Radiation image recording and read-out apparatus with sectored image recording capability

Stimulable phosphor sheets are circulated through an image recording section for recording radiation images on the stimulable phosphor sheets, an image read-out section for scanning the stimulable phosphor sheets with stimulating rays and detecting light emitted thereby upon stimulation, and an erasing section for releasing radiation energy remaining on the stimulable phosphor sheets. The image recording section is provided with a shutter which is selectively moveable between a standby position in which it permits radiation to reach the whole area of the stimulable phosphor sheet and a shielding position in which it shields a part of the stimulable phosphor sheet from the radiation. The means for conveying the stimulable phosphor sheet through the image recording section is provided with a control means for causing the stimulable phosphor sheet to be conveyed by sectors when the shutter is in the shielding position, whereby sectored image recording in which two or more radiation images are recorded on respective sectors of a single stimulable phosphor sheet can be carried out.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a radiation image recording and read-out 
apparatus for exposing stimulable phosphor sheets to a radiation passing 
through an object to have a radiation image of the object stored thereon, 
exposing the stimulable phosphor sheets to stimulating rays which cause 
them to emit light in proportion to the stored radiation energy, and 
detecting and converting the emitted light into electric signals. This 
invention particularly relates to such an apparatus in which the 
stimulable phosphor sheets are circulated and reused for recording images 
and more particularly to such an apparatus in which the circulated and 
reused stimulable phosphor sheets can be conveyed by sectors and subjected 
to sectored image recording in the radiation image recording section. 
2. Description of the Prior Art 
When certain kinds of phosphors are exposed to a radiation such as X-rays, 
.alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, 
they store a part of the energy of the radiation. Then, when the phosphor 
which has been exposed to the radiation is exposed to stimulating rays 
such as visible light, light is emitted from the phosphor in proportion to 
the stored energy of the radiation. A phosphor exhibiting such properties 
is referred to as a stimulable phosphor. 
As disclosed for example in Japanese Unexamined Patent Publication No. 
56(1981)-11395 and U.S. Pat. Nos. 4,258,264, 4,315,318, 4,387,428 and 
4,276,473, it has been proposed to use a stimulable phosphor in a 
radiation image recording and reproducing system. Specifically, a sheet 
comprising the stimulable phosphor is first exposed to a radiation passing 
through an object to have a radiation image stored thereon, and is then 
scanned with stimulating rays which cause it to emit light in proportion 
to the radiation energy stored. The light emitted from the stimulable 
phosphor sheet when the sheet is exposed to the stimulating rays is 
photoelectrically detected and converted to an electric image signal, 
which is processed as desired to reproduce a visible image having an 
improved quality, particularly a high diagnostic efficiency and accuracy. 
The finally obtained visible image may be reproduced in the form of a hard 
copy or may be displayed on a cathode ray tube (CRT). In this radiation 
image recording and reproducing system, the stimulable phosphor sheet is 
used to temporarily store the radiation image in order to reproduce the 
final visible image therefrom on a final recording medium. For economical 
reasons, therefore, it is desirable that the stimulable phosphor sheet be 
used repeatedly. 
Further, with regard to a mobile X-ray diagnostic station such as a 
traveling X-ray diagnostic station in the form of a vehicle like a bus 
which is provided with a radiation image recording and read-out apparatus 
for use in the aforesaid radiation image recording and reproducing system 
and moves from place to place to record radiation images for mass medical 
examinations, it is disadvantageous to load such a mobile X-ray diagnostic 
station with a large number of stimulable phosphor sheets, and the number 
of the stimulable phosphor sheets which can be loaded on the mobile X-ray 
diagnostic station is limited. Therefore, it is desired to load the mobile 
X-ray diagnostic station with stimulable phosphor sheets which can be used 
repeatedly, once store the radiation images of the objects on the 
stimulable phosphor sheets, transfer the electric image signals read out 
from the stimulable phosphor sheets to a recording medium having a large 
storage capacity, such as a magnetic tape, and circulate and reuse the 
stimulable phosphor sheets for further image recording and read-out 
operations, thereby to obtain the radiation image signals of many objects. 
