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WO2017129454A1 - Patient head-mountable device having a vital sign camera for use in a medical scanning modality - Google Patents

Patient head-mountable device having a vital sign camera for use in a medical scanning modality Download PDF

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Publication number
WO2017129454A1
WO2017129454A1 PCT/EP2017/050920 EP2017050920W WO2017129454A1 WO 2017129454 A1 WO2017129454 A1 WO 2017129454A1 EP 2017050920 W EP2017050920 W EP 2017050920W WO 2017129454 A1 WO2017129454 A1 WO 2017129454A1
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WO
WIPO (PCT)
Prior art keywords
type
patient
physiological parameter
output signals
scanning
Prior art date
Application number
PCT/EP2017/050920
Other languages
French (fr)
Inventor
Christoph Leussler
Daniel Wirtz
Original Assignee
Koninklijke Philips N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips N.V. filed Critical Koninklijke Philips N.V.
Publication of WO2017129454A1 publication Critical patent/WO2017129454A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6802—Sensor mounted on worn items
    • A61B5/6803—Head-worn items, e.g. helmets, masks, headphones or goggles
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb
    • A61B5/113—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb occurring during breathing
    • A61B5/1135—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb occurring during breathing by monitoring thoracic expansion
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7271—Specific aspects of physiological measurement analysis
    • A61B5/7285—Specific aspects of physiological measurement analysis for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
    • A61B5/0077—Devices for viewing the surface of the body, e.g. camera, magnifying lens
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/024—Detecting, measuring or recording pulse rate or heart rate
    • A61B5/02416—Detecting, measuring or recording pulse rate or heart rate using photoplethysmograph signals, e.g. generated by infrared radiation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
    • A61B5/0816—Measuring devices for examining respiratory frequency
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7221—Determining signal validity, reliability or quality
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
    • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
    • G01R33/567—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution gated by physiological signals, i.e. synchronization of acquired MR data with periodical motion of an object of interest, e.g. monitoring or triggering system for cardiac or respiratory gating
    • G01R33/5673—Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker

Definitions

  • Patient head-mountable device having a vital sign camera for use in a medical scanning modality
  • the invention pertains to head-mountable device, having a vital sign camera, for use in a medical scanning modality, in particular a magnetic resonance imaging system.
  • the vital sign camera may be included in such head-mountable device, in a medical scanning modality, in particular a magnetic resonance imaging system, or both.
  • the invention further pertains to a method of determining, by using such vital sign camera, at least one
  • Determining physiological parameters during scanning examination is usually performed by means of suitable sensors requiring setting up on the patient.
  • a conventional way of determining a respiratory waveform of the patient is by employing a respiration belt-type monitoring device which includes a respiration sensor that usually is attached to the thorax of the patient, and is held by a belt wound around the thorax.
  • a patient head-mountable device for use in a medical scanning modality, comprising a frame member adapted to the shape of a patient's head, at least one optical sensor that is temporarily fixedly attachable to the frame member; wherein the optical sensor is a vital sign camera configured for providing an output signal that is indicative of at least a first type of physiological parameter of the patient and serves as a basis for determining the at least first type of physiological parameter of the patient; wherein the patient head-mountable device includes a data acquisition and analysis unit that is configured to acquire output signals of the optical sensors temporarily fixedly attachable to the frame member and to analyze the acquired output signals by applying pre-determined criteria related to the output signals, and to provide a trigger output signal if one of the pre-determined criteria is fulfilled.
  • head-mountable device as used in this application, shall be understood as any MR-compatible head-mountable device, such as MR-compatible glasses.
  • physiological parameter shall be understood particularly as a physical measure characterizing the function of at least a portion of an individual subject of interest, and shall in particular encompass parameters such as, but not limited to, respiration cycle parameters and cardiac cycle parameters.
  • temporary fixedly attachable shall be understood particularly as an option to be attached in a fixed configuration for a time desired by an operator, and to be transferable from one fixed configuration to another fixed configuration by the operator in a non-destructive way.
  • An object of the present invention is to provide for triggering of the scanning modality on the basis of one or more physiological parameters of the patient to be examined.
  • a further object of the invention is to achieve this triggering without the need of additional cabling in the medical scanning modality. It has recently been shown, that vital signs monitoring provided by the vital sign camera is readily doable and robust using real time video signals derived from the patient skin and/or the patient's chest movement.
  • the integration of miniature camera modules into a set of head-mountable device, such as glasses, for MR and CT imaging has a number of advantages.
  • the frame member provide to the vital signs camera a reference frame that travels with the patient wearing the patient head-mountable device.
  • a definite and robust spatial relationship between the patient and the vital sign camera can be established.
  • the at least one physiological parameter can be determined from motions of a portion of the patient relative to the balance of the patient and irrespective of any motion of the patient as a whole. This is especially advantageous as the quantity to be measured is not determined as a difference of two substantially equally large quantities, a condition that is known to result in high precision requirements.
  • the optical sensor is configured for observing part or all of the patient's face and deriving a cardiac signal of the patient as the first type of physiological parameter.
  • the patient head-mountable device comprises at least one optical sensor that is temporarily fixedly attachable to the frame member and is configured for providing an output signal that is indicative of at least a second type of physiological parameter of the patient and serves as a basis for determining the at least second type of physiological parameter of the patient.
  • the at least one optical sensor is temporarily fixedly attachable to the frame member in a direction to observe the chest motion of the patient, and to derive a respiratory signal of the patient as the second type of physiological parameter.
  • the optical sensor is configured for observing the movement of the patient.
  • the frame member provides to the vital signs camera a reference frame that travels with the patient wearing the patient head-mountable device, the movement of the patient with respect to the ground or the slidably arranged table top for supporting the patient can be measured by this vital sign camera.
  • This measurement may provide the operator of MRI or CT with direct and valuable feedback from the patient. This is because the unease and bulk movement of the patient can be directly observed and, consequently, planned scans can be dismissed or repeated in response to the movement of the patient. Therefore, the amount of deprecated data can be reduced.
  • a medical scanning modality configured for contact- free acquisition of scanning data of at least a portion of a subject of interest, in particular a patient
  • the medical imaging modality comprising a scanning unit having an examination space provided for arranging at least the portion of the subject of interest within, a control unit configured for controlling functions of the medical imaging modality; a signal processing unit that is configured to generate scanning images from the acquired scanning data, at least one vital sign camera is temporarily fixedly attachable to the scanning unit and is configured for providing an output signal that is indicative of at least a second type of physiological parameter of the patient and serves as a basis for determining the at least second type of physiological parameter of the patient, and an embodiment of the patient head-mountable device as disclosed herein.
  • the contemplated medical scanning modalities include, but are not limited to, a magnetic resonance imaging (MRI) apparatus, especially of the bore-type, a computer tomography (CT) apparatus, a single-photon emission computed tomography (SPECT) apparatus, a Positron Emission Tomography (PET) apparatus or an image-guided therapy system such as an MR-LINAC system, an MR Hyperthermia therapy system or an MR-guided High-Intensity Focused Ultrasound (HIFU) system.
