Method for producing section ribbons from a sample block using a microtome, method for preparing a microscope sample for examination in an electron microscope, microtome and embedding mold for use therewith

Abstract

A method (1000) is disclosed for creating a section ribbon (800) from a sample block (700) using a microtome (100) having a blade (304), creating the section ribbon (800) to have a first partial ribbon comprising one or more first sections (802) of the sample block (700) and a second partial ribbon comprising one or more second sections (804) of the sample block (700), creating the first partial ribbon from a first surface region (703) of the sample block (700) and creating the second partial ribbon from a second surface region (705) of the sample block (700), the second surface region (705) being different from the first surface region (703), and retracting the sample block (700) from the blade (304) while creating the first partial ribbon and the second partial ribbon. A method (900) for preparing a microscopic sample (600) for examination in an electron microscope, a microtome (100) and an embedding mold (500) are also disclosed.

Description

[Technical field]

[0001] The present invention relates to a method for producing section ribbons from a sample block using a microtome, a method for preparing a microscope sample for examination in an electron microscope, a microtome and an embedding mold. [Background technology]

[0002] In particular, in the field of neuroscience, but also in other fields of biology and medicine, the examination of serial sections of tissue and the reconstruction of three-dimensional sample information from such serial sections of tissue, in particular by means of electron microscopy, is of great importance.

[0003] Corresponding methods may include, but are not limited to, the so-called "Serial Section Scanning Electron Microscopy" (ssSEM, S3EM) and the so-called "Serial Section Transmission Electron Microscopy" (ssTEM), the invention being particularly applicable in connection with ssSEM. However, it goes without saying that the embodiments described below are also applicable to any other method of an equivalent nature. In particular, the invention can essentially be used in connection with optical microscopy instead of electron microscopy, although the following description is directed to electron microscopy.

[0004] In such methods, as described further below, it may be advantageous to form a section ribbon that includes, in addition to a section containing the portion of the sample to be analyzed or tested (referred to herein as a "sample section"), also includes so-called "pusher" sections, "release" sections, "dummy" sections or "blank" sections (these terms are used synonymously herein), which may have the sole or essential purpose of extending or elongating the section ribbon and thus pushing the sample section forward. Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to improve the preparation of such types of sample ribbons, in particular at the liquid level, and in particular in terms of better reliability and ease of use. [Means for solving the problem]

[0006] According to one embodiment of the present invention, there is provided a method of producing section ribbons from a sample block using a microtome having a blade, the section ribbons being produced having a first partial ribbon with one or more first sections of the sample block and a second partial ribbon with one or more second sections of the sample block, the first partial ribbon being produced from a first surface region of the sample block and the second partial ribbon being produced from a second surface region of the sample block, the second surface region being different from the first surface region, and retracting the sample block from the blade during the production of the first partial ribbon and the second partial ribbon. In this manner, "pusher" sections and sample sections as described above can be produced in a convenient manner from a single sample block and using a microtome having a single clamp or holder for the sample block.

[0007] According to one embodiment of the invention, the method further comprises producing a sample block, the first surface region and the second surface region being formed as discontinuous surface regions of the sample block. Thus, the sample block may be particularly prepared for use in an advantageous method.

[0008] In this regard, the preparation of the sample block may comprise providing a precursor sample block having a continuous precursor region of a first surface region and a second surface region, where the preparation of the sample block comprises trimming the precursor sample block to form the first surface region and the second surface region from the precursor region. Since trimming may be useful in the field of microscopy in general to form a sample block, such an embodiment may be particularly advantageous since the first surface region and the second surface region may be formed in a single step during said trimming, which is performed in any case.

[0009] In an alternative embodiment of the invention, creating the sample block may include forming the sample block using an embedding mold configured to form the first and second surface regions or precursor regions thereof as discontinuous surface regions. Such an embodiment may be particularly advantageous as the surface regions may be (pre-)formed without or with little need for manual trimming.

[0010] In an embodiment of the invention, the preparation of a sample block comprises embedding a microscope sample in an embedding medium in an embedding mold, thereby providing a comprehensive process including all mutually coordinated steps required for advantageous sample preparation.

[0011] According to one embodiment of the invention, the embedding mold has an undivided internal space, a first compartment and a second compartment, the first compartment and the second compartment extending from and communicating with the undivided internal space, and the embedding step comprises placing the sample in the first compartment but not in the second compartment, filling the first compartment, the second compartment and the undivided internal space at least partially with an embedding medium, and hardening the embedding medium, the first surface area being the surface area of ​​the portion of the sample block hardened in the first compartment and the second surface area being the portion of the sample block hardened in the second compartment. The term "hardening" in the context used herein refers to any type of hardening process, including but not limited to solidification, cross-linking, polymerization and crystallization. In such an embodiment, the sample can be positioned particularly reliably without the risk of undesired displacement, for example during filling of the mold with the hardening medium.

[0012] In such embodiments, each of the one or more first sections may, among other things, include a portion of the sample (a "sample section" as described above), and each of the one or more second sections may, among other things, not include a portion of the sample (a "dummy section"). Again, such embodiments may, among other things, allow for reliable formation or creation of the "dummy" sections and sample sections with reduced risk of sample rearrangement.

[0013] In an alternative embodiment of the invention, the invention can also include producing a sample block, but the first surface region and the second surface region can be formed as continuous surface regions of the sample block in such an embodiment, thereby eliminating the need for trimming or the use of specially adapted embedding molds.

[0014] In embodiments of the invention, the sample block can be repositioned in one or more directions relative to the blade during creation of the first and second partial ribbons, i.e., in accordance with embodiments of the invention, the first and second partial ribbons (and their respective sections) are not cut in series from the sample block, thus allowing for any arbitrary order and number of sections or partial ribbons.

[0015] In one embodiment of the invention, the microtome is an ultramicrotome, and the first section or sections and the second section or sections are produced as ultrathin sections having dimensions generally known to the person skilled in the art. A corresponding embodiment is particularly advantageous for the methods of transmission or scanning electron microscopy mentioned at the beginning and further described below.

