JP5329149B2 - Cerebral sulcus position specifying method, image processing apparatus, and medical image diagnostic apparatus - Google Patents

Description

  The present invention can implement the sulcus position specifying method for specifying the position of the sulcus of the brain using an image related to the brain of the subject imaged by the X-ray CT apparatus, and the sulcus position specifying method can be implemented. The present invention relates to an image processing apparatus and a medical image diagnostic apparatus equipped with the image processing apparatus.

  2. Description of the Related Art In recent years, medical image diagnostic apparatuses that collect information inside a subject and generate a medical image by imaging the inside of the subject based on the collected information have been used. Examples of the medical image diagnostic apparatus include an X-ray CT apparatus (computed tomography) and a magnetic resonance diagnostic apparatus (MRI). The generated medical image is displayed on these medical image diagnostic apparatuses.

  Although there are various conditions regarding whether or not these medical image diagnostic apparatuses can be used, for example, since the head (brain) of the subject can be presented as an image, a report is created by a diagnosis or an interpreter Shows great power when performing. Furthermore, for example, it is useful when research on the brain field and pathology of a subject in fields such as neurology, brain surgery, and brain science is performed. In particular, the position of the cerebral sulcus is often used as a clue when making a diagnosis or the like and for distinguishing between the brain areas.

  In order to image and display the inside of the brain, MRI that can clearly represent the shape of the brain is often used. On the other hand, in the X-ray CT apparatus, although it can represent the shape of the brain, imaging is performed while suppressing adverse effects such as exposure to the subject as low as possible, and therefore there is a portion lacking in clarity of the image.

  The following invention is disclosed in Patent Document 1 shown below as one method for eliminating the shading of an image captured using an X-ray CT apparatus.

In the invention described in Patent Document 1, an index such as CBP that quantitatively represents the blood flow dynamics of capillaries in brain tissue by effectively suppressing noise while suppressing a decrease in spatial and temporal resolution using a coherent filter. Is calculated with high accuracy. This improves the analysis accuracy of the CPB study.
JP 2008-100121 A

  However, MRI has an adverse effect that, for example, a subject in which a pacemaker is embedded or a subject wearing metal or the like cannot be inspected, and measurement takes time.

  The invention disclosed in Patent Document 1 is useful for a method for quantitatively representing blood flow dynamics of capillaries in brain tissue called the CBP study described above. Is not appropriate.

  Even an image taken by an X-ray CT apparatus can be sharpened by a method different from the invention described in Patent Document 1, but for example, setting of conditions for sharpening is handled by the apparatus. The portion that depends on the skill of an engineer or the like is large, and this has caused variations in the sharpness of the image displayed by the operator.

  In addition, since the image taken by the X-ray CT apparatus is unclear, when displaying the sulcus, a substantial part of the brain excluding the skull in the brain of the subject displayed as the sulcus (hereinafter referred to as this part). Are expressed as “brain parenchyma”), and it is difficult to extract only a specific sulcus from the entire image.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to sharpen an image photographed by an X-ray CT apparatus by a simple operation and to accurately locate a specific cerebral groove. It is an object of the present invention to provide a sulcus position specifying method, an image processing apparatus, and a medical image diagnostic apparatus that can be extracted and specified.

  According to a first aspect of the present invention, there is provided a method for creating three-dimensional brain volume data using a CT image acquired by photographing a head of a subject in a method for specifying a position in the sulcus, Creating X-ray absorption amount data representing the X-ray absorption amount of the brain surface portion of the subject based on the data, and creating brain surface position data representing the position of the brain surface of the subject based on the brain volume data And a step of searching for the position of the sulcus using the X-ray absorption amount data and the brain surface position data, and creating a sulcus region map by positioning the searched sulcus position on the brain surface of the subject. Steps.

  According to a tenth aspect of the present invention, in the image processing apparatus, a means for creating three-dimensional brain volume data using a CT image acquired by imaging the subject's brain, and the brain volume data are used. X-ray absorption amount data creating means for creating X-ray absorption amount data representing the subject's brain surface in two dimensions, and brain surface position data representing the subject's brain surface with brightness brightness based on the brain volume data. Using the brain surface position data creation means to be created, the X-ray absorption amount data created by the X-ray absorption data creation means, and the brain surface position data created by the brain surface position data creation means, the position of the cerebral groove is determined. A sulcus searching means for searching and a sulcus region map creating means for positioning the position of the sulcus searched by the sulcus searching means on the brain surface of the subject.

