JP3244347B2 - Image processing method and image processing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and an image processing apparatus for improving a stereoscopic image display of a tomographic image.

[0002]

2. Description of the Related Art With the spread of high-speed CT and the practical use of helical scanning in recent years, attention has been paid to three-dimensional image display. Here, the helical scan means that the gantry including the X-ray tube and the detector is rotated several times, and the table on which the subject is placed is moved forward or backward during that time, and the periphery of the subject is spiraled with X-rays. This is a method of performing scanning. As the simplest 3D image display method, MIP
(Maximum Intensity Projection) processing is known. The MIP processing is a projection image obtained by taking out the largest value of all pixels in each observation direction from all original images to be processed. Also, it is possible to take out the minimum value, average value or specific value without limiting to the maximum value.
This is hereinafter referred to as image projection or IP (Image Projection).
Call the law. For example, the focus was low de
Sometimes rendered as nsity. At that time, Min_IP (Mi_IP (Mi
nimum Intensity Projection) processing is effective.

[0003] In general high-speed CT, several tens to several hundred images are usually obtained per patient. In particular, lung cancer mass screening by helical scan has recently been proposed, but image processing performance (interpretation efficiency) is more problematic than CT processing performance (setting of table moving speed suitable for diagnosis, etc.) at that time. There is. The IP method is expected as a new display method capable of solving such a problem.

Further, using a series of IP images obtained by finely changing the observation direction by an angle, it is possible to three-dimensionally observe the running of a blood vessel and the relationship between a lesion and a blood vessel in a cine mode. It is considered that such three-dimensional observation is useful for determining the size of the tumor and determining whether the tumor is malignant or benign. Therefore, the IP method can be considered as one basic display function when performing continuous scanning in the axial direction in high-speed CT.

[0005] In addition to the above-mentioned CT, MR may be used to obtain a tomographic image. However,
While MR angio basically does not show bones, CT images show bones quite strongly. Normally, the bone hinders the CT MIP process. Therefore, CT MIP
In processing, the removal of unnecessary areas including bones is extremely important in preprocessing.

The following two methods can be considered for extracting a region of interest including such bone removal. A first method for extracting a region of interest is a method of setting a threshold to delete an unnecessary region (threshold method). The second method is a method of extracting a region of interest using a mask (mask method).

[0007]

However, depending on the threshold value method, it is difficult to extract a region of interest when the contrast between an unnecessary organ and the organ of interest is difficult to obtain (the difference in CT value is small). There is. For example, by performing the contrast, the CT values of the bone and the blood vessel may be considerably close to each other, and in such a case, it may be difficult to extract the region of interest.

Further, a specific pattern such as a square or a circle is mainly used as a mask in the case of processing by the mask method. As described above, it is efficient to perform mask processing using a specific pattern such as a square or a circle, but the unnecessary area cannot be completely deleted, or the region of interest to be observed is significantly deleted. May occur. On the other hand, it is conceivable to individually create suitable masks by plotting on an image. According to such a method of plotting on individual images, it is possible to completely eliminate only unnecessary regions, but it is necessary to work for each individual image, and the efficiency is extremely deteriorated. Therefore, in the mask method, it has been desired to generate an efficient and accurate mask.

As a three-dimensional image display method other than the above-described MIP processing, there is a 3D processing for generating a three-dimensional image using a plurality of tomographic data. Unless a plurality of tomographic data from which a region of interest has been extracted are prepared in advance for the 3D processing, a desired part may not be seen due to an outer bone or the like. For example, when the lungs and the heart are displayed in 3D using the tomographic data of the chest, the ribs may hinder the user from seeing the inside.

For this purpose, it is necessary to remove unnecessary regions by performing mask processing and threshold processing on all of the plurality of tomographic data in advance. However, as described above, the removal of the unnecessary area has problems in work efficiency and the accuracy of the unnecessary area removal.

[0011] In addition, there has been a request to display an arbitrary image at an arbitrary angle in any of three-dimensional image display of MIP processing and 3D processing. The present invention has been made in view of the above points, and an object of the present invention is to perform efficient mask processing on tomographic data obtained by CT helical scan, MR, or the like, and obtain desired three-dimensional data by MIP processing, 3D, or the like. An object of the present invention is to realize an image processing method and an image processing apparatus capable of displaying an image.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image processing method for performing image processing after performing mask processing on image data of a plurality of cross-sections. Perform predetermined processing,
A step of generating a mask for all image data, a step of performing mask processing on all image data using the generated mask, and generating masked image data;
And performing a desired image processing using the masked image data.

