Device for detecting tissue inflammation

Abstract

A device (100) for detecting tissue inflammation is provided. The device (100) includes a processor (102) configured to acquire a plurality of photoplethysmographic (PPG) signals from at least one sensor (104), the plurality of photoplethysmographic (PPG) signals indicating light detected in a tissue region at a plurality of corresponding locations within the region. The processor is further configured to process the acquired plurality of PPG signals to determine an amplitude and a phase of each of the plurality of PPG signals, and based on the determined amplitude and phase of each of the plurality of PPG signals, detect tissue inflammation.

Description

Technical Field

[0001] The present disclosure relates to an apparatus and method for detecting tissue inflammation. Background Art

[0002] Tissue inflammation can provide useful insights into tissue appearance and health. Tissue inflammation is part of a complex biological response of body tissues to noxious stimuli such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molecular mediators.

[0003] An example of tissue inflammation is comedones. Comedones are small inflamed bumps on the skin. They are the result of excess oil being trapped in the pores of the skin, leading to inflammation and infection. Comedones occur at the site of the sebaceous ducts, which transport sebum from the sebaceous glands to the skin. Driven by hormonal changes at the onset of puberty, the sebaceous glands begin to produce more sebum. Since this oily substance is a rich food source for skin bacteria such as Propionibacterium acnes, these bacteria accumulate in large numbers in the sebaceous ducts. The consuming presence of the bacteria results in an altered sebum composition characterized by higher concentrations of lipid peroxides and free fatty acids. These slightly aggressive agents and Propionibacterium acnes itself trigger a pre-inflammatory process in the perifollicular area.

[0004] Generally, children do not develop acne before the age of 12. However, after the onset of puberty, more than 85% of teenagers will develop acne and frequent outbreaks, which generally continue until around the age of 25. In fact, even after this age, people may still develop acne. Acne is the clinical manifestation of acne, a skin condition that affects many people. Acne consists of papules and pustules, both of which are raised lesions after inflammation, and the difference is only that pustules contain visible amounts of pus while papules do not. It is useful to perform early comedonal testing to identify the onset of acne.

[0005] Indeed, early detection of tissue inflammation may be useful in general. Tissue inflammation is characterized by localized areas of increased (or enhanced) perfusion. Early acne begins with inflammation (which causes increased perfusion), even before the user notices the acne. Localized areas of enhanced perfusion may be detected by laser scattering techniques, such as laser Doppler perfusion imaging or laser speckle contrast analysis. WO2007 / 103795 discloses the use of spectral imaging techniques to compare an erythema map of the imaged skin with a visible light image of the imaged skin to identify any areas of predisposition to lesions.

[0006] However, existing technologies for detecting tissue inflammation are very expensive, have limited mobile robustness, and are difficult to commercialize using off-the-shelf components. In addition, in existing technologies, non-inflamed tissue may be misclassified as inflamed tissue in cases where the tissue is marked, such as including tattoos, makeup, spider veins, etc. Therefore, existing technologies lack accuracy in detecting inflamed tissue. Summary of the invention

[0007] As described above, a limitation of the prior art is that non-inflamed tissue may be misclassified as inflamed tissue, and therefore, the prior art is not accurate enough in detecting inflamed tissue. Therefore, it would be valuable to have improvements that can address this limitation.

[0008] Therefore, according to a first aspect, there is provided an apparatus for detecting tissue inflammation. The apparatus comprises a processor configured to acquire a plurality of photoplethysmographic (PPG) signals from at least one sensor, the plurality of photoplethysmographic (PPG) signals indicating light detected in a tissue region at a plurality of corresponding positions within the region. The processor is further configured to process the acquired plurality of PPG signals to determine an amplitude and a phase of each of the plurality of PPG signals, and based on the determined amplitude and phase of each of the plurality of PPG signals, detect tissue inflammation.

[0009] In some embodiments, the processor may be configured to detect tissue inflammation if the determined amplitude of at least one of the plurality of PPG signals is greater than a threshold amplitude. In some embodiments, the amplitude of each of the plurality of PPG signals may be an amplitude of the PPG signal normalized by a DC component of the PPG signal.

[0010] In some embodiments, the processor may be configured to detect tissue inflammation if a phase shift is detected in the determined phase of at least one of the plurality of PPG signals. In some embodiments, the processor may be configured to detect tissue inflammation if the detected phase shift is greater than a threshold phase shift. In some embodiments, the threshold phase shift may be a phase shift in the range of 45 to 135 degrees.

[0011] In some embodiments, the processor may be configured to generate an amplitude map representing the determined amplitude of each signal in the plurality of PPG signals. In some embodiments, the processor may be configured to generate an amplitude map representing the determined amplitude of each signal in the plurality of PPG signals, for each signal, the determined amplitude is greater than a threshold amplitude.

[0012] In some embodiments, the processor may be configured to generate a phase diagram representing the determined phase of each signal in the plurality of PPG signals. In some embodiments, the processor may be configured to generate a phase diagram representing the determined phase of each signal in the plurality of PPG signals, for each signal, a phase shift detected in the determined phase being greater than a threshold phase shift.

[0013] In some embodiments, the processor may be configured to compare the generated amplitude map and the generated phase map and determine a location of the detected tissue inflammation in the tissue region based on the comparison.

[0014] In some embodiments, the processor may be configured to generate a tissue inflammation map representing the determined locations of the detected tissue inflammation in the tissue region. In some embodiments, the processor may be configured to acquire an image of the tissue region and, based on the generated tissue inflammation map, indicate the determined locations of the detected tissue inflammation on the acquired image of the tissue region.