  According to a twelfth aspect of the present invention, in the medical image diagnostic apparatus, an X-ray tube, an X-ray detector that receives X-rays irradiated from the X-ray tube and passed through the subject, and an X-ray detector are generated. An image generation means for forming an image of the subject from the electrical signal, means for creating three-dimensional brain volume data using a CT image relating to the brain of the subject generated by the image generation means, and brain volume data X-ray absorption amount data creating means for generating X-ray absorption amount data representing the subject's brain table in two dimensions based on the brain volume, and the brain surface position representing the brain table of the subject with brightness contrast based on the brain volume data Using brain surface position data creating means for creating data, X-ray absorption data created by X-ray absorption data creating means, and brain surface position data created by brain table position data creating means A sulcus searching means for searching for a sulcus position; and a sulcus region map creating means for positioning the sulcus position searched by the sulcus searching means on the brain surface of the subject. .

  According to the present invention, a cerebral sulcus position specifying method and an image processing apparatus that can sharpen an image photographed by an X-ray CT apparatus by a simple operation and can accurately extract and specify a specific sulcus position. In addition, a medical image diagnostic apparatus can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Internal configuration of medical image diagnostic apparatus]
FIG. 1 is a block diagram showing an internal configuration of a medical image diagnostic apparatus 1 according to an embodiment of the present invention. There are various medical image diagnostic apparatuses such as the above-described MRI. In the embodiment of the present invention, an X-ray CT apparatus will be described as an example of the medical image diagnostic apparatus 1 below.

  In the medical image diagnostic apparatus 1, a CPU (Central Processing Unit) 1a, a ROM (Read Only Memory) 1b, a RAM (Random Access Memory) 1c, and an input / output interface 1d are connected via a bus 1e. Input / output interface 1d is connected to input means 1f, display means 1g, communication control means 1h, storage means 1i, removable disk 1j, and drive unit control means 1k. The drive unit control unit 1k includes, for example, a drive unit 11 such as an X-ray tube constituting the X-ray CT apparatus and an X-ray detector that receives X-rays, and is controlled by the drive unit control unit 1k. Further, the image processing apparatus 10 is also connected via the input / output interface 1d.

  The CPU 1a reads out and executes a boot program for starting the medical image diagnostic apparatus 1 from the ROM 1b based on an input signal from the input unit 1f, and reads out various operating systems stored in the storage unit 1i. The CPU 1a controls various devices based on input signals from other external devices not shown in FIG. 1 via the input means 1f and the input / output interface 1d. Further, the CPU 1a reads a program and data stored in the RAM 1c, the storage unit 1i, and the like, loads them into the RAM 1c, and performs a series of image processing, data calculation, processing, and the like based on the program commands read from the RAM 1c. It is a processing apparatus which implement | achieves the process of.

  The input unit 1 f is configured by an input device such as a keyboard and a dial for an operator (for example, a doctor or a laboratory technician) of the medical image diagnostic apparatus 1 to input various operations, and an input signal based on the operation of the operator Is transmitted to the CPU 1a via the bus 1e. The medical image diagnostic apparatus 1 is provided with a dedicated operation panel as well as a keyboard and the like, and an operation screen can be operated via an input device on the operation panel. The display means 1g is a liquid crystal display, for example. The display means 1g receives an output signal from the CPU 1a via the bus 1e and, for example, an image necessary for setting the ROI for provisional shooting and various conditions for the main shooting, or the processing of the CPU 1a. Display the results.

  The communication control unit 1h is a unit such as a LAN card or a modem, and is a unit that enables the medical image diagnostic apparatus 1 to be connected to a communication network such as the Internet or a LAN. Data transmitted / received to / from the communication network via the communication control unit 1h is transmitted / received to / from the CPU 1a via the input / output interface 1d and the bus 1e as an input signal or an output signal.

  The storage means 1i is composed of a semiconductor or a magnetic disk, and stores programs and data executed by the CPU 1a.

  The removable disk 1j is an optical disk or a flexible disk, and signals read and written by the disk drive are transmitted to and received from the CPU 1a via the input / output interface 1d and the bus 1e.

  The image generating unit 1m generates an image of the subject from an electrical signal generated by an X-ray detector that detects X-rays that are irradiated from the X-ray tube and transmitted through the subject.

  The image processing apparatus 10 is connected to the input / output interface 1d, and sharpens the image of the subject generated by the image generating unit 1m so that the position of the sulcus can be specified.

  In the embodiment of the present invention, an example in which the image processing apparatus 10 is mounted on the medical image diagnostic apparatus 1 will be described below. The image processing apparatus 10 is independent of the medical image diagnostic apparatus 1. It may exist and be connected to the medical image diagnostic apparatus 1 via a communication network. In this case, the image processing apparatus 10 further includes, for example, a hospital information management system (HIS), a radiological information management system (RIS), a medical image management system (PACS). It may be used in combination with various management systems constructed in a medical institution. Examples of this communication network include networks such as a LAN (Local Area Network) and the Internet. The communication standard used in this communication network may be any standard such as DICOM (Digital Imaging and Communication in Medicine).

