Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to an apparatus which is in-
tended to be brought into a field of radioactive radiation or
X ray radiation emergent from a source of such radiati.on, there
being used a rotatable driven body comprising a radiation-
absorbing material and having portions which are pervious to
said radiation~ :~
Such apparatus may have medicinal, security or industrial use, `~
and resemble f.~ying-spot systems, normally using mechanical
deflection of scanner beams, and in the majority of cases using
a collimator to obtain a narrow beam that is transmitted at
right angles to a rotating disc provided with elongate apertures ,
e~tending radially from the periphery of the disc. Because it
is difficult to produce well defined beams that will move as
well defined points across the object being scanned, the resul-
tant image becomes diffused and the use of such apparatus has ~ .
therefore, to a large extent, been limited to simple examina- `
tions, such as for the security examination of baggage at air
terminals or the like. Another problem encountered with said
known apparatus is that the need for high beam-energy levels
makes it necessary to use a thick rotary disc, in order to .
obtain the desired shielding efect in the intervals between
the slots. In turn, this means that
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the beams are unable to pass obliquely through the slot and there-
with only a very small part of the pa-th along which a slot travels
can be used, i.e. the scan path is extremely limited. Neither
can such known apparatus having open slots extending from the
periphery of the disc towards the center thereof be used to de-
tect along sweep-lines a body radiating radioactive radiation, for
example a human skull in which a radioac~ive substance has been
planted to ascertain, for example, the presence or absence of
a tumour. The main object of the invention is therefore to pro-
vide an improved apparatus for transmitting a highly concentratedspot radiation onto an object to be scanned and for forming from
radiation from an object a flying spot which is detected by a
dectector and which pr~vides an image of any inhomogenity in the
object.
According to the invention, there is provided an appa-
ratus brought into a field of radioactive radiation or X-radia-
tion immergent from a radiation source for sensing an object,
the apparatus comprising a housing formed of radiation impervious
material, at least one opening in the housing through which rad-
iation may pass, a chamber in the housing, conducting means inthe housing for conducting radiation between the opening and
the chamber, the conductiny means comprising a the solid
body surrounding the chamber and including a plurality of cir-
cumferentially spaced channels extending between ~he chamber and
an outer surface of the body to conduct radiation in the form . ~ .
of narrow beams to a detector which detects the radiation and
yenerates a signal corresponding to the intensity thereof, the
body including at least two parts secured together such that
inner faces of the parts are in axially facing rPlat:ionship,
with the channels comprising radial grooves arranged on the in-
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ner face of at least one of the parts, and drive means for driv-
: ing ~he body around an axis of rotation.
When the ob~ect is to be sensed, the source of radia- ;~
tion is arranged in the central chamber and the detector arrang-
ed adjacen the object, while when the object constitutes or
incorporates the radiation source, the detector is arranged in
the chamberO
Preferred embodiments of the invention will now be
described with reference to the drawings, in which~
Figure 1 is a simplified schematic perspective view
of one exemplary embodiment of the invention;
Figure 2 schematically illustrates the interior of
the embodiment -
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shown in Figure l;
FicJure 3 is a detailed sectional view of the disc employed in
the embodiment shown in Figure l;
Figure 4 shows one half of the disc shown in Figure 3; and,
Figure 5 is a block diagram of a further application of the
invention.
In Figure 1 there is shown a disc l mounted on a shaf~ 2 that is
driven b~ means of a motor (18 in Figure 2). As will be des- ~ ;
cribed hereinafter in more detail, the disc l has radially exten-
ding channels, and a source of radiation such as an X-ray source
or radio-active charge is arranged at the centre of the disc so
that well defined beams are sequentially directed onto an object
3 to be examined, of which a beam 4 is indicated by means of a
broken line. The object 3 is conveyed on a conveyor 5 extending
substantially parallel to the shaft 2 and moving past the disc l~
preferably at a constant speed. Each beam 4 exiting from the disc
(l)wîll scan the object 3 along a path 4' as indicated in Figure
l. The object 3 is assumed to be normally pervious to the beam,
so that after it has been penetrated by said beam, the beam éxi-
ting from the object will be incident upon an elon~ate detector6 arranged in the plane defined by the beam movement. During
passages through the object 3, the beam will be partially ab-
sorbed, but if an inhomogeneity such as a metal object, a knot in
a piece of wood; a stone or some other object whose density dif-
fers to that of the overall density of the object 3 is encountered
by the beam, there ~ill be a marked change in the emergent beam
amplitude. The electric signals generated by the detector 6 are
thus dependent upon the material through which the beam passes
at any instant, and upon the initial intensity and energy of the
incident beam. When the beam moves from the upper end of the de-
tector down towards the lower end thereof, with the direction of
rotation assumed herein, the number of pulses generated by the
detector 6 will be dependent upon the intensity of the received
beam. The beam detector 6 comprises for example, a scintillation
spectrometer. During each scan, the electric signals from the l ;
detector 6 reproduce the course of the intensity distribution re-
sulting from passage through the object. The output signals
from the detector 6 can, for example, be supplied to an analyser ;
7, su¢h as data processing apparatus or some other suitable unit. -~
Instead of one detector, a plurality of detectors 6 may be
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arranged sequentially in one and the same plane, i.e., the sweep
plane, or said detectors may be arranged in planes lying paral-
lel with said sweep plane. In this latter case, the different
detector portions are impinged upon by different portions of a
broader beam or of several beams emergent from respective,
separate channels arranged in the discs for each beam.
