency at which the indicator is displayed. The indicator can blink at a predetermined frequency when the estimated core body temperature is above a threshold temperature. 
     According to another aspect, a temperature measurement system for determining an estimated core body temperature is disclosed. The temperature measurement system can include a first sensor that can collect a first plurality of data associated with temperature of a patient. The temperature measurement system can further include a light emitter for emitting a first beam of light towards the patient. The temperature measurement system can further include a light detector for detecting a second beam of light from the patient. The temperature measurement system can further include an aperture. The temperature measurement system can further include a cover for the aperture, the cover having an open configuration and a closed configuration, the cover in the open configuration allowing the first beam of light and the second beam of light to travel between the temperature measurement system and the patient, the cover in the closed configuration preventing the first beam of light and the second beam of light from travelling between the temperature measurement system and the patient. The temperature measurement system can further include a processor in electronic communication with the first sensor, the light emitter, and the light detector, the processor can calculate an estimated core body temperature of the patient based at least on the first plurality of data, the processor can determine a distance between the temperature measurement system and the patient based at least on the second beam of light. The temperature measurement system can further include a display module that can generate a first indicator projected on the patient, the first indicator having a first configuration when the temperature measurement system is at a predetermined distance from the patient and having a second configuration when the temperature measurement system is not at the predetermined distance from the patient. 
     The second beam of light can include at least a portion of the first beam of light reflected by the patient. The cover can provide a waterproof or water-resistant seal for the aperture. The cover can be a mechanical flap. The light detector can determine an intensity of the second beam of light. The light detector can determine an incident position of the second beam of light. The processor can determine the distance between the temperature measurement system and the patient based at least on the intensity or the incident position of the second beam of light. 
     The first sensor can be an infrared light sensor. The light emitter can be an infrared light sensor. The first indicator can represent an estimated core body temperature of the patient. The first indicator can be legible when in the first configuration and illegible when in the second configuration. The first indicator in the first configuration and the first indicator in the second configuration can differ in color. The light emitter and the light detector can be housed within the aperture. The aperture can have a substantially parabolic cross-section. The substantially parabolic cross-section of the aperture can aid in focusing the second beam of light towards the light detector. 
     According to another aspect, a method of generating a display indicative that a temperature measurement system is at a recommended distance from a patient is disclosed. The method can include actuating a cover to expose the aperture. The method can further include emitting, using a light emitter, a first beam of light towards the patient. The method can further include detecting, using a light detector, a second beam of light from the patient. The method can further include analyzing the second beam of light to determine a first distance between the temperature measurement system and the patient. The method can further include comparing the first distance to a predetermined range. The method can further include generating and displaying a first indicator upon determination that the first distance is not within the predetermined range. The method can further include generating and displaying a second indicator upon determination that the first distance is not within the predetermined range. 
     The analyzing the second beam of light can include determining an intensity of the second beam of light. The analyzing the second beam of light cam include determining an incident position of the second beam of light. The actuating the cover can include changing a configuration of the cover from a closed configuration to an open configuration. The cover in the open configuration can allow the first beam of light and the second beam of light to travel between the temperature measurement system and the patient, and the cover in the closed configuration can prevent the first beam of light and the second beam of light from travelling between the temperature measurement system and the patient. 
     The systems and methods for obtaining and monitoring estimated core body temperature disclosed herein have several features, no single one of which is solely responsible for their desirable attributes. Without limiting the scope as expressed by the claims that follow, certain features of the temperature system will now be discussed briefly. One skilled in the art will understand how the features of the disclosed technology provide several advantages over traditional systems and methods. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various examples will be described hereinafter with reference to the accompanying drawings. The drawings and the associated descriptions are provided to illustrate examples of the present disclosure and do not limit the scope of the claims. In the drawings, similar elements have similar reference numerals. 
         FIG. 1A  illustrates an embodiment of a sensor system collecting data associated with temperature of a patient. 
         FIG. 1B  illustrates an example schematic diagram of the sensor system of  FIG. 1B . 
         FIG. 2A  illustrates a block diagram for an example method of calculating an estimated core body temperature. 
         FIG. 2B  illustrates another example method of calculating an estimated core body temperature. 
         FIG. 3A  is a graphical illustration of an example method of data noise reduction. 
         FIG. 3B  illustrates another example method of data noise reduction. 
         FIG. 4  illustrates an example method of filtering data using signal quality index. 
         FIG. 5A  illustrates an example method of calculating an estimated core body temperature. 
         FIG. 5B  illustrates a theoretical model for the method of calculating an estimated core body temperature of  FIG. 5A . 
         FIG. 5C  illustrates another example method of calculating an estimated core body temperature. 
         FIG. 6  illustrates an example method of displaying an estimated core body temperature. 
         FIG. 7  illustrates an example method of orienting a sensor system with respect to a patient. 
         FIG. 8A  is a block diagram illustrating of an example sensor system including an optical module. 
         FIG. 8B  is a block diagram illustrating the example optical module of  FIG. 9A . 
         FIG. 9  illustrates an example method of generating and displaying an indication that the temperature measurement system is at a recommended distance from a patient. 
     
    
    
     While the foregoing “Brief Description of the Drawings” references generally various examples of the disclosure, an artisan will recognize from the disclosure herein that such examples are not mutually exclusive. Rather, the artisan would recognize a myriad of combinations of some or all of such examples. 
