Method and structure for optimizing radiographic quality by controlling X-ray tube voltage, current, focal spot size and exposure time
First Claim
1. An X-ray apparatus comprisingan X-ray tube having a cathode which emits electrons and an anode on which said electrons impinge and which is a source of X-rays, said tube having an operating voltage which is the voltage drop between said anode and said cathode, a tube current which is the current between said anode and said cathode, and a focal spot size which is the area of said anode on which said electrons impinge, and in which said voltage, said current and said current and said focal spot size have initial settings;
- a collimator having an opening through which said X-rays leaving said source in the direction of said opening may pass;
means for holding tissue to be examined in position for being irradiated;
means for showing an image of X-rays which have passed through said tissue;
at least one sensor which generates sensor signals for detecting radiation passed through said tissue and through said means for showing an image, and for calibrating said X-ray apparatus; and
means for receiving said sensor signals from said at least one sensor and based on said sensor signals sending control signals which control said operating voltage, said tube current, and said focal spot size.
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Abstract
A structure and method for providing optimum recording of X-ray images without need for experimenting to learn optimum X-ray tube voltage, current, anode focal spot size and exposure time. The method and structure of this invention sample the radiation passed through an object to be radiographed during a short portion of the total exposure time and adjust voltage, current and focal spot size so that the radiation delivered by the X-ray tube during the remainder of the exposure time will produce optimum contrast between structures within the object being radiographed, also optimum sharpness of the image and optimum darkening of a film, xerographic picture, fluoroscopic image, or other recording medium. The method and structure of this invention account for variations in absorption coefficient between one object to be radiographed and the next. This invention is particularly useful for medical applications, and in the medical field, particularly important in mammography.
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Citations
34 Claims
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1. An X-ray apparatus comprising
an X-ray tube having a cathode which emits electrons and an anode on which said electrons impinge and which is a source of X-rays, said tube having an operating voltage which is the voltage drop between said anode and said cathode, a tube current which is the current between said anode and said cathode, and a focal spot size which is the area of said anode on which said electrons impinge, and in which said voltage, said current and said current and said focal spot size have initial settings; -
a collimator having an opening through which said X-rays leaving said source in the direction of said opening may pass; means for holding tissue to be examined in position for being irradiated; means for showing an image of X-rays which have passed through said tissue; at least one sensor which generates sensor signals for detecting radiation passed through said tissue and through said means for showing an image, and for calibrating said X-ray apparatus; and means for receiving said sensor signals from said at least one sensor and based on said sensor signals sending control signals which control said operating voltage, said tube current, and said focal spot size. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 30, 31)
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24. A method for optimizing an X-ray image from an X-ray apparatus comprising
an X-ray tube having a cathode which emits electrons and an anode on which said electrons impinge and which is a source of X-rays, said tube having an operating voltage which is the voltage drop between said anode and said cathode, a tube current which is the current between said anode and said cathode, and a focal spot size which is the area of said anode on which said electrons impinge, and in which said voltage, said current and said focal spot size have initial settings; -
a collimator having an opening through which said X-rays leaving said source in the direction of said opening may pass; means for holding tissue to be examined in position for being irradiated; means for showing an image of X-rays which have passed through said tissue; at least one sensor which generates sensor signals for detecting radiation passed through said tissue and through said means for showing an image, and for calibrating said X-ray apparatus; and means for receiving said sensor signals from said at least one sensor and based on said sensor signals sending control signals which control said operating voltage, said tube current, and said focal spot size;
comprising the steps of;positioning said tissue; determining thickness of said tissue and providing said tissue thickness to said microprocssor; operating said X-ray apparatus at said initial settings; in a sampling time small in comparison to an expected total exposure time calculating optimum voltage, current and focal spot size settings for the tissue being exposed; at the end of said small sampling time changing voltage, current and focal spot size settings to said optimum voltage, current and focal spot size settings for the tissue being exposed; and continuing to operate said X-ray apparatus at said optimal settings until an optimum visualization of said means for showing an image is achieved. - View Dependent Claims (25, 26, 27, 28, 29, 32, 33)
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34. An X-ray apparatus comprising
an X-ray tube having a cathode which emits electrons and an anode on which said electrons impinge and which is a source of X-rays, said tube having an operating voltage which is the voltage drop between said anode and said cathode, a tube current which is the current between said anode and said cathode, and a focal spot size which is the area of said anode on which said electrons impinge, and in which said voltage, said current and said focal spot size having initial settings; -
a collimator having an opening through which said X-rays leaving said source in the direction of said opening may pass; means for holding an object to be examined in position for being irradiated; means for showing an image of X-rays which have passed through said object; at least one sensor which generates sensor signals for detecting radiation passed through said object and through said means for showing an image, and for calibrating said X-ray apparatus; and means for receiving said sensor signals from said at least one sensor and based on said sensor signals sending control signals which control said operating voltage, said tube current, and said focal spot size.
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Specification