WO2012137488A1 - 温度推定方法、温度推定装置及びプログラム - Google Patents
温度推定方法、温度推定装置及びプログラム Download PDFInfo
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- WO2012137488A1 WO2012137488A1 PCT/JP2012/002326 JP2012002326W WO2012137488A1 WO 2012137488 A1 WO2012137488 A1 WO 2012137488A1 JP 2012002326 W JP2012002326 W JP 2012002326W WO 2012137488 A1 WO2012137488 A1 WO 2012137488A1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N7/00—Ultrasound therapy
- A61N7/02—Localised ultrasound hyperthermia
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/48—Diagnostic techniques
- A61B8/485—Diagnostic techniques involving measuring strain or elastic properties
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/52—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/5215—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of medical diagnostic data
- A61B8/5223—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of medical diagnostic data for extracting a diagnostic or physiological parameter from medical diagnostic data
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
- G01S7/52023—Details of receivers
- G01S7/52036—Details of receivers using analysis of echo signal for target characterisation
- G01S7/52042—Details of receivers using analysis of echo signal for target characterisation determining elastic properties of the propagation medium or of the reflective target
-
- G—PHYSICS
- G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
- G16H—HEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA
- G16H50/00—ICT specially adapted for medical diagnosis, medical simulation or medical data mining; ICT specially adapted for detecting, monitoring or modelling epidemics or pandemics
- G16H50/30—ICT specially adapted for medical diagnosis, medical simulation or medical data mining; ICT specially adapted for detecting, monitoring or modelling epidemics or pandemics for calculating health indices; for individual health risk assessment
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
- A61B2017/00017—Electrical control of surgical instruments
- A61B2017/00022—Sensing or detecting at the treatment site
- A61B2017/00084—Temperature
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
- A61B2017/00017—Electrical control of surgical instruments
- A61B2017/00022—Sensing or detecting at the treatment site
- A61B2017/00106—Sensing or detecting at the treatment site ultrasonic
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
- A61B2018/00636—Sensing and controlling the application of energy
- A61B2018/00773—Sensed parameters
- A61B2018/00791—Temperature
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/01—Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
- G01S7/52023—Details of receivers
- G01S7/52036—Details of receivers using analysis of echo signal for target characterisation
Definitions
- the present invention relates to a temperature estimation method, a temperature estimation device, and a program for estimating a temperature of a predetermined part inside a living body by using an ultrasonic signal, for example.
- HIFU treatment using high-focus ultrasound has been performed.
- HIFU treatment a powerful ultrasonic signal is focused on a treatment target site such as a tumor through the patient's body surface, thereby raising the temperature of the treatment target site to a predetermined temperature (for example, about 80 to 90 ° C.).
- a predetermined temperature for example, about 80 to 90 ° C.
- This is a treatment method that necroses the target site.
- a temperature estimation method using an ultrasonic signal for example, see Patent Documents 1 to 3 and Non-Patent Documents 1 and 2 is performed.
- the temperature estimation method using the conventional ultrasonic signal has a problem that the temperature cannot be accurately estimated and the temperature range in which the temperature can be estimated is narrow.
- the present invention solves the above-described conventional problems, and an object of the present invention is to estimate a temperature with high accuracy and to estimate a temperature in a wide temperature range, a temperature estimation device, and Is to provide a program.
- a temperature estimation method is a temperature estimation method for estimating a temperature of a target region using an ultrasonic signal, and scans the target region with an ultrasonic signal. And an echo shift, which is a change amount that changes depending on the temperature of the target region based on the scan signal.
- An echo shift calculation step to calculate, and a strain that is a change rate in which the moving distance when the ultrasonic signal passes through the target region apparently changes depending on the temperature of the target region based on the calculated echo shift.
- a strain calculation step for calculating the strain, and a strain rate that is a temporal change rate of the strain is calculated based on the calculated strain. Including a train rate calculating step, using the relationship between the predetermined strain and strain rate and temperature, and a temperature estimation step of estimating the temperature of the target region corresponding to the calculated strain and strain rate, a.
- the present invention can be realized not only as a method but also as an apparatus using processing steps as steps constituting the method, as a program for causing a computer to execute the steps, or as a computer readable recording of the program. It can also be realized as a recording medium such as a CD-ROM or as information, data or a signal indicating the program. These programs, information, data, and signals may be distributed via a communication network such as the Internet.
- the temperature of the target region corresponding to the calculated strain and strain rate is estimated using a predetermined relationship between the strain, the strain rate, and the temperature, so that the temperature is accurately determined.
- the temperature can be estimated over a wide temperature range.
- FIG. 1 is a block diagram showing a configuration of a temperature estimation apparatus according to Embodiment 1 of the present invention.
- FIG. 2 is a diagram for explaining the scan signal.
- FIG. 3 is a block diagram specifically illustrating the configuration of the signal processing unit of FIG.
- FIG. 4 is a block diagram specifically illustrating the configuration of the preprocessing unit.
- FIG. 5 is a diagram illustrating a damaged frame generated in the scan signal.
- FIG. 6 is a block diagram specifically illustrating the configuration of the echo shift calculation unit.
- FIG. 7 is a diagram for explaining an echo shift calculation step.
- FIG. 8 is a diagram for explaining the abnormal value correcting step.
- FIG. 9 is a block diagram specifically illustrating the configuration of the strain calculation unit.
- FIG. 10 is a block diagram specifically showing the configuration of the strain rate calculation unit.
- FIG. 11 is a block diagram specifically illustrating the configuration of the temperature estimation unit.
- FIG. 12 is a flowchart showing a flow of temperature estimation by the temperature estimation method according to Embodiment 1 of the present invention.
- FIG. 13 is a diagram for explaining the temperature estimation step.
- FIG. 14 is a diagram showing experimental results comparing the temperature estimation method of the present invention and the conventional temperature estimation method.
- FIG. 15 is a diagram showing experimental results comparing the temperature estimation method of the present invention and the conventional temperature estimation method.
- FIG. 16 is a block diagram showing the configuration of the temperature estimation apparatus according to Embodiment 2 of the present invention.
- FIG. 17 is a block diagram showing a configuration of a temperature estimation apparatus according to Embodiment 3 of the present invention.
- FIG. 18 is a diagram showing the relationship between the modeled temperature and the strain in the conventional temperature estimation method.
- FIG. 18 is a diagram showing the relationship between the modeled temperature and the strain in the conventional temperature estimation method.