  Further, the image processing is performed in the medical image diagnostic apparatus 1, but the processing is not performed by the image processing apparatus 10, but by using the sulcus position specifying program stored in the storage unit 1i or the removable disk 1j. You can also. In this case, the cerebral sulcus position specifying means is mounted on the medical image diagnostic apparatus 1 by reading and executing the programs stored in the CPU 1a.

[Internal configuration of image processing apparatus]
FIG. 2 is a block diagram showing the overall configuration of the image processing apparatus 10 according to the embodiment of the present invention. The image processing apparatus 10 includes a medical examination means 11, a volume data creation means 12, an X-ray absorption amount data creation means 13, a brain surface position data creation means 14, a sulcus search means 15, and a sulcus region map creation means. 16 and transmission means 17.

  The volume data creation unit 12 creates three-dimensional brain volume data, which is a material for creating a sulcus region map, using an X-ray CT image taken by the medical image diagnostic apparatus 1. The X-ray absorption amount data creation means 13 and the brain surface position data creation means 14 create projection images or brain surface position data, respectively, using the brain volume data created by the volume data creation means 12. Here, “X-ray absorption amount data” is data indicating CT values and the like, and using this X-ray absorption amount data, the brain of the subject represented by the three-dimensional brain volume data is given. A two-dimensional planar image showing a state viewed from the direction is hereinafter referred to as a “projection image” for convenience. “Brain surface position data” refers to an image that is displayed based on a luminance value for each pixel that displays the brain surface according to the distance from a predetermined reference position to the brain surface. Point to.

  The sulcus searching means 15 is a means for searching for a sulcus required by the operator using the created projection image and brain surface position data. Furthermore, the sulcus region map creating means 16 displays the searched sulcus in a predetermined position on the projection image or brain surface position data so that it can be displayed as a map.

  Next, the flow of creating and displaying a sulcus region map using the image processing apparatus 10 will be described below using a plurality of flowcharts as appropriate. First, after explaining the rough flow using the flowchart of FIG. 3, the detailed contents of each step will be explained.

[Flow of creating sulcus region map]
FIG. 3 is a flowchart showing a rough flow of creating and displaying a sulcus region map. In order to create a sulcus region map, first, an X-ray CT image of the head of a person who is the subject is captured using an X-ray CT apparatus (ST1). Imaging is performed by the drive unit control unit 1k driving the drive unit 11 such as an X-ray tube or an X-ray detector based on an instruction from the CPU 1a of the medical image diagnostic apparatus 1.

  Using the photographed X-ray CT image, three-dimensional volume data about the brain parenchyma is created (ST2), and a projected image of the brain surface and brain surface position data are created based on the three-dimensional volume data (ST3). ). The created projection image and brain surface position data are used to search for the position of the desired sulcus of the subject (ST4), and the searched sulcus is displayed (ST5). The cerebral sulcus position may be displayed by displaying only the searched cerebral sulcus or superposed (fused) with a separately created head perfusion image.

[Create 3D volume data]
FIG. 4 is a flowchart showing a flow (ST2) in which the volume data creating means 12 of the image processing apparatus 10 creates three-dimensional volume data for the brain parenchyma. The image that is the basis for creating the three-dimensional volume data is an image taken by the X-ray CT apparatus as described above. An image obtained by photographing is a three-dimensional image. First, an operation for sharpening the image is performed (ST21).

  In CT images, it is said that the standard deviation (sd) of noise is inversely proportional to the square root of the irradiation X-ray dose. Therefore, when the sharpness (S / N ratio) necessary for specifying the position of the sulcus is obtained, a very large amount of X-ray is required, and the amount of exposure of the subject is significantly increased. In addition, if the shooting pitch is set finely to obtain a detailed image of the brain parenchyma, the same spot will be shot over many times and the amount of exposure at the shooting spot will be much higher than in normal shooting. . For this reason, imaging is performed by reducing the amount of X-rays compared to normal imaging, but this time, the required sharpness (S / N ratio) cannot be obtained.

  Therefore, in order to ensure clearness (increase the S / N ratio), for example, a plurality of volume data photographed at a specified time is added and an average is obtained. By performing such an operation, sharp three-dimensional volume data is created. In addition, if a clear image is obtained from the beginning, such a process is not required and the obtained three-dimensional image can be used as it is.

  On the other hand, a process of extracting only the brain parenchyma using the photographed three-dimensional volume data is performed (ST22). In other words, the captured X-ray CT image shows a skull in addition to the brain parenchyma. Since only the brain parenchyma is displayed when displaying the cerebral sulcus, the unnecessary skull is removed from the image and only the brain parenchyma is extracted.