Further, when image recording is conducted continuously by circulating and 
reusing the stimulable phosphor sheets, it becomes possible to increase 
the image recording speed in mass medical examinations. This is very 
advantageous in practical use. 
From the aforesaid viewpoint, the applicant proposed in U.S. patent 
application Ser. No. 037,119, which is a continuation of U.S. patent 
application Ser. No. 600,689 a radiation image recording and read-out 
apparatus comprising: 
(i) a circulating and conveying means for conveying at least one stimulable 
phosphor sheet for recording a radiation image thereon along a 
predetermined circulation path, 
(ii) an image recording section positioned on said circulation path for 
recording a radiation transmission image of an object on said stimulable 
phosphor sheet by exposing said stimulable phosphor sheet to a radiation 
passing through said object, 
(iii) an image read-out section positioned on said circulation path an 
provided with a stimulating ray source for emitting stimulating rays for 
scanning said stimulable phosphor sheet carrying said radiation image 
stored thereon in said image recording section, and a photoelectric 
read-out means for detecting light emitted from said stimulable phosphor 
sheet scanned with said stimulating rays to obtain an electric image 
signal, and 
(iv) an erasing section for, prior to the next image recording on said 
stimulable phosphor sheet for which the image read-out has been conducted 
in said image read-out section, releasing the radiation energy remaining 
on said stimulable phosphor sheet, 
whereby said stimulable phosphor sheet is circulated through said image 
recording section, said image read-out section and said erasing section 
and reused for radiation image recording. The erasing section in this 
apparatus can be arranged to carry out an erasing method as disclosed, for 
example, in Japanese Unexamined Patent Publication No. 56(1981)-12599 or 
U.S. Pat. No. 4,470,619. 
The radiation image recording and read-out apparatus of this construction 
meets the various aforesaid needs while also making it possible to carry 
out the radiation image recording and the reprocessing of the used 
stimulable phosphor sheets with very high efficiency. 
In radiography, however, there are occasions when it is desirable to be 
able to view and compare two images of the same object recorded under 
different conditions or by different methods. For example, it is 
frequently desirable to be able to compare front and side images of the 
same human body or to compare images of the same object recorded before 
and after the injection of a contrast medium. At such times it is 
convenient if the two images can be recorded on opposite halves of one and 
the same stimulable phosphor sheet. 
With the aforesaid radiation image recording and read-out apparatus it is 
possible to first record the two images to be compared on separate 
stimulable phosphor sheets and then to reproduce these images on a single 
photographic film, thus obtaining the same effect as when the two images 
are recorded on the same stimulable phosphor sheet. However from the point 
of reducing running costs by reducing the number of stimulable phosphor 
sheets required, and of shortening the processing time, it is preferable 
to be able to record the two images on opposite halves of the same 
stimulable phosphor sheet. 
The advantage of reduced running costs obtainable by recording plural 
images on the same sheet can of course be enjoyed not only when image 
pairs are recorded for comparison but in any case where two or more images 
are recorded on a single sheet. 
For recording two or even three or more images on different sectors of a 
single stimulable phosphor sheet (hereinafter referred to as sectored 
image recording) it is conceivable to use a method wherein the radiation 
field diaphragm is moved, a method wherein the radiation source is moved, 
or a method in which the sheet is moved and the size of the radiation 
field is reduced during sectored image recording without moving the 
radiation field diaphragm. Among these methods, the last mentioned is the 
best since it is the simplest to apply practically and does not require 
complex modifications in the structure of the radiation image recording 
and read-out apparatus. 
SUMMARY OF THE INVENTION 
One object of the present invention is to provide a radiation image 
recording and read-out apparatus which conducts radiation image recording 
and read-out by circulating the stimulable phosphor sheet. 
Another object of the present invention is to provide a radiation image 
recording and read-out apparatus which is capable of carrying out sectored 
image recording. 
