JPS5875987A - X-ray television method and device - 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 The present invention relates to an X-ray television method and apparatus. X
Ray television equipment converts an X-ray image into a video signal using, for example, a conventional X-ray image intensifier camera tube cascade (U.S. Pat. No. 4,149,082).
Or it includes a large area X-ray imaging tube (US Pat. No. 4,161,735) having X-ray sensitivity immediately after it.

In X-ray television, it is important that only the X-ray image of the subject is displayed on the monitor, and that images (artifacts) caused by the image transmission system are not displayed. Thus, the X-ray vision used, for example, in the device according to US Pat. It must pass a very strict selection process. An even distribution of the target layer is essential for displaying an X-ray image of a subject on a monitor without artifacts for medical diagnostic purposes. However, when creating a target audience, uneven distribution, which causes artifacts, is unavoidable. This causes artifacts in the image on the monitor, mainly as small flecks.

The indispensability of selection in order to achieve a sufficiently good production of the target layer is the main reason why special image pickup tubes for X-ray television equipment have not been able to gain a foothold on the market so far. . As long as it is a normal image pickup tube that is sensitive to light, even defective products that cannot be used for X-ray equipment can be used for other industrial television equipment. However, with special image pickup tubes that are sensitive only to X-rays, defective products cannot be used for other purposes, so the cost of defective products must be factored into the cost of good products. Costs will be significantly higher. It is particularly important to completely reduce the defective rate in an X-ray vidicon in which a large-area target layer is provided in order to adapt the dimensions of the captured image to the dimensions of the subject for medical diagnosis.

In addition to the above-mentioned flecks of the target layer of the image pickup tube, artifacts also occur due to other parts of the X-ray television apparatus. For example, in an X-ray image isotensifier tube cascade, large area non-uniformities exist due to non-ideal electronic scanning or X-ray image intensifier irregularities.

SUMMARY OF THE INVENTION An object of the present invention is to provide an X-ray television method and an apparatus for implementing the same, which make it possible to display an X-ray image of a subject without artifacts, particularly flecks, caused by the image transmission system.

This object is achieved according to the invention by the method defined in claim 1. The device according to the invention for carrying out this method is also constructed as indicated in claim 3.

Advantageous embodiments of the method according to the invention are set out in the second patent claim, and advantageous embodiments of the device according to the invention are set out in the second patent claim.

The present invention is based on the fact that it is almost impossible to fabricate a semiconductor target layer for a bidicon that has a large area and is free from flex. are doing. According to the invention, noise signals caused during imaging or due to other X-ray image transmission threads (X-ray image intensifier, objective lens, etc.) are compensated for by electronic countermeasures. This compensation can be carried out very effectively, especially by using digital circuit technology.

The invention will be explained in more detail below by means of embodiments shown in the drawings.

FIG. 1 shows an X-ray television apparatus having an X-ray fluoroscope on a support plate 2 for viewing a patient 1 with X-rays from an X-ray source 3. A high voltage source 4 is attached to the X-ray source 3 and is equipped with the necessary means.

On the side of the patient 1 opposite the X-ray source 3, an X-ray image intensifier image tube cascade 5 or an X-ray image tube 5' (see FIG. 2) is arranged. This imaging device is 5 or 5
' is connected to a monitor 7 or 7' via a conductor 6 or 6'. The monitor is on the one hand an imager 5 or 5'
on the other hand, a device 8 containing the power supply unit and the compensation circuit according to the invention necessary for the operation of the video signal, and on the other hand a device 9 necessary for the visualization of the video signal.

In FIG. 2, the digital circuit for artifact compensation included in the device 8 in FIG. 1 is shown in principle, surrounded by a dashed line with the reference numeral 8'.

In this circuit, a video signal applied from an imaging device 5 or 5' is converted into a digital signal by an analog-to-digital converter 10, and then applied to a digital memory 11 online (in real time). The compensation circuit 8' further includes a digital memory 14, a subtraction circuit 16, a threshold circuit 20, an average value forming circuit 19, a switching device 21 and a digital-to-analog converter 22.

The digital signals from the analog-to-digital converter 10 or the digital memory 11 are first temporarily stored in another digital memory 14 .