  • MRI magnetic resonance imaging
  • CT computer tomography
  • SPECT single-photon emission computed tomography
  • PET Positron Emission Tomography
  • HIFU MR-guided High-Intensity Focused Ultrasound
  • the medical scanning modality is formed as a magnetic resonance imaging system configured for acquiring magnetic resonance images of at least a portion of a subject of interest, usually a patient.
  • the scanning data are formed by magnetic resonance signals and the generated scanning images are formed by magnetic resonance images.
  • the vital sign camera temporarily fixedly attachable to the scanning unit is configured for observing part or all of the patient's body and deriving a respiratory signal of the patient as the second type of physiological parameter.
  • the data acquisition and analysis unit is further configured to acquire output signals of the optical sensors temporarily fixedly attachable to the scanning unit and to analyze the acquired output signals by applying pre-determined criteria related to the output signals, and to provide a trigger output signal if one of the pre-determined criteria is fulfilled.
  • the data acquisition and analysis unit is further configured to compare the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter and to select the acquired output signals with better signal quality.
  • the data acquisition and analysis unit is configured to analyze a correlation of the acquired output signals from both the frame member of the head- mountable device and the scanning unit by applying pre-determined criteria related to the correlation of the two output signals indicating the first type of physiological parameter and the second type of physiological parameter and to provide a trigger output signal if one of the pre-determined criteria is fulfilled.
  • different camera systems located on the head-mountable device, in the coils part, in the bore part of the scanning unit, or in a therapy device can be diversely switched. Different individual cameras can be used for triggering and controlling magnetic resonance imaging system sequencing or therapy devices.
  • having several vital signs cameras can add to the signal quality of the trigger of the scanning unit. Since the trigger is deduced from analysis of the video stream it is influenced by the quality of the stream. In one case, several vital signs cameras in different positions are simultaneously used to derive the trigger. In case the signal quality of one vital sign camera as normally used drops below a predefined threshold, the input of the vital sign camera can be automatically switched to one providing a better signal.
  • the analysis on video streams of different origin allows for generating a correlation between the signals resulting in better definition of e.g. of a falling slope used for triggering.
  • simply adding up signals of different origin will reduce noise and thus increase SNR on the trigger. Both can be done before finally submitting the pulse to the imaging system. We assume that such a measure will improve the trigger quality.
  • control unit is configured to receive the trigger output signal and to control a scanning process being carried out by the medical scanning modality by using the received trigger output signal for gating and/or triggering the acquisition of scanning data.
  • This enables acquiring scanning data that are assigned to a specified value or a specified range of values of the at least one physiological parameter, corresponding to a specific phase of the physiological function such as, but not limited to, a specific phase of the cardiac cycle or a specific phase of the respiratory phase of the patient.
  • a method for determining, by using an embodiment of the patient head-mountable device and the medical scanning modality, at least a first type and second type of physiological parameters of a patient to be examined by a medical scanning modality for gating a scanning process of the medical scanning modality, the method comprising steps of: carrying out a calibration procedure by acquiring an output signal of the optical sensors indicating the first type and the second type of physiological parameter, determining values related to the output signals that are to be used as threshold values, defining at least one criterion related to the output signals with regard to the determined threshold values, acquiring an output signal or output signals of the optical sensors indicating the first type and the second type of physiological parameter, comparing the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter and selecting the acquired output signals with a better signal quality; applying the defined at least one criterion to the selected output signal, generating a trigger output signal if the at least one defined criterion is fulfilled,
  • a method of determining, by using an embodiment of the patient head-mountable device and the medical scanning modality, at least a first type and second type of physiological parameters of a patient to be examined by a medical scanning modality for gating a scanning process of the medical scanning modality comprising steps of: carrying out a calibration procedure by acquiring an output signal of the optical sensors indicating the first type and the second type of physiological parameter, determining values related to the correlation of the output signals indicating the first type and the second type of physiological parameter that are to be used as threshold values, defining at least one criterion related to the correlation of the output signals with regard to the determined threshold values, acquiring an output signal or output signals of the optical sensors indicating the first type and the second type of physiological parameter, correlating the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter; applying the defined at least one criterion to the correlated output signal, generating a trigger output signal if the at least one defined cri
  • a software module for carrying out steps of an embodiment of the disclosed method of determining, by using an embodiment of the patient sensor system as disclosed herein, at least one physiological parameter of a patient to be examined by a medical scanning modality for gating a scanning process of the medical scanning modality.
  • the method steps to be conducted are converted into a program code of the software module, wherein the program code is implementable in a memory unit of the medical scanning modality and is executable by a processor unit of the medical scanning modality.
  • the processor unit may be the processor unit of the control unit that is customary for controlling functions of the medical scanning modality.
  • the processor unit may, alternatively or supplementary, be another processor unit that is especially assigned to execute at least some of the method steps.
  • At least one physiological parameter like breathing rate or heart rate is determined by the measurement by the vital signs camera in either head-mountable device, or the scanning unit, or both.
  • the vital signs camera integrated in a head-mountable device are positioned almost equally on different patients allowing for generating robust and reliable signals to trigger an imaging system.
  • the modulated reflected optical or IR signal is analyzed and a suitable algorithm provides trigger signals to the imaging system.
  • other tasks may be fulfilled using an array of optical sensors such as control of bulk motion, feedback for functional imaging,
  • the software module can enable a robust and reliable execution of the method and can allow for a fast modification of method steps.
  • Fig. 1 shows a schematic illustration of a part of an embodiment of medical imaging modality in accordance with the invention, designed as a magnetic resonance imaging system
  • Fig. 2 schematically illustrates a front view of a configuration of the patient head-mountable device in accordance with the invention and pursuant to Fig. 1, attached at a patient in an operational state,
  • Fig. 3 schematically illustrates a side view of the configuration pursuant to
  • Fig. 4 schematically illustrates a front view of a configuration of the patient head-mountable device and the scanning unit when the patient is positioned within the scanning unit in accordance with the invention and pursuant to Fig. 1 , attached at a patient in an operational state
  • Fig. 5 shows a flow chart of an embodiment of the method in accordance with the invention
  • Fig. 6 shows a flow chart of an embodiment of the method in accordance with the invention.
  • Fig. 1 shows a schematic illustration of a part of an embodiment of a medical imaging modality 10 in accordance with the invention that is configured for contact-free acquisition of scanning data of at least a portion of a subject of interest 20, usually a patient.
  • the medical imaging modality 10 is designed, without limitation for the scope of protection, as a magnetic resonance imaging system.
  • Patient head-mountable device and a patient head- mountable device system, as described for use in this embodiment of the medical imaging modality 10 are also applicable in other medical imaging modalities, such as positron emission tomography devices or computer tomography devices, as will be appreciated to those skilled in the art.
  • Acquired scanning data are formed by magnetic resonance signals and generated scanning images are formed by magnetic resonance images.
