Ohio Nuclear, Inc.

Technicare Corporation

Other

John Covic

Arthur B Braden

Samuel K Taylor

John J Kuwik

Roland W Carlson

Joseph B Richey

Thomas R McBride

Glen Leininger

In a rotating fan beam tomographic scanner there is included a variable detector aperture housed within a radiation scatter shield. The scanner includes a diverging source of penetrating radiation which is directed toward a patient receiving section for passing a fan shaped beam of radiation through a planar section of the patient. The incident radition beam is attenuated during its passage through the patient receiving section and the transmitted beam passes from the patient receiving section until it impinges on a plurality of detectors for eventual reconstruction into a visible image. The variable detector aperture controls the thickness of the fan shaped beam and hence limits the amount of radiation impinging on the detectors. The aperture includes a pair of elongated beam thickness defining members having an opening therebetween and rotatable relative to the scanning plane. The opening between the two members in a direction transverse to the scanning plane defines the thickness of the attenuated fan beam passing therethrough.

Variable detector aperture

Disclosed is a collimator for a tomographic scanner which performs the collimator function of dividing a fan of radiation into a multiplicity of finger beams and the attenuator function of causing a generally bell-shaped radiation energy distribution across a scan circle. The collimator has larger effective apertures for forming radiation into finger beams to traverse the center of the scan circle than for forming finger beams to traverse the edges of the scan circle. The width of the collimator apertures are defined by radially oriented vanes arranged along a circular arc. By offsetting the radiation source from the geometric center of the circular arc, the vanes defining the width of some apertures are more skewed than others relative to the radiation paths.

Eccentric source collimator assembly for rotating source CT scanner

In a rotating fan beam tomographic scanner there is included an adjustable collimator and shutter assembly. The assembly includes a fan angle collimation cylinder having a plurality of different length slots through which the beam may pass for adjusting the fan angle of the beam. It also includes a beam thickness cylinder having a plurality of slots of different widths for adjusting the thickness of the beam. Further, some of the slots have filter materials mounted therein so that the operator may select from a plurality of filters. Also disclosed is a servo motor system which allows the operator to select the desired fan angle, beam thickness and filter from a remote location. An additional feature is a failsafe shutter assembly which includes a spring biased shutter cylinder mounted in the collimation cylinders. The servo motor control circuit checks several system conditions before the shutter is rendered openable. Further, the circuit cuts off the radiation if the shutter fails to open or close properly. A still further feature is a reference radiation intensity monitor which includes a tuning-fork shaped light conducting element having a scintillation crystal mounted on each tine. The monitor is placed adjacent the collimator between it and the source with the pair of crystals to either side of the fan beam.

Adjustable collimator

The method of determining collimator aperture efficiency for a computerized tomographic scanner having a plurality of radiation detectors positioned along a detector arc, a source of radiation having a focal spot having radiation flux distribution positioned across a scan circle from at least part of the detector arc, and a collimator having a plurality of apertures arranged in a collimator arc around said source. Also disclosed is a tomographic scanner having a circular detector arc, a radiation source moveable along a circular arc and an arcuate collimator having apertures in which the width of the collimator aperture in the geometry of the system has high efficiency. The ratio of the detector radius to the source radius, to the collimator radius, to the aperture width is 36:24.3;9.4:0.024.

Method of determining collimator aperture efficiency and apparatus with

In a CT scanner having a rotating source of radiation and a series of stationary radiation detectors spaced about the axis of rotation of the source, an eclipsing shutter mechanism restricts the width of the diverging fan pattern of radiation to that portion of the patient scan circle which is intermediate the array of stationary detectors and the orbiting source. The eclipsing shutter may include a single elongated slit aperture for flooding the scan circle with radiation or a plurality of smaller apertures defining a collimator for continuously training each one of a plurality of discrete diverging beams in the fan pattern on a single stationary detector during rotation of the source for as long as the separate beam intersects the scan circle. An epicyclic gear train powered by the rotation of the source drives the shutter mechanism in a counter-rotation and causes the collimator to keep each beam aimed at a respective detector.

Shutter for rotating source CT scanner

An automatic variable collimator which controls the width and thickness of X-ray beams in X-ray diagnostic medical equipment, and which is particularly adapted for use with computerized axial tomographic scanners. A two-part collimator is provided which shapes an X-ray beam both prior to its entering an object subject to radiographic analysis and after the attenuated beam has passed through the object. Interposed between a source of radiation and the object subject to radiographic analysis is a first or source collimator. The source collimator causes the X-ray beam emitted by the source of radiation to be split into a plurality of generally rectangular shaped beams. Disposed within the source collimator is a movable aperture plate which may be used to selectively vary the thickness of the plurality of generally rectangular shaped beams transmitted through the source collimator. A second or receiver collimator is interposed between the object subject to radiographic analysis and a series of radiation detectors. The receiver collimator is disposed to receive the attenuated X-ray beams passing through the object subject to radiographic analysis. Located within the receiver collimator are a plurality of movable aperture plates adapted to be displaced relative to a plurality of fixed aperture plates for the purpose of varying the width and thickness of the attenuated X-ray beams transmitted through the object subject to radiographic analysis. The movable aperture plates of the source and receiver collimators are automatically controlled by circuitry which is provided to allow remote operation of the movable aperture plates.

Variable collimator

Rotary safety shutter mechanisms for use in computerized tomographic X-ray scanners of the type wherein a source of radiation and a detector means are mounted for movement on opposite sides of a medium in order that the radiation passes through successive planar sections of medium and is attenuated and detected to give an output. The safety shutter mechanisms are arranged to be positioned adjacent the outlet aperture of the radiation source to selectively block the outlet upon occurrence of a predetermined condition. Two different embodiments of safety shutter mechanisms are disclosed. In each embodiment, the mechanism comprises a housing mounted adjacent the outlet aperture and having a through passage through which radiation from the source can pass. A cylindrical shutter member is carried in the housing transversely of the passage and mounted for rotary movement between a first position which permits the flow of radiation from the source and a second position which blocks the flow. In the first embodiment, the shutter member is moved from the second to the first position by a linear solenoid connected with the shutter member through a crank which is continually biased to move the shutter to the second position. In the second embodiment, the shutter member is actuated to the first position by a rotary solenoid aligned with the axis of rotation of the shutter member and directly coupled thereto.

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Wickliffe, OH, United States of America

John Covic