U.S. patent number 3,770,955 [Application Number 05/180,260] was granted by the patent office on 1973-11-06 for tomographic apparatus.
This patent grant is currently assigned to Hitachi Roentgen Company, Limited. Invention is credited to Kazuo Kobayashi, Yuji Miyazaki, Mitsuo Okudaira, Chuji Tomita.
United States Patent |
3,770,955 |
Tomita , et al. |
November 6, 1973 |
TOMOGRAPHIC APPARATUS
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.
Inventors: |
Tomita; Chuji (Adachi-ku,
Tokyo, JA), Miyazaki; Yuji (Matsudo-shi, Chiba,
JA), Kobayashi; Kazuo (Kashiwa-shi, Chiba,
JA), Okudaira; Mitsuo (Kita-ku, Tokyo,
JA) |
Assignee: |
Hitachi Roentgen Company,
Limited (Tokyo, JA)
|
Family
ID: |
13732456 |
Appl.
No.: |
05/180,260 |
Filed: |
September 14, 1971 |
Foreign Application Priority Data
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|
|
|
Sep 17, 1970 [JA] |
|
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45/80940 |
|
Current U.S.
Class: |
378/27; 378/197;
378/181 |
Current CPC
Class: |
A61B
6/025 (20130101); A61B 6/447 (20130101) |
Current International
Class: |
A61B
6/02 (20060101); A61B 6/00 (20060101); H01j
037/20 () |
Field of
Search: |
;250/61.5,52 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Lawrence; James W.
Assistant Examiner: Anderson; B. C.
Claims
We claim:
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.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is concerned with an apparatus for performing
tomography, which is suitable for obtaining satisfactory tomograms
of various required regions of the body or an animal body.
2. Description of the Prior Art
Various types of tomographic apparatuses are being used to obtain
X-ray tomograms of a variety of regions of the human body for
diagnostic as well as therapeutic purposes.
An X-ray tomography is intended, in principle, to obtain a sharply
focused tomogram of a desired particular region of the body of a
patient on a film which is adapted to move in associated positional
relationship with the X-ray source while an X-ray beam is directed
onto the required region of the body of the patient in a certain
optimum direction selected from a variety of directions, in such a
way that the X-rayed image of those un-required regions of the body
other than that particular region required for tomographic purposes
is satisfactorily blurred so as to be blanked out.
According to the knowledge obtained in the past with respect to the
technology in this field, it is commonly known that the amount of
blurring of the X-rayed image of the said unnecessary regions of
the object will increase with an increase in the length of the path
of travel of the X-rays from the source and that such a blurred
image of the unnecessary regions -- which are obtained in elongated
patterns -- such as the images of bones which are located in
parallel with the path of movement of the X-ray source, is
difficult to blank out since these unnecessary images appear on the
film in superposed relationship on top of the image of the required
particular region. Therefore, in order to obtain a satisfactory
tomogram of a particular region of body, such as in the chest, head
or hip, where the arrangement of bones is complicated, it is
necessary to use such an X-ray apparatus so arranged that the X-ray
source travels in a path having the best angle for each region of
body which is to be X-rayed.
For the foregoing reason, there have been developed and placed on
the market tomographic apparatuses which are designed so that the
X-ray source not only is able to make a rectilinear movement but
also is able to move on a path which represents a curve of the
second degree such as circular, oval or hypocycloidal. Also, in
order to blank out the elongated images of those unnecessary
regions of the object which lie outside the tomographic plane,
there has been sucessfully devised a technique which is called
selective X-ray irradiation such that an irradiation of X-ray beam
is produced only within a specific section of the range of path of
movement of the X-ray tube.
However, in those known tomographic apparatuses which have been put
into practice already, the paths to be followed by the X-ray source
are limited to very small group of directions. From the standpoint
of being ideal, these known tomographic apparatuses and techniques
have not yet attained satisfactory technical levels in view of the
consideration that there exists an optimum path of movement --
which is different from other paths -- of the X-ray source for each
region of the body to be X-rayed. In addition, these known
tomographic apparatuses are too complicated to be operated easily.
With these known apparatuses, there is required -- in case an
alteration of the path of movement of the X-ray source is needed in
accordance with the location or the angle of the required region of
the object to be X-rayed -- complicated and time-consuming setting
operations for each tomography and also a highly trained technician
is required. The aforesaid selective X-ray irradiation method
requires, in addition to the mechanism for driving the X-ray
source, the provision of a particular mechanism for controlling the
X-ray irradiation -- depending on the position of the X-ray source
currently located on its path of movement -- for each region of the
object to be X-rayed. Thus, this prior method gives rise to a
further complexity in both the apparatus structure and the handling
and these factors have made the practicability of this method very
small.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide an
improved apparatus for obtaining quality tomograms, which permits
the X-ray source to travel on any arbitrary path within the range
in which it is allowed to move, without being impaired by any
structural restrictions such as those stated above, and which
produces a tomogram wherein the X-ray image of those unnecessary
regions of the object is satisfactorily blurred.
