Note: Descriptions are shown in the official language in which they were submitted.
~38 [)~3
1 PHN 9038
The invention relates to an X-ray examin-
ing device, comprising an X-ray image intensifier, pro-
vided with a fibre-optical exit window, an optical image
transfer system, and a television pick-up tube and moni-
tor.
An examining device of this kind is known
from United States Patent Specification 3,912,936. A
device described therein is suitable for medical X-ray
examination during which direct visual observation
(fluoroscopy) as well as image recording (exposure) are
; possible. It is customary to project a part of the
image-carrying light beam emerging from a lens system,
situated between an X-ray image intensifier tube and a
television pick-up -tube, onto a filml and the other part
onto a target of the television pick-up tube. For this
purpose, use is made of, for example, a semi-reflective
semi-transparent mirror or a prism. Particularly for
making a ~ilm recording, a system of this kind requires
a comparatively high radiation energy, be it for only a
brief period of time. During the direct visual observ-
ation, a much lower radiation energy suffices, be it
that the duration of this observation is much longer.
In principle image information is lost in both methods,
either by loss in the distribution optical system or by
;~ 25 non-optimum operation of the lens system due to the
~ space to be held open for the distribution optical sys-
; tem.
'
.
1~L38~3
12~ 1g78 2 PHN 9038
The in~en-tion has for its object to provide
an X ray examining device in which a substantially lower
radiation dose suffices, notably for filln racordings, while
substantially all image information emerging from the X-
ray image intensifier is effectively used for both methodsof observation. To this end, an X-ray examining devise of
the described kind is characterized in that a film record-
ing material can be arranged between the X-ray image inten-
sifier and the optical system and can be pressed against
the exit window of the X-ray image intensifier.
In an X-ray examining device in accordance
with the invention, notably when a fibre-optical window is
used as the exit window of an X-ray image intensîfier, sub-
stan-tially all image information emerging from the X-ray
image intensifier tube is recorded as a result of the
direct contact with the X-ray image intensifier tube during
film recording. As a result, an image can already be formed
by means ~f a comparatively small radiation dose, the quan-
tum noise in the image-carrying beam then usually deciding
the dose limit.
~ In a preferred embGdiment in accordance with
- the invention, the optical image transfer system is opti-
mally adapted to the fact that a beam distribution system
need no longer be included therein. Therefore, a more com~
pact construction can be realized, in which less Yigne-t-
ting occurs so that improved image transfer to the tele-
vision pick-up tube is ensured. ~or the control of the
light beam on the target of the -television pick-up tube
to be used, a preferably automatically adjustable aperture
is included betwsen two parts of the optical system in a
- preferred embodiment.
In a further preferred embodiment, use is
made of a second fibre-optical window which can be readily
exchanged so that, should damaging occur due to the pres~
sing of the film material, it is merely necessary to re-
place this window, whilst the Y--ray image inlensifier tube
itse]f is not damaged.
-~ In a further preferred e~bodiment yet, a
~3~
12~12-1978 3 PMN 9038
~omparatively small optical element is included between
two lens parts of the lens system iI; order to project in-
formation or a code around an image to be recorded.
Contrary to known devices, the film material
~ is arranged in the image-carrying light beam without an
intermediate adjustable aperture. A preferred embodiment
in accordance with the invention comprises means for con-
trolling the output intensity of the X-ray image intensi-
fier. ~or this purpose use can be made of, for example,
1~ high voltage control of the X-ray image intensifier tube
or a channel intensifier plate. Use can alternatively be
; made of filters, such as grey filters or polarization fil~
ters, whereby the light beam emergin.g from the X-ray image
intensifier can be controlled.
Some preferred embodiments of the device in
accordance with the inven-tion will be described in detail
hereinafter with reference to the accompanying diagramnla-
tic drawing.
