Stereotactic device for cutting hard tissue on the skull bone using energetic radiation

Abstract

Stereotactic device for cutting hard tissue on the skull bone, with - a stereotactic frame (22) designed to be attached to the head of a patient, and - a stereotactic arc (25) attached to the stereotactic frame (22) via at least one pivot joint, which, when the stereotactic frame (22) is attached to the head of a patient, can be tilted over the head by means of the pivot joint, characterized by that a laser applicator (17) is attached to the stereotactic arc (25) and can be moved along the stereotactic arc (25) via a motor drive (28''), and the stereotactic arc (25) can be tilted on the stereotactic frame (22) via a further motor drive (28, 28'), wherein the laser applicator (17) has a dynamic 2D beam deflection device (11) by which a processing laser beam (2) coupled into the laser applicator (17) can be guided over an area of ​​the hard tissue to be cut, and a focusing optic (12) with a focus position for the coupled processing laser beam (2) adjustable by means of the focusing optic (12) or other optical elements, and wherein a measuring device (6) is arranged in or connected to the laser applicator (17) with which a cutting depth of a kerf produced with the processing laser beam (2) and a residual thickness of the skull bone (15) in the kerf can be measured.

Description

Technical application area

[0001] The present invention relates to a stereotactic device for cutting hard tissue on the skull bone of a patient, which device has a stereotactic frame which is designed to be attached to the patient's head, and a stereotactic arch which is attached to the stereotactic frame via at least one pivot joint and which can be tilted over the head by means of the pivot joint when the stereotactic frame is attached to the patient's head.

[0002] In neurosurgery, innovative therapeutic methods have been developed in recent years that significantly improve the quality of life and survival rate of critically ill patients. These methods require that the patient be operated on while awake, as complex functions such as speech must be tested during the operation. This applies, on the one hand, to deep brain stimulation (DBS) operations, in which electrodes are implanted with high precision into defined target areas of the brain to treat complex movement disorders (e.g., Parkinson's disease, dystonia, or essential tremor). Deep brain stimulation enables patients whose motor skills were so severely impaired that they became socially isolated and dependent upon care to live permanently symptom-free lives.Awake surgery is also becoming increasingly important in the treatment of low-grade gliomas (the most common brain tumor), as it has been shown that with these infiltratively growing tumors, the most extensive tumor removal possible, right up to the point of loss of brain function, is necessary to achieve the longest possible survival with a good quality of life. Despite these successes, the majority of patients with severe movement disorders or a brain tumor forgo awake surgery. The reason for this is the traumatic experience of drilling or reaming the skull. This procedure, accompanied by immense noise and strong vibrations, is perceived as frightening and extremely stressful. State of the art

[0003] Currently, deep brain stimulation involves opening the skull with a mechanical drill (12 mm diameter) whose rotation stops automatically at the point of penetration. Unfortunately, this results in injuries to the meninges beneath the bone in around 10% of cases. In rare cases, the brain is also injured. During awake surgery for brain tumors, a hole is drilled and then a large area of ​​the skull is reamed open using a hand-held reamer (craniotomy). An angled metal shoe is attached to the reamer to protect the meninges (dura) and brain from injury. Nevertheless, injuries to the meninges or even the blood vessels beneath the bone (sinus) frequently occur during craniotomy.

[0004] Laser-assisted cutting techniques are also well-known in the field of medical surgery. For example, a system for robot-assisted osteotomy has been developed. A robotic arm moves a laser head with a scanner over the bone tissue to be cut or positions it in front of the surgical site to cut bone tissue by distributing the laser energy across the scanner. However, the robotic arm and processing head move considerable masses, posing a very high safety risk during head surgery. The required precise incision on the patient's head also presents a challenge.

[0005] US 2023 / 0218316 A1 describes a guide assembly for inserting a percutaneous invasive instrument, such as a biopsy needle, through a selected insertion point on a patient's body and along a selected insertion path. The guide assembly comprises a semicircular arch connected to a base plate by sliding hinges, with the center of curvature of the arch located at the insertion point. A guide body is slidably connected to the arch. By rotating the arch around the hinges, a first angle of the insertion path is adjusted. By moving the guide body along the arch, a second angle of the insertion path is adjusted.

[0006] The object of the present invention is to provide a stereotactic device for cutting hard tissue on the skull bone of a patient with energetic radiation, which device entails a lower risk of injury to the patient, ensures high cutting accuracy and enables an opening of the skull with largely no stress on the patient. Description of the invention

[0007] The object is achieved with the device according to patent claim 1. Advantageous embodiments of the device are the subject of the dependent patent claims or can be derived from the following description and the exemplary embodiment.

