Micro-milling cutter for skull minimally invasive surgery and preparation method of micro-milling cutter

Abstract

The invention discloses a micro-milling cutter for a skull minimally invasive surgery and a preparation method of the micro-milling cutter. The diameter of the micro-milling cutter is micron-sized. The micro milling cutter comprises a cutter handle and a cutter head arranged at the end of the cutter handle, the cutter head comprises a first milling part, a second milling part and a third milling part which are sequentially arranged in the direction from a cutter point to the cutter handle, and the three milling parts are coaxially arranged; the first milling part is of a regular triangular pyramid structure, the edge forms a first edge blade, and the top forms a tool nose; the second milling part is annularly and alternately enclosed by parallel sections and inclined sections, a blade is formed at the junction of the parallel sections and the inclined sections, the parallel sections are parallel to the axis of the micro-milling cutter, and the inclined sections are inclined by a set angle relative to the axis of the micro-milling cutter; the cutting edges on the two sides of the same parallel tangent plane are connected with the same first edge cutting edge; the third milling part is of a regular triangular prism structure, the edges of the third milling part form second edge blades, and the blade ends on the two sides of the same inclined section are connected with the same second edge blade. The diameter of the micro-milling cutter is micron-sized, hole milling drainage is carried out on the skull, trauma in the operation process is small, postoperative pain is reduced, and healing time is shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-nano processing, and in particular relates to a micro-milling cutter used for minimally invasive skull surgery and a preparation method thereof. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Cerebral hemorrhage refers to primary non-traumatic bleeding in the brain parenchyma, also known as spontaneous bleeding. It is a disease caused by rupture of cerebral blood vessels, which causes blood to flow out. The basic cause is hypertension and arteriosclerosis. Hydrocephalus refers to the accumulation of excessive fluid in the brain, mainly due to cerebrospinal fluid absorption disorders, obstructed circulation or excessive secretion, which leads to progressive expansion of the ventricular system or (and) subarachnoid space expansion, often accompanied by increased intracranial pressure.

[0004] For the treatment of diseases such as cerebral hemorrhage and hydrocephalus, micro-milling drainage surgery has the following advantages over oral drug treatment: 1. Drainage surgery can directly treat cerebral hemorrhage lesions, remove hematomas, water accumulation or reduce bleeding lesions, thereby effectively controlling bleeding, reducing intracranial pressure, avoiding further nerve tissue damage, and reducing trauma and postoperative healing time; 2. Drainage surgery can be performed in a shorter period of time, especially for patients with acute cerebral hemorrhage, timely surgery can quickly alleviate the condition and reduce mortality; 3. With the assistance of imaging technology, the operation can accurately locate the bleeding lesions, accurately remove hematomas, water accumulation or reduce bleeding lesions, reducing surgical risks and injuries; 4. Drainage surgery can effectively reduce some complications related to cerebral hemorrhage, such as hydrocephalus, cerebral infarction, etc., which helps to improve the treatment effect and recovery speed.

[0005] At present, the milling tools used in the medical industry are relatively large in size, generally ranging from centimeters to millimeters. During surgery, they will cause a large degree of mechanical damage to the skull. If the operation is improper, it will cause serious mechanical damage, increase the degree of postoperative pain, and prolong the healing time. Summary of the invention

[0006] In view of the deficiencies in the prior art, an object of the present invention is to provide a micro-milling cutter for minimally invasive skull surgery and a method for preparing the same.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] In a first aspect, the present invention provides a micro-milling cutter for minimally invasive skull surgery, wherein the diameter of the micro-milling cutter is in the micrometer range;

[0009] The micro-milling cutter comprises a tool handle and a tool head arranged at the end of the tool handle, wherein the tool head comprises a first milling part, a second milling part and a third milling part arranged in sequence from the tool tip to the tool handle, and the three milling parts are coaxially arranged;

[0010] The first milling part is a regular triangular pyramid structure, the edge of which forms the first edge blade, and the top forms the blade tip;

[0011] The second milling portion is formed by alternating parallel cut surfaces and inclined cut surfaces in a circumferential direction, and a cutting edge is formed at the intersection of the parallel cut surfaces and the inclined cut surfaces. The parallel cut surfaces are parallel to the axis of the micro-milling cutter, and the inclined cut surfaces are inclined at a set angle relative to the axis of the micro-milling cutter. The cutting edges on both sides of the same parallel cut surface are connected to the same first edge cutting edge.

