JP5783627B2 - Human body modeling system - Google Patents

Description

  The present invention mainly relates to a human body model creating system for creating a human body model for medical education and medical treatment.

  In the medical field, it has become possible to photograph a detailed internal structure of a human body three-dimensionally by MRI, CT, ultrasonic waves, and the like. In ultrasonic examination, it is difficult to accurately read image information unless the three-dimensional structure of the human body is understood. In addition, medical treatments have been performed to treat a patient while observing the tissue with ultrasound, such as puncturing a tumor under an ultrasound guide and performing a nerve puncture for anesthesia under an ultrasound guide. . Therefore, a demand for grasping the three-dimensional structure of the human body has appeared. For example, Patent Document 1 describes that ultrasonic waves are applied to a human body model, and a built-in model diagnosis practice is performed based on the color tone of the ultrasonic image. There is also a teaching material on which an image obtained by reconstructing a 3D image from CT or the like (see Patent Document 2).

JP 11-242427 A JP 2002-40928 A

  However, since the inside of the conventional medical educational model cannot be seen, it is not possible to easily grasp the portion irradiated with ultrasonic waves. Such a problem is more conspicuous as the structure (such as a joint) has a more complicated structure. Bone and the like have been made from a human bone mold, but soft tissue has been made by human hands because it is difficult to make a mold. Therefore, it may be different from the actual dissection and has become a problem. In particular, when an anatomical structure, which was not a medical problem at the time of creation, has a new clinical significance due to advances in medical technology and knowledge, it is a problem because it has not been accurately created.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a human body model creation system capable of creating a human body model useful for medical education and medical care.

The present invention relates to a human body model creation system for creating a human body model from a transparent material based on the three-dimensional data of a human body created by the tissue extraction system , the tissue extraction system comprising a plurality of sequences with coordinate axes. An imaging unit that captures the image, a conversion unit that converts a plurality of sequences captured by the imaging unit into a histogram space that takes the sequence as a coordinate axis, and a center position of an island on the histogram space that is converted by the conversion unit Is calculated based on the center position, labeled to associate the histogram space coordinates with the tissue, an extraction unit for extracting the tissue of the subject, and the tissue extracted by the extraction unit Among them, a highlighting unit for highlighting a pathological tissue showing an abnormal signal pattern, and coordinates of the tissue extracted by the extraction unit A 3D data creation unit that creates 3D data by extracting information, and standardizes each sequence using island information in the histogram space, by standardizing by selecting a region using a free curve A coefficient is designated for each sequence, and transparency and color are set at each point in the histogram space using a library prepared in advance .

  Further, the transparent material may be a material excellent in ultrasonic transmission.

  Also, non-signal tissue in ultrasound images is transparent material without ultrasound signal, intermediate signal tissue is translucent material that becomes intermediate signal with ultrasound, high signal tissue is hard and signal is passed You may create it with no material.

  In addition, the intermediate signal tissue and the high signal tissue may be filled with a gel in a state where the intermediate signal tissue and the high signal tissue are prepared by an RP system and placed on a model covering the outside.

  A tissue extraction system for creating the three-dimensional data, the tissue extraction system including an imaging unit configured to image a plurality of sequences by aligning coordinate axes, and a plurality of sequences captured by the imaging unit; You may provide the conversion part which converts into the histogram space which took the coordinate axis, and the extraction part which extracts the structure | tissue of a subject from the distribution of the histogram converted by the said conversion part.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the human body model creation system which can create the human body model useful for medical education and medical treatment.

It is a perspective view of a human body model created by creation method A in an embodiment of the present invention. It is a figure for demonstrating the creation method A in embodiment of this invention. It is a figure for demonstrating the creation method A in embodiment of this invention. It is a figure for demonstrating the creation method A in embodiment of this invention. It is a figure for demonstrating the creation method A in embodiment of this invention. It is a figure for demonstrating the creation method A in embodiment of this invention. It is a figure for demonstrating the creation method A in embodiment of this invention. It is a figure for demonstrating the creation method A in embodiment of this invention. It is a figure for demonstrating the creation method A in embodiment of this invention. It is a figure for demonstrating the creation method A in embodiment of this invention. It is a figure for demonstrating the creation method A in embodiment of this invention. It is a figure for demonstrating the creation method A in embodiment of this invention. It is a figure for demonstrating the creation method A in embodiment of this invention. It is a figure for demonstrating the creation method B in embodiment of this invention. It is a figure for demonstrating the creation method B in embodiment of this invention. It is a figure for demonstrating the creation method B in embodiment of this invention. It is a block diagram of the structure | tissue extraction system in embodiment of this invention. It is a flowchart which shows the process of the histogram space in embodiment of this invention. It is a figure which shows expansion | deployment to the histogram space in embodiment of this invention. It is a figure for demonstrating the analysis method of the island in embodiment of this invention. It is a figure for demonstrating the analysis method of the island in embodiment of this invention. It is a figure which shows the center position of the island in embodiment of this invention. It is a figure which shows the example of a screen display in the display part in embodiment of this invention. It is a figure which shows the combination of a cone cell, and a color. It is a figure for demonstrating the organization classification | category in embodiment of this invention. It is a figure for demonstrating WL and WW in embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  In the human body model creation system according to the embodiment of the present invention, a plurality of three-dimensional data of a living body is obtained from CT, MRI, and three-dimensional ultrasound that are diagnostic apparatuses, the tissue is extracted by superimposing the three-dimensional data, and RP (Rapid Prototyping) Creates educational and clinical models by changing characteristics such as color, transparency, ultrasonic characteristics, and hardness according to the purpose of each tissue. By using a material with transparency and excellent ultrasonic transmission, it is possible to create a model for practicing ultrasonic examination and medical treatment while looking through the internal structure. It is useful for ultrasonic learning and practice, and can be used for preoperative practice of tumor puncture under ultrasound guidance when it is created from data obtained by imaging a patient.

