Patent Application
20160249997
The invention relates to the general technical field of calibration devices for calibrating surgical instruments used in conjunction with various medical procedures.
In order to be used in image-guided surgery, instruments have to be calibrated, so that their precise size, geometry and configuration is known while the surgical procedure is being performed. In particular, the spatial position of the instrument's functional section, such as for example the instrument tip, must be determined relative to at least one tracking marker which is assigned to the instrument and allows the instrument to be tracked by means of a surgical tracking system.
WO 02/061371 A1 shows a calibration device having a V-shaped groove or channel into which the cylindrical shaft of an instrument to be calibrated is inserted, wherein the tip of the instrument rests against a stop provided in the groove. In order to ensure that the instrument is positioned precisely within the groove during the calibration procedure, a self-actuating tool holder comprising a spring-biased ball bearing is positioned above the groove, such that the tool is securely held in the groove by the spring-biased ball bearing. The direction of the spring force acting on the instrument shaft points exactly towards the apex of the groove, thereby passing both of the flat surface areas extending from the apex on both sides. The applied spring force therefore has to hold the instrument shaft firmly against both of the surface areas of the V-shaped groove at a relatively small angle between the direction of the spring force and each of the surface areas, such that it can be difficult to hold the instrument shaft firmly on the two surface areas. It is therefore quite easy for the instrument shaft to tilt within the V-shaped groove, thus precluding an exact and precise calibration procedure.
It is the object of the present invention to provide a calibration device which allows a medical instrument to be calibrated in an efficient and reliable manner.
This problem is solved by the subject-matter of any appended independent claim. Advantages, advantageous features, advantageous embodiments and advantageous aspects of the present invention are disclosed in the following and contained in the subject-matter of the dependent claims. Different advantageous features can be combined in accordance with the invention wherever technically expedient and feasible.
The calibration device according to the invention comprises at least one supporting surface which is configured to provide support for a medical instrument which is brought into contact with at least one of the one or more supporting surfaces for a calibration procedure, wherein the calibration device comprises means which exert at least one force on the medical instrument, the at least one force being directed towards the at least one of the one or more supporting surfaces.
In other words, the calibration device according to the invention comprises one or more supporting surfaces which can be used to ensure that the instrument to be calibrated is positioned precisely relative to the calibration device by a physical contact between the instrument and the at least one supporting surface. It is necessary to maintain this physical contact during a calibration procedure which may include moving the instrument relative to the calibration device, for example about the axis of a longitudinal instrument shaft. In order to aid in maintaining this physical contact and therefore also the exact placement of the instrument during the calibration procedure, the calibration device according to the invention comprises means which exert at least one force on the medical instrument, in particular on the sections of the instrument which lie nearest the respective supporting surface. Each of the forces is assigned to a respective supporting surface and is directed towards the respective supporting surface, so as to maintain the physical contact between each of the respective supporting surfaces and the instrument to be calibrated. The angle between the direction of said force and the respective supporting surface is preferably between 80° and 100° and more preferably about 90°. For each supporting surface, the corresponding force generated by the force exerting means of the respective supporting surface is directed towards the supporting surface.
In accordance with a preferred embodiment of the present invention, at least one of the one or more supporting surfaces comprises said force exerting means. In other words, the medical instrument which contacts the respective supporting surface does not lie between said force exerting means and the supporting surface. In particular, the respective force exerting means lies on or underneath the respective supporting surface, opposite the medical instrument which contacts the supporting surface. With the force exerting means positioned this way, each of the supporting surfaces “pulls” the instrument towards itself.
The calibration device according to the invention preferably comprises at least two supporting surfaces which are arranged so as to simultaneously support one medical instrument during a calibration procedure. Two such supporting surfaces can for example form a V-shaped groove in order to support a cylindrical instrument shaft, wherein an additional supporting surface can serve as a stop which supports the tip of the cylindrical shaft or instrument. In addition, the at least two supporting surfaces can be configured to allow a rotational movement and/or a translational movement of the medical instrument relative to the calibration device during a calibration procedure. Using this embodiment of the invention comprising three supporting surfaces which form a V-shaped groove and a stop, various instruments comprising longitudinal cylindrical shafts of different diameters can be calibrated in terms of their shaft axis and instrument tip, for example by rotating the instrument shaft around its longitudinal axis within the V-shaped groove, thereby maintaining the contact between the instrument and each of the three supporting surfaces.
In accordance with another preferred embodiment, the force exerting means are configured to restrict the movement of a medical instrument relative to the calibration device to a rotational movement or to a translational movement. Such a configuration prevents any unintended tilting of the instrument relative to the supporting surfaces.
At least one of the one or more supporting surfaces can also be configured to provide one or more forms of contact with the medical instrument, in particular one or more of:
It is generally conceivable for the position of the calibration device to be spatially fixed within the surgical environment, wherein the invariant position of each of the supporting surfaces is known to the tracking system. In accordance with one preferred embodiment of the present invention, however, a preferred calibration device can be freely moved within the surgical environment. If the calibration device is not configured to be registered each time it has been moved, for example by using a pointer instrument to palpate at least three known registration marks provided on the calibration device, then the calibration device preferably comprises at least one tracking marker which allows a medical tracking system to track the calibration device in real time. Such tracking markers can be active or passive optical tracking markers, electromagnetic tracking markers or ultrasound tracking markers which have to exhibit a predetermined spatial relationship with respect to each of the supporting surfaces.
The force exerted on the medical instrument can be one or more of various kinds of forces. The force exerting means can for example comprise electromagnets which can be switched on or off in order to hold the instrument on the supporting surfaces using an electromagnetic force. Suction means which generate a vacuum between the supporting surfaces and the instrument are also conceivable. Alternatively or additionally, an electrostatic force can be exerted on the instrument by the force exerting means.
In accordance with a preferred embodiment of the present invention, the force exerting means exert a magnetic force on the medical instrument. To this end, at least one of the supporting surfaces can comprise a permanent magnet on and/or underneath the supporting surface which then “pulls” the instrument towards the supporting surface. Additionally or alternatively to the permanent magnet, an electromagnet can be provided.
In general, the invention can also provide a force fit between the calibration device and the medical instrument to be calibrated.
The calibration device according to the invention can also comprise a plurality of supporting surfaces which are configured to provide support for different medical instruments. An arrangement of at least two supporting surfaces which can form a V-shaped groove can for example allow a calibration procedure to be performed for instruments comprising a longitudinal cylindrical shaft by turning the instrument about the longitudinal axis of the cylindrical shaft, wherein an additional supporting surface can be provided in order to allow at least one other kind of medical instrument to be calibrated, such as for example a chisel which comprises a blade which can be supported by a flat, angled supporting surface.
In the following, the invention is described with reference to the enclosed figures which represent preferred embodiments of the invention, though without limiting the scope of the invention to the specific features shown in the figures.
All of the supporting surfaces 1A to 1C are provided on the calibration device in a predetermined spatial relationship with respect to three passive tracking markers 4 which are configured to be tracked by a medical tracking system, so that the spatial position of the calibration device and its supporting surfaces 1A to 1C are known to the medical tracking system.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/050575 | 1/14/2014 | WO | 00 |