[0016] According to one embodiment of the invention, there is also provided a method of preparing a microscope sample for examination in an electron microscope. The method comprises embedding the sample in an embedding medium to produce a sample block, and sequentially sectioning the sample block using a microtome to produce a section ribbon, in particular as described above or similarly. In such an embodiment, the section ribbon is produced to have one or more first sections of the sample block that include a portion of the sample and one or more second sections of the sample block that do not include a portion of the sample. According to a corresponding embodiment, the embedding step is carried out using an embedding mold having an undivided interior space, a first compartment, and a second compartment, the first compartment and the second compartment extending from and communicating with the undivided interior space. The embedding step comprises placing the sample in the first compartment but not in the second compartment, at least partially filling the first compartment, the second compartment, and the undivided interior space with the embedding medium, and hardening the embedding medium. According to this embodiment, the sequential sectioning includes forming one or more of the first sections from the portion of the sample block that has hardened in the first compartment, and forming one or more of the second sections from the portion of the sample block that has hardened in the second compartment. For specific advantages of such an embodiment, see the description provided above. These advantages include, as discussed above, reliable positioning of the sample in the mold without risk of undesired dislocation.

[0017] According to one embodiment of the invention, the section ribbon is suspended on the liquid surface during the formation of the continuous sectioning, and one or more of the first sections (or first partial sections) are pushed forward on the liquid surface by a transport distance to a target position on the liquid surface. The forward pushing comprises forming a plurality of the second sections (and thus second partial sections) on the section ribbon after forming the one or more first sections, with a cumulative length corresponding to the transport distance. The method can also be performed partially or fully automatically or based on user settings on the ultramicrotome. In particular, the method comprises fishing the one or more first sections out of the liquid surface using a sample carrier at a target position after forming a plurality of parallel section ribbons in a comparable manner. The pushing method according to such an embodiment can therefore be integrated into known workflows that include corresponding steps.

[0018] In particular, and in one embodiment of the invention, the sample block is mountable on the microtome such that the portion of the sample block formed in the first compartment is initially positioned vertically below and in a common vertical plane with the portion of the sample block formed in the second compartment. In such an embodiment, the sample block advantageously does not need to be repositioned laterally between forming different sections.

[0019] As will be shown in more detail below and envisioned according to one embodiment of the present invention, by forming the embedded first and second sections with different dimensions, sectioning the portion of the sample block formed in the second section can produce sections having different dimensions in the cutting direction compared to cutting the portion of the sample block formed in the first section. If a section having a larger dimension in the cutting direction is formed from the portion of the sample block corresponding to the second section (or the portion of the sample block not containing the sample), this can create a larger "dummy" section, thereby allowing the first section to be advanced more quickly with a relatively small amount of cutting action.

[0020] According to an embodiment of the present invention, a microtome is provided that is configured to perform the method according to any of the preceding claims. There is also provided a microtome having a blade and a sample holder and configured to produce a section ribbon from a sample block accommodated in the sample holder, the microtome being configured to produce the section ribbon such that the section ribbon has a first partial ribbon with one or more first sections of the sample block and a second partial ribbon with one or more second sections of the sample block, the microtome being configured such that the first partial ribbon is produced from a first surface area of ​​the sample block and the second partial ribbon is produced from a second surface area of ​​the sample block, the second surface area being different from the first surface area, and the microtome being configured to retract the sample block from the blade during the production of the first partial ribbon and the second partial ribbon. For further features and advantages of a microtome formed according to an embodiment of the present invention, please refer to the above description related to the method and its embodiments.

[0021] In one embodiment, the sample holder of the microtome is configured to accommodate exactly one sample block, thus allowing the microtome to be particularly easily constructed depending on the different configurations of the microtome.

[0022] In one embodiment, the microtome comprises a control unit configured to provide control commands based on a process definition provided prior to the production of the one or more first sections and the one or more second sections, the process definition comprising a sequence in which the one or more first sections and the one or more second sections (and thus the first and second partial ribbons) are produced, thereby enabling a largely automated production of the first and second partial ribbons according to a predefined process, in particular based on known dimensions of a water bath in which the section ribbons are suspended.

[0023] The present invention also provides an embedding mold adapted for use in the method described above in the different embodiments, i.e. the method of preparing a microscopic sample for examination in an electron microscope. The embedding mold has an undivided internal space, a first compartment and a second compartment, said first compartment and said second compartment extending from and communicating with said undivided internal space. For further advantages and embodiments related to such embedding molds, see the above description.

[0024] According to one embodiment of the invention, in the embedding mold, at least a part of the above-mentioned undivided inner space may be cylindrical and may have an inner diameter of 2 to 15 mm, for example 5 to 10 mm, in particular about 8 mm. At least the cylindrical space, but also all other parts of the mold, may be surrounded by a wall made of a suitable plastic material, which wall in particular has a thickness of 0.1 to 0.5 mm. The embedding mold may have a peel-off tab and a peel-off track for releasing the sample block formed in the embedding mold after the sample block has hardened. This allows the embedding mold to be produced and handled in a particularly economical and easy-to-handle manner.

[0025] The embedding mold may in one embodiment have a particularly flat bottom, and the first and second compartments may be formed at least partially in the form of a depression in the flat bottom. The depression may in particular be formed as a conical or pyramidal frustum for maximum stability and cuttability. In the embedding mold according to an embodiment of the invention, the first and second compartments may have a portion separated by a dividing structure formed in the embedding mold.

[0026] According to an embodiment of the invention, the first and second sections may be formed with different sizes or have different cross sections in a common plane, which is in particular perpendicular to the longitudinal axis of the undivided interior space. In particular, a line in such a common plane crosses the first and second sections, the length of said cross between this line and the first section being shorter than the length of said cross between this line and the second section. The line in particular corresponds to the above-mentioned perpendicular direction of cutting in the above-mentioned step. Thus, in such a configuration, larger (in the sense of area) or at least longer second or "dummy" sections can be formed, and the same cumulative length in the section ribbon can be reached with fewer cutting operations.

[0027] Another advantage of forming the first and second compartments with different dimensions or different cross-sections is that the blank section and the section with the sample are easily distinguishable with the naked eye when handling the sample block. If the sample is placed in the smaller compartment, the user can later distinguish between the blank and sample compartments without optical assistance.