  In the industry, a system for directly creating an actual product from computer design data, an RP system, is rapidly developing. Initially, only one type of material could be used, but it has become possible to create a mix of multicolored prints, transparent materials, and soft materials. It is possible to create a model useful for education and medical treatment by separating the tissue from the three-dimensional data of the living body and changing the color, transparency, and material (ultrasound permeability, etc.) of each tissue according to the purpose. is there. In particular, it is possible to create a useful material by using an RP system that is transparent and capable of multicolor printing.

  Hereinafter, a method for extracting a tissue by superimposing three-dimensional data, a method for creating a model based on the extracted tissue position information, and a method for use in education / clinical will be described.

1. Method of extracting tissue by superimposing three-dimensional data In medical practice, inspection apparatuses that acquire three-dimensional data such as MRI and CT are used. Since CT uses radiation, it is useful for detecting hard tissues such as bones, but is not good at detecting soft tissues. MRI uses a reaction between hydrogen and a magnetic field, and thus is excellent in detecting soft tissues such as muscles and fats. However, MRI is not good at detecting tissues such as bones without hydrogen. Although the field of view of three-dimensional ultrasound is narrow, soft part information can be obtained with high accuracy by using a three-dimensional high-frequency ultrasonic probe. In this way, three-dimensional data having different tissue specificities can be obtained for each apparatus.

  If it is the same apparatus, it is easy to align. Since MRI can fix an imaging range for each sequence at the time of imaging, it is possible to automatically perform superposition from position information unless the subject moves. When the photographing apparatuses are different, it is necessary to perform superposition based on the characteristics of the photographing data. Various methods have been devised for aligning information from different devices. There are a marker placement method, a marker placement method, a selection region matching method (surface matching, volume matching), an optimization method, and the like. Different three-dimensional data obtained using these methods are synthesized. As a result of the synthesis, vector data in which a plurality of pieces of signal information are set in arbitrary spatial coordinates is obtained.

  As a result of the superposition, it is possible to obtain a plurality of information in the three-dimensional coordinates. When the coordinates are (x, y, z), a vector (S1, S2, S3,..., Sn) having signal information corresponding to the type of information superimposed is obtained. When the information f (x, y, z) = (S1, S2, S3,..., Sn) is plotted in a multidimensional histogram space with the signal information as an axis, the tissue can be separated for each signal characteristic. It is. The present inventor has proposed such a tissue extraction system in Japanese Patent Application No. 2010-172482 (described later).

2. Method of creating model based on extracted tissue position information It is possible to obtain a set of position information for each tissue by the above method. It is possible to create a model by inputting such information into the CAD system and changing the material in the RP system for each organization. Of course, the method for creating the three-dimensional data of the human body is not particularly limited, and various methods can be employed. The method for creating a model based on the three-dimensional data is not limited to the method using the RP system. Two typical production methods will be described below.

(1) Preparation method A
A method A for creating a teaching material that does not have ultrasonic transparency but is translucent and can be seen through is shown. It is a teaching material that has the same shape as a human body and is translucent, and is capable of seeing through the tissue inside. It is possible to separate and observe the cross section of a specific cross section.

  FIG. 1 is a perspective view of a resin model of a knee joint created by the creation method A. Several parts can be divided in the vicinity of the joint, the divided pieces can be fitted (positioned), and the model can be fixed on the pedestal.

  When creating such a human body model, first, as shown in FIG. 2, a three-dimensional model is created from the CT image. The bone tissue and soft tissue are divided into models.

  Next, as shown in FIG. 3, the cross section 21 that divides the three-dimensional model is determined. What is necessary is just to determine the position and number of this division | segmentation cross section 21 according to the site | part of a model, the intended purpose, etc. FIG.

