TOMOGRAPHIC APPARATUS

• US 3,770,955 A
• Filed: 09/14/1971
• Issued: 11/06/1973
• Est. Priority Date: 09/17/1970
• Status: Expired due to Term

• Current Assignee: Chuji Tomita, Kazuo Kobayashi, Mitsuo Okudaira, Yuji Miyazaki
• Original Assignee: Chuji Tomita, Kazuo Kobayashi, Mitsuo Okudaira, Yuji Miyazaki
• Inventors: Tomita, Chuji, Miyazaki, Yuji, Kobayashi, Kazuo, Okudaira, Mitsuo
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): Anderson, B. C.
• Application Number:
  US05/180,260
• Time in Patent Office: 784 Days
• Field of Search: 250/61.5,52
• US Class Current: 378/27
• CPC Class Codes: A61B 6/025 Tomosynthesis
• CPC Class Codes: A61B 6/447 the source unit or the detector unit being mounted to counterpoise or springs

Abstract

A tomographic apparatus comprising: a principal linkage supporting an X-ray source and a film so that they face each other and having pivot fulcrums between these two members for being swingable in the directions of both axes X and Y; two servo motors for causing the linkage to move in the directions X and Y; means for setting the travel paths of the said two members comprising a plurality of sets of cams provided rotatably on a single rotatable shaft; means for driving only a selected set of cams corresponding to the required paths of the said two members, and cam follower members associated with the said sets of cams, respectively; and adjusting means for comparing the positions of both the X-ray source and the film to be assumed successively in the paths set by the said setting means in the directions of X and Y with the positions of the principal linkage to be assumed successively on the said paths, and for actuating the servo motors until these two groups of positions are brought into agreement with each other. With this arrangement, it is possible to displace, on the established required paths during the X-ray irradiation, both the X-ray source and the film by a mere selection of the required set of cams and to thereby obtain a sharply focused tomogram of any desired region of the object while satisfactorily blurring unnecessary regions of the object not required on the tomogram, without needing any special technical training or experience in this particular field.

Claims

1. A tomographic apparatus for taking X-ray tomographs, comprising:

link means having supports thereof for supporting an X-ray source and a film so as to directly oppose each other along a line through an image point between them;

a base frame on which said link means is mounted with the mounting point in a position in a plane containing said image point for swinging movement for moving said supports in the directions of an axis X and an axis Y;

two servo motors on said base frame and coupled to said link means for moving the said link means in the swinging movement;

travel path setting means comprising at least one set of cams including a first cam for setting positions corresponding to positions on axis X and a second cam for setting positions corresponding to positions on axis Y on the paths of travel to be followed by the said X-ray source support and said film support, a rotatable cam shaft, a coupling mechanism for each set of cams for selectively coupling the cams of the set to said cam shaft, cam drive means coupled to said shaft, and cam followers engageable with said cams, respectively;

servo motor control means coupled to said servo motor means for controlling the operation of said servo motor means, and follow up means on which said cam followers are mounted and coupled to said servo motor control means for transmitting the motion of said cam followers during the course of their displacement to the control means for operating the servo motors to move the link means to the desired positions so that the paths which are to be followed by the X-ray source support and the film support in the directions of the axes X and Y are according to said travel path setting means, said follow up means being coupled to said link means for moving said cams and for actuating said control means in response to the movement of said link means for causing the control means to stop the operation of said servo motors when the desired movements of said link means have been completed;

whereby the X-ray source support and the film support are cause to follow the paths according to the travel path setting means.

2. A tomographic apparatus according to claim 1, in which there are a plurality of sets of cams, and said apparatus further comprises means for selectively activating the coupling mechanism for the respective sets of cams corresponding to the desired paths of travel of the X-ray source and the film, whereby only the set of cams corresponding to the desired path of travel is coupled to the base frame for the rotation of the said cams, whereby both the X-ray source and the film are moved to follow the desired paths of travel during the irradiation of X-rays by a mere selection of the appropriate set of cams.

3. A tomographic apparatus according to claim 2, in which the said cam means comprises means for controlling the rotation of the said cam shaft for rotating the selected set of cams so that both the X-ray source support and the film support are moved along the desired path from retreated positions relative to the object to be photographed to positions for starting the photography and that thereafter said supports are returned to their initial retreated positions via the positions at which the exposure of film is completed.

4. A tomographic apparatus according to claim 1, in which the said set of cams have cam faces having contour for causing an increase in velocity of travel of the x-ray source and the film during the course of the travel path of the X-ray source corresponding to regions of the object which it is not desired to photograph, said velocity being in excess of the velocity of movement of the X-ray source along the portions of the said path corresponding to the region to be photographed.

5. A tomographic apparatus according to claim 1, in which:

the said link means comprises;

a pantograph constituted by a parallellogram linkage having a first link arm and a second link arm, a rotatable shaft on which both link arms are pivotably mounted, said shaft being rotatably supported horizontally on the base frame, a first bridge arm and a second bridge arm connected between the ends of said link arms and located on opposite sides of said rotatable shaft in parallel relationship therewith, and another parallelogram linkage comprised of a link arm extension on the first link arm, a bride arm extension on the bridge arm which is adjacent to the first extension, a first auxiliary arm pivotably coupled at one end to the said link arm extension and a second auxiliary arm pivotably coupled at one end to the link arm extension and at the other end to said first auxiliary arm, said auxiliary arms being parallel with the link arm extension and the bridge arm extension respectively, the said X-ray source support being secured to the said second auxiliary arm;

an extension on the other bridge arm and said film holder being supported normally horizontally thereon;

one of said servo motors being coupled to one of the said link arms and to said rotatable shaft at a point between said two link arms and the other servo motor being coupled to one of the said link arms and to the said base frame between said two link arms, to thereby cause the said link means to move in the directions of both axes X and Y to move both the X-ray source and the film along the desired travel paths.

6. A tomographic apparatus according to claim 1, in which said follow up means comprises:

a follow up parallelogram linkage having one corner pivotably coupled to a point on the said link means and the diagonally opposite corner pivotably coupled to a fixed point on the base frame so that the movement of the said link means for moving the supports in the directions of the axes X and Y is transmitted to said follow up parallelogram linkage, two adjacent arms of said follow up parallelogram linkage adjacent said fixed point having joints therein dividing the arms into segments, said cam followers being mounted on the segments of said two arms which are connected to the other links of said follow up linkage, the other segments of the two arms engaging said servo motor control means for transmitting the motion of said cam followers thereto.

7. A tomographic apparatus according to claim 6, in which the said servo motor means are comprised of hydraulically operated cylinders and the said control elements are comprised of servo valve means.