JP4801567B2 - Volume data processing apparatus and volume data processing program - Google Patents

Description

  The present invention relates to a volume data processing apparatus and volume data processing program for processing volume data obtained for a subject.

  2. Description of the Related Art Conventionally, a technique for specifying a position inside a subject using volume data such as CT, MR, and PET is known. Such a built-in position is identified by capturing and marking a physical feature that is apparent from the outer shape of the subject at the time of imaging. In particular, when the subject is a human, the sphenoid bone, the tip of the sciatic bone, the xiphoid process, etc. are often the targets of marking.

  In such a positioning technique when the subject is a human, a technique based on a bone image obtained by CT imaging has been developed (for example, Non-Patent Document 1). In order to extract a bone region, the positioning support system of Non-Patent Document 1 sets a CT value of a bone as a threshold, performs a feature amount extraction process, and targets tomographic data perpendicular to the obtained body axis as reference image data. The amount of deviation from the image data is calculated by a correlation function.

On the other hand, in recent years, demand for X-ray CT imaging of laboratory animals has increased. For such experimental animals, there is a case where changes in internal organs and fat are observed over time, and in this case, it is necessary to continue observation in the same region. Therefore, the position specifying technology such as built-in becomes important. An X-ray CT apparatus for laboratory animals has been developed that can complete imaging in only a few tens of seconds, and the burden on laboratory animals due to imaging is significantly reduced. As a result, it is possible to perform CT imaging of a specific individual many times, and the application is expanding.
Yokomine, “Development and examination of positioning support system using CT images in radiation therapy”, Journal of Japanese Society for Radiological Technology, April 2005, Vol. 61, No. 4, 521 pages

  However, there are cases in which the experimental animal has a short body length or is covered with body hair and its external shape is difficult to understand, and it is difficult to specify the position of an organ or the like from the appearance in advance. Even if the epidermis is marked with a marking pen or the like, the reproducibility of the position specification is impaired due to obstruction of body hair or expansion / contraction of the skin. As a result, the reliability of the calculated feature amount such as the body fat amount is lowered.

  Even if the CT value of the bone is used as a positioning reference, it takes time and labor for the user to determine the region of interest while viewing the image, which is a heavy burden. In addition, when the system described in Non-Patent Document 1 is used, the burden of processing is large, and it takes time to obtain the results. It is not suitable for processing. Moreover, since the above system uses image data of a plane perpendicular to the body axis, the user needs to narrow down the position in the body axis direction in advance.

  The present invention has been made in view of such circumstances. A volume data processing apparatus and a volume data processing program that can improve the reproducibility for specifying a measurement range and can objectively and easily calculate a feature amount. The purpose is to provide.

  (1) In order to achieve the above object, the volume data processing device according to the present invention is based on the volume data, and the measurement included in the numerical range representing the bone on a specific plane parallel to the body axis of the subject. A profile calculation unit that calculates a line profile of values, a region setting unit that sets a region of interest based on a local maximum or minimum position of the line profile, and a feature amount calculation unit that calculates a feature amount for the region of interest. It is characterized by providing. The measured value here is a value representing the nature of the tissue at each position, such as a CT value or an MR concentration value.

  Since the volume data processing apparatus of the present invention sets the region of interest based on the position where the line profile takes the maximum value or the minimum value, the region of interest can be set with high reproducibility for one subject. That is, it is possible to set a region for the same subject at the same position as the previous processing. In addition, the complexity of manually setting the region of interest can be eliminated, and the user's subjectivity can be eliminated. As a result, when the measurement is continuously performed on the experimental animal, an objective calculation result of the feature amount can be obtained. Further, since the position is specified by the bone, the position is specified more objectively and the reproducibility of the region setting is enhanced as compared with the case where the position is specified by the skin or the appearance. The line profile represents a relationship between a position on a line along a planar spinal column parallel to the body axis and a measured value.

  (2) The volume data processing apparatus according to the present invention further includes an input unit that receives an input of a schematic position of the region of interest, and the region setting unit includes the outline of the maximum or minimum position of the line profile. The region of interest is set based on a position closest to the position.

  Thus, if the approximate position is designated, the region of interest is auto-fitted, so that the user can easily perform the measurement and the labor is reduced.

  (3) Further, the volume data processing apparatus according to the present invention includes a unique position specifying unit that specifies a unique position uniquely determined by the skeleton of the subject on the specific plane, the unique position and the line profile. A storage unit that stores position determination information that determines a position in association with the position determination unit, and the region setting unit sets the region of interest using the position determination information.