[0015] According to a second aspect, a method for detecting tissue inflammation is provided. The method includes acquiring a plurality of PPG signals indicating light detected in a tissue region at a plurality of corresponding positions within the region, and processing the acquired plurality of PPG signals to determine an amplitude and a phase of each of the plurality of PPG signals. The method also includes detecting tissue inflammation based on the determined amplitude and phase of each of the plurality of PPG signals.

[0016] According to a third aspect, a computer program product is provided, comprising a computer readable medium having computer readable code stored therein, wherein the computer readable code is configured to, when executed by a suitable computer or processor, cause the computer or processor to perform the method described above.

[0017] According to the above aspects and embodiments, limitations of the prior art are addressed. In particular, according to the above aspects and embodiments, both the amplitude and phase of each of the plurality of PPG signals are used for detection of tissue inflammation. This avoids misclassification of non-inflammatory tissue (such as where the tissue is marked, e.g., including tattoos, makeup, spider veins, etc.) as inflammatory tissue, and thus inflammatory tissue can be detected more accurately. Thus, an improved apparatus and method for detecting tissue inflammation is described.

[0018] These and other aspects will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Exemplary embodiments will now be described, by way of example only, with reference to the following drawings, in which:

[0020] Figure 1 is a schematic diagram of an apparatus according to one embodiment;

[0021] Figure 2 is a flow chart illustrating a method according to one embodiment;

[0022] Figure 3 is a block diagram illustrating a method according to one embodiment; and

[0023] Figure 4-9 They are the respective illustrations of the amplitude diagram and the phase diagram. DETAILED DESCRIPTION

[0024] As described above, an improved device and method for detecting tissue inflammation is provided herein. In some embodiments, the device described herein can be a dedicated device (or device) for tissue inflammation detection or a mobile device such as a smart phone or tablet (e.g., running an application or "app" for detecting tissue inflammation).

[0025] The tissues described herein may include any type of tissue. For example, the tissue may include epithelial tissue such as skin (e.g., epidermis of skin, cells of skin, hair follicles in skin, etc.) or the protective layer of a hollow organ (e.g., a protective layer of a gastrointestinal organ or any other hollow organ), muscle tissue (e.g., cardiac muscle tissue, skeletal muscle, or any other muscle tissue), connective tissue (e.g., fat, bone, tendon, or any other connective tissue), neural tissue (e.g., brain, spinal cord, nerves, or any other neural tissue), blood vessels, or any other tissue, or any combination of tissues.

[0026] Generally, tissue inflammation is (e.g., local) inflammation of a tissue. Tissue inflammation may be a biological response of a tissue to a harmful stimulus, such as a pathogen, damaged cells, irritants, etc. Tissue inflammation may cause the tissue to become red, swollen, and / or hot. Tissue inflammation has a variety of causes, and examples include, but are not limited to, pustules (or acne), papules, cysts, nodules, cuts, etc.

[0027] Figure 1 FIG. 1 is a diagram of an apparatus 100 for detecting tissue inflammation according to one embodiment. Figure 1As shown, the device 100 includes a processor 102. In short, the processor 102 is configured to acquire a plurality of photoplethysmographic PPG signals indicating light detected in a tissue region at a plurality of corresponding positions within a region. The tissue region described herein may also be referred to as a region of interest (ROI) of the tissue. The processor 102 is configured to acquire a plurality of PPG signals from at least one sensor 104. The processor 102 is also configured to process the acquired plurality of PPG signals to determine an amplitude and a phase of each of the plurality of PPG signals. The processor 102 is configured to detect tissue inflammation based on the determined amplitude and phase of each of the plurality of PPG signals.

[0028] The processor 102 may be implemented in a variety of ways using software and / or hardware to perform the various functions described herein. In a particular embodiment, the processor 102 may include multiple software and / or hardware modules, each of which is configured to perform or be used to perform a single or multiple steps of the method described herein. The processor 102 may include one or more processors (such as one or more microprocessors, one or more multi-core processors, and / or one or more digital signal processors (DSPs)), one or more processing units, and / or one or more controllers (such as one or more microcontrollers), which may be configured or programmed (e.g., using software or computer program code) to perform the various functions described herein. The processor 102 may be implemented as a combination of dedicated hardware (e.g., amplifiers, preamplifiers, analog-to-digital converters (ADCs), and / or digital-to-analog converters (DACs)) that perform some functions, and processors (e.g., one or more programmed microprocessors, DSPs, and associated circuits) that perform other functions.

[0029] like Figure 1 As shown, in some embodiments, the device 100 may include at least one sensor 104, and the processor 102 may be configured to obtain one or more of the multiple PPG signals from the at least one sensor 104. Alternatively or additionally, the at least one sensor 104 may be located outside the device 100 (e.g., separate from or far away from the device 100), and the processor 102 may be configured to obtain one or more of the multiple PPG signals from the at least one sensor 104. The at least one sensor 104 referred to herein is configured to obtain multiple PPG signals from a tissue area at multiple corresponding positions within the area. Therefore, the at least one sensor 104 may also be referred to as at least one PPG sensor. The at least one sensor 104 may be configured to obtain multiple PPG signals at a single (e.g., specific) light wavelength or multiple light wavelengths. The at least one sensor 104 may be a single sensor or multiple (e.g., a series of) sensors.