[0028] The present invention will now be further described with reference to the accompanying drawings, in which embodiments of the invention are illustrated. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 shows a schematic representation of a microtome that can be used in accordance with one embodiment of the present invention. [Diagram 2] FIG. 1 shows a schematic representation of an embedding mold according to one embodiment of the present invention. [Diagram 3] FIG. 13 is a schematic diagram of an embedding mold according to another embodiment of the present invention. [Figure 4] FIG. 2 illustrates, in a simplified manner, the steps of a method according to one embodiment of the invention. [Diagram 5] 5A-5C are diagrams illustrating a cutting operation in a method according to another embodiment of the invention; [Figure 6] FIG. 1 shows a schematic diagram of a method according to one embodiment of the invention. [Figure 7] FIG. 2 is another diagram illustrating in a flow chart a method according to an embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] In the drawings, elements of the same function or technical implementation are indicated with the same reference numerals and repeated description is omitted only for the sake of brevity. Descriptions regarding device elements are applicable to the corresponding steps and vice versa.

[0031] FIG. 1 illustrates a simplified side view of a microtome 100 according to one embodiment of the present invention.

[0032] The microtome 100 can in particular be designed as an ultramicrotome in the illustrated embodiment, the operation of which can be controlled using any type of control unit 150 known in the art. The control unit 150 can in particular be formed as a calculation and evaluation unit connected to the ultramicrotome 100 via a wired or wireless communication link as indicated by the double arrow. Contrary to what is explicitly shown, the control unit 150 can also be accommodated in the microtome 100 or in its housing, or in a personal computer system or workstation.

[0033] The ultramicrotome 100 has a sample holder 108 attached to a sample arm 104, which allows the movement of a sample block 700 attached to the sample arm 104, as indicated by arrows 10a-10d, so as to cut the sample in a "cutting window" 10e. Cutting in the ultramicrotome 100 may in particular comprise the advancement of the sample block 700 in the illustrated horizontal direction 10a towards the blade 304 of the ultramicrotome 100, the movement of the sample block vertically downwards in a direction 10b perpendicular to the blade edge of said blade 304, and then the retraction of the sample block in the horizontal direction 10c, and the upward movement of the sample block in the direction 10d so as to be able to restart the process. Together, these movement movements form a "rocking" movement and the advancement and retraction in several steps, in particular in an amount that avoids collisions, the advancement by 10a additionally having an amount of advancement corresponding to the desired section thickness.

[0034] As explained above and further below, according to embodiments of the invention involving the creation of first and second partial ribbons, the sample block 700 is retracted during the creation of the first and second partial ribbons, and optionally during the creation of their respective sections, so that any order and number of first and second sections, or any length and order of partial ribbons, can be created. This is an essential advantage of embodiments of the invention over prior art methods, such as those disclosed in US2015 / 0135917, in that the "sample" and "dummy" sections, when created from the same sample block, such as sample block 904 in US2015 / 0135917, are always cut in a single cutting operation without retraction and are therefore connected, whereby the order of fixation of the "sample" and "dummy" sections is mandatory.

[0035] The downward movement by 10B is preferably performed at different speeds, as further described below, such that the sample block 700 approaches the blade 304 relatively quickly in a first phase of the downward movement, after which the sample block 700 is cut at a desired slower cutting speed in a second phase, and then again moves away from the blade 304 in a third phase, again at a speed higher than the cutting speed.

[0036] The sample arm 104 is connected to a movement unit integrated into the housing 102, which may be known per se and will therefore not be described in detail. Manual adjustment or manipulation of the ultramicrotome 100 can be performed using the handle 110 and another handle that is not individually labeled. The operation of the ultramicrotome 100, i.e. the formation of sections, can be observed using a viewing microscope 106.

[0037] The blade unit 300 is shown greatly enlarged and illustrated in cross section. Ultrathin sections are produced in each cycle indicated by arrows 10a-10d using the blade 304 of the blade unit 300. As will be explained in more detail with reference to the following figures, the sections produced accordingly adhere to each other and form a section ribbon, which is suspended on a liquid surface 306 formed in the liquid bath 302, which also holds the blade 304. A transfer element 400 can be lowered and raised in the liquid to "fish" the section ribbons from the liquid bath 302 and transfer them to the electron microscope.

[0038] The ultramicrotome 100 may include a cooling chamber, shown by dotted lines in FIG. 1, as well as any other devices, such as illumination devices, temperature control devices, and the like, as are commonly known in the art.

[0039] The ultramicrotome 100 can in particular be used to generate section ribbons for use in ssSEM, as mentioned at the outset and as described in further detail, for example, in Serial Section Scanning Electron Microscopy (S3EM) on Silicon Wafers for Ultra-Structural Volume Imaging of Cells and Tissues by Horstmann, H. et al. PLoS ONE 7(4), 2012, e35172, i.e. high-resolution three-dimensional (3D) imaging of tissue microstructure can be performed on the basis of the sections. This is possible using ssSEM, in contrast to ssTEM, described below, which allows the examination of limited subcellular volumes, but rarely allows complete microstructural reconstruction of larger volumes, whole cells or whole tissues. However, embodiments of the invention are not limited to either ssTEM or ssSEM, as already mentioned at the outset.

[0040] In ssSEM, as the name suggests, serial sectioning of tissues is combined with scanning electron microscopy (SEM), in particular using a conductive wafer as support. In ssSEM, section ribbons with up to several hundred sections, e.g. 35 nm thick, can be produced using an ultramicrotome 100 as shown, and then imaged with a lateral pixel resolution of e.g. 3.7 nm in the wafer, which is transferred by a transfer element, such as the transfer element 400 shown in FIG. 1. In ssSEM, electrons backscattered from the sections are generally recorded by a detector in the objective lens of the SEM ("in-lens detector"). The images resulting from such a method are qualitatively comparable to those of conventional TEM images. The main advantage of ssSEM is that it can be used to reconstruct relatively large structures, e.g. in the 2-3 orders of magnitude cubic micrometer range, as mentioned above.

[0041] The method of ssTEM is described, for example, in Harris, KM et al., Uniform Serial Sectioning for Transmission Electron Microscopy, J. Neurosci, 26(47), 2006, 12101-12103. Although representing a more conventional method, ssTEM may be superior to other methods for reconstructing three-dimensional sample information, such as confocal microscopy, especially due to its high resolution.