To this end, aerial imaging, that is, imaging is performed with no patient located in the X-ray path. In this case, the digital signal is temporarily stored in the digital memory 11 or directly applied to the digital memory 14 via the conductor 15. Digital memories 11 and 14 therefore also contain the gray value (eg, 8-bit amplitude depth) of the image point.

Thereafter, actual imaging is performed by transmitting X-rays through the patient.

The video signal obtained at this time is converted into a digital signal by an analog-to-digital converter 10 and then provided to a digital memory 11 as well.

A subtraction circuit 16 subtracts the digital signal from the aerial image taken from the memory 14 from the digital signal from the actual image taken from the memory 11 . However, it is also possible to provide a digital signal directly from the analog-to-digital converter 10 via the conductor 15 to the subtraction circuit 16, from which the digital signal from the memory 14 is subtracted. Even in the case of the above-mentioned deviation, a digital signal from which noise signals caused by the image transmission system have been removed appears at the output end of the subtraction circuit 16. Subtraction circuit 16
A circuit may be provided after the subtraction circuit 16 to avoid a negative video signal occurring after the subtraction in .

If aerial imaging is performed again with the same X-ray intensity after aerial imaging,
Since the input signals to both subtraction circuits 16 are identical, the signal produced at the output of the subtraction circuit as a result of subtraction should indicate zero. In this case, the dose can be increased, for example by a factor of 10, so that the quantum noise becomes negligible.

If actual imaging is performed after aerial imaging, the output terminal of the subtraction circuit 16 will have a signal proportional to the X-ray transparency of the patient at the location where there are no artifacts in the semiconductor layer, that is, where there is no strong fleck. live. Weak flecks that do not add to the image of the patient and exceed the capacity of the semiconductor layer disappear already after a simple subtraction. dashed line 30
Due to the bridge shown in FIG. 1, a significantly improved image can be displayed on the monitor even with a device that does not include the averaging circuit 19.

However, due to strong noise, the transmission path leading to the semiconductor layer 5'' of the image pickup tube 5 or the analog-to-digital converter 10, especially at the point where the X-ray image intensifier of the cascade device 5 has flecks, is affected by the influence of the flecks. If the digital output of the subtraction circuit 16 shows zero or
It may no longer be proportional to the light transmittance. The circuit elements 19, 20, and 21 shown in FIG. 2 are provided so that noise can be compensated even in such a case.

First, let us consider the case where the amplitude of the flakes in the semiconductor layer 5'' of the image pickup tube 5' is significantly different from the amplitudes of other image points in the aerial image.The output signal of the digital memory 14. It is applied to a threshold circuit (amplitude discriminator) 20 having a threshold value, which distinguishes image points belonging to flecks from other image points. As a result, the signal to be applied to the monitor is selected via the switching device 21.

The output signal of the subtraction circuit 16 is first applied to an average value forming circuit 19, which forms an average value of the amplitudes of the image points adjacent to the image point in question. In this case, at least four image points directly adjacent to the image point in question may be used for forming the average value, or a large number of image points over a wider range may be used for forming the average value. A signal sent from the memory 31 on the output side of the threshold circuit 20 to the average value forming circuit 19 via the conductor 23 prevents image points within the fleck from being used for forming the average value and forming an incorrect average value. The signal obtained at the output of the average value forming circuit 19, which is kept free, is applied to a switching device 21. This switching device also has a subtraction circuit 1.
A signal from 0 is also provided via conductor 18. The switching device 21 connects the output signal of the average value forming circuit 19 and the subtraction circuit 16.
It is determined which of the output signals should be applied to the digital-to-analog converter 22 for visualization. Incision device 21
is controlled by a threshold circuit 20 and passes the output signal of the average value forming circuit 19 to a digital-to-analog converter 22 for image points within the fleck.

Integration over a plurality of X-ray images can be performed in memory 11 or in memory 14 in a manner that suppresses quantum noise in the X-ray images and noise in electronic circuits such as video amplifiers. This integration forms an average value of the noise over a plurality of X-ray images, making it possible to suppress the noise. Memory 14 may be integrated within memory 11.

