U.S. patent number 3,752,990 [Application Number 05/154,530] was granted by the patent office on 1973-08-14 for x-ray device having an anode tube with filtering means thereon.
Invention is credited to Heimbert Fischer.
United States Patent |
3,752,990 |
Fischer |
August 14, 1973 |
X-RAY DEVICE HAVING AN ANODE TUBE WITH FILTERING MEANS THEREON
Abstract
A device for use in the production of dental X-ray photographs
comprises a hollow-anode X-ray tube projecting from a housing with
the tube specially mounted to absorb shocks and stresses imposed on
the anode tube. The anode tube which projects from the housing is
preferably shielded when not in use by a projecting tube slidable
relative to the housing. The device may also include a second X-ray
tube for intra-oral and extra-oral photography with this second
tube emitting X-rays at 90.degree. to the axis of the hollow anode
X-ray tube. Prefiltering material may be provided on the head of
the anode tube or the head of the anode tube may be specially
shaped so that uniform prefiltering of the radiation from the anode
tube occurs over the beam angle necessary for full-mouth
photography.
Inventors: |
Fischer; Heimbert (D 7801
Vorstetten, DT) |
Family
ID: |
39711874 |
Appl.
No.: |
05/154,530 |
Filed: |
June 18, 1971 |
Foreign Application Priority Data
|
|
|
|
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Jun 22, 1970 [DT] |
|
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P 20 30 624.5 |
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Current U.S.
Class: |
378/38; 378/121;
378/159; 378/193 |
Current CPC
Class: |
H05G
1/06 (20130101); H05G 1/04 (20130101); A61B
6/145 (20130101); H01J 35/26 (20130101); H01J
35/32 (20130101) |
Current International
Class: |
A61B
6/14 (20060101); H01J 35/00 (20060101); H01J
35/26 (20060101); H01J 35/32 (20060101); H05G
1/04 (20060101); H05G 1/00 (20060101); H01j
035/16 (); H01j 005/16 () |
Field of
Search: |
;250/70,86,90
;313/55,59 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lindquist; William F.
Claims
Having thus described my invention, what I claim as new and desire
to secure by Letters Patent of the United States is:
1. In an X-ray device for use in producing dental X-ray
radiographs,
a. a tube housing;
b. anode tube means projecting from said tube housing, said tube
means having a longitudinal axis;
c. an anode mounted in said anode tube means adjacent the end of
said anode tube means opposite said tube housing, said anode, when
bombarded by electrons, emitting X-rays over a beam angle that
extends both radially and longitudinally of said anode tube means
to produce a full-mouth radiograph when said anode tube means is
correctly positioned within a patient's mouth; the improvement
d. wherein said anode tube means comprises filtering means, said
filtering means having a variable thickness along the longitudinal
axis of said tube means such that the X-rays pass through
substantially equal thicknesses of filtering material irrespective
of the emission angle relative to the longitudinal axis of said
anode tube means whereby the X-rays are uniformly filtered over the
entire beam angle.
2. The X-ray device as set forth in claim 1 wherein the thickness
of said anode tube means varies such that all X-ray radiation
emitted within said beam angle travels a path of equal length
through the wall of said anode tube means.
3. The device as set forth in claim 2 wherein said filtering means
comprises a first portion of filtering material of uniform
thickness forming said anode tube means and a second portion of
filtering material of varying thickness covering preselected areas
of said first portion of filtering material wherein said second
portion of filtering material provides additional filtering to said
X-ray radiation such that said X-ray radiation travels equal path
lengths within said filtering means.
4. The apparatus as set forth in claim 3 wherein said anode tube
means comprises:
a. an anode tube of cylindrical cross sectioning having walls of
uniform thickness wherein said walls comprise said first portion of
said filtering means; and
b. an applicator tube for covering at least a portion of said anode
tube means, surrounding said at least a portion of said anode tube,
wherein said second portion of said filtering means is affixed to
said applicator tube.
5. The device as set forth in claim 2 wherein said anode tube means
comprises:
a. an anode tube including said filtering means; and
b. an applicator surrounding said anode tube.
6. The device as set forth in claim 2 wherein said anode tube means
comprises:
a. an anode tube;
b. an applicator surrounding said anode tube; and
c. wherein said filtering means comprises a first portion disposed
of said anode tube and a second portion disposed on said
applicator.
7. The apparatus as set forth in claim 1 wherein said anode tube
means is formed from a ceramic based material such as a ceramic
oxide.
