Non-contact temperature-based patient monitoring

Abstract

According to the present invention, there is provided a method for detecting at least one physiological signal of a patient, the method comprising the steps of: monitoring at least one subsection of the patient's surface with a thermal camera generating successive video frames having a plurality of pixels of the monitored subsection, the subsection of the patient's surface including at least a part of the patient's mouth and / or nose region as a region of interest; generating time-resolved temperature values ​​of at least one pixel of the region of interest; and generating a cardiac signal as the physiological signal based on the generated time-resolved temperature values. In this way, the possibility for non-contact temperature-based monitoring of a patient is provided in an easy and cost-effective manner.

Description

[Technical Field]

[0001] The present invention relates to the field of detecting respiratory and cardiac motion in a patient, and more particularly to detecting respiratory and cardiac motion during medical imaging or scan acquisition. [Background technology]

[0002] Detection of a patient's respiratory and cardiac motion has traditionally been performed using sensors applied to the patient. Physiological signals related to respiration and pulse can be provided by analyzing the patient's live video stream in either RGB or IR mode. Respiratory motion detection requires visibility of the motion of a target body part, such as the chest or upper abdomen. In typical medical imaging scenarios, coils, accessories, blankets, or support devices can obstruct the view from a specific fixed viewing angle, thus limiting the applicability of this technology. For non-occlusive remote cardiac physiological signal detection, video data can also be used to detect skin color changes due to pulsatile flow. The measurement principle is based on pulse plethysmography. Signal strength can be reduced in different ways, i.e., by skin visibility due to top or facial hair, or by physiological delays that vary from patient to patient or even for a single patient over time. In general, video-based pulse plethysmography works well with multispectral detectors, allowing the skin's absorption and reflection properties to self-calibrate for each video frame. A preferred setup for such a technique is based on a visible RGB camera using visible white light.

[0003] In "Combination of near infrared and thermal imaging techniques for remote and simultaneous measurements of breathing and heart rates under sleep situation" (PLoS ONE 13(1)2018), Hu M, Zhai G, Li D, Fan Y, Duan H, Zhu W et al. describe a near infrared imager and an infrared camera equipped with an IR-cutting lens and an infrared illumination array. Heart rate is detected by the infrared imaging system based on the absorption change in the skin due to blood flow to describe sleep quality.

[0004] US patent application US2014 / 275832 discloses an apparatus for acquiring vital sign information of a subject (a patient being examined). The known apparatus includes, for example, an infrared camera for acquiring an image data set of a skin portion of the patient. The vital sign information can then be derived from color changes of the skin portion. Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to provide a monitoring method and a monitoring system for detecting at least the movement of a patient's heart in an easy, versatile and reliable way, especially without the need for additional light irradiation. [Means for solving the problem]

[0006] According to the present invention, this object is addressed by the subject matter of the independent claims. Preferred embodiments of the invention are set forth in the dependent claims.

[0007] Therefore, according to the present invention, there is provided a method for detecting at least one physiological signal of a patient, the method comprising the steps of monitoring at least a subsection of the patient's surface with a thermal camera generating successive video frames having a plurality of pixels of the monitored subsection, the subsection of the patient's surface including at least a portion of the patient's mouth (including lips) and / or nose region as a region of interest; generating time-resolved temperature values ​​of at least one pixel of the region of interest; and generating a cardiac signal as the physiological signal based on the generated time-resolved temperature values.

[0008] When a cardiac signal is referred to, it is meant to refer to a signal generated from vibration waves following the contraction of the heart muscles in the chest. The heart rate indicated by the cardiac signal is the rate at which the heart beats, typically measured in beats per minute.

[0009] The method is adapted to generate a physiological signal based on temperature changes due to respiratory airflow, so that the region of interest includes the mouth and nose region, or just the mouth, or just the nose region.