  • the magnetic resonance imaging system is thus configured for contact-free acquisition of magnetic resonance images of at least a portion of the subject of interest 20.
  • the magnetic resonance imaging system comprises a scanning unit 12 with a main magnet 14 provided for generating a static magnetic field Bo.
  • the main magnet 14 has a central bore that provides an examination space 16 around a center axis 18 for the subject of interest 20 to be positioned within.
  • the main magnet 14 is configured to generate the static magnetic field Bo at least in the examination space 16.
  • the static magnetic field Bo defines an axial direction of the examination space 16, aligned in parallel to the center axis 18.
  • the magnetic resonance imaging system comprises an examination table 42 having a slidably arranged table top 44 for supporting the subject of interest 20 prior and after an examination outside the examination space 16 as well as while being arranged inside the examination space 16 during the examination.
  • the magnetic resonance imaging system further comprises a magnetic gradient coil system 22 with magnetic gradient coils provided for generating gradient magnetic fields superimposed to the static magnetic field Bo.
  • the magnetic gradient coils are concentrically arranged within the bore of the main magnet 14, as is known in the art.
  • the magnetic resonance imaging system includes a radio frequency antenna device 36 designed as a whole-body coil that is provided for applying a radio frequency magnetic field Bi to the examination space 16 during radio frequency transmit phases to excite nuclei of or within the subject of interest 20.
  • the radio frequency antenna device 36 is also configured for receiving magnetic resonance signals during radio frequency receive phases from the nuclei of or within the portion of the subject of interest 20 that have been excited by applying the radio frequency excitation field Bi .
  • radio frequency transmit phases and radio frequency receive phases are taking place in a consecutive manner.
  • the radio frequency antenna device 36 is arranged concentrically within the bore of the main magnet 14.
  • a cylindrical metal radio frequency shield 24 is arranged concentrically between the magnetic gradient coils of the magnetic gradient coil system 22 and the radio frequency antenna device 36.
  • the magnetic resonance imaging system further comprises a control unit 26 provided for controlling functions of the magnetic resonance imaging system.
  • the control unit 26 comprises a human interface device for displaying and controlling purposes that is designed as a touch screen device 32.
  • the magnetic resonance imaging system includes a radio frequency transmitter unit 38 that is connected to and controlled by the control unit 26.
  • the radio frequency transmitter unit 38 is provided to feed radio frequency power of a magnetic resonance radio frequency to the radio frequency antenna device 36 via a radio frequency switching unit 40 during the radio frequency transmit phases.
  • the radio frequency switching unit 40 directs the magnetic resonance signals from the radio frequency antenna device 36 to a signal processing unit 34 residing in the control unit 26.
  • the signal processing unit 34 is configured for processing acquired magnetic resonance signals to generate scanning images represented by magnetic resonance images of the portion of the subject of interest 20 from the acquired scanning data represented by the magnetic resonance signals. This technique is well known to those skilled in the art and thus need not be described in further detail herein.
  • the control unit 26 further comprises a digital memory unit 28 for at least temporarily storing the generated magnetic resonance images.
  • the magnetic resonance imaging system is connected to a Picture Archiving and Communication System (PACS) of the medical center that it is installed in via a data connection. In this way, data can be transferred between the magnetic resonance imaging system and the PACS.
  • PACS Picture Archiving and Communication System
  • the magnetic resonance imaging system includes a patient head- mountable device system 48 for determining physiological parameters of the subject of interest 20 to be examined by use of the magnetic resonance imaging system.
  • the patient head-mountable device system 48 includes patient head-mountable device 50 and a data acquisition and analysis unit 76.
  • the patient head-mountable device 50 is an eyeglasses that comprises a frame member 52 designed in the conventional U-shape that is adapted to a shape of the patient's head and made from an elastic plastic material (Fig. 2).
  • the patient head-mountable device 50 includes a plurality of identical optical sensors 68.
  • Each optical sensor 68 of the plurality of optical sensors 68 is designed as a vital signs camera.
  • Each optical sensor 68 of the plurality of optical sensors 68 is configured for deriving a cardiac signal of the patient as the first type of physiological parameter.
  • the optical sensor 68 is also configured for observing the movement of the patient.
  • the patient head-mountable device 50 may include electromagnetic induction means 62 that are configured for powering the patient head-mountable device 50 in a wireless way. This is accomplished by positioning the electromagnetic induction means 62 of the patient head-mountable device 50 close to and above corresponding electromagnetic induction means 46 that are permanently installed in one end of the table top 44 of the patient examination table 42, below a portion of the table top 44 that is provided for supporting the patient's head (Fig. 2).
  • each optical sensor 68 is configured for providing an output signal that is indicative of a physiological parameter of the patient and serves as a basis for determining the physiological parameter of the patient.
  • the physiological parameter is the cardiac cycle of the patient as a first type of physiological parameter, which is determined from the output signals of the optical sensors 68 that are indicative of changes of the skin color of the patient.
  • the method for determining the cardiac cycle of the patient is a well-known technology and is therefore not described here in detail.
  • at least one of the optical sensors 68 is temporarily fixedly attached to the frame member 52 in a direction that is suitable to observe the chest motion of the patient, and to derive a respiratory signal of the patient as a second type of physiological parameter.
  • Each optical sensor 68 of the plurality of optical sensors 68 is equipped with a radio frequency data emitter 72 based on Bluetooth ® protocol, and is configured to transmit its output signal in a wireless way to the data acquisition and analysis unit 76.
  • the radio frequency data emitters 72 of the optical sensors 68 are powered by the electromagnetic induction means 62 as described before.
  • the data acquisition and analysis unit 76 is furnished with a radio frequency data receiver 78 based on Bluetooth ® protocol, and is configured to acquire the output signals of the optical sensors 68, e.g. the output signals of the optical sensors 68 indicating the first type of physiological parameter, the output signals of the optical sensors 68 indicating the second type of the physiological parameter, or any combination thereof, and to analyze the acquired output signals by applying pre-determined criteria related to the output signals.
  • the data acquisition and analysis unit 76 may further compare the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter and select output signals with a better signal quality to analyze.
  • the data acquisition and analysis unit 76 may further correlate the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter.
  • the data acquisition and analysis unit 76 is further configured to provide a trigger output signal 80 if one of the pre-determined criteria is fulfilled, which the control unit 26 of the magnetic resonance imaging system is configured to receive and to use for controlling a scanning process to be carried out, as we will be described in more detail in the following.
  • radio frequency antenna device 36 is described in this specific embodiment as a transmit/receive radio frequency coil, it is also contemplated to apply the invention to magnetic resonance imaging systems comprising radio frequency antenna devices configured for receiving magnetic resonance signals which are designed as local coils, as is well known in the art.
  • the magnetic resonance imaging system may, for instance, employ a head coil that is compatible with the patient head-mountable device of the invention.
  • the head coil and surrounding surfaces are covered with a surface material that is highly absorptive with regard to the electromagnetic radiation emitted by the optical emitters, so as to not affect the measurement of the optical sensor by reflected patterns.