[0030] Examples of the at least one sensor 104 include, but are not limited to, a pulse oximeter (which may be configured to illuminate a tissue region and measure changes in light absorption within the tissue region to obtain multiple PPG signals), a camera (which may be configured to measure changes in tissue color to obtain multiple PPG signals), or any other sensor or sensor combination suitable for obtaining a PPG signal. Those skilled in the art will be aware of various sensors suitable for obtaining multiple PPG signals, and the manner in which these sensors may be configured to operate to obtain multiple PPG signals. In some embodiments, the at least one sensor 104 may be positioned at a distance from the tissue (e.g., away from the tissue). Therefore, according to some embodiments, the at least one sensor 104 may be a non-contact sensor. Therefore, the multiple PPG signals obtained in these embodiments may also be referred to as multiple non-contact PPG signals. Alternatively or additionally, in some embodiments, the at least one sensor 104 may be positioned so that it contacts the tissue to obtain multiple PPG signals.

[0031] like Figure 1 As shown, in some embodiments, the device 100 may include at least one memory 106. Alternatively or additionally, the at least one memory 106 may be located outside the device 100 (e.g., separate from or away from the device 100). For example, a hospital database may include at least one memory 106, and the at least one memory 106 may be a cloud computing resource, etc. The processor 102 of the device 100 may be configured to communicate with and / or connect to the at least one memory 106. The memory 106 may include any type of non-transitory machine-readable medium, such as a cache or system memory, including volatile and non-volatile computer memory, such as random access memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), and electrically erasable PROM (EEPROM). In some embodiments, the at least one memory 106 may be configured to store program code, which may be executed by the processor 102 of the device 100 to cause the device 100 to operate in the manner described herein.

[0032] Alternatively or additionally, in some embodiments, the at least one memory 106 may be configured to store information required for or generated by the methods described herein. For example, in some embodiments, the at least one memory 106 may be configured to store any one or more of: the acquired plurality of PPG signals, the determined amplitudes of one or more of the plurality of PPG signals, the determined phases of one or more of the plurality of PPG signals, the detected tissue inflammation, or any other information, or any combination of information required for or generated by the methods described herein. In some embodiments, the processor 102 of the device 100 may be configured to control the at least one memory 106 to store information required for or generated by the methods described herein.

[0033] like Figure 1 As shown, in some embodiments, the device 100 may include a user interface 108. Alternatively or additionally, the user interface 108 may be located outside the device 100 (e.g., separate from or away from the device 100). The processor 102 of the device 100 may be configured to communicate with and / or connect to the user interface 108. In some embodiments, the processor 102 of the device 100 may be configured to control the user interface 108 to operate in the manner described herein.

[0034] The user interface 108 may be configured to present (or output, display, or provide) information required by or generated by the methods described herein. For example, in some embodiments, the user interface 108 may be configured to present (or output, display, or provide) one or more of the following: a plurality of acquired PPG signals, a determined amplitude of one or more of the plurality of PPG signals, a determined phase of one or more of the plurality of PPG signals, detected tissue inflammation, or any other information, or any combination of information required by or generated by the methods described herein. Alternatively or additionally, the user interface 108 may be configured to receive user input. For example, the user interface 108 may allow a user to manually input information or instructions, interact with and / or control the device 100. Thus, the user interface 108 may be any user interface that enables the presentation (or output, display, or provision) of information and, alternatively or additionally, enables a user to provide user input.

[0035] For example, the user interface 108 may include one or more switches, one or more buttons, a keypad, a keyboard, a mouse, a touch screen or an application (e.g., on a smart device such as a tablet computer, a smart phone, or any other smart device), a display or display screen, a graphical user interface (GUI) such as a touch screen or any other visual component, one or more speakers, one or more microphones or any other audio component, one or more lights (such as light emitting diodes LED lights), a component for providing tactile or tactile feedback (such as a vibration function, or any other tactile feedback component), an augmented reality device (such as augmented reality glasses, or any other augmented reality device), a smart device (such as a smart mirror, a tablet computer, a smart phone, a smart watch, or any other smart device), or any other user interface, or a combination of user interfaces. In some embodiments, the user interface controlled to present information and the user interface that enables the user to provide user input may be the same user interface.

[0036] like Figure 1 As shown, in some embodiments, the device 100 may include a communication interface (or communication circuit) 110. Alternatively or additionally, the communication interface 110 may be located outside the device 100 (e.g., separate from or away from the device 100). The communication interface 110 may be used to enable the device 100 or a component of the device 100 to communicate with and / or connect to one or more other components (e.g., one or more sensors, interfaces, devices, processors, or memories), such as any of those described herein. For example, the communication interface 110 may be used to enable the processor 102 of the device 100 to communicate with and / or connect to one or more of the following: the previously mentioned at least one sensor 104, the previously mentioned at least one memory 106, and the previously mentioned user interface 108.

[0037] The communication interface 110 may enable the apparatus 100 or components of the apparatus 100 to communicate and / or connect in any suitable manner. For example, the communication interface 110 may enable the apparatus 100 or components of the apparatus 100 to communicate and / or connect wirelessly, via a wired connection, or via any other communication (or data transfer) mechanism. In some wireless embodiments, for example, the communication interface 110 may enable the apparatus 100 or components of the apparatus 100 to communicate and / or connect using radio frequency (RF), Bluetooth, or any other wireless communication technology.

[0038] Figure 2 A method 200 for detecting tissue inflammation according to one embodiment is illustrated. More specifically, Figure 2A method 200 of operating the previously described apparatus 100 for detecting tissue inflammation is illustrated. The method 200 is a computer-implemented method. As previously described, the apparatus 100 includes a processor 102. Figure 2 The illustrated method 200 may generally be performed by or under the control of the processor 102 of the apparatus 100 .

[0039] See also Figure 2 ,exist Figure 2 At block 202 of the apparatus 100 , a plurality of PPG signals are acquired, the plurality of PPG signals indicating light detected in a tissue region at a plurality of corresponding locations within the region. More specifically, the processor 102 of the apparatus 100 acquires a plurality of PPG signals from at least one sensor 104 .

