JP2010110352A - Region specifying method, volume measuring method using the same, region specifying apparatus and region specifying program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To specify a region of a living body part at one of dead centers of reciprocation or the living body part corresponding to the difference. <P>SOLUTION: A region specifying method for specifying the region of the living body part in volume data by X-ray CT includes a distribution calculation step (R3) of calculating the distribution of an element number to a CT value in cross section data including the region of the reciprocating living body part, and a range setting step (R6, R8) of setting a CT value range on the basis of a motion peak indicating the motion of the living body part in the distribution, and specifies the element region of the set CT value range as the region of the living body part at one of the dead centers of the reciprocation or the living body part corresponding to the difference. Thus, the region of lungs in a diastolic phase and the region of lungs in a contraction phase are specified even for a living body which does not stop breath for instance. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a region specifying method for specifying a region of a living body part in volume data obtained by X-ray CT, a volume measuring method using the same, a region specifying device, and a region specifying program.

The lung is an important organ for a living body, and analysis of X-ray CT data is required for diagnosis, treatment, or research. Conventionally, techniques for analyzing X-ray CT data targeting the lung have been proposed (see, for example, Patent Documents 1 and 2). The lung region extraction device described in Patent Document 1 excludes a region having a certain area or less from the labeled image regions and a predetermined region in contact with the uppermost, lowermost, rightmost, and leftmost portions of the input image. An area is extracted and used as a lung area. Further, the ventilation distribution measuring method described in Patent Document 2 extracts a lung region from a lung CT image during inhalation and a breath CT image that is three-dimensionally imaged, obtains local ventilation of the lung, and performs lung integration by volume integration. The total ventilation volume is calculated.
JP-A-11-151232 JP-A-2005-28121

  However, since the shape of the lung changes due to respiration, observation is difficult. In particular, it is difficult to obtain accurate results by analyzing X-ray CT data of a moving body part in an animal that cannot consciously hold its breath.

  The present invention has been made in view of such circumstances, and is an area specifying method that can specify a living body part at any dead point of a reciprocating motion or a region of a living body part corresponding to a difference between them. An object of the present invention is to provide a volume measuring method, an area specifying device, and an area specifying program using the.

  (1) In order to achieve the above object, a region specifying method according to the present invention is a region specifying method for specifying a region of a living body part in volume data obtained by X-ray CT, wherein the region of a living body part that reciprocates is determined. A distribution calculation step of calculating a distribution of the number of elements with respect to a CT value in the cross-sectional data including, and a range setting step of setting a CT value range based on a motion peak indicating the motion of the living body part in the distribution. The element region of the set CT value range is specified as a biological part at one of the dead points of the reciprocating motion or a region of a biological part corresponding to the difference between them.

  As described above, the region specifying method of the present invention sets the CT value range based on the peak indicating the movement of the living body part, and sets the element area as a living body part at one point in time of the reciprocating movement or the difference between them. Specify as the region of the part Thereby, for example, even for a living body that does not hold its breath, it is possible to specify the lung region in the diastole and the lung region in the systole. The dead point refers to a state in which the acceleration is temporarily zero in a reciprocating motion, and refers to a state in which expansion is maximum or contraction is minimum in a single breath in lung motion.

  (2) Further, in the region specifying method according to the present invention, the range setting step includes a lower limit value setting step in which a lower limit value is set in a base on a side where a CT value of an air peak indicating air is larger in the distribution, An upper limit value setting step for setting an upper limit value at the base on the side where the CT value of the motion peak is larger, and an element region of the CT value range determined by the set lower limit value and upper limit value is defined as the top dead center of the reciprocating motion. It is characterized in that it is specified as a region of a biological part at a point.

  Thereby, the area | region of the biological body part including the part which reciprocates can be pinpointed. For example, it is possible to specify a region indicating an diastolic organ. The base means a position (CT value) that is substantially not included in the peak and other peak ranges, for example, a position that is 2σ or more away from the center position of each peak. It is more preferable if it is a position separated by 3σ or more.

  (3) Further, in the region specifying method according to the present invention, the range setting step includes a lower limit value setting step in which a lower limit value is set in a base on a side where a CT value of an air peak indicating air is larger in the distribution, An upper limit value setting step for setting an upper limit value at the bottom of the side where the CT value of the motion peak is small, and an element region of a CT value range determined by the set lower limit value and upper limit value is set to the bottom of the reciprocating motion. It is characterized in that it is specified as a region of a biological part at a point. Thereby, the area | region of the biological body part except the part which reciprocates can be pinpointed. For example, a region indicating a systolic organ can be identified.