[0010] This method involves generating a physiological signal based on temperature changes due to respiratory airflow. This is done using a region of interest that includes the mouth and nose area, or just the mouth, or just the nose area. Thermal cameras have a sensitivity range of wavelengths from 2 to 25 μm, i.e., outside the near-infrared and well beyond the optical wavelength range. The insight of this invention is that the nose and mouth contain mucous membranes that are more humid than normal skin. Airflow dramatically changes the temperature of this surface, resulting in a high SNR signal that represents both respiratory and cardiac activity. The respiratory signal is directly related to inhaled and exhaled airflow. When the patient inhales, the mucosal surface cools, causing a significant drop in temperature, which rises again with the exhalation of warm air from the inside, generating a time signal.

[0011] According to a further aspect of the present invention, the nose and mouth regions of the examined patient can be easily and automatically recognized, for example from thermal video frames. Automatic recognition of the nose / mouth region can be performed using simple commercially available facial recognition software, which can be based on deep learning, as is often installed today in mobile phones with integrated cameras.

[0012] The broader insight of the present invention is that acquiring long-wavelength infrared data from the nose and mouth region allows accurate information about the patient's cardiac and respiratory motion to be derived from the temperature changes represented in the long-wavelength infrared data. Additionally, workflow becomes more efficient because the nose and mouth region can be easily and accurately automatically identified or recognized from thermal or optical video frames.

[0013] According to a preferred embodiment of the present invention, the method further comprises the method step of generating a respiratory signal as an additional physiological signal based on the generated time-resolved temperature values.

[0014] When a respiration signal is referred to, it is meant to refer to a signal generated from the inhalation process of a patient's breathing. Respiration rate is the number of breaths a person takes per breath, e.g., per minute. While generating a respiration signal based on generated temperature values, a lower pixel temperature relative to a reference temperature indicates inhalation, and a higher pixel temperature relative to the reference temperature indicates exhalation.

[0015] According to a preferred embodiment of the present invention, the method further comprises a method step of triggering and / or gating scan acquisition based on at least one physiological signal, the scan acquisition being performed during a medical imaging examination and / or medical treatment using a medical imaging device. Respiratory and cardiac motions cause uncertainty during a medical imaging examination and / or medical treatment, since organs, or generally, ROIs, are moving during scan acquisition. Image data acquisition is triggered depending on respiratory and / or cardiac motion, thereby reducing uncertainty due to ROI movement during scan acquisition. The medical imaging device may be, for example, an MRI, CT, or PET, and the medical treatment may be, for example, radiation therapy.

[0016] The physiological signal is generated based on temperature variations due to respiratory airflow. To generate temperature variations due to respiratory airflow, the region of interest includes the mouth and nose region, or only the mouth, or only the nose region. According to a preferred embodiment of the present invention, at least one pixel is from a pixel covering the patient's nostril.

[0017] One advantage is that the method provides a method in which one single pixel is used in generating a time-resolved temperature value for at least one pixel in the region of interest. Therefore, it is not necessary to generate time-resolved values ​​for all pixels in the region of interest. The time-resolved temperature value of only one single pixel may be sufficient to generate a physiological signal.

[0018] Further, according to the present invention, there is provided a monitoring system for detecting at least one physiological signal of a patient. The monitoring system comprises a thermal camera adapted to monitor at least a subsection of the patient's surface. The thermal camera generates successive video frames having a plurality of pixels of the monitored subsection. The subsection of the patient's surface includes at least a portion of the patient's mouth and / or nose region as a region of interest. The monitoring system further comprises a signal processing unit adapted to generate time-resolved temperature values ​​of the at least one pixel of the region of interest and to generate a cardiac signal as the physiological signal based on the generated time-resolved temperature values.

[0019] According to a preferred embodiment of the present invention, the monitoring system comprises a patient support adapted to hold a patient such that the subsection of the patient's surface that can be monitored by the thermal camera includes at least a portion of the patient's mouth and / or nose area. The patient support can be designed as a patient table that can be movable in all three spatial directions to allow for highly accurate patient positioning. In addition, face and / or body tracking devices and algorithms can also be used to further confine the area of ​​interest. The camera itself can be such a device, and known computer vision algorithms can be applied to determine, for example, the face or head area.

