Method and structure for optimizing radiographic quality by controlling X-ray tube voltage, current focal spot size and exposure time
DCFirst 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
42 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. .Iadd.
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35. An x-ray apparatus comprising:
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means for generating x-rays, said means for generating having an operating anode to cathode voltage; means for showing an image of x-rays which have passed through an object being examined; means for determining thickness of said object; at least one sensor for detecting radiation passed through said object and through said means for showing an image, said at least one sensor generating sensor signals in response to said radiation; and means for receiving said sensor signals from said at least one sensor and receiving said thickness from said means for determining thickness, and based on said sensor signals and said thickness sending control signals which control said operating anode to cathode voltage. .Iaddend. .Iadd. - View Dependent Claims (36)
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37. Iadd. A method for optimizing an x-ray image from an x-ray apparatus comprising the steps of:
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positioning an object to be exposed; determining thickness of said object; operating said x-ray apparatus at an initial anode to cathode voltage; after a sampling time small in comparison to an expected total exposure time making a determination related to an optimum anode to cathode voltage for said object based on said thickness and on radiation passed through said object at said initial anode to cathode voltage, and changing said initial anode to cathode voltage to said optimum anode to cathode voltage; and continuing to operate said x-ray apparatus at said optimum anode to cathode voltage until an optimum visualization of said means for showing an image
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38. is achieved. .Iaddend. .Iadd.57. A method for optimizing an x-ray image as in claim 56 in which said initial anode to cathode voltage is changed to said optimum anode to cathode voltage directly after said sampling time. .Iaddend. .Iadd.58. A method for optimizing an x-ray image as in claim 56 further comprising the steps of:
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operating said x-ray apparatus at an initial current; after said sampling time determining an optimum current; and changing said initial current to said optimum current. .Iaddend. .Iadd.59. A method for optimizing an x-ray image as in claim 56, further comprising the steps of; operating said x-ray apparatus at an initial focal spot size; after said sampling time determining an optimum focal spot size; and changing said initial focal spot size to said optimum focal spot size.
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39. Iaddend. .Iadd.60. A method for optimizing an x-ray image as in claim 56 further comprising the step of calibrating a sensor before positioning said object. .Iaddend. .Iadd.61. A method for optimizing an x-ray image as in claim 60 further comprising additional calibration in the form of providing information from a second sensor while exposing said object. .Iaddend. .Iadd.62. A method for optimizing an x-ray image from an x-ray apparatus as in claim 56 in which said initial anode to cathode voltage is an average anode to cathode voltage for the type of object being exposed. .Iaddend. .Iadd.63. A method for optimizing an x-ray image from an x-ray apparatus as in claim 56 in which said initial anode to cathode voltage is an optimal anode to cathode voltage of a previous exposure. .Iaddend. .Iadd.64. A method for optimizing an x-ray image from an x-ray apparatus as in claim 56 in which said step of making a determination related to an optimum anode to cathode voltage comprises:
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determining the integral of voltage provided by a first sensor which detects radiation from said x-ray apparatus passing through said object; determining the integral of voltage provided by a second sensor which detects radiation from said x-ray apparatus not passing through said object; determining the ratio of said integrals; and determining from a table an attenuation factor corresponding to said ratio. .Iaddend. .Iadd.65. A method for optimizing an x-ray image from an x-ray apparatus as in claim 56 in which said step of positioning an object comprises positioning tissue. .Iaddend. .Iadd.66. A method for optimizing an x-ray image from an x-ray apparatus as in claim 56 in which said step of making a determination related to an optimum anode to cathode voltage comprises; determining the integral of voltage provided by said sensor which detects radiation passing through said object from said x-ray apparatus being operated at said initial anode to cathode voltage; and determining from a table an attenuation factor corresponding to said integral. .Iaddend. .Iadd.67. A method for optimizing an x-ray image from an x-ray apparatus as in claim 56 in which said object comprises tissue and said step of making a determination related to an optimum anode to cathode voltage comprises; determining the integral of voltage provided by said sensor which detects radiation passing through said tissue from said x-ray apparatus being operated at said initial anode to cathode voltage; and determining a tissue density corresponding to said integral. .Iaddend. .Iadd.68. A method for optimizing an x-ray image from an x-ray apparatus as in claim 56 in which said object comprises tissue and said step of making a determination related to an optimum anode to cathode voltage comprises; determining the integral of voltage provided by a first sensor which detects radiation passing through said tissue from said x-ray apparatus being operated at said initial anode to cathode voltage; determining the integral of voltage provided by a second sensor which detects radiation from said x-ray apparatus not passing through said tissue; determining the ratio of said integrals; and determining a tissue density corresponding to said ratio. .Iaddend.
