JPS6330759B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes an X-ray generator, an image intensifier, a television system for capturing an output image thereof, and a system for detecting the brightness of the output image of the image intensifier and The present invention relates to an X-ray television fluoroscopic photographing apparatus comprising a phototimer device that controls the emission time and performs automatic photographing.

Automation of imaging in an X-ray television fluoroscopic imaging apparatus is generally performed using the configuration shown in FIG. In the figure, the X-rays generated by the X-ray tube X energized by the high voltage generator HT are irradiated onto the subject P, and at the same time, the image intensity set at the rear of the subject P is exposed. Fire (hereinafter abbreviated as image tube)
The image tube I.I is caused to emit light, and the average amount of light emitted within a limited predetermined range at the center of the image tube I.I is detected by a phototimer device consisting of a phototube PH and its controller Cp provided at its output section, The X-ray exposure time is controlled so that the detected amount remains constant.

In addition, when performing television fluoroscopy with the configuration shown in FIG.
The output image of the image tube II is captured by a television camera TC, and an X-ray fluoroscopic image of the subject P is displayed on a monitor cathode ray tube M.

However, as is clear from Fig. 1, the amount of X-rays transmitted through the subject P detected by the phototimer device is
Since it is an average luminescence amount within a limited range,
Even if the overall tone of the transmitted image (image brightness, composition, etc.) is approximately the same, the detection range located at the center of the transmitted image (generally, the detection range of transmitted X-ray amount is limited to the center of the image tube) When the ratio of bright and dark areas differs, the X-ray exposure time that is the object of control changes, and the density of the entire photograph changes significantly.

That is, in FIG. 2, the transmitted image B is the same as the transmitted image A.
Although there is no major difference in the image structure, the ratio of the shadow area to the detection range is different, so the X-ray exposure time in the photograph in case B is longer than in case A, and the density is higher. Note that the dotted circle indicates the detection part.

Therefore, even in automatic shooting, the photographic density is actually predicted empirically from the fluoroscopic image immediately before shooting, and the setting position of the film density setting device of the phototimer device is adjusted accordingly.
That is, at present, the magnitude of the film density setting reference signal is changed to keep the density of the desired portion as constant as possible.

This invention eliminates the unreasonableness of adjusting the density empirically for each exposure even though it is an automatic radiograph, and allows the entire transmitted image to be adjusted even if the ratio of bright and dark areas in the detection area for the amount of transmitted X-rays differs. It is an object of the present invention to provide an X-ray television apparatus that can always obtain photographs of a predetermined density if the conditions are the same.

This invention will be explained with reference to the embodiment shown in FIG. The apparatus shown in FIG.
a television device that captures and observes an output image, and a clamp that extracts only a portion of the video signal from the television device that corresponds to the detection range of the image tube I/I output portion, which is the main part of the present invention. Similarly to a peak hold circuit that holds the peak value of the video signal after passing through the gate circuit and the gate circuit for each TV field, the average value of the video signal after the gate is determined during the period in which the gate is open; an average value circuit that holds this average value during each television field; a division circuit that calculates the ratio of the average value to the peak value; and an output of the division circuit and the film density set by the film density setting device It consists of a multiplication circuit that calculates the product with the setting.

In the figure, the X-ray tube voltage setting transformer T for fluoroscopy or imaging, the high voltage generator HT, the relay RY ₂ that opens and closes the inputs of the X-ray tube X and the high voltage transformer H and T, its contact S ₄ , and relay RY ₄ and its contact S ₈ , relay
Delay relay RY ₁ opening and closing RY ₂ and relay RY ₄
and its contacts S ₂ , S ₃ , and opening/closing relay RY ₁ X
Radiation exposure switch S ₁ (X-RAY R) and relay
_Fluoroscopic X-ray exposure switch S ₇ (X-
RAY F), the image tube I, the phototube or photomultiplier tube PH installed at its output section, the capacitor C that integrates the output of the phototube PH, and the integrated voltage V integrated by the capacitor C as one of the inputs. a comparator A ₁ , and a thyristor that is operated by the output of this comparator A ₁ and shuts off the relay RY ₂
A well-known phototimer circuit comprising an SCR, a relay RY ₃ , and its contact _S6 , a television camera TC for capturing output images of image tubes I and I, a television camera controller CC, and a television monitor M have a phototimer device. It constitutes an automatic imaging type X-ray television device. The portion surrounded by a dashed line in the figure is provided according to the present invention, and its configuration will be explained in relation to its operation.

