X-ray or gamma ray systems or devices – Electronic circuit – X-ray source power supply
Utility Patent
1999-03-03
2001-01-02
Bruce, David V. (Department: 2876)
X-ray or gamma ray systems or devices
Electronic circuit
X-ray source power supply
C378S101000, C378S102000, C378S114000, C378S115000
Utility Patent
active
06169782
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an x-ray system and in particular to a portable x-ray system equipped with an internal power supply.
2. Description of the Prior Art
Known portable x-ray systems generally have an x-ray source which is usually an x-ray tube, a low storage voltage battery (typically several hundred volts) power supply and a voltage converter for stepping up the voltage supplied by the power supply to the high voltage (typically several tens of kilovolts(kV)) needed by the x-ray source to create a field in which electrons are accelerated before hitting a metal target and generating the x-rays. These systems are then used in conjunction with any one of a number of known image gathering devices, such as photographic plates or fluoroscopes to generate an x-ray image of an object, such as part of a patient in a hospital environment. Since the quality of the image thus created will generally depend on the penetration of the x-rays used and the exposure time (during which time any movement of the object will cause a blurring of the image), known x-ray systems usually provide a user with selectivity as to either or both of the dose and dose rate. The degree of selectivity of these parameters ultimately depends on the nature of the power supply used and in particular on the level and duration of the voltages that can be generated by the power supply.
One known type of portable x-ray system has an internal power supply having a storage battery arrangement formed by a number of individual lead/acid accumulators connected in series to provide the required output voltage to the converter, which usually includes a step-up transformer. This type of arrangement has the advantage that such accumulators, or similar battery-type energy storage media, provide a suitable voltage output over a relatively long time period. However, such batteries are relatively bulky and heavy which is a problem if the x-ray system is intended to be portable. This is particularly true if the system is required to generate a relatively high dose, short exposure time x-ray output, for example as is needed for short duration, deep penetration depth examinations. In this case a correspondingly large voltage (typically 300-400 V, needs to be supplied from the power source which requires between 25 to 33 bulky 12V lead acid accumulators, thus reducing the portability of the system.
Another known type of x-ray system is described in U.S. Pat. No. 3,878,394. In this known system, the battery store is used to charge a capacitor which, because of the electrical characteristics of capacitors, when discharged provides directly a sufficiently high voltage for use in the generation of a high dose, short exposure time x-rays, much more readily than is the case with the battery store. These same electrical characteristics, however, mean that a relatively large capacitance, which in practice usually represents a large number of capacitors, is needed if long exposure times are required, which is relatively expensive.
SUMMARY OF THE INVENTION
It is an object of the present invention is to provide an x-ray system in which some of the disadvantages of the known power supplies are reduced.
The above object is achieved in accordance with the invention in an x-ray system having a hybrid power supply that includes both a storage battery arrangement, for example rechargeable batteries such as lead/acid accumulators, and a capacitor power storage arrangement which are switchable during an exposure to provide an output from the supply that is generated by one or both (either sequentially or contemporaneously) of them. In this way a relatively high voltage, hence a short exposure time, can be achieved without the need for as high a number of batteries as would be required in a supply composed exclusively of storage batteries, and a long exposure time can be obtained without the need for as high a number of capacitors as would be required in a supply composed exclusively of capacitors. Thus an x-ray system having an increased flexibility in the choice of exposure time is provided while still remaining relatively portable and inexpensive.
Preferably the switching is conducted by, in sequence, first connecting the capacitor store and then the battery store to the input of the converter. This enables short exposure times to be used since power is taken initially from the capacitor supply which is better suited for providing a high dose short duration output as is necessary for short exposure times.
Means may be provided to connect an external alternating current power supply, for example the mains electricity supply, to charge the capacitor power store. This provides a further source of power supply to the x-ray source and may be used to extend the supply time of the battery power store.
Additionally or alternatively, the battery power store may be used to charge the capacitor store. This has the advantage that several exposures may be made before the power store has to be either replaced or, preferably, recharged using an external power source. This permits the portable operation of the x-ray system over an extended period of time.
REFERENCES:
patent: 3878394 (1975-04-01), Golden
patent: 4322623 (1982-03-01), Grady
patent: 4797907 (1989-01-01), Anderson
patent: 5111493 (1992-05-01), Siedband
patent: 5226064 (1993-07-01), Yahata et al.
patent: 5469350 (1995-11-01), Nishio et al.
patent: 5631814 (1997-05-01), Zak
Bruce David V.
Ho Allen C
Schiff & Hardin & Waite
Siemens-Elema AB
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