JPH07320028A - Projection image processing method and projection image processing apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] A projection image processing method and a projection image processing apparatus capable of displaying a projection image with good visibility by displaying together with the attention area without deleting the areas that were conventionally deleted other than the attention area. To be realized. [Structure] An area in which the brightness of the image display is to be changed is extracted from the image generated by the image reconstruction (step), the brightness value changing process is executed for the extracted image area, and the brightness value of the image data is changed. Is changed (step), and a projection image is generated by performing a projection process for extracting a predetermined value preset for each pixel with respect to the plurality of image data subjected to the brightness value change process (step). And the projection image processing method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection image processing method and a projection image processing apparatus for an image diagnostic apparatus, and more specifically, it focuses on a region other than the region of interest, which has been conventionally deleted (deleted region). The present invention relates to a projection image processing method and a projection image processing device that can be displayed together with a region to generate a projection image with good visibility.

[0002]

2. Description of the Related Art Projection (IP: Intensit) is the simplest three-dimensional image display in an image diagnostic apparatus.
y Projection) Processing is known. For example, using a series of IP images obtained by changing the observation direction at a fine angle, it becomes possible to stereoscopically observe the running of blood vessels and the relationship between the lesion site and blood vessels, etc., in the cine mode. Such three-dimensional observation is considered to be useful for determining the tumor size and malignancy / benignity. Further, it is expected that the diagnosis will be facilitated by generating a 3D image from a projection processing result of a large number of image data obtained by the helical scan to obtain one stereoscopic image.

Here, the IP processing is a predetermined value such as a maximum value (or a minimum value, a specific value) for the signal value of the density or brightness of each corresponding pixel for all original images to be processed. This is a process of obtaining a projection image (IP image) obtained by extracting a value and projecting it.
That is, in the case as shown in FIG. 5, the first to Nth original images obtained in the depth direction are subjected to a process of extracting a predetermined value from pixels at the same position for all pixels to obtain one image. I am trying to get a projected image of. Then, the IP processing for the maximum value is performed by MIP (Maximun
Intensity Projection) processing and IP processing performed with a minimum value are called MinIP (Minimum Intensity Projection) processing, and IP processing performed with a specific value is called a specific value IP processing.

For example, in this MIP process, a tissue (for example, bone) having a higher intensity than a tissue (for example, blood vessel) to be extracted becomes an obstacle. Therefore, if the work of removing them is not done in advance, a projection image in which only the maximum value bone is extracted can be obtained.
Therefore, it is necessary to delete such an area. Therefore, in the obtained projection image, the bone region is removed and only the blood vessel is extracted.

Similarly, in the MinIP process, a tissue (for example, air) having a lower intensity than a tissue to be extracted (for example, a diseased part) becomes an obstacle. Therefore, it is necessary to remove them in advance.

As a process for removing the above disturbing tissues,
Threshold processing for removing unnecessary areas by setting thresholds, mask processing for setting masks to remove masked areas, and removal of areas of the same signal value in areas of other images that overlap unnecessary areas of one image Consolidation processing etc. can be considered.

[0007]

By executing the above-described projection processing, it is possible to generate a projection image of the attention area without being blocked by unnecessary areas such as bones. However, as a result of completely deleting the bone, there is also a problem that the positional relationship between the bone and the attention area is not clear. Therefore, it may be difficult to understand the region of interest anatomically.

The present invention has been made in view of the above points, and an object thereof is a projection image processing method and a projection image processing apparatus capable of displaying the relationship between a region of interest of a subject and unnecessary regions around the region of interest. Is to be realized.

[0009]

The first means for solving the above-mentioned problems is to extract an area in the image generated by image reconstruction in which the brightness of the image display should be changed, and extract the extracted image. The brightness value changing process is executed for the area to change the brightness value of the image data, and the projection process for extracting a predetermined value set in advance for each pixel is executed for the plurality of image data having the brightness value changing process. Is a projection image processing method.

