WO2014003133A1 - 生体計測装置の計測データ選択方法、生体計測装置の光出射位置決定方法、および生体計測装置 - Google Patents
生体計測装置の計測データ選択方法、生体計測装置の光出射位置決定方法、および生体計測装置 Download PDFInfo
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V20/00—Scenes; Scene-specific elements
- G06V20/60—Type of objects
- G06V20/69—Microscopic objects, e.g. biological cells or cellular parts
- G06V20/695—Preprocessing, e.g. image segmentation
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- 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
- A61B5/0073—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence by tomography, i.e. reconstruction of 3D images from 2D projections
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/70—Determining position or orientation of objects or cameras
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B2576/00—Medical imaging apparatus involving image processing or analysis
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/10—Image acquisition modality
- G06T2207/10072—Tomographic images
- G06T2207/10101—Optical tomography; Optical coherence tomography [OCT]
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- 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
- G16H30/00—ICT specially adapted for the handling or processing of medical images
- G16H30/40—ICT specially adapted for the handling or processing of medical images for processing medical images, e.g. editing
Definitions
- the present invention relates to a measurement data selection method for a biological measurement device, a light emission position determination method for the biological measurement device, and a biological measurement device.
- Non-Patent Document 1 describes a method of performing three-dimensional optical imaging of a living body using a multi-channel time-resolved spectroscopic measurement apparatus.
- calculation (image reconstruction) for creating image data in diffuse optical tomography is formulated by a linear equation such as the following equation (1).
- the vector x is an n-dimensional vector (n is the number of pixels) representing image data.
- the vector y is an m-dimensional vector (m is the number of data) representing measurement data.
- the matrix A is an m-by-n system matrix relating vectors x and y.
- Image reconstruction in diffuse optical tomography means that the vector x is calculated backward from the equation (1).
- diffuse optical tomography has a feature that the number of measurement data is extremely large compared to other methods such as X-ray CT and positron tomography (PET).
- PET positron tomography
- the amount of measurement data is the product of the number of light detection positions and the number of time-resolved steps.
- the number of data is 28800. The number of such data is much larger than the size of the image data (in one example, 64 rows and 64 columns, that is, 4096 pixels), and it takes a long time to calculate the image data.
- the amount of data further increases.
- the present invention relates to a measurement data selection method for a biological measurement apparatus, a light emission position determination method for a biological measurement apparatus, and a living body that can reduce the number of pieces of measurement data required to create image data to shorten the creation time of the image data. It aims at providing a measuring device.
- a measurement data selection method of a biological measurement apparatus is a measurement target that is obtained at a plurality of light detection positions by emitting pulsed light from a plurality of light emission positions to a measurement site of a subject.
- This is a method of selecting measurement data used to create internal image data in a biological measurement apparatus that creates internal image data of a measurement site based on a time-resolved waveform of diffused light from the site.
- measurement data y 1 to y N1 obtained for each combination of a plurality of light emission positions, a plurality of light detection positions, and a plurality of decomposition times in a time-resolved waveform.
- x is a vector whose component is a pixel value of learning image data prepared in advance
- a 1 is a system matrix for calculating internal image data from measurement data y 1 to y N1.
- a living body measurement apparatus includes a light emitting unit that emits pulsed light from a plurality of light emission positions to a measurement site of a subject, and a target obtained at the plurality of light detection positions.
- a calculation unit that creates internal image data of the measurement target part based on the time-resolved waveform of the diffused light from the measurement part.
- the calculation unit includes measurement data y 1 to y N1 (where N1 is an integer of 2 or more) obtained for each combination of a plurality of light emission positions, a plurality of light detection positions, and a plurality of decomposition times in the time-resolved waveform.
- x is a vector whose component is a pixel value of learning image data prepared in advance
- a 1 is a system matrix for calculating internal image data from measurement data y 1 to y N1.
- conditional expressions (3) and (4) or the conditional expression (5) are satisfied (or the conditional expressions (7) and (8), or A vector y satisfying conditional expression (9) is obtained.
- Conditional expressions (3) and (7) are conditions for minimizing the L0 norm of the vector y, and conditional expressions (4) and (8) re-create the same image data as the learning image data. This is a constraint condition for suppressing the reconstruction error ⁇ 2 when configured to a predetermined value or less.
- Conditional expressions (5) and (9) are obtained by rewriting conditional expressions (3) and (4) and (7) and (8), which are problems with constraints, into problems without constraints. .
- a vector y satisfying conditional expressions (3) and (4) or conditional expression (5) (or satisfying conditional expressions (7) and (8) or conditional expression (9)) has a reconstruction error.
- the number of non-zero measurement data among the measurement data y 1 to y N1 is minimized while being suppressed within the allowable range.
- measurement data that is zero is unnecessary in order to obtain image data whose reconstruction error is within an allowable range, and measurement data that is not zero is the minimum necessary measurement data.
- the L0 norm of the vector y in the conditional expressions (3) and (5) (or the conditional expressions (7) and (9)) is changed to L1 of the vector y.
- the norm of the vector y can be easily calculated, and the calculation time of the minimum necessary measurement data can be shortened.