- the temperature of the treatment target site or the like is estimated by utilizing the fact that the speed of the ultrasonic signal changes depending on the temperature. For example, before and after performing the HIFU treatment by focusing the heating ultrasonic signal on the treatment target site, the speed of the temperature estimation ultrasonic signal changes as the temperature of the treatment target site changes. As the velocity of the ultrasonic signal changes in this way, the moving distance when the ultrasonic signal passes through the treatment target site apparently changes. This change rate of the movement distance is referred to as a strain.
- the strain is calculated based on the difference between the ultrasonic signal before the treatment and the ultrasonic signal during the treatment, and then the temperature is calculated based on the model equation indicating the relationship between the temperature and the strain.
- this model equation is approximated by a quadratic function.
- the temperature can be estimated only in a relatively low temperature range (about 30 to 50 ° C.).
- a relatively high temperature range about 70 to 90 ° C.
- (Conventional temperature estimation method 3) In the conventional temperature estimation method 3, a bio-heat transfer equation is used as a model formula. First, parameters of the model formula are obtained at the time of calibration, and further, a relational expression indicating the relationship between temperature and strain is obtained. For example, at the time of HIFU treatment, the temperature of the treatment target site is estimated based on the model formula. After that, the strain is obtained from the estimated temperature by calculation based on the above relational expression, and the parameters of the model expression are successively set so that the error between the calculated strain and the strain obtained from the RF (Radio Frequency) signal is reduced. Correct it.
- RF Radio Frequency
- the conventional temperature estimation method 3 has a problem that it is difficult to obtain a parameter of the model formula, and thus it is difficult to put it to practical use.
- a temperature estimation method is a temperature estimation method for estimating a temperature of a target region using an ultrasonic signal, and the target region is detected by an ultrasonic signal.
- the time required for the ultrasonic signal to pass through the target region based on the scan signal is a change amount that changes depending on the temperature of the target region based on the scan signal.
- An echo shift calculating step for calculating an echo shift, and a rate of change in which the moving distance when the ultrasonic signal passes through the target region apparently changes depending on the temperature of the target region based on the calculated echo shift
- a strain calculation step for calculating a strain, and a strain rate that is a temporal change rate of the strain based on the calculated strain.
- a strain rate calculating step to be output; and a temperature estimating step of estimating a temperature of the target region corresponding to the calculated strain and the strain rate using a predetermined strain and a relationship between the strain rate and the temperature. .
- the temperature can be estimated with high accuracy, and the temperature can be estimated in a wide temperature range.
- the linear model equation indicating the relationship between the strain, the strain rate, and the temperature is used to correspond to the calculated strain and the strain rate. You may comprise so that the temperature of an object area
- region may be estimated.
- the temperature can be predicted by using the linear model expression indicating the relationship between the strain, the strain rate, and the temperature.
- the method further includes a preprocessing step of removing a damaged frame generated in the scan signal due to a disturbance.
- the damaged frame is detected in the preprocessing step.
- An echo shift may be calculated based on the removed scan signal.
- the damaged frame generated in the scan signal can be removed as preprocessing before calculating the echo shift.
- the echo shift calculation step includes an echo shift calculation step of calculating a raw echo shift based on the received scan signal, and the calculated raw echo
- An abnormal value correction step for obtaining an echo shift caused by a temperature change by correcting an abnormal value not caused by a temperature change in the shift, and a noise attenuation for attenuating noise included in the echo shift caused by the temperature change by a noise filter And a step.
- the echo shift caused by the temperature change can be obtained by correcting the abnormal value not caused by the temperature change in the calculated raw echo shift.
- the abnormal value correction step includes echo shift prediction for calculating a predicted echo shift based on the raw echo shift calculated in the echo shift calculation step.
- a parameter adjusting step for adjusting parameters of the model, a predicted echo shift calculating step for calculating the predicted echo shift based on the optimized echo shift prediction model, and scanning the predicted echo shift and the target region.
- a threshold value setting step for setting a threshold value based on the RF signal obtained from the above, and among the data points of the raw echo shift, a data point that is the abnormal value exceeding the threshold value Data point to be modified based on the corresponding data point
- correction step may be configured to include.
- an abnormal value can be detected.
- the echo shift prediction model may be configured to be an error function or a complementary error function.
- the echo shift prediction model can be configured with an error function or a complementary error function.
- the threshold setting step includes an interval setting step of setting an interval between the upper threshold and the lower threshold as the threshold, and the intensity of the RF signal May be configured to include a threshold adjustment step of adjusting the upper threshold and the lower threshold.
- the scan signal is calculated using a model formula for predicting an echo shift based on a product of depth and time and a depth.
- the strain rate may be calculated so that the error between the echo shift calculated based on the above and the echo shift predicted based on the model formula is minimized.
- the strain rate can be calculated.
- the model formula used in the strain rate calculation step may be a linear model formula.
- the model formula used in the strain rate calculation step can be configured by a linear model formula.
- the algorithm parameter of the linear model formula used in the temperature estimation step is an alignment step of aligning the position of the thermocouple with respect to the target region to be heated.
- You may comprise.
- the positioning step includes a step of aligning the position of the thermocouple with respect to the target region to be heated using a B-mode image; Activating a heating source that outputs an ultrasonic signal to change the temperature; measuring the temperature of the target region with the thermocouple while displacing the heating source in space; and the thermocouple. And a step of stopping the displacement of the heating source when the temperature measured by the step is minimized.
- the position of the thermocouple can be aligned with the target region to be heated.
- the temperature estimation method further includes a temperature correction step of correcting the temperature estimated by the temperature estimation step based on an objective function that takes into account the spatial continuity of the temperature. You may comprise.
- the temperature estimated by the temperature estimation step can be corrected in consideration of the spatial continuity of the temperature.
- the temperature estimation step is further based on an objective function that takes into account the distance between the heat source position heated by the heating ultrasonic signal and the target region.
- a temperature correction step for correcting the temperature estimated by the above may be included.
- the temperature estimated by the temperature estimation step can be corrected in consideration of the distance between the heat source position heated by the heating ultrasonic signal (for example, HIFU) and the target region.