  Specifically, for example, paying attention to the fact that the CT value when displaying the three-dimensional volume data is different (the CT value is different between the bone (cranium) and the brain parenchyma), and it is sharpened using the threshold value of this CT value. A code is assigned to each region in the three-dimensional volume data (labeling is performed). Then, only necessary areas (brain parenchyma areas) are selected and displayed. By performing such processing, the skull can be removed from the three-dimensional volume data. However, even if only the brain parenchyma region is extracted, a portion indicating a blood vessel or the like remains in the region, so that a mask indicating the brain parenchyma region is created by performing a process such as expansion / reduction processing.

  After that, the sharpened three-dimensional volume data created in step 21 is overlapped with the mask indicating the brain parenchymal area created in step 22, and the overlapping area is extracted (ST23). By performing this processing, it is possible to obtain three-dimensional volume data that can represent a clear image of the necessary brain parenchyma while the skull is removed (ST24).

[Create projection image, Noh table position data]
Next, using the three-dimensional volume data created through such processing, a projected image of the brain and brain surface position data are created (ST3). Here, the “projection image” is a two-dimensional planar image showing the state of the subject's brain viewed from a certain direction from the three-dimensional volume data. The “brain surface position data” is an image represented by the density of CT values according to the distance from the reference position to the brain surface. In the embodiment of the present invention, the brain table located far from the reference position is displayed in black (dark), and the brain table positioned close to the reference position is displayed in white (bright). Furthermore, the two types of images, the projection image and the brain surface position data, were created because the exact position of the sulcus was grasped from only one of the images when searching for the sulcus. This is because it becomes difficult.

  First, creation of a “projection image” will be described below with reference to the chart of FIG. 5 and FIG. Here, FIG. 6 is a diagram showing the three-dimensional volume data by the X axis, the Y axis, and the Z axis. For convenience, the Y axis is taken as the horizontal axis and the Z axis is taken as the vertical axis. It is shown extending from the front toward the back.

  The X-ray absorption data creation means 13 searches for the position of the brain surface based on the three-dimensional volume data of the brain parenchy created in Step 2 described above (ST31). That is, when creating a projection image of the subject's brain viewed from above, for example, a virtual XY plane is set on the three-dimensional volume data, and the set XY plane is used as a reference. A line is drawn (stretched) in the -Z direction from the plane. When the line is extended from the reference position in this way, the position of the surface of the brain (brain surface) on the three-dimensional volume data can be searched for by changing the CT value. Since these lines are extended over the entire surface of the XY plane, the region where the three-dimensional volume data is present is distinguished from the region where the three-dimensional volume data is not present, that is, the contour and the brain parenchymal region when the brain is viewed from above are grasped. be able to.

  When the brain surface position is searched, a tangent line is provided at a position (brain surface position) where the extended line and the brain surface intersect, and a normal line orthogonal to the tangent line is calculated (ST32). That is, when a plurality of lines are extended from the reference position toward the brain surface, the searched brain surface position can be grasped. A tangent line can be set at the plurality of brain surface positions. This tangent setting is performed to derive a normal at each brain surface position. A normal is set perpendicular to the tangent and facing the brain parenchyma. This normal is for setting the luminance value at each brain surface position. Therefore, after setting the normal, the average luminance value of the pixels on each normal is calculated in order to express the depth of the sulci (ST33).

  These normals can be set even if they exceed the three-dimensional brain volume data, but in the embodiment of the present invention, luminance values are collected only for a few pixels from the brain surface position, Average. The reason why the number of pixels for calculating the average luminance value is limited to a few pixels from the brain surface position is that it exceeds the depth of the sulcus existing in the brain, considering that it represents the sulcus on the projected image. This is because it is considered unnecessary to obtain and average the luminance values of all the pixels on the normal line.

  A two-dimensional projection image of the brain is created using the calculated average luminance value (ST34). An example of the created projection image is shown in FIG. A portion far from the reference position, that is, a portion deep in the −Z direction is displayed in black because the luminance value is small. This part is a groove (brain groove) in the brain surface. This projection image can be created for any part of the brain surface depending on the setting of the reference plane.

  Next, creation of brain surface position data will be described. As shown in the flowchart of FIG. 8, first, the brain surface position data creating means 14 searches for the position of the brain surface based on the three-dimensional volume data of the brain parenchyma created in step 2 shown in FIG. 4 (ST41). . This step is the same as the step of creating the projection image described above. For example, when displaying the outer groove of the brain, the reference plane is defined as a virtual YZ plane, and a line is extended from this plane in the + X-axis direction.

