X-ray or gamma ray systems or devices – Source support – Source cooling
Reexamination Certificate
2001-11-26
2003-12-30
Oen, William (Department: 2855)
X-ray or gamma ray systems or devices
Source support
Source cooling
Reexamination Certificate
active
06669366
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an X-ray examination apparatus which includes an X-ray detector and an X-ray source which are arranged on a supporting device. The invention also relates to an X-ray detector which includes a sensor unit that converts X-rays into electrical image signals and in which a sensor unit is adjoined by a processing unit that includes a plurality of amplifier units. The invention also relates to a method for cooling X-ray examination apparatus.
BACKGROUND OF THE INVENTION
The X-rays emitted by an X-ray source in imaging X-ray examination apparatus traverse a patient or object to be examined and are attenuated in conformity with the different thickness and chemical composition of the tissue or the bones to be examined. In the X-ray detector the X-rays are converted into light in a scintillating material or into charge carriers that can be detected directly.
X-ray examination apparatus are used, for example in the field of surgery and consist, for example, of a mobile console and a mobile supporting device which is attached thereto and accommodates on the one side an X-ray source and on the opposite side an image pick-up device or the X-ray detector.
With a view to achieving easy mobility, the weight of the entire system is compensated. To this end, balancing weights are provided in given locations. The power fed into the X-ray source is converted substantially completely into heat which is dissipated mainly via the housing of the X-ray source. Because the permissible ambient temperature of the X-ray apparatus may not exceed a given value, the mean power must be limited and the housing must have a sufficiently large surface area. However, the latter can be realized to a limited extent only because of the weight and the room that is required, for example for the surgery.
The image pick-up devices or X-ray detectors being used thus far and consisting of an X-ray image intensifier and a camera will be replaced in future by flat dynamic X-ray detectors. This development is described, for example in EP 440282. Such systems realize a considerable saving of weight that is of enormous importance to the mobility. However, in order to make this saving of weight effective for the entire system, a corresponding reduction of weight must also be realized for the X-ray source. The latter, however, is possible to a limited extent only. Inter alia the necessary dissipation of heat prevents an adequate reduction of weight to be achieved for the same amount of X-rays. The problems are worsened by the fact that a flat X-ray detector makes it possible to realize higher mean continuous powers.
EP 0182040 discloses a cooling device for a computed tomography apparatus. Because of their structural configuration, computed tomography apparatus produces a very large amount of heat which must be limited on the one hand to prevent influencing of the patient to be examined who is arranged within the ring and on the other hand to prolong the service life of the computer tomography apparatus, notably of the X-ray tube. Therefore, the X-ray source is cooled by means of a cooling medium. Because the X-ray source and the X-ray detector are mounted on a ring, the X-ray source is cooled by means of a system of ducts that is situated in the ring and contains oil. The oil that is heated by the dissipation of heat from the X-ray source is applied to the ring via a cooling medium outlet opening and is transported around the ring by a circulation pump so as to reach the X-ray source again via the cooling medium inlet opening. The path through the ring is used to cool the heated cooling medium. The cooling oil can also be cooled by channels in the ring that contain air. The cooling ducts are arranged in the stationary part of the ring. Cooling ribs that are provided on the mobile part of the ring project into the cooling ducts in the stationary part of the ring and are cooled therein, thus enabling cooling of the cooling oil present in the system of ducts. The present invention proposes direct cooling of the X-ray source.
DE 29510802 U1 describes a surgical X-ray diagnostic device in which the X-ray generator and the X-ray image intensifier are mounted on a C arm. Cooling of the X-ray generator is possible via a double-walled construction of the C arm.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a device in which the temperature in the X-ray detector can be kept constant and at the same time the overall weight of the overall X-ray examination apparatus can be kept small.
This object is achieved in accordance with the invention in that there is provided an X-ray examination apparatus which includes a supporting device, an X-ray detector and an X-ray source and a system of ducts which is coupled to a heat exchanger, is associated with the X-ray detector and the X-ray source and is intended to receive a cooling medium.
The invention is based on the idea that the operation of an X-ray detector is very stable and that it generates similar image signals when all of its components are subject to the same temperature. Assuming that the temperature in such an X-ray detector is not very high, a cooling medium that is used to keep the temperature constant will not be severely heated. The X-ray source produces considerably more heat than the X-ray detector. Therefore, the cooling medium that can be readily heated and is used first of all for keeping the temperature in the X-ray detector constant is used additionally for cooling the X-ray source. An additional cooling device for the X-ray source can thus be dispensed with, so that the complexity of an X-ray examination apparatus is considerably reduced and hence also its overall weight.
The cooling medium in a preferred embodiment of the device is applied to the X-ray detector via a first sub-duct system with a constant temperature.
It is thus achieved that the components in the X-ray detector operate under the same temperature conditions, so that uniformly amplified image signals are produced. Moreover, the internal temperature of the X-ray detector is kept low, so that the sensor unit for converting the X-rays into electrical signals that is situated within the X-ray detector operates in the range of highest sensitivity. The cooling medium takes up a first amount of heat in the X-ray detector; however, this amount is not very large so that the cooling medium is applied, without further cooling, to the X-ray source via a second sub-duct system for further cooling. After the cooling of the X-ray source, the heated cooling medium is applied to a heat exchanger in which it is cooled to the initial temperature.
The X-ray detector in a preferred embodiment of the invention is provided with temperature sensors which apply a temperature-dependent signal to the heat exchanger so as to enable temperature control. The heat exchanger is preferably arranged outside the supporting device; however, a compact heat exchanger can also be integrated in the C arm or be arranged on the C arm when the construction of the overall system is to be smaller.
From the heat exchanger the cooling medium, preferably water, is first applied to the detector at a low but constant temperature of, for example 20° C., in which it realizes the necessary temperature stabilization. The cooling liquid that has been slightly heated therein, for example to 25° C., is then transported to the housing of the X-ray source in which it takes up further heat. The X-ray source is accommodated in a housing and consists essentially of the X-ray tube. The high voltage transformer with rectifier may optionally be accommodated in the same housing; in that case it is not necessary to realize the power supply with a high voltage. The console accommodates the power supply and the control circuitry. After the cooling of the X-ray source, the cooling liquid is applied with a higher temperature to the heat exchanger in which it is cooled to a lower temperature again. The liquid may be routed via the supporting device or the C arm. The heat exchanger may have such a simple constr
Busse Falko
Van der Broeck Heinz
Koninklijke Philips Electronics , N.V.
Oen William
Vodopia John
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