[0042] The sample is prepared in a known manner for processing for methods such as ssSEM and ssTEM, for example embedded in agarose or a suitable plastic to form a sample block 700. From the embedded sample, by adjusting suitable feed rates, section ribbons are produced using an ultramicrotome, such as ultramicrotome 100, as shown in FIG. 1, in which the individual sections are attached to one another, "attached" referring to relatively weak bonds at the edges of the sections, but not to continuous material bonds. The section ribbons thus produced are initially still attached to the blade, but can float in the liquid bath, from which they are removed ("fished") by a suitable transfer device (a so-called slot grid, or in the case of ssSEM, a wafer) for subsequent examination, as shown diagrammatically by transfer element 400 in FIG. 1. It is also possible not to allow the produced section ribbons to float in the liquid bath, but to transfer them directly instead to a suitable support or transfer element, for example a wafer.

[0043] The position of a single section in the examined object corresponds to its position in the generated section ribbon and vice versa. It is therefore crucial in the corresponding procedure to generate an uninterrupted and as long as possible section ribbon in this way, in order to be able to show the position of the individual sections in the overall sample, or in this section ribbon, preferably, all sections can be imaged, without some being lost for any reason. However, this is not always borne out, for example, by certain embedding materials. For long section ribbons, correspondingly long liquid baths or transport devices are required, and the handling of the sections becomes more difficult. Furthermore, the targeted generation of section ribbons generally proves to be not simple in practice, requiring skill and long-term training.

[0044] When using a liquid bath, one way of producing multiple section ribbons is to use a handling tool (classically an eyelash) to detach the currently attached section ribbon from the microtome blade after each desired number of sections and deliver it to an area of ​​the liquid bath that does not interfere with the cutting of subsequent ribbons. When a sufficient number of section ribbons have been produced in this way, the transfer device is slowly lifted upwards and out of the liquid. The liquid is allowed to flow out, resulting in a section ribbon attached to the transfer device. Typically, up to about 200 sections can be produced in this way. If a liquid bath is not used, this description applies accordingly.

[0045] A disadvantage of the corresponding process is that the sections of the section ribbon often do not adhere reliably to each other, especially when manipulated by an operator. Thus, for example, ribbon parts can break apart on the liquid surface, so that they are then no longer assigned to the cutting sequence. Furthermore, a bending of the corresponding section ribbon can often be observed, so that the section ribbon comes into contact with edge structures or with other ribbons. As a result, the obtained fragments can tear and break apart. If a liquid bath is used, when the section ribbons or their fragments come into contact with the liquid boundary, they are not deposited reliably or at all on the transfer device, but preferentially remain attached to the liquid boundary. Thus, sections can be lost. Another disadvantage is that in the described manner, only a low filling rate of the transfer device can be achieved. This is generally at most 10%, so that frequent transfers are necessary in the corresponding process. Furthermore, manipulation with a manipulation tool is risky, since it can damage the ribbon. In particular, tears and / or holes or wrinkles can occur.

[0046] An alternative method, described for example in U.S. Patent Application Publication No. 2015 / 0135917, is to form one or more section ribbons, in which the last section produced is successively attached to the microtome blade, while the previously produced sections float on the liquid surface as part of the section ribbon and are gradually pushed forward and away from the blade as new sections are joined and added to the ribbon, thus stretching.

[0047] In this way, if several parallel section ribbons are formed, up to 300 sections can be produced. In this context, as also described in US Patent Application Publication No. 2015 / 0135917, the section ribbon is scooped out of the liquid using a suitable transport device. However, such a transport device has a peripheral area that is not available for subsequent observation, so that the sections located in the peripheral area are lost for subsequent examination, and only the sections positioned closer to the center can be used. In other words, in order to be able to analyze the sections of interest in a later step, they need to be positioned at a certain distance from the blade. This is generally achieved, as already mentioned at the beginning, by using so-called "pusher", "release", "dummy" or "blank" sections (these terms are used synonymously in this specification), which have the sole purpose of extending the section ribbon and thus pushing the section of interest into the central area of ​​the transport device.

[0048] Since such release sections would consume valuable sample material in some circumstances, they are generally formed from a portion of the sample block that does not contain the sample or valuable parts thereof. The correspondingly used blank sections are lost for the actual examination because they are outside the transport device or wafer or their visible area. If the release sections were to be taken from an area containing a sample, the production of the release sections would not allow continuous sectioning over a larger sample area, since the series of sections of interest would be repeatedly interrupted by release sections required for positioning, which would be missed in the subsequent test. One embodiment of the invention provides advantages over the prior art methods, since it not only proposes to produce the sample section and the "pusher" section from the same sample block, which respectively form the first and second partial ribbons containing at least one sample section or pusher section, but also allows the production of the first and second sections or partial ribbons in any desired order and independently of each other, since, as described above, the sample is retracted from the blade in between.

[0049] In more general terms as used previously, the section ribbon can be produced in an embodiment of the invention to have a first partial ribbon with one or more first sections of the sample block and a second partial ribbon with one or more second sections of the sample block, where the first or second sections may not have a sample and therefore may be used specifically as "pusher" sections. In an embodiment of the invention, the first partial ribbon is produced from a first surface area of ​​the sample block and the second partial ribbon is produced from a second surface area of ​​the sample block, where the second surface area is different from the first surface area. As explained below, the first and second surface areas may be surface areas of portions of the sample block formed in different sections of the embedding mold, but they may be formed from a common precursor surface area by trimming. In contrast to such an embodiment where the first and second surface areas are discontinuous (either by producing them in a correspondingly adapted mold or by trimming), in yet another embodiment of the invention, the surface areas may be continuous areas that are repositioned relative to the blade of the microtome. In the following we turn to a description of the former alternative, namely how the first and second surface regions are discontinuous because they are produced in a suitable mould.

[0050] In Figures 2A and 2B as well as in Figures 3A-3C an embedding mould 500 according to a particular embodiment of the invention is shown in a longitudinal view (Figures 2A and 3A) and in a bottom view (Figures 2B, 3B and 3C). In each case, the embedding mould 500 has a substantially cylindrical common internal space 506 surrounded by a wall 502 and optionally covered by a lid 504. From the internal space 506 extend compartments 508 and 510 which are connected to the internal space 506. The internal space 506 and the compartments 508, 510 may be filled with a hardenable embedding medium 512 in the embedding mould 500. The compartments 508, 510 can be further divided by a dividing element 509, although this is not necessary in the embodiments of the invention, particularly in the embodiment shown in Figures 3A-3C.