  Then, the distance from the determined reference position to the searched brain surface is grasped (ST42). In addition, as long as the distance from the reference position can be accurately grasped, the grasped distance may be grasped in any unit.

  The lines extended in the + Z direction from the reference position on the virtual YZ plane are extended until they hit the brain surface of the three-dimensional volume data. By extending the line in this manner, the position of the brain surface and the distance from the reference position are grasped, but the sulcus portion is grasped far away, that is, as a long distance.

  Therefore, the brightness (brightness) in the display means 1g when displaying as brain surface position data is set according to the grasped distance (ST43). The relationship between the distance and the luminance is stored in advance in the storage unit 1i, for example. For example, the distance is converted into luminance so that a brain surface portion that is far from the reference position and has a long distance is black (dark), and a brain surface portion that is close to the reference position and has a short distance is white (bright). Then, brain surface position data is created using the set luminance (ST44).

  FIG. 9 shows the brain surface position data created in this way. FIG. 9 shows an example in which the lateral groove is indicated by brain surface position data. From this figure, as indicated by the dashed arrow, a black linear region is seen between the temporal lobe and frontal lobe, It can be understood that this portion is an outer groove. In addition, the temporal lobe region appears whiter (brighter) than the surrounding region, so it seems to protrude to the front.

  By performing the above processing, a projection image and brain surface position data are created from the three-dimensional volume data of the subject's brain. Using these images, the sulcus searching means 15 searches for a sulcus actually displayed. In the following, in the step (ST4) of searching for the position of the desired cerebral groove of the subject described above, the “cerebral longitudinal fissure”, “external groove”, and “central groove” are specifically cited as the cerebral grooves to be searched. I will explain.

[Search for sulcus position]
First, a “cerebral longitudinal fissure” will be described as an example of the search target. When searching for this longitudinal cerebral fissure, both the projection image and the brain surface position data are used. FIG. 10 is a flowchart showing a flow when searching for a cerebral sulcus (cerebral longitudinal fissure). FIG. 11 is a schematic diagram schematically showing a projection image (upper brain) of the subject's brain viewed from the head to the leg (from above). Although the projection image created as described above is two-dimensional, for convenience of explanation, FIG. 11 also shows the Z axis.

  As shown in FIG. 11, the cerebral sulcus search means 15 searches for the projections of the frontal lobe and the occipital lobe by two points using the projection image (ST51). For example, this is a point that extends from the reference position to the brain surface and is in contact with the brain surface, and can be searched by setting the point closest to the reference position. These searched convex portions A, A ', B, and B' are assumed. Here, the reference position is the X axis and a virtual line M parallel to the X axis (represented by a broken line in FIG. 11). The X axis and the virtual line M constitute the end side of the projected image to be displayed. The distances from the X axis and the virtual line M to the brain surface are calculated to determine the convex portions A, A ', B, B'. The reference position may be set anywhere as long as the distance from the reference position to the brain surface can be grasped.

  In the region between (A, B) and (A ', B') of the searched convex portions A, A ', B, B', the farthest point from the reference position is searched, and these are the start point and end point, respectively. (ST52). Here, as shown in FIG. 11, a point provided between (A, B) is a start point S1, and a point provided between (A ', B') is an end point G1. Then, the start point S1 and the end point G1 are connected by a straight line to form a temporary cerebral sulcus (cerebral longitudinal fissure) (ST53).

  Then, a plurality of points are placed on the temporary brain groove (ST54). The actual sulcus may not be a straight line but may be zigzag between the start point S and the end point G, or may be a curved line. Therefore, the plurality of placed points are used for more accurately searching for the position of the actually existing sulcus. The placement points may be placed at any interval, but a smaller placement interval contributes to grasping the position of the cerebral groove more precisely (accurately).

  Next, using the brain surface position data, each point placed on the temporarily placed sulcus is corrected (rearranged) to a position farthest in the −Z axis direction in the vicinity of each point (ST55). ). In other words, as described above, the brain surface position data is an image expressed by converting the distance distance into a luminance value. In other words, in the case of brain surface position data representing the upper brain, the distance from the reference position to each brain surface is known. Thus, each point is moved to the deepest position (in the −Z axis direction) in the direction orthogonal to the cerebral sulcus with the placed temporary sulcus as the center. Thus, the deepest position from the brain surface can be traced between the start point S1 and the end point G1. In this way, the exact position of the sulcus (cerebral longitudinal cleft) is specified (ST56).

  As for the amount of movement of the point placed on the temporarily placed sulcus in the direction perpendicular to the temporarily placed sulcus, if it moves too much, the desired sulcus cannot be specified. Considering this point, the sulcus searching means 15 is set in advance.