[0012] The third milling part is a regular triangular prism structure, whose edges form second edge blades, and the blade ends on both sides of the same inclined section are connected to the same second edge blade.

[0013] The diameter of the micro-milling cutter of the present invention is in the micron level. When treating cerebral hemorrhage, the micro-milling cutter has a smaller diameter, which can not only effectively reduce intracranial pressure, but also effectively reduce trauma to the skull, minimize postoperative healing time, and reduce the patient's pain level.

[0014] The first milling part, as the tip of the micro-milling cutter, has the smallest diameter and a regular triangular pyramid structure, and can be efficiently inserted into the skull for positioning.

[0015] The second milling section is the transition zone of micro-milling, and is axially symmetrical as a whole, which can maximize the stability of the surgical process, improve the quality of the surgical incision, and reduce trauma to the skull. In addition, the second milling section is the main working area, which is subject to the greatest resistance. The most blades are set here, which can effectively improve the efficiency of the operation and reduce the resistance allocated to each blade, thereby effectively reducing the wear of the blade and increasing the service life of the micro-milling cutter.

[0016] In addition, experiments have shown that the area with the greatest stress is located at the junction of the shank and the cutter head. Arranging multiple cutting edges at the second milling part can effectively reduce the force of the micro-milling cutter during the working process, thereby effectively alleviating the stress concentration phenomenon at the junction of the shank and the cutter head, preventing the cutter head from breaking, and effectively increasing the service life of the micro-milling cutter.

[0017] The third milling part is the last auxiliary micro-milling area. The diameter of its circumscribed circle is equal to the diameter of the knife handle. The diameter of the surgical incision can be adjusted to be equal to the knife handle so that the knife handle can be inserted to ensure the smooth progress of the operation.

[0018] In addition, since the micro-milling cutter in the present invention is micron-grade, small in size, and difficult to process, in order to ensure the processing accuracy, the blade of the micro-milling cutter is designed to be a straight blade type.

[0019] In some embodiments, the angle between each face of the regular triangular pyramid structure of the first milling portion and the micro-milling cutter axis is 55-65°, preferably 60°.

[0020] Through experiments, it was found that when the angle between each face of the regular triangular pyramid structure of the first milling part and the micro-milling cutter axis is about 60°, the surgical efficiency is relatively high, and the structure of the first milling part is more solid, less prone to damage, and has a longer service life.

[0021] When the angle is smaller, the first milling portion is more slender and more easily damaged during surgery. When the angle is larger, the first milling portion is thicker and shorter, the drilling resistance is greater, affecting the efficiency of surgery, and the blade is easily damaged.

[0022] Preferably, each face of the regular triangular pyramid structure is integrally formed with the corresponding inclined cut surface of the second milling portion. This structure is easier to process, and it is easier to ensure the quality of the surgical incision and reduce surgical damage.

[0023] In some embodiments, the parallel cut surface of the second milling portion is integrally formed with the side surface of the regular triangular prism structure of the third milling portion.

[0024] One-piece molding means that during the micro-milling process, the material is obtained through a single process without the need for more than two processes.

[0025] In some embodiments, a diameter of a circumscribed circle of the regular triangular prism structure of the third milling portion is equal to a diameter of the tool handle.

[0026] In some embodiments, the diameter of the micro-milling cutter is 300-700 μm.

[0027] In some embodiments, the micro-milling cutter is made of Si3N4 ceramic material. The micro-milling cutter adopts silicon nitride bioceramic material with good biocompatibility, which can ensure the mechanical properties of the micro-milling cutter on the one hand, and reduce the risk of postoperative complications on the other hand.

[0028] In some embodiments, the cutting edge of the blade of the micro-milling cutter is a nano-scale cutting edge. A special processing technology is used to make the cutting edge of the micro-milling cutter a nano-scale cutting edge, which is relatively sharp, which can not only improve the efficiency of surgery and reduce the degree of damage to the skull, but also improve the morphology of the surgical incision, making the morphology of the surgical incision good and convenient for intubation and drainage.