An image storage means for storing image data to be processed, and a predetermined process for generating a mask for the image data stored in the image storage means,
Mask generating means for generating a mask for all image data, and a mask processing unit for performing mask processing on all image data using the mask generated by the mask generating means to generate masked image data And an image processing unit for performing desired image processing using the masked image data masked by the mask processing unit.

[0014]

In this image processing method and image processing apparatus,
The mask generation unit performs a predetermined process for generating a mask on the image data to be processed, generates a mask for all the image data, and the mask processing unit uses the mask to process the entire image data. Then, mask processing is performed to generate masked image data, and desired image processing is executed using the masked image data thus generated. Since unnecessary areas are removed from the masked image data, an arbitrary three-dimensional image can be displayed by performing various types of image processing.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic processing step of an image processing method according to one embodiment of the present invention. FIG. 2 shows an image processing apparatus according to an embodiment of the present invention. First, the configuration of the image processing apparatus will be described with reference to FIG.

In FIG. 2, an image storage unit 1 stores CT or MR image data obtained by a tomography apparatus (not shown). The image processing device 2 executes a desired image process after performing an efficient mask process on the image data stored in the image storage unit 1.
° MIP processing unit 3, mask generation unit 4, mask processing unit 5,
An image processing unit 6 is provided. The 0 ° MIP processing unit 3 generates data for determining a mask common to all image data to be processed or a predetermined amount of image data, and the mask generation unit 4 generates a mask common from this data.
The mask processing unit 5 performs efficient mask processing on all image data or a predetermined amount of image data using a common mask. The image processing unit 6 performs various desired image processing (3D, MIP processing, etc.) on the masked image data, and displays the processing result on the display unit 7. The control section 8 controls the operation of the entire apparatus.

Next, an image processing method and an image processing step of an image processing apparatus according to an embodiment of the present invention will be described.
The image storage unit 1 stores a large number of image data obtained by CT or MR. For example, a description will be given on the assumption that image data including a series of several tens of tomographic images in the body axis direction of the chest and abdomen obtained by helical scan is accumulated.

Each of the image data of the tomographic images thus accumulated has a relatively small change (close cross section).
In the case of, since the change between the respective image data is small and the unnecessary area exists at the same position, a process of generating one mask for all the image data at once is performed.

If each of the image data has a relatively large change, the unnecessary area of each image data is located at a position shifted gradually, so that all the image data is processed by one mask. In other words, even the necessary area is covered by the mask. Therefore, division processing is performed such that a plurality of masks are generated by dividing the area into small groups for each small change. For this reason, the control unit 8 controls the image processing apparatus 2 based on an instruction from an operation unit (not shown) (FIG. 1).
step 1) ).

First, a description will be given of a case where processing is performed collectively without performing division processing. The 0 ° MIP processing unit 3 performs MIP processing such as a maximum value, a minimum value, an average value, and a specific value using dozens of image data stored in the image storage unit 1.

As a result, image data (mask generation data) is generated such that bones, hearts and the like of all image data are superimposed (FIG. 1 (2)). In this embodiment, the case where the subject is placed horizontally on the table is taken as an example, so that the 0 ° MIP processing in the body axis direction is performed, but the subject is tilted on the table. When it is mounted, the MIP processing is performed with an inclination that matches the inclination of the subject instead of 0 °.

In this 0 ° MIP processing, a mask for removing a common unnecessary area is generated after performing processing using all image data. However, the first and last masks are not used without using all image data. MI using two image data
Even if the P processing is performed to generate a mask in a range covering the unnecessary area of these two data, a similar mask is obtained as a result. Therefore, in order to shorten the processing time, it is also possible to perform the 0 ° MIP processing using the first and last two pieces of image data.

FIGS. 3 and 4 show a certain section of the image data, and FIG. 5 shows the image data for mask generation obtained by the 0 ° MIP processing as described above. Here, what is shown in FIG. 5 is mask generation image data obtained by performing MIP processing suitable for a mask for removing bone. For this reason, the bones appear to overlap.

The mask generation unit 4 generates a mask with reference to the mask generation data (FIG. 5) obtained as described above. When removing the bone, a mask corresponding to a portion where the bone is seen in FIG. 5 is generated to generate a mask for batch processing that removes the bone and leaves a lesion (step in FIG. 1). (3)). Conversely, a mask that leaves a bone can also be generated. Further, a mask that removes an artery or a vein to leave a capillary portion or a mask that removes an air layer is also conceivable.

That is, various masks can be generated in accordance with a desired image desired by the operator. If masking bones, use MIP (Maximum Inte
nsityProjection) Generates a mask by processing. Also,
If masking air, etc., the minimum value should be Min_IP
(Minimum Intensity Projection) Generate a mask.