  Next, another method for searching for a sulcus by the sulcus searching means 15 will be described. In the following description, the “outer groove” will be described as an example of the search target. When searching for the outer groove, only the brain surface position data is used. FIG. 12 is a flowchart showing a flow when searching for a brain groove (outer groove). FIG. 13 is a schematic diagram schematically showing the state of the brain viewed from the right side, and the cerebrum R, cerebellum L, and brain stem B can be seen.

  First, a start point S and an end point G are set (ST61). However, since the positions of the start point S and the end point G to be set are unclear in the brain surface position data, a schematic diagram of the brain called “standard brain” is used. The details of the human brain vary from person to person. However, the positional relationship of the components of the brain such as the frontal lobe and the occipital lobe is not naturally different. Therefore, the “standard brain” is defined as the most common human brain. In the embodiment of the present invention, the positions of the start point S and the end point G of the outer groove are set by superimposing the “standard brain” and the brain surface position data representing the brain of the subject.

  After the positions of the start point S2 and the end point G2 of the outer groove are determined, the start point S2 and the end point G2 are connected by a straight line to form a temporary brain groove (here, the outer groove) (ST62). A plurality of points are placed on the cerebral sulcus temporarily placed thereon (ST63).

  Then, each point placed on the temporarily placed sulcus is corrected (rearranged) to a position farthest in the X-axis direction in the vicinity of each point (ST64). In the case of brain surface position data representing the right side of the brain, the distance from the reference position to each brain surface is known. Therefore, by moving each point to the deepest position in the X-axis direction in the vicinity of the temporary cerebral sulcus, the deepest position from the brain surface can be traced between the start point S2 and the end point G2. In this way, the exact position of the brain groove (outer groove) is specified (ST65).

  Further, another method for searching for a sulcus by the sulcus searching means 15 will be described. In the following description, the “center groove” will be described as an example of the search target. When searching for the central groove, only the projection image is used. FIG. 14 is a flowchart showing a flow when searching for the central groove. FIG. 15 is a schematic diagram schematically showing a projected image of the upper part of the subject's brain, similar to FIG.

  As for the central groove, since there are few features that serve as a mark for setting the start point and the end point as in the longitudinal cerebral fissure, the sulcus search means 15 superimposes the projection image on the standard brain and then sets the start point S3 and An end point G3 is set (ST71). Then, the start point S3 and the end point G3 are connected by a straight line to form a temporary brain groove (here, the central groove) (ST72), and a plurality of points are placed on the temporarily placed brain groove (ST73).

  Then, each of these points is corrected to a position where the average luminance value is low near the temporary sulcus (ST74). The details are as follows. A plurality of points are placed on the sulcus temporarily placed in step 73. Among the placement points, for example, the placement points are moved in a direction perpendicular to the temporarily placed cerebral sulcus in order from the placement point close to the start point. The positions of the placement points that are closer to the start point than the placement point to be moved (hereinafter referred to as “previous placement points”) have already been determined by the method described below. Therefore, the brightness value of each pixel located between the previous placement point and the placement point to be moved is calculated, and the calculated brightness values are averaged. An average luminance value is calculated each time the placement point to be moved is moved using such a calculation method. When a plurality of average luminance values calculated on that basis are compared, there is a position where the average luminance value appears lowest. This position indicates that the placement point to be moved is located on the sulcus. Accordingly, the placement point to be moved is placed again at this position.

  The points are connected so as to pass through the corrected points from the start point S3 to the end point G3, and the position of the cerebral sulcus is specified (ST75). In this way, the central groove is specified.

  The sulcus searching means 15 searches for a sulcus required by the method described above. The sulcus searched by the sulcus searching means 15 is specified on the sulcus area map by the sulcus area map creating means 16, and the desired sulcus is accurately specified on the image. These identified cerebral sulcus can be displayed, for example, as a sulcus map on a projected image or three-dimensional volume data.

  Furthermore, it is also possible to display the image by superimposing it with a separately created CT perfusion image (CT Perfusion), for example. A “CT perfusion image” is an image created on the basis of a test method in which cerebral circulation is analyzed from time-dependent changes in concentration and signal, with an X-ray CT device continuously imaging a contrast agent. is there. By using this CT perfusion image, cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) can be calculated. It is possible to easily evaluate the state to some extent.

  16 and 17 show a fusion image obtained by superimposing a CT perfusion image on a sulcus map created by the method described above. Originally, it can be displayed as a color image, but is shown as a black and white image in FIGS. FIG. 16 is a fusion image of the subject's brain as seen from above the brain, and FIG. 17 is a fusion image as seen from the right side. In these figures, the diseased area appears dark.