[0040] The light detected in the tissue region can indicate the color in the tissue region, for example, the change of the light detected in the tissue region can indicate the color change in the tissue region. The color change in the tissue region is caused by the pulse pressure. Therefore, the multiple PPG signals can also be referred to as multiple pulse signals. In general, each PPG signal includes a direct current (DC) component and an alternating current (AC) component. The DC component of each PPG signal can be attributed to the body absorption of the tissue in the corresponding position in the tissue region. The AC component of each PPG signal can be attributed to the blood volume change caused by the pulse pressure in the corresponding position in the tissue region.

[0041] return Figure 2 At block 204, the acquired plurality of PPG signals are processed to determine an amplitude and a phase of each of the plurality of PPG signals. More specifically, the processor 102 of the apparatus 100 processes the acquired plurality of PPG signals to determine an amplitude and a phase of each of the plurality of PPG signals. Since the plurality of PPG signals indicate light detected in the tissue region at a plurality of corresponding positions within the region, the amplitude and the phase of each of the plurality of PPG signals are effectively determined at the plurality of corresponding positions within the region.

[0042] exist Figure 2 At block 206 of the apparatus 100, tissue inflammation is detected based on the determined amplitude and phase of each of the plurality of PPG signals. More specifically, the processor 102 of the apparatus 100 detects tissue inflammation based on the determined amplitude and phase of each of the plurality of PPG signals. Thus, detection of tissue inflammation is performed by combining amplitude and phase information.

[0043] In some embodiments, the processor 102 may be configured to detect tissue inflammation when the determined amplitude of at least one of the plurality of PPG signals is greater than a threshold amplitude. The threshold amplitude may be set differently depending on the subject and / or condition. Thus, in some embodiments, the threshold amplitude may be determined by calibration, wherein testing is performed on various subjects and / or under various conditions in order to determine an optimal threshold amplitude.

[0044] In some embodiments, the amplitude of each of the plurality of PPG signals may be a normalized amplitude. For example, the amplitude of each of the plurality of PPG signals may be the amplitude of the (original) PPG signal normalized by the direct current (DC) component of the PPG signal. In some such embodiments, the threshold amplitude may be an amplitude in the range of 0.2 to 2, such as an amplitude in the range of 0.3 to 1.9, such as an amplitude in the range of 0.4 to 1.8, such as an amplitude in the range of 0.5 to 1.7, such as an amplitude in the range of 0.6 to 1.6, such as an amplitude in the range of 0.7 to 1.5, such as an amplitude in the range of 0.8 to 1.4, such as an amplitude in the range of 0.9 to 1.3, such as an amplitude in the range of 1.0 to 1.2. In some embodiments, the threshold amplitude may be an amplitude in the range of 0.8 to 2, such as an amplitude in the range of 0.9 to 1.9, such as an amplitude in the range of 1 to 1.8, such as an amplitude in the range of 1.1 to 1.7, such as an amplitude in the range of 1.2 to 1.6, such as an amplitude in the range of 1.3 to 1.5. In some embodiments, the threshold amplitude may be an amplitude in the range of 1.3 to 2, such as an amplitude in the range of 1.35 to 1.95, such as an amplitude in the range of 1.4 to 1.9, such as an amplitude in the range of 1.45 to 1.85, such as an amplitude in the range of 1.5 to 1.8, such as an amplitude in the range of 1.55 to 1.75, such as an amplitude in the range of 1.6 to 1.7. In some embodiments, the threshold amplitude may be an amplitude in the range of 1.5 to 2, such as an amplitude in the range of 1.55 to 1.95, such as an amplitude in the range of 1.6 to 1.9, such as an amplitude in the range of 1.65 to 1.85, such as an amplitude in the range of 1.7 to 1.8.

[0045] In other embodiments, the processor 102 may be configured to generate an amplitude map histogram representing the determined amplitude of each of the plurality of PPG signals, and the threshold amplitude may be an amplitude within a range of 40% to 100% of the amplitude map histogram.

[0046] Alternatively or additionally, in some embodiments, the processor 102 may be configured to detect tissue inflammation if a phase shift is detected in the determined phase of at least one of the plurality of PPG signals. Thus, the processor 102 may be configured to detect tissue inflammation if the determined amplitude of at least one of the plurality of PPG signals is greater than a threshold amplitude, or the processor 102 may be configured to detect tissue inflammation if a phase shift is detected in the determined phase of at least one of the plurality of PPG signals, or the processor 102 may be configured to detect tissue inflammation if the determined amplitude of at least one of the plurality of PPG signals is greater than a threshold amplitude and a phase shift is detected in the determined phase of at least one of the plurality of PPG signals. In some embodiments, the latter detection may be implemented using logic gates (e.g., AND logic gates) or more complex algorithms (e.g., optimal weighting factors may be learned from a data set collected on tissue inflammation detection).