- the heating ultrasonic signal for example, HIFU
- a temperature estimation device is a temperature estimation device that estimates a temperature of a target region using an ultrasonic signal, and receives a scan signal obtained by scanning the target region with an ultrasonic signal. And an echo shift calculation unit that calculates an echo shift that is a change amount that varies depending on the temperature of the target region based on the scan signal, and the time required for the ultrasonic signal to pass through the target region; Based on the calculated echo shift, a strain calculation unit that calculates a strain that is a change rate in which the moving distance when the ultrasonic signal passes through the target region apparently changes depending on the temperature of the target region; A strain rate calculation unit that calculates a strain rate, which is a temporal change rate of the strain, based on the calculated strain; Using the relationship between the strain and the strain rate and temperature, corresponding to the calculated strain and strain rate and a temperature estimation unit that estimates a temperature of the target area.
- the temperature can be estimated with high accuracy, and the temperature can be estimated in a wide temperature range.
- a program is a program for estimating a temperature of a target region using an ultrasonic signal, and receives a scan signal obtained by scanning the target region with an ultrasonic signal, Based on the scan signal, an echo shift calculating step for calculating an echo shift, which is a change amount that varies depending on the temperature of the target region, the time required for the ultrasonic signal to pass through the target region is calculated.
- a strain calculating step for calculating a strain, which is a change rate in which the moving distance when the ultrasonic signal passes through the target region apparently changes depending on the temperature of the target region, based on the echo shift, The strain rate calculation step is used to calculate the strain rate, which is the rate of change of the strain over time, based on the strain.
- flop using a relationship between the predetermined strain and strain rate and temperature, to perform a temperature estimation step of estimating the temperature of the target region corresponding to the calculated strain and strain rate, to the computer.
- the temperature can be estimated with high accuracy, and the temperature can be estimated in a wide temperature range.
- FIG. 1 is a block diagram showing a configuration of a temperature estimation apparatus according to Embodiment 1 of the present invention.
- the temperature estimation apparatus 10 according to the present embodiment includes a main body 101 and an ultrasonic transducer 102.
- the ultrasonic transducer 102 transmits an ultrasonic signal to a target region 51 (for example, a treatment target site in HIFU treatment) inside the living body 50, and the target region 51 is scanned and reflected by the target region 51. Receive an ultrasonic signal.
- a target region 51 for example, a treatment target site in HIFU treatment
- the main body unit 101 includes a transmission unit 103, a reception unit 104, a signal processing unit 105, a display unit 106, and a control unit 107.
- the transmission unit 103 generates an ultrasonic signal in the ultrasonic transducer 102 by supplying an electrical signal (transmission signal) to the ultrasonic transducer 102 according to the control of the control unit 107.
- the receiving unit 104 receives an electrical signal (received signal) from the ultrasonic transducer 102 under the control of the control unit 107.
- the signal processing unit 105 estimates the temperature of the target region 51 by processing the electrical signal (scan signal) supplied from the receiving unit 104. A temperature estimation method by the signal processing unit 105 will be described later.
- the display unit 106 displays the temperature estimated by the signal processing unit 105 under the control of the control unit 107.
- the display unit 106 is configured by, for example, a liquid crystal display.
- the control unit 107 controls the temperature estimation apparatus 10 by controlling the transmission unit 103, the reception unit 104, the signal processing unit 105, and the display unit 106, respectively.
- the control unit 107 is composed of, for example, a microprocessor.
- FIG. 2 is a diagram for explaining the scan signal.
- the scan signal has three dimensions: depth direction (d), line direction (l), and frame direction (n). ing.
- the depth direction is a direction from the body surface of the living body 50 toward the inside of the living body 50
- the line direction is a direction substantially perpendicular to the depth direction.
- the frame direction is a time direction in which the frames are switched. In general, the time in the depth direction is referred to as a fast time, and the time in the frame direction is referred to as a slow time.
- the speed of the ultrasonic signal that is, the speed of sound changes.
- the time required for the ultrasonic signal to pass through the target region 51 changes.
- the amount of change in which the time required for the ultrasonic signal to pass through the target region 51 varies depending on the temperature of the target region 51 is referred to as echo shift.
- the time shift generated between the RF signal (scan signal) in frame 1 and the RF signal in frame 2 that is the next frame of frame 1 is an echo shift.
- the ultrasonic signal travels along the depth direction from the body surface of the living body 50 toward the inside thereof.
- the distance (depth) from the body surface of the living body 50 to the first part 51a of the target area 51 is d 1
- the distance from the body surface of the living body 50 to the second part 51b of the target area 51 is d 2
- the sound speed when the temperature of the target region 51 is T 0 ° C. is c 0 .
- the time (fast time) t f0 required for the ultrasonic signal to pass through the target region 51 is: It is.
- the strain ⁇ which is a change rate at which the moving distance when the ultrasonic signal passes through the target region 51 apparently changes depending on the temperature of the target region 51, is: It is represented by In equation 5, since c system is a constant, the strain ⁇ is It is represented by
- the speed of sound c 1 and the temperature T are the following second order polynomials: It is known to satisfy.
- Each of a 1 , a 2 and a 3 is a constant temperature coefficient.
- the amount of change of speed of sound varies depending on the temperature of the target region 51, it is known that sufficiently smaller than the speed of sound c 0. That is, It is.
- Equation 5 and Equation 7 Is obtained.
- Equation 9 a 4 , a 5 and a 6 are respectively It is a constant.
- the model formula of Formula 9 is the same as the model formula used in the conventional temperature estimation method 1 described above.
- the temperature of the target region 51 is estimated using the model formula (16) (described later) derived by combining the model formula (9) and the Pennes bioheat transfer equation.
- the Pennes bio-heat transfer equation is a differential equation representing heat conduction inside the living body, It is represented by In Equation 11, Q met : metabolic fever, ⁇ T: environmental temperature rise, ⁇ : tissue density, ⁇ : tissue specific heat, ⁇ b : blood density, ⁇ b : blood specific heat, ⁇ : blood perfusion ratio, ⁇ : Tissue thermal conductivity.
- Equation 11 is It can be rewritten as In Equation 12, a 7 and a 8 are respectively It is a constant that satisfies
- the strain rate is obtained by calculating the partial derivatives for both sides of the above equation (9).
- ⁇ is the strain rate.
- the strain rate ⁇ is a temporal change rate of the strain ⁇ .
- the strain rate ⁇ is a mixed partial derivative of the echo shift ⁇ along the depth d and time (slow time) n, It is.
- Equation 9 Combining Equation 9 and Equation 15 to eliminate the second order term (T 2 ), Is obtained.
- Equation 16 a 12 , a 13 and a 14 are respectively It is a constant that satisfies
- the model formula of Formula 16 is a linear model formula indicating the relationship among a predetermined strain ⁇ , strain rate ⁇ , and temperature T.