Description
BACKGROUND OF THE INVENTION: FIELD OF THE INVENTION
This invention relates to devices for use in producing X-ray
photographs, particularly dental X-ray photographs.
The invention is particularly concerned with devices for use in
producing dental X-ray photographs which make use of special
hollow-anode X-ray tubes which are quite distinct in construction
and function from the usual diagnostic X-ray tubes.
BACKGROUND OF THE INVENTION: DESCRIPTION OF THE PRIOR ART
In the presently known tubes of this hollow-anode type, the whole
electrode system -- comprising a cathode emitting the electrons, a
control electrode affecting the focussing, and a usually conical
anode arranged in the anode tube with a collecting or focussing
coil mounted on the anode tube and also affecting the focussing of
the electron stream -- is so constructed that it is formed from two
or three mechanically completely separate electrode units as far as
adjustment of the system is concerned. In these hollow-anode X-ray
tubes the focal spot is created at the end of a hollow-anode tube
externally of the actual X-ray tube casing and with a conical anode
it is at the cone tip pointing towards the cathode.
In the X-ray tubes used in dental medical diagnostic treatment for
producing full-mouth or panoramic photographs, in which the anode
tube is introduced into the mouth, the focal spot of the tube must
be kept very small on account of the comparatively small focal
length necessitate by these photographic techniques and on account
of the lack of sharpness in the image which would otherwise arise,
with the result that the electrode system of such a tube must be
extremely accurately focussed and adjusted initially and must then
remain so. The danger of the tube becoming out of adjustment is
greater the smaller the diameter of the anode tube and the more
sensitive the electrode system of the X-ray tube.
Since the wall thickness of the hollow-anode tube, which is barely
the size of a finger in diameter, must be kept small and since the
electron stream must be very accurately adjusted because of the
comparatively small focal spot, the user of such tubes protects the
very highly sensitive anode tube, which is formed from very soft
annealed copper at those places where in the event of a mechanical
stress the greatest bending moment is exerted, by placing a
protective cap over the tube housing in the inactive position of
the device to protect the anode tube from damage and defocussing.
When preparing the instrument for use and when actually using the
instrument. the protective cap is removed in all cases.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an X-ray
device, comprising a hollow-anode X-ray tube mounted in a housing
and provided with an anode tube projecting from the housing, which
is resistant to inadvertently applied stresses acting on the device
and which is also protected against defocussing and movement out of
adjustment.
This is achieved in accordance with one aspect of the invention in
that the casing of the hollow-anode X-ray tube is rigidly connected
to mounting means to which is connected resilient support means,
said support means being secured to the housing and extending
between the housing and the casing of the hollow-anode X-ray tube.
In this way, in the event of a blow on the anode tube, this tube
together with the whole X-ray tube and the focussing means rigidly
connected thereto together yield to the blow, and then return to
the positions occupied before the blow took place, so that in
consequence the adjustment of the focussing is not adversely
affected.
In the X-ray device of the present invention the X-ray tube casing
including the part of the anode tube adjacent to the cathode is
preferably formed of a ceramic based material, such as a ceramic
oxide for example, since this provides the anode tube with
substantially higher resistance to bending stresses than the copper
components previously generally used.
Since the thickness of the objects in the whole of the irradiated
field of interest for full-mouth photography is approximately the
same, it is of great importance that any prefiltering of the
radiation within the radiation beam angle should be constant. This
is not the case in the presently known hollowanode constructions in
which the anode tubes and/or the applicators placed over the tubes
have a constant wall thickness in the vicinity of the source of the
emitted radiation, with the result that the X-rays follow different
length paths in their passage through the wall in dependence on the
angle at which they are emitted and are consequently subjected to
differential filtering. This disadvantage is overcome in accordance
with a preferred feature of the present invention by the provision
of prefiltering material on the head of the anode tube containing
the anode, the distribution being such that uniform perfiltering of
the radiation occurs over the whole beam angle necessary for
full-mouth examination. This may be achieved by making the wall at
the head of the anode tube of non-uniform thickness such that all
X-rays passing through the tube wall at whatever angle traverse
equal length paths through the tube wall. Alternatively, it is
possible to provide additional prefiltering material on the head of
the anode tube in addition to the actual tube material, this
additional prefiltering material being provided in such a way that
the X-rays which on the basis of their angle of emission traverse a
shorter path length through the tube wall pass through a greater
mass of prefiltering material than the X-rays which traverse a
longer path length.