  Next, as shown in FIG. 4, the position for filling the positioning sphere is determined. Here, the fitting between the divided pieces is performed by two spheres 22. At that time, the fitting sphere 22 is arranged at a place as far as possible from the place where the model is required, and the arrangement of the fitting sphere 22 across the bone and the soft tissue is avoided. This is because it is difficult to determine which material will be used when straddling both.

  Next, as shown in FIG. 5, the model is cut by the divided cross section, and the penetration position of the skewer rod 23 is determined as shown in FIG. 6. The penetrating position of the rod 23 is arranged at a position where the uppermost part can be sufficiently fixed. Further, as shown in FIG. 7, the shape of the skewer rod 23 is determined.

  Next, as shown in FIG. 8, data for only the fitting sphere 22 is created in order to create a female type, and a Boolean operation is performed on the soft tissue and bone for the fitting sphere 22, and the fitting sphere is fitted to the soft tissue and bone. Attach 22 indentations 24. The Boolean operation is a method of modeling by a set operation of the sum, difference, and product of shapes having a volume in 3D computer graphics and CAD. Further, as shown in FIG. 9, the data of the fitting sphere 22 and the soft tissue / bone data are subjected to a Boolean operation to create data of the protrusion 25 only on the male side of the fitting sphere 22. Further, as shown in FIG. 10, the data with the depression 24 and the data with the projection 25 are Boolean-calculated and combined. Connecting the fitting ball 22 and each tissue from the beginning saves time, but it is necessary to pay attention to whether it is combined with bone or soft tissue.

  Next, as shown in FIG. 11, a skewer rod, a knee model base, and a skewer rod boolean calculation model are modeled. The skewer rod is designed to have a clearance of about 0.5 mm with respect to the Boolean calculation rod. Also, pay attention to the clearance at corners.

  Next, as shown in FIG. 12, the Boolean calculation is performed on the skewer rod Boolean model 23 and the model shown in FIG. Further, as shown in FIG. 13, a Boolean operation is performed on soft tissue and bone. As a whole, when the Boolean operation is performed on the soft tissue / bone and each element, the processed garbage 29 is severe, and correction is very troublesome. Therefore, it is desirable that each element is sufficiently corrected before the Boolean operation. Finally, when the modeling shown in FIGS. 10, 11, and 13 is performed, the model shown in FIG. 1 is completed.

(2) Preparation method B
A method B for creating a teaching material that is ultrasonically transparent and translucent and can be seen through is shown. The necessary characteristics of the teaching materials for ultrasonic examination practice are: (1) the important tissues such as blood vessels, muscles, and bones can be seen through; (2) the ultrasound image similar to that of the human body is drawn when the ultrasound is applied. To be done. In the ultrasonic image, there are a non-signal tissue such as water, an intermediate signal tissue such as muscle, and a tissue such as a bone that does not pass ultrasonic waves due to a high signal. Therefore, (1) a transparent material that does not have an ultrasonic signal in non-signal tissue, (2) a material that is an intermediate signal that is translucent in an intermediate signal tissue, and (3) a bone For example, a high signal structure such as a hard material that does not pass signals may be created by three-color printing. At present, there is no transparent RP material that does not have an ultrasonic signal, so the following method is adopted.

  14A is a CT image of a knee joint, and FIG. 14B is a three-dimensional model created from this CT image. Reference numeral 31 represents the no-signal structure of (1), reference numeral 32 represents the intermediate signal structure of (2), and reference numeral 33 represents the high-signal structure of (3).

  Here, as shown in FIG. 14C, the intermediate signal structure 32 and the high signal structure 33 are created by a two-color printing RP system to be an internal model 41. Next, as shown in FIG. 14 (d), a model that covers the outside is created from the inversion information of the non-signal tissue 31 + the intermediate signal tissue 32 + the high signal tissue 33, and is defined as the outer model 42. The outer model 42 can be opened like a mold using three-dimensional CAD software. The inner model 41 and the outer model 42 are connected to each other so that they can be stably combined. As shown in FIG. 15, the outer model 42 is filled with the gel 43 in a state where the inner model 41 is installed. As the material of the gel 43, an ultrasonic jelly can be used. The transparency is controlled by adding additives to this jelly. Further, the signal characteristics in the ultrasonic inspection apparatus are changed by changing the amount of the additive added to match the signal intensity. As shown in FIG. 16A, when the gel 43 is hardened, the outer model 42 is opened and taken out. The outer periphery is coated for stability. When the structure is large and stability cannot be maintained, as shown in FIG. 16 (b), a window 45 is attached to the outer model 42, the film is lined, and the probe 44 is applied from that portion to perform an echo inspection. Make it possible. Ultrasound echoes are not performed from all positions, but are only useful in such limited teaching materials because they are examined only in a specific direction from a specific site. In FIG. 16B, only one window 45 is provided, but it is needless to say that two or more windows 45 may be provided.