  Since the position of the region of interest is automatically set from the position unique to the subject, the measurement effort is reduced. If the position of the region of interest measured last time is stored as the region setting information, the region is automatically set even if the user forgets the position of the region of interest, and convenience is improved. Thus, an objective calculation result can be easily obtained for the feature amount.

  (4) Further, in the volume data processing device according to the present invention, the proper position specifying unit specifies the position of the thoracic vertebra as a specific position, and the region setting unit uses the position determination information based on the position of the thoracic vertebra. And setting the region of interest.

  There is a unique position for each subject that is always determined from the skeleton. Since the thoracic vertebra of the present invention is specified as described above and the region of interest is set based on the position determination information, the position of the region of interest can be set objectively and reliably.

  (5) Further, the volume data processing apparatus according to the present invention determines a position of a plane perpendicular to the body axis of the subject and suitable for use in determining the specific plane, and the body axis A spine center calculation unit that calculates the center of the spine on a plane perpendicular to the spine, and the profile calculation unit calculates a line profile on a plane passing through the spine center.

  As described above, the volume data processing apparatus of the present invention automatically calculates the center of the spinal column on a plane perpendicular to the body axis, and determines the plane for obtaining the line profile. Thereby, determination of a line profile can be automated and labor can be saved. In addition, it is good also as an aspect which presents a line profile determined automatically to a user as a candidate and corrects it if necessary.

  (6) Further, the volume data processing program according to the present invention calculates a line profile of measurement values included in a numerical range representing bone on a specific plane parallel to the body axis of the subject based on the volume data. A computer that includes: a profile calculation process that performs a region setting process that sets the region of interest based on a local maximum or minimum position of the line profile; and a feature amount calculation process that calculates the feature amount for the set region of interest. It is characterized by being executed.

  Since the volume data processing program of the present invention sets the region of interest based on the position where the maximum or minimum value of the line profile is taken, the region of interest can be set with high reproducibility for one subject. That is, it is possible to set a region for the same subject at the same position as the previous processing. In addition, the complexity of manually setting the region of interest can be eliminated, and the user's subjectivity can be eliminated. As a result, when the measurement is continuously performed on the experimental animal, an objective calculation result of the feature amount can be obtained. Further, since the position is specified by the bone, the position is specified more objectively and the reproducibility of the region setting is enhanced as compared with the case where the position is specified by the skin or the appearance.

  According to the present invention, a region of interest can be set with high reproducibility for one subject. That is, it is possible to set a region for the same subject at the same position as the previous processing. In addition, the complexity of manually setting the region of interest can be eliminated, and the user's subjectivity can be eliminated. As a result, when the measurement is continuously performed on the experimental animal, an objective calculation result of the feature amount can be obtained. Further, since the position is specified by the bone, the position is specified more objectively and the reproducibility of the region setting is enhanced as compared with the case where the position is specified by the skin or the appearance.

  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 conceptual diagram showing the configuration of the X-ray CT apparatus 5 and the volume data processing 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 volume data processing apparatus 10 is connected to the X-ray CT apparatus 5 and receives three-dimensional CT data (hereinafter referred to as volume data). The volume data processing apparatus 10 processes volume data and calculates a feature amount. The feature amount refers to, for example, fat mass or fat percentage. The above configuration is an example, and volume data targeted by the present invention includes MRI data, PET data, and the like in addition to X-ray CT data. Next, each part of the volume data processing apparatus 10 will be described in detail.

  FIG. 2 is a block diagram showing a functional configuration of the volume data processing apparatus 10. As shown in FIG. 2, the volume data processing apparatus 10 includes a transmission / reception unit 11, a storage unit 12, a control unit 13, a cross-section data formation unit 14, a display unit 15, an input unit 16, a profile calculation unit 17, an area setting unit 18, A feature amount calculating unit 19, a specific position specifying unit 20, a maximum value projecting unit 21, a spinal column center calculating unit 22, and a control bus N are provided. 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. Further, the storage unit 12 stores position determination information in association with the specific information of the subject. The subject specifying information is a sample number for specifying the subject. The position determination information is information for determining the set position of the region of interest using the unique position and the line profile. For example, the position determination information includes information indicating what number peak position between the unique position and what number peak position should be set as the region of interest. The peak position refers to a maximum or minimum position.