[0020] According to a preferred embodiment of the present invention, the signal processing unit is adapted to generate a respiration signal as an additional physiological signal based on the generated time-resolved temperature values. To generate the time-resolved temperature values, a pulse frequency range is preferably defined. This range may be, for example, 40 to 300 beats per minute. To generate the second physiological signal, a respiration range is preferably defined. This range may be, for example, 10 to 20 respiratory cycles per minute. By defining the range, the contribution due to bandpass filtering can be isolated. According to another preferred embodiment, a spatial shift of the head due to respiration, which is greater than the pulse-induced movement, is used. This shift can be measured to obtain a clean respiration curve and isolate it in the thermal signal using its frequency.

[0021] Further, in accordance with the present invention, there is provided a non-transitory computer-readable medium having stored thereon instructions that, when executed on a processor, cause a monitoring system including a thermal camera to perform a method for detecting at least one physiological signal of a patient.

[0022] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter, but such embodiments do not necessarily represent the full scope of the invention, and reference is therefore made to the claims and this specification for interpreting the scope of the invention. [Brief explanation of the drawings]

[0023] [Figure 1] 1 shows a schematic diagram of a method according to a preferred embodiment of the present invention; [Figure 2] 2 shows a schematic representation of a second scenario of the method according to a preferred embodiment of the present invention. [Figure 3] 1 illustrates schematically a monitoring system according to a preferred embodiment of the present invention; [Figure 4] 1 illustrates a schematic representation of a thermal camera and ROI of a surveillance system according to a preferred embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0024] FIG. 1 shows a schematic diagram of a method according to a preferred embodiment of the present invention. The first step S1 is to monitor at least a subsection 2 of a patient's surface 4 using a thermal camera 5. The thermal camera 5 generates successive video frames having a plurality of pixels 6 of the monitored subsection 2. The subsection 2 of the patient's surface 4 includes at least a portion of the patient's mouth and / or nose region as a region of interest 3 to generate a physiological signal based on temperature changes due to respiratory airflow. The second step S2 is to generate these time-resolved temperature values ​​of at least one pixel 8 of the region of interest 3. The third step S3 is to generate a cardiac signal 9 as the physiological signal 1 based on the generated time-resolved temperature values. The generated cardiac signal 9 can be used for the fifth step S5 and / or the sixth step S6. The fifth step S5 is to trigger, and the sixth step S6 is to gate the scan acquisition based on at least one physiological signal 1.

[0025] The scan acquisition is performed during a medical imaging examination and / or medical treatment by the medical imaging device 11. Therefore, it is possible to reduce uncertainties due to cardiac motion during the medical imaging examination and / or medical treatment. Some regions are moving during the scan acquisition due to the beating heart. The image data acquisition is gated in response to the cardiac signal 9, so that the cardiac motion can be traced on the medical image. Another opportunity is to trigger the image data acquisition in response to the cardiac signal 9, so that the image data acquisition is triggered every time the heart is in the same position. In FIG. 1, the medical imaging device 11 is an MRI system, a CT, or a linear accelerator.

[0026] 2 shows a schematic diagram of a second scheme of the method according to a preferred embodiment of the present invention. After the second step S2, i.e., after generating time-resolved temperature values ​​for at least one pixel 8 of the region of interest 3, it is possible to generate not only a cardiac signal, as described in the third step S3 of FIG. 1, but also a respiratory signal 10 as an additional physiological signal 1 based on the generated time-resolved temperature values. The generation of the respiratory signal 10 is the fourth step S4. Image data acquisition can be triggered S5 and / or gated S6 based on the cardiac signal 9 and / or the respiratory signal 10.

[0027] FIG. 3 shows a schematic diagram of a monitoring system 14 according to a preferred embodiment of the present invention. The situation during image data acquisition is shown. A patient 7 lies on a patient table 16. The table is movable in all three dimensions so that a region of interest 3 can be precisely positioned. The region of interest 3 is part of a subsection 2 of the patient 7 and includes the patient's nostrils 13. A thermal camera 5 is attached to a medical imaging device 11. In FIG. 3, the medical imaging device 11 is an MRI. The thermal camera 5 scans the patient's surface 4, in particular the precisely positioned region of interest 3. The thermal camera 5 is adapted to generate time-resolved temperature values ​​that are processed by a signal processing unit 15. Based on the time-resolved temperature values, the signal processing unit 15 generates two physiological signals, namely, a cardiac signal 9 and a respiratory signal 10, which are visualized.