3. How to use in education and clinical practice (1) How to use A
How to use the human body model created by the creation method A will be described. That is, teaching materials that do not have ultrasonic transparency but are translucent and can be seen through are useful for grasping the three-dimensional structure in CT, MRI, and ultrasonic examination. It is also possible to understand the difference in three dimensions by creating from healthy human data and disease data. Moreover, it is possible to create teaching materials useful for detecting a specific disease by setting the cross section with CAD so that an important cross section can be seen in the diagnosis.

(2) How to use B
How to use the human body model created by the creation method B will be described. That is, teaching materials that are ultrasonically transparent and translucent and can be seen through are useful for practicing ultrasonic examination. In particular, tumor puncture under an ultrasound guide and nerve puncture for anesthesia have great differences between patients, and individual measures are required. It is possible to simulate the surgical procedure by creating a patient model before the operation.

  The RP system is created only from CAD data, without creating a mold every time it is created, unlike a product that mass-produces by creating a mold. Therefore, it is suitable for making small quantities and many varieties. It is possible to perform simulation for customized treatment using this characteristic.

  As described above, according to the human body model creation system in the embodiment of the present invention, since the human body model is created with a transparent material based on the three-dimensional data of the human body, medical education can be seen through the inside.・ Model of human body useful for medical care can be created. By using a material with transparency and excellent ultrasonic transmission, it is possible to practice ultrasonic inspection while seeing through the inside. Furthermore, a model can be created in actual size using the RP system, and characteristics such as color, transparency, ultrasonic characteristics, and hardness of the material can be easily changed depending on the purpose.

4). The tissue extraction system described in Japanese Patent Application No. 2010-172482 The present inventor has proposed a tissue extraction system that can efficiently extract a tissue using an image. Hereinafter, this tissue extraction system will be described in detail with reference to the drawings.

(1) Configuration of Tissue Extraction System FIG. 17 is a configuration diagram of the tissue extraction system 10 in the embodiment of the present invention. The tissue extraction system 10 is a system that extracts a tissue of a subject using an MRI image. Functionally, the tissue extraction system 10 includes an imaging unit 11, a conversion unit 12, an extraction unit 13, a processing unit 14, and a memory. 15 and a display unit 16. Of course, other processing units such as an input unit for inputting information and a communication unit for communicating with other systems are also provided, but they are not shown here.

  The imaging unit 11 is an MRI or the like that images a plurality of MRI sequences with the coordinate axes aligned. The conversion unit 12 converts the plurality of MRI sequences imaged by the imaging unit 11 into a histogram space using the MRI sequences as coordinate axes. The extraction unit 13 extracts the tissue of the subject from the histogram distribution converted by the conversion unit 12. The processing unit 14 performs various types of processing using the results extracted by the extraction unit 13. The memory 15 stores various data such as processing results of the processing units. The display unit 16 is a liquid crystal display or the like that displays data stored in the memory 15. The conversion unit 12, the extraction unit 13, the processing unit 14, the memory 15, and the display unit 16 can be mounted on an image processing workstation. The image processing workstation is an apparatus for specialized in advanced image processing, and details thereof will be described later.

(2) Features and image processing of CT image Before describing the configuration of the tissue extraction system 10 in detail, the function of CT (Computed Tomography) will be reviewed to explain the background of the importance of image processing. X-ray photography is a two-dimensional system in which a subject is irradiated with radiation and a film that senses radiation is placed behind the subject. CT is a system that creates a cross-sectional image by taking images while rotating a radiation source and a receiver and calculating data. Until the 1990s, since the slice thickness was 3-5 mm, it was rare that the number of images exceeded 100 in a single inspection, and images were burned on a film for diagnosis.

  Later, helical CT was developed, the slice thickness became 0.5-1 mm, and the exposure time decreased due to the increased number of detectors, and the imaging time was shortened. For example, it is possible to shoot from the head to the foot in 10 or more seconds, and the number of images has exceeded 1000. Thanks to this, even if there is no awareness due to traffic injury or the like, it is possible to diagnose the head, chest, abdomen, pelvis, etc. all at once, and the lifesaving rate has increased. However, when there are 1000 or more images, there is a problem in cost to burn these images on a film. Therefore, medical displays developed for displaying medical images are becoming popular.

  On the other hand, when diagnosing complex fractures, it is difficult to construct a three-dimensional structure of bones in the head by arranging CT images, which are a set of planar images, and there is a demand for creating a three-dimensional image based on CT images. Occurred. When the slice thickness was thick, only 3D images with low resolution could be created. However, as the slice thickness was reduced, very beautiful 3D images could be created.