     DETAILED DESCRIPTION 
     Temperature Measurement System 
     Although certain examples of temperature measurement system are described herein, this disclosure extends beyond the specifically disclosed examples and/or uses and obvious modifications and equivalents thereof. Thus, it is intended that the scope of this disclosure should not be limited by any particular examples described below. 
       FIG. 1A  illustrates an example of a non-contact temperature measurement system  110  for measuring temperature of a patient  100  by taking a temperature measurement at the patient&#39;s forehead. The temperature measurement system  110  may include one or more sensors that can collect data associated with temperature of a patient. In some examples, the one or more sensors of the temperature measurement system  110  may be an infrared temperature sensor that can collect data associated with temperature of a patient without being in contact with the patient. Taking temperature measurement at the patient&#39;s forehead can be advantageous because it allows care providers to measure patient temperature without having to reorient or move patients. In some examples, the temperature measurement system  110  may provide more accurate reading when positioned at a recommended distance from the patient  100 . The temperature measurement system may be Rad-G™ Pulse Oximeter available at Masimo Corporation, Irvine, Calif. 
     In some examples, the temperature measurement system  110  may be in contact with a patient when determining temperature of a patient. Various examples of contact-based temperature measurement systems are disclosed in U.S. application Ser. No. ______, filed on ______, having an attorney docket number MAS.1248A, titled “Respiratory Core Body Temperature Measurement Systems and Methods,” entirety of which is incorporated by reference herein. 
       FIG. 1B  illustrates a block diagram of the temperature measurement system  110  shown in  FIG. 1A . The temperature measurement system  110  can include a processor  120 , a sensor  130 , a display module  140 , and a communication module  150 . The processor  120  can be operatively connected to the sensor  130 , the display module  140 , and the communication module  150  such that it can receive signals from or transmit signals to the sensor  130 , the display module  140 , and the communication module  150 . 
     The display module  140  can receive signals from the processor  120  and generate displays associated with temperature of a patient. The displays generated by the display module  140  may be based at least in part on the signals transmitted by/from the processor  120 . For example, the display module  140  can generate and display numerical temperature readings of the patient. Optionally, the display module  140  can generate displays with different characteristics including, but not limited to, color, blinking frequency, and the like. For example, when patient temperature is above a recommended value or a predetermined threshold, the display module  140  may display temperature readings in red. In this regard, care providers and others can advantageously identify temperature readings greater than a recommended value or a predetermined threshold. Likewise, the display module  140  may display temperature readings in green when patient temperature is at or below the recommended value or the predetermined threshold. In other examples, the display module  140  can use different types or patterns of blinking to display temperature readings above the recommended value or the predetermined threshold. 
     The display module  140  can further display information associated with the orientation of the temperature measurement system  110 . The orientation of the temperature measurement system  110  may be determined with respect to the patient  100 . The display module  140  can generate displays that indicate whether the temperature measurement system  110  is at a recommended distance from the patient  100 . This can be advantageous since some sensors require the sensor to be at a certain, recommended distance from a heat source to accurately measure temperature of the heat source. Further information regarding the display module  140  and the displays generated by the display module  140  is described herein. 
     In some examples, the display module  140  may generate displays that may be legible when the distance between the temperature measurement system  110  and the patient satisfies a condition. The condition may be associated with a predetermined distance value (for example, 10 inches). The condition may be changed by users, for example, care providers. 
     The communication module  150  can allow the temperature measurement system  110  to communicate with other sensor systems  110  or devices. For example, the temperature measurement system  110  can communicate with nearby pulse oximeter sensors via the communication module  150  to receive data related to patient blood perfusion. This can be advantageous since blood perfusion can be related to core body temperature of the patient and therefore affect calculation of the estimated core body temperature. The communication module  150  may be capable of establishing one or more types of wireless communications including, but not limited to, near-field communication, Wi-Fi, Li-Fi, LTE, 3G, 4G, and the like. In some examples, the temperature measurement system  110  may wirelessly store data in a remote server via wireless communication established by the communication module  150 . 
     Types of Sensors 
     The sensor(s)  130 , as described herein, may be able to generate data associated with the temperature of a patient. The sensor  130  may be an infrared (IR) sensor capable of detecting or measuring infrared radiation from an object. In a non-limiting example, the sensor  130  can detect infrared radiation and convert that infrared radiation into an electronic signal (including, for example, current or voltage) that correspond to the amount of infrared radiation. The sensor  130  can be an active or passive infrared sensor. 
     In some examples, the sensor  130  may be an infrared thermometer for non-contact temperatures measurements (for example, MLX090614 manufactured by Melexis Technologies NV, Tessenderlo, Belgium). In some examples, the sensor  130  may include a thermal relay that can allow an easy and cost effective implementation in temperature alert applications. A temperature threshold associated with temperature alerts may be programmable by a user, for example, a care provider. In some examples, the sensor  130  may include an optical filter to filter the visible or near infrared radiant flux. Such optional filter may be integrated into the sensor  130 . 