  Therefore, by using a fusion image in which not only a simple CT perfusion image but also a cerebral sulcus map that allows the position of the cerebral sulcus to be clearly understood is used, the range of disease in the subject's brain can be reduced. When identifying, it becomes easier to determine which part of the brain function is suffering from the disease. For example, from the fusion images in FIG. 16 and FIG. 17, the region where the blood flow is reduced and the brain function deterioration can be read in association with each other.

  By adopting the method described above, it is possible to sharpen an image photographed by an X-ray CT apparatus with a simple operation, and to accurately extract and specify the position of a specific cerebral groove. In addition, it is possible to provide an image processing apparatus that performs this cerebral groove position specifying method and a medical image diagnostic apparatus equipped with the image processing apparatus.

  In the above description of the search for cerebral sulcus position, for the purpose of understanding the explanation, a specific cerebral sulcus such as “cerebral longitudinal fissure” is described as an example. The combination is not fixed, and any search method may be employed for searching the cerebral sulcus position.

  The present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine the component covering different embodiment suitably.

It is a block diagram which shows the internal structure of the medical image diagnostic apparatus in embodiment of this invention. It is a block diagram which shows the internal structure of the image processing apparatus in embodiment of this invention. It is a flowchart which shows the rough flow which produces and displays a sulcus region map. It is the flowchart which showed the flow by which the three-dimensional volume data about brain parenchyma is created by the volume data creation means of the image processing apparatus. It is the flowchart which showed the flow which produces a projection image. It is the figure which represented three-dimensional volume data by the X-axis, the Y-axis, and the Z-axis. It is a schematic diagram which shows an example of the produced projection image. It is the flowchart which showed the flow which produces a brain surface position data projection image. It is a schematic diagram which shows an example of the produced brain surface position data. It is a flowchart which shows an example of the flow at the time of searching for a cerebral groove. It is the schematic diagram which represented typically the projection image (upper brain) which looked at the brain of the subject from the head toward the leg (from the top). It is a flowchart which shows an example of the flow at the time of searching for a cerebral groove. It is a schematic diagram which shows typically the state which looked at the brain from the right side. It is a flowchart which shows an example of the flow at the time of searching for a cerebral groove. It is the schematic diagram which represented typically the projection image (upper brain) which looked at the brain of the subject from the head toward the leg (from the top). It is a fusion image as an example which looked at the brain of the subject from the upper part of the brain. It is a fusion image as an example seen from the right side surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Medical image diagnostic apparatus 10 Image processing apparatus 11 Receiving means 12 Volume data creation means 13 X-ray absorption amount data creation means 14 Brain surface position data creation means 15 Brain groove search means 16 Brain groove region map creation means 17 Transmission means

Claims (14)