  The CT image signal is called a Hansfield value (HU value), and unlike MRI, it is standardized so that water is 0 and air is -1000, so the signal distribution of muscles and bones is known in advance. By extracting only the part of the bone signal distribution (approximately 200 or more), only the bone region can be obtained, and a three-dimensional image of the bone can be automatically created based on the information. Similarly, since the signal distribution of internal organs and muscles is known, it is also possible to automatically create a three-dimensional image of a specific tissue. Therefore, the three-dimensionalization is easier for a tissue whose signal distribution does not overlap with other tissues. Since blood vessels are similar to the signal distribution of soft tissues such as muscles, it is difficult to extract only blood vessels. Therefore, a blood vessel contrast can be provided by intravenously administering a contrast agent that is safe to the human body and has a high CT value immediately before CT imaging. The signal value of the contrast agent is similar to the bone signal distribution. Therefore, it is difficult to extract only blood vessels from only contrast CT images, but only blood vessels can be extracted by back-calculating CT images before contrast and CT images after contrast. An image processing workstation specializes in such advanced image processing. Contrast inspection is also possible with MRI.

(3) Standardization of medical image standards and the emergence of the image processing workstation industry Next, we will review the history of the clinical image market and grasp the current situation. Traditionally, medical image manufacturers have manufactured only proprietary equipment, and each company has enclosed. As a result, each medical institution can only use equipment from the same manufacturer, resulting in high costs. Therefore, the American Radiologist Association and the North American Electronics Manufacturers Association discussed and established the DICOM (Digital Imaging and Communications in Medicine) standard. As a result, different manufacturers can exchange images.

  This has two effects on the market. The first is that the market size has expanded. According to the DICOM standard, the market has expanded rapidly because it can be sold in Europe, America and Asia. Second, the division of labor among manufacturers has progressed. MRI, CT, image server, image processing workstation, medical display company and specialized company. Combining these two factors, medical image manufacturers have appeared around the world, and the speed of technological innovation has increased. At present, image processing workstations are introduced in large hospitals in Japan, and are divided into departments that take CT and MRI images and departments that process images such as 3D.

  The revenue source of image processing workstation companies is support costs. Usually, high-function PCs are shipped with dedicated software installed, but the performance of PCs increases every few years, so even if it is the fastest at the time of purchase, it will soon become obsolete. For this reason, there are many business models that can be renewed every few years and earn with maintenance inspection fees. In order to differentiate it from other companies, various image processing functions have been added to increase the market value. Initially, it had only functions such as three-dimensional CT, but in recent years it has also been equipped with MRI image processing functions. The present invention can be added as an add-in to image processing software installed in such an image processing workstation.

(4) Method for processing an MRI image like a CT image Standardization of an MRI image signal using a histogram space will be described. The problem with MRI images is that the signal is a relative value that changes from inspection to inspection. That is, since the signal value of the CT image is standardized with 0 for water and -1000 for air, a specific tissue can be extracted by relying only on the signal value. On the other hand, in MRI, it is difficult to automatically extract a specific tissue from only a signal value, and it is necessary to know a signal distribution for each tissue in order to perform automatic extraction.

  Therefore, the tissue extraction system 10 according to the embodiment of the present invention employs a technique for extracting a tissue from a histogram (frequency distribution) of an MRI image signal. That is, the goal is to separate the tissue from the signal distribution, rather than standardizing from the signal value obtained by photographing a specific substance like the HU value.

  When a histogram of a single sequence is created by MRI, a distribution in which a plurality of peaks are connected can be obtained. However, since the distribution overlap is wide, it is difficult to separate each tissue distribution from a single sequence histogram distribution. This is because each tissue signal distribution is wide and the signal distributions overlap each other. Therefore, it has been difficult to separate the tissue from the histogram.

  However, if a plurality of sequences are photographed with the coordinate axes aligned, the tissue can be separated from the histogram. “Capturing with coordinate axes aligned” means capturing with a fixed imaging condition (imaging range, imaging magnification, etc.) of the subject. Assuming that the signal value of each sequence is (x, y, z) = Sn (S is a signal value at a designated coordinate, n is a sequence number), if the respective sequences are integrated, (x, y, z) = (S1, S2,..., Sn). Therefore, the sequence is converted into a histogram space H (S1, S2,..., Sn) having coordinate axes. As a result, the tissues in which the signal distributions overlap in each sequence are also separated in the histogram space. That is, two groups that cannot be distinguished by univariate may be distinguished by making them multivariate. In the present invention, by using such a multivariate analysis technique, it is possible to convert a plurality of MRI sequences into a histogram space to increase the tissue separation efficiency.

  If the imaged part is known, the type of tissue in the part can be known, so it is possible to identify which distribution is a specific tissue from the signal pattern in the histogram space. If the collection of signals in the histogram space is “islands”, it is possible to know which organization each island is. The exact position of the island changes depending on the subtle setting of the shooting sequence, but the distribution pattern does not change. For example, when a T1-weighted image, a T2-weighted image, or a T2 * (star) weighted image is photographed at the knee joint and converted into a histogram space, islands such as water, bone marrow, fat, and muscle are formed. When there is muscle degeneration due to age, the distance between islands changes, but not so much as the order of island positions changes. This characteristic can be used to standardize signal values and extract tissues.