Another object of the present invention is to provide an improved
tomographic apparatus which allows the path to travel of the X-ray
source to be selected as desired, only by the manipulation of a
selective switch provided on the control panel of the apparatus,
and which accordingly is easy to handle.
Still another object of the present invention is to provide an
improved tomographic apparatus which enables the setting of the
velocity of travel of the X-ray source to be made during any
portion of the path of movement of the X-ray source already set as
desired, and which is capable of effecting substantial control of
the amount of irradiation of the X-ray beam by locally altering the
said velocity during the travel of the X-ray source, and which,
thus, is able to more satisfactorily blur the X-ray image of the
unnecessary regions of the object to be X-rayed.
These and other objects as well as the advantages and features of
the present invention will become apparent by reading the detailed
description of the preferred embodiment when taken in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a somewhat diagrammatic front elevation, showing the
essential parts of a preferred example of the apparatus of the
present invention, in which the link means is tilted only in the
direction of axis Y.
FIG. 2 is a somewhat diagrammatic side elevation of the same
apparatus, in which the link means is tilted only in the direction
of axis X, showing also the positional relationship between the
object to be photographed and the apparatus.
FIG. 3 is a somewhat diagrammatic fragmentary perspective view,
showing a part of the means for setting the travel path of the
X-ray source and a part of the means for adjusting the outputs of
the driving motors.
FIGS. 4 to 6 are somewhat diagrammatic illustrations to explain the
said setting means and the said adjusting means shown in FIG. 3; in
which:
FIG. 4 is a plan view,
FIG. 5 is a fragmentary plan view, showing the means of FIG. 4 in a
different position, and
FIG. 6 is a side view, showing the structure of the cam means which
represents the said setting means.
FIG. 7 is a somewhat diagrammatic explanatory illustration,
representing a plan view of the cam-selecting mechanism of a set of
cams provided in the means for setting the travel path of the X-ray
source.
FIG. 8 is a somewhat diagrammatic explanatory plan view of the
control mechanism for setting the stopping position of a required
set of cams which are provided in the means for setting the travel
path of the X-ray source.
FIGS. 9A, 9B, and 10A, 10B are explanatory illustrations, showing
the relationship between the path of movement of the X-ray source
and the shape of the cam faces; in which:
FIGS. 9A and 9B show the relationship between the two when the
X-ray source makes a rectilinear movement, and
FIGS. 10A and 10B show the relationship between the two when the
X-ray source makes a circular movement.
FIG. 11 is a longitudinal sectional view of a servo valve means
employed in the present invention as the means for adjusting the
outputs of servo motors, showing the structural details
thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIGS. 1 and 2, there is shown an example of the tomographic
apparatus embodying the present invention. In the drawings, it will
be noted that, on a base frame 1, there is supported a shaft 2 in
bearings 3 and 4 in such a way that this shaft 2 is rotatable about
its own axis in the direction Y which is shown by an arrow. Two
main link arms 5 and 6 of a link means are supported on pins 7 and
8, respectively, on the ends of shaft 2, so that these link arms 5
and 6 are rotatable in a direction perpendicular to the direction
of rotation of the said shaft 2, or in other words, these main link
arms 5 and 6 are rotatable in the direction of axis X. The
directions of rotation of the shaft 2 and the link means are
expressed as the directions of axis Y and axis X hereinafter as
well as in the claims. Two bridge arms 9 and 10 are rotatably
coupled to the said main link arms 5 and 6, respectively. These
four arms 9, 10, 5 and 6 constitute a parallelogram linkage which
can make swinging motion about the pins 7 and 8 on the shaft 2, in
directions crossing at right angles or in other words in the
directions of axes Y and X. Auxiliary arms 11 and 12 are
operatively coupled to the ends of the extension 5' of the main
link arm 5 and the extension 10' of the bridge arm 10,
respectively, to form another parallelogram linkage in this portion
of the link means. The aforesaid arrangement provides a link means
which may be defined as a pantographically arranged linking
mechanism which, as a whole, can be rotated in the directions of
axis Y and axis X.