Using the mask for batch processing obtained in this way, the mask processing unit 5 performs a mask process on image data composed of a series of images stored in the image storage unit 1 (FIG. 1). Step (4)), the masked image data is returned to the image storage unit 1 again. In this case, since mask processing can be performed using a common mask, the efficiency is high and the mask processing time can be significantly reduced. In addition, since a common mask is generated for image data having a relatively small change, a region of interest can be accurately extracted.

Next, the case where the dividing process is performed will be described. The 0 ° MIP processing unit 3 uses the tens of image data stored in the image storage unit 1 to determine several regions for each image having a small change, and stores the image data for each region. And performs MIP processing such as a maximum value, a minimum value, an average value, and a specific value for each area (step (5) in FIG. 1). As a result, mask generation data is generated for each divided area (FIG. 1 (6)). Referring to the mask generation data (FIG. 5) obtained in this way, the mask generation unit 4 generates a mask for division processing for each of the divided areas (step (7) in FIG. 1).

Using the division processing mask obtained in this manner, the mask processing unit 5 performs the mask processing for each of the divided areas of the image data composed of a series of image groups stored in the image storage unit 1. (Step (8) in Figure 1)
), The masked image data is stored in the image storage unit 1 again.
Return to In this case, since mask processing can be performed using a common mask for each region, efficiency is improved, and mask processing time can be reduced as compared with the conventional case where mask processing is performed for each sheet. Also in this case, since a common mask is generated for a group of image data having a relatively small change, the region of interest can be accurately extracted.

The image processing unit 6 performs desired image processing on the masked image data stored in the image storage unit 1 and displays the image data on the display unit 7. In this case, since a group of image data from which unnecessary portions have been removed by mask processing has already been stored in the image storage unit 1, any image processing can be performed in the image processing unit 6. It is. That is, even in the case of MIP processing or 3D processing at an arbitrary angle, processing can be performed without being affected by unnecessary objects such as bones, and a desired image can be easily observed.

As described above in detail, according to this embodiment, a mask can be generated by generating a common mask for image data of a large number of tomographic images. Image processing can be performed. In addition, since various types of image processing can be performed on the image data after the mask processing, an arbitrary three-dimensional image can be displayed.

[0031]

As described above in detail, by generating a common mask for a large number of tomographic image data and performing the mask processing, extremely efficient and accurate mask processing and image processing can be performed. It is possible to realize an image processing method and an image processing apparatus capable of performing processing, performing various image processing on the image data after the mask processing, and displaying a desired image.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an outline of processing contents of an image processing method according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a configuration of an apparatus according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing how a mask is generated according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing how a mask is generated according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing how a mask is generated according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image storage part 2 Image processing apparatus 3 0 degree MIP processing part 4 Mask generation part 5 Mask processing part 6 Image processing part 7 Display part 8 Control part

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G06T 1/00 G06T ⁷ /00-7/60 A61B 6/00-6/14 313

Claims (4)

(57) [Claims] 1. An image processing method for performing image processing after performing mask processing on image data of a plurality of cross sections,
For a plurality of image data of the image data to be processed, perform a process of extracting a predetermined value for all pixels in each observation direction to create mask generation data,
Generating a mask for all image data using the mask creation data, performing mask processing on all image data using the generated mask, and generating masked image data; And performing a desired image process using the masked image data. 2. The image data of the plurality of cross sections are divided into a plurality of groups, and a plurality of image data to be processed for each group is subjected to a predetermined process for all the pixels in each observation direction with respect to a plurality of image data. A process for extracting a value is performed to generate mask generation data, a mask is generated for the image data of the group using the mask generation data, and a plurality of masks are generated using the mask thus obtained. 2. A mask processing is performed for each group.
The image processing method described in the above. 3. An image storage means (1) for storing image data to be processed, and among image data stored in the image storage means (1), a plurality of image data in all directions in each observation direction. Mask generation means (3, 4) for generating mask generation data by performing a process of extracting a predetermined value for each pixel, and generating a mask for all image data using the mask generation data; Generation means (3,
A mask processing unit (5) that performs mask processing on all image data using the mask generated in 4) and generates masked image data, and a mask processing performed by the mask processing unit (5). An image processing device comprising: an image processing unit (6) for performing desired image processing using the processed image data. 4. The mask generating means (3, 4) divides the image data of a plurality of cross sections into a plurality of groups, and sets a plurality of image data to be processed for each group into a plurality of image data in each observation direction. Performing a process of extracting a predetermined value for all the pixels located above to generate mask generation data; generating a mask for the image data of the group using the mask generation data; 4. The image processing apparatus according to claim 3, wherein (5) performs mask processing for each of a plurality of groups using a mask for each group.