  (4) Further, in the region specifying device according to the present invention, the range setting step includes a lower limit value setting step in which a lower limit value is set in a base on a side where the CT value of the motion peak is small in the distribution, and the motion peak An upper limit value setting step for setting an upper limit value at the base of the larger CT value, and an element region in the CT value range determined by the set lower limit value and upper limit value corresponds to the difference of the reciprocating motion It is characterized by specifying as a region of a living body part. Thereby, the area | region which shows the part which reciprocates can be specified. For example, it is possible to specify a region indicating the difference between the diastole and the systole of the organ.

  (5) Moreover, the region specifying method according to the present invention is characterized in that the living body part is a lung. Thereby, the area | region which shows the lung at the time of exhalation and the lung at the time of inhalation, or the area | region which shows the active part by respiration can be specified.

  (6) The region specifying method according to the present invention is characterized in that the living body part is a heart. Thereby, the area | region which shows the heart at the time of expansion, the heart at the time of contraction, or the area | region which shows the active site | part by a beating can be specified.

  (7) Further, the volume measuring method according to the present invention is characterized in that the volume is measured by three-dimensionally integrating the areas specified using the above-described area specifying method. Thereby, the volume of an organ, the vital capacity, etc. at the time of expansion or contraction can be measured.

  (8) Further, the region specifying device according to the present invention is a region specifying device for specifying a region of a living body part in volume data by X-ray CT, and in cross-sectional data including a region of a living body part reciprocating, An upper limit value or a lower limit value at the base of the motion peak indicating the motion of the living body part; a distribution calculation unit that calculates a distribution of the number of elements with respect to the value; an operation unit that accepts an operation for setting a CT value range in the distribution; A setting correction unit that corrects the upper limit value or the lower limit value to a position that takes a minimum value at the base when an operation for setting is accepted, and the reciprocating motion of the element region of the set CT value range It is specified as the region of the living body part corresponding to the living body part at any one of the dead points or the difference between them. As described above, the region specifying device of the present invention accepts an operation for setting a CT value range, and corrects the upper limit or lower limit position thereof to a position where the minimum value of the CT value is obtained. Thereby, the region of the living body part including or excluding the reciprocating part can be accurately specified. It is also possible to specify a region indicating a reciprocating portion.

  (9) In addition, the region specifying device according to the present invention is a region specifying device that specifies a region of a living body part in volume data by X-ray CT, and in cross-sectional data including a region of a living body part that reciprocates. A distribution calculation unit that calculates a distribution of the number of elements with respect to the value, and a range setting unit that sets a CT value range based on an exercise peak indicating the movement of the living body part in the distribution, and the set CT The element region of the value range is specified as a region of a living body part corresponding to a difference between the living body parts at any dead point of the reciprocating motion. As described above, the region specifying device of the present invention automatically sets the CT value range based on the motion peak indicating the motion of the living body part. This makes it possible to easily identify the diastolic lung region and the systolic lung region even for a living body that cannot hold its breath, for example.

  (10) Further, the region specifying device according to the present invention uses the volume data obtained by the X-ray fluoroscopy function, and calculates the time change calculation unit that calculates the time change of the integrated CT value within the set ROI; An adjustment unit is further provided that adjusts the X-ray CT imaging when the duty ratio indicating one dead center side of the reciprocating motion in the time change is equal to or less than a predetermined ratio.

  As described above, the area specifying apparatus of the present invention uses the volume data obtained by the X-ray fluoroscopy function, and when the duty ratio of the integrated CT value indicated on one dead center side is equal to or less than a predetermined ratio, Adjust for CT imaging. As an adjustment method, for example, the amount of anesthesia can be automatically suppressed to activate the reciprocating motion of the living body part. Note that a warning may be displayed so as not to perform X-ray CT imaging, or imaging may not be forcibly performed.

  (11) An area specifying program according to the present invention is an area specifying program for specifying a region of a living body part in volume data obtained by X-ray CT, wherein CT A distribution calculation process for calculating a distribution of the number of elements with respect to a value, an operation reception process for receiving an operation for setting a CT value range in the distribution, and an upper limit value or a lower limit value at the base of an exercise peak indicating the movement of the living body part When the operation for setting is received, a setting correction process for correcting the upper limit value or the lower limit value to a position at which the minimum value is taken at the base is executed by a computer, whereby the elements of the set CT value range Identifying the region as the region of the biological part corresponding to the biological part at one of the dead points of the reciprocating motion or the difference between them. It is a symptom.