The present invention provides a radiation image recording and read-out 
apparatus comprising a circulation and conveyance means for conveying 
stimulable phosphor sheets, an image recording section, an image read-out 
section, an erasing section, a shutter provided above said stimulable 
phosphor sheet in said image recording section and movable to a position 
for shielding a part of the stimulable phosphor sheet from radiation 
during sectored image recording, a shutter operating means for controlling 
the movement of said shutter, and a sectored image recording operation 
control means for, upon receipt of a sectored image recording command, 
moving the shutter to the shielding position and controlling said 
circulation and conveyance means so as to convey the stimulable phosphor 
sheet in said image recording section by sectors. The shutter is 
selectively moveable between the shielding position and a standby position 
in which it permits exposure of the whole stimulable phosphor sheet to 
radiation. It is made of a material having strong radiation shielding 
ability, e.g. lead, and is of a size large enough to cover at least half 
of the stimulable phosphor sheet. 
During sectored image recording, when two images are to be recorded on a 
single stimulable phosphor sheet the sheet is conveyed by sectors each 
equal to one-half of its overall size. Likewise, when three or more images 
are to be recorded thereon, it is conveyed by sectors each equal to 
corresponding fractions of its overall size. The operation of the shutter 
is matched to the sector-by-sector conveyance of the sheet in such manner 
that it is positioned to leave exposed only the sector of the sheet on 
which the image is to be recorded and to cover and shield from the 
radiation the remaining part thereof. For example, when the sheet is to be 
divided into three sectors each having a length in the direction of 
conveyance equal to one-third the overall length of the sheet, the shutter 
covers two-thirds thereof and leaves the remaining one-third uncovered. 
When sectored image recording is not being conducted and it is not 
necessary for the shutter to shield any part of the sheet from radiation, 
the shutter is retracted to the standby position to allow the entire area 
of the stimulable phosphor sheet to be exposed to the radiation. 
Aside from being able to record two or more images on equal sized sheet 
sectors as described in the foregoing, the apparatus according to this 
invention is also capable of recording two or more images on sheet sectors 
of unequal size. For example, the sheet can be divided into one sector 
equal to one-third its overall size and another sector equal to the 
remaining two-thirds. In this case, the shutter first shields two-thirds 
of the sheet while an image is recorded on the other third thereof and 
then shields the exposed third while an image is recorded on the remaining 
two-thirds thereof, or vice versa. 
In the foregoing description it is presumed that the field of the radiation 
covers the whole area of the stimulable phosphor sheet, and in such case 
it is necessary to provide a shutter at least as large as half the size of 
the sheet. If provision is made for stopping the radiation field down so 
that it covers less than the whole area of the sheet, however, it becomes 
possible to use a shutter that is smaller than half the size of the sheet. 
Namely, in such case the shutter need be only large enough to shield the 
part of each sector near its boundary with the neighboring sector during 
the recording of an image on the neighboring sector. 
Where the shutter is constituted of a plurality of shutter blades, there is 
no need for the blades to be all made from the same material, and where a 
single shutter is used, it is permissible for it to be made up of a 
plurality of interlinked shutter elements insofar as adequate shielding 
property is maintained at the joints between the elements. 
In accordance with this invention, since, in a system in which stimulable 
phosphor sheets are circulated and reused for recording and reading out 
radiation images, the sheets can be conveyed by sectors in the image 
recording section, it is possible, when desired, to carry out sectored 
image recording in which two or more images are recorded on each sheet. As 
a result, the efficiency of sheet utilization is enhanced and system 
running costs are reduced. Also, since two or more images can be recorded 
on a single sheet, pairs or groups of related images can be conveniently 
reproduced on a single photographic film or the like without need for 
carrying out any special operations in the read-out or reproduction steps.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will hereinbelow be described in further detail with 
reference to the accompanying drawings. 