[0051] Although there are many commercially available embedding molds that can be commonly used in the above-mentioned method, these conventional embedding molds have certain disadvantages compared to the embedding mold 500 according to an embodiment of the present invention. Prior art embedding molds are generally cylindrical and may have a tapered tip to reduce the subsequent preparation work, i.e. to reduce the amount of material to be cut off. However, embedding of a microscope sample in this type of embedding mold, as in an embodiment of the present invention, essentially consists of placing the sample in the internal space of the embedding mold, filling said internal space with a suitable type of embedding medium, which in the field to which the present invention relates is referred to as a "reboning" embedding medium, such as polyester wax or epoxy material, and hardening said embedding medium in the mold to form a "sample block", such as the sample block 700 shown in FIG. 1. According to an embodiment of the present invention, such a sample block may be provided with discontinuous surface areas to allow independent cutting operations, in any order and in any number, independently in each surface area of ​​the sample block 700.

[0052] After removing the sample block 700 from the mold (for which the mold may have a predetermined break point or cut-off strip), in the prior art method and in the method according to the embodiment of the present invention, the formed sample block 700 may be subjected to a "trimming" step in which excess embedding medium may be removed in order to adapt the cut area to the dimensions of the ultramicrotome blade. The trimming operation may be reduced by using tapered embedding molds, i.e. embedding molds with a "tip" where the sample can be placed, which may then be surrounded by a relatively small amount of embedding medium that is cut off. Multi-well embedding molds, which are partially similar to multi-well sample plates, are also known. Multi-well embedding molds have a number of individual embedding molds as described hereinbefore in a common support by which the multi-well embedding molds can be combined to form or into which the multi-well embedding molds can be inserted.

[0053] However, none of the embedding molds according to the prior art allow a clear local separation of the specimen from the area where blank sections can be made for positioning. Essentially, currently available molds are designed in such a way that the sample material is positioned in an almost undefined location, which can be in the center or on the periphery of the interior space of the embedding mold. In other words, according to the prior art, the sample is not limited to a specific area in the sample mold, and the operator does not have the possibility to predefine the areas where sample sections can be formed on the one hand and blank sections on the other hand. This can significantly complicate the formation of blank sections for positioning.

[0054] US 2015 / 0135917, already mentioned above, discloses the formation of blank sections from embedding material without samples. In a first embodiment, different sample blocks are used, one containing a sample and the other completely free of sample. And in a second embodiment, areas of a single sample block are kept free of sample, such areas producing blank sections when sectioned. However, in the first embodiment, the ultramicrotome is required to be able to hold multiple sample blocks, and in the second embodiment, the positioning of the sample material is often tricky, since there is no structural separation of the different areas and the material may still exit from the desired position. Moreover, according to such conventional methods, the order of "sample" and "dummy" sections is strongly restricted to alternating when they are produced from a single block. Both problems can be overcome by using the embedding molds provided according to embodiments of the invention and the methods according to embodiments of the invention in which they are used.

[0055] As shown in Figures 2A and 2B, the compartments 508, 510 can be formed as two halves of a split tip of the embedding mold 500, whereas as shown in Figures 3A, 3B and 3C, they may also be formed as truncated pyramids (pyramidal frustum) extending from the bottom of the embedding mold 500. The sample 600 is placed in a first compartment 508 of the compartments 508, 510, whereas a second compartment 510 of the compartments 508, 510 remains empty, i.e. it is filled only with an embedding medium 512. The first and second surface areas formed by said frustums are surrounded by dotted lines (not a structural feature) and are indicated as 703 and 705.

[0056] As shown in Fig. 3C, the sections 508, 510 may be formed with different dimensions and have different cross sections in a common plane corresponding to the paper. A line in said common plane or parallel to the paper, shown as a dashed line in this figure, crosses the first section 508 and the second section 510 such that the cross length in the first section 508 is shorter than the cross length in the second section 510. If the sample block formed in the embedding mold 500 is cut in a direction corresponding to said line, as will be shown below, a larger section without a portion of the sample 600 and a smaller section including a portion of the sample 600 can be formed. Again, the first and second surface areas formed by frustums of different dimensions are surrounded by dashed lines (not structural features) and are indicated at 703 and 705. They are likewise formed with different dimensions in the illustrated embodiment.

[0057] Thus, in a corresponding embodiment of the present invention, an embedding mold 500 is used in which the sample material and the blank material are kept separate by technical means, i.e. by material barriers between separate compartments or receptacles, or separate protrusions are formed. Thus, there are predefined positions of the sample and the blank, and the basic condition required for automatic section ribbon production, in particular for 3D TEM examination, i.e. separate sample and blank sections, is fulfilled. The embedding mold used according to the present invention significantly reduces the loss of sample material due to sections that cannot be used to automatically produce serial sections for 3D TEM reconstruction, i.e. are used only for positioning.

[0058] According to such an embodiment of the invention, the basic idea of ​​using the embedding mold 500 is to position the sample in a separate or defined receptacle that is locally separated from a receptacle for a second sample or simply empty embedding material. Thus, in general, when referring to "one" first compartment or "one" second compartment, there may be at least one other compartment that is similar to the first compartment and has the purpose of the first compartment, and at least one other compartment that is similar to the second compartment and has the purpose of the second compartment.

[0059] Compared to forming multiple distinct sample blocks as in the prior art, for example as in the corresponding embodiments of U.S. Patent Application Publication No. 2015 / 0135917, a significant advantage of using mold 500 as described is the reduced preparation and installation time, with corresponding improvements in ease of use, reliability and reproducibility, by producing and using only one sample block 700. As noted above, in contrast to the prior art, the sample can be more reliably positioned according to embodiments of the present invention, since a mechanical barrier between the compartments is present in embedding mold 500.

[0060] However, it should be noted that another embodiment of the invention may involve the use of embedding moulds of different types, in particular of the conventional type, where no different compartments are provided as described above. In such an embodiment, a "precursor" sample block may be formed in which the sample and blank areas are not yet physically separated, i.e. the surface area from which the different sections are ultimately made is a continuous precursor area. In such a case, the creation of the sample block may comprise trimming the precursor sample block to form the surface area from which the sections are taken. The shape of the sample block resulting from said trimming may correspond to the shape of the sample block formed by the compartmentalized mould. In yet another embodiment of the invention, when the surface area from which the sections are made is provided as a continuous surface area of ​​the sample block, these surface areas may be positioned alongside one another, in particular parallel to the edge of the blade, and the sections can be formed therefrom by laterally repositioning the blade.