- M pieces of learning image data (M is an integer of 2 or more) are prepared in advance, and pixel values of the M pieces of learning image data are set.
- conditional expressions (4) and (5) (or the conditional expressions (8) and (9)), where x 1 to x M are the vectors used as components The It may be replaced with and calculated. Thereby, not only specific learning image data but also suitable measurement data for various learning image data can be selected.
- N2 groups (where N2 is an integer of 2 or more) are grouped, and a vector consisting of vectors y 1 to y N2 whose components are measured data for each of the N2 groups.
- x is a vector whose component is a pixel value of learning image data prepared in advance
- a 2 is a system matrix for calculating internal image data from vectors y 1 to y N2
- conditional expressions (3) to (5) instead of conditional expressions (3) to (5), the following conditional expressions (13) and (14) (Where ⁇ is an arbitrary constant) or the following conditional expression (15) (However, ⁇ is an arbitrary constant.)
- the vector y satisfying the above is obtained by back calculation, and when measuring the subject, the internal image data is created using only the measurement data corresponding to the non-zero component of the vector y. May be.
- the measurement data selection method and the biological measurement apparatus of the above-described biological measurement apparatus instead of the vector y having the measurement data as a component, the measurement data is classified into a plurality of sets according to a predetermined rule, and the measurement data for each of the plurality of sets The above conditional expression calculation is performed using a vector y composed of vectors y 1 to y N2 having as components. Thereby, it is possible to know a set that is unnecessary to obtain image data whose reconstruction error is within an allowable range among a plurality of sets classified according to a predetermined rule.
- a typical example of the predetermined rule is a light emission position. Classification, classification by light detection position, and classification by decomposition time.
- a plurality of measurement data obtained for each combination of a plurality of light emission positions, a plurality of light detection positions, and a plurality of decomposition times in the time-resolved waveform are obtained.
- the vectors y 1 to y N2 may be classified for each decomposition time. This eliminates the measurement data obtained at the decomposition time with a small influence on each pixel value of the internal image data, and only the measurement data obtained at the decomposition time with a large influence on each pixel value can be used. The creation time of internal image data can be shortened effectively.
- the calculation unit obtains measurement data obtained for each combination of a plurality of light emission positions, a plurality of light detection positions, and a plurality of decomposition times in the time-resolved waveform for each of the plurality of light emission positions.
- the vectors y 1 to y N2 are classified into vectors y 1 to y N 2, and the vector y satisfying the conditional expressions (13) and (14) or the conditional expression (15) is obtained by back calculation.
- the apparatus configuration can be simplified and the creation time of the internal image data can be effectively shortened.
- the light emission position determination method of the biological measurement apparatus which concerns on one Embodiment of this invention is a method of determining a light emission position using the measurement data selection method of the biological measurement apparatus mentioned above.
- measurement data obtained for each combination of a plurality of light emission positions, a plurality of light detection positions, and a plurality of decomposition times in a time-resolved waveform are classified into a plurality of light emission positions and vectors y 1 to y are used.
- N2 is obtained by back-calculating the vector y that satisfies the conditional expressions (13) and (14) or the conditional expression (15).
- a light emitting means for emitting light is arranged only at a light emitting position corresponding to a non-zero component of the vector y.
- the image is obtained by reducing the number of measurement data necessary for creating the image data. Data creation time can be reduced.
- FIG. 1 is a diagram showing a configuration of a biological measurement apparatus according to the first embodiment of the present invention.
- FIG. 2 is a diagram schematically showing a measurement site and a plurality of light emission / measurement ends.
- FIG. 3A schematically shows an example of the waveform of the measurement light emitted from a certain light emission position and the waveform of the scattered light detected at a certain light detection position after propagating through the measurement site.
- FIG. 3B is a diagram showing data values at each time when the intensity of the scattered light shown in FIG. 3A is detected and time-resolved.
- FIG. 4 is a diagram showing the learning image data used in the first embodiment.
- FIG. 1 is a diagram showing a configuration of a biological measurement apparatus according to the first embodiment of the present invention.
- FIG. 2 is a diagram schematically showing a measurement site and a plurality of light emission / measurement ends.
- FIG. 3A schematically shows an example of the waveform of the measurement light emitted from a certain light emission
- FIG. 5 is a diagram conceptually illustrating an operation of classifying a plurality of measurement data for each decomposition time to obtain vectors y 1 to y k .
- FIG. 6A is a diagram showing internal image data when reconstruction is performed using only measurement data obtained at the 23 selected decomposition times.
- FIG. 6B is a diagram showing internal image data when 23 decomposition times are randomly selected as a comparative example.
- FIG. 7A is a diagram showing internal image data when reconstruction is performed using only measurement data obtained at the selected 17 decomposition times.
- (B) of FIG. 7 is a figure which shows internal image data at the time of selecting 17 decomposition
- FIG. 8A is a diagram showing internal image data when reconstruction is performed using only measurement data obtained at 11 selected decomposition times.
- FIG. 8B is a diagram showing internal image data when 11 decomposition times are selected at random as a comparative example.
- FIG. 9A is a block diagram illustrating a photodetector, a signal processing circuit, and a calculation unit included in the biological measurement apparatus.
