Medical radiographic apparatus

Abstract

In a computer-assisted tomography (CAT) apparatus, in which a fan-shaped X-ray distribution is rotated about the patients body, it is possible to use a ring of stationary detectors disposed to receive the radiation after passage through the body. In this arrangement the ring of detectors is of smaller radius than the locus of motion of the radiation source. It would appear that this would cause the detectors to obscure the body from the radiation. An arrangement disclosed moves out of the radiation beam those detectors which would present an obstruction so that only those required to collect radiation lie in the beam.

Description

Claims

1. Medical radiographic apparatus, for investigating a cross-sectional slice of a patient's body, including at least one x-ray tube and means for supplying electrical energy to the at least one x-ray tube, locating means for locating the at least one x-ray tube in relation to the patient's body so that a fan-shaped distribution of x-radiation is directed towards said slice, scanning means for rotating said at least one x-ray tube around the patient's body to direct the radiation towards said slice from a plurality of different directions, detector means comprising a plurality of detector devices, sensitive to said radiation, disposed along an arcuate path surrounding, or partly surrounding, the patient's body, the detector devices being substantially immobile in the direction of rotation of said at least one-x-ray tube, means locating said detector devices such that said arcuate path is closer to the patient's body than the at least one x-ray tube throughout the rotational movement of said at least one x-ray tube, and means for moving detector devices for the time being disposed at the same side of the patient's body as the at least one x-ray tube so that they do not interrupt the detection of said radiation by detector devices for the time being disposed at the opposite side of the patient's body to said at least one x-ray tube.

2. Apparatus according to claim 1 in which the detector devices are distributed over 360.degree. about the patient's body.

3. Apparatus according to claim 1 including a plurality of anti-rotation means, which are compliant in a direction perpendicular to the direction of rotation of said at least one x-ray tube but not compliant in a direction tangential thereto, connecting the detector ring member with stationary parts of the apparatus to maintain the detector devices substantially immobile in said direction of rotation.

4. Apparatus according to claim 3 in which the antirotation means comprise flexible metal strips.

5. Apparatus according to claim 1 including a detector ring member, on which the detector devices are mounted to intercept the radiation after passage through the patient's body, and in which the means for moving detector devices is arranged to move said detector ring member.

6. Apparatus according to claim 5 including a source ring member, disposed with its axis coincident with the axis of rotation of the at least one x-ray tube and linked to said at least one x-ray tube to rotate therewith and in which the means for moving detector devices comprise a guiding means mounted thereon to maintain the detector ring member with its axis inclined to the axis of rotation of the at least one x-ray tube.

7. Apparatus according to claim 5 including resilient means disposed to urge the detector ring member into the path of the x-radiation and in which the means for moving detector devices comprise a cam member, linked to the at least one x-ray tube, arranged to deflect the detector ring member against said resilient means.

8. Apparatus according to claim 7 in which the resilient means comprise a plurality of spring means.

9. A medical diagnostic x-ray machine for producing an x-ray picture of the anatomy of a slice which extends along a planar section through the patient including:

at least one x-ray tube producing a fan-shaped distribution of x-radiation directed at the patient and passing through the slice and means for supplying electrical energy to said at least one x-ray tube;

means for orbiting the at least one x-ray tube about the patient to cause the origin of the radiation to move along a source orbit which surrounds the slice and is coplanar with the slice;

detectors of x-radiation which face the slice and are arranged in a detector ring which surrounds the slice and is within the source orbit; and

means for nutating the detector ring in synchronism with the orbiting of the at least one x-ray tube, and therefore with the motion of the origin along the source orbit, to prevent interception of the x-radiation from the origin by detectors which are between the at least one x-ray tube and the slice, but to cause interception of the x-radiation from the origin by detectors facing the side of the slice which is away from the at least one x-ray tube.