(5) Processing of Histogram Space FIG. 18 is a flowchart showing processing of the histogram space in the embodiment of the present invention. Essentially it is important to label the tissue mask against the coordinates. Hereinafter, each processing will be described in detail.

(5-1) Expansion to Histogram Space The signal value of each sequence is (x, y, z) = Sn. Since the minimum and maximum values of Sn vary depending on the sequence, MRI model, and settings, it is considered to finally convert Sn into standardized rSn (step 5-2 below).

  Therefore, as shown in FIG. 19A, the conversion unit 12 integrates a plurality of sequences and arranges data into a multi-sequence matrix S (x, y, z) = (S1, S2,..., Sn). (FIG. 18, step 1). Next, as shown in FIG. 19B, the frequency distribution is calculated and expanded in the histogram space H (S1, S2,..., Sn) = m (FIG. 18, step 2).

(5-2) Analysis and standardization of islands Since the histogram space has a distribution with many gaps, it is easier to separate than a single sequence. There are differences such as many muscles and many bones depending on the person, but the signal distribution and island distribution in the histogram space do not change. However, since the signal value is not standardized at this stage, the island organization name is first identified from the island distribution. Taking a joint as an example, when the sequence is a T1-weighted image, a T2-weighted image, or a T2 * -weighted fat suppression image, as shown in FIG. 20, (A) moisture, (B) fat, (C) bone marrow, (D) Muscle / cartilage and (E) Air / bone / ligament are separated into separate islands. This histogram is represented in three dimensions as shown in FIG.

  Therefore, as shown in FIG. 22, the extraction unit 13 calculates the center position P of the island in the histogram space, and performs standardization based on the center position P (FIG. 18, step 3 → 4). Although an error occurs to some extent for each inspection, the center position P of the island does not move so much, which is useful for standardization.

  Specifically, standardization is performed using island center data for each organization created based on healthy individuals. For example, when a T1-weighted image, a T2-weighted image, and a T2 * -weighted fat suppression image are taken using a knee coil at 1.5 T MRI, the center of the knee fat signal is H (200, 200, 100) in the histogram space. Suppose there was. When the island center data of the knee fat signal in the MRI is rH (150, 200, 60), the conversion variable A is A = (0.75, 1.0, 0) from “A * H = rH”. .6). In the center of the island, reproducibility increases if a tissue with a large signal value is selected. This method is a linear transformation, but in order to further improve the standardization accuracy, a nonlinear transformation using the similarity of distribution patterns is effective.

(5-3) Tissue Labeling Next, the extraction unit 13 performs labeling for associating the histogram space coordinates with the tissue (FIG. 18, step 5). It is difficult to exclusively specify whether a certain space has muscles or bones. No matter how the accuracy of the image inspection is improved, the size of the voxel (volume pixel) is not reduced to the cell level, so that various tissues are contained in a certain voxel. Therefore, a method of specifying the existence probability for each organization for each voxel is considered.

  That is, the existence probability is determined for each organization based on the distance from the island center in the histogram space. It is assumed that the probability of being an organization near the center of the island is 100%. Since the surrounding signal distribution information is required for specifying the probability in the case of being away from the center of the island, the existence probability cannot be determined simply by the distance from the center of the island. This is because, when two tissues are close to each other, the establishment of the existence of the tissue rapidly decreases as the distance from the center increases. The existence establishment pattern changes depending on what kind of tissue exists in the imaging region.

  As described above, since the tissue classification in the histogram space slightly changes for each imaging region, a probability distribution library is created for each region when the island center of the tissue is determined and standardized. In this way, tissue labeling can be automatically performed using the probability distribution library.

  Probability distribution libraries are not required if tissue labeling is performed manually without automation. For example, the signal distribution in the histogram space can be displayed on the display unit 16, and the user can specify which range corresponds to which tissue in the histogram space while viewing the signal distribution. This is necessary for sites that do not have an established distribution library.

  FIG. 23 is a diagram illustrating a screen display example in the display unit 16. The display unit 16 can display the histogram space using a three-view diagram. As shown in this figure, an operation button group is arranged in the display area 16a, and various operations can be instructed using this operation button group. For example, the color arrangement of each sequence can be selected in the display area 16b, and the signal conversion level and gamma correction of each sequence can be set in the display area 16c (described later). Furthermore, in the display area 16d, a specific tissue distribution in the histogram space can be specified by selecting and surrounding a specific signal range (rectangular region in the figure). Collecting information on the points included in this rectangular area results in a list of coordinate information in which the tissue exists, and an arbitrary tissue can be extracted (FIG. 18, step 6).

  The tissue distribution in the histogram space often overlaps. A specific tissue can be efficiently extracted by selecting a region having a complicated shape instead of a simple rectangular region. It is clinically important to create a library of such tissue extraction patterns for each imaging region.