     Temperature Measurements 
     As discussed above, the sensor  130  may measure infrared radiation from an object. In the example shown in  FIG. 1A , the sensor  130  of the temperature measurement system  110  can measure infrared radiation from a patient&#39;s forehead. In other examples, the sensor  130  of the temperature measurement system  110  can measure infrared radiation from other parts of patient&#39;s body including, but not limited to, armpit, groin, and the like. 
     In some examples, the sensor  130  may measure ambient temperature in addition to measuring infrared radiation from a patient. The ambient temperature and the temperature of the patient can be used to calculate estimated core body temperature of the patient. Calculation of the estimated core body temperature using the ambient temperature and the patient temperature is further described herein. 
     Calculating Estimated Core Body Temperature 
     As discussed above, core body temperature serves as an important indicator of one&#39;s health. However, core body temperature can be difficult to measure or estimate. Although there are many methods to measure temperature that are proxy to core body temperature, their accuracy, latency, and invasiveness can vary greatly. For example, while measuring temperature in the pulmonary artery can often provide the great accuracy in estimating core body temperature, it is one of the most invasive methods. In another example, while measuring temperature at the eardrum provides low latency, low invasiveness, and great comfort for patients, it suffers from low accuracy. Therefore, it may be advantageous to provide a non-invasive method that can accurately estimate core body temperature. 
     In some examples, ambient temperature measurements and skin temperature measurements may be used to estimate core body temperature. Skin temperature measurements may be taken at a forehead of a patient as shown in  FIG. 1A . In other examples, reference temperature measurements and skin temperature measurements may be used to estimate core body temperature. 
     Referring to  FIGS. 2A and 2B , an example method of calculating estimated core body temperature is disclosed. As described herein, the sensor  130  may collect temperature data associated with a patient. For example, the temperature data may be raw temperature data (for example, T s ) associated with surface temperature of the skin of a patient. In some examples, the temperature data is collected from the forehead of a patient. Once the sensor  130  collects the temperature data, the temperature data can be transmitted to the processor  120  of the temperature measurement system  110 . 
     As shown in  FIG. 2A , the processor  120  may apply one or more processing methods including, for example, noise reduction and signal quality filtering. Such signal processing methods can advantageously improve the quality of the temperature data and allow for more accurate calculation of estimated core body temperature. At block  220 , the processor  120  may reduce noise in the temperature data by removing data points that do not satisfy a predetermined condition. The predetermined condition may be provided by a care provider or by a manufacturer of the temperature measurement system. In some examples, the predetermined condition may be a tolerance associated with the sensor  130 . In some examples, the tolerance may be specific to different sensors. In some examples, the tolerance may be an index associated with a standard deviation of a data collected by the sensor  130 . 
     At block  230 , the processor  120  can calculate signal quality index for filtering the temperature data collected by the sensor  130 . The signal quality index may compared to a predetermined condition to determine whether to remove or keep respective, corresponding data point. If the predetermined condition is not satisfied, the data point may not be used to estimate core body temperature. On the other hand, if the predetermined condition is satisfied, the data point may be used to estimate the core body temperature. In some examples, the predetermine condition may be satisfied if the signal quality index is above a threshold. 
     At block  240 , the processor  120  can determine corrected (or adjusted) surface temperature (for example, skin temperature at the forehead of a patient) based at least in part on the processed temperature data. Optionally, the correction may also be based at least in part on temperature data indicative of ambient temperature (for example, T aux  in  FIG. 2A ). The temperature data indicative of ambient temperature (T aux ) may be the actual ambient temperature or a proxy representative of the ambient temperature. The temperature indicative of ambient temperature may be collected by the sensor  130  or another temperature sensor. 
     At block  250 , the processor  120  can calculate estimated core body temperature (for example, T b  in  FIG. 2A ) based at least in part on the corrected surface temperature. Optionally, the estimated core body temperature may be determined based at least in part on the corrected surface temperature and the temperature indicative of ambient temperature, for example, collected by the sensor  130 . Alternatively and/or optionally, the processor  120  may receive actual ambient temperature data from an ambient sensor  260  the estimated core body temperature may be determined based at least in part on the actual ambient temperature data. 
       FIG. 2B  illustrates an example method  200  of calculating estimated core body temperature. At block  202 , the temperature measurement system  110  can receive raw temperature data from the sensor  130 . The raw temperature data may be indicative of surface temperature of skin of a patient. The raw temperature data can be temperature measurements collected at the forehead of the patient, as shown in  FIG. 1A . The sensor  130 , for example, can be an IR sensor. 
     The patient temperature data, for example, T s  as shown in  FIG. 2A , can be collected at a predetermined frequency that can be between about 1 Hz and about 10 kHz, between about 5 Hz and about 5 kHz, between about 10 Hz and about 1 kHz, between about 100 Hz and about 500 Hz, between about 200 Hz and about 400 Hz, or about 1 Hz, 5 Hz, 10 Hz, 50 Hz, 100 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 5 kHz, 10 kHz, or range between any two of aforementioned values, and the like. The patient temperature data can be a raw data (including, for example, voltage or current) or processed data. 