10. A medical diagnostic x-ray machine as in claim 9 including a collimator secured relative to the x-ray tube to orbit, together with the x-ray tube, about the patient, said collimator facilitating the containment of said x-radiation in a fan-shaped distribution, said collimator being outside the detector ring.

11. Medical radiographic apparatus for investigating a cross-sectional slice of a patient's body, the apparatus including: at least one x-ray tube generating a fan-shaped distribution of x-radiation and means for supplying electrical energy to said at least one x-ray tube; locating means for locating the at least one x-ray tube, in relation to the patient's body, so that the said radiation is directed towards said slice; scanning means for orbiting said at least one x-ray tube about the patient's body so as to direct x-radiation towards said slice from a plurality of different directions; detector means comprising a detector ring member, of radius less than the radius of the orbit of the at least one tube, and a plurality of detector devices, sensitive to the radiation, mounted on the detector ring member to intercept the radiation after passage through the slice; deflecting means, linked to said at least one x-ray tube, arranged to deflect the detector ring member during the orbit of the at least one x-ray tube to prevent interruption of the radiation thereby prior to passage through the slice, and means arranged to prevent motion of said detector ring member in the direction of orbit of said at least one x-ray tube.

12. Medical radiographic apparatus for investigating a cross-sectional slice of a patient's body, the apparatus including: at least one x-ray tube generating a substantially planar fan-shaped distribution of x-radiation and means for supplying electrical energy to the at least one x-ray tube; locating means for locating the x-ray tube in relation to the patient's body so that the x-radiation is directed towards said slice; scanning means for orbiting the at least one x-ray tube about an axis perpendicular to the slice so as to direct the x-radiation towards the slice from a plurality of directions; detector means comprising a plurality of detector devices disposed around the patient's body in a detector ring, of radius less than the orbital radius of the at least one tube, about an axis inclined to the orbital axis of the at least one x-ray tube; deflecting means, linked to the x-ray tube, for nutating the axis of the detector ring about said orbital axis to cause the detector devices to intercept the radiation only after it has passed through the body; and means for substantially preventing rotation of the detector devices about the nutating axis.

13. A medical diagnostic x-ray machine for producing an x-ray picture of a slice which extends along a section through a patient comprising:

an x-ray tube and means for supplying electrical energy to the x-ray tube, and an x-ray collimator secured to the x-ray tube, said x-ray tube and x-ray collimator together producing a fan-shaped distribution of x-radiation which is directed at the patient and passes through the slice.

means for rotating both the x-ray tube and the x-ray collimator, as a unit, around the slice to thereby cause the fan-shaped distribution of x-radiation to pass through the slice along a number of different means directions,

an array of detectors of x-radiation which surrounds the slice, with the individual detectors facing the slice, said array being within the orbits inscribed by the x-ray tube and x-ray collimator in rotating around the slice, and

means for nutating the detector array in synchronism with the rotation of the x-ray tube and the x-ray collimator around the patient to prevent interception of the x-radiation by detectors which are between the x-ray tube and the slice but to cause interception of the x-radiation by detectors facing the side of the slice which is away from the x-ray tube. .Iadd.