A second means for solving the above-mentioned problems is a changed area extracting means for extracting an area in the image generated by image reconstruction in which the brightness of the image display should be changed, and the changed area extracting means. Luminance changing means for changing the luminance value of the image data by executing the luminance changing processing on the extracted image area, and preset for each pixel of the plurality of image data subjected to the luminance value changing processing by the luminance changing means. And a projection processing unit that executes projection processing for extracting a predetermined value to generate a projection image.

[0011]

In the first means for solving the problem, the area in which the brightness of the image display is to be changed is extracted from the image generated by the image reconstruction, and the brightness value changing process is performed for the extracted area of the image. The brightness value of the image data is changed by being executed, and the projection process for extracting a predetermined value set in advance for the plurality of image data subjected to the brightness value changing process is executed to generate a projection image.

In the second means for solving the problem, a region in which the luminance of the image display is to be changed is extracted from the image generated by the image reconstruction, and the luminance value changing process is performed on the extracted image region. The brightness value of the image data is changed by being executed, and the projection process for extracting a predetermined value set in advance for the plurality of image data subjected to the brightness value changing process is executed to generate a projection image.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a projection image processing apparatus according to an embodiment of the present invention, and FIG. 2 is a flowchart showing an operation procedure of a projection image processing method according to an embodiment of the present invention.

First, the configuration of the projection image processing apparatus will be described with reference to FIG. The data storage unit 1 is for temporarily storing image data obtained from an MRI (magnetic resonance imaging apparatus), a CT scanner, an ultrasonic diagnostic apparatus, etc., and is a magnetic disk apparatus, a magneto-optical disk apparatus, or the like. It is composed of. The pre-processing unit 2 has a brightness value, a density value, etc. (hereinafter, referred to as a changed area) of an area for changing the display brightness
It is also used to change the brightness value), and is composed of a frame memory 3, an extracting unit 4, and a changing unit 5.
The frame memory 3 stores the image data read from the data storage unit 1. The extraction unit 4 extracts a changed area of the image data in the frame memory 3, and the changing unit 5 sets a luminance value of the changed area to a predetermined value. Change to the value of. The IP processing unit 6 sequentially executes a projection process on the plurality of image data items that have been changed by the pre-processing unit 2. The display unit 7 displays the projection image obtained by the projection processing by the IP processing unit 6. The extracting unit 3, the changing unit 5, and the IP processing unit 6 are configured by software, hardware, and firmware such as a computer device or an image processing processor in which each processing program is installed.

The operation of the projection image processing apparatus thus configured and the projection image processing method will be described with reference to FIGS. 1 and 2 by taking the case of image data obtained by a CT scanner as an example.

The data storage unit 1 stores a plurality of image data obtained by CT scanning, and this image data is read into the preprocessing unit 2 for each image. The image data read by the preprocessing unit 2 is temporarily stored in the frame memory 3. And the frame memory 3
The extraction unit 4 extracts a change area from the image data stored in (2). Here, the change area is an area in which the brightness and the density of the image display are changed. In the conventional projection image processing apparatus, a bone or air region is treated as a deletion region and processed before the projection process, but in the present embodiment, such a region is treated as a change region and the brightness and density are changed and displayed. I am trying to do it. That is, the area that has been deleted in the past is changed in brightness and density and then displayed.

FIG. 3A is a histogram showing the relationship between the CT value of the image data of the head section obtained by the CT scanner and the appearance frequency. Thus, bone has a CT value of 1
It is distributed around 000, the brain parenchyma is distributed around CT value 0, and the air is distributed around CT value -1000.

Since the CT value distribution is as described above, bones are an obstacle in the MIP processing in which the projection processing is performed with the maximum value. In addition, air interferes with the MinIP processing in which the projection processing is performed with the minimum value.

Here, the case of performing the MIP processing will be described. In this case, the bone is extracted as the changed area (step in FIG. 2). As this extraction, various extraction methods such as a method of setting by setting a threshold value, a method of setting a mask and an extracting method by a concatenation method can be considered.