[0008] The proposed device comprises a stereotactic frame designed for attachment to a patient's head. A stereotactic arch in the form of an arcuate rail, also referred to as an aiming bar, is attached to the stereotactic frame via at least one pivot joint. When the stereotactic frame is attached to the patient's head, the aiming bar can be tilted over the head using the pivot joint, for example, along the head, i.e., in the sagittal direction. The proposed device is characterized in that a laser applicator is attached to the stereotactic arch and can be moved along the stereotactic arch via a motor drive. The stereotactic arch itself can also be tilted on the stereotactic frame via a further motor drive. The laser applicator has a dynamic 2D beam deflection device and focusing optics.The focus position can be adjusted using the focusing optics or other optical elements in the laser applicator. A processing laser beam coupled into the laser applicator can be guided over a section of the hard tissue to be cut with the laser beam using the 2D beam deflection device. The focusing optics with adjustable focus position enable the focus of the processing laser beam to be adjusted depending on the respective cutting depth and any changes in the distance of the laser applicator from the skull during processing. The laser applicator also has a measuring device or is connected to a measuring device with which the cutting depth of the cutting kerf created with the processing laser beam and the residual thickness of the skull bone in the cutting kerf – at least with a small residual thickness of ≤ 200 µm – can be measured.Various measurement techniques can be used for this purpose, such as ultrasound or optical measurement. An OCT (Optical Coherence Tomography) measuring device is preferably used, which directs a measuring beam coaxially to the laser beam onto the hard tissue to be cut to measure the cutting depth and the residual thickness of the skull.

[0009] With the proposed device, the skull bone can be opened safely, noiselessly, and vibration-free, with local anesthesia, making it virtually unnoticeable for the patient. By monitoring the residual thickness of the skull bone with the measuring device, unintentional injury to the tissue beneath the skull bone is avoided. The laser cutting process is carried out using the laser applicator, which distributes laser pulses from a short-pulse laser along the cutting line using the dynamic 2D beam deflection device, ensuring efficient laser cutting of the bone without thermal tissue damage.

[0010] The measuring device, located in or connected to the laser applicator, measures the cutting depth and residual bone thickness during cutting or ablation. In the case of an OCT measuring device, for example, this is done using the measuring beam carried along by the processing laser beam. This online control prevents injury to the dura mater beneath the bone and the brain.

[0011] For small skull openings, the laser applicator remains stationary and the incision is guided by the dynamic 2D beam deflection device, which can be formed, for example, by a 2D scanner mirror or by two separate 1D scanner mirrors arranged for beam deflection in two mutually orthogonal axes of rotation. For large skull openings, the laser applicator is additionally moved along the arc using a motor drive and the arc as a whole is tilted using another motor drive, for example along the longitudinal axis of the skull. To move the laser applicator along the arc, it preferably has a carriage that can be moved along the arc, to which the laser applicator is attached, preferably via a detachable connection, and which is moved along the arc using the motor drive. Since the patient's head is in a horizontal position during the procedure orSince the incision is fixed in the stereotactic frame, no unwanted relative movement between the laser beam and the skull can occur. The incision is planned before the procedure begins by taking a CT or MRI scan of the head with the stereotactic frame fixed to it to obtain the precise reference position of the stereotactic frame and the respective incision position.

[0012] The guidance of the laser applicator and thus of the processing laser beam is fully automated via the control of the motor drives according to the cutting plan using a specially designed control unit. The movement of the laser applicator is monitored and controlled with high precision via a measuring system, e.g., using suitable incremental encoders. This automated stereotactic system, also referred to below as a stereotactic robot, enables material removal with an accuracy in the submillimeter range (approximately 0.1 mm). This opens up the possibility of safely removing bone even very close to critical structures (e.g., in the area of ​​the skull base and the caudal cranial nerves). Injury to the meninges underlying the bone is avoided by controlling the process with continuous measurement of the residual bone thickness, preferably using optical coherence tomography (OCT).The control unit is preferably designed to stop processing with the laser beam when a target residual thickness is reached. The control unit can be located in or on the laser applicator, for example, but also separately. By automating the stereotaxic system, during complex operations in which numerous holes must be drilled in the skull and electrodes must be placed at various defined locations in the brain (stereo electroencephalogram, stereo EEG), these locations can be automatically approached by the system according to the preoperative planning. This relieves the surgeon, who previously had to set the coordinates manually, and reduces the susceptibility to errors in electrode positioning. The stereotaxic robot does not move large masses like a robotic arm. Due to its design, the moving mass of the applicator cannot collide with the patient's head.

