US3838287A

US3838287A - Fluoroscopic localization system for angular radiography

Info

Publication number: US3838287A
Application number: US00413442A
Authority: US
Inventors: D Barrett; R Chrapkowski
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1973-11-07
Filing date: 1973-11-07
Publication date: 1974-09-24
Anticipated expiration: 1991-09-24

Abstract

A diagnostic x-ray table has a film cassette supported on a Bucky carriage beneath the table top. A fluoroscopic image tube is fixedly located below the Bucky carriage. An x-ray tube is mounted above the table top for being translated and angulated correspondingly for providing oblique view radiographs. For tomographic procedures and for oblique radiographs a fulcrum bar couples the x-ray tube to the Bucky carriage, so the central ray of the x-ray beam always coincides with the center of the film. The pivot axis of the fulcrum bar is vertically adjustable so it may extend laterally through any selected layer of a patient reposed on the table top, through the plane of a film in the cassette and through the plane of the sensitive surface of the image intensifier tube. During angular radiography, the fulcrum axis can be located in the plane of the image tube wherein automatic means are provided for shifting the Bucky in the same direction as the x-ray tube so that the area being radiographed corresponds with the image viewed by means of the image tube.

Description

United States Patent 91 Barrett et a1.

[451 Sept. 24, 1974 FLUOROSCOPIC LOCALIZATION SYSTEM FOR ANGULAR RADIOGRAPHY [75] Inventors: David M. Barrett, Brookfield; Ralph K. Chrapkowski, St. Francis, both of Wis.

[73] Assignee: General Electric Company,

Schenectady, NY.

[22] Filed: Nov. 7, 1973 [21] App]. No.: 413,442

[52-] US. Cl 250/445, 250/444, 250/490 [51] Int. Cl. GOln 23/00 [58] Field of Search 250/442, 444, 446, 445,

Primary ExaminerArchie R. Borchelt Assistant ExaminerB. C. Anderson Attorney, Agent, or Firm-Ralph G. Hohenfeldt; Fred Wiviott [57 ABSTRACT A diagnostic x-ray table has a film cassette supported on a Bucky carriage beneath the table top. A fluoroscopic image tube is fixedly located below the Bucky carriage. An x-ray tube is mounted above the table top for being translated and angulated correspondingly for providing oblique view radiographs. For tomographic procedures and for oblique radiographs a fulcrum bar couples the x-ray tube to the Bucky carriage, so the central ray of the x-ray beam always coincides with the center of the film. The pivot axis of the fulcrum bar is vertically adjustable so it may extend laterally through any selected layer of a patient reposed on the table top, through the plane of a film in the cassette and through the plane of the sensitive surface of the image intensifier tube. During angular radiography, the fulcrum axis can be located in the plane of the image tube wherein automatic means are provided. for shifting the Bucky in the same direction as the x-ray tube so that the area being radiographed corresponds with the image viewed by means of the image tube 4 Claims, 9 Drawing Figures PATENTEUSEPZMQM FKBB FiGZ

PAIENIED 55 241924 SHEEF 3 0F 5 QUE FLUOROSCOPIC LOCALIZATION SYSTEM FOR ANGULAR RADIOGRAPHY BACKGROUND OF THE INVENTION This invention relates to diagnostic x-ray tables.

X-ray tables that are designed for performing radiography with the central x-ray normal to the patient supporting surface as well as tomography and angular radiography, usually support a film cassette on a Bucky carriage underneath the x-ray table top. The x-ray tube is mounted over the table top on an independent tube support or on an arm extending from a tube stand which is integral with the table. The independent support or integral stand as the case may be are movable relative to the table top. For radiography with the central x-ray perpendicular to the table top or patient support the focal spot of the x-ray tube is directly over the center of the film in the cassette beneath the table top. The tube support and the Bucky can be interlocked to maintain this alignment.

For tomography, a fulcrum bar is used to connect the x-ray tube to the Bucky carriage. The elevation of the axis of the fulcrum bar is adjustable so it can be made to coincide with any plane of interest in a patient supported on the table top. As is well known, during tomography, the x-ray tube is moved lengthwise of the table top in one direction in which case the fulcrum bar turns and causes the Bucky carriage to move in the opposite direction since the tube and Bucky carriage are on opposite sides of the fulcrum axis. Hence, all planes above and below the plane which contains the fulcrum axis are blurred on the radiographic film and the plane which contains the fulcrum axis is sharply imaged since it experiences no relative motion. In many tomographic tables, the lowest elevation to which the fulcrum axis may be adjusted is the top surface of the table top since there is nothing of interest to radiograph beneath the surface.

In some x-ray tables that are adapted for angular radiography, that is, taking a view through the patient at an angle instead of perpendicularly, as is done when it is desired to localize an embedded object or to view under an otherwise intervening part of the anatomy,

the fulcrum axis of the bar can be adjusted to the level of the film plane but no lower than this level. With this adjustment, the x-ray tube may be shifted longitudinally through an arc and angulated so that the central x-ray beam always points at the center of the film which is held stationary for this technic. The x-ray tube is adjusted to its final longitudinal and angulated position before a radiograph is initiated.