- FIG. 9B shows an example of a detection signal waveform (typically an impulse response waveform) of scattered light obtained in the photodetector.
- FIG. 9C shows an example of the waveform of the gate signal in the time gate circuit.
- (D) of FIG. 9 has shown the measurement data obtained in a data collection part.
- FIG. 10 is a diagram showing learning image data used in the second embodiment.
- FIG. 10 is a diagram showing learning image data used in the second embodiment.
- FIG. 11 is a diagram conceptually illustrating an operation of classifying a plurality of measurement data for each light emission position to obtain vectors y 1 to y m .
- FIG. 12 is a diagram illustrating a specific area of the learning image data as an example.
- FIG. 13 is a diagram showing the light emission positions selected in the second embodiment.
- FIG. 14A is a diagram showing internal image data when reconstruction is performed using only measurement data corresponding to nine selected light emission positions.
- FIG. 14B is a diagram showing internal image data when nine light emission positions are randomly selected as a comparative example.
- FIG. 15A is a diagram showing internal image data when reconstruction is performed using only measurement data corresponding to three selected light emission positions.
- FIG. 15B is a diagram showing internal image data when three light emission positions are randomly selected as a comparative example.
- FIG. 16A is a diagram showing internal image data when reconstruction is performed using only measurement data corresponding to one selected light emission position.
- FIG. 16B is a diagram showing internal image data when one light emitting position is randomly selected as a comparative example.
- FIG. 17 is a diagram illustrating an example of the light emission position varying unit.
- FIG. 18 is a diagram illustrating an arrangement example of the light emission / measurement end according to the location of the tumor when the measurement target tumor exists in the measurement site.
- FIG. 19 is a diagram showing another example of the light emission position varying means.
- FIG. 1 is a diagram illustrating a configuration of a biological measurement apparatus 10 according to the first embodiment.
- the biological measurement apparatus 10 of the present embodiment is a so-called diffused light tomography apparatus using TRS, which irradiates light to a measurement site B of a subject who is a measurement target, detects diffused light (return light), Based on the detected position and the measured light quantity data (for example, time-resolved photon histogram), the average flight path and average optical path length of the photons are estimated, and the in-vivo information is imaged as an image reconstruction problem.
- TRS diffused light tomography apparatus using TRS, which irradiates light to a measurement site B of a subject who is a measurement target, detects diffused light (return light), Based on the detected position and the measured light quantity data (for example, time-resolved photon histogram), the average flight path and average optical path length of the photons are estimated, and the in-vivo information is imaged as an image reconstruction
- the image obtained by this apparatus is a functional image of a body tissue, for example, which visualizes the position of a tumor and the distribution of oxygenated hemoglobin and deoxygenated hemoglobin.
- a to-be-measured part B a head, a female breast, etc. are assumed, for example.
- the biological measurement apparatus 10 includes a light irradiating unit that irradiates measurement light into the measurement site B, a light detection unit that detects diffused light generated from the measurement site B due to light irradiation from the light irradiation unit, and a light A calculation unit that calculates a spatial distribution of the absorption coefficient of the measurement site B based on an output signal from the detection unit and creates a reconstructed image of the measurement site B;
- the light irradiation unit is a part for emitting light from a plurality of light emission positions to the measurement site B of the subject.
- the light irradiating unit of the present embodiment includes a light emitting end (light emitting means), a light source 22, and light included in each of n (n is an integer of 2 or more) light emitting / measuring ends 16 attached to the measurement site B.
- the switch 24 is configured.
- the light source 22 for example, a laser diode can be used.
- the wavelength of the measurement light is preferably a wavelength in the near infrared region of about 700 nm to 900 nm from the relationship between the transmittance of the living body and the absorption coefficient of the absorber to be quantified.
- Measured light is emitted from the light source 22 as continuous light, for example.
- the measurement light emitted from the light source 22 is irradiated to the measurement site B from the light emission / measurement end 16.
- the optical switch 24 is a 1-input n-output optical switch, which inputs light from the light source 22 through the light source optical fiber 26 and supplies this light to each of the n light emission / measurement ends 16 in order. To do. That is, the optical switch 24 sequentially selects the n output optical fibers 28 connected to each light output / measurement end 16 one by one, and optically connects the output optical fibers 28 and the light source 22. .
- the light detection unit is a part that detects the intensity of diffused light from the measurement site B at a plurality of light detection positions.
- the light detection unit of the present embodiment includes an optical measurement end included in each of the n light emission / measurement ends 16 described above, n photodetectors 30 corresponding to each of the n light emission / measurement ends 16, and The n shutters 32 are arranged in front of the input unit of each photodetector. Diffused light from the measurement site B emitted to the optical measurement end of each light emission / measurement end 16 is input to each of the n photodetectors 30 via the detection optical fiber 34.
- the photodetector 30 generates an analog signal according to the light intensity of the diffused light that has reached the corresponding light emission / measurement end 16.
- photodetector 30 various things such as a photomultiplier tube (PMT: Photomultiplier Tube), a photodiode, an avalanche photodiode, and a PIN photodiode can be used.
