Lighttight envelope for high-speed conveyance of stimulable phosphor sheet

A lighttight envelope for housing a stimulable phosphor sheet therein is fabricated of a flexible light shielding material and has a size sufficient to house the stimulable phosphor sheet therein. The lighttight envelope comprises an upper sheet and a lower sheet closely contacted with each other at least at one side and open at least at one side opposite to the closely contacted side and at portions of two sides adjacent the ends of the opposite side up to such positions that access to a part of the stimulable phosphor sheet housed in the lighttight envelope is allowed, thereby forming a wide inlet for the stimulable phosphor sheet. A small face-to-face fastener is positioned at a part of the opposite side.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a lighttight envelope used when a stimulable 
phosphor sheet used in a radiation image recording and reproducing system 
for recording a radiation image in the stimulable phosphor sheet and then 
reproducing a visible image therefrom is conveyed in a high-speed image 
recording apparatus. This invention particularly relates to a lighttight 
envelope for high-speed conveyance of the stimulable phosphor sheet, which 
has a configuration for improving the operating efficiency in handling of 
the stimulable phosphor sheet. 
2. Description of the Prior Art 
High-speed image recording apparatuses have heretofore been used for 
angiography and the like. The high-speed image recording apparatuses 
record X-ray images of objects on many X-ray films by sequentially 
projecting the X-ray images onto the X-ray films. The apparatuses are 
suitable particularly for sequentially recording angiograms, which change 
from time to time, on many X-ray films when the diffusion speed of the 
contrast media is different among the objects. 
In the high-speed image recording apparatuses, the X-ray film is used in 
the form sandwiched, for example, between two intensifying screens and 
housed in a flexible lighttight envelope. 
The high-speed image recording apparatus using a lighttight envelope in 
which an X-ray film is housed comprises a first film receiving section for 
receiving the unexposed lighttight envelopes, a conveyance mechanism for 
sequentially conveying the lighttight envelopes at high speeds from the 
first film receiving section to an image recording position where the 
X-ray films are exposed to X-rays passing through an object, and for 
sequentially conveying the exposed lighttight envelopes at high speeds 
from the image recording position, and a second film receiving section for 
receiving the exposed lighttight envelopes which are conveyed at high 
speeds from the image recording position. The object is positioned on the 
high-speed image recording apparatus. 
The lighttight envelope used in the high-speed image recording apparatus 
constituted as described above has a configuration for sufficiently 
shielding the X-ray film from light. FIG. 1A is a perspective view showing 
an example of the lighttight envelope employed in the conventional 
high-speed image recording apparatus using an X-ray film, and FIG. 1B is a 
perspective view showing the lighttight envelope of FIG. 1A with the inlet 
opened. Sufficiently lighttight, black plastic sheets 2A and 2B are 
heat-sealed at their sides 20, 21 and 22 to form an envelope open at one 
side. The open side of the plastic sheet 2A continues into an opening edge 
portion 2a, and the open side of the plastic sheet 2B continues into an 
opening edge portion 2b. A face-to-face fastener 2c consisting of a tape 
provided with many fine hook-like fibers and a tape provided with many 
fine loop-like fibers is positioned so that the tapes extend on the inner 
surfaces of the opening edge portions 2a and 2b over the entire lengths 
thereof. The opening edge portions 2a and 2b are lighttightly engaged with 
each other by the face-to-face fastener 2c. As indicated by a chain line 
in FIG. 1A, an X-ray film 25 sandwiched between a pair of intensifying 
screens (not shown) is housed inside of the sealed sides 20, 21 and 22 and 
the face-to-face fastener 2c. Thus the X-ray film 25 is handled and 
conveyed in a condition sufficiently shielded from light. 
The conventional lighttight envelope as described above houses the X-ray 
film 25 in the sufficiently lighttight condition and is loaded into the 
high-speed image recording apparatus. However, since the face-to-face 
fastener 2c positioned at the opening edge portions 2a and 2b for securing 
sufficient lighttightness strongly closes the opening through which the 
X-ray film 25 is inserted into and removed from the lighttight envelope 
and since the area of the opening is small, insertion and removal of the 
X-ray film 25 are not easy to conduct. 
Recently, a radiation image recording and reproducing system using a 
stimulable phosphor as described below has been proposed. 
When certain kinds of phosphors are exposed to a radiation such as X-rays, 
.alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultra-violet 
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 by the phosphor in proportion 
to the stored energy of the radiation. A phosphor exhibitinhg such 
properties is referred to as a stimulable phosphor. 
As disclosed in U.S. Pat. No. 4,258,264 and Japanese Unexamined patent 
publication No. 56(1981)-11395, it has been proposed to use a stimulable 
phosphor in a radiation image recording and reproducing system. 