In radiographic x-ray tables that are adapted for fluoroscopic localization using an x-ray image intensifier tube the latter is typically fixedly mounted with its sen sitive input surface at a certain distance beneath the plane of the film in the cassette and with the center of this input surface in the same vertically lateral plane as the fulcrum axis of the fulcrum bar. When using this system with the fulcrum bar attached and with the central x-ray normal to the patient support surface, the center of the fluoroscopic input surface and the film center both coincide with the central x-ray beam regardless of the height of the fulcrum axis. In certain prior art x-ray apparatus it is possible and necessary to lower the fulcrum axis to the film plane to permit very slight angulation of the central ray with the least possible relative shift of the fluoroscopic image relative to the radiographic image assuming there is no film cassette in the Bucky tray and the Bucky carriage has a suitable opening in its bottom so as to not attenuate the x-ray image beam. However, due to the physical separation of the sensitive surface of the image intensifier tube from the film plane, in this prior art apparatus angular positioning of the central x-ray beam at larger angles results in the central ray intersecting the image intensifier input plane at a point which is at a considerable distance from the center. In other words, during angular fluoroscopy and radiography with prior art x-ray apparatus, the area recorded on the radiographic film does not correspond exactly with that which had been viewed fluoroscopically by means of the image intensifier tube.

SUMMARY OF THE INVENTION A primary object of the present invention is to overcome the above-noted problem and to provide means for obtaining accurate correspondence between an image recorded on a radiographic film and an image viewed by way of an image intensifier tube system at any position or angle which the system is capable of attaining.

How this general object and other more specific objects are achieved will appear in the course of the more detailed description of an illustrative embodiment of the invention which will be set forth hereinafter.

In general terms, the invention is characterized by coupling an x-ray tube and a Bucky carriage together by means of a fulcrum bar whose rotational axis is adjustable to coincide with the input plane of the image intensifier device. The fulcrum bar is coupled to the Bucky carriage above the fulcrum axis so that when the x-ray tube is shifted either to the right or left of the center of the table and angulated for angular radiography, the Bucky and film cassette supported thereon will shift in the same longitudinal direction as the x-ray tube to thereby maintain coincidence between the image on the image tube and the image recorded on the film.

A more detailed description of a preferred embodiment of the invention will now be set forth in reference to the drawings.

- DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a diagnostic x-ray table adapted for performing a variety of x-ray technics including angular fluoroscopy and radiography in accordance with the invention;

FIG. 2 is a front elevation view of the x-ray table showing the x-ray tube stand in solid line in its position for perpendicular radiography and also showing it in phantom in one of its angular radiography positions, the fulcrum axis being adjusted to the level of the film plane;

FIG. 3 is a side elevation of the x-ray table depicted in the previous figure but with the fulcrum axis adjusted to its lowest position;

FIG. 4 is an elevation view, partly in section, of a mechanism in the table for adjusting the elevation of the fulcrum bar pivot axis;

FIG. 5 is a side elevation view of the assembly shown in the preceding figure, partially in section, and with some parts removed;

FIG. 6 is a transverse section taken on a line corresponding with 66 in FIG. 5;

FIG. 7 is a side view of the x-ray tube support arm isolated from the apparatus and with the x-ray tube omitted;

FIGS. 8 and 9 are diagrams which are useful for explaining the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT The general features of a diagnostic x-ray table adapted for improved angular radiography and fluoroscopy, in accordance with the invention will now be discussed in reference to FIGS. l-3 primarily. These figures show a diagnostic x-ray table comprising a floor mounted table body or base assembly 10. There is a table top assembly 11 mounted on base 10. The top assembly comprises rectangularly arranged frame members such as the one marked 12. An x-ray permeable top panel 13 for supporting a patient is fastened to the frame. The mounting means for the frame or top assembly are not shown but it will be understood that the top assembly 11 may be mounted for being shifted lengthwise or longitudinally in opposite directions from the center position in which it is shown and being shifted laterally, that is, toward and away from the observer in FIGS. 1 and 2.

A substantially conventional x-ray tube casing 14 is supported over the table top. Associated with the tube casing is an x-ray beam collimator 15 which defines the boundaries of the x-ray beam that is projectd from tube casing 14 toward the table top 13 such as to penetrate a portion of the anatomy of a patient who is reposed on the table top. There is an x-ray tube, not visible, inside of casing 14. The focal spot of the x-ray tube is marked 16 in FIG. 2 and its position in profile is similarly marked in FIG. 3. X-ray tube casing 14 is mounted on the end of an arm 17 which extends from a column 18. Arm 17 is adjustable vertically on column 18. Normally, for perpendicular radiography, arm 17 and,

hence, focal spot 16 will be adjusted to a fixed distance from table top 13. For angular radiography, the tube casing 16 is rotatable on arm 17 about an axis that passes through focal spot 16 and is perpendicular to the plane of the drawing in FIG. 2. Tube casing 14 and collimator 15 are shown in one of their angulated positions in phantom lines in FIG. 2.