The drawing shows an X-ray examining d.evlce
comprisin.g an X-ray source 1 for generating a beam of X-
rays 2 which irradiates an object 3 to be examined, and
an ~-ray image intensi-fier tube 4 for intercepting the
image-carrying X~ray beam 2. The X-ray image intensifier
tube shown compri.ses a concave entrance window 5 which is
25 pxeferabl~r made of a metal such as titanium or aluminium,
and a fibre optical exit window 6. The tube accommodates
a luminescent screen 7 which is preferably made of Th acti-
vated or Na activated CsI which is deposited on a substrate
8. The CsI screen is preferably provided with a structure
30 as described in United States Patent Specification 3,825,
763. As a resul-t of the use of the screen structure des-
cribed therein, optin1um resolution is obtained by the
buil.t-in columnar structure in that transverse sca-ttering
of luminescerlt light does not occur in the layer, whilst
at the same time a high X-ray absorption is achicved in
that -the layer thiclcness may be chosen to be comparatively
: large9 for example, of from 200 to 300 /um. A photo cathode
9 is provided on the lu~inescent screen, with or without
~L~38~9~3
12-12-1~7~ 4 PH~T S038
an intermedlate separating layer. By means of a screen
electrode 10, provided be-tween electrodes 11 and 12 and an
output electrode 13, an electron beam which is formed by
the luminescent light in the photo cathode is imaged on a
luminescel1t screen 14 which is preferably provided direct-
ly on the exit window. Brightness control of the X~ray
image intensifier tube can be realized, for example, in
known manner by varia-tion of the high voltage between the
photo cathode 9 and the exit screen 14. It has been found
that use is advan$ageously made of an X-ray image intensi-
fier tube comprising a thick metal layer on the inner side
of the exit luminescent screen, as described in United
States Patent Specification 3,774,o38, or of the addition
of a channel plate multiplier between the photo cathode
; ~5 and the exit luminescent screen. The use oP a channel
multiplier plate offers the advantage that it is no-t
necessary to vary the high voltage, a comparatively small
variation of a voltage to be applied across the channel
plate suffices.
Using an optical system 20, comprising two
sections 21 and 22 and being known as a basic op-tical sys-
tem or tandem optical system, an image transmitted by the
exit window is imaged on a target 23 of a television pick-
up tube 2~. The optical system 20 is preferably construct
ed so that the beam is parallel between the two sections
21 and 22; as a result, local stopping is possible without
giving rise -to a significant disturbance of the image.
For the purpose of stopping, an adjustable aperture 25 is
locally provided, said aper-ture preferab]y being constructed
so as to be automatically adjustable. A video signal de-
rived frorn the television pick-up tube càn be displayed
on a monitor 26 for observation.
In accordance with the invention, photo-
sensitive material 27, for example, filrn material, can be
35 introduced between the exit window of the X-ray image
intensifier tube and the first lens 21 of the basic opt-ical
system. In the present embodiment, a film holder comprising
a first chamber 28 for unexposed film ma-terial and a
~L3~3~93
12~12-1975 5 PHN 9038
second chamber 29 for exposed fllm material is lncl-lded.
These film holders may contain a roll of film rnaterial as
well as a stack of cards provided with film windows. The
film material is displaceable -therebetween, for example,
in the form of` a long strip. Use can alternatively be made
of loose film plates which are accommodated, for example,
as a window in cards of a card system~ so that after de-
velopment and any fur-ther treatment~ direct filing and
projection at a later stage are possible. The fllm carrier
is arranged to be slidable or pivotable into the space be-
tween -the exit window and the lens system and can be pres-
sed against the exit window by means of a ring 3O. When
a pressing mechanism of this kind is combined with an
- evacuation device for the air between the exit window and
the film carrier, a reliable direct con-tact can be realized.
~or each film recording, a film carrier is inserted, pres-
sed, exposed and advanced again. ~inematrographic record
ing is also possible in a completely identical manner~ For
optimum exposu-re of the film, a preferred embodiment u-ti-
izes the fact -that the ~ilm carrier is always -to some
extent transparen-t for the light to be recorded. The trans-
mitted light is intercepted, for example, on Ihe television
camera or on a photo cell, and the signal derived there-
from is used in known manner for determining the expvsure
time for tlle film recording. The quantity of light to be
projected onto the television pick-up tube can be control-
led by means of the aperture 25 which is preferabl-y con-
structed as an automatically adjustable iris aperture.
In a prefarred embodiment, an additional optical element
31, for example, a prism, is included for projecting,
.. . ~ . . .
for example, patient data on an edge portion of a film
image to be rec^rded. When the opt:ical element 31 is con-
structed ~s a l;ght distribution system, this information
can be projected onto the film material as well as onto
tlle te:levision pick-up tube. lhe element 31 may be compa-
ratively small and can be arranged so tha-t the image--
carrying beam is no-t disturbed thereby, so that no rele-
vant fluoroscopy data are los-t.
~L3~3~9~
12-12-1978 6 PHN 9038
Because the recording takes place directly
from the exit window of the X-ray image intensifier tube,
having a diameter of, for example, 25mm, in an X-ray
examining device in accordance with tl~e invention, not
only -tha advantage of high sensi$ivity is obtained, but
also the advantage of a substantial saving as regards the
film material. As a result of the absence of an image dis-
-tribution system, which m-ust be clisplaced each time be-
tween fluoroscopy and recording in known devices, a device
having a high degree of reliability is realized.
.