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40. Iadd. . An x-ray apparatus comprising:
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means for generating x-rays, said means for generating having an operating anode to cathode voltage; means for compressing tissue; means for showing an image of x-rays which have passed through said tissue; at least one sensor for detecting radiation passed through said tissue and through said means for showing an image, said at least one sensor generating sensor signals in response to said radiation; 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
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41. operating anode to cathode voltage. .Iaddend. .Iadd.70. An x-ray apparatus as in claim 69 further comprising means for controlling anode to cathode current. .Iaddend. .Iadd.71. An x-ray apparatus as in claim 69 further comprising means for controlling focal spot size. .Iaddend. .Iadd.72. An x-ray apparatus as in claim 69 further comprising means for controlling exposure time. .Iaddend. .Iadd.73. A method for optimizing an x-ray image from an x-ray apparatus comprising the steps of:
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positioning and compressing tissue to be exposed; operating said x-ray apparatus at an initial anode to cathode voltage; after a sampling time small in comparison to an expected total exposure time, making a determination related to an optimum anode to cathode voltage for said tissue based on radiation passed through said tissue at said initial anode to cathode voltage, and changing said initial anode to cathode voltage to said optimum anode to cathode voltage; and continuing to operate said x-ray apparatus at said optimum anode to cathode voltage until an optimum visualization of means for showing an image is achieved. .Iaddend. .Iadd.74. A method for optimizing an x-ray image as in claim 73 further comprising; after said sampling time making a determination related to an optimum anode to cathode current for said tissue, and changing an initial anode to cathode current to said optimum anode to cathode current; and continuing to operate said x-ray apparatus at said optimum anode to cathode current until an optimum visualization of said means for showing an image is achieved. .Iaddend. .Iadd.75. A method for optimizing an x-ray image as in claim 73 further comprising; after said sampling time making a determination related to an optimum focal spot size for said tissue, and changing an initial focal spot size to said optimum focal spot size; and continuing to operate said x-ray apparatus at said optimum focal spot size until an optimum visualization of said means for showing an image is achieved. .Iaddend. .Iadd.76. An x-ray apparatus comprising; means for generating x-rays, said means for generating having an operating anode to cathode voltage; means for showing an image of x-rays which have passed through an object being examined; a first sensor for detecting radiation passed through said object and through said means for showing an image, and a second sensor for detecting radiation not passed through said object, said sensors generating sensor signals in response to said radiation; and means for receiving said sensor signals from said sensors and based on said sensor signals sending control signals which control said operating anode to cathode voltage. .Iaddend. .Iadd.77. An x-ray apparatus as in claim 76 further comprising means for controlling anode to cathode current. .Iaddend. .Iadd.78. An x-ray apparatus as in claim 76 further comprising means for controlling focal spot size. .Iaddend. .Iadd.79. An x-ray apparatus as in claim 76 further comprising means for controlling exposure time. .Iaddend. .Iadd.80. A method for optimizing an x-ray image from an x-ray apparatus comprising the steps of; positioning an object to be exposed; operating said x-ray apparatus at an initial anode to cathode voltage; after a sampling time small in comparison to an expected total exposure time, making a determination related to an optimum anode to cathode voltage for said object based on radiation passed to a first sensor through said object and on radiation passed to a second sensor not through said object at said initial anode to cathode voltage, and changing said initial anode to cathode voltage to said optimum anode to cathode voltage; and continuing to operate said x-ray apparatus at said optimum anode to cathode voltage until an optimum visualization of means for showing an image is
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42. achieved. .Iaddend. .Iadd.81. A method for optimizing an x-ray image as in claim 80 further comprising:
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after said sampling time making a determination related to an optimum anode to cathode current for said object, and changing an initial anode to cathode current to said optimum anode to cathode current; and continuing to operate said x-ray apparatus at said optimum anode to cathode current until an optimum visualization of said means for showing an image is achieved. .Iaddend. .Iadd.82. A method for optimizing an x-ray image as in claim 80 further comprising; after said sampling time making a determination related to an optimum focal spot size for said object, and changing an initial focal spot size to said optimum focal spot size; and continuing to operate said x-ray apparatus at said optimum focal spot size until an optimum visualization of said means for showing an image is achieved. .Iaddend. .Iadd.83. A method for optimizing an x-ray image from an x-ray apparatus comprising the steps of; positioning an object to be exposed; operating said x-ray apparatus at an initial anode to cathode voltage; after a sampling time small in comparison to an expected total exposure time making a determination related to an optimum anode to cathode voltage for said object, comprising; determining the integral of voltage provided by a sensor which detects radiation from said x-ray apparatus passing through said object, and determining from a table a value related to attenuation factor corresponding to said integral; changing said initial anode to cathode voltage to said optimum anode to cathode voltage; and continuing to operate said x-ray apparatus at said optimum anode to cathode voltage until an optimum visualization of said means for showing an image is achieved. .Iaddend.
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Specification