Navigation of medical instrument

The subject invention pertains to a device for inserting medical instruments into the human body. In a specific embodiment, the subject device can be made from a material which is invisible under Magnetic Resonance Imaging (MRI). The subject device can incorporate three or more MRI compatible marks. The imaging of these three or more markers can allow the determination of the orientation of the device. A virtual image of the device can then be shown in an MRI image.

BACKGROUND OF THE INVENTION

With the German patent specification DE 198 44 767 A1, a method attaching markers to a medical instrument that are detectable under MRI is already known. The orientation of the instrument within the MRI device can be determined with these points. However, the respective allocation of the measured markers to the instrument markers is impeded due to the similarity of the signal-emitting substance to the instrument material. The non-availability of an instrument fixation to the patient proves to be a further disadvantage. Such fixation could be achieved by use of trocars.FIGS. 2,3,4, and5show a device ensuring a minimally-invasive approach to the brain through a hole in the top of the skull. Such trocar is already known from patent specification DE 197 26 141 and prevents the risk of the so-called Brain Shift, which signifies the uncontrolled shifting of the brain inside the surrounding skull during an operation. This problem is not limited to the neuro field, but occurs whenever shifting tissue is punctured. The disadvantages of this kind of trocars are the following points:The adjustment of a navigation system adapting the devices to MRI imaging to such a neuro trocar is difficult.The neuro trocar is manufactured of titanium alloy, so that it is depicted as a homogenous formation with indistinct rim demarcation in the MR image. A three-dimensional orientation is difficult to assess. This, however, is highly essential, with the neuro trocar, unlike a stereotactic system, having no own reference point as it is fixed to the patient.

The invention presented herein aims to solve these and other problems.

BRIEF SUMMARY OF THE INVENTION

The subject invention pertains to a device for inserting medical instruments into the human body. In a specific embodiment, the subject device can be made from a material which is invisible under Magnetic Resonance Imaging (MRI). The subject device can incorporate three or more MRI compatible markers. The imaging of these three or more markers can allow the determination of the orientation of the device. A virtual image of the device can then be shown in an MRI image.

DETAILED DESCRIPTION OF THE INVENTION

The problem of the conventional neuro trocar being not sufficiently identifiably with regard to its orientation within the MRI, as described in patent DE 197 26 141, can be solved by designing a device of a material that is totally invisible under MRI. If then a minimum of three MRI compatible points are marked on it, an exact orientation can be determined by these three points; its position in the MRI procedure can be precisely assessed, and a virtual image of the trocar can be shown in the MRI picture.

Various systems for the technical realization of these points are described below.

The problem is shown in FIG.1. The medical instrument1with its reactive coordination system x′y′z′ shall be determined in its position relative to the patient coordination system xyz.

Both the adjustment of the instrument insertion channel10and the adjustment of the device3, which essentially corresponds to the devices1and2, can be correlated to each other by an angle adjustment (see FIG.4). An angle adjustment for the azimuth angle14and an angle adjustment for the zenith angle1are possible on the device3. When the position of the device3is known, the position of the instrument insertion channel10will also be known automatically. By an automatic pick-off of angular movement not shown inFIG. 4, azimuth and zenith angle could be directly measured and included into the MR image. The MR image could then always adjust to the orientation of the instrument insertion channel10so that the operation site16will always be optimally in the sight vane in the imaging of the MRI device. In such case, markers according to the principles20′,20″, and20′″ stated herein could be adapted in the device3or in a top for angle measurement21. Reversedly, it is also possible to measure the angle within the MR image and then to adjust at the device, i.e., the device follows the MR image.

The fixation of the instrument insertion channel10in a certain position can be achieved by tightening a fixing screw22as shown in FIG.5.

Through the instrument insertion channel10, a tube can be inserted deep into the operation site, which will then serve as a channel for inserting further instruments as shown inFIG. 6, the advantage being a stabilization of the instruments inserted under navigation. The stabilization channel23then holds the inserted instruments.FIGS. 8 and 9show a possibility where the instrument or the stabilization channel23can be cramped into a mounting6, which is shifting in axial direction on the instrument insertion channel10. Such mounting6can be lowered manually or automatically by a motor, electrically, hydraulically, by pneumatic power or by wire pull.

The orientation of the instrument insertion channel can be achieved by tilting. To allow this, two movable laminas7and8, relative to the device2and shifting to each other (as shown in FIG.9), are attached to the device. The instrument insertion channel10is guided through an oblong opening9in each lamina. By mechanical manual or automatic shifting of the laminas to each other, the instrument insertion channel is tiltable in various directions. Electrical, hydraulic or pneumatic actuations are possible for automatic shifting.

A further possibility of adjustment of the instrument insertion channel10, as shown inFIG. 11, is to position the instrument insertion channel by means such as a rotating and tilting motion via a worm wheel11mechanically or by motor, pneumatically, or by wire pull.

The orientation of the instrument is directly readable by the scaling at the positioning unit. It could also be monitored via the above-mentioned markers in the MR image.