A conductor 23 connects the threshold circuit 20 to the average value forming circuit 19.
If the subtraction circuit 16 is connected to the subtraction circuit 16 and the subtraction circuit 16 is omitted together with the conductor 17, the compensation of artifacts by the circuit elements 19, 20 and 21 can also be carried out independently of the subtraction in the subtraction circuit 16. However, this presupposes that the image quadrant within the fleck has a significantly different amplitude from the other image points. The signal within the fleck should be canceled and replaced by the average value.

It is also possible to omit one of the two digital memories 14 and 11 and use the conducting wire 15 or 24 in its place. This is based on the fact that one of the two signals required by the subtraction circuit 16 can be used directly without being stored. However, in this case a multiple evaluation of the image nucleus is not possible. Instead, the advantage is that the memory 11 or 14 can be omitted.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an X-ray television apparatus including a compensation circuit according to the present invention for displaying images without artifacts caused by the image transmission system, and FIG. 2 is a circuit diagram of the principle of the compensation circuit according to the present invention. It is. 1...Each patient, 2...Patient support plate. 3... X-ray source, 4... High voltage source, 5... X-ray image intensifier image pickup tube vertically attached device, 5'... X-ray image pickup tube, 5
″...Semiconductor layer, 7, 7'...Monitor, 8...Appendix layer, 8'...Compensation circuit, 9...Video signal visualization device, 10...Analog-digital converter , 11
, 14... Memory, 16... Subtraction circuit, 19... Average value forming circuit, 20... Threshold circuit, 21... Switching device, 22... Digital-to-analog converter, 31...
··memory.

Claims (1)

[Claims] 1) In the X-ray television method, in order to display an image without artifacts, a signal obtained by aerial imaging without a subject is transmitted through the subject by X-rays. An X-ray television method characterized in that the signal is subtracted from the signal obtained by actual imaging, and in some cases, the average value of the intensity of the actual imaging signal around the location is substituted for a location where the intensity of the noise signal is high. . 2) In the first process, the signal obtained by aerial imaging and stored is subtracted from the signal obtained by actual imaging, and there is only a pure noise signal without the part caused by X-ray images due to flakes of the target layer, etc. Through a switching device controlled by a signal obtained from the noise signal via a threshold circuit, the average value of the surrounding area is applied to the monitor at the point of fleck, and the original value at other points is applied to the monitor. 2. The X-ray television method according to claim 1, wherein a surrounding average value is substituted by substituting the surrounding average value. 3) To enable image display without artifacts in an X-ray television device that includes an imaging device that converts an X-ray image into a video signal and a monitor that visually displays the video signal obtained thereby. , imaging device (5, 5
′) and the monitor (9), an artifact compensation digital circuit device that operates adaptively and in real time is inserted, and this circuit device is sequentially connected to an analog-to-digital converter (10), an average value forming circuit (19), and the monitor (9). )
and a switching device (21), a digital-to-analog converter (22) is provided, and an average value forming circuit (1) is provided.
9) is provided with a threshold circuit (20) which is directly fed with the switchgear (21) signal and produces an output signal only when it exhibits a strong artifact; 21) is controlled to switch the output signal of the average value forming circuit (19) to a monitor. 4) The X-ray television apparatus according to claim 3, characterized in that a memory [11] is connected between the analog-digital converter (10) and the average value forming circuit (19). . 5) A connecting conductor and one threshold circuit (
Claim U] Scope No. 4, characterized in that another memory (14) is provided between the input conductor (20) and the input conductor (14).
X-ray television apparatus as described in . 6) The X-ray television apparatus according to claim 4 or 5, wherein both memories are digital memories. 7) In order to control the substitution of the mean directivity, another memory (31) is provided for the address of the image point where noise is present. X gland television equipment. 8) The X-ray television apparatus according to claim 4, characterized in that a subtraction circuit (16) is connected between the memory (11) and the average value forming circuit (19).9) 9. An X-ray television set according to claim 8, characterized in that, after the subtraction circuit (16), a circuit is present for avoiding the occurrence of negative video signals after subtraction. 10) The X-ray television apparatus according to claim 4, wherein the first memory (11) also has a function of integrating and averaging a plurality of X-ray images. 11) X-ray television device according to claim 5, characterized in that the second memory (14) is integrated into the first memory (11). 12) The X-ray television apparatus according to claim 7, wherein the second memory (14) also has a function of integrating and averaging a plurality of X-ray images.