Electron beam computed tomographic scanner system with helical or tilted target, collimator, and detector components to eliminate cone beam error and to scan continuously moving objects
First Claim
1. In a scanning electron beam computed tomographic system in which an electron beam is scanned across a target with a constant velocity to emit a fan beam of X-rays some of which X-rays may pass through an area defined by a reconstruction radius and having an object therein to be detected by a detector array, a method of eliminating cone beam error, comprising the following steps:
- (a) configuring and disposing said target and said detector array such that active regions of said target and said detector array are always diametrically opposite from each other;
wherein step (a) includes providing a planar target and a planar detector array and tilting said target and said detector array relative to a transverse axis that may include a vertical axis of said system to approximate a true helix configuration.
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Abstract
A scanning electron beam computed tomographic system eliminates axial offset between target and detector by disposing the target, collimator, and detector such that active portions of the target and detector are always diametrically opposite each other. This result is achieved by providing a helical target, collimator, and detector, or by providing planar target, collimator, and detector components that are inclined relative to the vertical axis such that active portions of the target and detector are always diametrically opposite each other. Either configuration eliminates cone beam error and the necessity to correct for same. Further, the system can provide multi-slice scanning of an object that is in constant motion at a critical velocity, without having to interpolate data. Conventional helical scanning may still be undertaken. Detector elements can be disposed axially to improve signal/noise ratio and to produce a cone beam cancellation effect.
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Citations
15 Claims
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1. In a scanning electron beam computed tomographic system in which an electron beam is scanned across a target with a constant velocity to emit a fan beam of X-rays some of which X-rays may pass through an area defined by a reconstruction radius and having an object therein to be detected by a detector array, a method of eliminating cone beam error, comprising the following steps:
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(a) configuring and disposing said target and said detector array such that active regions of said target and said detector array are always diametrically opposite from each other;
wherein step (a) includes providing a planar target and a planar detector array and tilting said target and said detector array relative to a transverse axis that may include a vertical axis of said system to approximate a true helix configuration.
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2. In a scanning electron beam computed tomographic system in which an electron beam is scanned across a target with a constant velocity to emit a fan beam of X-rays some of which X-rays may pass through an area defined by a reconstruction radius and having an object therein to be detected by a detector array, a method of eliminating cone beam error, comprising the following steps:
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(a) configuring and disposing said target and said detector array such that active regions of said target and said detector array are always diametrically opposite from each other;
(b) moving said object along a z-axis of said system with an object velocity equal to a critical velocity Vcrit during helical mode operation of said system;
wherein discrete equally-spaced slices of said object may be scanned without need to interpolate scan data acquired by said system. - View Dependent Claims (3, 4, 5, 6)
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7. In a scanning electron beam computed tomographic system operated in helical mode in which an electron beam is scanned across a target with a constant velocity to emit a fan beam of X-rays some of which X-rays may pass through an area defined by a reconstruction radius and having an object therein to be detected by a detector array, a method of acquiring scan data without a need to interpolate said data, the method comprising the following steps:
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(a) configuring and disposing said target and said detector array such that active regions of said target and said detector array are always diametrically opposite from each other;
(b) providing relative movement of said object to said system along a z-axis of said system at a critical velocity Vcrit;
wherein equally spaced object slices are acquired without need to interpolate said data. - View Dependent Claims (8, 9, 10)
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11. A scanning electron beam computed tomographic system in which cone beam error is eliminated, comprising:
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a helical shaped target;
a helical shaped detector array;
said target and said detector array disposed such that active regions of said target and active regions of said array are always diametrically opposite one another;
means for generating and sweeping an electron beam across said target with a constant velocity to emit a fan beam of X-rays some of which X-rays may pass through an area defined by a reconstruction radius and having an object therein to be detected by said detector array;
means for moving said object relative to a z-axis of said system with an velocity less than or equal to a critical velocity Vcrit;
wherein in helical mode operation of said system, if said velocity=Vcrit,scan data representing equally spaced slices of said object are obtained without need to interpolate said data. - View Dependent Claims (12)
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13. A scanning electron beam computed tomographic system in which cone beam error is eliminating, comprising:
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a planar target tilted with respect to a transverse axis that may include a vertical axis of said system to approximate a true helix;
a planar detector array tilted with respect to the same axis of said system to approximate a true helix;
said target and said detector array disposed such that active regions of said target and active regions of said array are always diametrically opposite one another; and
means for generating and sweeping an electron beam across said target with a constant velocity to emit a fan beam of X-rays some of which X-rays may pass through an area defined by a reconstruction radius and having an object therein to be detected by said detector array. - View Dependent Claims (14, 15)
means for moving said object relative to a z-axis of said system with a velocity less than or equal to a critical velocity Vcrit;
wherein in helical mode operation of said system, if said velocity=Vcrit scan data representing equally spaced slices of said object are obtained without need to interpolate said data.
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15. The system of claim 13, wherein said detector array includes elements displaced along an axial axis of said system.
Specification