In photographing the upper jaw it is sometimes necessary in special
cases to provide a cut-out in the film strip for the nose of the
patient and to photograph the unphotographed nose part in the usual
manner, i.e., with the film inside the mouth and with the X-ray
tube outside the mouth. The presently known hollow-anode X-ray
tubes cannot be used in this way. Photographic views of the whole
jaw region are produced with the presently known hollow-anode X-ray
tubes when inserted into the mouth for dental X-ray photographs,
and these overall pictures obviously give information about the
general status of the teeth. However, with these X-ray photographs
one takes photographs of the whole of one or both jaws from one
focal spot position, which automatically means that individual
teeth or whole groups of teeth are shown heavily distorted on the
X-ray film relative to their anatomically correct images or
positions in the jaw. Because of this, for specific diagnosis of
individual teeth it is necessary to take individual photographs of
teeth or groups of teeth by the distortion free intra-oral or
extra-oral techniques which are presently known. In order to carry
out these two basically different photographic techniques the
dental practitioner must have two different X-ray machines
respectively adapted for the separate photographic techniques and
with which one has to use X-ray tubes which are likewise different
and adapted respectively for the different photographic
techniques.
It is therefore extremely desirable to provide a device equipped
with a hollow-anode X-ray tube which is also such that distortion
free photographs of individual objects can be achieved with it as
with the known intra-oral and extra-oral photographic techniques.
According to the present invention this is achieved by providing a
second X-ray tube for intra-oral and extra-oral photographs within
the housing of the device and in addition to the hollow-anode X-ray
tube, the direction of emission of radiation from the second tube
being at an angle of substantially 90.degree. to the longitudinal
axis of the hollow-anode X-ray tube. A high voltage transformer for
both tubes is preferably also mounted within the housing of the
device so that in this case the device can be described as a
one-piece instrument.
Instead of having two separate X-ray tubes it is alternatively
possible to use a double X-ray tube suitable both for full-mouth
photography and also for intra- and extra-oral photography, such as
double X-ray tube having two separate cathode filaments in a common
casing. This results in a system which can be made extremely
compact. On the other hand, a device using two separate X-ray tubes
has the possible advantage that the X-ray tubes may be of a simpler
and cheaper construction and that in the event of failure of one
complete X-ray system or one X-ray tube the other X-ray system is
still usable until replacement or repair of the failed system or
tube. When using a common tube casing for both X-ray systems the
casing may be secured to mounting means which includes an electron
reflection target in alignment with the cathode filament for the
said second X-ray tube and a side window through which X-rays from
the target are beamed.
In order that the invention may be more fully understood a number
of embodiments in accordance therewith will now be described by way
of example and with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view through a part of a first
embodiment of device in accordance with the invention, the device
comprising a hollow-anode X-ray tube, here shown in its inactive
position;
FIG. 2 is a similar cross-sectional view of the device shown in
FIG. 1 but with the hollow-anode X-ray tube in its operational
position;
FIG. 3 is a similar cross-sectional view through a second
embodiment of device in accordance with the invention, this device
comprising a double X-ray tube adapted both for panoramic
full-mouth photography and also for intra-oral and extra-oral
photography, and with the device here shown in its operational
position for the last-mentioned photographic technique;
FIG. 4 is a longitudinal sectional view through the head of the
anode tube of a hollow-anode X-ray tube, the upper half (A) of the
illustrated tube being of known form and the lower half (B) of the
illustrated tube being of modified novel form;
FIG. 5 is a longitudinal sectional view through the head of the
hollow-anode X-ray tube illustrating the radiation beam-angle
necessary for panoramic full-mouth examination and of interest in
relation to prefiltering considerations;
FIG. 6 is a schematic longitudinal sectional view through a third
embodiment of device in accordance with the invention, the device
here comprising two separate X-ray tube systems;
FIG. 7 is a front end elevational view of the device of FIG. 6;
FIG. 8 is a schematic longitudinal sectional view through a fourth
embodiment of device in accordance with the invention, again
comprising two separate X-ray tube systems; and,
FIG. 9 is a front end elevational view of the device of FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the embodiment of the device shown in FIG. 1 the X-ray tube
comprises a casing 16 fitted with an anode tube 9 carrying a
conical anode 17; a mount 1 at anode potential and rigidly
connected to the tube casing 16; and a focussing unit 5 which is
fixedly connected to the tube system. The mount 1 is connected to a
housing 4 of the device by means of a resilient link 2, for example
in the form of a spring element. A high voltage generator (not
shown) for the X-ray tube is mounted in a suitable manner within
the housing 4 of the device.