[0029] In a second aspect, the present invention provides a method for preparing the micro-milling cutter for minimally invasive skull surgery, comprising the following steps:

[0030] Select the cylindrical raw material with a set diameter;

[0031] The end of the cylindrical raw material is processed into a regular triangular prism by using a femtosecond laser, and the diameter of the circumscribed circle of the regular triangular prism is equal to the diameter of the cylindrical raw material;

[0032] Then, a femtosecond laser is used to process an inclined surface at the connection between the two surfaces at the end of the regular triangular prism, and the inclined surface and the axis of the cylindrical raw material are at a set angle; the other two inclined surfaces are processed in the same way to form a regular triangular pyramid structure, and a rough micro-milling cutter is obtained;

[0033] The micro-milling cutter rough product is surface treated by using focused ion beam technology (FIB) to obtain the micro-milling cutter.

[0034] When using femtosecond laser processing to prepare rough micro-milling cutters, the femtosecond laser is used to remove the excess parts of the raw materials and prepare the preliminary shape of the micro-milling cutter, which can effectively improve the processing efficiency.

[0035] Then, the focused ion beam technology is used to perform sputtering surface processing on the rough micro-milling cutter, which can accurately control the amount of material removed and effectively reduce the surface roughness of the micro-milling cutter. At the same time, the blade reaches a nano-level edge with good sharpness.

[0036] Although focused ion beam technology can achieve precision machining, the inventors found during the research and development process that due to the small size of the micro-milling cutter, if only focused ion beam technology is used to process the cylindrical raw material, it is easy to produce a redeposition effect, that is, the sputtered removed material is redeposited on the surface of the raw material, making it difficult to achieve the expected machining accuracy.

[0037] Firstly, a femtosecond laser is used to remove the excess material in the raw material to obtain a rough micro-milling cutter, and then the rough micro-milling cutter is treated with a focused ion beam, which can effectively avoid the occurrence of redeposition and effectively improve the processing quality.

[0038] In some embodiments, the single pulse energy of the femtosecond laser is 15-18 μJ, the pulse width is 280-320 fs, the frequency is 50-70 kHz, and the power is 0.95-1 W.

[0039] In some embodiments, during focused ion beam processing, the tool surface is first processed using processing parameters of 25-35keV and 50-70nA, and then the milling cutter blade is trimmed using processing parameters of 5-10keV and 10-15nA.

[0040] In some embodiments, the cylinder raw material is made of Si3N4 ceramic material.

[0041] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0042] The micro-milling cutter of the present invention uses a Laser-FIB equipped with a femtosecond laser device. For the processing of this micro-milling cutter, Laser-FIB processing has the following main advantages compared with single FIB processing:

[0043] Faster processing speed: Laser can remove a large amount of material and prepare the preliminary shape of the micro-milling cutter, which greatly improves the processing efficiency, especially when large areas or large volumes of material need to be removed quickly. FIB has a slow cutting speed and is suitable for fine processing, while the high-speed removal ability of laser makes up for this shortcoming; Smaller heat-affected zone: Although laser processing involves higher temperatures, by combining with FIB, FIB can be used for modification in fine areas, thereby reducing the impact of heat-affected zone and residual stress on material properties; Combination of large-scale rough processing and fine processing: Laser is suitable for large-area rough processing, and FIB can be used for local fine processing afterwards, achieving a combination of high efficiency and high precision; Reduced redeposition effect: When FIB is used alone for deep etching, material redeposition may occur. Laser can quickly remove a large amount of material, reduce the possibility of redeposition, and thus improve processing quality.

[0044] Therefore, in the rough processing of milling cutter forming, femtosecond laser can be used to remove a large number of materials, thereby saving processing time and cost. The purpose of fine processing is to trim the surface of the milling cutter. The small beam of FIB can be used to mill the surface and edge of the milling cutter, so that the milling cutter has extremely low surface roughness and a relatively sharp edge.