(6) Clinical Application Method for Tissue Extraction A common tissue mask common to each sequence can be obtained using a list of coordinate information. The clinically important application methods that can be performed using this tissue mask are the following items.

(6-1) Highlighting and automatic diagnosis of pathological tissue Since tumor tissue does not show a normal signal pattern, it appears as an island that is not normally recognized in the histogram space. Therefore, the processing unit 14 has a function of highlighting a pathological tissue that shows an abnormal signal pattern among the tissues extracted by the extraction unit 13. As a specific method, after standardizing the signal from the island pattern of the histogram space, the signal corresponding to the island of the abnormal signal pattern (island that is not normally recognized) is displayed in red or the like. In this way, the pathological tissue is highlighted as a red mask area in a normal black and white image. It will be easier to understand if you turn on / off highlights on the software.

  In practice, the highlight function is useful as a diagnostic aid because diagnosis is based not only on signal values but also on location and spread. Of course, if the signal distribution is clearly abnormal, diagnosis can be performed only from the signal distribution, and therefore an automatic diagnosis function for automatically presenting the diagnosis result to the user may be provided. However, it seems that the highlight function that clearly shows abnormal sites can be used clinically with confidence.

(6-2) Quantification by measuring the volume of the tissue of interest The volume change of the synovium of rheumatoid arthritis and the volume change of the tumor are used for determining the effect of the drug. Usually, the volume is simulated by measuring the length and width in the cross-sectional view that looks the largest. Since the human eye is used to extract a specific tissue, such a measurement method has been taken. In recent years, since the amount of image inspection has become enormous, the work of such measurement has increased, and the burden on the interpreting doctor has increased.

  If an area of a specific tissue can be automatically extracted, the volume can be automatically measured even with a complicated shape by simply counting the number of extracted voxels. Therefore, the processing unit 14 has a function of measuring the volume of the tissue from the number of voxels belonging to the tissue region extracted by the extraction unit 13. By extracting the same part of the histogram space and comparing the tissue volume for the MRI examination data set before and after treatment for the same person, it becomes possible to compare pathological tissues with high reproducibility and useful for judging treatment effects It is.

(6-3) Realistic Model Production and Navigation A full-scale model is created from three-dimensional CT and MRI data to create a bone model, and plate preoperative bending is performed on the bone model. Further, if the three-dimensional shape of the bone is known, it can be used for navigation surgery data. MRI three-dimensional data is considered to be inferior to CT three-dimensional data. However, extraction by multi-sequence increases the tissue contrast and thus the extraction accuracy increases. Therefore, the processing unit 14 has a function of creating the three-dimensional data of the tissue by extracting the coordinate information of the tissue extracted by the extraction unit 13. In this case, the mask data in which the existence of the tissue is “present = 1” and “none = 0” is necessary. However, according to the present invention, this can be realized only by selecting an area from the histogram space and extracting coordinate information. Can do.

(6-4) Multi-sequence color map If each of a plurality of sequences is converted into RGB and displayed on the display unit 16, a plurality of sequences can be diagnosed simultaneously. Therefore, the processing unit 14 has a function of creating a color map by associating each pyramidal cell with each MRI sequence and converting each of the plurality of MRI sequences to RGB based on the correspondence.

  That is, human visual cells include rod cells that recognize light and darkness and cone cells that recognize color. There are three types of cone cells: red, green, and blue. So-called three primary colors. Specifically, as shown in FIG. 24, “color” is recognized by superimposing red, green, and blue. Therefore, as shown in FIG. 25, the cone cell R and the T1 weighted image, the cone cell G and the T2 weighted image, and the cone cell B and the T2 * weighted image are associated with each other. This association can be realized by arranging the T1 weighted image in R, the T2 weighted image in G, and the T2 * weighted image in B in the display area 16b of FIG. If each sequence is synthesized in this state, fat is displayed in yellow and water is displayed in light blue, so that each tissue can be classified with a natural color scheme.

(6-4-1) Since the MRI signal is a relative value, the hue changes every time unless each sequence is standardized, causing confusion. At this time, if the signal is corrected and standardized from the tissue classification using the island distribution in the histogram space, the same color can be displayed for each examination. Usually, the MRI image is a black and white image, and is interpreted by a doctor who interprets images while changing the contrast. By adding a contrast correction function for each of the R, G, and B signals, fine adjustment can be made when correction in the histogram space is not successful. Various methods of fine adjustment are conceivable. However, since air signals are collected at the minimum value (signal value 0) of the MRI signal value, how to set the maximum value is important. Therefore, as shown in FIG. 26, two variables of WL (Window Level) and WW (Window Width) may be set. The values of these two variables can be finely adjusted in the display area 16c of FIG. If more detailed fine adjustment is required, set a gamma correction or, in some cases, a tone curve with a free curve.