FIG. 1 schematically shows the basic structure of an radiation image 
recording and read-out apparatus in accordance with the present invention, 
wherein a radiation image of the chest, abdomen or the like of a lying 
object is recorded. The main unit 1 of the apparatus is provided with a 
sheet circulation and conveyance means constituting an endless circulation 
path and comprising endless belts 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 and 
13, guide rollers 14, 15, 16, 17, 18, 19 and 20 rotated respectively by 
the endless belts 3, 4, 7, 10, 11, 12 and 13, guide plates 21, 22, 23, 24, 
25 and 26, and nip rollers 27 and 28. In the sheet circulation and 
conveyance system, by way of example, six stimulable phosphor sheets 30 
are conveyed and circulated in spaced relation to each other in the 
direction as indicated by the arrows. 
An image recording table 41 is positioned above the uppermost endless belt 
2 of the circulation and conveyance system and a radiation source 42, e.g. 
and X-ray source, is spaced from the image recording table 41 to stand 
face to face with the endless belt 2. An image recording section 40 is 
constituted by the image recording table 41 and the radiation source 42. A 
shutter 101 made of lead and having a size large enough to cover at least 
one-half the area of a sheet 30 is provided between the recording table 41 
and the radiation source 42. The shutter 101 is driven by a drive motor 
102 to move along a shutter guide 103 positioned parallel to the image 
recording table 41. 
In ordinary radiation image recording, the sheet 30 on which the image is 
to be recorded is positioned on the endless belt 2 as shown in the 
drawing, and the radiation source 42 is activated with the object lying on 
the image recording table 41. In this manner, the sheet 30 is exposed to 
X-rays passing through the object 43 to have a radiation image of the 
object 43 stored on the sheet 30. At this time, the shutter 101 is in a 
standby position at which it does not overlap any part of the sheet 30 and 
allows the whole area of the sheet 30 to be exposed to the X-rays. 
An image read-out section 50 is positioned at the right end of the sheet 
circulation and conveyance system. At the image read-out section 50, a 
laser beam source 51 is positioned above the endless belt 8 constituting a 
part of the image read-out section 50, and a mirror 53, a galvanometer 
mirror 54, and mirrors 55, 56 are positioned for scanning a laser beam 52 
emitted by the laser beam source 51 in the width direction of the sheet 30 
placed on the endless belt 8. The galvanometer mirror 54 is swung in both 
directions to scan the laser beam 52 in the main scanning direction on the 
sheet 30 carrying the radiation image stored thereon. The sheet 30 has 
been subjected to image recording at the image recording section 40 and 
then conveyed by the sheet circulation and conveyance system to the image 
read-out section 50. A light guiding reflection mirror 57 is positioned 
along the main scanning direction at the scanning portion of the laser 
beam 52 on the sheet 30. When the sheet 30 is exposed to the laser beam 
52, the sheet 30 emits light in proportion to the stored radiation energy. 
The light emitted by the sheet 30 directly towards a light guide member 58 
and the light emitted thereby and reflected by the light guiding 
reflection mirror 57 enters the light guide member 58 from a light input 
face 58A thereof, and is guided inside of the light guide member 58 
through total reflection to a light output face 58B thereof. The light is 
thus detected by a photomultiplier 59 connected to the light output face 
58B of the light guide member 58. Simultaneously with the scanning of the 
sheet 30 by the laser beam 52 in the main scanning direction, the sheet 30 
is moved by the endless belt 8 in the subscanning direction as indicated 
by the arrow approximately normal to the main scanning direction, so that 
the whole surface of the sheet 30 is scanned by the laser beam 52. An 
electric image signal obtained by the photomultiplier 59 is sent to an 
image processing circuit (not shown) for processing the electric image 
signal. The image signal thus processed is then sent to an image 
reproducing apparatus (not shown). The image reproducing apparatus may be 
a display device such as a CRT, or a device for recording a visible image 
by point-by-point scanning on a photographic film. Or, the image may be 
stored on a storage means such as a magnetic tape. 