An X-ray tube 13 which serves as the X-ray source is secured to the
auxiliary arm 12. On the other hand, a film holder 14 is secured to
the foremost end of the extension of the bridge arm 9. The X-ray
source 13, the center of the film mounted on the film holder 14 and
a point A located on the extension of the longitudinal axis of the
shaft 2 are arranged so that these three points will always lie on
a rectilinear line irrespective of whatever angle of inclination is
assumed by the link means as it is tilted in the directions of axis
Y and axis X.
The bridge arm 9 which supports the film holder 14 is supported by
bearings 58 and 59 which, in turn, are rotatably mounted on the
link arms 5 and 6, respectively. Reference numeral 15 represents a
balance load for balancing the forces existing on both sides of the
shaft 2. An arm 17' is fixed to the said bridge arm 9. This arm 17'
is coupled, at a position closer to one end thereof by a ball
joint, to an auxiliary arm 17 which is provided between the link
arms 5 and 6. This arm 17' is arranged to be parallel with the said
link arms 5 and 6. The opposite and portion of the auxiliary arm 17
is coupled via a ball joint to another auxiliary arm 16 which is
fixed to the base frame 1. Because of this arrangement, it will be
understood that when the link arms 5 and 6 are rotated in the
direction of axis X about the pins 7 and 8, the film holder 14 will
carry out a movement, in parallel with and in correlation with the
X-ray tube 13, in such a way that the center of the film mounted on
the film holder 14, the focus of the X-ray source 13 and the point
A on the extension of the longitudinal axis of the shaft 2 lie on a
straight line. When the link arms 5 and 6 are rotated in the
direction of axis Y about the shaft 2, on the other hand, the
auxiliary arm 17 tilts about its pivotal point on the auxiliary arm
16 through an angle which is the same as that of the tilting of the
link arms 5 and 6, so that the arm 17' rotates the bridge arm 9 to
maintain the film holder 14 horizontal in position in spite of the
tilting of the link arms 5 and 6. At the same time therewith, the
center of the film mounted on the film holder 14 keeps the
aforesaid correlationship with the X-ray tube 13 and the point
A.
As will be described later, the point A represents a point lying on
the tomographic plane of the object to be photographed by X-rays.
Thus, it may be said that both the X-ray tube 13 and the film
mounted on the film holder 14 are adapted to make spherical
movements, respectively, about a point lying on the tomographic
plane.
With the linking mechanism having the aforesaid arrangement, let us
now assume that a force is applied to the main link arm 5 in any
arbitrary direction. Whereupon, the link arm 5 tilts in the
direction in which the force is applied. Thus, the main link arm 5
is able to assume any arbitrary angle of inclination within the
range of the maximum angle of inclination which is limited by the
linking mechanism as a whole and also by the base frame 1.
Accordingly, the X-ray tube 13 and the film holder 14 are able to
travel on any desired paths of movement, starting at any arbitrary
positions on the faces of spheres formed about the point A,
respectively. At the same time, the line which is formed by
connecting the X-ray source 13, the point A located on the
extension of the central longitudinal axis of the shaft 2 and the
center of the film holder 14 will be a straight line in all
cases.
The servo motors which impart to the linking mechanism having the
aforesaid arrangement the required angles of inclination in both
directions of Y and X, in this embodiment, are comprised of two
hydraulically operated cylinders 18 and 19. Cylinder 18 of these
two hydraulic cylinders is arranged between the shaft 2 and the
main link arm 5. The other hydraulic cylinder 19 is arranged
between the base frame 1 and the main link arm 5. The action of the
hydraulic cylinder 18 causes both the X-ray source 13 and the film
holder 14 to move in the direction of the axis X, whereas the
action of the hydraulic cylinder 19 causes both the X-ray source 13
and the film holder 14 to move in the direction of the axis Y.
These two hydraulically driven cylinders 18 and 19 are controlled
in their actions by follow up linkage means for adjusting the
action of the servo motors which will be described later. In FIGS.