According to these various extraction methods, the corresponding area of the image data stored in the frame memory 3 is extracted. For example, for each pixel in the corresponding area of the image data stored in the frame memory 3,
It is conceivable to manipulate a predetermined bit to indicate that it is a change area.

Next, the changing unit 5 changes the luminance value (CT value in the case of CT image data) of the area where the image data in the frame memory 3 is extracted according to a predetermined algorithm. If the histogram of the image data before the change is as shown in FIG. 3A, the CT value of the bone part is extracted and changed, and the result is as shown in FIG. 3B. That is, in the case of MIP processing, the CT value of the data in the changed area is made smaller than the CT value of the area of interest (near 0) and is larger than the distribution of the minimum value (air: CT value near -1000). . The CT value level satisfying such a condition will be referred to as a background level in this embodiment.

In such a changing process, when the CT value of the data in the extraction region before the changing process is DATAold, the CT value of the data in the extracting region after the changing process is DATAnew, and the constant is α,
It can be expressed as DATAnew = DATAold−α. This constant α is set in advance so that the CT value of the bone is changed between the brain parenchyma and the air as shown in FIG. 3B. Therefore, by this change processing, the data in the corresponding change area of the image data stored in the frame memory 3 is changed.

Then, the IP processing unit 6 causes the frame memory 3
Projection processing such as MIP processing is executed using the image data of 1. and the projection image is displayed on the display unit 7. By doing so, it is possible to perform the projection process without deleting the bone region, which was previously deleted as an unnecessary region in the MIP process,
The bone with the changed CT value will be displayed as an IP image together with the brain parenchyma in the region of interest. In this case, the bone C
Since the T value is smaller than that of the brain parenchyma and larger than that of the air, as a result of the MIP process, the portion where the brain parenchyma is present is projected as the maximum value, and the portion where the brain parenchyma is not present is projected as the maximum value of the bone. Therefore, not only the brain parenchyma as the region of interest but also the state of the surrounding bones are displayed. Therefore, it is possible to display the area that has been deleted as an unnecessary area together with the attention area.

Next, in place of the MIP processing for performing the projection processing with the maximum value described above, Mi for performing the projection processing with the minimum value is used.
The case of nIP processing will be described. In this case, conventionally, it was necessary to delete the air region having the minimum CT value as an unnecessary region. Therefore, the CT value of this air region is extracted and changed to perform the processing as shown in FIG.

In such a changing process, when the CT value of the data in the extraction region before the changing process is DATAold, the CT value of the data in the extracting region after the changing process is DATAnew, and α is a constant,
It can be expressed as DATAnew = DATAold−α. As for this constant α, as shown in FIG. 3C, the CT value of air (around −1000) is the CT value of brain parenchyma (around 0) and the CT value of bone (around 100).
A value that can be changed in the middle of (around 0) is set in advance. By doing so, for example, even if there are air and gas regions in the body, they are displayed.

In the above embodiment, extraction and modification are performed via the frame memory 3. However, as shown in FIG. 4, the address of the area extracted by the extraction unit 4 is modified by the modification unit 5.
It is also possible to notify. The notification in this case may be a direct notification or a notification via a bus or the like. Then, the changing unit 5 that receives the notification from the extracting unit 4
Does not need to write the extracted result to the frame memory 3 (the number of times of writing to the frame memory 3 is reduced).
Therefore, speeding up of extraction and change processing can be expected.

Further, in each of the above-mentioned embodiments, the constant α is added and subtracted as the CT value changing process, but the CT value can be changed by multiplying by the constant α. In this case as well, it can be realized by predetermining a constant α such that the results shown in FIGS. 3B and 3C are obtained and executing the changing process.