  As described above, the region specifying program of the present invention accepts an operation for setting a CT value range, and corrects the upper limit or lower limit position thereof to a position where the CT value becomes a minimum value. Thereby, the region of the living body part including or excluding the reciprocating part can be accurately specified. It is also possible to specify a region indicating a reciprocating portion.

  (12) Further, the region specifying program according to the present invention is a region specifying program for specifying a region of a living body part in volume data by X-ray CT, and in CT data including a region of a living body part that reciprocates, By causing a computer to execute a distribution calculation process for calculating a distribution of the number of elements with respect to a value, and a range setting process for setting a CT value range based on a motion peak indicating the motion of the living body part in the distribution, The element region of the set CT value range is specified as a living body part at a dead point of the reciprocating motion or a living body part region corresponding to a difference between them.

  As described above, the region specifying program of the present invention automatically sets the CT value range based on the motion peak indicating the motion of the living body part. This makes it possible to easily identify the diastolic lung region and the systolic lung region even for a living body that cannot hold its breath, for example.

  According to the present invention, it is possible to specify a living body part at a dead center of a reciprocating motion or a region of a living body part corresponding to a difference between them. For example, the diastolic lung region, the systolic lung region, or the difference region thereof can be specified for a living body that cannot hold its breath.

  Next, embodiments of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference numerals are given to the same components in the respective drawings, and duplicate descriptions are omitted.

(Device configuration)
FIG. 1 is a schematic diagram showing the configuration of the X-ray CT apparatus 5 and the region specifying apparatus 10. The X-ray CT apparatus 5 includes a microfocus X-ray source having a X-ray focal spot size of a micron unit and a two-dimensional X-ray detector. The X-ray received by the surface is converted into an electric signal and imaged. In detection, the pixel size of the tomographic data can be set, for example, from 20 μm to 135 μm. The X-ray source and the detector are installed on a rotating arm and rotate 360 ° around a predetermined rotation axis. The X-ray CT apparatus 5 includes a support base on which a subject such as a rat or a mouse is placed, and the support base is slid into the X-ray CT apparatus 5 through a gantry hole. The three-dimensional CT data of the subject is measured by the X-ray CT apparatus 5.

  The area specifying apparatus 10 is connected to the X-ray CT apparatus 5 and receives three-dimensional CT data (hereinafter, volume data). The region specifying device 10 not only accumulates X-ray CT data obtained by imaging, but can also measure a CT value in a ROI (region of interest) in real time by an X-ray fluoroscopy function. The region specifying device 10 processes the volume data, calculates the CT value of each element, and can specify the region of the living body part related to the reciprocating motion in the volume data. Next, each part of the area specifying device 10 will be described in detail.

  FIG. 2 is a block diagram showing a functional configuration of the area specifying device 10. As shown in FIG. 2, the area specifying device 10 includes a transmission / reception unit 11, a storage unit 12, an operation unit 13, a time change calculation unit 14, an adjustment unit 15, a display unit 16, a separation unit 21, a distribution calculation unit 22, and a setting correction. A unit 23, a range setting unit 24, a volume calculation unit 25, a report creation unit 26, a control unit 27, and a control bus N. The control bus N conceptually shows a trunk line used for transmission / reception of signals and data between the respective units. The transmission / reception unit 11 is an interface for data transmission / reception, and receives volume data from the X-ray CT apparatus 5.

  The storage unit 12 is configured by a main storage device or an external storage device, and stores received volume data. The operation unit 13 receives an operation via a pointing device or a keyboard, for example. In this way, the operation unit 13 accepts an input for moving and confirming the cursor for designating the cross-sectional position, and performs an operation for setting an upper limit value and a lower limit value of a CT value range (binarization range) and an operation for setting an ROI. enable.

  The time change calculation unit 14 calculates the time change of the integrated CT value within the set ROI using the X-ray CT data obtained by the X-ray fluoroscopy function. The time change of the calculated integrated CT value is obtained as a waveform by the reciprocating motion of the living body part. In particular, the reciprocating motion of organs such as the lungs and the heart is a motion having a certain period. For example, when performing X-ray CT imaging of the lung, it is possible to confirm that the duty ratio is equal to or greater than a predetermined value by observing the respiratory beat using the X-ray CT data obtained by the X-ray fluoroscopy function in advance. . In that case, it is preferable to set the ROI near the diaphragm. Moreover, the time change calculation part 14 has a function which displays the integrated CT value of ROI as a graph, and the user can confirm a graph and can adjust a respiratory beat etc. In the above example, the time change calculation unit 14 calculates a respiratory rate by fluoroscopy, but a dedicated respiratory measurement device (cardiopulmonary measurement device), a sensor or a video camera that detects the movement of the chest due to respiration are used. You may connect to the area | region identification apparatus 10, and may calculate a respiratory beat using the change of a respiration rate, a displacement amount, a brightness, etc.