Specifically, a sheet provided with a layer of the stimulable phosphor 
(hereinafter referred to as a stimulable phosphor sheet) is first exposed 
to a radiation passing through an object to have a radiation image stored 
therein, and is then scanned with stimulating rays such as a laser beam 
which cause it to emit light in the pattern of the stored image. The light 
emitted by the stimulable phosphor sheet upon stimulation thereof is 
photoelectrically detected and converted to an electric image signal, 
which is processed as desired to reproduce a visible image on a recording 
medium such as photographic film or on a display device such as a cathode 
ray tube (CRT). 
This radiation image recording and reproducing system using the stimulable 
phosphor sheet is advantageous over conventional radiography using an 
X-ray film and intersifying screens in that the radiation image can be 
recorded over a very wide range (latitude) of radiation exposure and 
further in that the electric signal used for reproducing the visible image 
can be freely processed to improve the image quality for viewing, 
particularly for diagnostic purposes. In more detail, since the amount of 
light emitted upon stimulation after the radiation energy is stored in the 
phosphor varies over a very wide range in proportion to the amount of 
energy stored therein, it is possible to obtain an image having desired 
density regardless of the amount of exposure of the phosphor to the 
radiation by reading out the emitted light with an appropriate read-out 
gain and converting it to an electric signal to reproduce a visible image 
on a recording medium or a display device. The electric signal may further 
be processed as desired to obtain a radiation image suitable for viewing, 
particularly for diagnostic purposes. This is very advantageous in 
practical use. 
Also in the aforesaid radiation image recording and reproducing system 
using the stimulable phosphor sheet, if such a high-speed image recording 
apparatus as used in the conventional radiography could be employed, it 
would become possible to quickly record many radiation images having an 
improved image quality, particularly a high diagnostic efficiency and 
accuracy. This would be very advantageous for medical diagnosis. 
As mentioned above, the high-speed image recording apparatus is suitable 
particularly for angiography. Therefore, if the high-speed image recording 
apparatus could be employed for the radiation image recording and 
reproducing system using the stimulable phosphor sheet, it would become 
possible to further improve the diagnostic efficiency and accuracy of 
angiograms. This would be very advantageous for medical diagnosis. 
Accordingly, it is desired to use the aforesaid lighttight envelope for the 
X-ray film in the high-speed image recording apparatus employed for the 
radiation image recording and reproducing system, and to load the 
stimulable phosphor sheet into the high-speed image recording apparatus in 
the form housed in the lighttight envelope. 
However, the aforesaid lighttight envelope is not convenient for inserting 
the stimulable phosphor sheet thereinto and removing it therefrom at a 
high operating efficiency. Further, in the radiation image recording and 
reproducing system using the stimulable phosphor sheet, the stimulable 
phosphor sheet need not be shielded from light before an X-ray image is 
recorded thereon. Also, the required degree of light shielding for the 
stimulable phosphor sheet after an X-ray image is recorded thereon is far 
lower than the degree of light shielding required for the X-ray film. 
Therefore, it is not advantageous from the viewpoint of operating 
efficiency to employ the conventional lighttight envelope for the X-ray 
film directly as a lighttight envelope for the stimulable phosphor sheet. 
In view of the aforesaid feature of the radiation image recording and 
reproducing system using the stimulable phosphor sheet, a need exists for 
a lighttight envelope for high-speed conveyance of the stimulable phosphor 
sheet, which exhibits a comparatively simple light shielding function and 
which has a configuration facilitating insertion and removal of the 
stimulable phosphor sheet. 
SUMMARY OF THE INVENTION 
The primary object of the present invention is to provide a lighttight 
envelope which has a comparatively simple light shielding function, and 
which enables easy insertion and removal of a stimulable phosphor sheet. 
Another object of the present invention is to provide a lighttight envelope 
which is suitable for use in the high-speed image recording apparatus. 
The present invention provides a lighttight envelope for high-speed 
conveyance of a stimulable phosphor sheet, which is fabricated of a 
flexible light shielding material and has a size sufficient to house the 
stimulable phosphor sheet therein, 
the lighttight envelope comprising: 
(i) an upper sheet and a lower sheet having approximately identical 
rectangular shapes, said upper sheet and said lower sheet being closely 
contacted with each other at least at one side thereof and open at least 
at one side opposite to said closely contacted side and at portions of two 
sides adjacent the ends of said opposite side up to such positions that 
access to a part of the stimulable phosphor sheet housed in the lighttight 
envelope is allowed, and 
(ii) a means for preventing said upper sheet and said lower sheet from 
separating from each other, said means being positioned at a part of said 
opposite side. 
The term "close contact" also embraces the case where the upper sheet and 
the lower sheet are joined together by folding. 
As the means for preventing the upper sheet and the lower sheet from 
separating from each other, any means may be employed insofar as the upper 
sheet and the lower sheet can be easily engaged releasably with each other 
and prevented from naturally separating from each other. 