[0013] The processing laser used in the proposed device preferably uses a CO2 laser, which emits pulsed laser radiation with pulse lengths in the picosecond, nanosecond, or microsecond range, preferably with emission wavelengths between 9.3 µm and 10.6 µm, or a pulsed solid-state laser with pulse lengths in the picosecond, nanosecond, or microsecond range, preferably with wavelengths between 2.7 µm and 3.3 µm. In an advantageous embodiment, the processing laser beam is guided to the laser applicator via a flexible or articulated beam guide. This can, for example, be a suitably designed articulated mirror arm. A fiber guide to the laser applicator can also be used.

[0014] Preferably, the proposed device also has a spray system with one or more nozzles that generates a spray mist, preferably of water, for local humidification and cooling of the bone in the processing area.

[0015] In an advantageous embodiment of the proposed device, the laser applicator is attached to the stereotactic arch via a motorized linear adjustment unit. This linear adjustment unit allows the laser applicator to be moved radially relative to the stereotactic arch. This additional motorized drive is, in turn, controlled by the control unit. This allows a constant distance between the laser applicator and the bone surface to be maintained during processing.

[0016] In a further development of the device, the stereotactic frame has an inner ring-shaped frame part that is fixed to the patient's head, and an outer frame part that can be rotated around the inner ring-shaped frame part (in the ring plane), to which the stereotactic arch is attached via at least one pivot joint. This further development offers the advantage that the stereotactic arch can then also be rotated on the stereotactic frame. This allows all trajectories to be set at the target points (located in the center of the arch). This avoids the need to set the stereotactic arch in a position that is disruptive for the surgeon, or certain trajectories that are technically impossible to achieve.This is particularly important for complex stereotactic operations such as stereo-EEG or biopsies in the posterior cranial fossa, as fewer technical limitations allow the anatomically optimal trajectory to be selected more often.

[0017] The motorized stereotaxic system or stereotaxic robot with the motor drives for tilting the stereotaxic arch and moving a carriage arranged so that it can move along the arch can also be operated without the laser applicator, for example to position a plurality of electrodes deep within the brain. The stereotaxic frame can also have, as described above, an inner ring-shaped frame part that is fixed to the patient's head, and an outer frame part that can rotate around the inner ring-shaped frame part and to which the stereotaxic arch is attached via at least one pivot joint. To position electrodes deep within the brain, a holder for thin, cylindrical electrodes with multiple contacts is attached to the carriage of the stereotaxic arch instead of the laser applicator.This holder is equipped with a micrometer screw to enable submillimeter-precise advancement of the electrodes into the brain. The motorized stereotaxic system can now be used to move to a wide range of positions with submillimeter precision, where electrodes are to be positioned deep within the brain based on preoperative planning. Holes are drilled at the corresponding positions using the laser applicator so that the electrodes can be inserted into the brain. This is important, for example, for so-called stereo-EEGs, which are used to determine the location of epileptic seizures. Based on this localization, a tailored surgical therapy ("tailored resection") is subsequently performed to treat the epilepsy. Other applications of the motorized stereotaxic system without the laser applicator are also possible. Short description of the drawings

[0018] The proposed device is explained in more detail below using an exemplary embodiment in conjunction with the drawings. Herein: Fig. 1 a schematic representation of an example of the laser applicator used in the proposed device and Fig. 2 a schematic representation of the proposed device with the stereotactic frame fixed to the head of a patient. Ways to implement the invention

[0019] The proposed device enables a safe, noise- and vibration-free ablation process on a patient's skull. The proposed device replaces the drills and milling cutters previously used with a laser beam source that emits short-pulsed laser radiation with pulse energies preferably in the range of 0.1 mJ to 10 J. This radiation can be used to cut narrow and deep grooves in bone tissue to create access to the brain. To ensure efficient cutting and avoid thermal tissue damage, the laser pulses must be distributed along the cutting line at repetition rates in the range of 0.1 to 1000 kHz in such a way that, on the one hand, the resulting process heat does not accumulate locally and, on the other hand, a continuous, deep cutting groove is created.The pulses are distributed by the laser applicator's dynamic 2D beam deflection device, which is controlled accordingly via the control unit. Suitable wavelengths for the processing laser beam are those that are well absorbed by bone tissue. Examples of suitable wavelengths for this are the CO2 laser wavelengths between 9.3 µm and 10.6 µm, as well as wavelengths between 2.7 and 3.3 µm. The process is controlled by a laser applicator 17, an example of which is shown in . Fig. 1 and is described below.