  Since gas anesthesia shortens the respiratory diastolic period of mice and rats, it is not suitable for the method of imaging lung motion over a predetermined period as in the present invention. It is preferable to maintain the ratio between the diastole and the systole of organs such as the lung and heart at about 50%. Therefore, in order to perform volume calculation and functional part comparison at the time of exhalation and inspiration of the lung at the same time, it is preferable not to perform respiratory suppression by gas anesthesia or the like, and to perform imaging under conditions of the same frequency of exhalation and inspiration. This makes it easier to specify the area of the region indicating the lungs during exhalation and the area of the region indicating the lungs of inspiration, and the accuracy of volume calculation is increased.

The adjustment unit 15 adjusts the X-ray CT imaging when the duty ratio indicating one dead center side of the reciprocating motion is not more than a predetermined ratio. For example, _assuming that the average intake time in one cycle is t _ave and the average cycle T _ave, and the duty ratio t _ave / T _ave is 25% or less, adjustment is performed for X-ray CT imaging. For example, the amount of anesthesia can be automatically suppressed to activate the reciprocating motion of the living body part. Note that a warning may be displayed so as not to perform X-ray CT imaging, or imaging may not be forcibly performed.

  The display unit 16 displays the distribution of the number of elements (number of pixels) for the volume data and CT value of each cross section. The cross-sectional data can be displayed in different colors according to the CT value. When a threshold value is set for the CT value, only the measured values that fall within the threshold value range are displayed in a binary format. It is also possible.

  Note that the cross section of the X-ray CT data includes, for example, an axial plane, a sagittal plane, and a coronal plane. An axial plane is a plane perpendicular to the body axis direction of the subject. The sagittal plane is a plane perpendicular to the body width direction of the subject. The coronal plane is a plane perpendicular to the body thickness direction of the subject. The body axis direction, the coronal plane, and the sagittal plane are preferably determined in advance in the configuration of the X-ray CT apparatus 5 and the subject is placed in accordance with the determined axis during X-ray CT imaging. By installing in such a manner, volume data whose body axis direction is determined can be obtained.

  The separation unit 21 sets a separation line, and separates the region of the biological part to be measured from other regions. Examples of biological parts to be measured include the lungs and the heart. For example, with reference to the spine and rib regions, a separation line is set to separate the lung region from other regions. Specifically, an axial cross section is set in the coronal cross section data in the vicinity of where the spine region is interrupted, and a circular closed curve is set along the rib region on the axial cross section data. By separating the lung region in this way, irrelevant CT value data equivalent to the CT value of the lung reciprocation region can be removed.

  The distribution calculation unit 22 calculates the distribution of the number of elements with respect to the CT value in the cross-sectional data including the region of the living body part that reciprocates. The calculation range is the range separated by the separation unit 21. Using the distribution, the element region of the set CT value range can be specified as a region corresponding to the diastolic or systolic lung or a difference between them.

  The setting correction unit 23 minimizes the upper limit value or the lower limit value at the base when an operation for setting the upper limit value or the lower limit value is received in the manual mode at the base of the peak (motion peak) indicating the motion of the living body part. Correct the position to take the value. Then, the corrected range is binarized and displayed on the display unit 16.

  The range setting unit 24 automatically detects a peak indicating the movement of the living body part in the distribution of the number of elements with respect to the CT value, and sets the CT value range. Accordingly, in the distribution of the number of elements with respect to the CT value, a lower limit value is set at the base of the peak indicating air (air peak) on the side where the CT value is larger. In that case, a peak having a maximum near a CT value of −300 is recognized as a motion peak, and a peak having a maximum near a CT value of −1000 is recognized as an air peak. As a result, the element region of the set CT value range can be specified as a lung region corresponding to the diastolic or systolic lung or a difference between them. When a correction operation is manually performed on the set range, it is reflected. The range setting unit 24 binarizes and displays the determined range. Note that the user can select whether to set the range manually or automatically.