[0061] Returning to the embedding mold 500 with compartments as formed according to an embodiment of the invention, the hardening of the embedding medium 512 in the embedding mold 500 forms a sample block 700 as shown in Figures 4A-4D, which can in particular be produced using an embedding mold as shown in Figures 3A and 3B. Figures 4A-4D further show steps of a method according to one embodiment of the invention, with Figures 4A and 4B showing side views corresponding to the side view of Figure 1, and Figures 4C and 4D showing a perspective view along the length of the ultramicrotome 100 from a position above it shown in Figure 1 and rotated by 90°. Neither the figures nor the elements shown therein are drawn to scale. This in particular concerns the sections, the thickness of which is greatly exaggerated for clarity. The movements already shown and described in relation to Figure 1 are also shown here and are indicated by the arrows 10a-10d and the cutting window 10e in Figures 4A and 4B.

[0062] As shown in FIG. 4A, by moving the sample holder 108 as described above and as indicated by the arrows 10a-10d, sections 802 can be formed from the portion 702 of the sample block 700 corresponding to the first section 508 containing the sample 600. Each of these sections 802, previously referred to as the "first" section, therefore contains a portion of the sample 600. A correspondingly formed section ribbon, initially comprising only the "first" section 802 according to FIG. 4A, i.e. the section 802 having a portion of the sample 600, is indicated at 800 and was previously referred to as the "first partial section". During sectioning, by relative lateral movement between the sample block 700 and the blade 304, a plurality of section ribbons 800 can be formed, which sections are attached parallel to the blade 304 and are each formed as described above.

[0063] After forming the first plurality of slices, the portion 702 of the sample block 700 corresponding to the first section 508 containing the sample 600 is substantially shortened, as shown in an exaggerated manner in FIG. 4B. As a result, the portion 704 of the sample corresponding to the second section 510 where no sample is present is accessible to the blade. That is, the portions 702 and 704 are initially of the same size in this example, and the portion 702 is shortened by making the slice. However, this embodiment can also be used in connection with sample block portions of different dimensions, for example as shown in FIG. 3C. Thus, as shown in FIG. 4B, slices 804 can be formed from the portion 704 of the sample block 700 corresponding to the second section 510 not containing the sample 600, by moving the sample holder 108 as described above and as shown by the arrows 10a-10d. Thus, each of these slices 804, previously referred to as the "second" slice and forming a "second sub-slice", can be used to position the slice 802 containing a portion of the sample. Thus, the section ribbon 800 is extended by the second section 804 from the side of the blade 304, so that the section 802 can be positioned in the transfer element 400. Again, during sectioning, the relative lateral movement between the sample block 700 and the blade 304 can result in the multiple section ribbons 800 being extended accordingly, which are attached parallel to the blade 304.

[0064] Forming two section ribbons 800 including a first section 802 and a second section 804, the first section 802 including the portion 602 of the sample 600, is again shown in perspective in Figures 4C and 4D, where the portions 702 and 704 of the sample block are shown for reasons of simplicity as if the respective other portions 704, 702 were not present. Not all identical elements are numbered. As shown, by extending the section ribbon 800 by the second section 804, i.e. forming a second partial section, the first section 802 in the first partial section can be positioned to correspond to the window 402 of the transfer element 400.

[0065] In an embodiment of the present invention in which an embedding mold 500 having a first section 508 and a second section 510 is used, the formation of one or more first sections 802 or corresponding first partial ribbons is particularly preceded by positioning of a portion 702 of the sample block 700 formed in the first section 508 so that the portion 702 can be cut by the blade 304 of the microtome 100 being used, and the formation of one or more second sections 804 or corresponding second partial ribbons is particularly preceded by positioning of a portion 704 of the sample block 700 formed in the second section 510 so that the portion 704 can be cut by the blade 304 of the microtome 100. In either case, the formation of the sections comprises, as shown in particular in Figures 4A-4D, a horizontal advance of the sample block 700 towards the blade 304 of the microtome 100, a vertical downward movement of the sample block 700 in a direction perpendicular to the blade edge of the blade 304, and then a retraction of the sample block 700 in the horizontal direction and an upward movement of the sample block 700 so that the process can be restarted in steps, which together form a "rocking" movement. The retraction is particularly performed during the formation of a first and a second partial ribbon, each having an arbitrary number of first and second sections 802 and 804. Substantially the same applies when trimming is performed to create discontinuous surface areas 703, 705.

[0066] The advancement and retraction indicated by arrows 10a and 10c is in particular performed in an amount and over a large distance to avoid collisions of the sample carrier 108 or parts of the sample block 700 with the blade 304 and other parts of the microtome 100, the advancement 10a additionally having an advancement in an amount corresponding to the desired section thickness. The downward movement indicated by arrow 10e is preferably performed at different speeds during the movement, so that in a first phase of the downward movement the sample block approaches the blade 304 at a relatively high speed, then the block 700 is cut in a second phase at a slower desired cutting speed, such as 1 mm / s, and after each actual cut the sample block 700 moves away from the blade in a third phase of the movement again at a speed higher than the cutting speed.

[0067] In an embodiment of the invention, each of the movements as indicated by arrows 10a-10c may include a particular range of movement, with the movements indicated by arrows 10b and 10d including a range of 0.1 mm to 5 mm, preferably 0.2 to 2 mm, and the movements indicated by arrows 10a and 10c including a range of 0.1 mm to 0.5 mm, preferably 0.2 to 0.3 mm.

[0068] The two portions 702, 704 of the sample block can be initially cut to a common length using the microtome 100 in this regard, regardless of whether they are formed in the sections 508, 510 of the sample mold 500 or by trimming. Thereafter, a first section 802 of one or more section ribbons 800, and thus a first partial ribbon, can be formed. That is, in a first lateral position of the blade 304 relative to the sample block 700, the first section 802 of the first ribbon 800 can be formed, and then the lateral position of the blade 304 relative to the sample block 700 can be changed so that the first section 802 of the second section ribbon 800, and thus another first partial ribbon, can be formed. Both the first section ribbon and the first section 802 of the second section ribbon 800 are attached to the edge of the blade 304 and extend therefrom in parallel. An additional section ribbon 800 including the first section 802, and thus a first partial ribbon, can be formed in this manner. Changing the relative position between the blade 304 and the sample block 700 may involve moving the blade 304, or a structure supporting the blade, the sample block 700, or both, in a direction substantially parallel to and corresponding to the edge of the blade 304.

