Siemens Aktiengesellschaft

Siemens Aktiengeselleschaft

Heribert Amtmann

Hans Ebersberger

Hans-Joachim Greiner

Johann Seissl

Karlheinz Broenner

Hans-Jurgen Gerlach

Klaus Baeker

Guenther Eckardt

Hermann Forkel

Guenter Eckardt

An autoradiography system for obtaining exposures from, and reading the latent image stored in, stimulable phosphor foils includes a cassette which receives a preparation of low energy radiation emitting tissue to be examined and two stimulable phosphor foils separated by a shielding plate consisting of material permeable to high energy radiation, but impermeable to low energy radiation. The cassette is surrounded by a high radiation absorbing housing. The preparation is disposed against one of the foils, so that the low energy radiation therefrom forms a latent image on the adjacent foil, but cannot pass through the shielding plate to form an image on the other foil. Both foils will, however, record and form a latent image of high energy radiation which may not be absorbed by the cassette housing. One of the foils thus exhibits a latent image due solely to background or thermal radiation, while the other phosphor foil has a latent image corresponding to the tissue, as well as the background and thermal radiation. A processing circuit is included in a read out system having a subtraction stage which subtracts electronic signals corresponding to the two latent images from each other, so that a tissure image free of background and thermal radiation noise is obtained. Insensitivity to thermal noise is obtained by insulating and cooling the cassette.

Autoradiography system for stimulable phosphor foils

An exemplary embodiment comprises an image intensifier television chain and an image subtraction device, connected thereto, with three image memories. In two image memories, a blank image is stored, respectively, whereby the first blank image is automatically stored long before commencement of the rise of the contrast medium concentration. Through observation of the difference image in a fluoroscopy operation with a low dose rate, the time of the rise of the contrast medium concentration can be precisely located. Then a radiographic recording series follows with a high dose rate per image. This radiographic series may be retained in an on-line operation using a hard copy-series device. No subsequent off-line-operation is necessary.

Diagnostic radiology system for angiographic x-ray examinations

In an exemplary embodiment in order to establish the desired relationship between x-ray tube voltage and x-ray tube current, at least one series resistance is connected in the power path between the mains and the x-ray tube. A switching device for by-passing the series resistance is present which is controlled by a comparator for the actual value and setpoint value of the x-ray tube voltage in such a fashion that the series resistance is by-passed at the commencement of a radiograph as long as the actual value is smaller than the setpoint value.

X-Ray diagnostic generator in which the x-ray tube voltage is adjusted

In an exemplary embodiment, a rectifier bridge is inserted in the primary circuit of the high voltage transformer and has an electronic circuit for adjusting the primary current to adjust the amplitude of the x-ray tube voltage pulse waveform. The comparator of the control loop cooperates with a storage circuit which is connected to a release circuit which releases it by means of a release pulse in a short time interval within a half wave of the x-ray tube voltage waveform for storing an instantaneous value of the error until the next release pulse. The storage circuit drives the electronic voltage adjusting circuit to adjust the pulse amplitude without distorting its waveform.

One- or two-pulse x-ray diagnostic generator

In an exemplary embodiment, a circuit arrangement is present for the purpose of storage of information which corresponds to the switch-off phase angle of the supply voltage and for the purpose of switching-on at a phase position of the supply voltage which is equal to the respectively stored phase angle. In order to take into account the delay time between a switch-on signal and the actual switching-on of the high voltage transformer, two time systems are present, operating in relative displacement by the amount of the delay time, which time systems recognize the respective phase position of the supply voltage and cooperate with the memory as well as with a comparator, where the phase position present at the switch-off time is stored taking into account the delay time. The comparator delivers enabling signals for the switching-on of the high voltage transformer when the supply voltage reaches the switch-off-phase position which is pre-displaced by the amount of the delay time.

X-Ray diagnostic generator comprising switching means for switching-on

In an exemplary embodiment, a comparator is present which compares the actual value of the x-ray tube output with a time-varying rated value output of the function generator which controls the falling load characteristic, and effects the switching off of the x-ray tube to prevent an overloading thereof if the difference between the actual and the rated value of the x-ray tube output exceeds a predetermined limit for a time interval exceeding a predetermined minimum time span.

X-Ray diagnostic generator for operation with falling load

In an exemplary embodiment, the control circuit for controlling filament current to maintain x-ray tube voltage at a set point value is disabled near the beginning of an x-ray exposure by the cut-off of filament current to provide a falling load characteristic as a function of time. During the cooling of the x-ray tube filament, the x-ray tube voltage is maintained near its set point value by the timed switching of taps of a variable-ratio transformer to change the input voltage to the x-ray tube high voltage transformer, and by the coordinated changing of the loading of the primary circuit of such high voltage transformer, the control circuit for maintaining x-ray tube voltage at the set point value thereafter being placed in control of the filament current for the remainder of the x-ray exposure.

X-ray diagnostic generator in which the x-ray tube voltage is regulated

In an exemplary embodiment, in order to operate the X-ray diagnostic generator with a decreasing (or 'falling') load during an X-ray exposure, there is disposed in the primary circuit of the high voltage transformer a bridge rectifier in whose D.C. current branch there is disposed a series of networks each consisting of at least one resistance and one capacitor in parallel, and a switch for the purpose of switching the network into and out of the circuit. A timing control initially short circuits the resistance-capacitance networks to provide for maximum primary current at the start of an exposure, the shunt capacitor absorbing such primary current when each resistance-capacitance network is first switched into the circuit to initiate a relatively smoothly decreasing primary current as a function of time. As secondary voltage tends to decrease, the X-ray tube current is progressively reduced to maintain the selected X-ray tube voltage, the result being the desired smoothly decreasing load characteristic.

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Langensendelbach, Germany

Heribert Amtmann