     The processor  120  of the temperature measurement system  110  may process the raw temperature data (for example, T s  in  FIG. 2A ) prior to calculating or determining estimated core body temperature (for example, T b  in  FIG. 2A ). At block  204 , inaccurate measurements or measurements not within a specified tolerance may be discarded using noise reduction process, as generally described herein in reference to block  220  of FIG.  2 A. The processor  120  may compare sensor measurements (for example, temperature data) to a predetermined threshold condition to determine whether measurements may be inaccurate or not within a specified tolerance. In some examples, such predetermined threshold condition or such specific tolerance may be provided during manufacture of the sensors, for example, the sensor(s)  130 . At block  206 , measurements with signal quality index below a predetermined threshold value may be discarded, as generally described herein in reference to block  230  of  FIG. 2A . Additional details of noise reduction process and monitoring of signal quality is described herein. 
     At block  208 , the temperature measurement system  110  can receive temperature data indicative of ambient temperature of the area surrounding the patient. The temperature data indicative of the ambient temperature may be the actual ambient temperature or a proxy representative of the ambient temperature. The proxy representative of the ambient temperature may be, for example, a thermal gradient within the sensor  130  that can be used to adjust or compensate temperature measurements (for example, T s ). Optionally, one or more sensors different from the sensor  130 , for example, separate from the temperature measurement system  110 , may measure and provide temperature data indicative of the ambient temperature. In some examples, the ambient temperature may be measured or estimated by the sensor  130 . 
     At block  209 , the temperature measurement system  110  (or the processor  120  of the temperature measurement system  110 ) may calculate corrected skin temperature, as generally described herein in reference to block  240  of  FIG. 2A . The corrected skin temperature may be calculated based at least in part on the temperature data indicative of ambient temperature and filtered or processed raw temperature data. At block  210 , the temperature measurement system  110  can calculate the estimated core body temperature of the patient, as generally described herein in reference to block  250  of  FIG. 2A . The estimated core body temperature may be calculated based at least in part on the corrected skin temperature and the temperature data indicative of ambient temperature. Optionally, in some examples, the estimation of core body temperature can be done based at least in part on the ambient temperature. The ambient temperature may be determined by the sensor  130 , another sensor, or a device other than the temperature measurement system  110 . 
     In some examples, multiple temperature measurements may be used to estimate core body temperature. In some examples, the multiple temperature measurements may be taken at one or more different parts or locations of a patient&#39;s body. Various examples of systems and methods of estimating core body temperature using multiple temperature measurements is disclosed in U.S. application Ser. No. 16/546,667, filed on Aug. 1, 2019, titled “Core Body Temperature Measurement,” entirety of which is incorporated by reference herein. 
     Noise Reduction 
     Although an IR sensor may provide a non-invasive method to measure temperature, its measurements can include noise that may not accurately represent patient temperature. Therefore, it may be advantageous to identify and remove noise from temperature data (including, for example, ambient temperature measurements and skin temperature measurements) using notice reduction methods. 
       FIG. 3A  shows an exemplary signal distribution graph  300 , which illustrates distribution of the patient temperature data. In the example signal distribution graph  300 , the y-axis represents signal density while the x-axis represents a delta between each data point of the patient temperature data and a mean value of the patient temperature data. The highlighted portion of the graph  300  may illustrate a subset  302  of the patient temperature data that may be determined or categorized as noise. The non-highlighted portion of the graph  300  may illustrate a subset  304  of the patient temperature data that may not be determined or categorized as noise. In some examples, the subset  304  of the temperature data may be used to estimate core body temperature. In some examples, the subset  302  may be determined using the distribution of the temperature data. In some examples, the subset  302  can be determined using other methods such as data smoothing, moving average filtering, Savitzky-Golay filtering, local regression filtering, robust local regression, and the like. 
       FIG. 3B  illustrates an example method  310  of reducing noise in the patient temperature data. At block  312 , a mean of the patient temperature data is calculated. At block  314 , differences between the mean and each data point of the patient temperature data are calculated. The differences between the first mean and each data point of the patient temperature data may be positive or negative. At block  316 , a distribution of the difference (between the first mean and each data point of the patient temperature data) is determined. 
     At block  318 , a subset of the patient temperature data may be identified, for example, the subset  304 . In some examples, standard deviation from the mean may be used to identify data points to be included in the subset. For example, the subset may include data points that are within plus/minus one standard deviation from the mean, two standard deviations from the mean, three standard deviations from the mean, and the like. Once the subset is identified, data points that are not within the subset may be discarded at block  320 . At block  322 , another mean may be calculated using the subset identified at block  318 . The mean calculated at block  322  may be used to determine a patient temperature reading. 
     Signal Quality Index 
     In some examples, the patient temperature data can be filtered using signal quality index (SQI). Using SQI to filter temperature data can be advantageous by discarding relatively inaccurate data and thereby achieving more accurate temperature reading of a patient. 
       FIG. 4  illustrates an example method  400  to filter data using SQI. At block  402 , sensor tolerance is determined. Sensors can have tolerances that define total allowable error for sensor measurements. At block  404 , standard deviation of the patient temperature data is calculated. At block  406 , signal quality index is calculated for the patient temperature data. In some examples, the signal quality index (SQI) may be calculated using at least the sensor tolerance and the standard deviation of the patient temperature data. An exemplary equation for calculating the SQI is shown below. 