  • different vital signs cameras 88, 88', 88" are temporarily fixedly attached to the magnetic gradient coil system 22, therapy devices 98 or in the bore region of the main magnet 14, respectively, and are diversity switched.
  • the vital signs cameras 88, 88', 88" may observe part or all of the patient's body, such as observing the chest motion, and deriving a respiratory signal of the patient as the second type of physiological parameter.
  • the data acquisition and analysis unit 76 is further configured to acquire the output signals of the vital signs cameras 88, 88', 88" indicating the second type of physiological parameter and to analyze the acquired output signals by applying predetermined criteria related to the output signals.
  • a physiological parameter namely the cardiac cycle or respiration cycle
  • a physiological parameter namely the cardiac cycle or respiration cycle
  • a calibration procedure is carried out by acquiring an output signal of the optical sensors indicating the first type and the second type of physiological parameter, namely the cardiac cycle and the respiration cycle respectively.
  • a second step 104 values related to the output signals that are to be used as threshold values are determined.
  • the values are given by the maximum magnitudes of the output signals, which are averaged over a plurality of cardiac cycles or respiration cycle, to obtain a mean amplitude.
  • the at least one criterion related to the output signals with regard to the determined threshold values is defined.
  • the criterion is defined for the output signal to be at least 80% of the mean amplitude.
  • step 108 output signals of the optical sensors indicating the first type and the second type of physiological parameter are acquired.
  • step 110 the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter is compared and the acquired output signals with a better signal quality is selected.
  • step 112 the defined at least one criterion to the selected output signal is applied.
  • a trigger output signal is genearted if the at least one defined criterion is fulfilled, and in the following step 116, the scanning process by making use of generated trigger output signals is gated.
  • a further embodiment of a method for determining, by using the embodiment of the patient head-mountable device system 50 and the medical scanning modality 10 as described before, a physiological parameter, namely the cardiac cycle or respiration cycle, of the patient to be examined by the magnetic resonance imaging system for gating a scanning process of the magnetic resonance imaging system is described.
  • a flow chart of the method is given in Fig. 6.
  • a calibration procedure is carried out by acquiring an output signal of the optical sensors indicating the first type and the second type of physiological parameter, namely the cardiac cycle and the respiration cycle respectively.
  • a second step 124 values related to the output signals indicating the first type and the second type of physiological parameter that are to be used as threshold values are determined.
  • the values are given by the maximum magnitudes of the output signals, which are averaged over a correlation of a plurality of cardiac cycles and a plurality of a respiration cycle, to obtain a mean amplitude.
  • the at least one criterion related to the correlation of the output signals indicating the first type and the second type of physiological parameter with regard to the determined threshold values is defined.
  • the criterion is defined for the output signal to be at least 80% of the mean amplitude.
  • step 1208 output signals of the optical sensors indicating the first type and the second type of physiological parameter are acuquired.
  • the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter are correlated to each other.
  • step 132 the defined at least one criterion to the correlated signal quality of the acquired output signal is applied.
  • a trigger output signal is genearted if the at least one defined criterion is fulfilled, and in the following step 136, the scanning process by making use of generated trigger output signals is gated.
  • the control unit 26 comprises a software module 82 (Fig. 1).
  • the method steps to be conducted are converted into a program code of the software module 82, wherein the program code is implemented in the digital memory unit 28 of the control unit 26 and is executable by the processor unit 30 of the control unit 26.
  • the patient head-mountable device system 48 may include a control unit having a digital memory unit and a processor unit, for instance within the data acquisition and analysis unit 76, the software module may reside in the digital memory unit of the control unit of the patient head-mountable device system 48, and the processor unit of the patient head-mountable device system 48 may be especially configured to carry out the method.

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Abstract

A patient head-mountable device for use in a medical scanning modality, comprising a frame member adapted to the shape of a patient's head, at least one optical sensor that is temporarily fixedly attachable to the frame member; wherein the optical sensor is a vital sign camera configured for providing an output signal that is indicative of at least a first type of physiological parameter of the patient and serves as a basis for determining the at least first type of physiological parameter of the patient; wherein the patient head-mountable device includes a data acquisition and analysis unit that is configured to acquire output signals of the optical sensors temporarily fixedly attachable to the frame member and to analyze the acquired output signals by applying pre-determined criteria related to the output signals, and to provide a trigger output signal if one of the pre-determined criteria is fulfilled.

Description

Patient head-mountable device having a vital sign camera for use in a medical scanning modality
FIELD OF THE INVENTION
The invention pertains to head-mountable device, having a vital sign camera, for use in a medical scanning modality, in particular a magnetic resonance imaging system. The vital sign camera may be included in such head-mountable device, in a medical scanning modality, in particular a magnetic resonance imaging system, or both. The invention further pertains to a method of determining, by using such vital sign camera, at least one
physiological parameter of a patient to be examined by such medical scanning modality for gating a scanning process of the medical scanning modality. BACKGROUND OF THE INVENTION
In the field of medical scanning, it is known to monitor physiological parameters of a patient such as, but not limited to, cardiac cycles and respiratory cycles, and to use the monitored physiological parameters for temporal control, for instance by gating and/or triggering, of a scanning process.
Determining physiological parameters during scanning examination is usually performed by means of suitable sensors requiring setting up on the patient. For instance, a conventional way of determining a respiratory waveform of the patient is by employing a respiration belt-type monitoring device which includes a respiration sensor that usually is attached to the thorax of the patient, and is held by a belt wound around the thorax.
SUMMARY OF THE INVENTION
In one aspect of the present invention, it is provided A patient head-mountable device for use in a medical scanning modality, comprising a frame member adapted to the shape of a patient's head, at least one optical sensor that is temporarily fixedly attachable to the frame member; wherein the optical sensor is a vital sign camera configured for providing an output signal that is indicative of at least a first type of physiological parameter of the patient and serves as a basis for determining the at least first type of physiological parameter of the patient; wherein the patient head-mountable device includes a data acquisition and analysis unit that is configured to acquire output signals of the optical sensors temporarily fixedly attachable to the frame member and to analyze the acquired output signals by applying pre-determined criteria related to the output signals, and to provide a trigger output signal if one of the pre-determined criteria is fulfilled.
The phrase "head-mountable device", as used in this application, shall be understood as any MR-compatible head-mountable device, such as MR-compatible glasses.
The phrase "physiological parameter", as used in this application, shall be understood particularly as a physical measure characterizing the function of at least a portion of an individual subject of interest, and shall in particular encompass parameters such as, but not limited to, respiration cycle parameters and cardiac cycle parameters.
The phrase "temporarily fixedly attachable", as used in this application, shall be understood particularly as an option to be attached in a fixed configuration for a time desired by an operator, and to be transferable from one fixed configuration to another fixed configuration by the operator in a non-destructive way.