[0045] The milling tools currently used in the medical industry are between centimeters and millimeters in size, and improper operation during surgery can cause serious mechanical damage. This micro-milling cutter has a diameter of 500μm, which is smaller than traditional medical drainage surgical instruments. Therefore, milling holes for drainage in the skull can reduce trauma during surgery, reducing postoperative pain and healing time.

[0046] This micro-milling cutter uses Si3N4 bioceramic material, which is a ceramic material used in medical and biological applications. It usually has excellent biocompatibility, chemical stability and mechanical properties, and is suitable for orthopedic implants, dental restorations, medical devices and other fields. Si3N4 has high bending strength, high fracture toughness, very low friction coefficient, and strong corrosion resistance. For medical milling cutters, the mechanical properties of Si3N4 ceramic materials can meet the use requirements of micro-milling cutters. Therefore, the risk of postoperative complications when using medical milling cutters made of Si3N4 ceramic materials for skull milling and drainage is relatively low. The prepared micro-milling cutter was used to perform milling experiments on pig skulls. The surface morphology of the pig skull after milling was good, and intubation and drainage could be performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0048] Figure 1 This is the stress distribution cloud diagram of the micro-milling cutter milling hole;

[0049] Figure 2 It is the deformation distribution cloud diagram of micro-milling cutter;

[0050] Figure 3 It is the stress distribution cloud diagram of the micro-milling cutter;

[0051] Figure 4 Flow chart of micro-milling tool for Laser-FIB machining;

[0052] Figure 5 Image of raw material before FIB processing of micro milling cutter;

[0053] Figure 6 Figure 1 is a diagram of the micro-milling cutter after processing, where a is the main view of the micro-milling cutter; b is the top view of the micro-milling cutter; c is the three-dimensional morphology of the micro-milling cutter; d is the edge morphology of the micro-milling cutter;

[0054] Figure 7 These are the morphological images of minimally invasive holes in the skull, where a is the morphological image of the microholes in the outer layer of the skull; b is the morphological image of the microholes in the inner layer of the skull. DETAILED DESCRIPTION

[0055] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0056] The present invention will be further described below in conjunction with the embodiments.

[0057] Example

[0058] The design method of medical skull micro-milling cutter based on Laser-FIB technology is as follows:

[0059] S1: The micro-milling cutter was designed using Solidworks software. The blade type was designed with a straight blade and a blade inclination angle of 60°. First, the structure is relatively simple, and second, the micro-milling cutter is easy to process during preparation. The length of the micro-milling cutter is 5 mm and the diameter is 0.5 mm.

[0060] The specific structure of the micro-milling cutter is as follows: the micro-milling cutter comprises a tool handle and a tool head arranged at the end of the tool handle, wherein the tool head comprises a first milling part, a second milling part and a third milling part arranged in sequence from the tool tip to the tool handle, and the three milling parts are arranged coaxially;

[0061] The first milling part is a regular triangular pyramid structure, the edge of which forms the first edge blade, and the top forms the blade tip;

[0062] The second milling portion is formed by alternating parallel cut surfaces and inclined cut surfaces in a circumferential direction, and a cutting edge is formed at the intersection of the parallel cut surfaces and the inclined cut surfaces. The parallel cut surfaces are parallel to the axis of the micro-milling cutter, and the inclined cut surfaces are inclined at a set angle relative to the axis of the micro-milling cutter. The cutting edges on both sides of the same parallel cut surface are connected to the same first edge cutting edge.

[0063] The third milling portion is a regular triangular prism structure, whose edges form second edge blades, and the blade ends on both sides of the same inclined section are connected to the same second edge blade.

[0064] The angle between each face of the regular triangular pyramid structure of the first milling portion and the micro-milling cutter axis is 60°.

[0065] Each face of the regular triangular pyramid structure is integrally formed with the corresponding inclined section of the second milling part; the parallel section of the second milling part is integrally formed with the side of the regular triangular prism structure of the third milling part; the diameter of the circumscribed circle of the regular triangular prism structure of the third milling part is equal to the diameter of the tool handle.