3 to 5, it will be seen that the main link arm 5 has, operatively
coupled thereto at an arbitrary point B located within the length
of this arm, a first corner joint of the bridges of a square follow
up linkage which is formed by four links or bridge arms 20, 21, 22
and 23. Another joint of this latter linkage, which is located at a
diagonally opposite corner of the square bridges relative to the
aforesaid first corner joint is pivotably supported at a fixed
point C on the base frame 1 in such a way that, when the main link
arm 5 is located at a certain reference position in the directions
of both the axis X and the axis Y, the said two bridge arms 20 and
23 of the aforesaid square linkage are positioned in parallel
relationship with the direction of the axis X, and the other two
bridge arms 21 and 22 are positioned in parallel with the direction
of the axis Y. The bridge arms 22 and 23 have, on the sides closer
to the fixed point C, joints 24 and 25, respectively, to
substantially divide each of these two bridge arms into two arm
segments. An arm segment 22' which is located between the joint 24
and the fixed point C is provided with a hydraulic servo valve
means 26 and an arm segment 23' which is located between the joint
25 and the fixed point C is provided with another hydraulic servo
valve means 27, both of which servo valve means 26 and 27 are for
controlling the actions of the aforesaid hydraulic cylinders 18 and
19. These two servo valve means each has an actuator rod, and these
two rods are in contact with the said arm segments 22' and 23' via
levers 57' and 57, respectively, to actuate the said hydraulic
cylinders 18 and 19, respectively.
These two servo valve means are each coupled to the two hydraulic
cylinders by two oil pipes. To each servo valve means is coupled a
pressurized oil supply pipe extending from a pressurized oil source
not shown and also coupled thereto is an oil discharge pipe
extending from a hydraulic cylinder. FIG. 11 shows a preferred
example of such a servo valve means. These two servo valve means
serve to control both the supply and discharge of a pressurized oil
to and from the hydraulic cylinders 18 and 19, respectively, in
association with the motion of the link arm segments 22' and 23',
respectively. A spool 54 of each servo valve means is urged against
the arm segments 22' or 23' by a spring 56 so that the spool 54
opens and closes the respective orifices of the valve means in
accordance with the movement of these arm portions, to thereby
control the supply and discharge of the pressurized oil to and from
the hydraulic cylinders 18 or 19. It should be understood that the
hydraulic circuitry as a whole including the two hydraulic
cylinders 18 and 19 and the servo valve means 26 and 27 is known,
and accordingly, the description of its details is omitted.
Means for setting the paths of travel of both the X-ray source 13
and the film holder 14 is shown in FIGS. 3 to 7. The said means for
setting the travel paths is comprised of cam means which is
generally indicated at 28. This cam means 28 comprises a plurality
of sets of cams, each set being comprised of two cams having
different cam face configurations, one 28x of each set being for
controlling the movement of the said two members in the direction
of the axis X, and the other cam 28y being for controlling their
movements in the direction of the axis Y. These two cams 28x and
28y are rotatably mounted on a shaft 29. This cam means 28 -- in
cooperation with the cam-selecting mechanism which will be
described later and which is for selectively driving a required set
of cams -- constitutes means for setting the travel paths of the
said two members. Of these two cams forming one set, the cam 28y
which controls the movement of the said two members in the
direction of the axis Y is contacted by a roller 32 which, in turn,
is rotatably supported on a shaft 31 on a frame which constitutes
the arm segment 23'. On the other hand, the other cam 28x of the
cams of a set is contacted by a roller 33 which, in turn, is
rotatably supported on the arm segment 22'. With the aforesaid
arrangement of the cam means, it will be understood that the
rollers 32 and 33 are able to be displaced in accordance with the
rotation of their corresponding cams, causing the rotation of the
arm segments 22' and 23' so that the servo valve means 26 and 27
are actuated.
The details of the aforesaid cam selecting mechanism are shown in
FIG. 7. Each set of two cams 28x and 28y is rotatably mounted on a
boss 34 which, in turn, is fixed to the shaft 29. The arrangement
is such that only the selected set of cams is directly coupled to
the shaft 29 by a clutch mechanism which is provided for each set
of cams, in such a way that these two cams 28x and 28y are adapted
to be rotated simultaneously. More specifically, the aforesaid boss
34 is provided with an engaging groove 35 formed on the
circumference thereof.
One cam 28y of the two cams is provided with a pawl member 37 which
is pivotably attached thereto by a pin 36. This pawl member 37 is
arranged on the cam so that it is engageable in the engaging groove
35 of the boss 34. This pawl member 37 normally is urged by a
spring 38 to engage the said groove 35. In the rigid, fixed region
close to each set of cams, there is provided a lever 40 which is
rotatably supported on the said fixed region and which has an
engaging end portion 41 adapted to engage the end portion of the
pawl member 37 to act in such a fashion as to release the pawl
member 37 from its engagement with the groove 35 against the force
of the spring 38. The said lever 40 is rotated by a solenoid 42 and
is adapted to be brought back to its normal position by a coil
spring 43. Accordingly, when the solenoid 42 is energized, the pawl
member 37 is relieved of its engagement with the end portion of the
lever 40, and the pawl of the pawl member 37 is brought into
engagement with the groove 35. As a result, the rotation of the
shaft 29 is transmitted to the set of cams via the boss 34 and the
pawl member 37, and thus, the said set of cams is rotated. Such a
cam-selecting mechanism is provided for each set of cams as stated
previously. By manipulating a selective switch not shown which is
provided on the control panel not shown, a particular solenoid 42
is energized to control the required set of cams and to thereby
actuate the hydraulic servo valve means.
