JP4454055B2 - Image display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image display apparatus that selects and displays a biological tissue on a medical image such as a CT image.
[0002]
[Prior art]
Conventionally, in order to delete, for example, a bone on a CT image, there is a method of deleting an area between two threshold values. These two threshold values are bone values (pixel values and CT values. Here, the pixel value is a pixel value obtained by converting a CT value obtained by reconstruction into a multi-gradation for display. In the following description, pixel values are used, but the same applies to CT values.) Upper limit value and lower limit value are set respectively, and values within the two threshold values of these upper limit value and lower limit value are used as bone values. Delete from.
[0003]
[Problems to be solved by the invention]
In such a conventional example, what value is set to the two threshold values is important for accurate bone image removal. In particular, when a contrast medium is injected (injected), the value of the blood vessel containing the contrast medium and the bone to be removed may be close to each other. Therefore, when the bone is removed, the blood vessel containing the contrast medium is also removed. There was an example that would have been. This is shown in FIG. FIG. 2A is a CT image of a cut surface 3 including a bone 1 and a blood vessel 2 containing a contrast medium. Further, the pixel value profile on the cut surface 3 is as shown in FIG. Here, if the upper threshold 6 and the lower threshold 7 are set so as to include all the bone pixel value profiles 4, the pixel value profile 5 of the blood vessel containing the contrast medium is also included. Therefore, when the range obtained by the two threshold values is deleted, there is an example in which necessary information (contrast agent profile 5) is also removed as in the profile 8 of FIG.
[0004]
An object of the present invention is to provide a CT image processing apparatus that leaves a blood vessel or the like containing a contrast medium on a display image and can remove only bone.
[0005]
[Means for Solving the Problems]
The purpose is different from the first threshold value setting means for setting a first threshold value for setting a plurality of pixel regions in an image based on information input by an operator's input, and the first threshold value. A second threshold value setting means for setting a second threshold value, and a pixel area including a pixel that is equal to or higher than the second threshold value is deleted from the plurality of pixel areas set by the first threshold value setting means. An image display device comprising: a deletion area extracting means to be obtained as an area; an area removing means for removing the deletion area from the image; and a means for displaying an image from which the deletion area has been removed . Achieved.
[0006]
The image display device may further include an extended region setting unit that sets an extended region, and the region removing unit deletes the extended region together with the deletion region .
[0007]
Further, in the image display device, the extension region setting means sets an extension width, and the extension region is a region having the extension width outside the deletion region . Achieved.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of an image display device of the present invention will be described with reference to the drawings.
FIG. 1A shows a relationship diagram between a pixel value profile and a threshold setting example of the present invention. The upper limit value A of the threshold was selected to be lower than the peak of the bone pixel value profile 4 and higher than the peak of the pixel value profile 5 of the blood vessel containing the contrast medium. The lower limit value B of the threshold value was selected to be lower than the peak of the blood vessel profile 5 containing the contrast medium and higher than the pixel value profile level of biological tissue other than bone and blood vessels.
[0009]
A method of processing using the two threshold values A and B will be described with reference to FIG. Of the pixel values exceeding the threshold B, only the pixel values (peaks) exceeding the threshold A, but not all the pixels exceeding the threshold B, are deleted from the upper limit (both P1 and P2 in FIG. 1). Among all pixel values exceeding the threshold B, pixel values (waveforms) other than the deleted portion remain. As a result of this processing, as shown in FIG. 1B, the bone profile 19 is removed, and the blood vessel profile 5 containing the contrast medium remains as it is. The profile 11 indicates a pixel value profile of a living tissue other than blood vessels and bones.
[0010]
According to this embodiment, the blood vessel profile 5 containing the contrast medium remains without being deleted, and most of the pixel values of the bone profile 4 can be deleted.
[0011]
Another embodiment will be described. In FIG. 1B, it is assumed that the bone profile 19 is almost deleted, but actually, the rising portion of the bone profile 19 (the lower side of P2 in FIG. 1, so-called whiskers) a, b, c, d remains. In order to delete the beard-like components a to d, the threshold B may be set to a level smaller than the beard-like components a to d. There is a risk of deleting an unlimited number of parts including the part you want to keep. After all, it is difficult to adopt a method of changing the level of the threshold B and removing the whiskers.
[0012]
Therefore, as a new concept, a position width W (width on the horizontal axis) as an extended portion including a whisker-like component is set in the vicinity of the portion deleted using the threshold value B, and a profile in the position width W is set as Decided to delete. This is shown in FIGS. 3 (a) and 3 (b). 3A is an explanatory diagram of the extended portion, and FIG. 3B is a profile deletion result of the extended portion. By introducing such a neighborhood extension W, whiskers a to d were completely deleted.
[0013]