  The storage unit 12 stores recommended position determination information as default position determination information. Thus, even when the first process is performed on a certain subject, the region of interest setting candidate is presented to the user, which makes it easy to determine the region setting. The control part 13 is comprised by CPU and controls each part. For example, the control unit 13 reads volume data that is a target of feature quantity calculation from the storage unit 12.

  The cross-section data forming unit 14 forms cross-section data at the position specified for the volume data. The cross section 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 at the time of imaging. In that case, volume data whose body axis direction is determined in advance is obtained.

  The cross-section data forming unit 14 forms cross-section data at the default position or the position used last time in the first processing after the volume data processing apparatus 10 is started. When there is an instruction from the user via the input unit 16, the cross-section data forming unit 14 forms cross-sectional data at the instructed position. Further, when automatically setting a cross section for generating a line profile, the cross section data forming unit 14 sets a plane parallel to the body axis such as a sagittal plane and a coronal plane at the center of the spinal column. The cross-section data forming unit 14 is configured by a CPU.

  The display unit 15 displays volume data of each cross section. It is possible to display by color-coded according to the measured value. When a threshold value is set for the measured value, only the measured value within the threshold value range can be displayed by color-coded. The measured value is a value representing the nature of the tissue at each position, such as a CT value. The display unit 15 displays a line profile on a predetermined line of each cross section. For example, the measured value on the line indicating the coronal plane on the sagittal plane is displayed as a line profile. It is preferred to display the line profile along the spine center at the body axis or any axial plane. Note that not only a straight line such as a line indicating a coronal plane but also a line profile on a curve along the spinal column may be displayed. The display unit 15 includes a liquid crystal display, a CRT, or the like.

  The input unit 16 is, for example, a pointing device or a keyboard. The input unit 16 receives an input for moving or confirming a cursor for designating a cross-sectional position. The input unit 16 receives an input of the approximate position of the region of interest. For example, the approximate position of the region of interest is input by moving the pointer to a position determined by the user as appropriate by the mouse and double-clicking.

  The profile calculation unit 17 calculates a line profile of measurement values included in a numerical range representing bone on a specific plane parallel to the body axis of the subject. Specifically, based on the volume data, a measurement value in a numerical range representing a bone is calculated on a line along a body axis on a specific plane parallel to the body axis of the subject. As a result of the calculation, a relationship between each position in the body axis direction and the measured value, that is, a line profile is calculated. The spinal column of a living organism is usually curved forward or backward. The above-mentioned “specific plane parallel to the body axis of the subject” is preferably a sagittal plane so as not to be affected by this curvature. In addition, as a line for calculating a line profile in a specific plane, the central axis of the spinal column is preferable, but any line that crosses the spinal column in the vicinity of the start surface may be used. For example, a line indicating a coronal plane can be used as a line for calculating a profile. When the cross section is automatically set, the profile calculation unit 17 calculates a line profile on a plane passing through the spine column center.

  The region setting unit 18 sets a region of interest on the basis of a position closest to the approximate position designated by the user among the maximum or minimum positions of the measurement values on the line profile. For example, the start surface of the region of interest is set at the maximum or minimum position closest to the approximate position specified by the user, and the end surface of the region of interest is set based on the size of the region specified in advance. In this way, since the region of interest is set based on the position where the maximum or minimum value of the profile is taken, the region of interest can be set with high reproducibility for one subject. That is, it is possible to set an area at the same position as the previous time for the same subject. The end surface may be set at a predetermined distance from the start surface. Unless the experiment is performed for a long period of time, the relative position of the spinal column does not change greatly. Therefore, there is no problem even if the end surface is set at a predetermined position from the start surface.

  The start surface and the end surface are end surfaces of the region of interest, and the region of interest is between the two. The calculation of the feature amount starts from the start surface and ends on the end surface. Note that, when the region setting is performed automatically, the region setting unit 18 sets the region of interest using the position determination information based on the unique position such as the thoracic vertebra position and the profile. For example, the position of the peak or valley of the profile from the thoracic vertebra position is used as the position determination information, and the position where the region of interest is to be set is specified. As described above, the region of interest given as an example is a three-dimensional region, but may be a two-dimensional region. In the two-dimensional case, the feature amount is calculated in the region from the start line to the end line on the determined plane.