[0066] S2: The Explicit Dynamics module in the ANSYS Workbench finite element simulation software was used to analyze the dynamics of the micro-milling cutter designed in the early stage for milling holes in the skull, and to analyze the milling effect and stress generated during milling. Figure 1 As shown: the stress gradually decreases from the position of the hole to the outside, the maximum stress value generated by the micro-milling cutter on the skull milling hole is 3.3MPa, and the micro-milling cutter causes slightly less damage to the skull.

[0067] S3: The stress-strain analysis of the micro-milling cutter is performed through the Modal module in ANSYS Workbench to analyze the strength of the micro-milling cutter. Figure 2 is the deformation distribution cloud diagram of the micro-milling cutter, Figure 2 It can be seen that the deformation of the part closer to the handle connection is getting smaller and smaller, and the maximum deformation is 5μm, which is much smaller than the 500μm size in the early design; Figure 3 The stress distribution cloud diagram of the micro-milling cutter shows that the maximum stress occurs at the root of the blade, which is also the part where material removal and retention are connected during tool processing, which is consistent with the force of the tool in actual processing. The maximum stress value at the tip of the tool is 5.27MPa, which is much lower than the fracture strength of Si3N4 material.

[0068] S4: The modal analysis of the micro-milling cutter is performed through the Modal module in ANSYS Workbench to obtain the vibration frequency of the micro-milling cutter. The result is: the actual vibration frequency is much higher than the first-order natural frequency in the modal simulation, so the micro-milling cutter will not produce resonance during milling processing.

[0069] The preparation method of the micro-milling cutter comprises the following steps:

[0070] (1) The processing process of micro milling cutter is as follows Figure 4 As shown, the substrate is a complete cylindrical shape, such as Figure 5 As shown in the figure, the first step is to process a surface at one end of the cylindrical raw material, such as Figure 4 As shown in step 1 of FIG, the second step is to process the second and third surfaces at a 60° angle after processing the first surface, as shown in FIG. Figure 4 The shape after processing is a triangular prism. The third step is to process a bevel at a 60° angle to the horizontal direction at the connection between the two faces of the triangular prism. The other two faces are processed in the same way to obtain the preliminary shape of the micro-milling cutter. Finally, the 6 processed faces are milled by ion beam to obtain a micro-milling cutter with extremely low surface roughness and nano-scale cutting edge.

[0071] (2) The diameter of the micro-milling cutter is 500 μm, the blade design adopts a straight blade type, and the blade inclination angle is selected to be 60°. First, the structure is relatively simple, and second, the micro-milling cutter is easy to process during preparation.

[0072] (3) Process the micro texture according to the process in the previous section. The processing effect is as follows Figure 6 As shown, (a) is the main view of the micro-milling cutter, (b) is the top view of the micro-milling cutter, (c) is the spatial morphology of the micro-milling cutter, and (d) is the edge morphology of the micro-milling cutter. First, a femtosecond laser is used to quickly remove the corroded micro-milling cutter blank. The single pulse energy used is 16μJ, the pulse width is 300fs, the frequency is 60kHz, and the power is 0.96W. After laser rough processing, ion beam is used for fine processing. The processing parameters are 30keV and 60nA for processing the tool surface, and then the processing parameters are 5keV and 12nA for trimming the milling cutter blade. The prepared micro-milling cutter is placed under SEM for observation, as shown Figure 6 As shown in the figure, it can be seen that the structure of the prepared micro-milling cutter is the same as the micro-milling cutter designed in the early stage, and all items meet the requirements.