In general, the time required for reading out a radiation image from one 
sheet 30 is longer than the time taken for recording the radiation image 
on the sheet 30. However, it is possible to quickly finish image recording 
on a plurality of sheets 30 and leave the exposed sheets 30 resting one 
each on the endless belts 7, 6, 5, 4 and 2 prior to read-out. Also, for 
example, Japanese Unexamined Patent Publication No. 58(1983)-89245 
discloses a method wherein a read-out operation for detecting the image 
input information of a radiation image stored on a stimulable phosphor 
sheet (hereinafter referred to as the preliminary read-out) is conducted 
in advance by use of stimulating rays having stimulation energy of a level 
lower than that of the stimulation energy of stimulating rays used in a 
read-out operation for obtaining a visible image for viewing, particularly 
for diagnostic purposes (hereinafter referred to as the final read-out), 
and thereafter the final read-out gain is adjusted and/or appropriate 
signal processing is conducted to obtain a visible image having an 
improved image quality, particularly a high diagnostic efficiency and 
accuracy regardless of radiation exposure conditions. In the apparatus of 
the present invention, too, it is possible to conduct the preliminary 
read-out and the final read-out by returning the sheet 30, which has been 
sent onto the endless belt 9 after once being read out (the preliminary 
read-out), back to the image read-out position for a second read-out (the 
final read-out) by reversely rotating the endless belts 7, 8 and 9. 
After image read-out is finished, the sheet 30 is conveyed by the endless 
belt 9 to an erasing section 70 comprising a case 71 and many erasing 
light sources 72, e.g. tungsten, sodium, xenon or iodine lamps, arranged 
within the case 71. After a shutter 73 is opened, the sheet 30 is conveyed 
by the endless belt 9 until the leading end of the sheet 30 contacts the 
nip rollers 27. The sheet 30 is thus sent into the case 71 by the rotating 
nip rollers 27. Then the shutter 73 is closed, and the erasing light 
sources 72 are turned on. The erasing light sources 72 mainly emit light 
having a wavelength within the stimulation wavelength range for the 
stimulable phosphor of the sheet 30. When the sheet 30 is exposed to the 
erasing light, the radiation energy remaining in the sheet 30 after the 
image read-out is released. At this time, since the shutter 73 is closed, 
no noise is generated in the read-out signal by erasing light leaking into 
the image read-out section 50. 
After the radiation energy remaining on the sheet 30 is erased to such an 
extent that the next image recording on the sheet 30 is possible, the nip 
rollers 28 are rotated and the sheet 30 is conveyed out of the erasing 
section 70. Then, the sheet 30 is conveyed by the endless belts 10, 11, 12 
and 13 onto the endless belt 2 at the image recording section 40. At this 
time, if a different sheet 30 is present on the endless belt 2 at the 
image recording section 40, the sheet 30 conveyed by the endless belts 10, 
11 and 12 is kept waiting on the endless belt 13, and subsequent sheets 30 
are kept waiting on the endless belts 12, 11 and 10. When the image 
recording and read-out operations are finished, the last sheet 30 is 
subjected to erasing at the erasing section 70, moved back onto the 
endless belt 9 by reverse rotation of the nip rollers 27, and kept waiting 
on the endless belt 9. 
As described above, the endless belts 2 to 13 and nip rollers 27 and 28 of 
the sheet circulation and conveyance system are controlled in relation to 
the image recording section 40, the image read-out section 50 and the 
erasing section 70 by a known sequence control method or the like, thereby 
conveying or keeping the sheet waiting. 
As mentioned earlier, there are times when it is desirable to be able to 
record two or more images of the same object 43 on different sectors of a 
single sheet 30. Such sectored image recording can be realized by an 
arrangement such as that shown in FIG. 2. More specifically, instructions 
for carrying out sectored image recording, for example instructions for 
the recording of two images on respective halves of a sheet 30, are 
entered via an external controller 90 which then transmits a corresponding 
command to the main unit 1 of the radiation image recording and read-out 
apparatus and through the main unit 1 also to the radiation source 42. As 
a result, the sheet 30 is conveyed by half lengths so that each of two 
sectors thereof can be separately exposed to the radiation from the 
radiation source 42. At this time, the drive motor 102 moves the shutter 
101 along the shutter guide 103 prior to each exposure and stops it so as 
to cover the sector of the sheet 30 not being exposed while leaving the 
other sector uncovered. 