  The volume calculation unit 25 measures the volume by three-dimensionally integrating the areas specified in the set CT value range. Integration is performed by repeating the calculation of the area of the CT value range set by the volume calculation unit 25 for continuous cross-sectional data. For example, in one cross-sectional data of the volume data, the volume calculation unit 25 obtains the area of the diastolic region specified by the CT value range set by the range setting unit 24. The area is calculated by counting the number of elements in the binarized lung diastole region. Similarly, for the diastolic region of the lungs of the adjacent cross-sectional data, the lung diastole region is specified by the set CT value range, and the volume calculation unit 25 obtains the area of the specified region. In this case, in principle, the CT value range uses the initially set range and is not calculated for each cross-sectional data. When specifying adjacent cross-sectional data areas, it is determined whether the elements of the area are in contact with each other. If they are in contact with each other, it is determined that the area is in the diastole of the lungs. It is determined that it is not in the period. In this way, the range setting and counting are repeated, and the volume of the region indicating the diastolic phase of the lung obtained by the volume calculation unit 25 for each cross-sectional data is integrated to obtain the volume of the diastolic phase of the lung.

  Similarly, the range setting unit 24 sets the CT value range of the lung systole, and the volume calculation unit 25 counts the area of the region specified for each cross-sectional data. The area is obtained, and this is repeated to integrate the area to obtain the volume of the lung systole. In addition, the volume calculation unit 25 can determine the vital capacity based on the difference between the diastolic volume and the systolic volume. The volume of the difference may be obtained by obtaining the volume corresponding to each state as described above and taking the difference, or by setting the upper and lower limits corresponding to the difference when setting the CT value range. You may ask directly.

  The report creation unit 26 creates a report that summarizes the diastolic volume, systolic volume, and vital capacity of the lungs in a table. The created report is displayed on the display unit 16. In that case, it is also possible to construct a three-dimensional image and display the skeleton. Thereby, the part which is active in the living body part becomes clear. Further, when an operation such as pressing a report output button is performed, a report of image data and measurement results is output. The control unit 27 is composed of a CPU and controls each unit. For example, the control unit 27 performs processing for acquiring photographed X-ray CT data from the X-ray CT apparatus 5.

(Volume measurement method)
Next, a volume measuring method for specifying a region of a living body part that reciprocates using the region specifying device 10 configured as described above will be described by taking the respiratory motion of an animal lung as an example. FIG. 3 is a flowchart showing a method of measuring the lung volume using the region specifying device 10.

  First, samples such as mice and rats are anesthetized (step S1). Then, using the X-ray fluoroscopic function, it is confirmed that the respiration of the sample is stable (step S2). In that case, the display of the respiratory beat may be visually confirmed by the user, or the duty ratio of the respiratory time may be calculated using the auxiliary function of the region specifying device 10.

  When ready, the X-ray CT apparatus 5 is operated to perform X-ray CT imaging (step S3). The area specifying device 10 reconstructs the captured X-ray CT data as volume data (step S4). Then, the lung volume is measured using the volume data (step S5). The lung volume can be measured by the operation of the region specifying device 10. Below, operation | movement of the area | region identification apparatus 10 is demonstrated and the detail of lung volume measurement is demonstrated.

(Device operation)
FIG. 4 is a flowchart showing the characteristic operation of the area specifying device 10. As shown in FIG. 4, first, the region specifying device 10 selects axial cross-section data from X-ray CT data (step R1). In that case, the axial cross-section data selected from the position of the spine is determined. Specifically, in the coronal cross-section data, the cross section is set at a position near where the spine is interrupted when the spine is traced along the body axis of the sample. Next, the target area is separated by a separation line (step R2). At that time, a closed curve is drawn in a circle along the spine and ribs, and the closed curve is taken as a separation line. The area inside the separation line is the measurement target area.

  Next, the distribution of the number of elements with respect to the CT value over the target region is calculated (step R3). The obtained result is displayed as a histogram graph. Next, the area specifying device 10 accepts selection by the user as automatic or manual (step R4). Then, it is determined whether automatic or manual is selected (step R5).

  When the automatic mode is selected, the CT value range is automatically set according to each purpose (step R6), the set CT value range is binarized, and axial, coronal, and sagittal sectional images are obtained. To display. The criteria for setting the CT value range will be described later. Next, a manual correction operation is accepted as necessary for the automatically set CT value range (step R7), and the process proceeds to step R10.