- PMT Photomultiplier Tube
- a photodiode an avalanche photodiode
- a PIN photodiode a photodiode
- the diffused light from the measurement site B is weak, it is preferable to use a photodetector with high sensitivity or high gain.
- a signal processing circuit 36 is connected to the signal output terminal of the photodetector 30, and the signal processing circuit 36 digitizes the analog signal output from the photodetector 30 and time-resolves it to perform the TRS calculation. Generate measurement data.
- the signal processing circuit 36 provides the generated measurement data to the calculation unit 14.
- the calculation unit 14 calculates a light absorption coefficient distribution in the measurement site B based on the measurement data provided from the signal processing circuit 36, and a reconstructed image relating to the inside of the measurement site B (hereinafter referred to as internal image data). ).
- the calculation unit 14 is realized by a computer having a calculation unit such as a CPU (Central Processing Unit) and a storage unit such as a memory.
- the calculation unit 14 may further have a function of controlling the light emission of the light source 22, the operation of the optical switch 24, and the opening / closing of the shutter 32.
- a recording / display unit 38 is connected to the calculation unit 14, and the calculation result in the calculation unit 14, that is, the internal image data of the measurement site B can be visualized.
- Calculation of internal information of the measurement site B is performed as follows, for example.
- the measurement light is sequentially emitted from each of the n light emission / measurement ends 16 into the measurement site B, and the intensity of the light that has passed through the measurement site B and diffused is determined by the n light emission / measurement ends 16.
- n photodetectors 30 are detected by n photodetectors 30. Based on this detection result, the spatial distribution of the absorption coefficient inside the measurement site B is calculated, and internal image data including information (internal information) on the position and shape of the absorber such as a tumor is created.
- Non-Patent Document 1 For calculating the absorption coefficient distribution in the calculation unit 14, for example, a well-known method as described in detail in Non-Patent Document 1 may be used.
- the calculation unit 14 of the present embodiment excludes measurement data that has a small influence on each pixel value of the internal image data from among a plurality of measurement data obtained from the light detection unit, and each pixel of the internal image data. It has a function to selectively use only measurement data that has a large influence on the value.
- a method for selecting such measurement data in the calculation unit 14 will be described. Note that the measurement data selection method described below may be performed when the biological measurement apparatus 10 is manufactured. In that case, when measuring the measurement site B, the calculation unit 14 may be programmed in advance so that the internal image data is created using only the selected measurement data.
- FIG. 2 is a diagram schematically showing a measurement site B and a plurality of light emission / measurement ends 16.
- measurement light is emitted from each of the m light emission / measurement ends 16 to the measurement site B, and scattered light is measured at each light emission / measurement end 16 to obtain a plurality of measurement data.
- the plurality of measurement data is measurement data at each time that is time-resolved at each light detection position.
- FIG. 3A shows an example of the waveform of the measurement light P1 emitted from a certain light emission position and the waveform of the scattered light P2 detected at a certain light detection position after propagating through the measurement site B. It is a figure shown roughly.
- FIG. 3B is a diagram showing data values at each time when the intensity of the scattered light P2 shown in FIG. 3A is detected and time-resolved.
- the horizontal axis represents time.
- the vertical axis in FIG. 3A represents the light intensity
- the vertical axis in FIG. 3B represents the magnitude of the data value.
- the measurement light P1 is emitted as pulsed light to the measurement site B, but is diffused inside the measurement site B and passes through optical paths of various lengths.
- the waveform of the scattered light P2 has a shape extending back and forth in time.
- k is an integer greater than or equal to 2 (the number of time-resolved steps)
- Such measurement data d 1 , d 2 ,..., D k are obtained for each of the m light emission positions at each of the m light measurement positions. That is, measurement data is obtained for each combination of m light emission positions, m light detection positions, and k decomposition times, and a total of (m ⁇ m ⁇ k) measurement data is obtained. It will be.
- learning image data is prepared in advance.
- the learning image data is prepared in advance as an example of the internal image data.
- an area in the internal image data created by the calculation unit 14 that requires a relatively clear image quality for example, a measurement site B Image data such that a light absorber exists in an area where a tumor is likely to occur.
- a vector having a plurality of pixel values of the learning image data as components is applied to the vector x described above.
- condition (17) is a target function in the present embodiment, a condition for minimizing the L0 norm of a vector y consisting of measured data y 1 ⁇ y N1, measurement data y 1 to be used for image reconstruction ⁇ Y This is a condition for minimizing the number of non-zero measurement data among N1 .
- conditional expression (18) is a constraint condition for suppressing the reconstruction error ⁇ 2 when the same image data as the learning image data is reconstructed to a predetermined value or less.
- the calculation unit 14 may obtain a vector y that satisfies the following conditional expression (19) instead of the above conditional expressions (17) and (18).
- ⁇ is an arbitrary constant.
- the conditional expression (19) is obtained by rewriting the conditional expressions (17) and (18), which are minimization problems with constraints, into minimization problems without constraints, and the conditional expressions (17) and (18). It is easier to calculate.
- Such a minimization problem without a constraint can be easily solved by an iterative method called an iterative soft-thresholding method in the field of compressed sensing, for example.