In order to adapt the device to the imaging of the MRI device, a navigation system is to be integrated into the device itself.FIG. 2shows a device2with an instrument insertion channel10and three laterally extended reflectors12. The three mountings13for the reflectors12can be manufactured from one piece or can be three separate parts. The reflectors12could also be active optical light-emitting diodes. In such arrangement, the three reflectors or sending elements12can be monitored by an external camera system, and, due to the relative position of these three elements to each other, the spatial orientation of the device can be calculated and then be integrated in the MR image. Better still is the application of markers which are directly identified by the “magnet” (MRI), since this will prevent inaccuracies upon matching the coordination systems.

FIG. 3shows that this navigation device can also be directly connected to the instrument insertion channel10. There could also be a navigation system for the device2a well as for the instrument insertion channel10, resulting in having two navigation systems working with either different wavelengths or different codification or with different geometrically designed reflectors12. The device can be manufactured of a material that is not depictable under MRI or with other radiological imaging methods. Single parts or areas of the device could be designed of a material that is actively or passively identifiable under MRI. For instance, the entire device for the operation under MRI could be manufactured of plastics such as PEEK, and only certain parts would be designed of titanium. The device could also be designed to have hollow spaces containing a liquid which will emit active signals, such as liquids with unpaired proton spin, for instance a gadolinium-based liquid.FIG. 10shows a double-walled top filled with a signal-emitting liquid.

FIG. 5shows a device4designed completely of plastics, preferably PEEK (polyetheretherketone). This device4is screwed into the skull with a self-cutting thread19. Owing to the hardness of the plastic material, the device can be manufactured with a self-cutting thread. Such plastic device4is preferably designed as a disposable. Two navigation points, which could be placed inside the device either separated from one another or together, shall be exemplarily described at the device. As one possibility, the adjusting screw17in this PEEK instrument could be made of titanium. Titanium is imaged negatively, as a black spot, in the MRI device, so that the position of the device4is recognizable. With two further titanium points, the orientation of the device4can be identified in a similar way as with the navigation system ofFIG. 3or2. A gadolinium-containing liquid is filled into a hollow space18in this device. This liquid is an active liquid for the MRI device, to be imaged as a white spot in the MR image. With three such hollow spaces filled with a gadolinium-containing liquid, here also the position of the device4can be determined. It is now possible to combine such active spots such as the hollow spaces18with the respective active or passive points17, or self-reflecting or luminous marker points12, which will be identified by the MRI device or a navigation system connected to the MRI device. In this way, the localization and navigation of the device within the MRI is ensured. By use of various positioning points depicted differently in the MR image, it is possible to achieve an exact allocation of the measured points to the points at the device.

A so-called TrackPointer, as described in patent specification 298 21 944.1, can also be connected to the device by implanting it in the instrument insertion channel10.

The orientation of the instrument with regard to the operation system, or, in other words, the adaptation of the image to the device presented herein via the MRI device, can also be realized with the markers, according to the principle20stated herein, not only attached to the device3itself, but also to the instrument24, being inserted into the minimally-invasive channel2for a certain procedure, and to the angle measuring system25(FIG.7).

FIG. 7shows the process of pushing an instrument24through the device3into the operation area. A marker20′ is placed at its distal end20′, a second marker20″ in the insertion center of the device3as shown in FIG.5. The third marker20′″ is positioned on the angle measuring system25, which is freely adjustable around the device. The plane visible in the MR image will then be extended by the three points20′,20″, and20′″. Thus one will always see the instrument with its inserted length in the brain region, which is determined by the third point placed on the circular angle measuring system25. Such marking points could also be designed as small coils, as, for example, laid open with number200in patent application U.S. Pat. No. 5,353,795 by Sven P. Souza in FIG.2. Such an element is an active coil sending with a certain frequency and being deflected according to the system presented in the above-mentioned patent.

Such a device can be used to insert probes, for mechanical and mechanical-surgical instruments or endoscopes. The instrument insertion channel10could also be designed in form of several lumens, resulting in several channels instead of only one. The device can also be used to insert larger instruments in open OP's. Such a device could be designed as either reusable or disposable instrument.

A system as presented herein can be used not only for surgical interventions and procedures, but also for the insertion of electrodes to fight Parkinson's disease. It could also be applied as a shunt.

REFERENCE NUMBERS

1.Device2.Device, general for adaptation to a navigation system3.Device4.Plastic Device5.Double-walled top filled with contrast medium6.Mounting7.Movable lamina8.Movable lamina9.Opening10.Instrument insertion channel11.Worm wheel12.Reflector/optically emitting elements13.Reflector fitting14.Angle adjustment azimuth angle15.Angle adjustment zenith angle16.Operation site17.Titanium screw18.Hollow space filled with gadolinium-containing liquid19.Self-cutting thread20.MRI markers according to one principle presented herein21.Top with angle adjustment22.Fixing screw23.Stabilization channel24.Instrument25.Angle measuring system