  On the other hand, if the manual mode is selected, a CT value range setting operation is accepted (step R8). The setting operation is performed, for example, by clicking and specifying an appropriate position as the upper limit value or the lower limit value on the graph of the distribution of the number of image elements with respect to the CT value. In the case of manual operation, since the designated position is not necessarily optimal, the area specifying device 10 corrects the designated position (step R9). The area specifying device 10 binarizes the determined CT value range and displays it on the axial, coronal, and sagittal sectional images. At that time, the diastole region and the systole region are binarized and displayed on the axial, coronal, and sagittal sectional images. At the same time, each area of the diastole and systole regions of each cross-sectional image is calculated and displayed. In addition, the contraction rate of the lung at each cross-sectional position (area of systole ÷ area of diastole × 100%) is calculated and displayed.

  Next, the area of the region specified by the CT value range set for the diastolic (or systolic) lung is calculated for each cross-sectional data, and the volume is calculated by integrating them (step R10). Further, when it is necessary to calculate the vital capacity, the vital capacity is also calculated (step R11). If necessary, the active site is displayed in a skeleton in the three-dimensional image (step R12), and the calculation result is displayed (step R13). Thereby, an active site becomes clear. When the report output button is pressed, a report is output (step R14) and the process ends. Next, the details of the judgment criteria in each step will be described.

(Judgment criteria for respiratory beats)
FIG. 5A is a graph showing the respiratory beat when the mouse is anesthetized shallowly, and FIG. 5B is a graph showing the respiratory beat when the mouse is deeply anesthetized. In each figure, contraction period u ₁ of the lungs to expand the period t _1, t ₂ of the _lung, u ₂ is substantially constant, it is possible to average each to calculate a duty ratio. For example, in the case of performing injection anesthesia, the respiratory rate becomes faster as shown in FIG. Duty ratio of the diastolic lung, _{when t} ave the average value of _{t 1,} the average value of t 1 + _{u 1} was _{T ave,} represented by t _{ave / T} ave. In the case shown in FIG. 5A, the duty ratio is approximately 50%, which is ideal. On the other hand, in the case shown in FIG. 5B, the duty ratio is approximately 17%, which is not suitable for photographing for volume measurement. It is preferable to check whether or not the duty ratio t _ave / T _ave is 25% or less. If the duty ratio t _ave / T _ave is 25% or less, it is preferable to adjust so as to improve the duty ratio or not to shoot.

  Although respiratory synchronized imaging has already been proposed as a technique for accurately capturing the lung shape, only the lung systole can be captured by short-time imaging. This is because mice and rats have a short respiratory diastolic period. Thus, volume measurement in the systole of the lung is easy, but volume measurement in the diastole is difficult. Humans can consciously stop breathing to obtain CT images during inspiration and expiration, respectively, but this is difficult for animals. In such a case, the present invention is very effective.

(Target area separation criteria)
FIG. 6 is a diagram showing a coronal cross-sectional data image obtained by X-ray CT of the body part. As shown in FIG. 6, the coronal cross-sectional data image 100 shows air 110, body surface 120, bone 130, lung 140, and diaphragm fluctuation portion 150. The bone 130 in the figure is shown divided by hatching in a certain direction. The fluctuating portion 150 of the diaphragm is shown with hatching in the opposite direction to the bone. Since the position of the diaphragm fluctuates due to respiration, the density of the fluctuating portion 150 of the diaphragm is displayed lower than that of the body organ and higher than that of air in the X-ray CT image. In the cross section, the display of the spine is interrupted from the spine 130a. Then, an axial section is set around a little back from the spine 130a.

  Next, a separation line is set on the axial plane thus set. FIG. 7 is a diagram showing an axial cross-sectional data image of the body portion by X-ray CT. As shown in FIG. 7, the ribs 131 are formed in a circular shape on the axial cross section, and the lungs are always inside thereof. Utilizing such a property, the separation line 135 is set as a circular closed curve following the rib 131. In this way, the separation line 135 can be drawn.

(Criteria for setting CT value range)
When specifying the region of the living body part at the bottom dead center of the reciprocating motion, the upper limit value and the lower limit value of the CT value are set based on the following criteria. FIG. 8 is a graph showing the distribution of the number of elements with respect to the CT value. Taking the lung as an example, the criteria for specifying a region showing the contraction period of the lung will be described. First, a lower limit value is set at the base on the side where the CT value of the air peak P1 indicating air is larger. Then, an upper limit value is set at the base on the side where the CT value of the motion peak is small. At this time, the fact that the air peak is -1000, the motion peak is -300, and the real organ is around -200 is utilized. Then, the minimum value between the exercise peak P3 and the fat peak P2 is set as the lower limit value. The element region of the CT value range determined by the lower limit value and the upper limit value set in this way is specified.