- the upper limit of reconstruction error is defined by ⁇
- conditional expression (19) the upper limit of reconstruction error is defined by ⁇ .
- the vector y satisfying the conditional expressions (17) and (18) or the conditional expression (19) has the number of non-zero measurement data among the measurement data y 1 to y N1 while suppressing the reconstruction error within an allowable range. It will be minimized.
- measurement data that is zero is not necessary to obtain image data whose reconstruction error is within an allowable range, and measurement data that is not zero is an image whose reconstruction error is within an allowable range. This is the minimum measurement data required to obtain data.
- the calculation unit 14 uses only the measurement data of the light emission position, the light detection position, and the decomposition time corresponding to the measurement data that is not zero among the measurement data y 1 to y N1 as the measurement target B. Create internal image data for use during measurement.
- the necessary minimum measurement is performed when measuring the subject after calculating the vector y indicating the minimum measurement data as described above.
- Internal image data is created using only the data. Therefore, it is possible to reduce the time for creating image data by reducing the number of measurement data.
- the L0 norm of the vector y is minimized in the conditional expression (17), and the expression including the L0 norm of the vector y is also minimized in the conditional expression (19).
- the L0 norm is a non-convex function, the amount of calculation for minimization increases. Therefore, in this modification, the L0 norm of the vector y in the conditional expressions (17) and (19) is replaced with the L1 norm that is a convex function to perform an approximate minimization calculation. That is, the calculation unit 14 may obtain a vector y that satisfies the following conditional expressions (20) and (21) or a vector y that satisfies the conditional expression (22). According to this modification, the norm of the vector y can be easily calculated, and the time required for selecting the minimum necessary measurement data can be shortened.
- one piece of learning image data is prepared in advance, and conditional expressions (18) and (19) are calculated.
- the light emission position, the light detection position, and the decomposition time of the finally selected measurement data are the light emission position, the light detection position, and the decomposition time that are optimum for the learning image data.
- the reconstruction error is not always sufficiently small.
- the number of pieces of learning image data prepared in advance is set to 2 or more. That is, typical M pieces of image data for learning (M is an integer of 2 or more) assumed in the measurement site B are prepared in advance, and a vector whose components are pixel values of the M pieces of image data for learning is used.
- x 1 to x M in each conditional expression The Replace with and calculate. Thereby, not only specific learning image data but also suitable measurement data can be selected for various learning image data, and the reconstruction error can be reduced.
- learning image data similar to that in the above embodiment is prepared in advance. Then, a vector having a plurality of pixel values of the learning image data as components is applied to the vector x described above.
- Condition (26) is a target function in the present embodiment, a condition for minimizing the L0 norm of a vector y comprising a vector y 1 ⁇ y N1, the vector y 1 ⁇ y used for image reconstruction This is a condition for minimizing the number of non-zero vectors in N1 .
- Conditional expression (27) is a constraint condition for suppressing the reconstruction error ⁇ 2 when the same image data as the learning image data is reconstructed to a predetermined value or less.
- conditional expression (28) is obtained by rewriting conditional expressions (26) and (27), which are minimization problems with constraints, into minimization problems without constraints, and conditional expressions (26) and (27). It is easier to calculate.
- the measurement data is classified into a plurality of sets according to a predetermined rule, and the vector y 1 using the measurement data for each of the plurality of sets as a component.
- ⁇ Y The above conditional expression is calculated using the vector y consisting of N2 .
- a typical example of the predetermined rule depends on the light emission position. Classification, classification based on the light detection position, and classification based on the decomposition time may be mentioned.
- N2 m.
- N2 k.
- FIG. 4 is a diagram showing the learning image data D1 used in the present embodiment, and includes a plurality of spots SP simulating a tumor or the like.
- FIG. 5 is a diagram conceptually showing an operation of classifying a plurality of measurement data into the decomposition times to obtain vectors y 1 to y k .
- FIG. 6A is a diagram showing internal image data when reconstruction is performed using only the measurement data obtained at the 23 decomposition times.
- FIG. 6B is a diagram showing internal image data when 23 decomposition times are randomly selected as a comparative example. As shown in FIG. 6A and FIG. 6B, it can be seen that in this embodiment, a good image quality can be obtained as compared with the comparative example by appropriately selecting the 23 decomposition times.
- FIG. 7A is a diagram showing internal image data when reconstruction is performed using only the measurement data obtained at the 17 decomposition times.
- FIG. 7B is a diagram showing internal image data when 17 decomposition times are randomly selected as a comparative example. As shown in FIG. 7A and FIG. 7B, it can be seen that, in the present embodiment, it is possible to obtain better image quality than in the comparative example by appropriately selecting 17 decomposition times.
- the vectors corresponding to the eleventh eighteenth to eighteenth decomposition times counted from the measurement start time were not zero vectors but significant values.
- FIG. 8A is a diagram showing internal image data when reconstruction is performed using only the measurement data obtained at these eleven decomposition times.
- FIG. 8B is a diagram showing internal image data when 11 decomposition times are selected at random as a comparative example. As shown in FIG. 8A and FIG. 8B, it can be seen that, in the present embodiment, better image quality can be obtained compared to the comparative example by appropriately selecting 11 disassembly times.