FIG. 3 shows that column 18 is mounted on the back of the table body or base 10 for being moved longitudinally in parallelism with table top 13. Thus, column 18 is supported on a carriage 19 in which there are rollers, not shown, for running on

tracks

20, 21 and another track, not shown. The mechanism for driving column 18 longitudinally is not shown since such mechanisms are known. It is sufficient for the purposes of the present invention to realize that the tube supporting column 18 can be driven or moved longitudinally of the table in opposite directions.

Another general feature of the table exhibited in FIGS. l-3 is the Bucky carriage which is designated generally by the reference number 25 in FIGS. 2 and 3. The Bucky carriage 25 has rollers for running on tracks in the table body so the Bucky may be shifted under table top 13 longitudinally to a limited extent. The details of the Bucky carriage such as the rollers and cooperating tracks are not shown. The Bucky carriage has a tray for supporting a film cassette 26 which is merely symbolized by a dashed line rectangle in FIG. 2. The center of a film in the cassette is designated with a point marked 27 in FIG. 2. When the x-ray tube casing 14 is positioned as it is in FIG. 2 for perpendicular radiography, the focal spot 16 is positioned on a true vertical line which passes through the center point 27 of the film in cassette 26 perpendicularly to the film plane. Point 27 is centered in both directions with respect to the edges of the film and may be considered as coinciding with the top surface of the film.

Immediately below Bucky carriage 25 there is an image intensifier tube 28 for fluoroscopy procedures. The tube has an internal x-ray sensitive photocathode which is symbolized by the curved dashed line 29. Image tube 28 may be a known type characterized by its ability to convert an x-ray image to an optical image. The optical image is directed by an objective lens, not shown, to an angularly disposed mirror 30 which reflects the image to a television camera 31. It will be understood that the television camera 31 is coupled to a television monitor, not shown, which enables the radiologist to view the x-ray image. This procedure is usually referred to as fluoroscopy. A horizontal plane tangent to the center of photocathode 29 may be considered the x-ray image input plane of image tube 28. The photocathode receives the x-ray image and converts it to a light image which is, in turn, converted to an electron image and then to a highly intensified light image again which is received by mirror 30. During fluoroscopy, the x-ray film cassette 26 is removed to avoid exposing it and the x-ray image beam passes through an opening 32 in the bottom of the Bucky carriage. It is evident that when focal spot 16 of the x-ray tube is directly centered perpendicularly over sensitive surface 29 of image intensifier 28 the central ray of the x-ray beam emanating from the focal spot will also pass through the center point 27 of a film when the cassette 26 is inserted. Thus, during vertical fluoroscopy followed by radiography, the image formed on the film will coincide substantially with that formed on the image intensifier sensitive surface 29.

In some x-ray technics, however, the cone of x-rays emanating from focal spot 16 and, particularly, the central ray thereof does not intersect the table top nor the film plane in the cassette perpendicularly. This is the case when angular radiography is being performed at angles up to 45 at which time the x-ray tube is shifted in one direction or the other from the center of the table top and turned at an angle. One angular position of the x-ray tube is illustrated in FIG. 2 where the x-ray tube casing 14 is shifted to the left and rotated about the laterally projected axis of focal spot 16 as indicated by phantom lines in FIG. 2. One may see that with the x-ray tube in phantom line position and angulated, the central x-ray beam marked 33 will intersect table top 13 and a patient reposed thereon at an angle. This technic is used when it is desired to localize an embedded object in the patient and it is also used to obtain a better view of an organ which underlies an interfering organ.

In FIG. 2 it is evident that the central x-ray 33 still passes through center point 27 of a film lying in a horizontal plane within cassette 26. However, it is evident that if central ray 33 is extrapolated it will not coincide with the center of sensitive surface 29 of image intensifier tube 28. In some prior art tables and the present invention as well, the x-ray tube can be, in effect, rotated about a lateral axis extending through point 27 in the film plane so that the central ray always coincides with the center of the film. To accomplish this purpose, the x-ray tube casing 14 is connected to the Bucky carriage 25, which supports the film cassette 26, by a fulcrum bar 34 which pivots about a horizontal axis extending through point 27 and normal to the plane of the drawing in FIG. 2. However, it will be evident that if the height of the fulcrum axis 61 is at point 27 or above, the central ray will pass through the center of the film but not through the center of the x-ray sensitive surface 29 of the image intensifier and the image viewed during fluoroscopy will not agree with that recorded on the subsequently inserted film. It is evident that such would not be the case if image intensifier 28 were shifted far enough to the right in FIG. 2 for central ray 33 to intersect both center point 27 of the film and the center of sensitive surface 29 in the image intensifier 28 within the x-ray table body so, heretofore, during angular radiographic procedures the radiologist had to tolerate an image from the intensifier which was not coincident with the image to be recorded on film in cassette 26. As indicated earlier, the present invention solves this problem by shifting the Bucky carriage and, hence, the film cassette in the same direction in which the x-ray tube is shifted during angular radiography so that the central ray 33 will intersect the center of sensitive surface 29 and the center point 27 of the film cassette at the same time. For this arrangement, the center of the area of the anatomy which'is recorded on the film when the cassette isinserted will agree with that which had been previously observed during fluoroscopy with the image tube.