  The feature amount calculation unit 19 calculates a feature amount for the region of interest. For example, when calculating the amount of fat in the region, the fat region is integrated from the start surface to the end surface of the region of interest to calculate the volume of the entire fat region. It is also possible to calculate the body fat percentage by calculating the volume of the trunk in the region and dividing the fat mass. The starting surface is determined by determining the line on the sagittal surface.

  The specific position specifying unit 20 specifies a specific position uniquely determined by the skeleton of the subject on a specific plane such as a sagittal plane. The unique position is a unique position determined as the only position with respect to the subject. For the proper position, for example, the position of the thoracic vertebra closest to the waist is suitable. Since the thoracic vertebra is connected to the ribs and the maximum projection data on the sagittal plane shows that the thoracic vertebra is connected to the ribs, it can be identified as a unique position of the subject.

  The maximum value projection unit 21 projects the maximum measurement value in the projection path onto a plane parallel to the body axis of the subject. Thereby, the position of the rib and the thoracic vertebra to which the rib is connected are known. In addition, since the spine silhouette is obtained on a plane parallel to the body axis, the axial plane used for determining a specific plane can be easily determined.

  The spinal column center calculation unit 22 determines the position of the axial plane based on the maximum measurement value projected on the plane, and calculates the center of the spinal column on the axial plane. The criterion for determining the position of the axial surface does not need to be strict, and may be determined from, for example, an average value of the positions of the bones, or may be determined as a position where the ribs are detected. It is not necessary to determine precisely because the sagittal plane is not affected by the curvature of the spinal column if the profile calculation plane is used. As a method of calculating the center of the spinal column in the axial plane, for example, there is a method of calculating the center assuming an ellipse in contact with the spinal column region of the axial plane. Note that the spinal column center calculation unit 22 may determine the position of the axial plane used for determining a specific plane by a simpler method without referring to the maximum measurement value projected on the plane. . The profile calculation unit 17, the region setting unit 18, the feature amount calculation unit 19, the proper position specifying unit 20, the maximum value projection unit 21, and the spinal column center calculation unit 22 function by the CPU.

  In the configuration of the X-ray CT apparatus 5, it is preferable that the body axis direction, the coronal plane, and the sagittal plane are determined in advance, and the subject is set in accordance with the determined axis at the time of imaging. It is good also as determining a body axis by. This applies not only to the X-ray CT apparatus but also to an MRI apparatus or the like.

(Device operation)
Next, the operation of the volume data processing apparatus 10 configured as described above will be described. FIG. 3 is a flowchart showing the operation of the volume data processing apparatus 10 when manually specifying the approximate position of the region of interest.

  First, the volume data processing device 10 displays on the screen the cross-sectional images of the axial surface, sagittal surface, and coronal surface of the subject set as the bone threshold for the target volume data and the line profile thereof (step S1). The user refers to the tomographic image of the sagittal plane or coronal plane, determines an appropriate axial plane, and the volume data processing apparatus 10 accepts the determination operation (step S2). Next, the volume data processing apparatus 10 accepts a line determining operation for calculating a sagittal plane and a line profile (step S3). Specifically, the user performs a determination operation by placing the cross cursor on the center of the vertebral column in the axial plane image. The volume data processing apparatus 10 extracts the measured value in the numerical range representing the bone on the determined sagittal plane, and calculates the line profile on the line in the body axis direction (step S4).

  Then, the volume data processing apparatus 10 presents the selection of the guide function to the user, and determines the user's selection (step S5). If the volume data processing apparatus 10 determines that the user has not selected the guide function, the volume data processing apparatus 10 accepts designation of the region of interest by a complete manual operation (step S6) and proceeds to step S9. On the other hand, if it is determined that the user has selected the guide function, the volume data processing apparatus 10 accepts designation of the approximate position by the user (step S7). The designation of the approximate position is performed, for example, when the user moves the pointer to an approximate position and double-clicks the mouse.

  Then, the volume data processing device 10 sets a region of interest based on the maximum or minimum position of the line profile closest to the above approximate position (step S8). For example, the end face of the region of interest is matched with the maximum or minimum position. As a result, it is possible to eliminate the trouble of manually setting the region of interest to a fine detail and to eliminate the user's subjectivity. As a result, when the measurement is continuously performed on the experimental animal, an objective calculation result of the feature amount can be obtained.