[0047] In some embodiments where a phase shift is detected, the processor 102 can be configured to detect tissue inflammation if the detected phase shift is greater than a threshold phase shift. In some embodiments, the threshold phase shift can be a phase shift in the range of 45 to 135 degrees, such as a phase shift in the range of 50 to 130 degrees, such as a phase shift in the range of 55 to 125 degrees, such as a phase shift in the range of 60 to 120 degrees, such as a phase shift in the range of 65 to 115 degrees, such as a phase shift in the range of 70 to 110 degrees, such as a phase shift in the range of 75 to 105 degrees, such as a phase shift in the range of 80 to 100 degrees, such as a phase shift in the range of 85 to 95 degrees. In some embodiments, the threshold phase offset can be a phase offset in the range of 50 to 100 degrees, for example, a phase offset in the range of 52 to 98 degrees, for example, a phase offset in the range of 54 to 96 degrees, for example, a phase offset in the range of 56 to 94 degrees, for example, a phase offset in the range of 58 to 92 degrees, for example, a phase offset in the range of 60 to 90 degrees, for example, a phase offset in the range of 62 to 88 degrees, for example, a phase offset in the range of 64 to 86 degrees, for example, a phase offset in the range of 66 to 84 degrees, for example, a phase offset in the range of 68 to 82 degrees, for example, a phase offset in the range of 70 to 80 degrees, for example, a phase offset in the range of 72 to 78 degrees, for example, a phase offset in the range of 74 to 76 degrees. In some embodiments, the threshold phase offset can be a phase offset in the range of 55 to 90 degrees, such as a phase offset in the range of 57 to 88 degrees, such as a phase offset in the range of 59 to 86 degrees, such as a phase offset in the range of 61 to 84 degrees, such as a phase offset in the range of 63 to 82 degrees, such as a phase offset in the range of 65 to 80 degrees, such as a phase offset in the range of 67 to 78 degrees, such as a phase offset in the range of 69 to 76 degrees, such as a phase offset in the range of 71 to 74 degrees.

[0048] In some embodiments, the processor 102 may be configured to detect tissue inflammation when the determined amplitude of at least one of the plurality of PPG signals is greater than a threshold amplitude and the detected phase shift is greater than a threshold phase shift. In some embodiments, such detection may be implemented using logic gates (e.g., “AND” logic gates) or more complex algorithms (e.g., optimal weighting factors may be learned from a data set collected on tissue inflammation detection).

[0049] Figure 3 An example method for determining the amplitude and phase offset of each of a plurality of PPG signals is illustrated. The example method utilizes phase lock amplification. Because the plurality of PPG signals indicate light detected in a tissue region at a plurality of corresponding locations within the region, the plurality of PPG signals may also be referred to as a plurality of “local” PPG signals. Figure 3As shown, the input of this method is the reference signal R(t) and the local PPG signal S(t). The reference signal R(t) can be expressed as:

[0050] R(t)=cos(w HR t)

[0051] where w HR is the heart rate frequency, and t is the time. The reference signal R(t) can be expressed as HR modulated and obtained by averaging all local PPG signals.

[0052] The local PPG signal S(t) can be expressed as:

[0053]

[0054] Where A is the modulated heart rate frequency w HR The amplitude, is the phase offset of the local PPG signal S(t) relative to the reference signal R(t), Sn(t) contains all other frequency components, and t is time. R(t) and S(t) are fed into the phase-locked amplifier block, and S(t) is multiplied by R(t), that is, by cos(w HR t), and the phase of R(t) is shifted by 90 degrees, that is, the phase is shifted to sin(w HR t). The two output signals of these operations are then low pass filtered. For example, the low pass filtering may be performed by averaging the two output signals over time, but it will be appreciated that any other form of low pass filtering may be used instead.

[0055] As a result of low-pass filtering, the two values ​​x and y are given as These values ​​are related to the amplitude A of the local PPG signal and the phase offset of the local PPG signal relative to R(t) By combining the values ​​x and y, the amplitude A of the local PPG signal and the phase offset of the local PPG signal Can be expressed as: and Thus, for each of the plurality of PPG signals, a value representing the amplitude of the PPG signal and a value representing the phase shift of the PPG signal may be determined.

[0056] although Figure 2, but in some embodiments where the amplitude of each of the plurality of PPG signals is determined, the processor 102 may be configured to generate an amplitude map representing the determined amplitude of each of the plurality of PPG signals. Alternatively or additionally, in some embodiments where the amplitude of each of the plurality of PPG signals is determined, the processor 102 may be configured to generate an amplitude map representing the determined amplitude of each of the plurality of PPG signals, for each signal, the determined amplitude being greater than a threshold amplitude. In this way, in the generated amplitude map, tissue inflammation may be distinguished from background noise. Since the plurality of PPG signals indicate light detected in a tissue region at a plurality of corresponding positions within the region, the amplitude map representing the determined amplitude of each of the plurality of PPG signals is a spatial map. The amplitude map may provide an indication of the degree of perfusion of the tissue spatially. In some embodiments, the amplitude map may be generated by associating a color with the determined amplitude of the PPG signal for each of the plurality of PPG signals and associating the color with a corresponding position within the tissue region. A person skilled in the art will be aware of various techniques that may be used to generate an amplitude map.

[0057] Alternatively or additionally, although Figure 2 102. Although not shown in the figure, in some embodiments where the phase of each of the plurality of PPG signals is determined, the processor 102 may be configured to generate a phase map representing the determined phase of each of the plurality of PPG signals. Alternatively or additionally, in some embodiments where the phase of each of the plurality of PPG signals is determined, the processor 102 may be configured to generate a phase map representing the determined phase of each of the plurality of PPG signals, for each signal, a phase shift detected in the determined phase is greater than a threshold phase shift. In this way, in the generated phase map, tissue inflammation may be distinguished from background noise. Since the plurality of PPG signals indicate light detected in the tissue region at a plurality of corresponding locations within the region, the phase map representing the determined phase of each of the plurality of PPG signals is a spatial map. The phase map may provide an indication of the phase shift of the local PPG signal. In some embodiments, the phase map may be generated by correlating a color with the determined phase of the PPG signal and associating the color with a corresponding location within the tissue region for each of the plurality of PPG signals. A person skilled in the art will be aware of various techniques that may be used to generate a phase map.