  9 is an axial cross-sectional data image of the body portion by X-ray CT, FIG. 10 is a coronal cross-sectional data image, and FIG. 11 is a sagittal cross-sectional data image. Each hatched area shows a lung systole area and an area 170 having a CT value equivalent thereto. Note that the hatched area close to the table 160 shows the subcutaneous fat 180.

  FIG. 12 is a graph showing the distribution of the number of elements with respect to the CT value. When specifying the region of the living body part at the top dead center of the reciprocating motion, the upper limit value and the lower limit value of the CT value are set based on the following criteria. Taking the lung as an example, the criteria for specifying the region indicating the diastole of the lung will be described. At this time, a lower limit value is set at the base on the side where the CT value of the air peak P1 indicating air is larger. Then, an upper limit value is set at the base on the side where the CT value of the motion peak is large. For example, the minimum value between the motion peak P3 and the real organ peak P4 is set as the lower limit value. The element region of the CT value range determined by the lower limit value and the upper limit value set in this way is specified.

  FIG. 13 is a diagram showing an axial cross-sectional data image by X-ray CT of the body part, FIG. 14 is a diagram showing a coronal cross-sectional data image by X-ray CT of the body part, and FIG. 15 is sagittal by X-ray CT of the body part. It is a figure which shows a cross-section data image. Each hatched area 170 indicates a diastolic area of the lung and an area having a CT value equivalent thereto.

  When specifying as a region of a living body part corresponding to the difference of reciprocating motion, the upper limit value and the lower limit value of the CT value are set based on the following criteria. In the case of the lung, an area indicating each of the diastole and the systole of the lung is specified. At this time, a lower limit value is set at the base of the motion peak P3 where the CT value is smaller. Then, an upper limit value is set at the base of the motion peak P3 where the CT value is larger. The element region of the CT value range determined by the lower limit value and the upper limit value set in this way is specified. The above operation is performed by executing a program on the area specifying device 10.

  In the above embodiment, the sample is an animal such as a mouse or a rat, but it is also possible to use a human as a measurement target. In that case, vital capacity can be accurately measured without intentionally stopping breathing. Although the description has been mainly made on the lung as a measurement target, the present invention can be applied to an organ such as a heart, and can be applied to measurement of other reciprocating living body parts.

It is the schematic which shows the structure of the area | region identification apparatus of this invention. It is a block diagram which shows the functional structure of the area | region identification apparatus of this invention. It is a flowchart which shows the method of measuring the volume of the lung using the area | region identification apparatus of this invention. It is a flowchart which shows the characteristic operation | movement of the area | region identification apparatus of this invention. It is a graph which shows the breathing rate when each (a) mouse is anesthetized shallowly and (b) the mouse is deeply anesthetized. It is a figure which shows the coronal cross-section data image by X-ray CT of a trunk | drum. It is a figure which shows the axial cross-section data image by X-ray CT of a trunk | drum part. It is a graph which shows distribution of the number of elements with respect to CT value. It is a figure which shows the axial cross-section data image by X-ray CT of a trunk | drum part. It is a figure which shows the coronal cross-section data image by X-ray CT of a trunk | drum. It is a figure which shows the sagittal cross-section data image by X-ray CT of a trunk | drum part. It is a graph which shows distribution of the number of elements with respect to CT value. It is a figure which shows the axial cross-section data image by X-ray CT of a trunk | drum part. It is a figure which shows the coronal cross-section data image by X-ray CT of a trunk | drum. It is a figure which shows the sagittal cross-section data image by X-ray CT of a trunk | drum part.

Explanation of symbols

5 X-ray CT apparatus 10 Region specifying device 11 Transmission / reception unit 12 Storage unit 13 Operation unit 14 Time change calculation unit 15 Adjustment unit 16 Display unit 21 Separation unit 22 Distribution calculation unit 23 Setting correction unit 24 Range setting unit 25 Volume calculation unit 26 Report Creation unit 27 Control unit 100 Coronal cross-section data image 110 Air 120 Body surface 130 Bone 130a Spine 131 Rib 135 Separation line 140 Lung 150 Fluctuating part 160 Stand 170 Area showing systole 180 Subcutaneous fat N Control bus P1 Air peak P2 Fat peak P3 Movement peak P4 Real organ peak t ₁ , t ₂ Diastolic u ₁ , u ₂ systole

Claims (12)