A mechanism for controlling the velocity of revolution of the cams
is provided on the shaft 29 which is intended to drive the cam
means 28. As seen best in FIG. 8, the shaft 29 is rotatably
supported on the base frame 1 and is rotated by a motor 45 (seen in
FIG. 3). A cam 44 is fixed to the bottom of the shaft 29 and it is
provided, on the periphery thereof, with two grooves 46 and 47. On
the rigid fixed portion of the apparatus located close to this cam
44, or in other words on the base frame 1, there is arranged a
lever 49 which, in turn, is rotatably supported on a pin 48. This
lever 49 has a pawl 51 and is urged against the periphery of the
cam 44 by a coil spring 50. In the normal state of the lever 49,
the pawl 51 engages the groove 46 of the cam 44. A limit switch 52
which is controlled by the said lever 49 is provided to control the
action of the motor 45 in the following manner. During the period
in which the pawl 51 engages either one of the grooves 46 and 47,
the said limit switch 52 is adapted to shut off the supply of
current to the motor 45, and during the period in which the
solenoid 53 is actuated or in other words during the period in
which the pawl 51 engages neither one of the grooves 46 and 47, the
limit switch 52 allows the current to be supplied to the motor 45
to set it in motion. More specifically, in the positions of these
members shown in FIG. 8, the energization of the solenoid 53 will
cause the pawl 51 to be disengaged from the groove 46 and, upon
this disengagement, the limit switch 52 is actuated to drive the
motor 45. Whereupon, the shaft 29 is rotated so that the cam 44
will be caused to rotate together with the cam means 28. During
this part of operation, the pawl 51 of the lever 49 is in
engagement with that portion of the cam 44 other than the grooves
46 and 47 or in other words the un-notched periphery portion of the
cam 44. Accordingly, the limit switch 52 is closed so that the
motor 45 is kept running. When, subsequently, the pawl 51 is
received in the groove 47, the limit switch 53 is opened, so that
the motor 45 is brought to a halt. With these members in the
positions described the apparatus is ready for tomography.
Subsequently, when the solenoid 53 is energized, the motor 45 is
set into motion. When the cam 44 returns, as the motor 45 is
rotated to its initial position, or in other words, when the pawl
51 is received in the groove 46, the rotation of the motor 45 is
halted again.
A description will now be given of the shape of the cam means 28.
In a tomographic apparatus utilizing X-rays, the X-ray tube moves
through a wide range of paths from one position to another.
Therefore, it would be reasonable to keep the X-ray tube at the
most harmless position, i.e., at the retreated position, whenever
the X-ray apparatus is not in use. Also, it will be understood
that, in case the selection of the cam means is performed in the
aforesaid manner, the rollers 32 and 33 must not contact the
bulging peripheries of the faces of those cams not selected. Also,
irrespective of the type of mechanism for selecting the cam means
in addition to the aforesaid one, the arrangement must be such that
any arbitrary set of cams may be selected as desired. Because of
these reasons, the position of the X-ray tube when the apparatus is
not in use, i.e., the retreated position of the X-ray tube, in the
tomographic apparatus of the present invention, is set at either
one of the four corners which are within the given range of
movement of the X-ray tube. In order to accomplish this purpose,
the positions of the cam means are arranged so that the rollers 32
and 33 will be in contact with the recessed portions of the cam
faces whenever the X-ray tube is in its retreated position. Also,
in case it is intended to take a tomogram by a rectilinear movement
of the X-ray tube, arrangement is such that as shown in FIG. 9A,
the X-ray tube will first move from its initial retreated position
a over to the second position b at which it is ready for
photography and which is located in the middle of the path in the
direction of axis Y and also at the end on the axis X, and
therefrom the X-ray tube will carry out a rectilinear travel to the
third position c. X-ray irradiation will be given during the travel
of the X-ray tube between the point b and the point c for the
purpose of photography. Upon completion of photography by X-rays,
the X-ray tube will be returned to its initial retreated position.
