JPS602238A - Ct image display apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field to which the invention pertains] The present invention relates to 1, for example, CT (Computerized
The present invention relates to a CT image display device used in a CT image display device that converts image data into luminance data when displaying a reconstructed image.

[Prior art]

2. Description of the Related Art CT apparatuses that obtain tomographic images of a subject using radiation such as X-rays are conventionally known. For example, in this CT device, an X-ray tube and an X-ray detection device are placed facing each other with a subject in between, and the X-ray tube and detection device are rotated integrally around the subject. The specimen is exposed to X-rays, the intensity of the X-rays that have passed through the specimen at each rotation angle is detected, and this is collected in the storage unit as projection data.Then, the Conbeater analyzes each of the tomographic planes of the specimen. Calculate the X-ray absorption rate of the part,
The tomographic plane is reproduced with a gradation level corresponding to the absorption rate. In this case, analysis can be performed in as many as 3,000 gradations depending on the tissue HX-ray absorption rate of each part of the tomographic plane.

This CT display data, which is expressed in 3000 gradations, is divided into black level and +3000 as white level. 300 as shown
An arbitrary specific range of CT values (&~b) of interest is determined from among the 0-stage CT values, and the CT values in this range are used as the displayable gradation of the display device, so-called luminance data gradation (256
The images are displayed on the screen by dividing them into different gradations.

However, in the conventional device, when converting luminance data to gradation, a conversion process covering the entire input data range H,
-The memory capacity is large because it has a pull-pull, and as shown in Figure 1, the CT value of a specific range is determined by the level value, which is the center value of the CT value range, and the width of the CT value range, that is, the window width. (for example, 100), but each time the level value or window width is changed, the table is rewritten accordingly only by software, so an extra buffer memory of the same capacity as the table is required, and the level value If you try to follow changes in real time, there is a drawback that the CPU will be occupied by the rewriting work.

Furthermore, the luminance gradation distribution within the window width is usually uniform (C
The T value and the luminance data are in direct proportion to each other). A uniform brightness gradation distribution is effective for images such as the abdomen, but a brightness gradation distribution that emphasizes contrast at the center of the window width is more effective for images such as the head. It is very convenient to be able to change the brightness gradation distribution depending on the target area in this way. Although there are some systems in which the luminance gradation distribution is variable, there is a problem in that even though it is variable, only a limited number of gradation distributions are available, and an arbitrary distribution cannot be obtained and is not very effective.

[Purpose of the invention]

An object of the present invention is to provide a CT image display device that can solve all of these drawbacks and problems at once.

[Summary of the invention]

In order to achieve the purpose of the table, in the present invention, the capacity of the table depends only on the window width, and a separate register is used to convert the level change, and the table rewrite line hardware due to the change in width is used. This reduces the capacity of the table for brightness data by automatically using software, reduces the burden on the CpH for rewriting the table, and speeds up rewriting. At the same time, it can be accessed by software. The present invention is characterized in that it is equipped with a luminance gradation distribution table, which allows any luminance gradation distribution to be easily obtained.

〔Example〕

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 2 is a block diagram of main parts showing an embodiment of a data conversion device according to the present invention. In the figure, 10 is a data area boundary value comparator (hereinafter simply referred to as a comparator), 20 is a first switch, 30 is a brightness data table, 40 is a second switch,
Reference numeral 50 indicates a table rewriting circuit, and reference numeral 60 indicates a brightness gradation distribution table. The comparator 10 compares input data with a window area lower limit value. This input data is image data expressed in CT values, and this image data is image data reconstructed by a computer (not shown).

By the way, in the present invention, several kinds of specific widths are used as the window width (for example, 20°40, 6
0. ..., 500.1000) are prepared,
One of these can be designated by a code number. The table area has a capacity corresponding to the maximum window width (1000 in this embodiment).

The comparator 10 compares the input data with the window lower limit value, and as shown in FIG. 3, if the input data is in the range ■ smaller than the lower limit value, output! The m degree data lower limit value is outputted from iD2, and conversely, in the range (2) which is larger than the value obtained by adding the table area OCT value width to the lower limit value, the brightness data upper limit value is outputted from the output end D2.

Further, when the input data exactly corresponds to the range (3) of the table area, the deviation from the window lower limit value can be sent to the output terminal D1.

The first switch 20 selects and outputs either the output from the output terminal D1 of the comparator 10 or the rewriting address sent from the table rewriting circuit 50, and displays images in a television format. In this case, the output of the comparator 10 is selected during the period other than the blanking period, and the address output of the table rewriting circuit 50 is selected during the blanking period, and each can be applied to the table 30 as an address signal. ing.

The brightness data table 30 has brightness data of a maximum of 256 gradations set from black to white as the CT value within the window increases, and its contents are determined by addressing with the output of the switch 20. can be read out. Further, the contents of the table can be rewritten, and the rewriting data is supplied to the table rewriting circuit 50. The second switch 40 is
Either the output data of the table 30 or the D2 output of the comparator 10 is selected and sent out as the luminance data output. When the comparator 10 sends out the D2 output, the D2 output is selected and the D1 output is sent out. When sent, the output of table 30 is selected.