Creating three-dimensional brain volume data using a CT image acquired by imaging the head of the subject;
Creating X-ray absorption amount data representing the X-ray absorption amount of the brain surface portion of the subject based on the brain volume data;
Creating brain surface position data representing the position of the brain surface of the subject based on the brain volume data;
Searching for the position of the sulcus using the X-ray absorption data and the brain surface position data;
Positioning the searched sulcus position on the brain surface of the subject to create a sulcus region map;
A method for specifying the position of the sulci, comprising:   2. The cerebral sulcus position specification according to claim 1, further comprising a step of displaying the sulcus region map by reflecting the sulcus region map on the X-ray absorption amount data after the sulcus region map creating step. Method.   A step of superimposing a sulcus region map created by the sulcus region map creating unit and a separately imaged image showing a state of the brain of the subject after the displaying step is provided. Item 3. A method for specifying a sulcus position according to Item 2.   The brain volume data creation step includes a step of sharpening a photographed X-ray CT image of the brain of the subject, and a step of creating a mask that removes the skull from the X-ray CT image and uses only brain parenchyma data. And a step of extracting a region where the sharpened X-ray CT image and the mask overlap with each other. 4. The method for specifying a sulcus position according to any one of claims 1 to 3. The X-ray absorption data creation step includes
Searching the position of the brain surface of the brain volume data;
Calculating a normal perpendicular to a virtual tangent provided at the searched brain surface position;
Calculating an average pixel value in each normal line by calculating and averaging the CT values of pixels located on the normal line for each pixel; and
Determining a luminance value of each pixel at the corresponding brain surface position based on the calculated average pixel value;
Creating X-ray absorption data based on the determined luminance value;
The method for specifying the position of the sulcus according to any one of claims 1 to 4, further comprising: The step of creating the brain surface position data includes:
Searching the position of the brain surface of the brain volume data;
Grasping a distance from a reference position to the searched brain surface;
Defining a luminance value for each pixel displaying a brain surface according to the grasped distance;
Creating brain surface position data based on the prescribed luminance value;
The method for specifying the position of the sulcus according to any one of claims 1 to 4, further comprising: The sulcus position searching step includes:
Setting the start and end points of the sulcus to be searched using the X-ray absorption data;
Connecting the set start point and end point with a straight line to form a temporary sulcus;
Placing a plurality of points on the temporary sulcus;
Moving the positions of the plurality of points set forth above using the brain surface position data to a position where the distance from the reference position to the brain surface is the farthest in the brain surface position data in the vicinity of the temporary sulcus When,
Connecting the start point, the corrected plurality of points and the end point to be the sulcus to be searched, and
The method for specifying a sulcus position according to any one of claims 1 to 6, comprising: Creating three-dimensional brain volume data using a CT image acquired by imaging the head of the subject;
Creating X-ray absorption amount data representing the X-ray absorption amount of the brain surface portion of the subject based on the brain volume data;
Creating brain surface position data representing the position of the brain surface of the subject based on the brain volume data;
Searching for the position of the sulcus using the brain surface position data;
Creating a sulcus region map by positioning the searched sulcus position on the brain surface of the subject; and
The sulcus position searching step includes:
Superimposing a standard brain prepared in advance on the brain surface position data, setting a start point and an end point of the sulcus to be searched; and
Connecting the set start point and end point with a straight line to form a temporary sulcus;
Placing a plurality of points on the temporary sulcus;
Moving the positions of the plurality of points set forth above to positions where the distance from the reference position to the brain surface is the farthest in the brain surface position data in the vicinity of the provisional sulcus;
Connecting the start point, the corrected plurality of points and the end point to be the sulcus to be searched, and
A method for specifying the position of the sulci, comprising: Creating three-dimensional brain volume data using a CT image acquired by imaging the head of the subject;
Creating X-ray absorption amount data representing the X-ray absorption amount of the brain surface portion of the subject based on the brain volume data;
Creating brain surface position data representing the position of the brain surface of the subject based on the brain volume data;
Searching for the position of the sulci using the X-ray absorption data;
Creating a sulcus region map by positioning the searched sulcus position on the brain surface of the subject; and
The sulcus position searching step includes:
Setting the start and end points of the sulcus to be searched using the X-ray absorption data;
Connecting the set start point and end point with a straight line to form a temporary sulcus;
Placing a plurality of points on the temporary sulcus;
Moving the positions of the plurality of points set forth above to a position having the lowest luminance value in the vicinity of the temporary sulcus;
Connecting the start point, the corrected plurality of points and the end point to be the sulcus to be searched, and
A method for specifying the position of the sulci, comprising: Means for creating three-dimensional brain volume data using CT images acquired by imaging the brain of the subject;
X-ray absorption data creation means for creating X-ray absorption data that two-dimensionally represents the brain table of the subject based on the brain volume data;
Brain surface position data creating means for creating brain surface position data representing the brain surface of the subject with brightness contrast based on the brain volume data;
Cerebral sulcus searching means for searching for the position of the sulcus using the X-ray absorption amount data created by the X-ray absorption amount data creating means and the brain surface position data created by the brain surface position data creating means;
A sulcus region map creating means for positioning the position of the sulcus searched by the sulcus searching means on the brain surface of the subject;
An image processing apparatus comprising:   11. The image processing apparatus is capable of superimposing a sulcus region map created by the sulcus region map creating unit and an image showing a state of the brain of the subject taken separately. The image processing apparatus described. An X-ray tube;
An X-ray detector for receiving X-rays irradiated from the X-ray tube and passing through the subject;
Image generating means for forming an image of the subject from an electrical signal generated by the X-ray detector;
Means for creating three-dimensional brain volume data using a CT image of the subject's brain generated by the image generating means; and X-rays representing the subject's brain surface in two dimensions based on the brain volume data X-ray absorption amount data generation means for generating absorption amount data; brain surface position data generation means for generating brain surface position data representing the brain surface of the subject with brightness contrast based on the brain volume data; Cerebral sulcus searching means for searching for the position of the sulcus using the X-ray absorption amount data created by the X-ray absorption amount data creating means and the brain surface position data created by the brain surface position data creating means, A sulcus region map creating means for positioning the position of the sulcus searched by the sulcus searching means on the brain surface of the subject;
A medical image diagnostic apparatus comprising:   13. The medical image diagnostic apparatus according to claim 12, further comprising display means for displaying the sulcus specified by the sulcus region map creating means by reflecting it on the X-ray absorption amount data. Medical diagnostic imaging device. 14. The display unit can superimpose a sulcus region map created by the sulcus region map creating unit and an image showing a state of a brain of the subject that is separately photographed. Medical image diagnostic equipment.