     
       
         
           
             SQI 
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     In the equation shown above, SQI increases as standard deviation of the data becomes less than the tolerance of the sensor  130 . On the other hand, SQI decreases as standard deviation of the data becomes greater than the tolerance of the sensor  130 . At block  408 , SQI of the patient temperature data may be compared to a predetermined threshold value. For example, the predetermined value can be  100 . In some examples, care providers can provide or change the predetermined threshold value for SQI. If SQI is greater or equal to the predetermined threshold value, the patient temperature data may not be discarded at block  414 . If SQI is less than the predetermined threshold value, the patient temperature data can be discarded at block  412 . In some examples, the predetermined threshold value for SQI may vary over time or depend on patients or types of sensors used for temperature data measurement. 
     Physical Model 
     Referring to  FIGS. 5A-5B , a core body temperature may be estimated using a physical model. An example of a physical model may use an ambient temperature (T a ) and a skin temperature (T s ) of a patient to estimate core body temperature (T b ) the patient. The skin temperature may be measured at a forehead of a patient as shown in  FIG. 1A . An exemplary method  500  of estimating core body temperature is shown in  FIG. 5A . 
     At block  502 , T s  and T a  are used to calculate convection heat transfer between the patient (for example, forehead of the patient) and the ambient surrounding. At block  504 , T s  and T a  are used to calculate radiation heat transfer. At block  508 , a core body temperature can be estimated using the convection heat transfer and the radiation heat transfer. 
     Optionally, a local heat flux may be estimated or calculated using a local skin perfusion rate at block  506 . Local skin perfusion rate (for example, at a forehead of a patient) can change the amount of heat transfer between the skin and the air. For example, an increase in core body temperature can increase skin perfusion rate, thereby increasing heat transfer between the body and the skin and between the skin and the air. 
       FIG. 5B  illustrates an example physical model  520  that may be used to estimate core body temperature  526  (T b ) of body  538  using ambient temperature  522  (T a ) of air  540  and skin temperature (or surface temperature)  524  (T s ) of skin  536  of a patient. In the physical model  520 , three different types of thermal heat flux may be identified: conductive heat transfer  532  (q 1 ) between the body  538  and the skin  536 , convective heat transfer (q 2 ) between the skin  536  and the air  540 , and radiative heat transfer (q 3 ) between the skin  536  and the air  540 . In some examples, the conductive heat transfer, the convective heat transfer, and the radiative heat transfer may be calculated using the following equations: 
     
       
         
           
             
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     where k γ  represents thermal conductivity of human skin, L represents thickness  534  of the skin  536 , h ra  represents convective heat transfer coefficient of an ambient air, ϵ γ  represents emissivity coefficient of human skin, and σ represents the Stefan-Boltzmann Constant (i.e., 5.6703*10 −8  (W/m 2 K 4 ). Under a thermal equilibrium between the body, the skin, and the ambient surrounding, any heat transfer between the body and the skin can be equal to heat transfer between the skin and the ambient air. In other words, under thermal equilibrium, q 1  can be equal to a sum of q 2  and q 3 . Using the above equations and known coefficients, core body temperature (T b ) may be calculated using equations shown below. 
     
       
         
           
             
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     Regression Model 
     Different methods may be used to estimate core body temperature of a patient. In a non-limiting example, linear regression may be used to estimate core body temperature of a patient.  FIG. 5C  illustrates an example method  580  to estimate core body temperature using a regression model between reference body temperature measurements and skin temperature measurements. At block  582 , reference body temperature measurement can be collected. The reference temperature measurements may be collected at different locations of a patient&#39;s body such as eardrum and mouth. The reference temperatures can be proxy to core body temperature. At block  584 , skin temperature measurements can be collected. At block  586 , a mathematical model describing the relationship between the reference temperature measurements and the skin temperature measurements may be generated. In a non-limiting example, following exemplary regression model may be used between the reference temperature (T b ) and the skin temperature (T s ). 
         T   b = a   N * T   s   N + a   N−1 * T   s   N−1 + . . . + a   2 * T   s   2 + a   1 * T   s + btas    
     Once the coefficients (for example, a n , a n−1 , a n−2 , . . . a 2 , a 1 ) and the bias is determined, skin temperature may be used to estimate body temperature at block  588 . In some examples, the coefficients and the bias may be specific to a patient. In other words, the coefficients and the bias may vary between different patients. In this regard, reference temperatures may be needed to determine the coefficients and the bias for an estimation model. 
     Display 
     Once estimated core body temperature is determined, it may be advantageous to display the estimated core body temperature to allow care providers and others to easily identify a temperature reading that is not within the normal range (for example, between 36.1° C. and 37.2° C. or 97° F. and 99° F.). In some examples, the estimated core body temperature may be displayed on a screen on the temperature measurement system  110  or projected on the patient  100  while collecting the temperature measurements. For example, the estimated core body temperature may be displayed or projected on a patient&#39;s forehead while the temperature measurement system  110  measures temperature at the patient&#39;s forehead. This configuration can be advantageous because it allows care providers to measure and record patient temperature without having to take their eyes off of the patient. 