- the measurement data selection method for example, by classifying the measurement data for each decomposition time of the time-resolved spectroscopy, the optimum among the many decomposition times is obtained. Decomposition time can be determined. Then, by reconstructing the internal image data using only the measurement data at the optimal decomposition time, it is possible to obtain internal image data with good image quality.
- measurement data obtained at a relatively early decomposition time among a plurality of decomposition times is useful for improving the image quality of the internal image data.
- FIG. 9A is a block diagram illustrating the photodetector 30, the signal processing circuit 36, and the calculation unit 14 included in the biological measurement apparatus 10.
- the signal processing circuit 36 includes a time gate circuit (Time Gate Circuit; TGC) 36a and a data collection unit 36b. It is preferable to have.
- FIG. 9B shows an example of a detection signal waveform (typically an impulse response waveform) of scattered light obtained in the photodetector 30, and
- FIG. 9C shows a time gate circuit 36a.
- 9D shows an example of the waveform of the gate signal in FIG. 9, and FIG. 9D shows measurement data obtained in the data collection unit 36b.
- FIG. 10 is a diagram showing the learning image data D2 used in the present embodiment, and includes a plurality of spots SP simulating tumors and the like.
- FIG. 10 also shows the positions of the light emission / measurement end 16 (that is, the light emission position and the light detection position) A 1 to A 20 .
- FIG. 11 is a diagram conceptually illustrating an operation of classifying a plurality of measurement data for each light emission position to obtain vectors y 1 to y m .
- the conditional expression (28) described above may be modified as follows.
- the vector z is a vector indicating a pixel value of a specific region (particularly, a region requiring image quality, a region where a tumor is easily generated, etc.) among the vector x indicating each pixel value of the learning image data D2.
- FIG. 12 is a diagram illustrating the specific area D3 of the learning image data D2 as an example.
- the system matrix H is a system matrix obtained by extracting part related vector z of the system matrix A 2.
- FIG. 14A is a diagram showing internal image data when reconstruction is performed using only measurement data corresponding to these nine light emission positions.
- FIG. 14B shows a comparative example in which nine light emission positions are selected at random (specifically, light emission positions A 2 , A 3 , A 5 , A 8 , A 12 , A 15 , A 17 , A 18 , A 20 ). As shown in FIG. 14A and FIG. 14B, it can be seen that in this embodiment, it is possible to obtain better image quality than in the comparative example by appropriately selecting nine light emission positions. .
- FIG. 15A is a diagram showing internal image data when reconstruction is performed using only measurement data corresponding to these three light emission positions.
- FIG. 15B is a diagram showing internal image data when three light emission positions are selected at random (specifically, light emission positions A 15 , A 17 , A 18 ) as a comparative example. It is. As shown in FIG. 15A and FIG. 15B, it can be seen that in this embodiment, it is possible to obtain better image quality than in the comparative example by appropriately selecting the three light emitting positions. .
- the vector corresponding to one light emission position close to the specific region D3 is not a zero vector but has a significant value.
- FIG. 16A is a diagram showing internal image data when reconstruction is performed using only measurement data corresponding to the one light emission position.
- FIG. 16B is a diagram showing internal image data when one light emission position is selected at random (specifically, the light emission position A 15 ) as a comparative example. As shown in FIG. 16A and FIG. 16B, it can be seen that in this embodiment, it is possible to obtain better image quality than in the comparative example by appropriately selecting one light emitting position. .
- the measurement data selection method for example, by classifying measurement data for each light emission position, the image quality is maintained from among a large number of light emission positions. Therefore, the optimum light emission position can be determined. Then, by reconstructing the internal image data using only the measurement data at the optimal light emission position, it is possible to obtain internal image data with good image quality.
- tumors such as cancer cells tend to occur in a specific region with a high probability, but according to this embodiment, measurement data corresponding to a light output position close to the specific region D3 among a plurality of light output positions.
- the biological measurement apparatus 10 preferably further includes a light emission position variable unit.
- the light emission position variable means can move the light emission / measurement end 16 (see FIG. 1) for emitting measurement light to two or more light emission positions selected from a plurality of preset light emission positions. Or it is a means comprised so that it can arrange
- the light emission position changing means is configured to select only n (n is an integer of 1 or more, n ⁇ m) light emission / measurement ends 16 among m light emission / measurement ends 16 arranged in advance. It is comprised so that measurement light may be irradiated from.
- Such light emission position varying means is preferably realized by selectively supplying measurement light to only the n light emission / measurement ends 16 by means of the optical switch 24, for example.
- the light emission position varying means may be configured so that, for example, n light emission / measurement ends 16 prepared in advance move to n light emission positions selected from the m light emission positions.
- An actuator (not shown) attached to the emission / measurement end 16 may be controlled.
- the light emission position changing means is a mechanism that allows the operator to freely attach and detach, for example, n light emission / measurement ends 16 to n light emission positions selected from m light emission positions. It may be.
- FIG. 17 is a diagram showing an example of the light emission position varying means.
- the light emission position varying means shown in the figure includes m folders 17 to which the light emission / measurement end 16 can be attached and detached.