In accordance with the invention, recording on the film the same view that is observed with the image intensifier is assured by pivoting fulcrum arm 34 and the x-ray tube about a lateral axis that lies on the input plane or sensitive surface 29 of the image intensifier tube. Means are also provided for automatically shifting the Bucky carriage 25 and the film cassette supported thereon in the same direction in which the xray tube is translated longitudinally to thus maintain alignment of the center points of the film and sensitive surface at all times. How this is accomplished will now be discussed.

In FIG. 3 one may see that a fulcrum bar 34, otherwise known as a tomographic bar, couples the x-ray tube cross-arm 17 to a mechanism which is generally designated by the reference numeral 40. A property of this mechanism is that it can be adjusted to cause Bucky carriage 25 to translate beneath the table top in the opposite direction to which the x-ray tube is moved over the table top or it may be adjusted so that the Bucky carriage does not move at all when the x-ray tube is moved and, in accordance with the invention, it may be adjusted so that the Bucky carriage is moved in the same direction as the x-ray tube is moved.

Rotation of fulcrum bar assembly 34 is obtained by driving the x-ray tube casing away from the center of the table for angular radiography. As indicated earlier, in the illustrative embodiment, this is accomplished by driving column 18 in a longitudinal direction on its supporting

tracks

20 and 21 which are symbolized in FIG. 3. As can be seen in FIG. 7, the x-ray tube supporting arm assembly 17 has a carriage 41 with sets of rollers such as 42 and 43 which enable the arm to be positioned at the desired height on column 18. Sometimes during angular radiography, the carriage 41 and arm 17 extending therefrom are locked at a fixed height with respect to table top 13. If the x-ray tube 14 height is fixed by locking the vertical carriage 41, the distance from the focal spot 16 of the x-ray tube to the film plane center point 27 will increase when the x-ray tube is shifted longitudinally along a horizontal line provided there is a slidable connection between the x-ray tube casing 14 and fulcrum bar 34. This situation may be considered to exist in FIG. 2 where it is evident that the length of central ray 33 between focal spot 16 and film center point 27 is greater when the casing is translated and rotated as shown in phantom than it is when the focal spot 16 is perpendicularly aligned with the film center 27 as shown in solid lines when the tube casing is centered with the table. It is customary to lock the tube arm against vertical movement and let the fulcrum bar turning radius and, hence, the focal spot to film distance increase when doing tomography but there is a preference for swinging the x-ray tube through an arc of constant radius for angular radiography to maintain a constant focal spot to film distance.

To maintain the constant distance during angular radiography the tube carriage 41 may be unlocked so it is free to move with a vertical component and thereby follow an arc. The fulcrum bar 34 is clamped to a rotatable shaft 45 on which the x-ray tube is supported to thereby fix the fulcrum bar radius. When the vertical column 18 is shifted from table center, the x-ray tube is angulated on the shaft 45 axis and moved through an arc since the carriage 41 can go up and down as the column 18 moves and the fulcrum bar 34 swings.

In FIG. 7 the x-ray tube is omitted but it will be understood to be mounted on a bracket 44 which is, in turn, fastened to shaft 45. This shaft may be selectively locked against rotation or it may be released for rota tion by a mechanism which is enclosed in the housing of arm 17 and need not be discussed in detail since it is not pertinent to the present invention. For present purposes, rotatability of shaft 45 is assumed. In a broken-away portion of arm housing 17 one may see that shaft 45 is effectively coupled to a yoke 46. Yoke 46 is provided with

recesses

47 and 48 in which fulcrum bar 34 nests. The arrangement is such that fulcrum bar 34 may be permitted to slide vertically within the recesses to compensate for distance changes between focal spot 16 and center point 27 of the film when the x-ray tube casing is translated generally longitudinally. The rear ends of

recesses

48 and 49 are open so that fulcrum bar 34 can be backed out and disengaged from yoke 46 for some radiographic technics. For this reason bar 34 extends through a collar 49 which attaches to an axially movable shaft 50. The collar has a clamping element 51 which enables bar 34 to slide selectively in collar 49.

By means of a mechanism not shown, which is operable by a manual lever 52 on the side of tube arm 17, shaft 50 may be shifted axially to the right as viewed in FIG. 7 so as to effectively disengage fulcrum bar 34 from yoke 46. The fulcrum bar can then slide in the yoke 46 while still turning the yoke and x-ray tube. When engaged as depicted in FIG. 7, the longitudinal shifting of tube arm 17 will rotate fulcrum bar 34 and shaft 50 which will cause x-ray tube supporting shaft 45 to be rotated. Longitudinal movement and rotation of the x-ray tube will assure that central ray is alwaysin parallelism with fulcrum bar 34 but laterally spaced thereof so that the longitudinal axis of the fulcrum bar and of the central ray from the x-ray tube lie in the same laterally extending plane. Thus, the x-ray beam is always directed to the center of the film plane and the angular direction of the fulcrum bar may be considered the angular direction of the central x-ray beam. During angular radiography, fulcrum bar 34 may be engaged with yoke 46 so the yoke cannot slide relative to the bar while the tube angulates and swings through a longitudinal arc and vertical carriage'41 is unlocked so the fulcrum radius and, hence, the focal spot-to-film distance stays constant. During tomography, vertical carriage 41 is locked and bar 34 is unclamped from yoke 46 so the yoke can slide on the bar to allow the bar radius to change when the x-ray tube is moved longitudinally on a horizontal line and not in an arc.