More specifically, the X-ray tube will travel at a sufficiently
accelerated velocity from the point b to the point b'. The
irradiation of X-rays will be started at the point b' and will be
stopped at point c' which is located this side of the point c. Upon
the stopping of irradiation of X-rays, the X-ray tube will be moved
at a progressively reduced velocity as it proceeds to the point c
at which the movement of the tube will be stopped. Therefrom the
X-ray tube will be brought back to its retreated position a. In
order to accomplish the aforesaid movement of the X-ray tube, the
cams are required to have cam faces with a specific shape. This
shape of cam face is as shown in FIG. 9B. The shape is shown in the
form in which it is developed in the rectilinear direction, which
is obtained by using the retreated position as the reference point
and by dividing the paths into the direction of axis X and the
direction of axis Y, and by connecting the respective points of
junction. More specifically, the movement of the X-ray tube from
point a to point b is only in the direction of the axis Y and not
the direction of axis X at all. Whereas, the movement from point b
to point c represents no change in the direction of axis Y, but
concerns strictly the axis X. From point c to the reference point
a, on the other hand, the movement of the X-ray tube follows a path
which represents a combination of the said two axes X and Y. In
order to convert the aforesaid rectilinear patterns into circular
cam face configuration, it is necessary that the distances between
the respective adjacent points be converted to the distances of
radii of the cams and that the respective ends of the radii be
connected to produce a continuous face line of each cam in such a
way that the starting point is in agreement with the ending point
which represents the said retreated position.
Also, when it is intended to perform a tomography by causing an
arcuate movement of the X-ray tube, the path of travel which is
followed by the X-ray tube is arranged as shown in FIG. 10A. More
specifically, the X-ray tube will move from its retreated position
a to the position b ready for photography, and therefrom, in
accordance with the instructions for photography, the speed of
movement of the X-ray tube will be sufficiently accelerated during
the part of path from point b to point c at which irradiation of
X-rays is started while making an arcuate movement passing the
points d, e and f in succession and returning to point c at which
the irradiation is ceased. The X-ray tube will move from point c at
a reduced velocity till it reaches point g at which it will stop
for a small length of time, and then it will return to the initial
retreated position a. In order to have the X-ray tube follow such a
series of movements, the shapes of the cam faces of the two cams
which form a set are shown in FIG. 10B in developed styles.
A description has been given of two instances, i.e., an instance
where the X-ray tube is required to make a rectilinear movement,
and another instance where the X-ray tube is required to make a
circular movement. It will be understood clearly that, when it is
intended to cause the X-ray tube to follow any other kind of path,
such a path of travel is divided into a directional component of
axis X and another directional component of axis Y and the
positions of the X-ray tube at the respective points on the
selected path are connected together and, thus, the required shapes
of the two cam faces can be obtained.
The cam faces have been described with respect to the instances
where the X-ray tube is given a motion at a constant speed during
the period of tomography. However, in case it is intended to
locally alter the velocity of travel of the X-ray tube during the
course of the path to be followed, this can be accomplished as
follows. With respect to that part of path where the travel
velocity of the X-ray tube has to be increased, the corresponding
portion of the cam face configuration will have a reduced length in
relationship with the time axis. Conversely, for the part of path
where the X-ray tube has to be moved slowly, the corresponding part
of the cam face configuration will have a prolonged portion of face
in relation to the time axis. In an extreme case where it is
intended to halt the movement of the X-ray tube for a certain
length of time, the corresponding portion of the cam face will have
a constant length of radius. By arranging the cam faces in the
aforesaid manner, there are obtained a set of cams having faces
which cause the X-ray tube to travel through the predetermined
respective sections of the path at different velocities while
following the same predetermined path.