[0028] Figure 4 shows a schematic representation of a thermal camera 5 and a region of interest 3 of a monitoring system according to a preferred embodiment of the present invention. The thermal camera 5 scans the patient's surface 4 and generates successive video frames having a plurality of pixels 6 of the region of interest 3. For clarity, the patient's nostrils 13 are not shown in Figure 4, but they are part of the region of interest 3. Time-resolved temperature values ​​of at least one pixel 8 of the region of interest 3 are generated. In particular, according to the present invention, it is possible to generate time-resolved temperature values ​​of at least one pixel 8 of the region of interest 3 using only one single pixel 12.

[0029] While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered exemplary or illustrative and not restrictive, and the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of 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. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope. Moreover, for the sake of clarity, not all elements in the drawings have been labeled with reference signs. [Explanation of symbols]

[0030] Subsection Monitoring S1 Temperature value generation S2 Cardiac signal generation S3 Respiratory signal generation S4 Scan Acquisition Trigger S5 Scan acquisition gating S6 Physiological signals 1 measure 2 Area of ​​Interest 3 Patient Surface 4 Thermal Camera 5 Multiple pixels 6 patient 7 Pixels 8 Heart Signal 9 breathing signal 10 Medical Devices 11 Single pixel 12 nostrils 13 Surveillance Systems 14 Signal Processing Circuit 15 Patient Table 16

Claims

1. 1. A method for detecting at least one physiological signal of a patient, comprising: monitoring at least one subsection of a patient's surface with a thermal camera generating successive video frames having a plurality of pixels of the monitored subsection, the subsection of the patient's surface including at least a portion of the patient's mouth and / or nose area as an area of ​​interest; generating a time-resolved temperature value of at least one pixel of the region of interest; generating a cardiac signal as the physiological signal based on the generated time-resolved temperature values ​​due to temperature changes caused by respiratory airflow; A method comprising:

2. The method of claim 1 , wherein the camera detects the video frames in the wavelength range of 2 μm to 25 μm.

3. The method of claim 1 or 2, wherein the patient's nose and mouth are automatically detected as the region of interest from the video frames.

4. The method according to claim 1 , further comprising generating a respiratory signal as an additional physiological signal based on the generated time-resolved temperature values.

5. 5. The method according to claim 1, further comprising the step of triggering and / or gating scan acquisition based on the at least one physiological signal, the scan acquisition being performed during a medical imaging examination and / or medical treatment using a medical imaging device.

6. 6. The method of claim 1, wherein the at least one pixel is from the pixel covering a nostril of the patient.

7. 7. The method according to claim 1, wherein in the step of generating time-resolved temperature values ​​of at least one pixel of the region of interest, one single pixel is used.

8. 1. A monitoring system for detecting at least one physiological signal of a patient, the monitoring system comprising: a thermal camera adapted to monitor at least one subsection of a patient's surface generating successive video frames having a plurality of pixels of the monitored subsection, the subsection of the patient's surface including portions of the patient's mouth and / or nose region as regions of interest; a signal processing unit adapted to generate a time-resolved temperature value of at least one pixel in the region of interest, and to generate a cardiac signal as the physiological signal based on the generated time-resolved temperature value due to temperature changes caused by respiratory airflow; A monitoring system having:

9. 9. The surveillance system of claim 8, wherein the thermal camera is sensitive in the infrared wavelength range of 2 μm to 25 μm.

10. 10. The monitoring system of claim 8 or 9, wherein the signal processing unit comprises an auto-detection module for identifying the patient's nose and mouth regions from the video frames.

11. 10. The monitoring system of claim 8 or 9, wherein the signal processing unit is adapted to generate a respiratory signal as an additional physiological signal based on the generated time-resolved temperature values.

12. A computer readable medium storing instructions that, when executed on a processor, cause a surveillance system comprising a thermal camera to perform the method of any one of claims 1 to 7.

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