Mechanism 40 for engaging the fulcrum bar 34 with Bucky carriage 25 for driving the latter in selected directions relative to the x-ray tube will now be described. Referring to FIG. 2, one may see that there is a stand or frame 55 fixedly mounted to the table body behind the top 13 thereof. Stand 55 and the mechanism associated therewith is shown in greater detail in FIGS. 4-6. In FIG. 4 there is a motor 56 and a gear train 57 coupling the motor to a lead screw 58. There is an internally threaded cross-head 59 engaged with lead screw 58. Rotation of motor 56 in one direction will elevate head 59 and rotation in the other direction will lower it. The head is also guided on an unthreaded rod 54 and there is a suitable hole in the head through which rod 54 passes. There is a horizontal shaft 60 journaled for rotation in head 59. The axis of shaft 60 is marked 61. At its rear, shaft 60 has a crank arm 62 fastened to it. The back of stand 50 has a vertical slot 63 in it so that head 59, shaft 60 and crank arm 62 may move vertically bidirectionally without interference. Crank arm 62 is provided with an upwardly extending pin 63 which facilitates coupling it to the end of fulcrum bar 34. The details of the socket in the end of fulcrum bar 34 for engaging pin 63 are not shown. In any event, crank arm 62 always remains in alignment with fulcrum bar 34 and the x-ray beam is in the direction of the fulcrum bar. Shaft 60 and its axis 61 can be adjusted in height by moving head 59 so the axis 61 extends laterally atvarious elevations such as through selective planes about table top 13, through the film plane or, in accordance with the invention, through planes below the film plane including the image intensifier input surface plane 29 which is shown in dotted lines in FIG. 4.

FIG. shows another arm 64 which is pinned to shaft 60 for joint rotation with crank arm 62. Arm 64 is fastened to a distance compensating linkage including a link 65 and another link 66 which is slidable relative to link 65. These links may be considered extensions of the fulcrum bar beyond its rotational axis 61. Link 66 has a pad or base element 67 fastened to it and an arm 68 which extends downwardly is fastened to a shaft 69 by means of a pin 70. Shaft 69 is journaled in bearings 71 which are recessed in base element 67 as can be seen clearly in FIG. 6. In FIG. 6 it is evident that link 65 is provided with a pair of

channels

72 and 73. The other link 66 has a complementary pair of

channels

74 and 75 which are so shaped that they retain a plurality of bearing balls such as 76 and 77 between them. This sliding link assembly is known in the art and need not be discussed in greater detail except to create awareness that link 66 is slidable on link 65 and the links are inseparable and maintain their alignment at all times.

In FIG. 3, it is evident that downwardly extending arm 68 and, particularly, the T-shaped head 78 thereof is fastened to a cross-bracket 79 which has an upwardly extending portion 80 connected rigidly to Bucky carriage 25. The axis of arm 68 supporting shaft 69 extends laterally across the table top and projects through the film plane or the plane in which film center point 27 is lying during the radiographic procedure. In FIG. 4, the film plane is indicated with a broken line marked 27. The plane of the top surface of the table top is indicated with a broken line marked 13. Since Bucky carriage 25 is constrained to move in one plane only, axis 69 of arm 68 will always extend through the corresponding film plane even though the arm extends below it and then upwardly again where its end portion 80 fastens to Bucky carriage 25.

Since arm 68 remains fixed in elevation even though fulcrum bar 64 turns

links

65 and 66 jointly about the axis 61 of shaft in the cross-head 59, the radius between cross-head axis 61 and axis 69 of arm 68 varies for distance compensation because of link being slidable on link 66.

In FIG. 4, the x-ray tube casing would be to the left of the center of the table viewing it from the front and the central ray would be at the same angle as

link

65 and 66. With cross-head 59 adjusted to the high level in which it is shown in FIG. 4, the cross-head shaft axis 61 would extend through a plane above x-ray table top 13 such as might be the case if the apparatus were being used for conducting tomography. In such case, if the x-ray tube were shifted to the right or clockwise as viewed in FIG. 4, the

links

65 and 66 would swing in the opposite direction to drive the Bucky carriage oppositely from the direction in which the tube is moved. This procedure results in all planes of the table top supported subject being radiographed which planes are above and below cross-head shaft axis 61 to be blurred on the film while the plane in which shaft axis 61 lies remains in focus and is sharply imaged on the film.

If cross-head 59 is shifted downwardly until fulcrum bar rotational axis 61 lies on film plane 27, the x-ray tube, in effect, is rotatable about the film plane and the Bucky carriage is not shifted longitudinally when the x-ray tube is shifted longitudinally. Some prior art tables permit the fulcrum axis 61 to be lowered to the level of film plane 27. This facilitated directing the central ray at the center of the film at all times during angular radiography for any position of the x-ray tube.