- the temperature of the target region 51 is estimated using this model formula as described later.
- FIG. 3 is a block diagram specifically illustrating the configuration of the signal processing unit of FIG.
- the signal processing unit 105 includes a preprocessing unit 201, an echo shift calculation unit 202, a strain calculation unit 203, a strain rate calculation unit 204, and a temperature estimation unit 205.
- FIG. 4 is a block diagram specifically showing the configuration of the preprocessing unit.
- the preprocessing unit 201 includes a damaged frame removal unit 301 and a noise filter 302.
- the damaged frame removal unit 301 removes a damaged frame generated in the scan signal due to disturbance (for example, environmental noise, an external processing signal, and a highly focused ultrasonic wave used in HIFU treatment) from the scan signal (preprocessing step).
- disturbance for example, environmental noise, an external processing signal, and a highly focused ultrasonic wave used in HIFU treatment
- scan signals (d, l, n) and the like in FIG. 3 and subsequent figures, d represents a dimension in the depth direction, l represents a dimension in the line direction, and n represents a dimension in the frame direction.
- FIG. 5 is a diagram showing a damaged frame generated in the scan signal. As shown in FIG. 5, in the damaged frame, the amplitude of the intensity of the scan signal (RF signal) becomes abnormally large.
- the damaged frame removing unit 301 After detecting the upper envelope and the lower envelope in the scan signal intensity graph, the damaged frame removing unit 301 calculates the difference between the upper envelope and the lower envelope by calculation for each frame. . Thereafter, the damaged frame removing unit 301 determines that a frame in which the difference between the two envelopes is equal to or greater than a predetermined threshold is the above-described damaged frame, and removes the damaged frame from the scan signal. Note that the frame in which the difference between the two envelopes is equal to or greater than the predetermined threshold corresponds to a heating stage in which highly focused ultrasound is irradiated in, for example, HIFU treatment.
- a frame in which the difference between the two envelopes is smaller than the predetermined threshold corresponds to a cooling stage after irradiation with high-focus ultrasound, for example, in HIFU treatment. Accordingly, the scan signal frame in the cooling phase of the HIFU treatment is used for temperature estimation in a temperature estimation unit 205 described later, and the scan signal frame in the heating phase of the HIFU treatment (that is, a damaged frame) is used in the temperature estimation unit. It is not used for temperature estimation at 205.
- the scan signal output from the damaged frame removing unit 301 is output as a filtering signal (ie, a filtered scan signal) from the noise filter 302 after the noise is attenuated in the noise filter 302.
- a filtering signal ie, a filtered scan signal
- the pre-processing unit 201 can also perform processing in consideration of compensation for body movement and blood flow.
- the movement of the body is detected by using an ultrasonic signal (or image) in the motion estimation technique, or by using an acceleration sensor or the like.
- Blood flow is detected by using ultrasonic Doppler signal processing.
- FIG. 6 is a block diagram specifically showing the configuration of the echo shift calculation unit.
- the echo shift calculation unit 202 includes an echo shift calculation unit 303, an abnormal value correction unit 304, and an echo shift noise filter 305.
- the echo shift calculation unit 202 calculates an echo shift based on the filtering signal (scan signal) (echo shift calculation step).
- the echo shift calculation unit 303 calculates a raw echo shift based on the filtering signal output from the preprocessing unit 201 (echo shift calculation step).
- Methods for calculating the raw echo shift include, for example, autocorrelation methods and cross-correlation methods.
- the SDopp estimation method In the autocorrelation method, for example, the SDopp estimation method is used.
- ⁇ (d, n) is an echo shift at depth d th and time (slow time) n th .
- k is the number of samples in the depth direction for which the echo shift is calculated
- y is the number of frames for which the echo shift is calculated.
- I (d, n) is an IQ segment selected from the depth d th and the time (slow time) n th .
- the size of the (k * y) window may be a constant value, or may be variable according to a change in the characteristics of the scan signal (for example, a change in amplitude or energy).
- the cross-correlation method is expressed mathematically by the following equation 18, for example.
- Equation 18 S n is an RF segment in frame n, and S n + 1 is an RF segment in frame n + 1 adjacent to frame n.
- S n mean and S n RMS are the average and root mean square of the segments, respectively.
- k is the length of the segment window
- q is the search range in the RF line of the frame
- ⁇ is the cross-correlation coefficient.
- ⁇ is equal to the echo shift between the two segments when ⁇ ( ⁇ ) is the maximum value.
- FIG. 7 is a diagram for explaining an echo shift calculation step.
- the echo shift calculation section 303 first, in a state of being displaced to the upper end of the search range q in the frame n + 1 window (S n + 1), the segments S n to the window (S n + 1 ) Multiply. This calculation step is performed for each data point, and the total value is stored as a variable. Thereafter, the echo shift calculation section 303, until the window (S n + 1) reaches the lower end of the search range q, while displacing the window (S n + 1) for each sample to repeat the calculation described above.
- the echo shift calculation unit 303 determines ⁇ when ⁇ ( ⁇ ) reaches the maximum value as a raw echo shift.
- the abnormal value correcting unit 304 corrects an abnormal value that is not caused by a temperature change in the raw echo shift calculated by the echo shift calculating unit 303 (abnormal value correcting step).
- the raw echo shift includes an echo shift caused by a temperature change and an abnormal value not caused by the temperature change (eg, caused by vibration). This outlier significantly reduces the accuracy of temperature estimation. By correcting this abnormal value, an echo shift due to a temperature change can be obtained.
- the abnormal value correcting unit 304 removes abnormal values based on, for example, an echo shift prediction model. This echo shift prediction model is composed of an error function or a complementary error function.
- FIG. 8 is a diagram for explaining the abnormal value correcting step.
- parameters of an echo shift prediction model for calculating a predicted echo shift are adjusted based on the raw echo shift calculated in the echo shift calculation step (parameter adjustment step).
- a predicted echo shift is calculated based on the optimized echo shift prediction model (predicted echo shift calculation step).
- the upper threshold value and the lower threshold value are set based on the predicted echo shift and the RF signal obtained by scanning the target region 51 (threshold setting step).
- this threshold value setting step an interval between the upper threshold value and the lower threshold value is set based on a preliminary experiment or the like (interval setting step), and the intensity of the RF signal is used as a weight, whereby the upper threshold value is set. And the lower threshold is adjusted (threshold adjustment step). After that, among the plurality of data points of the raw echo shift, the data point that is an abnormal value exceeding the upper threshold value and the lower threshold value is corrected to the corresponding data point of the predicted echo shift (data point correction step). .