An object of the present invention is to provide for triggering of the scanning modality on the basis of one or more physiological parameters of the patient to be examined. Notably, a further object of the invention is to achieve this triggering without the need of additional cabling in the medical scanning modality. It has recently been shown, that vital signs monitoring provided by the vital sign camera is readily doable and robust using real time video signals derived from the patient skin and/or the patient's chest movement. The integration of miniature camera modules into a set of head-mountable device, such as glasses, for MR and CT imaging has a number of advantages. For instance, no external sensors are needed anymore to hamper workflow; the placement of the vital signs cameras are always optimal once the field of view of such devices placed of the rim of a pair of glasses has been identified; using wireless transmission the pre-scan setup of such a head-mountable device is extremely easy, fast and failsafe.
Another advantage of the patient head-mountable device lies in that the frame member provide to the vital signs camera a reference frame that travels with the patient wearing the patient head-mountable device. In this way, a definite and robust spatial relationship between the patient and the vital sign camera can be established. The effect of this is that the at least one physiological parameter can be determined from motions of a portion of the patient relative to the balance of the patient and irrespective of any motion of the patient as a whole. This is especially advantageous as the quantity to be measured is not determined as a difference of two substantially equally large quantities, a condition that is known to result in high precision requirements.
In one embodiment, the optical sensor is configured for observing part or all of the patient's face and deriving a cardiac signal of the patient as the first type of physiological parameter.
In one embodiment, the patient head-mountable device comprises at least one optical sensor that is temporarily fixedly attachable to the frame member and is configured for providing an output signal that is indicative of at least a second type of physiological parameter of the patient and serves as a basis for determining the at least second type of physiological parameter of the patient.
In one embodiment, the at least one optical sensor is temporarily fixedly attachable to the frame member in a direction to observe the chest motion of the patient, and to derive a respiratory signal of the patient as the second type of physiological parameter.
In one embodiment, the optical sensor is configured for observing the movement of the patient. As the frame member provides to the vital signs camera a reference frame that travels with the patient wearing the patient head-mountable device, the movement of the patient with respect to the ground or the slidably arranged table top for supporting the patient can be measured by this vital sign camera. This measurement may provide the operator of MRI or CT with direct and valuable feedback from the patient. This is because the unease and bulk movement of the patient can be directly observed and, consequently, planned scans can be dismissed or repeated in response to the movement of the patient. Therefore, the amount of deprecated data can be reduced.
In yet another aspect of the present invention, a medical scanning modality is provided that is configured for contact- free acquisition of scanning data of at least a portion of a subject of interest, in particular a patient, the medical imaging modality comprising a scanning unit having an examination space provided for arranging at least the portion of the subject of interest within, a control unit configured for controlling functions of the medical imaging modality; a signal processing unit that is configured to generate scanning images from the acquired scanning data, at least one vital sign camera is temporarily fixedly attachable to the scanning unit and is configured for providing an output signal that is indicative of at least a second type of physiological parameter of the patient and serves as a basis for determining the at least second type of physiological parameter of the patient, and an embodiment of the patient head-mountable device as disclosed herein. By furnishing the medical scanning modality with an embodiment of the patient head-mountable device, the respective advantages described for the various embodiments can be accomplished.
In particular, the contemplated medical scanning modalities include, but are not limited to, a magnetic resonance imaging (MRI) apparatus, especially of the bore-type, a computer tomography (CT) apparatus, a single-photon emission computed tomography (SPECT) apparatus, a Positron Emission Tomography (PET) apparatus or an image-guided therapy system such as an MR-LINAC system, an MR Hyperthermia therapy system or an MR-guided High-Intensity Focused Ultrasound (HIFU) system.
In a preferred embodiment, the medical scanning modality is formed as a magnetic resonance imaging system configured for acquiring magnetic resonance images of at least a portion of a subject of interest, usually a patient. The scanning data are formed by magnetic resonance signals and the generated scanning images are formed by magnetic resonance images.
In an embodiment, the vital sign camera temporarily fixedly attachable to the scanning unit is configured for observing part or all of the patient's body and deriving a respiratory signal of the patient as the second type of physiological parameter.
In an embodiment, the data acquisition and analysis unit is further configured to acquire output signals of the optical sensors temporarily fixedly attachable to the scanning unit and to analyze the acquired output signals by applying pre-determined criteria related to the output signals, and to provide a trigger output signal if one of the pre-determined criteria is fulfilled.
In an embodiment, the data acquisition and analysis unit is further configured to compare the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter and to select the acquired output signals with better signal quality.
In an embodiment, the data acquisition and analysis unit is configured to analyze a correlation of the acquired output signals from both the frame member of the head- mountable device and the scanning unit by applying pre-determined criteria related to the correlation of the two output signals indicating the first type of physiological parameter and the second type of physiological parameter and to provide a trigger output signal if one of the pre-determined criteria is fulfilled.
In general, different camera systems located on the head-mountable device, in the coils part, in the bore part of the scanning unit, or in a therapy device can be diversely switched. Different individual cameras can be used for triggering and controlling magnetic resonance imaging system sequencing or therapy devices. In addition, having several vital signs cameras can add to the signal quality of the trigger of the scanning unit. Since the trigger is deduced from analysis of the video stream it is influenced by the quality of the stream. In one case, several vital signs cameras in different positions are simultaneously used to derive the trigger. In case the signal quality of one vital sign camera as normally used drops below a predefined threshold, the input of the vital sign camera can be automatically switched to one providing a better signal. In another embodiment the analysis on video streams of different origin (and different views of the patient) allows for generating a correlation between the signals resulting in better definition of e.g. of a falling slope used for triggering. Furthermore, simply adding up signals of different origin will reduce noise and thus increase SNR on the trigger. Both can be done before finally submitting the pulse to the imaging system. We assume that such a measure will improve the trigger quality.
In a preferred embodiment of the medical scanning modality, the control unit is configured to receive the trigger output signal and to control a scanning process being carried out by the medical scanning modality by using the received trigger output signal for gating and/or triggering the acquisition of scanning data. This enables acquiring scanning data that are assigned to a specified value or a specified range of values of the at least one physiological parameter, corresponding to a specific phase of the physiological function such as, but not limited to, a specific phase of the cardiac cycle or a specific phase of the respiratory phase of the patient.
In another aspect of the invention, a method is provided for determining, by using an embodiment of the patient head-mountable device and the medical scanning modality, at least a first type and second type of physiological parameters of a patient to be examined by a medical scanning modality for gating a scanning process of the medical scanning modality, the method comprising steps of: carrying out a calibration procedure by acquiring an output signal of the optical sensors indicating the first type and the second type of physiological parameter, determining values related to the output signals that are to be used as threshold values, defining at least one criterion related to the output signals with regard to the determined threshold values, acquiring an output signal or output signals of the optical sensors indicating the first type and the second type of physiological parameter, comparing the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter and selecting the acquired output signals with a better signal quality; applying the defined at least one criterion to the selected output signal, generating a trigger output signal if the at least one defined criterion is fulfilled, and gating the scanning process by making use of generated trigger output signals.
