JPH0410788B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention is used in the field of digital subtraction systems added to X-ray television.

The present invention relates to a digital subtraction system for an X-ray TV apparatus in which differential images (subtraction images) before and after contrast agent injection are displayed.

(b) Prior art In digital subtraction systems (DSS), S/
The signal current Is of the image pickup tube of a television camera is attracting attention as one of the factors that determines the N ratio. Since DSS is often added to existing X-ray televisions, the type of fluorescence intensifier (II) and field of view size differ depending on the system, and even if the same type of II There are variations in performance,
It is necessary to set the aperture of the TV camera so that it always has the optimum Is for each system.

Conventionally, when selecting an aperture value by reading the Is value, a synchroscope was used to read the Is value, and the aperture value or ND (Neutral Density) filter was selected by trial and error or by using a model system in advance. This was done by referring to experimentally determined data (relationship between aperture value and Is value). In this way, conventional methods require manpower and effort, and the performance of IIs of the same type may vary, resulting in differences in image quality (differences in S/Z ratio) in the same system. . In addition,
With ND filters, the aperture range is fixed at 1/2, 1/4, and 1/8, so fine adjustment is not possible.

(c) Purpose An object of the present invention is to process the IS
It is an object of the present invention to provide a digital subtraction system capable of reading the Is value and outputting an electric signal corresponding to the aperture value that realizes the optimum Is value.

(D) Configuration The above purpose is to test the sample value obtained through the experiment of the signal current Is of the image pickup tube and the corresponding video signal level V, and the experiment of the signal current Is and the corresponding lens aperture value Fc of the television camera. means for inputting and writing data of each of the sample values obtained in the memory, interpolation calculation means for interpolating the data between the sample values stored in the memory, peak value detection means for detecting the peak value V of the video signal obtained by the calculation; This is achieved by providing an aperture value search means.

(E) Embodiments A preferred embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is an example of a partial circuit including a television camera and an A/D converter as main parts. FIG. 3 shows the relationship between the composite video signal and the peak value V. Figure 4 shows V-
The Is characteristic diagram, and FIG. 5 is the Is-aperture value Fc characteristic diagram.

12 is an X-ray tube, 14 is a high voltage generator, 16 is a subject, 18 is a fluorescence multiplier tube (II), 19 is a television camera lens aperture, 20 is a television camera head,
21 is an image pickup tube, 21' is a preamplifier, 22 is a camera control, 23 is an amplifier, 24 is a logarithmic amplifier, 26 is an A/D converter, 28 is a frame memory 1, 30 is a frame memory 2, and 32 is an arithmetic circuit. ,
34 is an enhancement circuit, 36 is a D/A converter, 38 is a VDR, 40 is a VTR, 42 is a monitor,
44 is a microcomputer, which is equipped with an arithmetic circuit, a control circuit, a memory, and an input/output port.
6 is a keyboard, and 48 is a monitor.

In FIG. 1 and FIG. 2, the operation of this embodiment is as follows.
First, the (1) sides of the switches SW1 and SW2 are turned on. Furthermore, the gains in the preamplifier 21' and the camera control 22 are all fixed constant, and the aperture 19 is opened.

In FIG. 1, first, several experimentally determined V-Is values (x marks) and Is-Fc values (x marks) as shown in FIGS. 4 and 5 are input from the keyboard 46. . Based on the input data, the computer 44 performs linear interpolation of these data or fits a high-order curve using the least squares method, holds the data as a continuous curve, and constitutes an interpolation calculation means.
Then, the simulated phantom, which is assumed to be a standard object, is subjected to X-ray irradiation under the usage conditions so as to achieve a predetermined II incident dose. In order to specify the dose as described above, the relationship between the X-ray conditions and the incident dose is determined experimentally under the usage conditions.

The video signal obtained by the X-ray exposure is A/D converted 26, and the final frame of the exposure is stored in the frame memory 28 shown in FIG. The microcomputer 44 obtains the peak value V of the video signal from the memory 28 (peak value detection means), and determines the lens aperture value Fc of the television camera from the detailed data table created from the data shown in FIGS. 4 and 5. is output as an electric signal (aperture value designation signal) (aperture value search means). In FIG. 1, it is output as a digital signal.

This aperture value designation signal is used, for example, to display the aperture value numerically on the monitor 48, or is used as a signal to control the aperture value in a system having an automatic aperture mechanism.

Although not shown, the microcomputer 44 includes a ROM memory, which stores a procedure or program according to the operation of the present invention. The microcomputer 44 also receives a timing control signal to operate in synchronization with the X-ray exposure.
CL will be sent. Further, for convenience of configuration, the keyboard 46, microcomputer 44, and monitor 48 are incorporated into a system controller and operation panel (not shown) of the DSS.

Although the present invention is mainly applied to the installation and adjustment of DSS systems, it can also be used to detect aging of II and TV camera image pickup tubes, that is, performance deterioration. At the time of installation, the Is value for a predetermined II incident dose is stored as an initial value in nonvolatile memory, and by comparing it with the Is value at that time during periodic inspections,
The performance deterioration can be understood.

(f) Effects The present invention has the effect that the optimal value of the signal current value Is of the image pickup tube can be easily and accurately set, which conventionally required a lot of manpower and time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a partial diagram thereof, FIG. 3 is an example of a decoded video signal, FIG. 4 is a V-Is characteristic diagram, and FIG. The diagram is
-Fc characteristic diagram. 19 is a lens aperture of the television camera, 21 is an image pickup tube, 28 and 30 are frame memories, and 44 is a microcomputer.

Claims (1)

[Claims] 1 Sample values obtained through an experiment between the signal current Is of the image pickup tube and the corresponding video signal level V, and sample values obtained through an experiment between the signal current Is and the corresponding lens aperture value Fc of the television camera, respectively. interpolation calculation means for interpolating the data between the sample values stored in the memory; and a means for calculating the peak value V of the video signal obtained from the image pickup tube by X-ray exposure. The present invention includes a peak value detection means for detecting a peak value, and an aperture value search means for outputting an aperture value Fc at which an optimum signal current value can be obtained from both the Is-V and Is-Fc characteristic tables obtained by the calculation. Digital subtraction, characterized by
system.