A description will hereinafter be given of the operation of the
tomographic apparatus of the present invention having the foregoing
arrangement. As shown in FIG. 2, the patient 54 or the object to be
tomographed is laid on a bed 55. The bed 55 is moved in accordance
with the position for photography of the required region of the
patient's body. A film is loaded on the film holder 14. Then, one
of the selective switches provided on the control panel is operated
to select the particular set of cams for imparting to the X-ray
source a movement optimum for taking a tomography of the said
particular region of the object to be photographed. Whereupon, the
specific one 42 of the solenoids which is assigned for the
selection of the said particular set of cams is energized. As a
result, the engaging end portion 41 of the lever 40 is relieved of
its engagement with the pawl member 37. The pawl of the resulting
pawl member 37 is then caused to engage the groove 35 of the boss
34. As the shaft 29 is rotated, the required set of cams is caused
to rotate therewith. With the parts of the apparatus in this state,
the photography preparing button not shown which is provided on the
control panel is depressed. Whereupon, the solenoid 53 is energized
to close the limit switch 52 to rotate the motor 45. Thus, the
required set of cams is rotated. If the selected set of cams is for
a rectilinear movement of the X-ray tube, the position at which the
cams 28x and 28y for the axis X and for the axis Y are brought into
contact with their mating rollers 32 and 33 will undergo a change
in orientation in accordance with the curves shown in FIGS. 9A and
9B. More specifically, in the portion of the path between point a
and point b, the direction of axis X will not undergo any change in
orientation at all but only the direction of axis Y undergoes a
change. The cam 28y which produces this change in the axis Y will
push the roller 32 towards the right in FIG. 4. Since the bridge
arm 21 remains stationary, at such a time, only the bridge arm 23
and the arm segment 23' have their positions changed into the
angular positions with the joint 25 serving as the apex of this
angle, in the manner as shown in solid lines in FIG. 5. On the
other hand, the servo valve means 27 will supply a pressurized oil
to the hydraulic cylinder 19. As a result, the linking mechanism
which is comprised of the main link arms 5 and 6, the bridge arms
9, 10 and the auxiliary arms 11 and 12 is rotated clockwise about
the shaft 2 in FIG. 1. This rotation of the linking mechanism
causes the bridge arm 21 of the adjusting means, which is coupled
to a fixed point (B) of the main link arm 5, to be pushed towards
the right side in FIG. 4. Whereupon, the bridge arm 23 is rotated
counter-clockwise about the axis 31 of the roller 32 as shown by
broken line in FIG. 5 so as to bring the arm segment 23' to its
initial position. As the linkage which is comprised of link members
5, 6, 9-12 is rotated up to the required position, the said arm
segment 23' returns completely to its initial position, and the
actuator rod of the servo valve means 27 also resumes its normal
position, thereby suspending the supply of the pressurized oil to
the hydraulic cylinder 19. The hydraulic cylinder 19 continues to
be operative until the desired position of travel in the direction
of the axis Y which is established by the cam 28y selected in the
aforesaid manner comes into agreement with the current positions of
both the film and the X-ray tube 13. Then, in accordance with the
rotation of the cams, the linking mechanism which supports both the
X-ray tube and the film holder 14 is caused to tilt in the
direction of the axis Y. When the X-ray tube reaches point b shown
in FIG. 9A, the pawl 51 of the lever 49 engages the groove 47 of
the cam 44, so that the limit switch 52 is opened to stop the
rotation of the motor 45, and with this the preparation for
photography is completed.
After confirming the conditions of photography, the exposure
button, not shown, which is provided on the control panel is
depressed. Whereupon the solenoid 53 is energized to set the lever
49 into motion. As result, the limit switch 52 is actuated to
rotate the motor 45, followed by the revolution of the selected cam
means. Since the photography is performed during the course of
travel of the X-ray tube between point b and point c in FIG. 9A,
the face of the cam 28y which is assigned for the control of
direction of the axis Y undergoes no change in terms of its radius,
whereas only the cam 28x which controls the axis Y exhibits
rectilinear changes in its radius during the said portion of path.
As a result, the roller 33 is pushed so that the bridge arm 22 and
the arm segment 22' will be at an angle, causing the servo valve
means 26 to be actuated. Accordingly, a pressurized oil is supplied
to the hydraulic cylinder 18, so that the linkage which is formed
by link members 5, 6, 9-12 is rotated clockwise about the pins 7
and 8 serving as the fulcrums in FIG. 2. As a consequence, the
X-ray tube 13 is moved clockwise. As the cam 28x rotates
progressively, the X-ray tube 13 is moved farther. During the
predetermined portion of path of its travel, X-rays are emitted
from the tube 13 so that the photograph by X-rays is produced.
At the point c in FIG. 9A representing the final position of
movement of the X-ray tube in the course of photography, the
inclination of the face of the cam 28x for controlling the axis X
becomes opposite to the angle of the inclination of the face of the
cam 28y for controlling the axis Y. Therefore, the bridge arm 22 as
well as the arm segment 22' will undergo a change in their
positions in a direction opposite to the direction assumed by them
in that part of operation described previously. Because of the
change in positions of these link members, the servo valve means 26
and 27 are, at this time, actuated simultaneously to pull back the
actuator rods of the hydraulic cylinders 18 and 19 so as to actuate
the said linkage -- which is comprised of link members 5, 6, 9-12
-- to bring the X-ray tube 13 to its retreated position. During
this part of the operation, it should be noted that the amount or
angle of inclination of the cam shape is arranged different for the
cam for controlling the axis X than for the cam for controlling the
axis Y, and that, therefore, the component of movement in the
direction of the axis X of the X-ray tube is different from the
component of movement in the direction of the axis Y in proportion
to the respective different angles of facial inclination of these
two cams 28x and 28y. When the cam means returns to the initial
position, the pawl 51 of the lever 49 plunges into the groove 46 of
the cam 44. As a result, the limit switch 52 is opened to halt the
rotation of the motor 45, followed by the stopping the driving of
the cam means. As a result, the X-ray tube 13 returns to its
retreated position at which the apparatus is prepared for the next
photography.