(6-4-2) Since human color vision is a system in which R, G, and B are simultaneously analyzed by three types of pyramidal cells, it is not possible to analyze four or more colors simultaneously (the number is small but genetic) Some people have four primary colors. However, since there are often four or more types of MRI sequences, in order to display these MRI sequences at the same time, a method for converting information of four or more dimensions into three-dimensional information is required.

  The simplest method is to combine two specific sequences into one dimension. By specifying a conversion function in a two-dimensional signal space, two specific sequences can be synthesized (Formula 1). Usually, a simple linear transformation is used (Equation 2). In some cases, conversion in space is effective in order to increase the display capability for a specific organization (Formula 3). A conversion that maximizes the color distance between islands in the histogram space is useful.

F (S1, S2) = mS (Formula 1)
F (S1, S2) = aS1 + bS2 (Formula 2)
F (S1, S2, S3,... Sn) = (R, G, B) (Formula 3)
As described above, according to the tissue extraction system 10 in the embodiment of the present invention, a plurality of MRI sequences are converted into the histogram space and the tissue separation efficiency is increased, so that the tissue can be extracted efficiently. Moreover, it can be applied to various clinically important fields such as highlighting and automatic diagnosis of pathological tissues, quantification by volume measurement of target tissues, creation of solid models and navigation, and multi-sequence color maps. This is an extremely high invention. Since MRI can be taken with various sequences, there is an advantage that many examinations with different tissue contrasts can be performed.

  In addition, although the case where an MRI image is used is illustrated here, even when an image other than an MRI image such as a CT image, an ultrasonic image, or an electron microscope image is used, a plurality of signals can be obtained from the same coordinates. The present invention can be applied.

  That is, although the CT apparatus was imaged with only a single energy, dual energy imaging has recently emerged in which two sets of X-ray tubes and detectors are imaged at 90 ° positions. As a result, two types of signals can be obtained at the same coordinates. In the future, it is expected that the era of obtaining two or more types of signals by increasing the number of types of detectors will come. Thus, when a plurality of signals can be obtained from the same coordinates, the present invention can be applied, and the same effects as described above can be obtained.

  Currently, CT three-dimensional display methods use three-dimensional display methods by setting transparency and color for specific signal values. For example, in the three-dimensional display of bones, a library in which the bone signal value is expressed as white with transparency 0 (that is, opaque), the other part is set as transparency 100, and the color and transparency are displayed in gradation at the intermediate part in advance. Create it. Thereby, a three-dimensional image can be created from CT data in one step.

  If this method is expanded and a function for setting transparency and color at each point in the histogram space is provided, a three-dimensional display can be automatically performed. In the case of MRI, each sequence can be standardized using island information, so that it can be converted into a three-dimensional image having the same appearance each time. Even if island information is used, there is a slight deviation, so a function for specifying a standardization coefficient for each sequence is necessary. For designation in the histogram space, not only a rectangle but also an area selection using a free curve is performed, so that tissues close to the histogram space can be separated efficiently. This system can be created by extending the area selection function of 3D image processing software.

DESCRIPTION OF SYMBOLS 10 Tissue extraction system 11 Imaging part 12 Conversion part 13 Extraction part 31 No signal structure | tissue 32 Intermediate signal structure | tissue 33 High signal structure | tissue

Claims (4)

A human body model creation system that creates a human body model with a transparent material based on the three-dimensional data of the human body created by the tissue extraction system ,
The tissue extraction system includes:
An imaging unit for imaging a plurality of sequences by aligning coordinate axes;
A conversion unit that converts a plurality of sequences imaged by the imaging unit into a histogram space using the sequences as coordinate axes;
The center position of the island on the histogram space converted by the conversion unit is calculated, standardization is performed based on the center position, labeling for associating the histogram space coordinates with the tissue is performed, and the tissue of the subject is determined. An extractor for extracting;
A highlighting unit for highlighting a pathological tissue showing an abnormal signal pattern among the tissues extracted by the extraction unit;
A three-dimensional data creation unit that creates three-dimensional data by extracting the coordinate information of the tissue extracted by the extraction unit;
When standardizing each sequence using island information on the histogram space, specify a standardization coefficient for each sequence by performing region selection using a free curve, and using the library created in advance, A human body modeling system characterized by setting transparency and color at each point in the histogram space .   The human body model creating system according to claim 1, wherein the transparent material is a material excellent in ultrasonic transmission.   Transparent material that does not have ultrasonic signals in ultrasonic images in ultrasonic images, intermediate signal tissue that is translucent and intermediate signals in ultrasonic waves, and high signal tissue that is rigid and impervious to signals The human body model creation system according to claim 2, wherein the human body model creation system is created by the following.   4. The human body model creating system according to claim 3, wherein the intermediate signal tissue and the high signal tissue are filled with a gel in a state where the intermediate signal tissue and the high signal tissue are created by an RP system and placed on a model covering the outside.