       FIG. 6  illustrates an example method  600  of displaying core temperature. At block  602 , ambient temperature measurements and patient temperatures measurements can be collected as described herein. At block  604 , estimated core body temperature can be calculated using methods or systems described herein. At block  606 , temperature display can be generated based at least on the calculated estimated core body temperature. At block  608 , the estimated core body temperature is displayed. In some examples, the estimated core body temperature may be displayed on a screen of the temperature measurement system  110 . In some examples, the estimated core body temperature may be displayed or projected on a surface. For example, the estimated core body temperature may be displayed on a skin of a patient. In some examples, the estimated core body temperature may be displayed on a forehead of a patient. In some examples, the estimated core body temperature may be displayed on an area of a patient&#39;s skin corresponding to where the sensor  130  took measurements associated with the temperature of the patient. 
     In some examples, one or more characteristics of the display, for example, generated by the display module  140 , may vary depending on the estimated core body temperature. When the estimated core body temperature is above the normal range (for example, hyperthermia), the display of the estimated core body temperature may be in red. On the other hand, when the estimated core body temperature is below the normal range (for example, hypothermia), the display of the estimated core body temperature may be in blue. When the estimated core body temperature is within the normal range, the display of the estimated core body temperature may be in green. In some examples, different visible blinking or flashing patterns may be used for different estimated core body temperatures. The display of the estimated core body temperature may be steady and not blink when the estimated core body temperature is within the normal range. However, the display may blink when the estimated core body temperature is not within the normal range. In other examples, the display may blink at a variable rate depending on the difference between the measured estimated core body temperature and the normal range. Of course, other suitable colors and patterns not described above may be used to display the estimated core body temperature. 
     The frequency at which the display of the estimated core body temperature blink or flash may be between about 1 Hz and about 50 Hz, between about 2 Hz, and about 45 Hz, between about 5 Hz, and about 40 Hz, between about 10 Hz, and about 35 Hz, between about 15 Hz and about 30 Hz, between about 20 Hz and about 25 Hz, or about 1 Hz, 2 Hz, 5 Hz, 10 Hz, 15 Hz, 20 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz, 45 Hz, 50 Hz, or range between any two of aforementioned values. 
     In some examples, the color schemes (or blinking or flashing patterns) may be provided by the processor  120  of the temperature measurement system  110 . In other examples, such schemes or patterns may be provided by care providers. For example, care providers may be able to configure the temperature measurement system  110  or the display module  140  to change the color schemes or blinking (or flashing) patterns. Care providers may be able to remotely configure the temperature measurement system  110  or the display module  140  via the communication module  150 . For example, care providers may transmit signals that include color (or blinking) schemes or patterns to the temperature measurement system  110  via the communication module  150  using mobile devices including, but not limited to, tablets, mobile communication devices, personal computers, and the like. 
     Distance Indicators 
     As described herein, the sensor  130  can be an IR sensor. Typically, IR sensors have a recommended measuring range. For example, when the sensor  130  is too close or too far from a patient, the temperature measurement system  110  may not be able to accurately estimate core body temperature of the patient. Therefore it may be advantageous to provide systems or methods for indicating when the sensor  130  is located at an adequate or recommended distance from the patient. The recommended distance for the sensor  130  may be determined at the time of manufacture or changed by a user, for example, a care provider, at any time. 
       FIG. 7  illustrates an example method  700  for correctly positioning the temperature measurement system  110  with respect to the patient. The temperature measurement system  110  may include a distance indicator module that may determine the distance between the temperature measurement system  110  and an object, for example, a patient. For example, the distance indicator module may be an optical module  800  as illustrated in  FIG. 8A  and described herein. In some examples, the distance indicator module can be the display module  140 . At block  702 , the processor  120  actuates the distance indicator module. At block  704 , the temperature measurement system  110  is positioned with respect to the patient. At block  706 , a distance indicator is monitored. In some examples, the distance indicator is generated by the display module  140 . The distance indicator may be displayed on the temperature measurement system  110  or on the patient. The distance indicator may indicate whether the temperature measurement system  110  is positioned at a recommended distance from the patient. 
     In a non-limiting example, the distance indicator can include a first light beam in a first color and a second light beam in a second color. The first light beam and the second light beam may be generated by the same light source or different light sources. For example, the first color can be blue and the second color can be yellow. The first light source and the second light source can be oriented such that the first beam of light and the second beam of light can intersect at a predetermined distance. 
     At block  708 , the processor  120  may determine whether the distance indicator indicates that the temperature measurement system  110  is at the recommended distance from the patient. The process of determining whether the distance indicator indicates that the temperature measurement system  110  is at the recommended distance from the patient may include determining the distance between the temperature measurement system  110  and an object, for example, a patient, and comparing the determined distance with a threshold distance value. When the temperature measurement system  110  is too close to the patient (including, for example, the distance between the temperature measurement system  110  and the patient is less than the recommended distance), the first beam and the second beam may be projected onto the patient at two different locations. Likewise, when the temperature measurement system  110  is too far from the patient (including, for example, the distance between the temperature measurement system  110  and the patient is greater than the recommended distance), the first beam and the second beam may be projected onto the patient at two different locations. However, when the temperature measurement system  110  is at the recommended distance from the patient, the two beams may be projected on the patient at the same location, displaying a third color different from the first color and the second color. For example, the third color can be green, which is a mix of blue and yellow. In this regard, care providers will be able to easily reorient the temperature measurement system  110  by monitoring where the two beams are on the patient. 
