PATENT ABSTRACT
A computed tomography-fluoroscopy method is invented for interventions comprising the steps of combining a floating patient table with a cross-sectional imaging modality for interventions under visual computed tomography control. A handle is installed on the patient table, which is mechanically decoupled from the central control system. During an intervention, the table is brought to a random position, and a single-scan or scan-series is triggered. A light-beam localizer is used for orientation and positioning the single-scan or scan-series.

PATENT DESCRIPTION
FIELD OF THE INVENTION 
     The invention relates to a method and an apparatus on scannographs, in particular for computed tomographyradioscopy for interventions, and refers to adjustment of a table for the patient, fixing of its position, as well as triggering of a light-beam localiser and of a single scan after mechanical decoupling of the scannograph from the central control system. 
     DESCRIPTION OF THE BACKGROUND ART 
     Computed tomography has enriched medical diagnostics in an extraordinary manner and not only rendered numerous radiation-exposing X-ray examinations, such as encephalography or angiography, superfluous but also took advantage of the tomograms gained thereby for planning and checking the radiation therapy of tumors. Numerous pathological processes in the entire trunk of the body, such as carcinomata or enlarged lymph nodes, can be classified only by withdrawal of tissue and subsequently treated. Such biopsies can, inter alia, be carried out with the help of computed tomography. When doing so, the position of a needle introduced into the body is represented by executing a single sectional drawing in the plane of the needle. 
     After corresponding preparation of the patient, i.e. after positioning of said patient and disinfection of the skin of same as well as after having locally anaesthetised the point of puncturing, the biopsy needle is, usually outside the gantry, introduced so as to lie under the surface of the skin and, thereafter, the table with the patient will be moved into the gantry for conduction of the first check scan. Control of that procedure is effected from the console of the scannograph, which console, for reasons of radiation protection, is situated outside the examination room. When a lamination is radiographed, the medical personnel are not in the examination room. After the sectional drawing has been displayed on the monitor, the patient is moved out of the gantry. After a possibly required positional correction of the needle, another radiograph is taken once the table with the patient has been moved into the gantry through the console. The entire procedure--moving of the patient out of the gantry and into the gantry again--takes up a great deal of time and, during the whole examination, the patient must remain quiet and motionless. 
     Various solutions have been proposed, dealing with positioning of the patient resp of specific parts of the body or of tables for patients as exactly as possible, e. g.: 
     positioning of a patient, in case of a medical panoramic radiographic facility, with the help of a sensor for determining the relative position of an object to be examined towards the radiographic facility, the determined data being compared with those of the relative position of a tomographic zone towards the radiographic facility (German Patent resp Laying-open Specification 38 08 009), 
     a fixed device for holding the patient whereas the housing of the scannograph can be linearly displaceably) guided by means of driving and guiding facilities 
     (German Utility Model 92 18 322), 
     a motor-driven and computer-controlled day-bed for the patient, which day-bed can be moved into the housing of the scannograph, 
     moving the patient synchronously with radiographing successive scans, departing from an initial position--e.g. in case of examinations of the area of the cranium (European Patent 579 036), 
     a scannograph housing for receiving the day-bed with the patient, in which case--in order to avoid information losses between diagnosis and surgical treatment--the day-bed for the patient is, at the same time, constructed as an operating table (German Patent resp Laying-open Specification 42 02 302), 
     physicians&#39; or dentists&#39; examination facilities, e.g. for radiographing the temporomandibular joint (German Patent resp Laying-open Specification 39 37 077) or for scannographing the knee after fixation of the lower leg (German Patent resp Laying-open Specification 38 09 535), 
     scannograph with means for generating a silhouette which is represented on a monitor synchronously with the respective position of the measuring system towards the day-bed for the patient (German Patent 42 18 637, U.S. Pat. No. 5,373,543). 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention is based on the object to develop a method and an apparatus by which, for computed tomography-radioscopy for interventions, exact positioning of the patient can be achieved and the number of scans for seeking the needle can be reduced. 