In another aspect of the invention, a method of determining, by using an embodiment of the patient head-mountable device and the medical scanning modality, at least a first type and second type of physiological parameters of a patient to be examined by a medical scanning modality for gating a scanning process of the medical scanning modality, the method comprising steps of: carrying out a calibration procedure by acquiring an output signal of the optical sensors indicating the first type and the second type of physiological parameter, determining values related to the correlation of the output signals indicating the first type and the second type of physiological parameter that are to be used as threshold values, defining at least one criterion related to the correlation of the output signals with regard to the determined threshold values, acquiring an output signal or output signals of the optical sensors indicating the first type and the second type of physiological parameter, correlating the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter; applying the defined at least one criterion to the correlated output signal, generating a trigger output signal if the at least one defined criterion is fulfilled, and gating the scanning process by making use of generated trigger output signals.
In yet another aspect of the present invention, a software module is provided for carrying out steps of an embodiment of the disclosed method of determining, by using an embodiment of the patient sensor system as disclosed herein, at least one physiological parameter of a patient to be examined by a medical scanning modality for gating a scanning process of the medical scanning modality. The method steps to be conducted are converted into a program code of the software module, wherein the program code is implementable in a memory unit of the medical scanning modality and is executable by a processor unit of the medical scanning modality. The processor unit may be the processor unit of the control unit that is customary for controlling functions of the medical scanning modality. The processor unit may, alternatively or supplementary, be another processor unit that is especially assigned to execute at least some of the method steps.
At least one physiological parameter like breathing rate or heart rate is determined by the measurement by the vital signs camera in either head-mountable device, or the scanning unit, or both. In practice, the patient's face is not covered by clothes, vital signs cameras integrated in a head-mountable device are positioned almost equally on different patients allowing for generating robust and reliable signals to trigger an imaging system. The modulated reflected optical or IR signal is analyzed and a suitable algorithm provides trigger signals to the imaging system. Furthermore other tasks may be fulfilled using an array of optical sensors such as control of bulk motion, feedback for functional imaging,
determination of the status of the patient and correlations between these.
The software module can enable a robust and reliable execution of the method and can allow for a fast modification of method steps.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. Such embodiment does not necessarily represent the full scope of the invention, however, and reference is made therefore to the claims and herein for interpreting the scope of the invention.
In the drawings:
Fig. 1 shows a schematic illustration of a part of an embodiment of medical imaging modality in accordance with the invention, designed as a magnetic resonance imaging system,
Fig. 2 schematically illustrates a front view of a configuration of the patient head-mountable device in accordance with the invention and pursuant to Fig. 1, attached at a patient in an operational state,
Fig. 3 schematically illustrates a side view of the configuration pursuant to
Fig. 2,
Fig. 4 schematically illustrates a front view of a configuration of the patient head-mountable device and the scanning unit when the patient is positioned within the scanning unit in accordance with the invention and pursuant to Fig. 1 , attached at a patient in an operational state,
Fig. 5 shows a flow chart of an embodiment of the method in accordance with the invention,
Fig. 6 shows a flow chart of an embodiment of the method in accordance with the invention. DETAILED DESCRIPTION OF EMBODIMENTS
Fig. 1 shows a schematic illustration of a part of an embodiment of a medical imaging modality 10 in accordance with the invention that is configured for contact-free acquisition of scanning data of at least a portion of a subject of interest 20, usually a patient. The medical imaging modality 10 is designed, without limitation for the scope of protection, as a magnetic resonance imaging system. Patient head-mountable device and a patient head- mountable device system, as described for use in this embodiment of the medical imaging modality 10, are also applicable in other medical imaging modalities, such as positron emission tomography devices or computer tomography devices, as will be appreciated to those skilled in the art.
Acquired scanning data are formed by magnetic resonance signals and generated scanning images are formed by magnetic resonance images.
The magnetic resonance imaging system is thus configured for contact-free acquisition of magnetic resonance images of at least a portion of the subject of interest 20. To this end, the magnetic resonance imaging system comprises a scanning unit 12 with a main magnet 14 provided for generating a static magnetic field Bo. The main magnet 14 has a central bore that provides an examination space 16 around a center axis 18 for the subject of interest 20 to be positioned within. The main magnet 14 is configured to generate the static magnetic field Bo at least in the examination space 16. The static magnetic field Bo defines an axial direction of the examination space 16, aligned in parallel to the center axis 18.
The magnetic resonance imaging system comprises an examination table 42 having a slidably arranged table top 44 for supporting the subject of interest 20 prior and after an examination outside the examination space 16 as well as while being arranged inside the examination space 16 during the examination.
The magnetic resonance imaging system further comprises a magnetic gradient coil system 22 with magnetic gradient coils provided for generating gradient magnetic fields superimposed to the static magnetic field Bo. The magnetic gradient coils are concentrically arranged within the bore of the main magnet 14, as is known in the art.
Further, the magnetic resonance imaging system includes a radio frequency antenna device 36 designed as a whole-body coil that is provided for applying a radio frequency magnetic field Bi to the examination space 16 during radio frequency transmit phases to excite nuclei of or within the subject of interest 20. The radio frequency antenna device 36 is also configured for receiving magnetic resonance signals during radio frequency receive phases from the nuclei of or within the portion of the subject of interest 20 that have been excited by applying the radio frequency excitation field Bi . In an operational state of the magnetic resonance imaging system, radio frequency transmit phases and radio frequency receive phases are taking place in a consecutive manner. The radio frequency antenna device 36 is arranged concentrically within the bore of the main magnet 14. As is well known in the art, a cylindrical metal radio frequency shield 24 is arranged concentrically between the magnetic gradient coils of the magnetic gradient coil system 22 and the radio frequency antenna device 36.
The magnetic resonance imaging system further comprises a control unit 26 provided for controlling functions of the magnetic resonance imaging system. The control unit 26 comprises a human interface device for displaying and controlling purposes that is designed as a touch screen device 32.
Furthermore, the magnetic resonance imaging system includes a radio frequency transmitter unit 38 that is connected to and controlled by the control unit 26. The radio frequency transmitter unit 38 is provided to feed radio frequency power of a magnetic resonance radio frequency to the radio frequency antenna device 36 via a radio frequency switching unit 40 during the radio frequency transmit phases. During radio frequency receive phases, the radio frequency switching unit 40 directs the magnetic resonance signals from the radio frequency antenna device 36 to a signal processing unit 34 residing in the control unit 26. The signal processing unit 34 is configured for processing acquired magnetic resonance signals to generate scanning images represented by magnetic resonance images of the portion of the subject of interest 20 from the acquired scanning data represented by the magnetic resonance signals. This technique is well known to those skilled in the art and thus need not be described in further detail herein.
The control unit 26 further comprises a digital memory unit 28 for at least temporarily storing the generated magnetic resonance images. The magnetic resonance imaging system is connected to a Picture Archiving and Communication System (PACS) of the medical center that it is installed in via a data connection. In this way, data can be transferred between the magnetic resonance imaging system and the PACS.