The controller 90 can be provided in a separate operating room as shown in 
FIG. 2 or can be mounted on one end of the main unit 1 as shown in FIG. 1. 
In either case it is provided with a pair of buttons 80, 81 by which the 
operator can set the position of the shutter 101. Namely, when the button 
80 is pushed, the shutter 101 is moved along the shutter guide 103 from 
the standby position to the shielding position making it possible to 
conduct sectored image recording, and when the button 81 is pushed, the 
shutter 101 is moved from the shielding position back to the standby 
position making it possible to conduct ordinary image recording. The 
buttons 80, 81, the drive motor 102 and the shutter guide 103 together 
constitute the operating means for the shutter 101. 
Control of the conveyance of the sheet 30 in sectored image recording will 
now be explained in detail with reference to FIGS. 4A, 4B and 5. 
FIGS. 4A, 4B and 5 illustrate an example in which the positions at which 
the sheet 30 is stopped during its conveyance by the endless belt 2 are 
controlled using two sensor pairs 2A and 2B. In this example the shutter 
101 consists of two shutter blades 101A, 101B and when the sectored image 
recording mode of operation is designated through the controller 90, the 
shutter blades 101A, 101B move to positions at which they shield one half 
of the sheet 30 and define an image recording sector A therebetween. At 
the same time, the sheet 30 fed onto the endless belt 2 is advanced until 
its leading end 30A is detected by the sensors 2A positioned at the 
forward end of the image recording sector A and is stopped in this 
position (FIG. 4A). The radiation source 42 is then activated to record an 
image on the forward (first) sector of the sheet 30. Next, the endless 
belt 2 is driven and the sheet 30 is advanced until its trailing end 30B 
is detected by the sensors 2B positioned at the rearward end of the image 
recording sector A and is stopped at this position (FIG. 4B). The 
radiation source 42 is then activated to record an image on the rearward 
sector of the sheet 30. After recording of the image on the rearward 
(second) sector has been completed, the sheet 30 is discharged from the 
image recording section 40 and is conveyed to the next processing step. 
An example in which the two sensor pairs 2A, 2B are replaced by a single 
sensor pair 2C will now be explained with reference to FIGS. 6A-6D and 
FIG. 7. 
In this example, the sensors 2C are positioned ahead of the image recording 
sector A and the endless belt 2 is stopped after the lapse of a first 
prescribe time period from the time that the leading end 30A of the sheet 
30 is detected by the sensors 2C at the position shown in FIG. 6A. As the 
first prescribed time period is the same as the time required for the 
leading end 30A of the sheet 30 to move from the position of the sensors 
2C to the forward end A1 of the image recording sector A, the sheet 30 is 
properly located for recording of an image on its forward (first) sector 
after the lapse of this time (FIG. 6B). After recording of the image on 
the first sector is completed, the endless belt is again driven and kept 
in operation until a second prescribed time has lapsed from the time that 
the trailing end 30B of the sheet 30 is detected by the sensors 2C at the 
position shown in FIG. 6C. As the second prescribed time period is the 
same as the time required for the trailing end 30B of the sheet 30 to move 
from the position of the sensors 2C to the rearward end B1 of the second 
image recording sector A, the sheet 30 is properly located for recording 
of an image on its rearward (second) sector after the lapse of this time 
(FIG. 6D). After recording of the image on the second sector is completed, 
the sheet 30 is conveyed to the next processing step. 
While the two examples described in the foregoing both relate to sectored 
image recording in which the sheet 30 is divided into two sectors, 
recording in which the sheet 30 is divided into three or more sectors can 
also be carried out in a similar manner.