     This object was solved by combining a floating table for the patient with a sectional drawing modality for biopsies under a visual ct check. The apparatus according to the invention comprises a table for the patient, which is included in a scannograph and which is provided with a handle serving for mechanically setting a random position of the table after decoupling from the central control system, and foot switches for triggering a light-beam localiser on the one hand and a single scan on the other hand. The handle newly mounted to the table for the patient enables random positioning of the table after mechanical decoupling from central control. The foot switches are installed in the examination room. They can trigger both the light-beam localiser and a single scan. 
     The term &#34;floating table for the patient&#34; designates a day-bed for the patient, which, with but small mechanical effort, can freely be moved by the examining person along an axis at any time during examination. 
     By &#34;sectional drawing modality&#34; an examination technique is meant which, for visualising an examined object, generates sectional drawings in a plane with a defined lamination thickness. The sectional drawing modalities include computed tomography, ultrasonics or nuclear spin resonance tomography. 
     Installation of the handle on the table for the patient enables setting of any table position by hand during surgical treatment. The digitally indicated table position always corresponds to the real position. The light-beam localiser is triggered via an additionally installed foot switch in the examination room just like--via a further foot switch a single scan (one lamination). In order to check the position of the needle, the table is--without any control from the console--rapidly moved out of the gantry and into the gantry again so that a fresh single scan can be triggered. 
     Surprisingly, it was found that the way of proceeding according to the invention provides, considering all the modifications--light, single scan following a pressure exerted by the foot, manually movable table with position indicator, and immediate tomogram monitoring, an examination modality by which biopsies can be conducted in more reliable a manner and which will lead to shortened examination periods. Since the patient can, by hand, be rapidly moved out of the gantry and into the gantry again--without having to leave the examination program--, the required amount of time will be considerably reduced. In order that the physician may stay in the room for inspecting the tomogram--, the latter as taken becomes visible to the examining person on a monitor standing in the gantry room. 
     Another advantage resides in that the patient is less exposed to radiation since, due to the exact table position achieved in accordance with the invention, superfluous scans for seeking the needle will be avoided. During surgical treatment, the medical personnel will remain in the examination room so as to affect the psyche of the patient in positive manner, if need be. 
     Apart from saving time, application of the method and apparatus according to the invention brings about multiplication of the technical possibilities and shows another new way in the field of computed tomography-radioscopy for interventions. Further advantages reside in minor exposition to radiation due to reduction of superfluous scans, in higher sensitivity, and, indirectly, in less complications as well--primarily due to the fact that the frequent manipulation, in case of needle correction, is not required any more under computed tomography-radioscopy. 
     With conventional radioscopy, continuous projection roentgenograms are produced, not permitting any spatial allocation. When doing so, a needle is guided to its destination under constant irradiation insofar as said destination can be made out at all in the projection. The hand of the examining person is mainly situated in the direct optical path. 
     However, movement of the table for the patient--which, on principle, is possible with most X-ray apparatuses--will not be brought about since puncturing is carried out under X-ray vision and the represented roentgenogram depicts areas of from 5 by 5 to 35 by 35 cm. Insofar, the invention is based on a principle which is different from single-scan triggering and moving the table by hand. 
     A manually operated scannograph has not become known since such a scannograph, because of the usually required lamination examination at defined lamination distances, cannot be realised and is of no clinical relevance. The combination of a floating table with a sectional drawing modality is new. Moreover, it would make sense only for biopsies under a visual ct check. 
     The invention shall be explained in detail on the basis of one embodiment. 
     Embodiment 
     The table 1 for the patient P is equipped with a handle 2 enabling the table to be taken to a random position after mechanical decoupling from central control 3. The digital indication of the table position is not affected thereby. After the patient P has been prepared in the usual way, the physician, subsequently to switching on of the light-beam localiser 4 via an additionally installed foot switch, 5 can now exactly position the table 1 within the sectional drawing modality 9. Then, a single scan (one lamination) will be triggered in the examination room via a second foot switch 6. Four seconds later, the tomogram will appear on a monitor 7; it will appear after one second, provided that all additional filters and subsequent tomogram processings are done without. The tonogram as taken becomes visible to the examining person on a monitor 7 standing in the gantry room. 
     The physician will remain in the examination room and, during surgical treatment, can affect the psyche of the patient P in positive manner. When the position of the needle has to be checked, the table 1 can rapidly be moved out of the gantry 8 and into the gantry 8 again without any control from the console. Thereafter, a fresh single scan can be triggered. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.