[0058] Figure 4 and Figure 5 is a diagram of an amplitude diagram and a phase diagram according to one embodiment. In more detail, Figure 4 (a) and Figure 5 (a) Images of tissue regions are shown, Figure 4 (b) and Figure 5(b) illustrating the generated amplitude graph representing the determined amplitude of each of the plurality of PPG signals, respectively, and Figure 4 (c) and Figure 5 (c) illustrates the generated phase diagram representing the determined phase of each of the plurality of PPG signals, respectively. As previously described, the plurality of PPG signals indicate light detected in the tissue region at a plurality of corresponding locations within the region. Tissue inflammation 300, 400 within the tissue region is Figure 4 (a), (b) and (c) and Figure 5 (a), (b) and (c) are circled. In the example shown, the tissue inflammation 300, 400 is acne and the tissue is skin. Figure 4 (d) and 5(d) illustrate the generated amplitude maps, overlaid on the image of the tissue region, and Figure 4 (e) and 5(e) illustrate the generated phase maps, respectively, overlaid on the image of the tissue region.

[0059] like Figure 4 and 5 As shown in FIG. 1 , both the generated amplitude map and the generated phase map are affected by the acne 300, 400. For example, Figure 4 As shown in (a), comedones (central areas with pus) are visible in circular areas of the image of the tissue region. Figure 4 As shown in the amplitude graph of (b), there is an increase in perfusion amplitude in the acne area. Figure 4 As shown in the phase image of (c), there is a phase shift in the comedone area. In addition, there is an increase in the perfusion amplitude in the tissue surrounding the pus area compared to the pus area itself (because the pus is not perfused by blood). On the other hand, Figure 5 An example of detecting acne at an early stage is shown. In this case, although Figure 5 In the circular area of ​​the tissue area image of (a), almost no comedones can be seen, but Figure 5 (b) The circular area 400 and Figure 5 In the circular region 400 of the phase image of (c), local enhanced perfusion is clearly visible. Figure 4 and 5 As shown, an increase in the amplitude of the PPG signal and a phase shift in the PPG signal can provide a good indication of tissue inflammation (e.g., acne), even in the early stages.

[0060] In some embodiments where the processor 102 is configured to generate both an amplitude map and a phase map, the processor 102 may also be configured to compare the generated amplitude map and the generated phase map. In some such embodiments, the processor 102 may be configured to determine the location of the detected tissue inflammation in the tissue region based on the comparison. For example, in some embodiments, if the amplitude at a location in the generated amplitude map is greater than a threshold amplitude and the phase offset at the corresponding location in the generated phase map is greater than a threshold phase offset, then tissue inflammation may be detected at the location. In some embodiments, this may be implemented using logic gates (e.g., AND logic gates) or more complex algorithms (e.g., optimal weighting factors may be learned from a data set collected regarding tissue inflammation detection). In some such embodiments, the processor 102 may also be configured to generate a tissue inflammation map representing the determined location of the detected tissue inflammation in the tissue region.

[0061] In some embodiments, the processor 102 may be configured to acquire an image (e.g., an RGB image) of a tissue region, and indicate the determined location of the detected tissue inflammation on the acquired image of the tissue region based on the generated tissue inflammation map. For example, in some embodiments, the processor 102 may be configured to indicate the determined location of the detected tissue inflammation on the acquired image of the tissue region by being configured to overlay the acquired image of the tissue region with the generated tissue inflammation map.

[0062] Figure 6 is an illustration of an amplitude map and a phase map according to one embodiment, wherein the amplitude map and the phase map are compared (e.g., in the manner previously described) and the location of tissue inflammation detected in the tissue region is determined. In more detail, Figure 6 (a) illustrates a generated amplitude map representing the determined amplitude of each of a plurality of PPG signals, and Figure 6 (b) illustrates a generated phase map representing the determined phase of each of the plurality of PPG signals.As previously described, the plurality of PPG signals indicate light detected in a tissue region at a plurality of corresponding locations within the region.

[0063] exist Figure 6 At arrow 500, the threshold amplitude previously described is applied to Figure 6 (a) The generated amplitude map. Thus, in the generated amplitude map, tissue inflammation can be distinguished from background noise. Therefore, Figure 6 (c) illustrates a generated amplitude map representing the determined amplitude of each signal in a plurality of PPG signals, for each signal, the determined amplitude is greater than the threshold amplitude. Figure 6 At arrow 502, the threshold phase offset described previously is applied to Figure 6 (b) The generated phase image. Thus, in the generated phase image, tissue inflammation can be distinguished from background noise. Figure 6 (d) illustrates a generated phase diagram representing the determined phase for each of a plurality of PPG signals, for each signal a phase shift in the determined phase being greater than a threshold phase shift.

[0064] exist Figure 6 At block 504 of Figure 6 The generated amplitude map shown in (c) is similar to Figure 6 (d), determine the location of the detected tissue inflammation in the tissue region based on the comparison, and generate a tissue inflammation map representing the determined location of the detected tissue inflammation in the tissue region. As previously described, in some embodiments, if Figure 6 The amplitude at a certain position in the generated amplitude map in (c) is greater than the threshold amplitude and Figure 6 If the phase shift at the corresponding position in the generated phase map in (d) is greater than the threshold phase shift, tissue inflammation can be detected at that position (which is then represented at the corresponding position in the tissue inflammation map). In some embodiments, this can be done using Figure 6 The weighting factor can be realized by a logic gate (e.g., an “AND” logic gate) as shown in the shape of the box 504 in FIG. 5 or a more complex algorithm (e.g., the optimal weighting factor can be learned from the data set collected on tissue inflammation detection). Figure 6 The generated amplitude map and Figure 6 The generated phase maps shown in (d) are combined.