If the selected set of cams is assigned for imparting to the X-ray
tube a circular movement, the depression of the button indicated as
"preparation" not shown will cause the X-ray tube to move from its
retreated position to the preparatory position. Upon subsequent
depression of the exposure button, the set of cams will control the
servo valve means 26 and 27 so that the X-ray tube will make the
required circular movement. Along with this, the hydraulic
cylinders 18 and 19 will be actuated in accordance with the
revolutions of the cams for controlling the axis X and the axis Y
to give the X-ray tube the desired circular movement. Upon
completion of this circular movement of the X-ray tube 13, this
X-ray tube is returned to its initial retreated position. When it
is intended to have the X-ray tube follow a path different from any
one of the paths stated above, such a desire can be accomplished by
selecting a set of cams having cam faces corresponding to such a
path. The operation and actions of the members for such an
operation will be easily understood by reading the description
dealing with FIGS. 9A and 9B and also from FIGS. 10A and 10B.
The kinds of paths of travel of both the X-ray tube and the film
which are available include straight line, large circle, small
circle, oval, hypocycloid, spiral and any other desired patterns.
Any one of these kinds of travel paths can be obtained by merely
selecting or replacing the cam means.
When the X-ray tube and the film are moved by following the paths
selected from one of these kinds of courses and when a beam of
X-rays is irradiated during the travel of these two members on the
said paths, there is focused -- on the film -- only the image in
the plane of the tomogram of the object which is parallel with the
film face and which includes the point A located on the straight
line connecting the focus of the beam from the X-ray tube 13 and
the center of the film, whereas the images of the regions of the
object located above and below the plane of tomogram and not
required to be photographed will be in a path which is similar to
that of the movement of the X-ray tube and will appear on the film
as blurred images so that they can be ruled out easily. During the
travel of the X-ray tube, by locally increasing the velocity of
movement of the X-ray tube for those unnecessary regions of the
body of the object where the path of travel of the X-ray tube
becomes parallel with such regions, i.e., by increasing the said
velocity so that it will be greater than the velocity for the
remaining region which is required for the photography, so as to
control the amount of X-rays per unit time for the non-required
regions so that it is smaller than for the required region, it is
possible to obtain a tomogram where the images of those
non-required regions has a much reduced density and, therefore,
such blurred images can be ruled out more satisfactorily.
As has been stated above, according to the present invention,
complicated or any specific paths of travel of the X-ray tube which
cannot be obtained according to the known tomographic apparatuses
can be very easily obtained, simply by the provision of cams having
cam faces corresponding to such paths. Therefore, it is possible to
give the X-ray tube the optimum path of travel for the photograph
of any required region of the object, and also to obtain a clear
tomogram wherein the images of those un-required regions are
satisfactorily blurred so as to be easily ruled out. Also, in any
part of the path of travel of the X-ray tube, it is possible to
move, as desired, the X-ray tube and the film at any specific
different velocities by a mere shaping of the faces of the cam
means. This allows the apparatus of the present invention to
produce the same effect as that produced by the selective
irradiation method of the prior art which requires complicated
apparatus structure and complicated operations, merely by the
selection of a required set of cams. As stated above, the
tomographic apparatus of the present invention having a simplified
structure can be used for photographic conditions over a wide
range, and yet such use can be effected easily and positively by an
operator having little technical training in this field, in view of
the fact that any desired photographic program can be established
by the mere selection of the required set of cams.
The example which has been described and shown in the drawings
employs a hydraulic servo mechanism for the control of movements of
both the X-ray tube and the film. It should be understood by those
skilled in the art that this servo mechanism can be replaced by any
known electrical or electronic control mechanism or by a pneumatic
servo mechanism to obtain the same effect. It should be understood
also that the present invention is not restricted to the said
example, but that many other changes and modifications may be made
without departing from the spirit of the present invention.
Furthermore, various applications having all of the features of the
present invention are possible also. It should be understood ,
therefore, that such changes, modifications and applications are
equivalent to what is stated in the appended claims and are all
included within the scope of these claims.
* * * * *