An area specifying method for specifying an area of a living body part in volume data by X-ray CT,
A distribution calculating step for calculating a distribution of the number of elements with respect to a CT value in cross-sectional data including a region of a biological part that reciprocates;
A range setting step for setting a CT value range based on a motion peak indicating motion of the living body part in the distribution, and
An area specifying method characterized by specifying an element area of the set CT value range as a living body part at a dead point of any of the reciprocating motions or a living body part region corresponding to a difference between them. In the distribution, the range setting step includes:
A lower limit setting step for setting a lower limit at the base of the side where the CT value of the air peak indicating air is larger;
An upper limit value setting step for setting an upper limit value at the base on the side where the CT value of the motion peak is large,
2. The region specifying method according to claim 1, wherein an element region of a CT value range determined by the set lower limit value and upper limit value is specified as a region of a living body part at the top dead center of the reciprocating motion. In the distribution, the range setting step includes:
A lower limit setting step for setting a lower limit at the base of the side where the CT value of the air peak indicating air is larger;
An upper limit value setting step for setting an upper limit value at the base on the side where the CT value of the motion peak is small,
The region specifying method according to claim 1, wherein an element region of a CT value range determined by the set lower limit value and upper limit value is specified as a region of a living body part at a bottom dead center of the reciprocating motion. In the distribution, the range setting step includes:
A lower limit setting step for setting a lower limit at the bottom of the side where the CT value of the motion peak is small;
An upper limit value setting step for setting an upper limit value at the base on the side where the CT value of the motion peak is large,
2. The region specifying method according to claim 1, wherein an element region of a CT value range determined by the set lower limit value and upper limit value is specified as a region of a living body part corresponding to the difference between the reciprocating motions.   The region specifying method according to claim 1, wherein the living body part is a lung.   The region specifying method according to any one of claims 1 to 4, wherein the living body part is a heart.   A volume measuring method, comprising: measuring a volume by three-dimensionally integrating the regions specified using the region specifying method according to claim 1. An area specifying device for specifying an area of a living body part in volume data by X-ray CT,
In cross-sectional data including a region of a biological part that reciprocates, a distribution calculation unit that calculates a distribution of the number of elements with respect to a CT value;
An operation unit that receives an operation of setting a CT value range in the distribution;
A setting correction unit that corrects the upper limit value or the lower limit value to a position that takes a minimum value in the skirt when an operation for setting an upper limit value or a lower limit value is received at the skirt of the movement peak indicating the movement of the living body part; With
An area specifying device that specifies an element area of the set CT value range as a living body part at a dead point of any of the reciprocating motions or a region of a living body part corresponding to a difference between them. An area specifying device for specifying an area of a living body part in volume data by X-ray CT,
In cross-sectional data including a region of a biological part that reciprocates, a distribution calculation unit that calculates a distribution of the number of elements with respect to a CT value;
A range setting unit configured to set a CT value range based on a motion peak indicating motion of the living body part in the distribution;
An area specifying device that specifies an element area of the set CT value range as a living body part at a dead point of any of the reciprocating motions or a region of a living body part corresponding to a difference between them. A time change calculation unit for calculating a time change of the integrated CT value within the set ROI using the volume data obtained by the fluoroscopic function;
An adjustment unit that adjusts X-ray CT imaging when a duty ratio indicating one dead center side of the reciprocation is less than or equal to a predetermined ratio in the time variation; The area specifying device according to claim 8 or 9. An area specifying program for specifying an area of a living body part in volume data by X-ray CT,
A distribution calculation process for calculating a distribution of the number of elements with respect to a CT value in cross-sectional data including a region of a living body part that reciprocates;
In the distribution, an operation reception process for receiving an operation for setting a CT value range;
A setting correction process for correcting the upper limit value or the lower limit value to a position where the minimum value is taken in the base when an operation for setting an upper limit value or a lower limit value is accepted at the base of the motion peak indicating the motion of the living body part; , Letting the computer execute
An area specifying program that specifies an element area of the set CT value range as a living body part at one of the dead points of the reciprocating motion or a region of a living body part corresponding to a difference between them. An area specifying program for specifying an area of a living body part in volume data by X-ray CT,
A distribution calculation process for calculating a distribution of the number of elements with respect to a CT value in cross-sectional data including a region of a living body part that reciprocates;
In the distribution, by causing a computer to execute a range setting process for setting a CT value range based on a motion peak indicating the motion of the living body part,
An area specifying program that specifies an element area of the set CT value range as a living body part at one of the dead points of the reciprocating motion or a region of a living body part corresponding to a difference between them.

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