The table rewrite circuit 50 sends a rewrite address and rewrite data to rewrite the contents of the table 30 when the level value and window width are changed. FIG. 4 is a block diagram of an embodiment showing its details, in which 51 is an address counter, 52 is a step ROM, 53 is an adder, 54 is a latch, and 55 is a switch. The address counter 51 increments the table address by one address and outputs it. The step ROM 52 stores gradation data increment values corresponding to each window width in a ROM of 16 steps each. For example, in the case of a window width of 2o, the gradation data and the output data increase value are stored in the ROM. The values are as shown in Table 1, and the configuration is such that the data increase value can be output by specifying the window width code and address.

The adder 53 in Table 1 is used to cumulatively add this data increase value, and feeds back the output through the circuit 54, so that the newly given input data is added to this output value. It is something. The switch 55 is normally a two-way switch 54.
is selected, and the cumulative addition value of the adder 53 is 25.
When the brightness exceeds 6, the overflow signal activates and selects a preset brightness upper limit value. The output of the switch 55 is led to the table 30 as rewrite data, but the switch 55 is also controlled by a vertical synchronizing signal and is configured so that the output data is valid only during the blanking period.

The brightness gradation distribution table in FIG. 2 outputs the data of the brightness gradation distribution table corresponding to the output data from the switch 40 as brightness output data. The contents of the tone distribution table can be easily changed, and any tone distribution can be set.

The operation in such a configuration will be explained next.

During a normal luminance data conversion operation, the procedure is as follows. -CpU from the set level value and window width
calculates the window area lower limit value, and uses this as the comparator 10
is given as a reference value. The comparator 10 compares sequentially input reconstructed image data with this lower limit value. As shown in Figure 3, the lower limit value (black level) of luminance data is uniformly applied to the input data in the range ■, and the upper limit value (white level) of the brightness data is uniformly applied to the input data in the range ■. Both are sent out from the D2 output terminal. When the input data is in the range ■, the deviation from the window lower limit value is sent out from the D□ output terminal and given as an address signal to the table 30 via the switch 20, and the contents of the memory at that address are read out. It is output as luminance data via the switch 40.

This table 30 is rewritten every time the window width changes. Next, the operation during rewriting will be explained. This rewriting operation is performed during the blanking period, and all rewriting necessary for changing the window is completed within one blanking period.

Give the window width code (for example, it can be the address number of the start address of the step ROM for each window - 1) to the step ROM 52, and set a new window from among the many windows stored in advance. Specify the window to use. For example, assume that a window with gradations as shown in Table 1 is set. The addresses of the step ROM 52 are updated one by one by the address counter 51, and the read contents of the ROM 52 are sequentially cumulatively added in the adder 53, and the cumulatively added value for each address is used as table rewriting data via the switch 55. table 30
give to In the table 30, the rewriting data (gradation take shown in Table 1) is written to the address specified by the address counter 51 (the leading address is the same for all windows). In this way j−
During the next rewriting, when the rewritten data reaches the brightness data upper limit value, the switch 55 selects and outputs the brightness data upper limit value, and only the brightness data upper limit value is uniformly written to the remaining addresses in the table. In this way, an update table showing the relationship between input data and luminance data as shown in range (3) in FIG. 3 is completed.

The luminance data output from the switch 40 in this manner has a linear distribution relationship with the CT value, as shown in FIG. 5(a). The brightness gradation distribution table 60 receives the output of the switch 40 as a distribution table address, and sends out the contents of the address as brightness output data. As a result, luminance data having a nonlinear relationship with the CT value can be obtained as shown in FIG. 5(b). The relationship between the CT value within the window width and the luminance data gradation is arbitrarily determined by a distribution table, and the contents of the distribution table can be rewritten.

〔Effect of the invention〕

As explained above, according to the present invention, there is no need for a table with a large capacity to store luminance data over the entire CT value range as in the past, and the table is limited to the maximum width of the window. The memory capacity is small, and since the capacity is small, the rewriting time can be shortened, and table rewriting is done by hardware, so it does not occupy the CPU (reducing the burden on the CPH). Effects such as can be reduced υ, and at the same time,
Since the relationship between the CT value and the brightness data can be easily set to any desired relationship, there is an effect that the abdomen, head, and other parts can be observed using images with a desired brightness distribution.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between CT value and brightness data gradation, Figure 2
5 is a diagram for explaining the relationship between input and output data of the present invention, FIG. 4 is an embodiment diagram of the table rewriting circuit 5o of FIG. 3, and FIG. 5 is a diagram of an embodiment of the present invention. 3 is a diagram showing the relationship between CT value and luminance data gradation in FIG. 2. FIG. 10...Data area boundary value comparator, 20, 40.55
...Switcher, 30...Brightness data table, 50.
...Table rewriting circuit, 51...Address counter,
52... Ste, Brom, 53... Adder, 54...
- Latch, 60... Brightness gradation distribution table.

Claims (1)

[Claims] A CT image display device that divides the reconstructed image data into predetermined gradations and converts it into luminance data in order to display the reconstructed image on the screen with appropriate contrast only around the CT value of interest. a luminance data table having a memory capacity sufficient for the maximum width among a number of window widths and capable of writing and reading luminance data;
The lower limit value of the window is compared with the input reconstructed image data, and the input data is divided into three types of data: data used as the address of the brightness data table, the lower limit value of brightness data, or the upper limit value of brightness data. and a table rewriting circuit which stores information regarding brightness data for a large number of windows in advance and sequentially outputs an address to be written in the brightness data table and brightness data of that window when a desired window is designated. and a luminance gradation distribution table that has a rewritable luminance gradation distribution table and can read luminance output data by addressing with output luminance data from the luminance data table. Device.