- the echo shift noise filter 305 attenuates noise included in the echo shift by increasing the SN ratio of the echo shift caused by temperature change (noise attenuation step).
- the echo shift noise filter 305 is composed of, for example, a low pass filter or a band pass filter.
- the echo shift whose noise is reduced by the echo shift noise filter 305 is output from the echo shift noise filter 305.
- FIG. 9 is a block diagram specifically showing the configuration of the strain calculation unit.
- the strain calculation unit 203 includes a strain calculation unit 306 and a strain noise filter 307.
- the strain calculation unit 306 calculates the partial derivative of the echo shift ⁇ along the depth d, that is, the strain ⁇ , as shown in Equation 6 (strain calculation step).
- the strain calculation unit 306 calculates the strain using, for example, a weighted least square algorithm.
- the weighted least squares algorithm is a least squares method by leading the weight associated with each data point to a suitable criterion.
- the strain calculation unit 306 calculates a strain using an echo shift from three or three or more samples using a weighted least square algorithm. This adjusts the parameters of the linear function to match the set data, i.e. minimizes the mean square error between the model and the data.
- the strain ⁇ is Determined by. In Equation 19, N is the number of samples, ⁇ is the echo shift at the sample point, and d is the depth index of the sample point.
- each echo shift sample is weighted at a rate of RF point intensity.
- a sample point can be emphasized with a higher S / N ratio. Therefore, the strain ⁇ in Equation 19 is As amended.
- I is the RF point intensity for calculating the displacement of the sample.
- the strain noise filter 307 attenuates noise generated in the strain due to a small environmental disturbance.
- the strain noise filter 307 is, for example, a two-dimensional median filter along the depth and time.
- the strain whose noise is reduced by the strain noise filter 307 is output from the strain noise filter 307.
- FIG. 10 is a block diagram specifically showing the configuration of the strain rate calculation unit.
- the strain rate calculation unit 204 includes a strain rate calculation unit 308 and a strain rate noise filter 309.
- the strain rate calculation unit 204 calculates a strain rate based on the calculated strain (strain rate calculation step).
- the strain rate ⁇ is a mixed partial derivative of the echo shift ⁇ along the depth d and time (slow time) n (see Equation 14).
- the strain rate calculation unit 308 calculates the strain rate indirectly or directly from the echo shift.
- Indirect strain rate calculation methods include, for example, strain based on strain (partial derivative of echo shift along depth) or speed (partial derivative of echo shift along time (slow time)). There is a method for calculating the rate, but it is not limited to this.
- the echo shift ⁇ has depth d and time (slow time) n as independent variables. It is represented by
- Another example of the method for directly calculating the strain rate is a least squares method.
- the echo shift is assumed to match the following curve:
- Equation 24 Is the value of the echo shift matched at the point (d i , n j ).
- strain rate ⁇ is Is defined as
- Equation 24 a linear model equation for predicting echo shift based on the product and depth of depth and time (slow time) is obtained.
- This linear model formula is It is represented by For a set of data (d 1 , n 1 , ⁇ 1,1 ), (d 1 , n 2 , ⁇ 1 , 2 ),... (D n , n m , ⁇ n, m ), As described above, the value of ⁇ is determined such that the error between the echo shift ⁇ i, j calculated based on the scan signal and the echo shift predicted based on the linear model equation of Equation 26 is minimized.
- Equation 27 k and y are the number of samples and the number of frames in the depth direction where the strain rate is calculated and predicted, respectively. All d i, n i and ⁇ i, j are known, while ⁇ , b and ⁇ are unknown coefficients. In order to obtain the least square error, first derivatives are generated for the unknown coefficients ⁇ , b and ⁇ .
- the value of the strain rate ⁇ can be obtained by solving Equation 28.
- the strain rate noise filter 309 attenuates noise generated in the strain rate.
- the strain rate whose noise is reduced by the strain rate noise filter 309 is output from the strain rate noise filter 309.
- FIG. 11 is a block diagram specifically showing the configuration of the temperature estimation unit.
- the temperature estimation unit 205 includes a parameter calculation unit 310 and a temperature calculation unit 311.
- the temperature estimation unit 205 estimates the temperature based on the calculated strain and strain rate (temperature estimation step).
- the parameter calculation unit 310 calculates algorithm parameters a 12 , a 13, and a 14 of the linear model expression of Expression 16 based on the calculated strain and strain rate. These algorithm parameters are identified by performing the following steps:
- thermocouple (not shown) is aligned with the target region 51 to be heated (alignment step). Then, the temperature of the object area
- first derivatives are generated for the unknown coefficients a 12 , a 13 and a 14 .
- the temperature calculation unit 311 estimates the temperature by applying the calculated algorithm parameter to Equation 16 and calculating the temperature based on the calculated strain and strain rate.
- the alignment step described above it is necessary to accurately align the position of the thermocouple with respect to the target region 51 to be heated in order to cover the entire range of temperature change.
- the position of the thermocouple is aligned with the target region 51 to be heated by the B-mode image. Thereafter, in order to change the temperature of the target region 51, a heating source (not shown) that outputs an ultrasonic signal is operated, and the temperature of the target region 51 is measured by a thermocouple while the heating source is displaced in the space. To do. Thereafter, when the temperature measured by the thermocouple becomes minimum, the displacement of the heating source is stopped. In this way, the relative positional relationship between the thermocouple and the heating source is determined.
- FIG. 12 is a flowchart showing a flow of temperature estimation by the temperature estimation method according to Embodiment 1 of the present invention.
- FIG. 13 is a diagram for explaining the temperature estimation step.
- a scan signal obtained by scanning the target area 51 with an ultrasonic signal is received, and a damaged frame generated in the scan signal due to disturbance is removed (pre-processing step) (S11). Then, an echo shift is calculated based on the scan signal from which the damaged frame is removed (echo shift calculation step) (S12). Thereafter, a strain is calculated based on the calculated echo shift (strain calculation step) (S13), and a strain rate is calculated based on the calculated strain (strain rate calculation step) (S14). Then, as shown in FIG. 13, based on the calculated strain and strain rate, the temperature of the target region 51 is estimated using the linear model equation of Equation 16 (temperature estimation step) (S15).
- FIG. 14 is a diagram showing experimental results comparing the temperature estimation method of the present invention and the conventional temperature estimation method.
- the solid line graph indicates the time change of the temperature estimated by the temperature estimation method of the first embodiment
- the alternate long and short dash line graph indicates the time change of the temperature estimated by the conventional temperature estimation method 1 described above. Is shown.
- the broken line graph shows the time variation of the recorded actual temperature.
- the temperature estimated by the temperature estimation method of the first embodiment has a smaller error from the actual temperature than the temperature estimated by the conventional temperature estimation method 1. From this experimental result, it can be understood that the temperature estimation method of the present embodiment can estimate the temperature with high accuracy.
- FIG. 15 is a diagram showing experimental results comparing the temperature estimation method of the present invention and the conventional temperature estimation method.
- the upper graph is a result of performing nine experiments for obtaining an error (specifically, root mean square error) between the temperature estimated by the conventional temperature estimation method 1 and the recorded actual temperature. Is shown.
- the lower graph shows the result of nine experiments for obtaining an error between the temperature estimated by the temperature estimation method of the first embodiment and the recorded actual temperature.
- the standard deviation of the temperature estimated by the temperature estimation method of the first embodiment is smaller than the standard deviation of the temperature estimated by the conventional temperature estimation method 1. Also from this experimental result, it can be understood that the temperature estimation method of the present embodiment can estimate the temperature with high accuracy.
- FIG. 16 is a block diagram showing the configuration of the temperature estimation apparatus according to Embodiment 2 of the present invention.
- the signal processing unit 105A further includes a memory 321 and a temperature correction unit 322.
- the memory 321 stores the temperature of one frame (or a plurality of frames) estimated by the temperature estimation unit 205.
- the temperature correction unit 322 corrects the temperature of one frame (or a plurality of frames) stored in the memory 321 based on the objective function f 1 considering the spatial continuity of temperature (temperature correction step).
- the temperature correction step is executed after the above-described temperature estimation step.
- the objective function f 1 described above is It is represented by In Equation 31, Is a temperature corrected by the temperature correction unit 322, and T d, l is a temperature estimated by the temperature estimation unit 205.
- ⁇ 1 and g are weighting functions, respectively. Note that the weighting function g is configured with a Huber function, for example.
- d represents a spatial position in the depth direction
- l represents a spatial position in the line direction.
- the first term is a term for bringing the temperature correction value closer to the estimated temperature value
- the second term is a term for spatially differentiating the estimated temperature value.
- the temperature correction unit 322 obtains a temperature correction value that minimizes the objective function f 1 of Equation 31, for example, by performing numerical calculation such as a conjugate gradient method. Thereby, the temperature estimated by the temperature estimation unit 205 can be corrected to a temperature in which spatial continuity is considered.
- FIG. 17 is a block diagram showing a configuration of a temperature estimation apparatus according to Embodiment 3 of the present invention.
- the signal processing unit 105B includes a temperature correction unit 323 instead of the temperature correction unit 322 of the second embodiment.
- the temperature correction unit 323 is for one frame (or for a plurality of frames) accumulated in the memory 321 based on the objective function f 2 considering the distance between the heat source position heated by the ultrasonic signal and the target region 51. Is corrected (temperature correction step).
- the temperature correction step is executed after the above-described temperature estimation step.
- Equation 32 The objective function f 2 described above is It is represented by In Equation 32, ⁇ 2 and ⁇ are weighting functions, respectively.
- the first term is a term for bringing the temperature correction value closer to the estimated temperature value
- the second term is to obtain the temperature and correction value at the heat source position (d 0 , l 0 ). This is the difference from the temperature at the position (d, l)
- the third term is a term that is inversely proportional to the cube of the distance from the heat source position.
- Temperature correction unit 323 for example, by performing the numerical calculation, such as the conjugate gradient method, to obtain a correction value of the temperature such that the objective function f 2 of the formula 32 to a minimum.
- the temperature estimated by the temperature estimation unit 205 can be corrected to a temperature that takes into account the distance between the heat source position and the target region.
- each component may be configured by dedicated hardware or may be realized by executing a software program suitable for each component.
- Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.
- the software that realizes the temperature estimation method and the like of each of the above embodiments is the following program.
- this program receives a scan signal obtained by scanning the target area with an ultrasonic signal, and based on the scan signal, the time required for the ultrasonic signal to pass through the target area is the target.
- An echo shift calculation step for calculating an echo shift that is a change amount that changes depending on the temperature of the region, and a moving distance when the ultrasonic signal passes through the target region based on the calculated echo shift is the target.
- the above program can be read by a computer in a nonvolatile recording medium such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, BD (Blu-ray Disc (registered trademark)) and What was recorded on the semiconductor memory etc. may be used.
- a nonvolatile recording medium such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, BD (Blu-ray Disc (registered trademark)) and What was recorded on the semiconductor memory etc.
- the temperature estimation method, the temperature estimation device, and the program according to one or more aspects of the present invention have been described in the first to third embodiments.
- the present invention is limited to the first to third embodiments. It is not a thing.
- various modifications conceivable by those skilled in the art are applied to the first to third embodiments, and a form constructed by combining components in different embodiments is also one of the present invention. It may be included within the scope of multiple embodiments.
- the present invention can be applied as a temperature estimation method, a temperature estimation device, and a program capable of estimating temperature with high accuracy and estimating temperature in a wide temperature range.
- Temperature estimation apparatus 50 Living body 51 Target area 101 Main body part 102 Ultrasonic vibrator 103 Transmission part 104 Reception part 105,105A, 105B Signal processing part 106 Display part 107 Control part 201 Preprocessing part 202 Echo shift calculation part 203 Strain calculation part 204 Strain rate calculation unit 205 Temperature estimation unit 301 Damaged frame removal unit 302 Noise filter 303 Echo shift calculation unit 304 Abnormal value correction unit 305 Echo shift noise filter 306 Strain calculation unit 307 Strain noise filter 308 Strain rate calculation unit 309 Strain rate noise filter 310 Parameter Calculation Unit 311 Temperature Calculation Unit 321 Memory 322, 323 Temperature Correction Unit
Abstract
Description
まず、本発明の実施の形態を説明する前に、本発明者が見出した、従来の温度推定方法において生じる不具合について説明する。
図18は、従来の温度推定方法における、モデル化された温度とストレインとの関係を示す図である。従来の温度推定方法1では、超音波信号の速度が温度に依存して変化することを利用して、治療対象部位等の温度を推定する。例えば、治療対象部位に加熱用の超音波信号を集束させてHIFU治療を行う前後において、治療対象部位の温度が変化することに伴って、温度推定用の超音波信号の速度が変化する。このように超音波信号の速度が変化することにより、超音波信号が治療対象部位を通過する際の移動距離が見かけ上変化する。この移動距離の変化割合をストレイン(strain)という。
従来の温度推定方法2では、上述と同様に、例えばHIFU治療前における超音波信号とHIFU治療中における超音波信号との差に基づいてストレインを計算により求めた後に、温度とストレインとの関係を示すモデル式に基づいて温度を推定する。図18中の破線のグラフ403で示すように、このモデル式は、1次関数で近似されている。
従来の温度推定方法3では、モデル式として生体伝熱方程式(Bio-Heat Transfer Equation)が用いられる。まず、モデル式のパラメータをキャリブレーション時に求め、さらに、温度とストレインとの関係を示す関係式を求めておく。例えば、HIFU治療時には、モデル式に基づいて治療対象部位の温度を推定する。その後、推定した温度からストレインを上記関係式に基づいて計算により求め、計算により求めたストレインとRF(Radio Frequency)信号から得られたストレインとの誤差が小さくなるように、モデル式のパラメータを逐次修正する。
以下、本発明の実施の形態について、図面を用いて詳細に説明する。なお、以下で説明する実施の形態は、いずれも本発明の一具体例を示すものである。以下の実施の形態で示される数値、形状、材料、構成要素、構成要素の配置位置、ステップ及びステップの順序等は、一例であり、本発明を限定する主旨ではない。また、以下の実施の形態における構成要素のうち、最上位概念を示す独立請求項に記載されていない構成要素については、任意の構成要素として説明される。
(温度推定装置の全体構成)
図1は、本発明の実施の形態1に係る温度推定装置の構成を示すブロック図である。図1に示すように、本実施の形態の温度推定装置10は、本体部101及び超音波振動子102を備えている。
図2は、スキャン信号を説明するための図である。図2に示すように、スキャン信号は、3つの次元、即ち、深さ方向(depth direction)(d)、ライン方向(line direction)(l)及びフレーム方向(frame direction)(n)を有している。深さ方向は、生体50の体表から生体50の内部に向かう方向であり、ライン方向は、深さ方向に対して略垂直な方向である。フレーム方向は、フレームが切り替わる時間方向である。一般に、深さ方向における時間をファストタイム(fast time)、フレーム方向における時間をスロータイム(slow time)という。
図3は、図1の信号処理部の構成を具体的に示すブロック図である。図3に示すように、信号処理部105は、前処理部201、エコーシフト算出部202、ストレイン算出部203、ストレインレート算出部204及び温度推定部205を有している。
図12は、本発明の実施の形態1に係る温度推定方法による温度の推定の流れを示すフローチャートである。図13は、温度推定ステップを説明するための図である。
図16は、本発明の実施の形態2に係る温度推定装置の構成を示すブロック図である。本実施の形態の温度推定装置では、信号処理部105Aは、さらに、メモリ321及び温度補正部322を有している。メモリ321には、温度推定部205により推定された1フレーム分(又は複数フレーム分)の温度が蓄積されている。温度補正部322は、温度の空間的な連続性を考慮した目的関数f1に基づいて、メモリ321に蓄積された1フレーム分(又は複数フレーム分)の温度を補正する(温度補正ステップ)。なお、温度補正ステップは、上述した温度推定ステップの後に実行される。
図17は、本発明の実施の形態3に係る温度推定装置の構成を示すブロック図である。本実施の形態の温度推定装置では、信号処理部105Bは、上記実施の形態2の温度補正部322に代えて、温度補正部323を有している。温度補正部323は、超音波信号により加熱された熱源位置と対象領域51との間の距離を考慮した目的関数f2に基づいて、メモリ321に蓄積された1フレーム分(又は複数フレーム分)の温度を補正する(温度補正ステップ)。なお、温度補正ステップは、上述した温度推定ステップの後に実行される。
50 生体
51 対象領域
101 本体部
102 超音波振動子
103 送信部
104 受信部
105,105A,105B 信号処理部
106 表示部
107 制御部
201 前処理部
202 エコーシフト算出部
203 ストレイン算出部
204 ストレインレート算出部
205 温度推定部
301 破損フレーム除去部
302 ノイズフィルタ
303 エコーシフト計算部
304 異常値修正部
305 エコーシフトノイズフィルタ
306 ストレイン計算部
307 ストレインノイズフィルタ
308 ストレインレート計算部
309 ストレインレートノイズフィルタ
310 パラメータ計算部
311 温度計算部
321 メモリ
322,323 温度補正部
Claims (15)
- 超音波信号を用いて対象領域の温度を推定する温度推定方法であって、
超音波信号によって前記対象領域をスキャンすることにより得られるスキャン信号を受信し、前記スキャン信号に基づいて、超音波信号が前記対象領域を通過するのに要する時間が前記対象領域の温度に依存して変化する変化量であるエコーシフトを算出するエコーシフト算出ステップと、
算出されたエコーシフトに基づいて、超音波信号が前記対象領域を通過する際の移動距離が前記対象領域の温度に依存して見かけ上変化する変化割合であるストレインを算出するストレイン算出ステップと、
算出されたストレインに基づいて、ストレインの時間的な変化割合であるストレインレートを算出するストレインレート算出ステップと、
予め定められたストレインとストレインレートと温度との関係を用いて、算出されたストレイン及びストレインレートに対応する前記対象領域の温度を推定する温度推定ステップと、を含む