In accordance with the invention, cross-head 59 may be lowered on lead screw 58 until the fulcrum bar pivot shaft axis 61 lies on the input surface of the image intensifier tube which surface is defined by a curved dotted line marked 29. It is evident that cross-head shaft or fulcrum bar axis 61, with this adjustment, is well below the film plane 27'. Now, if the long radius defined by fulcrum bar 34 with respect to rotational axis 61 is rotated in one direction as viewed in FIG. 4, pivot axis 69 and Bucky carriage 25 engaged thereto will shift in the same direction along the film plane 27. This is so because the fulcrum axis 61 is now below the film plane 27 and coincident axis 69. Since the central x-ray passes through axis 69 which is on the film plane and fulcrum axis 61 is on the plane 29 of the sensitive surface of the image intensifier, the central x-ray beam will pass through the center of the film and the center of the sensitive surface simultaneously. As long as fulcrum axis 61 is on the plane of sensitive surface 29 of the image intensifier, this alignment will be maintained and whatever image is viewed centrally on the image intensifier tube will be recorded centrally on the film in the cassette.

The situtation which exists when cross-head 59 is adjusted vertically so that fulcrum bar axis 61 coincides with sensitive surface 29 is shown schematically in FIG. 8 where it will be seen that the film center point 26 lying on the film plane is slightly to the left of the center image tube input surface center point 61 so that central ray 33 passes through both center points. The plane of an object such as 81 in FIG. 8 will thus be imaged correspondingly on the film and the input surface 29 of image intensifier tube 28. When the x-ray tube focal spot 16 is moved longitudinally through an arc for taking a fluoroscopic view and a radiograph at a different angle such as at the angle of central beam 33' in FIG. 8, the central ray 33 will still pass through the center point 26" of the film because the Bucky 25 has been shifted to its phantom line position. Thus, central ray 33 and the cone of rays surrounding it effectively rotate about laterally projected fulcrum bar axis 61 so the image viewed on surface 29 is the same as that on the film for all angular fluoroscopic and radiographic views. FIG. 9 shows diagramatically how link 65 has shifted along link 66 when the axis of the cross-head is adjusted to coincidence with sensitive surface 29. It is also evident in FIG. 9 that when the x-ray tube 14 and its focal spot 16 are shifted to the right, rotation will occur about axis 61 and Bucky carriage 25 will move to the right slightly to maintain the

points

26 and 61 on the line of sight of the central x-ray 33. Of course, if tube 14 is shifted further to the left in FIG. 9, Bucky carriage 25 will shift further to the left a short distance and the alignment of the x-ray beam 33 and the centers of the film and intensifier will still be maintained.

The fulcrum bar 34 may be selectively removed or installed for various procedures. When the bar 34 is installed it couples tube rotation yoke 46 to the fulcrum mechanism crank arm 62. For performing perpendicular radiography the fulcrum bar may be installed and the x-ray tube locked against angulation so as to maintain perpendicularity from the x-ray tube focal spot and the film plane for all positions of the tube stand. The bar may be removed for perpendicular radiography if, as in some tables, other means are provided for maintaining perpendicularity.

In some prior table designs it is possible to remove the fulcrum bar and manually angulate the x-ray tube for angular radiography and to shift the Bucky carriage and cassette thereon in the same direction in which the x-ray tube is shifted to provide coincident alignment of the film center and the center of a image intensifier input plane. However, in accordance with the present invention this is done accurately, rapidly and essentially automatically by having the installed fulcrum bar provide this coincidence.

The fulcrum bar in the illustrated x-ray table may also be removed for the vertical radiography procedure where the cassette is supported in a vertical plane on a floor mounted stand, not shown. In this procedure, tube arm 17 is swung with column 18 so the arm extends lengthwise of the table and the tube is rotated so its central x-ray beam projects laterally across the table top toward the vertical cassette stand.

To summarize operation of the equipment for angular radiography and body localization, column 18 is moved until the x-ray tube is pointed at the angle which the radiologist deems necessary for radiographing an underlying organ or embedded object in the patient. The x-ray tube is automatically turned at an angle which will maintain the central x-ray beam on the center of the film cassette. At this time, the cross-head or fulcrum axis will be lowered coincident with the input surface of the image intensifier tube and the Bucky carriage and film cassette thereon will be shifted in the same direction in which the x-ray tube is moved longitudinally from the center line of the x-ray table. The radiologist then energizes the x-ray tube for the fluoroscopic mode and views the image produced by the image intensifier on a television monitor. When the desired angular view and area of the anatomy is obtained, the x-ray tube is turned off and a film cassette is inserted in the Bucky carriage. The x-ray tube, current, voltage and exposure time factors are then set for the radiographic mode and a radiograph is quickly taken. Then, if the radiologist desires a view at another angle, tube column 18 is driven longitudinally of the table top and the x-ray tube is moved through an arc and is angled correspondingly and automatically. The rotational axis 61 for fulcrum bar 34 will again be coincident with the input surface of the image intensifier if sequential fluoroscopy and radiography are desired. If the tube is moved from the angle which is shown in phantom in FIG. 2 beyond center to the opposite angle from perpendicular, the Bucky carriage and film cassette thereon will move in the same direction to maintain the alignment of the focal spot, the center of the film plane and the center of the image intensifier tube. In apparatus in which there is no image intensifier tube, the cross-head axis 61 may merely be adjusted downwardly to the level of the film plane so that the x-ray tube rotates about an axis lying in the film plane for in such case it would not make any difference if the image lying in a plane below the film plane were displaced or cut off.