- the m folders 17 are attached to the measuring cup 40 at a predetermined interval.
- the measurement cup 40 is a substantially hemispherical container having an open upper end. For example, a breast is inserted into the measurement cup 40 as the measurement site B. Further, a liquid interface agent having a light absorption coefficient and a light scattering coefficient equivalent to those of the measurement site B is injected between the measurement site B and the measurement cup 40.
- FIGS. 18A and 18B show an arrangement example of the light emission / measurement end 16 according to the location of the tumor E when the tumor E to be measured is present in the measurement site B.
- the light emission position variable means that allows the operator to freely attach and detach the n light emission / measurement ends 16 to the n light emission positions selected from the m light emission positions.
- a small number of light emitting / measuring ends 16 can be arranged at optimal positions to create high-quality internal image data.
- the calculation unit 14 of the biological measurement apparatus 10 may present an optimal light emission position to the operator through display means such as a display. If the number of light emitting / measuring terminals 16 is not limited, the light emitting / measuring terminals 16 are attached to all the folders 17 in the figure, and the n light emitting / measuring / measurements are obtained from the obtained measurement data.
- the internal image data may be created using only the measurement data related to the end 16.
- FIG. 19 is a diagram showing another example of the light emission position varying means.
- the light emission position varying means shown in the figure includes a plurality of holder rings 19 to which the light emission / measurement ends 16 are fixed.
- the plurality of holder rings 19 surround the measurement site B and are arranged side by side in the insertion direction of the measurement site B. Further, the interval F between the plurality of holder rings 19 is variable, and the actuator is arranged so that the light emitting / measuring end 16 moves to n light emitting positions selected from m light emitting positions. (Not shown).
- the light emitting / measuring end 16 irradiates measurement light to the inside of the measurement site B while being in contact with it.
- the measurement data selection method of the biological measurement device, the light emission position determination method of the biological measurement device, and the biological measurement device are not limited to the above-described embodiments, and various other modifications are possible.
- each modification, and each example the calculation unit of the biological measurement device calculates the conditional expression to obtain measurement data or the light emission position to be selected.
- the manufacturer may perform the manufacturing of the biological measuring device.
- the living body measurement apparatus may be completed in a state in which the light emission / measurement end is arranged in advance at the selected optimal light emission position.
- the present invention relates to a measurement data selection method for a biological measurement apparatus, a light emission position determination method for a biological measurement apparatus, and a living body that can reduce the number of pieces of measurement data required to create image data to shorten the creation time of the image data. It can be used as a measuring device.