温度推定方法。 - 前記温度推定ステップにおいては、ストレインとストレインレートと温度との関係を示す線形モデル式を用いて、算出されたストレイン及びストレインレートに対応する前記対象領域の温度を推定する
請求項1に記載の温度推定方法。 - さらに、外乱によって前記スキャン信号に生じた破損フレームを除去する前処理ステップを含み、
前記エコーシフト算出ステップでは、前記前処理ステップにおいて破損フレームが除去されたスキャン信号に基づいて、エコーシフトを算出する
請求項1又は2に記載の温度推定方法。 - 前記エコーシフト算出ステップは、
受信された前記スキャン信号に基づいて生のエコーシフトを計算するエコーシフト計算ステップと、
計算された前記生のエコーシフトにおいて温度変化に起因しない異常値を修正することにより、温度変化に起因するエコーシフトを得る異常値修正ステップと、
前記温度変化に起因するエコーシフトに含まれるノイズをノイズフィルタにより減衰させるノイズ減衰ステップと、を含む
請求項1~3のいずれか1項に記載の温度推定方法。 - 前記異常値修正ステップは、
前記エコーシフト計算ステップにおいて計算された前記生のエコーシフトに基づいて、予測エコーシフトを計算するためのエコーシフト予測モデルのパラメータを調整するパラメータ調整ステップと、
最適化された前記エコーシフト予測モデルに基づいて、前記予測エコーシフトを計算する予測エコーシフト計算ステップと、
前記予測エコーシフト及び前記対象領域をスキャンすることにより得られるRF信号に基づいて、閾値を設定する閾値設定ステップと、
前記生のエコーシフトの複数のデータポイントのうち、前記閾値を超えた前記異常値であるデータポイントを、前記予測エコーシフトの対応するデータポイントに基づいて修正するデータポイント修正ステップと、を含む
請求項4に記載の温度推定方法。 - 前記エコーシフト予測モデルは、誤差関数又は相補誤差関数である
請求項5に記載の温度推定方法。 - 前記閾値設定ステップは、
前記閾値としての上側の閾値と下側の閾値との間の間隔を設定する間隔設定ステップと、
前記RF信号の強度を重みとして用いることにより、前記上側の閾値及び前記下側の閾値を調節する閾値調節ステップと、を含む
請求項5又は6に記載の温度推定方法。 - 前記ストレインレート算出ステップにおいては、
深さ及び時間の積と深さとに基づいてエコーシフトを予測するためのモデル式を用いて、前記スキャン信号に基づいて算出されたエコーシフトと前記モデル式に基づいて予測されたエコーシフトとの誤差が最小となるように、ストレインレートを算出する
請求項1~7のいずれか1項に記載の温度推定方法。 - 前記ストレインレート算出ステップにおいて用いられる前記モデル式は、線形モデル式である
請求項8に記載の温度推定方法。 - 前記温度推定ステップにおいて用いられる前記線形モデル式のアルゴリズムパラメータは、
加熱すべき前記対象領域に対して熱電対の位置を位置合わせする位置合わせステップと、
前記熱電対によって前記対象領域の温度を測定する温度測定ステップと、
前記対象領域をスキャンすることにより得られる前記スキャン信号に基づいて、前記対象領域の推定温度を導出する推定温度導出ステップと、
前記温度測定ステップにおいて測定された温度と前記推定温度導出ステップにおいて導出された推定温度との誤差が最小となるように、前記アルゴリズムパラメータを同定するアルゴリズムパラメータ同定ステップと、を実行することにより同定される
請求項2に記載の温度推定方法。 - 前記位置合わせステップは、
Bモード画像によって、加熱すべき前記対象領域に対して前記熱電対の位置を位置合わせするステップと、
前記対象領域の温度を変化させるために、超音波信号を出力する加熱源を作動させるステップと、
前記加熱源を空間内で変位させながら、前記熱電対によって前記対象領域の温度を測定するステップと、
前記熱電対により測定された温度が最小となったときに前記加熱源の変位を停止させるステップと、を含む
請求項10に記載の温度推定方法。 - さらに、温度の空間的な連続性を考慮した目的関数に基づいて、前記温度推定ステップにより推定された温度を補正する温度補正ステップを含む
請求項1~11のいずれか1項に記載の温度推定方法。 - さらに、加熱用の超音波信号により加熱された熱源位置と前記対象領域との間の距離を考慮した目的関数に基づいて、前記温度推定ステップにより推定された温度を補正する温度補正ステップを含む
請求項1~11のいずれか1項に記載の温度推定方法。 - 超音波信号を用いて対象領域の温度を推定する温度推定装置であって、
超音波信号によって前記対象領域をスキャンすることにより得られるスキャン信号を受信し、前記スキャン信号に基づいて、超音波信号が前記対象領域を通過するのに要する時間が前記対象領域の温度に依存して変化する変化量であるエコーシフトを算出するエコーシフト算出部と、
算出されたエコーシフトに基づいて、超音波信号が前記対象領域を通過する際の移動距離が前記対象領域の温度に依存して見かけ上変化する変化割合であるストレインを算出するストレイン算出部と、
算出されたストレインに基づいて、ストレインの時間的な変化割合であるストレインレートを算出するストレインレート算出部と、
予め定められたストレインとストレインレートと温度との関係を用いて、算出されたストレイン及びストレインレートに対応する前記対象領域の温度を推定する温度推定部と、を備える
温度推定装置。 - 超音波信号を用いて対象領域の温度を推定するためのプログラムであって、
超音波信号によって前記対象領域をスキャンすることにより得られるスキャン信号を受信し、前記スキャン信号に基づいて、超音波信号が前記対象領域を通過するのに要する時間が前記対象領域の温度に依存して変化する変化量であるエコーシフトを算出するエコーシフト算出ステップと、
算出されたエコーシフトに基づいて、超音波信号が前記対象領域を通過する際の移動距離が前記対象領域の温度に依存して見かけ上変化する変化割合であるストレインを算出するストレイン算出ステップと、
算出されたストレインに基づいて、ストレインの時間的な変化割合であるストレインレートを算出するストレインレート算出ステップと、
予め定められたストレインとストレインレートと温度との関係を用いて、算出されたストレイン及びストレインレートに対応する前記対象領域の温度を推定する温度推定ステップと、をコンピュータに実行させる
プログラム。
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CN106264607A (zh) * | 2016-09-18 | 2017-01-04 | 天津大学 | 基于时间信号偏移的实时超声波温度成像方法及设备 |
JP2018501875A (ja) * | 2014-12-30 | 2018-01-25 | コーニンクレッカ フィリップス エヌ ヴェKoninklijke Philips N.V. | 患者特有超音波熱歪温度較正 |
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KR20130051241A (ko) * | 2011-11-09 | 2013-05-20 | 삼성전자주식회사 | 진단영상을 생성하는 방법, 이를 수행하는 장치 및 의료영상시스템 |
KR20130075533A (ko) * | 2011-12-27 | 2013-07-05 | 삼성전자주식회사 | 온도 추정 방법 및 이를 이용한 온도 추정 장치 |
CN106999159B (zh) * | 2014-11-18 | 2020-08-14 | 皇家飞利浦有限公司 | 用于将组织性质可视化的装置 |
CN109975477A (zh) * | 2017-12-27 | 2019-07-05 | 科仕环境控制设备(上海)有限公司 | 一种窄带物联网空气质量传感器装置及处理方法 |
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