Moreover, the magnetic resonance imaging system includes a patient head- mountable device system 48 for determining physiological parameters of the subject of interest 20 to be examined by use of the magnetic resonance imaging system.
The patient head-mountable device system 48 includes patient head-mountable device 50 and a data acquisition and analysis unit 76. The patient head-mountable device 50 is an eyeglasses that comprises a frame member 52 designed in the conventional U-shape that is adapted to a shape of the patient's head and made from an elastic plastic material (Fig. 2).
Furthermore, the patient head-mountable device 50 includes a plurality of identical optical sensors 68. Each optical sensor 68 of the plurality of optical sensors 68 is designed as a vital signs camera. Each optical sensor 68 of the plurality of optical sensors 68 is configured for deriving a cardiac signal of the patient as the first type of physiological parameter. The optical sensor 68 is also configured for observing the movement of the patient.
The patient head-mountable device 50 may include electromagnetic induction means 62 that are configured for powering the patient head-mountable device 50 in a wireless way. This is accomplished by positioning the electromagnetic induction means 62 of the patient head-mountable device 50 close to and above corresponding electromagnetic induction means 46 that are permanently installed in one end of the table top 44 of the patient examination table 42, below a portion of the table top 44 that is provided for supporting the patient's head (Fig. 2).
As is shown in Fig.3, two or more optical sensors 68 are temporarily fixedly attached to the frame member 52 by holder members designed as fixation clamps 84. An optical path 66 of the optical sensors 68 are shown in Fig. 2. Each optical sensor 68 is configured for providing an output signal that is indicative of a physiological parameter of the patient and serves as a basis for determining the physiological parameter of the patient. In this specific embodiment, the physiological parameter is the cardiac cycle of the patient as a first type of physiological parameter, which is determined from the output signals of the optical sensors 68 that are indicative of changes of the skin color of the patient. The method for determining the cardiac cycle of the patient is a well-known technology and is therefore not described here in detail. Alternatively, at least one of the optical sensors 68 is temporarily fixedly attached to the frame member 52 in a direction that is suitable to observe the chest motion of the patient, and to derive a respiratory signal of the patient as a second type of physiological parameter.
Each optical sensor 68 of the plurality of optical sensors 68 is equipped with a radio frequency data emitter 72 based on Bluetooth® protocol, and is configured to transmit its output signal in a wireless way to the data acquisition and analysis unit 76. The radio frequency data emitters 72 of the optical sensors 68 are powered by the electromagnetic induction means 62 as described before. The data acquisition and analysis unit 76 is furnished with a radio frequency data receiver 78 based on Bluetooth® protocol, and is configured to acquire the output signals of the optical sensors 68, e.g. the output signals of the optical sensors 68 indicating the first type of physiological parameter, the output signals of the optical sensors 68 indicating the second type of the physiological parameter, or any combination thereof, and to analyze the acquired output signals by applying pre-determined criteria related to the output signals. The data acquisition and analysis unit 76 may further compare the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter and select output signals with a better signal quality to analyze. The data acquisition and analysis unit 76 may further correlate the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter. The data acquisition and analysis unit 76 is further configured to provide a trigger output signal 80 if one of the pre-determined criteria is fulfilled, which the control unit 26 of the magnetic resonance imaging system is configured to receive and to use for controlling a scanning process to be carried out, as we will be described in more detail in the following.
Although the radio frequency antenna device 36 is described in this specific embodiment as a transmit/receive radio frequency coil, it is also contemplated to apply the invention to magnetic resonance imaging systems comprising radio frequency antenna devices configured for receiving magnetic resonance signals which are designed as local coils, as is well known in the art. The magnetic resonance imaging system may, for instance, employ a head coil that is compatible with the patient head-mountable device of the invention. In this case, the head coil and surrounding surfaces are covered with a surface material that is highly absorptive with regard to the electromagnetic radiation emitted by the optical emitters, so as to not affect the measurement of the optical sensor by reflected patterns.
As is shown in Fig.4, different vital signs cameras 88, 88', 88" are temporarily fixedly attached to the magnetic gradient coil system 22, therapy devices 98 or in the bore region of the main magnet 14, respectively, and are diversity switched. The vital signs cameras 88, 88', 88" may observe part or all of the patient's body, such as observing the chest motion, and deriving a respiratory signal of the patient as the second type of physiological parameter. The data acquisition and analysis unit 76 is further configured to acquire the output signals of the vital signs cameras 88, 88', 88" indicating the second type of physiological parameter and to analyze the acquired output signals by applying predetermined criteria related to the output signals. Next, an embodiment of a method for determining, by using the embodiment of the patient head-mountable device system 50 and the medical scanning modality 10 as described before, a physiological parameter, namely the cardiac cycle or respiration cycle, of the patient to be examined by the magnetic resonance imaging system for gating a scanning process of the magnetic resonance imaging system is described. A flow chart of the method is given in Fig. 5. In preparation of carrying out the method, it shall be understood that all involved units and devices are in an operational state and configured as illustrated in Fig. 1.
In a first step 102, a calibration procedure is carried out by acquiring an output signal of the optical sensors indicating the first type and the second type of physiological parameter, namely the cardiac cycle and the respiration cycle respectively.
In a second step 104, values related to the output signals that are to be used as threshold values are determined. In this embodiment, the values are given by the maximum magnitudes of the output signals, which are averaged over a plurality of cardiac cycles or respiration cycle, to obtain a mean amplitude.
In the next step 106, the at least one criterion related to the output signals with regard to the determined threshold values is defined. In this embodiment, the criterion is defined for the output signal to be at least 80% of the mean amplitude.
In the following step 108, output signals of the optical sensors indicating the first type and the second type of physiological parameter are acquired.
In the following step 110, the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter is compared and the acquired output signals with a better signal quality is selected.
In the following step 112, the defined at least one criterion to the selected output signal is applied.
In the following step 114,a trigger output signal is genearted if the at least one defined criterion is fulfilled, and in the following step 116, the scanning process by making use of generated trigger output signals is gated.
A further embodiment of a method for determining, by using the embodiment of the patient head-mountable device system 50 and the medical scanning modality 10 as described before, a physiological parameter, namely the cardiac cycle or respiration cycle, of the patient to be examined by the magnetic resonance imaging system for gating a scanning process of the magnetic resonance imaging system is described. A flow chart of the method is given in Fig. 6. In a first step 122, a calibration procedure is carried out by acquiring an output signal of the optical sensors indicating the first type and the second type of physiological parameter, namely the cardiac cycle and the respiration cycle respectively.
In a second step 124, values related to the output signals indicating the first type and the second type of physiological parameter that are to be used as threshold values are determined. In this embodiment, the values are given by the maximum magnitudes of the output signals, which are averaged over a correlation of a plurality of cardiac cycles and a plurality of a respiration cycle, to obtain a mean amplitude.