The extended portion W will be described in detail. The extended portion W may be determined by looking at the waveform, but there are many examples in which such a profile is not displayed. In that case, decide empirically. Deletion at the extended portion W is performed by specifying a deletion position where the profile has become zero, and selecting and deleting a width of ± W (the width of W on each side) from the deletion position. Here, ± W is set to delete both the side deleted at the threshold B and the side not connected to the threshold B and, as a result, delete only the side not deleted. For example, the left side is deleted for a and the right side is deleted for b. By setting ± a and ± b, the direction can be ignored and deleted. Of course, it is also possible to take a way of deleting in consideration of the direction. As another method for deleting, a pixel threshold value Δh for removing the whisker pixel component may be set in the vicinity of the position before and after the deletion position, and a pixel value exceeding this may be deleted.
[0014]
FIG. 4 shows a processing system diagram. In this system, a CPU 20, MM 21, CRT 22, auxiliary memory 23, keyboard 24, and mouse 25 are connected to a common bus 26. The CT image is stored in the auxiliary memory 23, and the CPU 20 and the MM 21 perform processing as shown in FIGS. The keyboard 24 and the mouse 25 perform various inputs such as designation of CT images and setting of thresholds A and B. The CRT 22 displays CT images and profile images.
[0015]
FIG. 5 shows an explanatory diagram for CT image processing. This image is a multi-gradation grayscale image, but it is difficult to represent it as it is. FIG. 5A shows the original CT image 14. In this image, a portion indicated by a symbol 140 indicates a bone, and a portion indicated by a symbol 141 indicates a blood vessel containing a contrast medium. FIG. 5B shows a diagram in which only pixel values equal to or greater than the threshold A are extracted from the image 14. Since this extracted diagram shows pixel values that are equal to or greater than the threshold value A in the bone, it is not a diagram showing the entire bone. FIG. 5C is a diagram in which only pixel values equal to or higher than the threshold value B are extracted, and pixel values equal to or higher than the threshold value B in the blood vessel 141 including the bone 140 are extracted. FIGS. 5 (b) and 5 (c) are explanatory diagrams showing extracted pixel values greater than the threshold values A and B respectively. On the other hand, it can be seen from FIG. 5 (b) that the entire bone cannot be deleted. FIG. 5C shows that the blood vessel 141 is also deleted.
[0016]
In the present invention, as shown in FIG. 5D, pixel values belonging to the bone 140 are deleted (deleted region 17) among the deleted pixel values equal to or greater than the threshold value B. Therefore, according to the processing example of the present invention, an image as shown in FIG. 5E can be obtained. In this image, it can be seen that the entire bone 140 shown in FIG. 5D is deleted, and the blood vessel 141 remains without being deleted.
[0017]
According to the present embodiment, it is possible to delete a bone while leaving a blood vessel containing a contrast medium. In addition, although the example of the blood vessel and bone containing a contrast agent was shown, it is not limited to this. In addition, the example of A> B with the two thresholds A and B is described, but the present invention can also be applied to an example in which pixel values equal to or less than B are deleted in an example of A <B. Moreover, although shown in order to delete, it is applicable also to the example which selects and leaves.
[0018]
FIG. 5A is a CT image including bone 1 and contrast medium 2. First, the threshold A9, the threshold B10, and the extended portion 12 in FIG. A range 15 that is greater than or equal to the threshold A and a range 16 that is greater than or equal to the threshold B are obtained for the threshold.
[0019]
Next, in a range that is equal to or greater than the threshold value B, an area that includes a range that is equal to or greater than the threshold value A is obtained and set as a deletion area 17. The deleted region 17 is expanded to the number of pixels set in the expanded portion 12 (that is, the pixel region), and is removed from the original image, thereby obtaining an image 18 after deleting the bone region.
[0020]
【The invention's effect】
According to the present invention, a blood vessel or the like containing a contrast medium is left on the display image, and only the bone can be removed.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a processing example of the present invention.
FIG. 2 is an explanatory diagram of a conventional example.
FIG. 3 is an explanatory diagram of a modification processing example of the present invention.
FIG. 4 is a system configuration example diagram of the present invention.
FIG. 5 is an explanatory diagram of an image processing example of the present invention.
[Explanation of symbols]
4 Profile (bone)
5 Blood vessel with contrast medium 20 CPU
21 MM (main memory)
22 CRT
23 Auxiliary memory 24 Keyboard 25 Mouse 26 Shared bus

Claims (3)

First threshold value setting means for setting a first threshold value for extracting a plurality of pixel regions in the image based on information input by an operator's input ;
Second threshold value setting means for setting a second threshold value different from the first threshold value;
If the first threshold value is smaller than the second threshold value, a pixel area including a pixel that is equal to or higher than the second threshold value is selected as a deletion area from the plurality of pixel areas extracted by the first threshold value setting unit. If the first threshold value is greater than the second threshold value, a pixel region including a pixel that is equal to or lower than the second threshold value is extracted from the plurality of pixel regions extracted by the first threshold value setting unit. A deletion area extraction means for obtaining a deletion area;
Area removing means for removing the deleted area from the image;
Means for displaying an image from which the deletion area has been removed;
An image display device comprising: The image display device according to claim 1,
An extended area setting means for setting an extended area;
The image display apparatus according to claim 1, wherein the area removing unit deletes the extension area together with the deletion area. The image display device according to claim 2,
The extension area setting means is for setting an extension width,
The image display device according to claim 1, wherein the extension area is an area having the extension width outside the deletion area.

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