[0069] Absolute and / or relative spatial designations used anywhere in this disclosure, such as "above", "below" and "beside", in particular refer to the spatial arrangement of the correspondingly designated elements, such as portions 702, 704 or surface areas 703, 705 of sample block 700. By an arrangement of two elements where one element is arranged "below the other", in particular is understood an arrangement where the upper end of the lower element of these two elements is at a lower geodetic height than or at the same geodetic height as the lower end of the upper element of the two elements, and where the projections of the two elements on the horizontal plane overlap.

[0070] After one or more section ribbons 800 or ribbon portions have been formed, each of which includes only a first section 802, the portion 702 of the sample block formed in said first section 508 or trimmed accordingly and including the sample is shortened, and optionally can be shortened further, by an amount corresponding to the cumulative thickness of the first sections 802 in said horizontal direction. Thus, the portion 704 of the sample block 700 formed in said second section 510 is accessible to the blade 304 and can be moved into a cutting position. Thus, these section ribbons 800, or each of these ribbons of sections 800, can be extended by forming a second section 804, i.e. a second partial ribbon, or in other words by attaching the second section 804 to the beginning of the section ribbon 800, which previously had only the first section 802.

[0071] Thus, in an ultramicrotome usable according to the invention, portions of a sample block formed in a first section and a second section are positionable vertically above one another, in other words, the sample block is mounted on the microtome such that the portion of the sample block formed in the first section is initially positioned vertically below and in a common vertical plane with the portion of the sample block formed in the second section.

[0072] However, it should be noted that the method just described represents only one of several embodiments of the present invention, including the specific placement of portions of the sample block on top of one another. In another embodiment, for example, an ultramicrotome blade mounted at a predetermined distance or angle relative to the liquid reservoir can be used to create a specific distance between the sample block and its portions and the reservoir.

[0073] Figures 5A-5C show a cutting operation performed by sample block 700 in accordance with an embodiment of the present invention, with individual cuts indicated by arrows 1 and 2, and looking at sample block 700 from the direction of blade 304 as in Figures 2B, 3B and 3D, and therefore for the reference numbers used in Figures 5A-5C, please refer to Figures 2B, 3B and 3D.

[0074] 5A-5C, three cutting operations 1 are performed in the first surface region 703 of the sample block 700 and one cutting operation 2 is performed in the second surface region 705 of the sample block 700, but these numbers can be varied in any manner deemed useful for forming the "sample" and "dummy" sections (first and second sections and first and second partial ribbons). For example, surface region 703 may include a portion of the sample 600 and surface region 705 may not include a portion of the sample, or vice versa, such that embodiments of the invention may cut either of surface regions 703, 705 to create "sample" and "dummy" sections in the partial ribbons in any number and order, which is a particular advantage of the invention.

[0075] That is, a first partial ribbon including a "first" or "sample" section 802 can be made from one of the surface areas 703, 705 of the sample block 700 (which in this case can be referred to as the "first" surface area), and a second partial ribbon including a "second" or "dummy" section 804 can be made from another surface area 703, 705 (which in this case can be referred to as the "second" surface area).

[0076] As already shown in FIGS. 4A-4D, which are essentially similar to FIG. 5A, the discontinuous surface regions 703, 705 are cut by the blade 304 of the microtome 100 to form a first section 802 and a second section 804, which are arranged vertically above one another, i.e. along a line transverse to the direction of the edge of the blade 304, which is horizontal in the views of FIGS. 5A-5C. As shown in FIG. 5A, the first three sections are made from the surface region 703 using cutting operation 1, and then one section is made from the surface region 705 using cutting operation 2. At least between cutting operations 1 and 2, i.e. during the making of the respective sections or partial ribbons from the surface regions, the sample block 700 is retracted from the blade 304. The order of forming the first and second sections as well as their number are therefore freely selectable according to an embodiment of the invention.

[0077] In Fig. 5B, a cutting according to an alternative embodiment of the invention is shown diagrammatically. Here too, the discontinuous surface areas 703, 705 are cut by the blade 304 of the microtome 100 to form a first section 802 and a second section 804, which according to Fig. 5B are arranged alongside one another, i.e. along a line parallel to the direction of the edge of the blade 304, which is horizontal in the views of Figs. 5A-5C. In this embodiment, the sample block 700 is retracted from the blade 304 between cutting movements 1 and 2 and additionally repositioned laterally. Also, in such an embodiment, in contrast to the methods according to the prior art, the order in which the first and second sections are formed as well as their number are freely selectable.

[0078] 5A and 5B, the first surface region 703 and the second surface region 705 are formed as discontinuous surface regions of the sample block 700, either using a suitable embedding mold or by corresponding trimming as described above, whereas FIG. 5C illustrates one embodiment in which the first surface region 703 and the second surface region 705 are formed as continuous surface regions of the sample block 700. Cutting operations 1 and 2 can be performed substantially as previously described for FIG. 5B, i.e., by retracting and additionally laterally repositioning the sample block 700 from the blade 304 between cutting operations 1 and 2.

[0079] FIG. 6 illustrates, in a flow chart, a method 900 according to one embodiment of the present invention.

[0080] As previously reiterated, a method 900 is provided for preparing a microscopic sample 600 for examination in an electron microscope, comprising a step 902 of embedding said sample 600 in an embedding medium 512 producing a sample block 700, and a step 906 of serially sectioning said sample block 700 using a microtome 100 producing a section ribbon 800, as described. The method 900 performs said embedding step 902 using an embedding mold 500, also as described. The method comprises, as generally indicated by a step 904, placing said sample 600 in a first compartment 508 of a mold 500, but not in a second compartment 510, at least partially filling said first compartment 508, said second compartment 510 and the undivided interior space 506 of the mold 500 with an embedding medium 512, and hardening with said embedding medium 512. The sequential sectioning step 906 includes forming the first section 802 from the portion 702 of the sample block 700 that has hardened in the first section 508, and forming one or more second sections 804 from the portion 704 of the sample block 700 that has hardened in the second section 510. In step 908, the correspondingly formed section ribbon 800 may be fished out of the liquid surface 306.

[0081] FIG. 7 shows a schematic flow diagram of a method 1000 according to another embodiment of the present invention.