- DESCRIPTION OF SYMBOLS 10 ... Biological measuring device, 14 ... Operation part, 16 ... Light emission / measurement end, 17 ... Folder, 19 ... Holder ring, 22 ... Light source, 24 ... Optical switch, 26 ... Optical fiber for light source, 28 ... Optical fiber for emission , 30: photodetector, 32: shutter, 34: optical fiber for detection, 36: signal processing circuit, 36a: time gate circuit, 36b ... data collection unit, 38 ... display unit, 40 ... measuring cup, B ... measured Part, D1, D2 ... image data for learning, D3 ... specific area, P1 ... measurement light, P2 ... scattered light, SP ... spot.
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Abstract
Description
図1は、第1実施形態に係る生体計測装置10の構成を示す図である。本実施形態の生体計測装置10は、いわゆるTRSによる拡散光トモグラフィ装置であって、計測対象である被検者の被計測部位Bに光を照射し、拡散光(戻り光)を検出し、その検出位置と計測された光量データ(例えば時間分解光子ヒストグラム)とに基づいて、光子の平均飛行経路と平均光路長を推定し、画像再構成問題として体内の情報を画像化する。この装置によって得られる画像は、例えば腫瘍の位置や酸素化ヘモグロビン及び脱酸素化ヘモグロビンの分布を可視化したものであり、体組織の機能画像である。なお、被計測部位Bとしては、例えば頭部や女性の乳房等が想定される。
上記実施形態では、条件式(17)においてベクトルyのL0ノルムを最小化しており、また、条件式(19)においてもベクトルyのL0ノルムが含まれる式を最小化している。しかしながら、L0ノルムは非凸関数であることから、最小化のための計算量が多くなる。そこで、本変形例では、条件式(17)及び(19)のベクトルyのL0ノルムを、凸関数であるL1ノルムに置き換えることにより、近似的に最小化計算を行う。すなわち、演算部14は、以下の条件式(20)及び(21)を満たすベクトルyを求めるか、若しくは、条件式(22)を満たすベクトルyを求めるとよい。
上記実施形態では、予め一つの学習用画像データを用意し、条件式(18)及び(19)を計算している。この場合、最終的に選択される計測データの光出射位置、光検出位置、及び分解時刻は、その学習用画像データにとって最適な光出射位置、光検出位置、及び分解時刻であり、その学習用画像データとは異なる画像データに関しては、再構成誤差が十分に小さくなるとは限らない。
本変形例では、上記実施形態においてm個の光出射位置、m個の光検出位置、及びk個の分解時刻の組み合わせ毎に得られる(m×m×k)個の計測データを、所定のルールに従ってN2個(但し、N2は2以上の整数)の組に分類する。そして、N2個の組毎の計測データを成分とするベクトルy1~yN2を定義し、これらのベクトルy1~yN2からなる次のベクトルyを定義する。
上述した第3変形例において、分解時刻による分類を行った場合の実施例について説明する。図4は、本実施例で用いられた学習用画像データD1を示す図であって、腫瘍等を模した複数のスポットSPが含まれている。また、本実施例では、計測条件を以下のように設定した。
画像サイズ:32×32
光出射位置の数:12個
光検出位置の数:12個
計測時間:20ナノ秒
分解時刻の数(時間サンプリング数):k=140
計測データの総数:20160個
上述した第3変形例において、光出射位置による分類を行った場合の実施例について説明する。本実施例では、第3変形例に係る計測データ選択方法を用いて、最適な光出射位置を決定する。
画像サイズ:32×32
光出射位置の数:m=20個
光検出位置の数:m=20個
計測時間:10ナノ秒
分解時刻の数(時間サンプリング数):50
計測データの総数:20000個
Claims (12)
- 複数の光出射位置から被検者の被計測部位へパルス状の光を出射し、複数の光検出位置において得られる前記被計測部位からの拡散光の時間分解波形に基づいて前記被計測部位の内部画像データを作成する生体計測装置において、前記内部画像データを作成するために使用される計測データを選択する方法であって、
前記複数の光出射位置、前記複数の光検出位置、及び前記時間分解波形における複数の分解時刻の組み合わせ毎に得られる計測データy1~yN1(但し、N1は2以上の整数)からなるベクトルを
- 前記条件式(2)及び(4)におけるベクトルyのL0ノルムをベクトルyのL1ノルムに置き換えて計算する、請求項1に記載の生体計測装置の計測データ選択方法。
- 前記複数の光出射位置、前記複数の光検出位置、及び前記時間分解波形における複数の分解時刻の組み合わせ毎に得られる前記計測データを所定のルールに従ってN2個(但し、N2は2以上の整数)の組に分類し、前記N2個の組毎の前記計測データを成分とするベクトルy1~yN2からなるベクトルを
- 前記複数の光出射位置、前記複数の光検出位置、及び前記時間分解波形における複数の分解時刻の組み合わせ毎に得られる前記計測データを、前記複数の分解時刻毎に分類して前記ベクトルy1~yN2とする、請求項4に記載の生体計測装置の計測データ選択方法。
- 請求項4に記載された生体計測装置の計測データ選択方法を用いて前記光出射位置を決定する方法であって、
前記複数の光出射位置、前記複数の光検出位置、及び前記時間分解波形における複数の分解時刻の組み合わせ毎に得られる前記計測データを、前記複数の光出射位置毎に分類して前記ベクトルy1~yN2とし、前記条件式(6)及び(7)、若しくは条件式(8)を満たす前記ベクトルyを逆算して求め、前記被検者を計測する際、若しくは前記生体計測装置を製造する際に、該ベクトルyの零ではない成分に対応する前記光出射位置のみに、前記光を出射する光出射手段を配置する、生体計測装置の光出射位置決定方法。 - 複数の光出射位置から被検者の被計測部位へパルス状の光を出射する光出射部と、複数の光検出位置において得られる前記被計測部位からの拡散光の時間分解波形に基づいて前記被計測部位の内部画像データを作成する演算部とを備える生体計測装置であって、
前記演算部は、
前記複数の光出射位置、前記複数の光検出位置、及び前記時間分解波形における複数の分解時刻の組み合わせ毎に得られる計測データy1~yN1(但し、N1は2以上の整数)からなるベクトルを
- 前記演算部は、前記条件式(2)及び(4)におけるベクトルyのL0ノルムをベクトルyのL1ノルムに置き換えて計算する、請求項7に記載の生体計測装置の計測データ選択方法。
- 前記演算部は、前記複数の光出射位置、前記複数の光検出位置、及び前記時間分解波形における複数の分解時刻の組み合わせ毎に得られる前記計測データを所定のルールに従ってN2個(但し、N2は2以上の整数)の組に分類し、前記N2個の組毎の前記計測データを成分とするベクトルy1~yN2からなるベクトルを
- 前記演算部は、前記複数の光出射位置、前記複数の光検出位置、及び前記時間分解波形における複数の分解時刻の組み合わせ毎に得られる前記計測データを、前記複数の分解時刻毎に分類して前記ベクトルy1~yN2とする、請求項10に記載の生体計測装置。
- 前記演算部は、前記複数の光出射位置、前記複数の光検出位置、及び前記時間分解波形における複数の分解時刻の組み合わせ毎に得られる前記計測データを、前記複数の光出射位置毎に分類して前記ベクトルy1~yN2とし、前記条件式(6)及び(7)、若しくは条件式(8)を満たす前記ベクトルyを逆算して求め、
当該生体計測装置は、該ベクトルyの零ではない成分に対応する前記光出射位置に、前記光を出射する光出射手段を移動可能若しくは選択的に配置可能なように構成された光出射位置可変手段を更に備える、請求項10に記載の生体計測装置。
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