WO2000035347A1

WO2000035347A1 - A digital bucky device

Info

Publication number: WO2000035347A1
Application number: PCT/SE1999/002367
Authority: WO
Inventors: Carl-Eric Ohlson
Original assignee: Ao Medical Products Ab
Priority date: 1998-12-16
Filing date: 1999-12-15
Publication date: 2000-06-22
Also published as: AU3090900A; SE9804351D0; SE9804351L; SE512202C2

Abstract

An X-ray radiographic system (1) includes a digital bucky that has a fixed or a movable raster. The bucky is comprised of a rectangular box (2) which houses an image receptor (3) in the form or a digital detector that is connected electrically, magnetically or optically to an image presentation unit in the form of a computer (5) and associated screen (5a). The upper part of the box (2) includes an ion-chamber in addition to the raster. The detector (3) can be withdrawn from the box to enable free exposures of smaller objects (10) to be taken. In this respect, the radiation source is arranged so that it can be focused on the detector (3) in its withdrawn position. The box and the detector are also provided with a latching device (2b, 3c) which releaseably blocks the box in the withdrawn position of the detector, and damping means are also provided for taking-up any impact forces to which the detector may be subjected.

Description

A DIGITAL BUCKY DEVICE

Background of the invention

X-ray radiograms are generally exposed with the aid of radiogram cassettes of different standard sizes ranging from 18 x 24 to 35 x 43 cm.

Image impairing stray radiation will occur when exposing objects that are larger than a hand or a foot for instance. This stray radiation is absorbed with the aid of lead- lamellae rasters. The raster consists of thin lamellae, preferably lead lamellae, which are orientated parallel with the direction of the radiation.

A bucky is a box that accommodates existing standard size film cassettes in their length and cross directions. The bucky also includes a raster, which is often moved during the exposure period, so as not to be imaged on the film, and also includes a so-called ion chamber for measuring the radiation dosage and regulating the correct exposure time.

The raster creates certain drawbacks. The most serious of these resides in a substantial increase in the X-ray dosage by a factor of 4, and also an increase in the object-film- distance. This latter drawback can be compensated for by proportionally increasing the film-radiation source (focus) -distance, which in turn causes a further increase in the radiation dosage. Although the ion chamber does not affect the radiation dosage, the object-film-distance does.

Digital imaging technology has progressively increased in recent years. In this regard, the use of image receptors will probably replace film technology completely in time, and exists in the form of digital image plates and digital detectors. There are some technical differences between image plates and digital detectors, insomuch that the image plates have corresponding standard sizes so as to be able to replace film cassettes in existing equipment, for instance in a bucky, whereas the detectors are available in only a few fixed sizes and, distinct from the image plates, are normally fixedly connected by cables to the imaging equipment.

As in the case of film cassettes, it is necessary to move the image plates to the X-ray equipment for exposure and from there to the scanning unit used for image production, this procedure being both unergonomic and laborious.

This drawback is avoided when the detectors are fixedly mounted in a digital bucky. However, the large format based on the largest format of the image plate/cassette and the raster prevents so-called free exposures from being carried out.

Free exposures have hitherto been performed on small objects, such hands, feet, elbows, knees, etc., with loose film cassettes or image plates and in the absence of rasters, which do not generate image impairing stray radiation. Because the object can be placed directly on the image field, optimal image quality is achieved with a low radiation dosage.

Field of the invention

The present invention relates to a digital bucky that has a fixed or movable raster, and more particularly to a digital bucky of the kind defined in the preamble of Claim 1. A digital bucky of this kind can be partially adapted for free exposures, by moving the raster away, i.e. by moving the raster way from the field of image. Despite this, however, the drawback associated with the large object- film-distance remains. Furthermore, when handling the delicate raster there is a serious risk of the raster being damaged when it is replaced, so as to cause an impairment in image or picture quality.

Object of the invention

On the basis of the aforedescribed problems, an object of the present invention is to avoid large object-film- distances and the danger of damaging the raster, so as to enable the free exposure of small objects to be achieved even with the aid of a bucky of the aforesaid kind provided with digital detectors.

Another object is to enable free-exposures to be made with the detector in a defined or selected position in relation to the bucky and connected to an image presentation unit via a cable or in a cordless manner, and without needing to remove the detector in order to transfer stored image information after exposure.

Summary of the invention

These and other objects of the invention are achieved with a digital bucky of the aforedescribed kind having the characteristic features set forth in the characterizing clause of Claim 1.

Because the bucky box includes means which enable the detector to be withdrawn from the box, it is possible to place the object directly on the detector so that a desired free exposure can be taken.

In one embodiment of the invention said means may be implemented by providing the box with a movable lid, e.g. a liftable or outwardly pivotal lid, that includes the ion chamber and raster.

In this embodiment no re-adjustment with renewed centering of the radiation source is necessary. Instead, a light cross is shown on the exposed image of field of the detector and shows where the focus impinges on the object. The same applies when the bucky box is movable in accordance with another embodiment, e.g. can be displaced horizontally relative to the detector.

An alternative embodiment, which is preferred in practice, is characterized in that the detector can be moved into and out of the box horizontally, and in that the radiation source is adapted so as to enable it to be focused onto the detector in its withdrawn position.

In this embodiment, the ion chamber and the fragile raster will thus remain in position inside the bucky box and need not therefore be exposed to risks that can impair future image quality.

Various types of arrangements can be provided which will enable the detector to be withdrawn to one or more pre- selected, defined positions or also to a desired position that corresponds to the size of the object to be exposed.

In the first instance, the radiation source may be displaced mechanically or manually to a position that corresponds to the position of the detector. When the detector is withdrawn to a selected position, the position of the radiation source can be adjusted manually with the aid of the aforesaid light cross, or can be adjusted with the aid of an automatic guidance system which sets the radiation source in relation to the position taken by the detector.

In order to eliminate the risk of damage to the detector, it is preferred that the box includes a detector latching device that functions to prevent the detector from being completely withdrawn from the box and which will also functions to releasably block the detector in its withdrawn position. The latching device is also conveniently adapted to come into operation automatically when the box is obliquely positioned. Such oblique positioning of the box can occur, for instance, when the bucky is swung from a position beneath a patient table, i.e. a position for vertical radiation, to a vertical position on one side of said table, i.e. for receiving horizontal radiation. In one embodiment, the latching device coacts with a sensor which indicates on a system control panel that the latching device has been activated.

The latching device may be implemented in different ways, depending on existing circumstances. In one preferred embodiment, the latching device has the form of a rack mounted on one side of the withdrawable detector and coacting with engagement elements mounted on the box and engaging between two mutually adjacent rack teeth.

When an inventive bucky is used in practice, it can be expected that the withdrawable detector will be subjected to certain significant strain, for instance when subjected to the weight of a foot to be X-rayed. Other types of more or less unforeseeable loads can also occur in practice, for instance a withdrawn detector may be hit by a moving object or subjected to some other type of load.

Accordingly, one embodiment of the invention is characterized by guide means, such as side strips, located between the box and the detector and functioning to absorb any reasonable strain to which the detector is subjected when withdrawn from the bucky.

Correspondingly, the detector will preferably be resilient- ly mounted in the bucky box, so as to absorb impact forces in occurring movement directions.

The detector may include to this end a damping device that is active in the movement direction of the detector to dampen impact forces to which it is subjected and to enable the detector to spring to one side when subjected to load in its inward and outward movement directions.

In a more developed arrangement in which the detector includes sensors which coact with the radiation source and which enable the radiation source to be centered accurately in relation to the detector in one or more withdrawn positions thereof, the aforesaid damping arrangement may be adapted to deactivate the sensors at the same time as it performs its damping function.

This will ensure that the means for controlling and setting the radiation source will not be at risk should the detector be subjected to unforeseeable stresses or strains. The digital detector is conveniently connected to the image presentation unit, which is preferably a computer and associated display screen, by means of an electric cable, or by magnetic or optical means.

However, the detector may be connected to the image presentation unit in a cordless fashion, which provides greater flexibility in some cases. Correspondingly, movement of the radiation source to a position that corresponds with the position to which the detector is withdrawn can also be controlled in a cordless fashion, even though a cable connection will normally be preferred in this case.

The radiation source may possibly be column-supported, although it is normally preferred to mount the radiation source on the ceiling of the room concerned since this affords greater flexibility and enables a wider area to be covered than in the former case. The bucky will also suitably include a sheet of acrylic material, plexiglass or carbon fiber material to protect the raster.

The image field of the detector is a delicate component of the detector, and, accordingly, a thin carbon fiber plate is placed on the image field to protect it from mechanical influences and other damage. Carbon fibre is a mechanically durable material and has low absorption with respect to X- rays.

The invention will now be described in more detail with reference to exemplifying embodiments thereof and also with reference to the accompanying schematic drawings. Brief description of the drawings

Figure 1 illustrates in perspective the principle components of X-ray radiographic equipment that includes an inventive digital bucky.

Figure 2 is a perspective view of the digital bucky in the equipment shown in Figure 1, with the digital detector inserted in its box.

Figure 3 is a view corresponding to the view of Figure 2 but shows the detector in a withdrawn position.

Figure 3 illustrates so-called free-exposure or uncovered exposure of a hand with the digital bucky in a horizontal withdrawn position.

Figure 5 illustrates an example of free exposure, namely of a foot, with the detector in a withdrawn, inclined posi- tion.

Finally, Figures 6 and 7 illustrate a column stand which includes a pivotal arm that carries the bucky, the box of which can be displaced to uncover the detector.

Detailed description of preferred embodiments

Referring first to Figure 1, there is shown X-ray radio- graphic equipment that includes a digital bucky which has a raster fixedly or movably mounted therein and which comprises a rectangular box whose dimensions are determined by the size of the image field concerned and which is located beneath a patient table 9. The size of the image field shall be at least 24x35 or 43 cm. The box houses an image receptor in the form of a digital detector which is connected electrically to an image presentation unit in the form of a computer 5 and associated picture screen 5a, by means of a cable 4.

The equipment also includes a movable radiation source 8 which delivers X-ray radiation onto the image field of the detector.

The rectangular bucky box 2 is shown in more detail in Figures 2 and 3. The box 2 has a lid or an upper part 2a which accommodates an ion-chamber and a fixed or movable raster (not shown) .

The digital detector 3 is provided with an upper carbon fiber protective layer 3a and can be withdrawn relative to the box 2 and is provided with a handle 3b to this end.

The detector and the box are provided with a coacting latching device in the form of a rack 3c fitted along one short side of the detector. The box is fitted, in turn, with a rack engaging element in the form of a pin 2b that engages between two mutually adjacent teeth on the rack 3c such as to releasable latch the detector 3 in the position in which the detector is situated. The latching device is adapted to come into operation automatically when the box is swung to an inclined position, i.e. to a position in which the detector will tend to fall from the box under the influence of gravity.

The latching device coacts with a sensor (not shown) which indicates when the latching device is activated, on a system control panel (not shown) .

Extending along the side edges of the detector are guide strips 3d which are received in correspondingly shaped grooves or channels in the box. These guide strips 3d and said corresponding grooves in the box are adapted to take- up reasonable stresses and strains to which the detector may be subjected in its withdrawn position.

The detector 3 is also resiliently mounted in the box, so that impact forces to which the detector may be subjected when moved into and out of the box can be taken-up. Figure 2 illustrates a small pneumatic cylinder 12 that forms part of this movement damping arrangement.

When the detector is withdrawn, the radiation source 8 shall be adjusted to a corresponding setting. This setting may be effected manually, in which case the operator can use the light cross that is projected onto the detector by the radiation source and that discloses where the focus of said source is situated. Alternatively, or in addition, the radiation source may be adapted so as to allow a limited number of pre-determined positions to be adopted, where each position corresponds to a pre-determined detector withdrawal position.

In a more sophisticated arrangement there is used an automated control system which ensures precise setting of the radiation source in relation to the position in which the detector is situated, and where the radiation source is also adapted for respective horizontal and inclined beam paths when the detector is situated in a vertical or an inclined position respectively. Figure 5 shows the detector 3 in one such inclined position with so-called free exposure of a smaller object, such as a foot.

Figure 4 illustrates free exposure of a hand with the detector withdrawn from the box in a horizontal position, wherewith the radiation source 8 is adapted typically for a vertical beam path.

The detector 3 may include sensors (not shown) which coact with the radiation source and which enable the radiation source to be centered accurately in relation to the detector in one or more withdrawn positions thereof. In this case, the damping arrangement 12 is adapted to deactivate said sensor in conjunction with said arrangement performing its damping function.

Figures 6 and 7 illustrate an alternative embodiment of the bucky box 2 in which said box is carried by an arm 12b of a column stand 12, said arm being pivotal about a horizontal pivot axis 12a. In this case, the actual bucky box 2 and the ion-chamber and raster can be displaced from the position shown in Figure 6 to the position shown in Figure 7, so as to lay the digital detector 3 open for free exposure by means of the radiation source 8 , which in this case need not change position in conjunction with displacing the box.

Claims

1. A digital bucky having a fixed or movable raster and comprising a) a preferably rectangular box (2) of pre-determined dimensions, b) an image receptor housed in the box and having the form of a digital detector (3) which is coupled electrically, magnetically or optically to an image presentation unit, e.g. a computer (5) and associated picture screen (5a) , said connection being effected either in a cordless fashion or by means of a cable (4) , c) an ion-chamber and a fixed or movable raster located in the box between the detector and an outwardly lying object

(10) , and d) a movable radiation source (8) which delivers X-ray radiation onto the image field of the detector, characterized in that the box (2) includes means for moving the detector (3) free from the ion-chamber and the raster so as to enable free exposure of smaller objects (10) , for instance a foot, knee or the like, directly on the detector.

2. A digital bucky according to Claim 1, characterized in that the box (2) includes a movable lid (2a) i.e. a lid which can be raised or swung outwardly and which contains an ion-chamber and a raster.

3. A digital bucky according to Claim 1, characterized in that the box (2) and/or the detector (3) is/are movable, preferably displaceable relative to each other.

4. A digital bucky according to Claim 3, characterized in that the detector (3) is displaceable or withdrawable from the box (2) ; and in that the radiation source (8) is adapted to enable it to be focused on the detector (3) in a withdrawn position of said detector.

5. A digital bucky according to Claim 4, characterized in that the box (2) includes a detector latching device (2b, 3c) which is adapted to prevent the detector from being completely withdrawn from the box and which releaseably blocks the detector in the position to which it is with- drawn.

6. A digital bucky according to Claim 5, characterized in that the latching device (2b, 3c) is adapted to come into operation automatically when the box is positioned obliquely.

7. A digital bucky according to Claim 5 or 6, characterized in that the latching device (2b, 3c) coacts with a sensor which when the latching device has been activated gives an indication to this effect a system control panel.

8. A digital bucky according to any one of Claims 1-7, characterized by guide means, e.g. guide strips (3d) disposed between the box (2) and the detector (3) and functioning to take-up reasonable stresses and strains to which the detector may be subjected in its withdrawn position.

9. A digital bucky according to any one of Claims 1-8, characterized in that the detector (3) is resiliently fixed to the box (2) so that impact forces on the detector will be absorbed.

10. A digital bucky according to Claim 9, characterized in that the box fastener means includes damping means (12) which function to dampen impact forces on the detector and enable the detector to spring to one side when subjected to an overload in its inward and outward movement directions.

11. A digital bucky according to Claim 10, in which the detector includes a sensor that coacts with the radiation source (8) to enable said source to be centered accurately in relation to the detector in one or more of its withdrawn positions, characterized in that the damping means (12) is adapted to deactivate the sensor in conjunction with performing its damping function.