To operate in the perpendicular radiographic mode, the x-ray tube is oriented with the focal spot directly over the center of the film in the cassette and the patient is aligned with the beam to get the desired view by shifting the table top 13 laterally and longitudinally.

The tomographic mode of operation is somewhat similar to the angular radiography mode except that the axis of the fulcrum bar, as is known, will extend through the plane of interest of a patient lying on table top 13. The central ray from the x-ray tube will penetrate the center of the film. However, as the x-ray tube is shifted longitudinally of the table top in one direction, the film cassette on the Bucky carriage will be moved in the opposite direction from the x-ray tube since the tube is on the opposite side of the pivot from the Bucky carriage. For tomography, the x-ray tube may be moved horizontally and angulated in which case the distance between the focal spot and the film plane will vary. This requires that the tube arm be locked against vertical motion on its supporting column and that the tube casing slide axially relative to the fulcrum bar 34.

In the illustrative embodiment, the x-ray tube casing is mounted on a column which translates longitudinally of the table body. It will be understood that the x-ray tube might also be mounted on an overhead tube hanger similar to a traveling crane independently of the x-ray table. Moreover, the illustrative table is one which is not adapted for tilting but those skilled in the art will appreciate that the invention may be used in conjunction with tiltable tables as well in which case the tube supporting column 18 would not only translate longitudinally of the table top but would tilt with the body as well. All of the angular relationships between the parts of the apparatus discussed above in connection with the table top being maintained horizontal would exist if the table top and patient thereon were tilted at an angle with respect to horizontal.

Although a preferred embodiment of the invention has been described in considerable detail, such description is intended to be illustrative rather than limiting for the invention may be variously embodied and is to be limited only by interpretation of the claims which follow.

We claim:

1. In diagnostic x-ray apparatus having x-ray tube means movable over an x-ray table which comprises a table body means and an x-ray permeable top mounted thereon for supporting an examination subject, means for supporting a radiographic film for movement relative to said top in a plane on one side thereof opposite from'the x-ray tube, a fixed fluoroscopic means having an x-ray sensitive surface more remote from said top than said film plane, the improvement for automatically obtaining substantially the image of an area of an examination subject on the film as is viewed with the fluoroscopic device, comprising:

a. means movable along a line substantially normal to said film plane,

b. fulcrum arm means having a first pivot connection to said movable means, said fulcrum arm means being coupled on one side of said first pivot connection to said x-ray tube means and being engaged by a second pivotal connection with said film supporting means, the axes of said first and second pivotal connections being directed laterally of said table top and the second pivotal axis lying substantially in said film plane, the x-ray beam from said tube being directed in the direction of said fulcrum arm means through said pivotal axes, and

c. means for adjusting said movable means through a range of positions for said first pivotal axis to be at selected levels on the x-ray tube side of said film plane, coincident with said film plane and coincident with said x-ray sensitive surface of said fluoro scopic device whereby said film supporting means will move in the opposite direction of fulcrum arm rotation when said first pivot axis is on the x-ray tube side of said film plane and will move in the same direction when said first axis is on said sensitive surface of said fluoroscopic device so that the central ray of said x-ray beam will pass through said first axis on said film and said second axis on said surface whereby the central ray of the x-ray tube will be simultaneously coincident with the center of the film and the center of said sensitive surface and substantially the same x-ray image area may be recorded on said film as occurs on said sensitive surface.

2. The invention defined in claim 1 wherein:

a. said fulcrum arm means between said first and second pivot axes comprises at least a pair of elements which are joined for relative sliding motion whereby to compensate for radius changes between said axes when said fulcrum arm means is rotated.

3. The invention defined in claim 1 including:

a. lead screw means having a rotation axis coincident with the line of movement of said movable means,

b. said movable means having a thread engaging it with said lead screw means, rotation of said lead screw means changing the position of said movable means on the axis of said screw means, and

c. a reversible motor and means coupling said motor means in driving relation to said lead screw means.

4. In diagnostic x-ray apparatus adapted for perpendicular radiographic, tomographic and angular radiographic examination of a subject and for fluoroscopic examination thereof, said apparatus cooperating with a movable x-ray tube means, said apparatus including an x-ray table comprising a table body and an x-ray permeable top panel mounted thereon for supporting an examination subject, a carriage for supporting a radiographic film cassette, for movement of a film therein in a plane on one side of the table top opposite from the x-ray tube, a fluoroscope device fixedly mounted in said table body and having an x-ray image insert surface more remote from said top than said film plane, the improvement for assuring that the central ray from said x-ray tube and the center of the image on said fluoroscope device will be coincident with the center of the image on the film, said improvement comprising:

a. movable means and means for guiding said movable means in a line of travel substantially perpendicular to said film plane and said x-ray image insert surface,

b. fulcrum arm means connected for angular movement on said movable means about an axis projecting in the lateral direction of said table top,