     In another example, the distance indicator projected on the patient may be visible or legible when the temperature measurement system  110  is positioned at a predetermined distance from the patient. The distance indicator, in some examples, may not be visible or legible when the temperature measurement system  110  is not positioned at the predetermined distance from the patient (including, for example, too close or too far from the patient). The distance indicator may be a temperature reading of the patient. According to one example, the distance indicator may be blurry when the temperature measurement system  110  is not positioned at a predetermined distance from the patient  100  and not blurry (including, for example, clearly legible or visible) when the temperature measurement system  110  is positioned at the predetermined distance from the patient  100 . According to another example, the distance indicator may be out of focus when the temperature measurement system  110  is not positioned at a predetermined distance from a patient and in focus when the temperature measurement system  110  is positioned at the predetermined distance from the patient. 
     If the temperature measurement system  110  is not at the recommended distance, the temperature measurement system  110  can be re-positioned at block  710 . In some examples, the temperature measurement  110  may generate and display a message, for example, via the display module  140 , prompting a user to re-position the temperature measurement system  110 . After the temperature measurement system  110  is re-positioned, the distance indicator can be monitored again to determine whether the temperature measurement system  110  is positioned at the recommended distance from the patient. If the temperature measurement system  110  is at the recommended distance, the estimated core body temperature displayed by the temperature measurement system  110  can be recorded at block  712 . 
       FIG. 8A  is a block diagram illustrating an example temperature measurement system  110  including an optical module  800 . As noted above, the temperature measurement system  110 , in addition to the optical module  800 , can include the processor  120 , the sensor  130 , the display module  140 , and the communication module  150 . The processor  120  can communicate with the optical module  800  to calculate the distance between the temperature measurement system  110  and the patient  100 . 
       FIG. 8B  is a block diagram illustrating the optical module  800 . The optical module  800  can include an aperture  810 , a light source  820 , a light detecting module  830 , and a cover  840 . The aperture  810  can provide a path for infrared radiation to travel between the patient  100  and the temperature measurement system  110 . In some implementations, the aperture  810  can provide a path for the light to travel from the light source  820  to another location, for example, skin of the patient. The light source  820  and the sensor  130  can be housed within the aperture  810 . The aperture  810  can have a cross-sectional shape that is substantially parabolic. Such cross-sectional shape can aid in focusing an incoming light to the light detecting module  830 . An inner surface of the aperture  810  can be reflective. 
     The light source  820  and the light detecting module  830  can be used to calculate the distance between the temperature measurement system  110  and the patient  100 . The light emitted by the light source  820  can be reflected by the patient  100 . The light detecting module  830  can detect the light reflected by the patient  100 . The light detecting module  830  can detect one or more characteristics of the reflected light to determine the distance between the patient  100  and the temperature measurement module system  110 . In some implementations, the light source  820  is a light emitter that generates infrared light. 
     The light detecting module  830  can detect the intensity of the reflected light. The intensity of the reflected light can inversely correspond to the distance between the patient  100  and the temperature measurement system  110 . By determining the intensity of the reflected light (that is, reflected from the patient), the distance between the patient  100  and the temperature measurement system  110  can be calculated. 
     Additionally or alternatively, the light detecting module  830  can be a position-sensible photo detector that can determine light incident position of the reflected light. In some implementations, the conductivity of the light detecting module  830  can vary based on the incident position of the reflected light (for example, light reflected from or by the patient  100 ). In this regard, the conductivity of the light detecting module  830  can be used to calculate the distance between the patient  100  and the temperature measuring system  110 . 
     The cover  840  can be coupled to the aperture  810 . The cover  840  can be a closure mechanism for the aperture  810 . The cover  840  can be a flap, a lid, a sliding panel, and the like. The cover  840  can include an open configuration and a closed configuration. When in the open configuration, the cover  840  can allow light emitted by the light source  820  (or light emitter) to travel between the temperature measurement system  110  to the patient  100 . Moreover, the cover  840  in the open configuration can allow light to travel between the temperature measurement system  110  and the patient  100  such that the detecting module  830  can detect light reflected from the patient  100 . When in the closed configuration, the cover  840  can prevent light from travelling between the temperature measurement system  110  and the patient  100 . 
     In some examples, the cover  840  may be a lever arm that can be used to determine the distance between the temperature measurement system  110  and the patient. When actuated (for example, in an open configuration), the cover  840  can extend from the temperature measurement system  110  towards the patient. The length of the cover  840  may be substantially similar to the recommended distance between the sensor  130  and the patient as described herein. In some examples, the cover  840  may be extendable. When the cover  840  is not actuated (for example, in a closed configuration), it may cover the aperture  810 . 
     The cover  840  can be actuated by an actuator, which may be actuated by a button, a switch, or a control knob, for example, on the temperature measurement system  110 . Examples of actuators to open and close the cover  840  are mechanical actuators (such as a jack screw, spring, cam, wheel and axle, and the like), hydraulic actuators, magnetic actuators, piezoelectric actuators, twisted and coiled polymer (TCP) or supercoiled (SCP) actuators, thermal actuators, pneumatic actuators, and electro-mechanical actuators that can include a motor to actuate a mechanical actuator. 
     In some implementations, the cover  840  can be actuated automatically. For example, the actuator for the cover  840  can be actuated when the light source  820  is powered on (that is, generate a beam of light). In this regard, the cover  840  opens automatically when the user powers on the light source  820  to emit a beam of light towards the patient  100 . Optionally, the cover  840  can be actuated automatically when the sensor  130  is powered on to detect infrared radiation from the patient  100 . 