In this case, C of the attention area and the unnecessary area
Although the value and sign of the constant α are determined by the magnitude of the T value and the magnitude of the CT value after the change, they can be expressed by the formula DATAnew = DATAold × α. Therefore, the extraction unit 4 refers to the histogram of the image data in the frame memory 3 to determine the constant α of the above-described change processing and executes the change processing.

Further, it is possible to change the CT value of the region of interest so as to obtain the same result as the above embodiment. Further, it is possible to switch between the region of interest and the conventional change region as the change region between the MIP process and the MinIP process.

Although the CT images obtained by the CT scanner have been described in the above embodiments, the present invention is not limited to this, and various image diagnostic apparatuses such as a nuclear magnetic resonance diagnostic apparatus, an ultrasonic diagnostic apparatus, and PET. It can be applied to processing images. In this case, the CT values described above correspond to the brightness value and the density value of each image.

As described above, the area (change area) in which the brightness of the image display is to be changed is extracted from the image generated by the image reconstruction, and the brightness value changing process is executed on the extracted image area. A projection image for generating a projection image by executing a projection process for changing the brightness value of the image data, and extracting a predetermined value set in advance for each pixel from the plurality of image data that has been subjected to the brightness value changing process. According to the processing method, by designating an area that was previously an unnecessary area other than the attention area as the change area, there is no need to delete the area that was previously deleted as an unnecessary area, and it is possible to display it together with the attention area. It will be possible.

Further, in the image generated by the image reconstruction, the area where the brightness of the image display should be changed (changed area)
Change area extracting means for extracting the brightness value, brightness changing means for changing the brightness value of the image data by executing the brightness changing process for the area of the image extracted by the change area extracting means, and the brightness value changing means by the brightness changing means. According to the projection image processing apparatus including the projection processing unit that executes the projection processing for extracting the predetermined value set in advance for each pixel of the processed plurality of image data to generate the projection image, By specifying a region that was previously an unnecessary region other than the region of interest and extracting the changed region,
It is no longer necessary to delete the area that has been deleted as an unnecessary area in the past, and it is possible to display the area together with the attention area.

Therefore, it becomes possible to display the area which has been deleted as an unnecessary area in the past together with the attention area.

[0034]

As described above in detail, according to the present invention, an area where the brightness of the image display should be changed is extracted from the image generated by the image reconstruction, and the brightness of the extracted image area is changed. A projection image is executed by executing a value changing process to change the brightness value of the image data and extracting a predetermined value set in advance for each pixel from the plurality of brightness value changing process image data. It is possible to realize a projection image processing method and a projection image processing apparatus that can generate a projection image with good visibility by displaying together with the attention area without deleting the conventionally deleted areas other than the attention area.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a projection image processing apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart of the operation of the projection image processing method and the projection image processing device.

FIG. 3 is an explanatory diagram showing how a brightness value is changed.

FIG. 4 is a block diagram showing the configuration of another embodiment of the projection image processing apparatus of the present invention.

FIG. 5 is an explanatory diagram showing a state of projection processing.

[Explanation of symbols]

 1 Data Storage Section 2 Pre-Processing Section 3 Frame Memory 4 Extraction Section 5 Change Section 6 IP Processing Section 7 Display Section

Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G06T 5/00

Claims (2)

[Claims] 1. A region from which an image display luminance is to be changed is extracted from an image generated by image reconstruction, and a luminance value changing process is executed on the extracted image region to obtain a luminance value of image data. A projection image processing method, wherein a projection image is generated by performing a projection process for extracting a predetermined value set in advance for each pixel on a plurality of image data that has been changed and has undergone a brightness value change process. 2. A change area extracting means for extracting an area in which the brightness of the image display should be changed in the image generated by the image reconstruction, and a brightness changing process for the area of the image extracted by the change area extracting means. And a brightness changing unit for changing the brightness value of the image data, and a projection process for extracting a predetermined value set in advance for each pixel of the plurality of image data which has been subjected to the brightness value changing process by the brightness changing unit. And a projection processing unit for generating a projection image, the projection image processing apparatus comprising: