X-ray or gamma ray systems or devices – Source support – Including object support or positioning
Patent
1985-04-23
1987-07-07
Howell, Janice A.
X-ray or gamma ray systems or devices
Source support
Including object support or positioning
378197, H05G 102
Patent
active
046792236
DESCRIPTION:
BRIEF SUMMARY
Field of invention
The present invention relates to a method for damping the natural vibrations and/or oscillations of movable pillar-stands carrying X-ray equipment, when making positional adjustments thereto.
Such a pillar-stand may be mounted to the ceiling, on the floor or on the wall of a room, and the equipment carried by said stand may comprise X-ray film exposure apparatus, a hospital bed or the like.
When the pillar-stand is suspended from the ceiling of a room, the stand often has an L-shape configuration, and the X-ray apparatus, hospital bed or the like is often positioned on a member which is movable in relation to the pillar-stand itself and which, either separately or together with the pillar-stand, has a U-shape, a C-shape or a similar shape.
A typical ceiling-hung pillar-stand often has the shape of an inverted L, and is mounted so as to be pivotable or adjustable about a vertical axis located in the upper part of said stand, at the end of the shorter leg thereof. The vertically extending, longer leg of the stand is provided with a further member which carries the X-ray equipment, such as exposure equipment and film-cassette holder or a hospital bed or the like.
This further member is normally arranged for vertical movement along the pillar-stand and is also mounted thereon for pivotal or rotary movement about a horizontal axis.
In the case of a typically ceiling-mounted pillar-stand of the aforedescribed kind, the height between ceiling and floor is 2.75 m, and the total height of the pillar-stand is slightly less than this measurement and measures, for example, about 2.5 m. When the pillar-stand carries X-ray equipment, the total weight may reach from 300 to 350 kg.
PRESENTATION OF THE UNDERLYING PROBLEMS RELEVANT TO THE INVENTION
One problem encountered with such pillar-stands, particularly with a pillar-stand mounted on the ceiling of a room, is that the stand can readily be set into free oscillation, e.g. when making positional adjustments, when the pillar-stand is swung about the vertical axis and/or the further part is swung about its horizontal axis.
Upon examination it has been found that the amplitude of this natural oscillatory movement in the case of a typical pillar-stand of the aforedescribed kind is about 2 mm, and that this amplitude is still close to 2 mm after a lapse of 12 seconds. After 36 seconds, the amplitude was found to have decreased to about 1 mm, and it took almost one minute before it could be said that the free oscillatory movement of the stand had ceased.
Tests have shown that when the pillar-stand is caused to oscillate or vibrate in an arbitrary direction -- e.g. by kicking the base of a ceiling-suspended pillar-stand -- the stand will relatively quickly begin to oscillate freely in one and the same plane, namely the plane exhibiting the lowest inertia against natural oscillation, in accordance with for example a central plane or symmetry plane which passes through the L-shaped stand and extends through its suspension point.
It will be understood that the course followed by natural oscillations of the aforedescribed kind constitutes a serious disadvantage, primarily because the X-ray exposure may be blurred as a result thereof. Thus, the phenomena of natural vibrations results, in turn, to the serious risk of necessitating the patient to be subjected to a repeated course of X-rays, with an increased X-ray dosage as a result thereof.
In order to further illustrate the decisive negative influence of the phenomena of natural oscillations on the final result, it can be mentioned that there are essentially three factors which contribute to the total blurring of an X-ray picture. These three factors are: geometric blurring blurring of the film system (limited resolution of the picture etc.), and movement blurring.
If these factors are assumed to have the numerical values a, b and c respectively, the total non-focussing or blurring effect is given by the expression ##EQU1## It will be seen herefrom that when one of these factors is substantially higher than th
REFERENCES:
patent: 2778948 (1957-01-01), Berger
patent: 3803418 (1974-04-01), Holstrom
patent: 4050551 (1977-09-01), Schmedemann et al.
patent: 4181347 (1980-01-01), Clark
patent: 4287424 (1981-09-01), Tomita et al.
patent: 4365343 (1982-12-01), Grady et al.
patent: 4420134 (1983-12-01), Flannelly
Behnke Gunther
Ohlson Carl-Eric
AO Medical Products AB
Howell Janice A.
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