In the above configuration, when the fluoroscopic X-ray exposure switch _S7 is closed, the contact _S8 of the relay _RY4 is closed, the fluoroscopic X-ray generation circuit is closed, and the fluoroscopic image of the subject P is transmitted through the television camera TC and image tubes I and I. It is projected and observed on a television monitor. At the same time, the video signal output from the television camera controller CC is amplified by an amplifier 1, and a clamp circuit 2 removes the synchronizing signal portion. Only the video signal component from which this synchronization signal was removed is then composed of two monostable multivibrators, which are synchronized with the TV vertical synchronization pulse signal VD and delayed by a set time from the signal VD. It is composed of a vertical scanning gate circuit 5 that generates a pulse with a width of The gate circuit 3, which is controlled by a signal combined with the output of the horizontal scanning gate circuit 6 that generates a pulse of Only the video signal is taken out and amplified by an amplifier 4. The output of the amplifier 4 becomes the input to the peak hold circuit 7 which holds the peak value through the contact _S9 . Here, during observation of a fluoroscopic image, the peak value νp of the video signal corresponding to the detection range between each television field is maintained while repeating reset in synchronization with the vertical synchronization pulse VD. Then, when the quick photography X-ray exposure switch S ₁ is closed, the contact point
_S10 opens and the reset signal synchronized with the VD is cut off, and the peak hold circuit 7 continuously holds the peak value νp of the video signal immediately before snapshot shooting during the shooting period.

Further, the output of the amplifier 4 is simultaneously supplied to the average value circuit 8 during observation of a fluoroscopic image, and
The average value νm of the video signal during the open period is determined and held until the next video signal is supplied. Similar to the output νp of the peak hold circuit 7, the reset signal is cut off in synchronization with the operation of the quick-shooting X-ray exposure switch _S1 , and the average value νm of the immediately preceding video signal is the same as the output νp of the peak hold circuit 7. It is maintained continuously for a long time.

The peak value νp and average value νm of the video signal corresponding to the phototimer signal detection range detected during the observation of the fluoroscopic image are supplied to the divider circuit _A2 , and the ratio (νm/
νp) is calculated. Furthermore, the output (νm/νp) of the divider circuit _A2 is supplied to the multiplier circuit _A3 , which has one input as the DC voltage film density setting signal V set by the film density setter VR.
A ₃ calculates the product of both signals {(νm/νp)×V},
The output of this multiplier circuit _A3 is used as the reference value for film density setting when taking photographs, and is used as a comparator in the phototimer circuit.
A ₁ is supplied.

Next, when the quick-shot shooting start switch S ₁ is closed, RY ₁ operates after a delay time due to resistor R ₁ and capacitor C ₁ , its contact S ₂ opens, and contact S ₈ of relay RY ₄ opens, and the fluoroscopic X The line is interrupted and the contact is made at the same time
S ₃ and contact S ₄ of relay RY ₂ are closed and the imaging X-rays are emitted. Similarly, the reset contact _S5 of the capacitor C opens to form a photocurrent integration circuit of the phototimer section, and receives a signal from the phototube PH. During the delay time caused by the resistor _R1 and capacitor _C1 , the film F is transferred to the image tube I as shown in the figure.
It is sent to the front of I.

Let i be the photocurrent from the phototube PH, that is, the average value in the phototimer signal detection range, and consider the detection range subdivided, and assume the photocurrent from the brightest part, and let it be I. Then, the ratio between the average value i of the photocurrent and the assumed peak value I is set as α.

That is, i/I=α On the other hand, like the phototube PH, the television device also inputs the image tube I/I output image during fluoroscopic image observation, so the average value νm and the peak value of the video signal corresponding to the detection range are The ratio of νp is also equal to α.

That is, νm/νp=α Next, if the X-ray exposure time when the phototimer is operated with the average value i of the photocurrent as input is t ₁ , then t ₁ =Cν/i At the same time, with the peak current as input, the phototimer is Let t ₂ be the exposure time when it is assumed that the is activated, t ₂ =Cν/I where ν represents the integrated voltage of the integrating capacitor C.