14. An X-ray diagnostic apparatus for producing transverse layer images of a radiography subject with an X-ray measuring arrangement comprising an X-ray source which produces a fan-shaped X-ray beam penetrating the radiography subject, the cross-sectional extent of the beam, perpendicular to the layer plane, being equal to the layer thickness and, in the layer plane, being of such a magnitude that the entire layer is penetrated with radiation, and comprising also a radiation receiver which detects the intensity of radiation emanating from the layer, said radiation receiver being constructed as a circular ring into which the radiography subject may be inserted and comprising a series of detectors, with means for changing the direction of the axis of symmetry of the X-ray beam to effect a scanning operation, and with a measured value converter for the transformation of the signals supplied by the radiation receiver during a scanning operation into a layer image, characterized in that the X-ray source is arranged outside the radiation receiver, in that the radiation receiver has swiveling mounting means, and guide means acting on said radiation receiver for swiveling that particular part of the circular ring forming the radiation receiver, which is required to detect the X-radiation issuing from the radiography subject, into the X-ray beam. .Iaddend. .Iadd.15. An X-ray diagnostic apparatus for producing transverse layer images of a radiography subject with an X-ray measuring arrangement comprising an X-ray source which produces a fan-shaped X-ray beam penetrating the radiography subject, the cross-sectional extent of the beam, perpendicular to the layer plane, being equal to the layer thickness and, in the layer plane, being of such a magnitude that the entire layer is penetrated with radiation, and comprising also a radiation receiver which detects the intensity of radiation emanating from the layer, said radiation receiver being constructed as a circular ring into which the radiography subject may be inserted and comprising a series of detectors, with means for shifting the instantaneous origin point of the X-ray beam and for simultaneously changing the direction of the axis of symmetry of the X-ray beam to effect a scanning operation, and with a measured value converter for the transformation of the signals supplied by the radiation receiver during a scanning operation into a layer image, characterized in that the X-ray source provides an instantaneous origin point for the X-ray beam for each direction of the axis of symmetry thereof which is outside of the circular ring forming said radiation receiver, the radiation receiver having mounting means accommodating shifting movement of the circular ring forming said radiation receiver such that for each direction of the axis of symmetry of the X-ray beam the part of the circular ring which is adjacent the instantaneous origin point for such X-ray beam is laterally offset from such X-ray beam, and guide means for positioning said circular ring forming said radiation receiver such that for each instantaneous origin point the adjacent part of the circular ring is laterally offset from the X-ray beam while the part of the circular ring required to detect X-radiation issuing from the radiography subject is disposed in the path of the X-ray beam from such instantaneous origin point. .Iaddend. .Iadd.16. X-ray diagnostic apparatus for the examination of a transverse layer of a radiography subject, comprising

(a) X-ray source means for producing respective fan-shaped X-ray beams penetrating the radiography subject from respective different directions, with origin points of the respective fan-shaped beams being equidistant from a central axis, the cross-sectional extent of the beams, perpendicular to the layer plane, being equal to the layer thickness, and the lateral extent of the beams in the layer plane corresponding to the lateral extent of the layer to be examined so that the entire layer is penetrated with radiation upon production of each beam,

(b) patient support means for locating a radiography subject such that the fan-shaped X-ray beams are directed from the X-ray source means toward the layer to be examined from the respective different directions, and such that the central axis intersects the layer to be examined,

(c) scanning means for effecting irradiation of the layer to be examined from respective different directions to produce respective scans thereof and operable for effecting a rotational displacement of the direction from which the layer is scanned by sequentially producing fan-shaped X-ray beams from the X-ray source means which are directed toward the layer from successive angularly offset positions about said central axis, and operable during a scanning operation for producing a sufficient number of scans of the layer to be examined so as to enable production of an image thereof,

(d) detector means comprising a series of detectors, sensitive to said radiation, disposed at successive positions about the patient support means and arranged such that radiation of each of the fan-shaped beams will impinge on a plurality of successive detectors of said series without requiring rotational movement of said detectors in the direction of rotational displacement of said scanning means during a scanning operation of said scanning means,

(e) said detectors of said series being substantially immobile in the direction of rotational displacement of the scanning means throughout a scanning operation of said scanning means,

(f) means for locating said detectors so that the distance of each detector from said central axis is less than the distance of the origin points of the fan-shaped beams from the central axis during a scanning operation of said scanning means, and