0. said fulcrum arm means having a portion on one side of said axis coupled to said x-ray tube means and another portion on the other side of said axis connected to said film support means,

d. said movable means being selectively adjustable along its line of travel to locate said fulcrum arm axis in selected planes a predetermined distance from said table top, whereupon movement of said x-ray tube means in one direction will move film support in an opposite direction,

e. said movable means being further adjustable along its line of travel to locate said fulcrum arm axis on said image insert surface whereby to dispose said axis on an opposite side of said film plane whereby rotation of said fulcrum arm due to movement of said x-ray tube will cause said film support to move in the same direction as said x-ray tube whereby to maintain the central ray from said x-ray tube on the center of a film on said support and coincidentally on the center of said insert plane, the image area recordable on said film thereby being the same as that viewed with said fluoroscopic device, and

f. means supporting said x-ray tube for rotation by said fulcrum arm means coordinately with said x-ray tube movement to maintain alignment of said x-ray tube beam with said fulcrum arm.

Claims

1. In diagnostic x-ray apparatus having x-ray tube means movable over an x-ray table which comprises a table body means and an xray permeable top mounted thereon for supporting an examination subject, means for supporting a radiographic film for movement relative to said top in a plane on one side thereof opposite from the x-ray tube, a fixed fluoroscopic means having an x-ray sensitive surface more remote from said top than said film plane, the improvement for automatically obtaining substantially the image of an area of an examination subject on the film as is viewed with the fluoroscopic device, comprising: a. means movable along a line substantially normal to said film plane, b. fulcrum arm means having a first pivot connection to said movable means, said fulcrum arm means being coupled on one side of said first pivot connection to said x-ray tube means and being engaged by a second pivotal connection with said film supporting means, the axes of said first and second pivotal connections being directed laterally of said table top and the second pivotal axis lying substantially in said film plane, the x-ray beam from said tube being directed in the direction of said fulcrum arm means through said pivotal axes, and c. means for adjusting said movable means through a range of positions for said first pivotal axis to be at selected levels on the x-ray tube side of said film plane, coincident with said film plane and coincident with said x-ray sensitive surface of said fluoroscopic device whereby said film supporting means will move in the opposite direction of fulcrum arm rotation when said first pivot axis is on the x-ray tube side of said film plane and will move in the same direction when said first axis is on said sensitive surface of said fluoroscopic device so that the central ray of said x-ray beam will pass through said first axis on said film and said second axis on said surface whereby the central ray of the x-ray tube will be simultaneously coincident with the center of the film and the center of said sensitive surface and substantially the same xray image area may be recorded on said film as occurs on said sensitive surface.

2. The invention defined in claim 1 wherein: a. said fulcrum arm means between said first and second pivot axes comprises at least a pair of elements which are joined for relative sliding motIon whereby to compensate for radius changes between said axes when said fulcrum arm means is rotated.

3. The invention defined in claim 1 including: a. lead screw means having a rotation axis coincident with the line of movement of said movable means, b. said movable means having a thread engaging it with said lead screw means, rotation of said lead screw means changing the position of said movable means on the axis of said screw means, and c. a reversible motor and means coupling said motor means in driving relation to said lead screw means.

4. In diagnostic x-ray apparatus adapted for perpendicular radiographic, tomographic and angular radiographic examination of a subject and for fluoroscopic examination thereof, said apparatus cooperating with a movable x-ray tube means, said apparatus including an x-ray table comprising a table body and an x-ray permeable top panel mounted thereon for supporting an examination subject, a carriage for supporting a radiographic film cassette for movement of a film therein in a plane on one side of the table top opposite from the x-ray tube, a fluoroscope device fixedly mounted in said table body and having an x-ray image insert surface more remote from said top than said film plane, the improvement for assuring that the central ray from said x-ray tube and the center of the image on said fluoroscope device will be coincident with the center of the image on the film, said improvement comprising: a. movable means and means for guiding said movable means in a line of travel substantially perpendicular to said film plane and said x-ray image insert surface, b. fulcrum arm means connected for angular movement on said movable means about an axis projecting in the lateral direction of said table top, c. said fulcrum arm means having a portion on one side of said axis coupled to said x-ray tube means and another portion on the other side of said axis connected to said film support means, d. said movable means being selectively adjustable along its line of travel to locate said fulcrum arm axis in selected planes a predetermined distance from said table top, whereupon movement of said x-ray tube means in one direction will move film support in an opposite direction, e. said movable means being further adjustable along its line of travel to locate said fulcrum arm axis on said image insert surface whereby to dispose said axis on an opposite side of said film plane whereby rotation of said fulcrum arm due to movement of said x-ray tube will cause said film support to move in the same direction as said x-ray tube whereby to maintain the central ray from said x-ray tube on the center of a film on said support and coincidentally on the center of said insert plane, the image area recordable on said film thereby being the same as that viewed with said fluoroscopic device, and f. means supporting said x-ray tube for rotation by said fulcrum arm means coordinately with said x-ray tube movement to maintain alignment of said x-ray tube beam with said fulcrum arm.