Here, in the embodiment of the present invention, the multiplication circuit is used as the film density setting reference value of the phototimer circuit.
Since it is configured to give the output of _A3 {(νm/νp)V}, the integral voltage ν of the integrating capacitor and (νm/νp)V become ν=(νm/νp)V=αV, and X Since the radiation exposure stop operation is performed, in this case, the above t ₁ is expressed as follows.

t ₁ = C (αV) / i = CV / (i / a) Since i / I = α, t ₁ = CV / I Here, for t ₂ , νm = νp, and the following relationship is found.

ν={νm/νp)V}=V where ν...integrated voltage of the integrating capacitor C. Therefore, t ₂ =CV/I Therefore, t ₁ =t ₂ , that is, the X-ray exposure time becomes equal to t ₂ .

Therefore, even if the ratio of bright areas to dark areas occupying the detection area is different, if the overall tone of the transmitted X-rays is uniform, a photograph with a predetermined density can always be obtained.

As described above, the present invention makes the film density setting standard value during automatic shooting using a phototimer a function of the ratio of the peak value to the average value within a period corresponding to the phototimer signal detection range of the video signal of the television device. Therefore, the phototimer performs an X-ray exposure time control operation to keep the concentration of the brightest part in the detection range constant.

Therefore, according to the present invention, unlike the conventional automatic radiographing system X-ray television apparatus of this kind, when taking a snapshot,
Variations in film density due to the fact that the dose transmitted through the subject is detected as the average value of the image intensifier output;
Contrast media, etc. even at the same site and in the same body position.
The film density does not change greatly depending on the size of the area occupied by the image of the portion where the X-ray absorption is extremely large in the detection section. As a result, there is no need to predict the film density for the next photographing based on the fluoroscopic image and change the setting position of the density setting device.

Furthermore, conventionally, the average output of the image tube I/I is changed by changing the X-ray irradiation field using an aperture device. The size was limited to less than the minimum irradiation field so as not to be affected. Moreover, even if the detection range is limited in this way, the influence of the irradiation size cannot be ignored due to the structure of the image tube or the influence of scattered radiation, so it is necessary to change the film density of the phototimer device in conjunction with changing the size. The set reference value had to be changed, but according to the present invention, this is no longer necessary. Moreover, since the size of the detection range can be arbitrarily set to be large to a certain extent, the phototimer device can take a large input and improve the stability of its operation.

In the above embodiment, the output image of the image tube is detected by the phototube during photography, but the phototube may be omitted and the video signal from the television camera may be input to the integrating capacitor. However, in this case, since there is a delay in the television system, the configuration as in the embodiment is more accurate.
Radiation exposure time control operation can be performed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of an automatic X-ray television fluoroscopic imaging device, FIG. 2 is an explanatory diagram of the relationship between a fluoroscopic image and a detection unit, and FIG. 3 is a block diagram showing an embodiment of the present invention. It is a diagram. X...X-ray tube, P...subject, F...film, I/I...image intensifier (image tube), P/H...phototube, C...integrating capacitor, _A1 ...comparison TC...TV camera, M...TV monitor, CC...TV camera controller, 1, 4...Amplifier, 2...Clamp circuit, 3...Gate circuit, 5...Vertical scanning gate circuit, 6 ...Horizontal scanning gate circuit, 7...Peak hold circuit, 8...Average value circuit, _A2 ...Division circuit (arithmetic circuit), _A3 ...Multiplication circuit (arithmetic circuit), HT...High voltage transformer , RY ₁ to RY ₄ ... relay, S ₁ ... X-ray exposure switch for imaging, S ₇ ... X-ray exposure switch for fluoroscopy.

Claims (1)

[Claims] 1. In a device in which a phototimer device is coupled to an X-ray television device consisting of an image intensifier and a television system, and automatic photographing is performed by the phototimer, a specific area is a circuit that generates an electric signal corresponding to the peak value and average value of the television video signal; a divider circuit that calculates the ratio of the peak value and the average value; 1. An X-ray television apparatus comprising: a multiplier circuit for calculating the product of film density setting signals, the output of said multiplier circuit being used as a film density setting reference value of a phototimer device.