  Note that the region of interest may be set at a position determined based on the position of the maximum or minimum, without the end face of the region of interest completely matching the position of the maximum or minimum. When the region of interest is set in this manner, a feature amount such as a fat amount is calculated for the region of interest (step S9), and the process ends. As described above, the volume data processing apparatus 10 specifies the position by the bone, so that the position specification becomes objective and the reproducibility of the region setting is enhanced as compared with the case of specifying the position by the skin or the appearance.

  The setting of the sagittal plane and the setting of the region of interest will be described from the viewpoint of the user interface. FIG. 4 is a diagram showing a display screen for displaying each cross section and profile. When the volume data processing apparatus 10 reads the volume data of the subject to be examined, the volume data processing apparatus 10 displays the axial plane image 31, the coronal plane image 32, and the sagittal plane image 33 in the window 30 on the screen (display unit 15). The area on the left side of the window 30 is an operation area. Initially, images of three tomographic planes are displayed with a predetermined setting.

  The user can determine an appropriate axial plane by adjusting the axial plane cursor 31 a of the coronal plane image 32 or the sagittal plane image 33. The determined axial plane is newly displayed in the window 30 as the axial plane image 31. In the axial plane image 31, when the cross cursor is aligned with the center of the spinal column region 41, the coronal plane cursor 32 a and the sagittal plane cursor 33 a are set at positions passing through the center of the spinal column region 41. In addition, since it is sufficient if the sagittal plane can be specified, only the sagittal plane cursor 33a may be matched. In this way, the sagittal plane is determined.

  In this way, in the determined sagittal plane image 33, for example, the measurement value on the straight line of the coronal plane cursor 32a is displayed as the line profile 48. The user designates the approximate position of the start plane cursor 50 in the region of interest by double-clicking on a point on the screen of the sagittal plane image 33. The volume data processing device 10 corrects the position of the start surface cursor 50 to the maximum or minimum position of the line profile 48 closest to the designated position. The end surface is also corrected to a predetermined maximum or minimum position. Note that the size of the region of interest is set in advance, and the end surface cursor 51 may be determined in conjunction with the setting of the start surface cursor 50. In this way, the region of interest is set.

  FIG. 5 is a diagram illustrating an example of the region of interest setting operation using the line profile 48. For example, when the user designates the position 50a by double-clicking as the position of the start surface cursor 50, the start surface of the region of interest is automatically set to the nearest maximum position 50b. When the user designates the position 50c as the position of the start surface cursor 50 by double-clicking, the start surface of the region of interest is automatically set to the nearest minimum position 50d. Note that the cursor may be set to move only to either the maximum position or the minimum position in advance.

  In the above operation example, the user manually designates the approximate position of the region of interest, but the region of interest can be set without the user's designation. FIG. 6 is a flowchart showing an example of the operation of the volume data processing apparatus 10 when the region of interest is automatically set. In addition to this, there is a method of applying a labeling processing technique. Here, the method will be described with reference to the drawings. First, the volume data processing apparatus 10 inputs information for specifying the subject input by the user (step T1). The information for specifying the subject is, for example, a sample number. Thus, by determining the information for specifying the subject, the position determination information stored in association with the subject specifying information can be read, and the same region as the previous time can be set. Become.

  The volume data processing device 10 displays on the screen cross-sectional images of the axial, sagittal, and coronal planes of the subject's bone threshold for the target volume data (step T2). The user refers to the tomographic image of the sagittal plane or the coronal plane, determines an axial plane suitable for determining the sagittal plane, and the volume data processing apparatus 10 receives the determination operation (step T3). Next, the volume data processing apparatus 10 accepts a sagittal plane determination operation (step T4).

  The volume data processing apparatus 10 extracts the measured value in the numerical range representing the bone on the determined sagittal plane, and calculates a line profile for the line indicating the coronal plane (step T5). The line for calculating the line profile is not necessarily a line indicating the coronal plane, but is preferably a line along the body axis direction and near the center of the spinal column. The line must be within a range where a bone profile can be obtained at least from the thoracic vertebra to the region of interest. Next, a maximum value projection process on the sagittal plane is performed on the volume data (step T6). In the data subjected to the maximum value projection processing, when the measurement value within the range of the bone is extracted, it can be seen that the thoracic vertebra is connected to the rib. Then, two straight lines in the body axis direction are set in a range crossing the ribs, and a line profile on the straight lines is calculated. The line profile is maximal at the rib position. Of the local maximum values of the line profile, the local maximum position closest to the waist is calculated for each straight line (step T7), and the position of the intersection of the straight line connecting the two local maximum positions and the line indicating the coronal plane is calculated. . Since the rib extends linearly from the thoracic vertebra, the position of the intersection is the estimated position of the thoracic vertebra (step T8). And in the line profile on the line which shows a coronal surface, the local maximum position nearest from the position of said intersection is calculated. This local maximum position is a unique position (step T9). The unique position may be the position of the thoracic vertebra closest to the waist as described above, but may be any other position as long as the position is unique to the subject.

