X-ray or gamma ray systems or devices – Electronic circuit – X-ray source power supply
Reexamination Certificate
2000-01-28
2001-09-18
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Electronic circuit
X-ray source power supply
C378S097000
Reexamination Certificate
active
06292537
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an X-ray diagnostic device which includes an X-ray generator for feeding an X-ray source and means for determining the dose applied during an X-ray examination of a patient.
2. Description of Related Art
An X-ray diagnostic device of this kind is known from DE-OS 2 124 035 (page 2, second paragraph). The dose is measured therein by means of an ionization chamber which is attached to an ionization chamber connected to the X-ray source. The ionization chamber has such a large surface area that it intercepts all X-rays emanating from the primary diaphragm even in the case of the maximum radiation field size that can be adjusted by means of the primary diaphragm. The output signal of the ionization chamber thus corresponds to the dose surface product measured in &mgr;Gy*m
2
.
The dose surface product is a purely physical quantity which corresponds to the surface integral of KERMA (Kinetic Energy Released in MAtter) in air. This physical quantity only conditionally provides information about the radiation load for the patient being examined or about the effective dose which takes into account the various risks of the individual organs or tissues in respect of stochastic irradiation. When exposed to the same applied dose surface product, for example, the X-rays will damage the bladder of a patient significantly more than the skull of the patient.
Citation of a reference herein, or throughout this specification, is not to construed as an admission that such reference is prior art to the Applicant's invention of the invention subsequently claimed.
SUMMARY OF THE INVENTION
Therefore, it is an object of the invention to construct an X-ray diagnostic device of the kind set forth in such a manner that the radiation load for a patient can be more accurately indicated during an X-ray examination. This object is achieved according to the invention in that there is provided a storage device in which a respective set of exposure and/or fluoroscopy parameters is stored for a number of organs, that each set includes, in addition to exposure or fluoroscopy parameters for the X-ray generator, a weighting factor which corresponds to the biological effect of the radiation on the relevant organ, and that there is provided an arithmetic unit for calculating the effective dose from the dose and the weighting factor.
A memory in which a respective set of exposure or fluoroscopy parameters is stored for a number of organs is customarily used in contemporary X-ray generators and is referred to as APR (Anatomically Programmed Radiography). For an X-ray exposure, the user enters the organ to be examined or the anatomical region (for example “lung p.a.”), the optimum exposure parameters (inter alia the voltage applied to the X-ray source) for an X-ray exposure of this organ then being fetched from the memory so as to be automatically adjusted.
The invention is based on the recognition of the fact that to each organ there can be assigned a weighting factor which is a measure of the biological effect of the dose during an X-ray examination of the relevant organ. The effective dose which is a measure of the biological effect of the X-rays in the patient can be calculated by multiplying said weighting factor by the dose determined during the X-ray examination (i.e. the KERMA in air).
The invention can be used not only for X-ray apparatus in which only X-ray images can be formed, such as the so-called Bucky devices, but also in X-ray apparatus with an exposure mode as well as a fluoroscopy mode. In contemporary apparatus of this kind the fluoroscopy parameters for different organs or anatomical regions can also be stored; in the case of a change-over to the X-ray exposure mode, the exposure parameters are then either derived from the fluoroscopy parameters or fetched from a separate memory containing the exposure parameters for the relevant organ.
The dose, or the dose surface product, can be measured by means of a suitable measuring chamber. The further embodiment additionally comprising means for measuring the geometrical parameters of the X-ray examination and means for calculating the dose from the geometrical parameters and the exposure or fluoroscopy parameters does not require such a measuring chamber; the dose is derived on the one hand from the exposure or fluoroscopy parameters (voltage applied to the X-ray source or the time integral of the current through the X-ray source, filtering etc.) and on the other hand from geometrical parameters of the X-ray examination (for example, the aperture of the X-ray beam).
A preferred embodiment of the means for measuring the geometrical parameters includes a measuring device for measuring the aperture of a primary beam diaphragm connected to the X-ray source.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be described in detail hereinafter with reference to a drawing which is a purely diagrammatic representation of an X-ray device according to the invention.
REFERENCES:
patent: 5625662 (1997-04-01), Toth et al.
patent: 2124035 (1972-11-01), None
Kim Robert H.
U.S. Philips Corporation
Vodopia John F.
Yun Jurie
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