[0065] Figure 6 (e) Illustration of the generated tissue inflammation map. Figure 6 As can be seen in (e), tissue inflammation is clearly visible in the generated tissue inflammation map, but background noise is not visible. In this way, tissue inflammation can be detected more accurately. Figure 6 (f) illustrates the generated tissue inflammation map overlaid (or superimposed) on the acquired image of the tissue region. It can thus be seen that tissue inflammation (eg, acne) is detected.

[0066] Figure 7 (a) illustrates the generated tissue inflammation map, where any pixel value for which the amplitude of at least one signal among the multiple PPG signals is greater than a threshold amplitude of 1.5 and a phase shift in the range of 45 to 135 degrees is detected anywhere in the phase of at least one signal among the multiple PPG signals is set to black, and all other pixel values ​​are set to white. Figure 7(b) illustrates the generated tissue inflammation map, where any pixel value where the amplitude of at least one of the multiple PPG signals is greater than the threshold amplitude of 0.2 and the phase shift at any position in the phase of at least one of the multiple PPG signals is detected within the range of 0 to 45 degrees is set to black, and all other pixel values ​​are set to white. Figure 7 In the inflammation image (b), no tissue inflammation is seen, but Figure 7 In (a), tissue inflammation is clearly visible.

[0067] Figure 8 is a diagram of an amplitude diagram and a phase diagram according to one embodiment. In more detail, Figure 8 (a) An image of a tissue region is shown. In this example, the tissue is the skin on the subject's forehead. Four dots of color are drawn on the forehead with ink. Figure 8 (b) illustrates a generated amplitude map representing the determined amplitude of each of the plurality of PPG signals, and Figure 8 (c) shows the generated phase map, which represents the determined phase of each of the plurality of PPG signals. The plurality of PPG signals indicate light detected in the forehead skin region of the subject at a plurality of corresponding positions in the region. The processor 102 of the apparatus 100 considers the black dot as background, which obscures the skin, and therefore, in Figure 8 In the amplitude plot of (b), no light (and thus no perfusion) is detected at the locations of the black dots. Figure 8 In the phase image of (c), the phase of the black dot area is also the same as the background. The processor 102 of the device 100 detects that the perfusion on the dot area is low (because the ink covers the skin). Figure 8 The phase map of (c) shows no change in perfusion over the dot area. Perfusion changes are detected at the boundaries of these dots, but this is only because of the sudden color change between the skin and the ink. By examining both the amplitude and phase shifts of the PPG signal, any non-inflammatory tissue (such as tattoos, makeup, spider veins, or other non-inflammatory tissue) will not be misclassified as inflammatory tissue (such as acne or other inflammatory tissue).

[0068] Fig. 9 is an illustration of an amplitude map and a phase map according to one embodiment, wherein the amplitude map and the phase map are compared (e.g., in the manner previously described) and the location of tissue inflammation detected in a tissue region is determined. In this example, the tissue region is a skin region on the forehead of a subject with four colored dots drawn in ink, such as Figure 8 In more detail, Fig. 9 (a) illustrates a generated amplitude map representing the determined amplitude of each of a plurality of PPG signals, and Fig. 9(b) illustrates a generated phase map representing the determined phase of each of a plurality of PPG signals indicating light detected in a forehead skin region at a plurality of corresponding locations in the region.

[0069] exist Fig. 9 At arrow 700, the threshold amplitude previously described is applied to Fig. 9 (a) The generated amplitude map. Thus, in the generated amplitude map, tissue inflammation can be distinguished from background noise. Therefore, Fig. 9 (c) illustrates a generated amplitude map representing the determined amplitude of each signal in a plurality of PPG signals, for each signal, the determined amplitude is greater than the threshold amplitude. Fig. 9 At arrow 702, the threshold phase offset described previously is applied to Fig. 9 (b) The generated phase image. Thus, in the generated phase image, tissue inflammation can be distinguished from background noise. Fig. 9 (d) illustrates a generated phase diagram representing the determined phase for each of a plurality of PPG signals, for each signal a detected phase shift in the determined phase being greater than a threshold phase shift.

[0070] exist Fig. 9 At block 704 of Fig. 9 The generated amplitude map shown in (c) is similar to Fig. 9 (d) and the generated phase map shown in FIG. 1 , determining the location of the detected tissue inflammation in the skin area on the forehead based on the comparison, and generating a tissue inflammation map representing the determined location of the detected tissue inflammation in the skin area on the forehead. As previously described, in some embodiments, if Fig. 9 The amplitude at a certain position in the generated amplitude map in (c) is greater than the threshold amplitude and Fig. 9 If the phase shift at the corresponding position in the generated phase map in (d) is greater than the threshold phase shift, tissue inflammation can be detected at that position (which is then represented at the corresponding position in the tissue inflammation map). In some embodiments, this can be done using Fig. 9 The weighting factor can be realized by a logic gate (e.g., an “AND” logic gate) as shown in the shape of the box 704 in FIG. 1 or a more complex algorithm (e.g., the optimal weighting factor can be learned from the data set collected on tissue inflammation detection). Fig. 9 The generated amplitude map and Fig. 9 The generated phase maps shown in (d) are combined. Fig. 9 (e) Illustration of the generated tissue inflammation map. Fig. 9As can be seen in (e), tissue inflammation 706 (in this example, a potential comedone in the early stage) is clearly visible in the generated tissue inflammation map, but background noise (including color dots) is not visible. Fig. 9 As shown, tissue inflammation can be detected more accurately.

