JPH032534B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a CT image display device suitable for a CT (Computed Tomography) device. 2. Description of the Related Art CT apparatuses that obtain tomographic images of a subject using radiation such as X-rays are conventionally known. In this CT device, for example, 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 rotate 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, this is collected in the storage unit as projection data, and then analyzed by a computer to determine each part of the tomographic plane of the specimen. The X-ray absorption rate is calculated, and the tomographic plane is reproduced with a gradation level corresponding to the absorption rate. In this case, the structure of each part of the tomographic plane can be analyzed in as many as 3,000 gradations depending on the X-ray absorption rate. This CT display data, so-called CT value, is expressed in 3000 gradations, with 0 being the black level and +3000 being the white level, but when it is ultimately displayed on a display screen such as a CRT, the values shown in Figure 1. As shown in Figure 2, a CT value (a to b) in a specific range of interest is determined from among the 3000 levels of CT values, and
The CT values in this range are divided into gradations that can be displayed by the display device, so-called luminance data gradations (up to 256 gradations can be classified), and displayed on the screen. Furthermore, there is also a device that can display on the screen a CT value range of particular interest (hereinafter referred to as a blink region). There are two conventional blink area display methods as follows. One is a method in which the blink area is displayed at the maximum gradation of display brightness, as shown in Figure 2, and the other is a method in which the maximum brightness gradation of the CT value is a gradation lower than the maximum gradation of display brightness. This method displays the blink area at the maximum gradation of display brightness. However, the former method has the disadvantage that it is difficult to distinguish between the blink region and the CT value region with the maximum brightness gradation, while the latter method makes it easy to distinguish, but the CT value is displayed only up to the maximum value of the displayed brightness gradation. The problem is that not all of them are being used effectively. In addition, in conventional devices, when converting luminance data to gradation, the memory capacity becomes large because it has a conversion table covering the entire input data range, and the CT value of a specific range is The level value which is the center value of the CT value range,
It is specified by the width of the CT value range, that is, the window width (for example, 100), but the level value,
Each time the window width is changed, the table is rewritten accordingly using only software, which requires an extra buffer memory with the same capacity as the table.Furthermore, if you want to follow level value changes in real time, the rewriting process requires a lot of CPU time. The disadvantage was that the area was occupied. In view of these points, it is an object of the present invention to provide a display method that allows the display of CT values to effectively use up to the maximum display brightness gradation, and that also allows the display of blink areas to be easily distinguished. An object of the present invention is to provide a CT image display device that employs the following. In addition to the above-mentioned objects, another object of the present invention is to reduce the capacity of a table for brightness data gradation, reduce the burden on the CPU for rewriting the table, and speed up the rewriting of the data. The purpose of the present invention is to provide a conversion device. To achieve this purpose, in the present invention, the capacity of the table depends only on the window width, a separate register is used for conversion for level changes, and table rewriting due to width changes is performed. This will be done automatically by the hardware, and the blink area within the specified blink area will be
The present invention is characterized in that by blinking the CT values, the blink area and the CT value area having the maximum brightness gradation can be clearly distinguished, and furthermore, the display brightness gradation can be utilized to the fullest. The present invention will be explained in detail below using the drawings. FIG. 4 is a configuration diagram of main parts showing an embodiment of the CT image display 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 luminance data table, 40 is a second switch, and 50 is a table rewriting circuit. . The comparator 10 compares input data with a window area lower limit value, and this input data is image data expressed by CT values, and the image data is image data reconstructed by a computer (not shown). It is. By the way, in the present invention, several kinds of specific widths (for example, CT value) are used as the window width.
20, 40, 60, …, 500, 1000) are available,
Any one of these can be designated by a code number. The maximum window width (in this example,
1000). The comparator 10 compares the input data with the window lower limit value, but as shown in FIG. 5, if the input data is within a range smaller than the lower limit value, the output terminal is
The lower limit value of luminance data is outputted from _D2 , and conversely, the upper limit value of luminance data is outputted from the output terminal _D2 in a range larger than the value obtained by adding the CT value width of the table area to the lower limit value. Furthermore, when the input data exactly falls within the range of the table area, the deviation from the window lower limit value can be sent out from the output terminal _D1 . The first switch 20 connects the output terminal D ₁ of the comparator 10
or the rewriting address sent from the table rewriting circuit 50. When displaying images by television system, the output of the comparator 10 is selected and output except during the blanking period. During the blanking period, the address outputs of the table rewriting circuit 50 are selected and can be applied to the table 30 as address signals. The brightness data table 30 is displayed in the window.
Up to 256 from black to white as CT value increases
The luminance data of the gradation is set correspondingly.
The output of the switch 20 can be addressed and its contents can be read out. Also,
The contents of the table can be rewritten, and the rewriting data is provided by a table rewriting circuit 50. The second switch 40 selects either the output data of the table 30 or the D ₂ output of the comparator 10 and sends it out as the luminance data output. When the comparator 10 sends out the D ₂ output, When the _D2 output is selected and the _D1 output is sent out, the output of table 30 is selected. The table rewrite circuit 50 sends a rewrite address and rewrite data for rewriting the contents of the table 30 when the level value and window width are changed. FIG. 6 is a block diagram showing the details of one embodiment, in which 51 is an address counter, 52 is a step programm, 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 program 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 20, the gradation data and the output data increment value are stored in a ROM. is as shown in Table 1, and is configured so that a data increase value can be output by specifying a window width code and address.

【table】

Claims (1)

[Claims] 1 The reconstructed image on the CT device is
It is a CT image display device that divides reconstructed image data into predetermined gradations and converts it into luminance data in order to display it on the screen with appropriate contrast only around the value. A luminance data table that has a memory capacity sufficient for the maximum width and in which luminance data can be written and read is compared with the lower limit value of the window and the input reconstructed image data, and the input data is stored at the address of the luminance data table. means for dividing and outputting data into three types of data, a lower limit value of brightness data, and an upper limit value of brightness data; A table rewriting circuit that sequentially outputs addresses for writing to a brightness data table and brightness data of the window; a blink area setter that sets a blink area; and whether input CT value data is a CT value within the blink area. and a blink mode that controls the comparator to alternately switch between a normal brightness gradation display mode and a blink-on brightness gradation display mode at regular intervals when displaying the blink area in a blinking manner. - A CT image display device characterized by being equipped with a control circuit.