In spite of the provision of a resilient supporting link 2 it is
important to provide additional protection for the exposed
comparatively slender anode tube 9 in its inactive position. For
this purpose a protecting tube 15 is provided which is secured so
as to be displaceable in the axial direction over the housing 4 of
the device. In FIG. 1, this protecting tube 15 is shown in its
operative protective position enclosing the anode tube 9. The tube
15 is provided with an aperture 18 in its end face to provide for
passage of the anode tube 9 therethrough.
Additional springs 7 are provided between the housing 4 and the
mount 1 on the tube casing 16 in order to adjust the flexibility
and resiliency of the link 2 so that it will absorb forces arising
as a result of impacts or pressures on the anode tube 9 and will
return the tube system to its original setting as soon as such
foreign external forces no longer act on the anode tube.
In the illustration shown in FIG. 2 the protecting tube 15 has been
withdrawn back over the housing 4 of the device so that the anode
tube 9 is located in its operational position in which it can be
inserted into the mouth if panoramic photography of the whole of a
patient's mouth is to be carried out.
The embodiment of the invention which is shown in FIG. 3 comprises
a double X-ray tube by means of which it is possible to use both
the hollow-anode technique for panoramic full-mouth photography and
also intra-oral and extra-oral photographic techniques for
examination of individual teeth. In this embodiment a tube side
window 11 with an electron target disc 10 arranged adjacent thereto
are provided in the mount 1 as a part of the tube casing 16, in
addition to the anode tube 9 which has the anode 17 as an electron
target point. A filament arrangement 13 acting as the cathode
associated with the anode 17 and a filament arrangement 14 acting
as the cathode associated with the electron target disc 10 are
provided within the tube casing 16. The mount 1 is at anode
potential.
In this embodiment the cathode filaments 13 and 14 which are
necessary for the two electrode systems are mounted on a cathode
support 12 and can be selectively switched on individually
according to the desired type of photographic examination to be
effected with the device.
In this embodiment, apertures are provided in the housing 4 and in
the axially displaceable protecting tube 15 for the passage of the
X-rays emitted through the tube side window 11. These apertures are
so arranged that when the device is used for hollow-anode
photographic examination the protecting tube 15 masks the aperture
in the housing 4 in front of the side window 11 and uncovers the
free end of the anode tube 9, while when the device is used for
intra-oral or extraoral photographic examination the protecting
tube 15 encloses the free end of the anode tube 9 and unmasks the
side window 11.
The upper half of FIG. 4 of the drawings, designated as A, shows
the head of a known form of hollow-anode X-ray tube in which the
anode tube 9 is cylindrical and of uniform wall thickness in the
radiating region. In such circumstances the X-rays coming from the
anode 17 within a beam angle .alpha. and which do not pass through
the wall of the anode tube at right-angles along the line S, for
example rays passing along the lines S1 to S4, must penetrate
larger amounts of the material of the anode tube. These rays are
therefore prefiltered differentially and this has an extremely
unfavourable effect on the quality of the image on the X-ray
photograph.
In the lower half of FIG. 4, designated as B, there is there shown
how this differential prefiltering of the X-rays is avoided by the
use of a special configuration for the wall thickness of the head
of the anode tube 9. With the wall thickness made non-uniform as
shown the same length of path S is traversed by all radiation from
the anode 17 throughout the whole beam angle which is of
interest.
FIG. 5 shows, in relation to an anode tube 9 with a conical anode
17 and fitted with an applicator 8 over the anode tube, the tube
and applicator being shown inserted into a patient's mouth, that
the beam angle .alpha. shown in FIG. 4 is in fact necessary for
full-mouth photographic examination.
Alternatively, it is possible to provide additional prefiltering
material on the head of the anode tube 9, preferably on its
external surface, with such a distribution or gradation that the
X-rays within the beam angle .alpha. which follow a shorter path
through the wall of the head of the tube traverse a greater mass of
prefiltering material than the X-rays which follow a longer path.
In this case, the cylindrical wall of the anode tube, as is shown
in the upper part A of FIG. 4, may have its thickness unchanged.