[0071] A computer program product including a computer-readable medium is also described. The computer-readable medium has a computer-readable code contained therein. The computer-readable code is configured to, when executed by a suitable computer or processor, cause the computer or processor to perform the method described herein. The computer-readable medium can be, for example, any entity or device capable of carrying a computer program product. For example, a computer-readable medium can include a data storage device, such as a ROM (such as a CD-ROM or a semiconductor ROM) or a magnetic recording medium (such as a hard disk). In addition, the computer-readable medium can be a transportable carrier, such as an electrical signal or an optical signal, which can be transmitted via a cable or an optical cable or by radio or other means. When the computer program product is included in such a signal, the computer-readable medium can be composed of such cables or other devices or means. Alternatively, the computer-readable medium can be an integrated circuit embedded with a computer program product, which is suitable for executing or for executing the method described herein.

[0072] Thus, described herein are apparatus 100, methods 200, and computer program products that address limitations associated with the prior art. Thus, an improved apparatus and method for detecting tissue inflammation is described. Detecting tissue inflammation in the manner described herein enables better detection of infection, wound healing, skin irritation, and other conditions involving tissue inflammation.

[0073] In the process of practicing the principles and techniques described herein, variations of the disclosed embodiments are understandable and implementable to those skilled in the art by studying the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may satisfy multiple functions described in the claims. The fact that certain measures are recorded in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously. The computer program may be stored or distributed on an appropriate medium, such as an optical storage medium or solid-state medium provided with the hardware or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any figure marks in the claims should not be understood as limiting their scope.

Claims

1. A device (100) for detecting tissue inflammation, the device (100) comprising a processor (102), the processor being configured to: acquiring a plurality of photoplethysmographic (PPG) signals from at least one sensor (104), the plurality of photoplethysmographic (PPG) signals indicating light detected in a tissue region at a plurality of corresponding locations within the region; processing the acquired plurality of PPG signals to determine an amplitude and a phase of each of the plurality of PPG signals; as well as detecting tissue inflammation if the determined amplitude of at least one of the plurality of PPG signals is greater than a threshold amplitude and a phase shift greater than a threshold phase shift is detected in the determined phase of at least one of the plurality of PPG signals; wherein the threshold amplitude is an amplitude in the range of 0.2 to 2; The threshold phase shift is a phase shift in the range of 45 to 135 degrees.

2. The apparatus (100) according to claim 1, wherein the amplitude of each of the plurality of PPG signals is the amplitude of the PPG signal normalized by a DC component of the PPG signal.

3. The apparatus (100) of claim 2, wherein the threshold amplitude is: a magnitude in the range of 0.8 to 2; or a magnitude in the range of 1.3 to 2; or Amplitude in the range of 1.5 to 2.

4. The apparatus (100) according to any one of claims 1 to 3, wherein the threshold phase offset is: A phase shift in the range of 50 to 100 degrees; or Phase shift in the range of 55 to 90 degrees.

5. The apparatus (100) according to any one of claims 1 to 3, wherein the processor (102) is configured to: An amplitude map representing the determined amplitude of each signal in the plurality of PPG signals is generated.

6. The apparatus (100) according to any one of claims 1 to 3, wherein the processor (102) is configured to: An amplitude map is generated that represents the determined amplitude of each signal of the plurality of PPG signals, for each signal the determined amplitude is greater than a threshold amplitude.

7. The apparatus (100) according to any one of claims 1 to 3, wherein the processor (102) is configured to: A phase map is generated that represents the determined phase of each signal in the plurality of PPG signals.

8. The apparatus (100) according to any one of claims 1 to 3, wherein the processor (102) is configured to: A phase map is generated representing the determined phase for each of the plurality of PPG signals for which a detected phase shift is greater than a threshold phase shift.

9. The apparatus (100) of claim 5, wherein the processor (102) is configured to: generating a phase map representing the determined phase of each signal in the plurality of PPG signals; comparing the generated magnitude map and the generated phase map; as well as The location of the detected tissue inflammation (300, 400) in the tissue region is determined based on the comparison.

10. The apparatus (100) of claim 6, wherein the processor (102) is configured to: generating a phase map representing the determined phase of each signal of the plurality of PPG signals, for each signal a detected phase shift in the determined phase being greater than a threshold phase shift; comparing the generated magnitude map and the generated phase map; as well as The location of the detected tissue inflammation (300, 400) in the tissue region is determined based on the comparison.

11. The apparatus (100) according to claim 9 or 10, wherein the processor (102) is configured to: A tissue inflammation map is generated that represents the determined locations of the detected tissue inflammation (300, 400) in the tissue region.

12. The apparatus (100) of claim 11, wherein the processor (102) is configured to: acquiring an image of the tissue region; and According to the generated tissue inflammation map, the determined location of the detected tissue inflammation (300, 400) is indicated on the acquired image of the tissue region.

13. A computer program product comprising a computer readable medium having computer readable code stored therein, the computer readable code being configured to, when executed by a suitable computer or processor, cause the computer or processor to perform a method (200) for detecting tissue inflammation, the method (200) comprising: acquiring (202) a plurality of PPG signals indicative of light detected in a tissue region at a plurality of corresponding locations within the region; processing (204) the acquired plurality of PPG signals to determine an amplitude and a phase of each of the plurality of PPG signals; as well as Tissue inflammation (300, 400) is detected (206) when the determined amplitude of at least one of the plurality of PPG signals is greater than a threshold amplitude and a phase shift greater than a threshold phase shift is detected in the determined phase of at least one of the plurality of PPG signals.

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