  Next, the volume data processing apparatus 10 determines whether or not the process for the subject specified by the specific information is performed for the second time or later (step T10). When it is determined that the process is the first, the volume data processing apparatus 10 performs a default area setting (step T11). For example, when subject specifying information is input, it is stored in association with information recommended as position determination information corresponding to the subject specifying information. Then, according to the position determination information, the region of interest is automatically set from the unique position and the profile (step T12).

  The volume data processing apparatus 10 confirms with the user whether the set region of interest is acceptable by default setting (step T13). If there is an answer that the set item is not satisfactory, the user receives designation of the approximate position of the region of interest (step T14). Then, the volume data processing device 10 sets a region of interest based on the maximum or minimum position of the line profile closest to the above approximate position (step T15). The volume data processing apparatus 10 stores the position determination information of the set region of interest (step T16), and proceeds to step T19. On the other hand, if there is an answer from the user that the region of interest set by default is satisfactory, the process proceeds directly to step T19.

  If it is determined in step T10 that the process is the second or subsequent process, position determination information is read based on the subject specific information (step T17), and the interest is determined using the specific position and profile according to the position determination information. An area is set (step T18). Thus, since the position of the region of interest is automatically set from the position unique to the subject, the measurement effort is reduced. In addition, if the position of the region of interest measured last time is stored as region setting information, the region is automatically set even if the measurer forgets the position of the region of interest, which improves user convenience. Finally, the feature amount in the region of interest is calculated (step T19), and the process ends.

  A method of automatically determining a region of interest using the above-described unique position, line profile, and position determination information will be specifically described. FIG. 7 is a diagram showing a sagittal screen image obtained by performing maximum value projection processing on volume data. As shown in FIG. 7, ribs 90 to 98 are connected to cervical vertebrae 70 to 78 among cervical vertebrae 70 to 84. From these skeletal features, the cervical vertebrae 70-78 are known to be thoracic vertebrae, and can be distinguished from the cervical vertebrae 79-84. In order to determine the position of the thoracic vertebrae, first, straight lines 100 and 101 in opposite directions are taken so as to cross the ribs 90 to 98. Then, line profiles 103 and 104 are calculated for the straight lines 100 and 101, and maximum positions 106 and 107 closest to the waist are calculated. Then, an intersection 108 between a straight line connecting the two maximum positions and a straight line (for example, a line indicating a coronal plane) taken to separately calculate a line profile of the spinal column is calculated. The position A0 in the opposite axis direction of the intersection 108 can be estimated as the position of the thoracic vertebra closest to the waist. Next, a method for setting the position of the region of interest using the estimated thoracic vertebra position A0 will be described.

  FIG. 8 is a diagram showing a sagittal plane image displayed with a bone threshold. As shown in FIG. 8, each cervical vertebra 70 to 84 corresponds to the maximum position of the line profile 48 for the line indicating the coronal plane. The maximum positions include positions B0 to B6. In the position line profile 48, the maximum position B0 closest to the position A0 of the thoracic vertebra estimated in the above process is extracted and set as a natural position. This unique position B0 is the position of the thoracic vertebra closest to the waist.

  For example, if the region of interest for which the feature amount has been calculated before is between the cervical vertebra 83 and the cervical vertebra 84, the region of interest is a region sandwiched between the fifth and sixth peaks from the unique position B0. Is stored in the storage unit 12 as position determination information. When the feature amount is calculated again for the same region for the same subject, the volume data processing apparatus 10 reads the position determination information from the storage unit 12, and the maximum position B 5 and the maximum position B 6 calculated from the unique position B 0 and the profile 48. Can be set to the region of interest 110. By setting the region of interest in the region thus identified, it is possible to automatically set the region of interest with high reproducibility. Further, since the bone position is used as a reference, the profile characteristics hardly change over time. Therefore, a highly reliable result can be obtained, for example, when an experiment is conducted following changes in fat mass.