[0020] In this example, the laser beam 2 from a laser beam source 1 is transmitted via a beam guide 3 through two weakly reflective planar glass plates 4 and 4'. The small portion of the laser radiation reflected by the glass plates 4, 4' is detected by two position sensors 5, 5'. The position sensors determine the position and propagation direction of the laser beam 2 within the laser applicator. Using two automatically adjustable mirrors in the beam guidance system (not shown here), the beam position can be adjusted to the optical axis of the laser applicator in the event of misalignment using the mirrors in the beam guidance system and the position measurement. Via a deflection element 8, the laser beam is guided over a telescopic optics 9 and impinges on a dynamic 2D beam deflection unit 11 via a beam combiner 10.Behind the beam deflection unit 11, the laser beam 2 is focused by a focusing optics 12 onto the bone surface 15 to be cut, leaving the applicator housing 14 through an exit opening 13. Depending on the design, the exit opening 13 can be closed off by the focusing optics 12 or a protective window 13'.

[0021] An OCT sensor 6 emits an OCT measuring beam 7, which is guided to the applicator 17 via a beam guidance system 6', e.g., an optical fiber. This measuring beam 7 is superimposed with the laser beam 2 at the beam combiner 10 and then impinges on the deflection unit 11. The deflection unit 11 distributes the focuses of the two coaxial beams 2, 7 in the processing plane on the bone 15 in the feed direction (x-direction) of the cutting process and perpendicular to it (y-direction). During the ablation process, the bone surface is wetted with a water spray to ensure a carbonization-free and efficient laser ablation process. The spray comes from fine atomizing nozzles 16, which are arranged concentrically around the outlet opening 13 of the applicator housing 14. The OCT sensor 6 uses the OCT measuring beam 7 to measure the cutting depth d s and the remaining thickness d rThe measuring light runs antiparallel to the excitation direction of the OCT measuring beam 7 and is detected by the OCT sensor 6. The measuring signal controls the cutting process so that a defined thin residual thickness remains, preventing the laser beam 2 from damaging the brain tissue or dura beneath the bone 15. As the ablation depth increases, the position of the laser focus is shifted in depth (z-direction) into the bone 15 by adjusting a positionally adjustable lens 9' of the telescope 9.

[0022] The laser applicator 17 is located on a stereotaxic robot 21 (cf. Fig. 2). This comprises a stereotactic frame 22 and a stereotactic arch 25. In this example, the stereotactic frame 22 has an inner ring 22' with a platform 22'' that is rotatably mounted against the ring 22'. The inner ring 22' is screwed to the patient's skull 40 via brackets 23 with screws 24. The stereotactic arch 25 is attached to the platform 22'' of the stereotactic frame 22 via swivel joints. The arch plane is thus rotatably mounted so that it can be folded towards or away from the ring plane. On the stereotactic arch 25 there is a carriage 26 that can be moved along the arch. The applicator housing 14 is attached to the arch by a motorized linear adjustment unit 27.The applicator tip, from which the laser beam 2 emerges, can be moved in space by tilting the stereotactic arch 25, moving the carriage 26 along the arch 25, and linearly adjusting the applicator 17 with the adjustment unit 27. In contrast to conventional stereotactic systems, the stereotactic system of the proposed device is motorized. The stereotactic arch 25, the carriage 26, and the linear adjustment unit 27 are moved by motors 28, 28', 28'' via a sequence control (see . Fig.2). Furthermore, the stereotaxic system has additional degrees of freedom, via which the position of the arc center can be manually adjusted to a target point in the head (center-of-arc principle). This adjustment allows the surgeon to reach the preset arc center as the target point for any position of the arc 25 and the carriage 26 by radially guiding a surgical instrument in the arc plane. Using surgical planning software, the target trajectory for the cutting process of the proposed device, hereinafter also referred to as a laser osteotome, is determined based on preoperative image data.

[0023] The stereotactic laser osteotome can be operated in two application modes. For cutting small access openings, the laser applicator 17 is stationary. The laser focus is then moved along a closed cutting line via the beam deflection unit 11. The width of the cutting kerf is defined by moving the laser beam 2 transversely to the cutting direction, and the length of the cutting kerf is defined by moving it in the cutting direction. Adjusting the laser focus in depth via the telescope 9 ensures an efficient cutting process, even with increasing depth. During the cutting process, the cutting depth and residual thickness are measured via the OCT sensor 6 to regulate the local cutting depth and prevent the tissue from being processed beyond the bone.