     The cover  840  can provide a waterproof or a water resistant barrier for the aperture  810 , which can be advantageous in wet environments. Such feature can be especially helpful in hospital settings. In some implementations, the cover  840  can be manually actuated or removed. The cover  840  can be modular or integrated to the temperature measurement system  110 . 
       FIG. 9  illustrates an example method  900  of generating and displaying an indicator that the temperature measurement system  110  is at a recommended distance from the patient  100 . At block  902 , the cover  840  is actuated. Actuating the cover  840  can change a configuration of the cover  840  from the closed configuration to the open configuration. When the cover  840  is in an open configuration, the light source  820  and the light detecting module  830  can be exposed such that light can travel between either of the light source  820  or the light detecting module  830  and the patient  100 . At block  904 , a beam of light can be emitted towards the patient  100  using the light source  820 . The beam of light, once it reaches the patient  100 , can be reflected by the patient  100  towards the temperature measurement system  110 . At block  906 , the reflected light can be detected using the light detecting module  830 . At block  908 , the detected reflected light is analyzed. As discussed herein, the detected reflected light can be analyzed to determine one or more characteristics. In some implementations, the light detector module  830  can determine an incident position of the reflected light. Optionally, the light detector module  830  can determine intensity of the reflected light. 
     At block  910 , a distance between the temperature measurement system  110  and the patient  100  is determined. The distance can be calculated using the incident position of the reflected light or the intensity of the reflected light. At block  912 , the distance between the temperature measurement system  110  and the patient  100  is compared to a predetermined range. The predetermined range can be indicative of recommended distance between the temperature measurement system  110  and the patient  100 . The predetermined range can be varied for different sensors, different conditions, or different applications. For example, the predetermined range can be different when estimating core body temperature at different areas of the patient  100 . In some implementations, the distance between the temperature measurement system  110  and the patient  100  is compared to a predetermined value (instead of a range). 
     At block  914 , when the distance between the temperature measurement system  110  and the patient  100  is within the predetermined range, the temperature measurement system  110  can generate, for example, using a display module  140 , a display indicating that the temperature measurement system  110  is at a recommended distance from the patient  100 . On the other hand, when the distance between the temperature measurement system  110  and the patient  100  is not within the predetermined range, the temperature measurement system  110 , at block  916 , can generate a display indicating that the temperature measurement system  110  is not at a recommended distance from the patient  100 . The method can return to the block  904  to emit another beam of light towards the patient  100 . 
     Terminology 
     Many other variations than those described herein will be apparent from this disclosure. For example, depending on the embodiment, certain acts, events, or functions of any of the algorithms described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the algorithms). Moreover, in certain examples, acts or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially. In addition, different tasks or processes can be performed by different machines or computing systems that can function together. 
     The various illustrative logical blocks, modules, and algorithm steps described in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The described functionality can be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosure. 
     The various illustrative logical blocks and modules described in connection with the embodiments disclosed herein can be implemented or performed by a machine, such as a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor can be a microprocessor, but in the alternative, the processor can be a controller, microcontroller, or state machine, combinations of the same, or the like. A processor can include electrical circuitry that can process computer-executable instructions. In another embodiment, a processor includes an FPGA or other programmable device that performs logic operations without processing computer-executable instructions. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. A computing environment can include any type of computer system, including, but not limited to, a computer system based on a microprocessor, a mainframe computer, a digital signal processor, a portable computing device, a device controller, or a computational engine within an appliance, to name a few. 
     The steps of a method, process, or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module stored in one or more memory devices and executed by one or more processors, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of non-transitory computer-readable storage medium, media, or physical computer storage known in the art. An example storage medium can be coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The storage medium can be volatile or nonvolatile. The processor and the storage medium can reside in an ASIC. 
     Conditional language used herein, such as, among others, “can,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list. Further, the term “each,” as used herein, in addition to having its ordinary meaning, can mean any subset of a set of elements to which the term “each” is applied. 
     While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the systems, devices or methods illustrated can be made without departing from the spirit of the disclosure. As will be recognized, certain embodiments described herein can be embodied within a form that does not provide all of the features and benefits set forth herein, as some features can be used or practiced separately from others. 
     The term “and/or” herein has its broadest, least limiting meaning which is the disclosure includes A alone, B alone, both A and B together, or A or B alternatively, but does not require both A and B or require one of A or one of B. As used herein, the phrase “at least one of” A, B, “and” C should be construed to mean a logical A or B or C, using a non-exclusive logical or. 
     The apparatuses and methods described herein may be implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on a non-transitory tangible computer readable medium. The computer programs may also include stored data. Non-limiting examples of the non-transitory tangible computer readable medium are nonvolatile memory, magnetic storage, and optical storage. 
     Although the foregoing disclosure has been described in terms of certain preferred embodiments, other embodiments will be apparent to those of ordinary skill in the art from the disclosure herein. Additionally, other combinations, omissions, substitutions and modifications will be apparent to the skilled artisan in view of the disclosure herein. Accordingly, the present invention is not intended to be limited by the description of the preferred embodiments, but is to be defined by reference to claims.