  As a method for calculating the unique position, there is a method using a labeling process other than the above example. In this method, first, the rib closest to the lumbar vertebra is identified from the line profile crossing the rib in the data obtained by projecting the maximum value of the volume data onto the sagittal plane. Then, labeling processing is performed on the data projected with the maximum value. The labeling process can identify the ribs and the thoracic vertebrae connected to the ribs. As a result, the region of the thoracic vertebra connected to the rib closest to the lumbar vertebra can be identified. On the other hand, in the cross-sectional data of the sagittal plane, a line profile along the spinal column is calculated, and the maximum position of the line profile is calculated in the region of the thoracic vertebra closest to the waist specified as described above. This local maximum position can be set as a specific position. As described above, there are various methods for specifying the thoracic vertebra or a specific position unique to the subject, and the present invention is not limited to the method using only the profile.

  In the above operation example, the sagittal plane is determined manually, but this may be performed automatically. In that case, first, the volume data processing device 10 projects the maximum measured value in the projection path onto a plane parallel to the body axis of the subject. Then, based on the maximum measurement value projected on the plane, the position of the axial plane used for determining the specific plane is determined, and the center of the spinal column is calculated on the axial plane. Note that the position of the axial plane used for determining a specific plane may be determined by a simpler method without referring to the maximum measurement value projected on the plane.

It is a conceptual diagram which shows the structure of a X-ray CT apparatus and a volume data processing apparatus. It is a block diagram which shows the functional structure of the volume data processing apparatus which concerns on this invention. It is a flowchart which shows operation | movement of the volume data processing apparatus concerning this invention. It is a figure which shows the display screen which displays each cross section and profile. It is a figure which shows an example of the setting operation | movement of the region of interest using a line profile. It is a flowchart which shows operation | movement of the volume data processing apparatus concerning this invention. It is a figure which shows the sagittal screen image which carried out the maximum value projection process of the volume data. It is a figure which shows the sagittal surface image displayed with the threshold value of the bone.

Explanation of symbols

5 X-ray CT apparatus 10 Volume data processing apparatus 11 Transmission / reception part 12 Storage part 13 Control part 14 Cross-section data formation part 15 Display part 16 Input part 17 Profile calculation part 18 Area setting part 19 Feature value calculation part 20 Eigenlocation specifying part 21 Maximum Value projection unit 22 Spinal center calculation unit 30 Window 31 Axial plane image 31a Axial plane cursor 32 Coronal plane image 32a Coronal plane cursor 33 Sagittal plane image 33a Sagittal plane cursor B0 Thoracic spine position (unique position)
110 Area of interest

Claims (6)

A profile calculation unit that calculates a line profile of measurement values included in a numerical range representing bone on a specific plane parallel to the body axis of the subject based on the volume data;
A region setting unit for setting a region of interest based on the local maximum or minimum position of the line profile;
A volume data processing apparatus comprising: a feature amount calculation unit that calculates a feature amount for the region of interest. An input unit that receives an input of the approximate position of the region of interest;
The volume data processing apparatus according to claim 1, wherein the region setting unit sets the region of interest based on a position closest to the approximate position among the maximum or minimum positions of the line profile. A specific position specifying unit that specifies a specific position uniquely determined by the skeleton of the subject on the specific plane;
A storage unit for storing position determination information for determining a set position of a region of interest using the unique position and the line profile;
The volume data processing apparatus according to claim 1, wherein the region setting unit sets the region of interest using the position determination information. The specific position specifying unit specifies the position of the thoracic vertebra as a specific position,
The volume data processing apparatus according to claim 3, wherein the region setting unit sets the region of interest based on the position of the thoracic vertebra using the position determination information. Determine the position of a plane perpendicular to the body axis of the subject and suitable for use in determining the specific plane, and calculate the center of the spine on the plane perpendicular to the body axis And further comprising,
5. The volume data processing apparatus according to claim 1, wherein the profile calculation unit calculates a line profile on a plane passing through the spinal column center. Profile calculation processing for calculating a line profile of measurement values included in a numerical range representing bone on a specific plane parallel to the body axis of the subject based on the volume data;
A region setting process for setting a region of interest based on the local maximum or minimum position of the line profile;
A volume data processing program for causing a computer to execute a feature amount calculation process for calculating a feature amount for the region of interest .