In the next step 126, the at least one criterion related to the correlation of the output signals indicating the first type and the second type of physiological parameter with regard to the determined threshold values is defined. In this embodiment, the criterion is defined for the output signal to be at least 80% of the mean amplitude.
In the following step 128, output signals of the optical sensors indicating the first type and the second type of physiological parameter are acuquired.
In the following step 130, the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter are correlated to each other.
In the following step 132, the defined at least one criterion to the correlated signal quality of the acquired output signal is applied.
In the following step 134,a trigger output signal is genearted if the at least one defined criterion is fulfilled, and in the following step 136, the scanning process by making use of generated trigger output signals is gated.
In order to be able to carry out the method, the control unit 26 comprises a software module 82 (Fig. 1). The method steps to be conducted are converted into a program code of the software module 82, wherein the program code is implemented in the digital memory unit 28 of the control unit 26 and is executable by the processor unit 30 of the control unit 26. Alternatively, the patient head-mountable device system 48 may include a control unit having a digital memory unit and a processor unit, for instance within the data acquisition and analysis unit 76, the software module may reside in the digital memory unit of the control unit of the patient head-mountable device system 48, and the processor unit of the patient head-mountable device system 48 may be especially configured to carry out the method.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; 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.

Claims

CLAIMS:
1. A patient head-mountable device for use in a medical scanning modality, comprising:
- a frame member adapted to the shape of a patient's head,
- at least one optical sensor that is temporarily fixedly attachable to the frame member;
- wherein the at least one optical sensor is a vital sign camera configured for providing an output signal that is indicative of at least a first type of physiological parameter of the patient and serves as a basis for determining the at least first type of physiological parameter of the patient;
- wherein the patient head-mountable device includes a data acquisition and analysis unit that is configured to acquire output signals of the optical sensors temporarily fixedly attachable to the frame member and to analyze the acquired output signals by applying pre-determined criteria related to the output signals, and to provide a trigger output signal if one of the pre-determined criteria is fulfilled,
- at least one optical sensor that is temporarily fixedly attachable to the frame member and is configured for providing an output signal that is indicative of at least a second type of physiological parameter of the patient and serves as a basis for determining the at least second type of physiological parameter of the patient,
- wherein the at least one optical sensor is temporarily fixedly attachable to the frame member in a direction to observe the chest motion of the patient, and to derive a respiratory signal of the patient as the second type of physiological parameter.
2. The patient head-mountable device as claimed in claim 1, wherein the optical sensor is configured for observing part or all of the patient's face and deriving a cardiac signal of the patient as the first type of physiological parameter. serves
3. The patient head-mountable device as claimed in claim 1, wherein the optical sensor is configured for observing the movement of the patient.
4. A medical scanning modality that is configured for contact- free acquisition of scanning data of at least a portion of a subject of interest, in particular a patient, the medical imaging modality comprising
a scanning unit having an examination space provided for arranging at least the portion of the subject of interest within,
a control unit configured for controlling functions of the medical imaging modality;
a signal processing unit that is configured to generate scanning images from the acquired scanning data,
at least one vital sign camera that is temporarily fixedly attachable to the scanning unit and is configured for providing an output signal that is indicative of at least the second type of physiological parameter of the patient and serves as a basis for determining the at least second type of physiological parameter of the patient,
the patient head-mountable device as claimed in claim 1.
5. A medical scanning modality as claimed in claim 4, wherein the medical imaging modality is formed as a magnetic resonance imaging system configured for acquiring magnetic resonance images of at least a portion of a subject of interest, and wherein the scanning data are formed by magnetic resonance signals and the generated scanning images are formed by magnetic resonance images.
6. A medical scanning modality as claimed in claim 4, wherein the vital sign camera temporarily fixedly attachable to the scanning unit is configured for observing part or all of the patient's body and deriving a respiratory signal of the patient as the second type of physiological parameter.
7. A medical scanning modality as claimed in claim 4, wherein the data acquisition and analysis unit is further configured to acquire output signals of the optical sensors temporarily fixedly attachable to the scanning unit and to analyze the acquired output signals by applying pre-determined criteria related to the output signals, and to provide a trigger output signal if one of the pre-determined criteria is fulfilled.
8. A medical scanning modality as claimed in claim 7, wherein the data acquisition and analysis unit is further configured to compare the signal quality from the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter, and to select the acquired output signals with better signal quality.
9. A medical scanning modality as claimed in claim 7, wherein the data acquisition and analysis unit is configured to analyze a correlation of the acquired output signals indicating the first type of physiological parameter and the second type of
physiological parameter by applying pre-determined criteria related to the correlation of the two output signals and to provide a trigger output signal if one of the pre-determined criteria is fulfilled.
10. The medical scanning modality as claimed in claim 4, wherein the control unit is configured to receive the trigger output signal and to control a scanning process being carried out by the medical scanning modality by using the received trigger output signal.
11. A method of determining, by using an embodiment of the medical scanning modality in claim 4, at least a first type and second type of physiological parameters of a patient to be examined by a medical scanning modality for gating a scanning process of the medical scanning modality, the method comprising steps of:
carrying out a calibration procedure by acquiring an output signal of the optical sensors indicating the first type and the second type of physiological parameter,
determining values related to the output signals that are to be used as threshold values,
defining at least one criterion related to the output signals with regard to the determined threshold values,
acquiring an output signal or output signals of the optical sensors indicating the first type and the second type of physiological parameter,
comparing the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter and selecting the acquired output signals with a better signal quality;
applying the defined at least one criterion to the selected output signal, generating a trigger output signal if the at least one defined criterion is fulfilled, and
gating the scanning process by making use of generated trigger output signals.
12. A method of determining, by using an embodiment of the medical scanning modality in claim 4, at least a first type and second type of physiological parameters of a patient to be examined by a medical scanning modality for gating a scanning process of the medical scanning modality, the method comprising steps of:
carrying out a calibration procedure by acquiring an output signal of the optical sensors indicating the first type and the second type of physiological parameter, determining values related to the correlation of the output signals indicating the first type and the second type of physiological parameter that are to be used as threshold values,
defining at least one criterion related to the correlation of the output signals with regard to the determined threshold values,
acquiring an output signal or output signals of the optical sensors indicating the first type and the second type of physiological parameter,
correlating the signal quality of the acquired output signals of the optical sensors indicating the first type of physiological parameter and the second type of physiological parameter;
applying the defined at least one criterion to the correlated signal quality of the acquired output signal,
generating a trigger output signal if the at least one defined criterion is fulfilled, and
- gating the scanning process by making use of generated trigger output signals.
13. Method of claim 11, wherein the medical scanning modality further comprises a digital memory unit and a processor unit.
14. A software module for carrying out the method as claimed in claim 13, wherein the method steps to be conducted are converted into a program code of the software module, wherein the program code is implementable in the digital memory unit of the medical scanning modality and is executable by the processor unit of the medical scanning modality.
PCT/EP2017/050920 2016-01-25 2017-01-18 Patient head-mountable device having a vital sign camera for use in a medical scanning modality WO2017129454A1 (en)

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