Alternatively, this additional prefiltering material may be
provided on the applicator 8 which is slidable over the anode tube
9, or it may be provided partially on this applicator and partially
on the anode tube itself. By these means one can ensure in a simple
manner that all the X-rays coming from the anode 17 are prefiltered
to the same extent irrespective of their direction, and preferably
to a degree equivalent to the case of the rays taking the longest
path S4.
The X-ray tube casing, including the part of the anode tube
adjacent to the cathode, is preferably made from a ceramic-based
material having high resistance to bending stresses. Among the best
materials are ceramic oxides, particularly beryllium oxide, which
can absorb large bending moments and which at the same time are
permeable to the magnetic field necessary for focussing the
electron stream.
In each of the embodiments described above in which the mounting of
the X-ray tube within the housing of the device is accomplished by
means of an intermediate element such as the resilient link 2, this
resilient supporting link need not necessarily consist of a spring
element, but for example can alternatively be in the form of
resilient membranes, or in the form of ball and socket joints in
association with individual springs spaced on a circle around the
tube. In each case the arrangement is such that the reaction to
bending stresses of the resilient link due to forces acting from
externally on the anode tube 9 is smaller than the reaction to
deformation of the anode tube 9 due to the external forces acting
thereon.
Focussing unit 5 shown in FIGS. 1 to 3 may be an electromagnetic
unit or a permanent magnet system. It will further be appreciated
that an electrostatic focussing unit could alternatively be
used.
In the embodiment shown in FIGS. 6 and 7 there is provided a
hollow-anode X-ray tube suitable for full-mouth or panoral
photographic examination and comprising the X-ray tube casing 16,
the anode tube 9, and an associated transformer 6 mounted on an
axis 19 which is parallel to but displaced upwardly relative to the
longitudinal axis 20 of the housing 4 of the device. Parallel to
this tube 9, 16 is provided an intra-oral tube 21 having its
longitudinal axis 22 displaced downwardly relative to the
longitudinal axis 20 of the housing 4 of the device. The direction
23 of the emitted radiation from the intra-oral X-ray tube 21 is at
90.degree. to the longitudinal axis 19 of the hollow-anode X-ray
tube 9, 16.
In this embodiment the hollow-anode X-ray tube 9, 16 is resiliently
mounted in the housing 4 by means of springs or a spring bellows or
a membrane 2. A protecting tube 15 is provided to protect the anode
tube 9. The protecting tube 15 is displaceable along the axis of
the X-ray tube such that its cylindrical wall is displaceably
positioned within the housing 4 and only its forward end wall
portion provided with an aperture 25 for the anode tube 9 lies
outside the housing 4. A window 24 for the passage of radiation
from the intra-oral tube 21 is provided in the cylindrical wall
portion of the protecting tube 15. This window 24 is only aligned
with the output from the intra-oral tube 21 when the hollow-anode
X-ray tube 9, 16 is not operational and is enclosed by the
protecting tube 15. However, the window 24 is not in alignment with
the axis 23 of the radiation from the tube 21 when the protecting
tube 15 is displaced inwardly and the hollow-anode X-ray tube 9
extends in its operative position.
The embodiment illustrated in FIGS. 8 and 9 only differs from that
shown in FIGS. 6 and 7 in that the two X-ray tubes 9, 16 and 21 are
not arranged one below the other but are positioned on a common
axis 22 one behind the other within the housing 3. In this
embodiment the housing 3 is not cylindrical but has an inverted
teardrop shape cross-section. The hollow-anode X-ray tube is
mounted within the housing 3 in almost the same way as in the
embodiment shown in FIGS. 6 and 7 but below the pivot axis 20 of
the housing, while the second X-ray tube 21 lies on the axis 22
behind the hollow-anode X-ray tube 9, 16. The two transformers 6
and 17 of these two X-ray systems are provided as a one-piece unit
positioned within the upper portion of the housing which is of
larger cross-section.
In both the embodiments shown in FIGS. 6 to 9 the direction 23 of
the emitted radiation from the intra-oral tube 21 makes an angle of
90.degree. with the longitudinal axis 19 of the hollow-anode X-ray
tube 9, 16.
The casing of the intra-oral or extra-oral X-ray tube 21 preferably
consists of a ceramic oxide with the tube side window being formed
from sintered beryllium oxide.
Since certain other obvious changes may be made in the device
without departing from the scope thereof it is intended that the
above description of certain embodiments of the invention be
interpreted in an illustrative and not a limiting sense.
* * * * *