(g) means for moving potentially beam obstructing detectors of said series for the time being disposed at the same side of the central axis as an origin point of a fan-shaped beam to be produced so that such detectors do not obstruct the detection of radiation from such origin point by detectors of said series disposed on the side of the central axis opposite to that of such origin point. .Iaddend. .Iadd.17. X-ray diagnostic apparatus according to claim 16 with said detector means comprising a circular radiation receiver having said series of detectors disposed at successive positions therealong, said means for moving potentially beam obstructing detectors of said series being arranged for moving said

circular radiation receiver as a unit. .Iaddend. .Iadd.18. X-ray diagnostic apparatus according to claim 17, with said means for moving comprising a ring rotatable about said central axis during a scanning operation and coupled with said radiation receiver to maintain the axis of the radiation receiver inclined to said central axis such that potentially beam obstructing detectors of said series are offset from each sequentially produced fan-shaped X-ray beam. .Iaddend. .Iadd.19. X-ray diagnostic apparatus for the examination of a transverse layer of a radiography subject, comprising

(a) X-ray source means for producing respective fan-shaped X-ray beams penetrating the radiography subject from respective different directions, with origin points of the respective fan-shaped beams being equidistant from a central axis, the cross-sectional extent of the beams, perpendicular to the layer plane, being equal to the layer thickness, and the lateral extent of the beams in the layer plane corresponding to the lateral extent of the layer to be examined so that the entire layer is penetrated with radiation upon production of each beam,

(b) patient support means for locating a radiography subject such that the fan-shaped X-ray beams are directed from the X-ray source means toward the layer to be examined from the respective different directions, and such that the central axis intersects the layer to be examined,

(c) scanning means for effecting irradiation of the layer to be examined from respective different directions to produce respective scans thereof and operable for effecting a rotational displacement of the direction from which the layer is scanned by sequentially producing fan-shaped X-ray beams from the X-ray source means which are directed toward the layer from successive angularly offset positions about said central axis, and operable during a scanning operation for producing a sufficient number of scans of the layer to be examined so as to enable production of an image thereof,

(d) detector means comprising a series of detectors, sensitive to said radiation, disposed at successive positions so as to completely encircle the patient support means and arranged such that radiation of each of the fan-shaped beams will impinge on a plurality of successive detectors of said series without requiring rotational movement of said detectors in the direction of rotational displacement of the scanning means during a scanning operation of said scanning means,

(e) said detectors of said series being substantially immobile in the direction of rotational displacement of the scanning means throughout a scanning operation of said scanning means,

(f) means for locating said detectors so that the distance of each detector from said central axis is less than the distance of the origin points of the fan-shaped beams from the central axis during a scanning operation of said scanning means, said detectors of said series including with respect to each origin point, an adjacent series of detectors located on the same side of the central axis as such origin point, and a remote series of detectors located on the opposite side of the central axis from such origin point, and

(g) means constructed so as to laterally offset, with respect to each origin point, the adjacent series of detectors relative to the fan-shaped X-ray beam therefrom, so that the fan-shaped beam from each origin point impinges on the radiography subject without obstruction by such adjacent series of detectors, and so as to position the remote series of detectors with respect to each origin point so that the fan-shaped beam from each origin point impinges on such remote series of detectors. .Iaddend. .Iadd.20. An X-ray diagnostic apparatus for producing transverse layer images of a radiography subject with an X-ray measuring arrangement comprising an X-ray source which produces a fan-shaped beam penetrating the radiography subject, the cross-sectional extent of the beam, perpendicular to the layer plane, being equal to the layer thickness and, in the layer plane, being of such a magnitude that the entire layer is penetrated with radiation, and comprising also a radiation receiver which detects the intensity of radiation emanating from the layer, said radiation receiver being constructed as a circular ring into which the radiography subject may be inserted and comprising a series of detectors, with means for changing the direction of the axis of symmetry of the X-ray beam to effect a scanning operation, and with a measured value converter for the transformation of the signals supplied by the radiation receiver during a scanning operation into a layer image, characterized in that the X-ray source is arranged outside the radiation receiver, in that the radiation receiver has mounting means permitting the radiation receiver to incline in any direction, and guide means acting on said radiation receiver for swiveling that particular part of the circular ring forming the radiation receiver, which is required to detect the X-radiation issuing from the radiography subject, into the X-ray beam. .Iaddend.