In order to provide a well-defined, narrow beam, the scanning
disc 1 is constructed in the manner shown in Figures 2 to 4.
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Figure 2 shows the disc 1 on -the shaft 2 which is journalled in
two bearings 8 and 9. These bearings 8 and 9 are attached to a
wall 12 by means of bolts 10 and 11, said wall forming part of a -
housing indicated by a broken line 13. This housing is made of
lead or some other suitable material preventing radiation leakage
to the surroundings, and has an opening 14 in the wall 12, through
which radiation from the periphery of the disc 1 passes out to-
wards the detec~or 6. Moun~ed on the shaft 2 that carries the
disc 1 is a belt pulley 15, via which the disc 1 is driven by a
bel~ 16 engaging a further belt pulley 17 that is mounted on the
shaft of an electric motor 18. Other drive arrangements can be
used. The disc 1 is provided with internal channels extending
radially from the periphery of the disc 1 to a central chamber
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19 that is accessible through a hollow shaft portion (Figure 3)
and in which there is a source 20 of radiation. Two diametrically
opposed channels 21 and 22 are shown in Figure 3. As will also
be seen from Figure 3, the disc 1 comprises two halves 23 and 24.
Figure 4 shows one full face of the disc-half 24. Arranged in
this face are grooves 25 to 40 which extend from the periphery 41
of the disc to a central recess 42, forming part of the chamber lg
for accommodating the radiation-source 20. ~he radiation-source
is placed in register with the channels formed when the planar,
10 inner face of the other disc-half 23 is brought into contact with ;~
~ the disc-half 24 to cover the grooves 25 to 40. The disc-halves, ; ;~
; which are manufactured from a material capable of absorbing radia-
tion, such as steel, are bolted securely together, as shown by
bolt 43 (Figure 3). Figure 4 shows bolt-holes 44 and 45.
Although from the aspect of manufacture it is preferred to provide
grooves only in one disc-half, it is naturally possible to pro-
vide cooperating grooves in the two disc-halves. It is also
possible for the disc 1 to be a one-piece structure in which ra-
dial channels are formed by bores each extending from the peri-
2~0 phery to the central chamber accommodating the source of radiation.
In order to obtain a high degree of sensitivity, it is important
to obtain good shielding in the intervals between the channels,
i.e., to obtainas little background noise as possible, and in
addition, a good fit between the mutually opposed surfaces is de-
sirable in the case of a disc comprising two disc-halves, to avoid
leakage of radiation.
The grooves are shown as being of uniform width, but in some em-
bodiments each groove is of increasing cross-sectional area from
the source of radiation outwardly towards the periphery of the
disc. Irrespective of the form of the grooves, the exiting
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radiation forms respective narrow beams whose geometry is con-
stant irrespective of the beam energy.
In the illustrated embodiment the shaft 2 is driven to rotate the
body 1, but it is also possible to use a stationary shaft, on
which the disc rotates. An important advantage obtained with the
described hollow shaft is that the radio-active source 20 can be
stored in a stationary position relative to the shaft, being
carried by a holder extending into the shaft (not shown).
As will readily be perceived, the disc surrounding the radiation
source 20 need not be of circular shape, but can be a plate of
any shape whatsoever, although a rotationally symmetrical shape
is to be preferred if it is to rotate at a high speed.
In the illustrated embodiment, the object to be examined is moved
and the detector and radiation apparatus are stationary, but it
will be understood that a detector and associated radiation appa-
ratus may be moved past a stationary object.
Figure 5 is a schematic view of apparatus for detecting radiation
R lmmergent from an object 3'. The object 3' may be a hospital
patient into whose blood a radio-active substance has been in-
jected, a radio-active machine component, a container holding
radio-active material or an object which is irradiated from the
rear, it being assumed that said object can be moved on the con-
veyor (not shown) as with the Figure 1 embodiment and is moved
in the direction of the arrow A.
The object may be arranged so that it can be rotated whilst being
conveyed by said conveyor or to be rotated whilst stationary.
An apparatus of the type aforedescrlbed is arranged in the path
of radiation and a detector (not shown) is arranged in the cent-
ral chamber 19' of the disc l~o When the disc 1' rotates and the
30 - object 31 is moved in the direction of arrow A, a well defined
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beam will pass through respective channels in the disc 1' and
impinge upon the detector, the position of said beam changing ~:
along sweep lines which cover the body 3~' to a higher or lower
degree of denseness. Thus, the detector arranged in the space
19' will generate at each moment of time an output signal re-
presentiny a value of the intensity of the radiation of that
locality on the object which at that moment of time is observed
by a channel. This signal is transmitted to an indicating de-
vice 7' via a conductor 46.
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