1. Field of the Invention
The invention relates to an apparatus for medical diagnosis and/or therapy, including a patient table provided with
a patient table top, PA1 an elevating mechanism for adjusting the height of the table top, PA1 said elevating mechanism being provided with at least one hinge which supports the patient table top, bears on a base surface and comprises at least two arms, PA1 and a drive mechanism which is arranged between the base surface and the table top in order to drive the height adjustment of the elevating mechanism.
2. Description of the Related Art
An apparatus comprising a table top and an elevating mechanism for adjusting the height of the table top is known from U.S. Pat. No. 4,157,743.
In apparatus for medical applications utilizing a patient table, the height of the patient table is preferably adjustable between a lowermost position comparatively close to the floor of the workspace and an uppermost position comparatively far above this floor. In order to achieve a comparatively low lowermost position of the patient table it would be feasible to form a recess in the floor of the workspace in order to lower the elevating mechanism therein. However, building managers do not appreciate interventions in the building structure in order to accommodate apparatus; moreover in most buildings it is not possible to lower an apparatus (partly) into the floor because the floor of one space at the same time constitutes the ceiling of a space situated therebelow. Therefore, there is a need for an elevating mechanism which has a small structural height in the lowermost position and a high height in the uppermost position.
A further requirement imposed on a patient table is that it should occupy a limited floor surface area only, so that the attending staff can comfortably work at and walk around the table without colliding with the frame of the table or without their movements being impeded. Consequently, a patient table having a compact base construction is required.
Furthermore, the patient table in apparatus for medical applications is increasingly required to be highly resistant to bending in load conditions, i.e. it should be constructed so as to be very rigid. This is important for radiation therapy where first a region of a patient to be irradiated is defined and subsequently the irradiation is actually performed. Between the defining of the region to be irradiated and the execution of the irradiation the patient, and hence also the table on which the patient is arranged, may not be displaced relative to the equipment except in a suitably controlled manner. During tomographic imaging the table should also retain exactly the same orientation and position during exposure, since the image will be unsharp otherwise.
It is expected that in the near future it will become possible to perform surgical operations on the basis of one or more images of the region to be treated which have been made in advance. Such methods are also known as image guided surgery. An image guided surgery system is used to show a surgeon the position of a surgical instrument in an operating region in the body of a patient. Images, such as X-ray CT or MRI images, are made of the patient prior to the operation. A position measuring system measures the position of the surgical instrument relative to the patient during the operation and a data processor calculates the position in such a prior image which corresponds to the measured position of the surgical instrument. The image formed in advance is displayed on a monitor and the actual position of the surgical instrument is reproduced therein. The surgeon can observe the image on the monitor so as to see where the surgical instrument is situated in the operating region, without the surgeon having a direct view of the instrument. The image on the monitor shows how the surgeon can move the surgical instrument in the operating region without incurring a high risk of unnecessary damaging of tissue and notably without a risk of damaging of vital organs.
Such an image guided surgery system is preferably used in neuro surgery in order to show the surgeon exactly where in the brain the surgical instrument is situated during brain surgery. During such operations it is of crucial importance that the patient is not subjected to any changes of position, other than perfectly controlled changes of position, relative to the position occupied at the instant at which the image was formed. This can be achieved only if no or only perfectly controlled movements of the table top occur.
The elevating mechanism which is known from the cited United States Patent comprises a plurality of pantographs which support the table top and each of which includes a number of pivotably interconnected arms. The known elevating mechanism occupies a surface area on the floor which is approximately equal to the dimensions of the table top to be displaced. The hinges of such an elevating mechanism can be readily constructed so as to be free from play and in order to ensure that such a hinge offers adequate rigidity against horizontal displacement, such a hinge can be constructed so as to have a width which is comparable to that of the table and also to have adequately robust hinge arms which may have, within given limits, an arbitrarily heavy construction. Using this known elevating mechanism, therefore, a base can be realized for a patient table which is sufficiently rigid and has a compact construction.
Moving the table top up and down requires a drive mechanism which fits within the compact construction of the elevating mechanism, offers adequate rigidity in the vertical direction with a view to the above rigidity requirements, and has a simple construction which preferably consists of commercially available components.