[0024] In the second application, larger access openings are cut using the stereotactic laser osteotome. The laser focus is distributed on the bone surface by a combined movement of the applicator 17 via the stereotactic robot 21, the laser beam 2 via the beam deflection unit 11, and the focus adjustment of the telescope 9.

[0025] The beam deflection unit 11 can be designed as a 2D scanner mirror. A 2D scanner mirror is a mirror with a pivot point that can deflect a laser beam in two spatial directions. Alternatively, the beam deflection unit 11 can consist of two 1D scanner mirrors with two mutually orthogonal axes of rotation. List of reference symbols 1 laser beam source 2 laser beam 3 Beam guidance 4 glass plate 4' glass plate 5 Position sensor 5' position sensor 6 OCT sensor 6' beam guidance system 7 OCT measuring beam 8 Deflection element 9 Telescope optics 9' adjustable telescopic lens 10 beam combiners 11 2D beam deflection unit 12 Focusing optics 13 Exit opening 13' protective window 14 Applicator housing 15 bones 16 atomizer nozzle 17 Laser applicator 21 stereotaxic robots 22 Stereotactic frame 22' ring 22'' platform 23 Bracket 24 screw 25 Stereotactic bow 26 sleds 27 Linear adjustment unit 28 Engine 28' engine 28'' engine 40 skulls

Claims

[1] Stereotactic device for cutting hard tissue on the skull bone, with - a stereotactic frame (22) designed to be attached to the head of a patient, and - a stereotactic arch (25) which is attached to the stereotactic frame (22) via at least one rotary joint and which can be tilted over the head of a patient by means of the rotary joint when the stereotactic frame (22) is attached to the head of a patient, characterized by , that a laser applicator (17) is attached to the stereotactic arch (25) and can be moved along the stereotactic arch (25) via a motor drive (28''), and the stereotactic arch (25) can be tilted on the stereotactic frame (22) via a further motor drive (28, 28'), wherein the laser applicator (17) has a dynamic 2D beam deflection device (11), via which a processing laser beam (2) coupled into the laser applicator (17) can be guided over a region of the hard tissue to be cut, and a focusing optics (12) with a focus position for the coupled processing laser beam (2) that can be adjusted by the focusing optics (12) or other optical elements, and wherein a measuring device (6) is arranged in the laser applicator (17) or is connected to the laser applicator (17), with which a cutting depth of a cutting joint produced with the processing laser beam (2) and a residual thickness of the skull bone (15) in the cutting joint can be measured. [2] Stereotactic device according to claim 1, characterized bythat the measuring device (6) is an OCT measuring device which directs a measuring beam (7) for measuring the cutting depth and the residual thickness of the skull bone (15) coaxially to the processing laser beam (2) onto the hard tissue to be cut. [3] Stereotactic device according to claim 1 or 2, characterized by that the laser applicator (17) has a spray device with which a liquid film moistening and cooling the bone surface can be applied to the skull bone (15) during cutting. [4] Stereotactic device according to one of claims 1 to 3, characterized by that the laser applicator (17) is connected to a flexible or articulated beam guiding device (3) via which the processing laser beam (2) is coupled into the laser applicator (17). [5] Stereotactic device according to claim 4, characterized bythat the beam guiding device (3) is formed by an articulated mirror arm or a fiber optic with an optical fiber. [6] Stereotactic device according to one of claims 1 to 5, characterized by that the stereotactic arch (25) has a carriage (26) which can be moved along the stereotactic arch by the motor drive (28'') and to which the laser applicator (17) is attached. [7] Stereotactic device according to claim 6, characterized by that the laser applicator (17) is attached to the carriage (26) via a detachable connection. [8] Stereotactic device according to one of claims 1 to 7, characterized by that the stereotactic frame (22) has an inner annular frame part (22') and an outer frame part (22'') rotatable about the inner annular frame part (22'), to which outer frame part the stereotactic arch (25) is fastened via the at least one rotary joint. [9] Stereotactic device according to one of claims 1 to 8, characterized by that the laser applicator (17) is attached to the stereotactic arch (25) via a motorized linear adjustment unit (27), via which the laser applicator (17) can be moved in a direction radial to the arch (25). [10] Stereotactic device according to one of claims 1 to 9, characterized by that the dynamic 2D beam deflection device (11) has a 2D scanner mirror or two 1D scanner mirrors which are designed for beam deflection into two mutually orthogonal axes of rotation. [11] Stereotactic device according to one of claims 1 to 10, characterized by that the motor drives (28, 28', 28''), the measuring device (6) and the laser applicator (17) are connected to a control unit which controls them for cutting guidance when cutting the hard tissue on the skull bone.

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