In the lighttight envelope of the present invention, since the envelope has 
a wide opening, it is easy to insert a stimulable phosphor sheet into the 
envelope and to remove the stimulable phosphor sheet therefrom. Further, 
since the envelope exhibits lighttightness to a reasonable extent, it can 
be directly used in the high-speed image recording apparatus. The 
lighttight envelope also has the effect of protecting the surface of the 
stimulable phosphor sheet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will hereinbelow be described in further detail with 
reference to the accompanying drawings. 
FIG. 2 is a view of an embodiment of the lighttight envelope in accordance 
with the present invention with the inlet closed, and FIG. 3 is a view 
thereof with the inlet opened. The lighttight envelope comprises an upper 
sheet 1A and a lower sheet 1B made of a flexible light-shielding material 
and having approximately identical rectangular shapes. The upper sheet 1A 
and the lower sheet 1B are heat-sealed together at one side 10 and at 
portions 11a and 12a of sides 11 and 12 adjacent the side 10. A side 13 
opposite to the side 10 is left open. Also, a portion 11b of the side 11 
and a portion 12b of the side 12, which are adjacent the opposite side 13, 
are left open from said opposite side 13 up to such positions that access 
to a part of the stimulable phosphor sheet housed in the lighttight 
envelope is allowed. A face 13A provided with many fine hook-like fibers 
is positioned on the inner surface of the upper sheet 1A at the opened 
side 13. A face 13B provided with many fine loop-like fibers is positioned 
on the inner surface of the lower sheet 1B at the open side 13. The faces 
13A and 13B together constitute a face-to-face fastener for releasably 
closing the upper sheet 1A and the lower sheet 1B at the open side 13. 
Further, the inner surface of the lower sheet 1B at the open side 13 is 
provided with a flap 13C facing inward for contracting or engaging with 
the stimulable phosphor sheet housed in the lighttight envelope, thereby 
securely preventing the stimulable phosphor sheet from coming out of the 
lighttight envelope. 
The lighttight envelope is provided with an identification number 
indicating section 14 made of lead or a material impermeable or 
semi-impermeable to X-rays for indicating an image identification number. 
Therefore, the identification number can be recorded on the stimulable 
phosphor sheet simultaneously with recording of an X-ray image. 
FIGS. 4A, 4B, and 4C show further embodiments of the lighttight envelope in 
accordance with the present invention. 
In the embodiment of FIG. 4A, one of the two sides corresponding to sides 
11 and 12 in the embodiment of FIGS 2 and 3 is open over the entire 
length, and a plastic fastener 15 is positioned at the completely open 
side. In this embodiment, since two sides of the lighttight envelope can 
be opened widely, insertion and removal of a stimulable phosphor sheet 30 
are easier than in the embodiment of FIGS. 2 and 3. In the embodiment of 
FIG. 4A, a face-to-face fastener 16 for releasably engaging the upper 
sheet and the lower sheets with each other should preferably be positioned 
near the side provided with the plastic fastener 15. The lighttight 
envelope is heat-sealed at portions 17A and 17B. 
In FIG. 4B, the lighttight envelope is heat-sealed only at a side 18B, and 
plastic fasteners 18A, 18A are positioned at the two sides adjacent the 
heat-sealed side 18B. In this embodiment, since the three sides other than 
the sealed side 18B can be opened completely, insertion and removal of the 
stimulable phosphor sheet becomes further easier. A face-to-face fastener 
19 for releasably engaging the upper sheet and the lower sheet with each 
other is positioned at the center of the open side opposite to the sealed 
side 18B. 
In the embodiment of FIG. 4C, the plastic fastener 15 in the embodiment of 
FIG. 4A is omitted. In this embodiment, though the degree of sealing 
becomes somewhat low, it is easy to open and close the lighttight envelope 
and to insert and remove the stimulable phosphor sheet 30. A face-to-face 
fastener 16A is positioned closer to the corner of the lighttight envelope 
than in the embodiment of FIG. 4A so that the stimulable phosphor sheet 30 
does not come out of the lighttight envelope. 
In the aforesaid embodiments of the lighttight envelope, plastic fasteners 
for fastening by engagement between protruded ribs and grooves are used 
for preventing the upper sheet and the lower sheet from disengaging. 
Instead of using the plastic fasteners, it is also possible to use 
ordinary bite type fasteners, simple hooks, or the face-to-face fasteners 
as described above. 
The lighttight envelope of the present invention can be conveyed at high 
speeds in the high-speed image recording apparatus by being releasably 
secured to the conveyor belt. For this purpose, as shown in FIG. 3B, faces 
24, 24 of a face-to-face fastener provided with hook-like fibers or 
loop-like fibers may be positioned on the outer surface of the lower sheet 
1B of the lighttight envelope, and the other faces of the face-to-face 
fastener for engagement with the faces 24, 24 may be positioned on the 
conveyor belt. Or, the lighttight envelope may be conveyed by being 
sandwiched between two belts.