[0073] The prepared micro-milling cutter was used to perform milling experiments on skull micro-holes. The skull micro-hole milling experiment platform was composed of the CM-1 vertical boring and milling machining center and vertical boring and milling machining system produced by Haas Company of the United States, the Kistler9129AA dynamometer produced by Kilash Company of Germany, and the skull fixture. The feed speed was 5mm / min and the spindle speed was 1000r / min. After the pig skull minimally invasive small hole milling experiment, in order to ensure that the skull micro-holes after milling can be clearly observed, the pig skull after milling was ultrasonically cleaned with physiological saline, then wiped dry with absorbent cotton balls, and then placed under a three-dimensional ultra-depth microscope for observation. Figure 7This is a morphological diagram of the outer layer of the skull milled by a micro-milling cutter. It can be seen that the bone density around the milled micro-holes is relatively large and the structure is compact. The cortical bone is used to bear the load caused by the outside world or itself. Figure 7 (b) is the micro-hole morphology after the micro-milling cutter milled the inner layer of the skull. Combining the two pictures, it can be seen that the pig skull is completely milled by the micro-milling cutter, and the micro-hole contour after milling is relatively regular. Although there are a small amount of skull debris, it does not affect the subsequent insertion of the hose.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A micro-milling cutter for minimally invasive skull surgery, characterized in that: The diameter of the micro-milling cutter is in the micrometer range; The micro-milling cutter comprises a tool handle and a tool head arranged at the end of the tool handle, wherein the tool head comprises a first milling part, a second milling part and a third milling part arranged in sequence from the tool tip to the tool handle, and the three milling parts are coaxially arranged; The first milling part is a regular triangular pyramid structure, the edge of which forms the first edge blade, and the top forms the blade tip; The second milling portion is formed by alternating parallel cut surfaces and inclined cut surfaces in a circumferential direction, and a cutting edge is formed at the intersection of the parallel cut surfaces and the inclined cut surfaces. The parallel cut surfaces are parallel to the axis of the micro-milling cutter, and the inclined cut surfaces are inclined at a set angle relative to the axis of the micro-milling cutter. The cutting edges on both sides of the same parallel cut surface are connected to the same first edge cutting edge. The third milling portion is a regular triangular prism structure, whose edges form second edge blades, and the blade ends on both sides of the same inclined section are connected to the same second edge blade.

2. The micro-milling cutter for minimally invasive cranial surgery according to claim 1, characterized in that: The angle between each face of the regular triangular pyramid structure of the first milling portion and the micro-milling cutter axis is 55-65°, preferably 60°; Preferably, each face of the regular triangular pyramid structure is integrally formed with the corresponding inclined section of the second milling portion.

3. The micro-milling cutter for minimally invasive cranial surgery according to claim 2, characterized in that: The parallel cut surface of the second milling portion and the side surface of the regular triangular prism structure of the third milling portion are integrally formed.

4. The micro-milling cutter for minimally invasive cranial surgery according to claim 2, characterized in that: The diameter of the circumscribed circle of the regular triangular prism structure of the third milling portion is equal to the diameter of the tool handle.

5. The micro-milling cutter for minimally invasive cranial surgery according to claim 1, characterized in that: The diameter of the micro-milling cutter is 300-700 μm.

6. The micro-milling cutter for minimally invasive cranial surgery according to claim 1, characterized in that: The micro-milling cutter is made of Si3N4 ceramic material.

7. The micro-milling cutter for minimally invasive cranial surgery according to claim 1, characterized in that: The cutting edge of the blade of the micro-milling cutter is a nanometer-scale cutting edge.

8. The method for preparing the micro-milling cutter for minimally invasive cranial surgery according to any one of claims 1 to 7, characterized in that: The steps include: Select the cylindrical raw material with a set diameter; The end of the cylindrical raw material is processed into a regular triangular prism by using a femtosecond laser, and the diameter of the circumscribed circle of the regular triangular prism is equal to the diameter of the cylindrical raw material; Then, a femtosecond laser is used to process an inclined surface at the connection between the two surfaces at the end of the regular triangular prism, and the inclined surface and the axis of the cylindrical raw material are at a set angle; the other two inclined surfaces are processed in the same way to form a regular triangular pyramid structure, and a rough micro-milling cutter is obtained; The micro-milling cutter rough product is surface treated by using focused ion beam technology to obtain the micro-milling cutter.

9. The method for preparing a micro-milling cutter for minimally invasive cranial surgery according to claim 8, characterized in that: The single pulse energy of femtosecond laser is 15-18μJ, the pulse width is 280-320fs, the frequency is 50-70kHz, and the power is 0.95-1W.

10. The method for preparing a micro-milling cutter for minimally invasive cranial surgery according to claim 8, characterized in that: During focused ion beam treatment, the tool surface is first processed using processing parameters of 25-35keV and 50-70nA, and then the milling cutter blade is trimmed using processing parameters of 5-10keV and 10-15nA.

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