[0082] In method 1000, a microtome 100 having a blade 304 is used to create a section ribbon 800 from a sample block 700, substantially as described above. As described above, the section ribbon 800 is created to have a first partial ribbon comprising one or more first sections 802 of the sample block 700 and a second partial ribbon comprising one or more second sections 804 of the sample block 700, the first partial ribbon being created from a first surface region 703 of the sample block 700 and the second partial ribbon being created from a second surface region 705 of the sample block 700, the second surface region 705 being different from the first surface region 703.

[0083] The method 1000 may include a step 1002 of fabricating a sample block 700, where the first surface region 703 and the second surface region 705 may be formed as continuous or discontinuous surface regions of the sample block 700. If the first surface region 703 and the second surface region 705 are formed as discontinuous surface regions, the step 1002 of fabricating a sample block 700 may include steps substantially as described above for the method 900 or any other equivalent embodiment as described above, i.e., by using an embedding mold 500 with the sections 508, 510 as described above. In an alternative embodiment, the step 1002 of fabricating a sample block 700 may include forming a precursor block 700 and trimming the precursor block 700 to form discontinuous surface regions 703, 705. Yet another alternative embodiment includes forming a sample block with continuous first surface region 703 and second surface region 705.

[0084] The method 1000 then continues with step 1004 of forming a first ("sample") section 802 of the section ribbon 800 from the sample block 700. In step 1006, it is determined that a target or desired number of first sections 802 have been formed, thus completing the formation of the first partial ribbon. If not, the method returns to step 1004 to form another first section 802, thus extending the first partial ribbon. If a target or desired number of first sections 802 have been formed, the method 1000 proceeds to step 1008 of retracting the sample block 700 from the blade 304 of the microtome 100, with one additional step being performed between each instance of step 1004.

[0085] A subsequent step 1010 forms a second ("blank") section 804 of the section ribbon 800 from the sample block 700. Similar to step 1006 above, a step 1012 determines that a target or desired number of second sections 804 have been formed, thus completing the formation of the second partial ribbon. If not, the method returns to step 1010 to form another second section 804, thus extending the second partial ribbon. If a target or desired number of second sections 804 have been formed, the method 1000 proceeds to step 1014, where it may be determined whether the method 1000 is complete or should be repeated to form another section ribbon 800. [Explanation of symbols]

[0086] 1,2 Cutting action 10a~10b Microtome movement 10e Cutting window 100 Ultramicrotome 102 Housing 104 sample arms 106 Observation Microscope 108 Sample Holder 110 Handle 150 Control Unit 300 Blade Unit 302 Liquid tank 304 Blade 306 Liquid surface 400 Transport elements 500 Embedded type 502 Wall 504 Lid 506 Common interior space 508 Section 1 510 Section 2 509 Division Elements 600 samples 602 Sample part 700 sample block 702 First part of sample block 703 1st surface area 704 Second part of sample block 705 Second surface area 800 section ribbon 802 1st section 802 2nd section 900 ways 902 Embedding step 904 Sample placement, hardening step 906 Serial sectioning steps 908 Fishing Step

Claims

1. A method (1000) of producing a section ribbon (800) from a sample block (700) using a microtome (100) having a blade (304), comprising: producing the section ribbon (800) to have a first partial ribbon comprising one or more first sections (802) of the sample block (700) and a second partial ribbon comprising one or more second sections (804) of the sample block (700); producing the first partial ribbon from a first surface area (703) of the sample block (700) and producing the second partial ribbon from a second surface area (705) of the sample block (700), wherein the second surface area (705) is different from the first surface area (703); retracting the sample block (700) from the blade (304) during production of the first partial ribbon and the second partial ribbon; method (1000).

2. The method further comprises producing the sample block (700), wherein the first surface area (703) and the second surface area (705) are formed as discontinuous surface areas of the sample block (700), The method (1000) according to claim 1.

3. Producing the sample block (700) comprises forming a precursor sample block having continuous precursor areas of the first surface area (703) and the second surface area (705), Producing the sample block (700) comprises trimming the precursor sample block to form the first surface area (703) and the second surface area (705) from the precursor areas, The method (1000) according to claim 2.

4. Producing the sample block (700) comprises forming the sample block (700) using an embedding mold (500) configured to form the first surface area (703) and the second surface area (705), or precursor areas of the first surface area (703) and the second surface area (705), as the discontinuous surface areas, The method (1000) according to claim 2.

5. Producing the sample block (700) comprises embedding a microscope sample (600) in an embedding medium (512) in the embedding mold (500) (902), The method (1000) according to claim 4.

6. The embedded type (500) has an undivided internal space (506), a first compartment (508), and a second compartment (510), the first compartment (508) and the second compartment (510) extending from and communicating with the undivided internal space (506), the embedding step (902) including disposing the sample (600) in the first compartment (508) but not in the second compartment (510), filling at least partially the first compartment (508), the second compartment (510), and the undivided internal space (506) with the embedding medium (512), and curing the embedding medium (512), the first surface region (703) being the surface region of the portion (702) of the sample block (700) cured in the first compartment (508), and the second surface region (705) being the portion (704) of the sample block (700) cured in the second compartment (510). The method (1000) according to claim 5.

7. Each of the one or more first sections (802) includes a portion (602) of the sample (600). Each of the one or more second sections (804) does not include a portion (604) of the sample (600). The method (1000) according to claim 5.

8. The method further includes fabricating the sample block (700), and forming the first surface region (703) and the second surface region (705) as continuous surface regions of the sample block (700). The method (1000) according to claim 1.

9. During fabrication of the first partial ribbon and the second partial ribbon, repositioning the sample block (700) in one or more directions relative to the blade (304). The method (1000) according to claim 1.

10. Using an ultramicrotome as the microtome (100) to fabricate the one or more first sections (802) and the one or more second sections (804) as ultrathin sections. The method (1000) according to claim 1.

11. A method (900) for preparing a microscope sample (600) for inspection in an electron microscope, the method (900) comprising A step (902) of embedding the sample (600) in an embedding medium (512) for producing a sample block (700); A step (906) of continuously sectioning the sample block (700) using a microtome (100) for producing a section ribbon (800); having producing the section ribbon (800) to have one or more first sections (802) of the sample block (700) including a portion (602) of the sample (600) and one or more second sections (804) of the sample block (700) not including the portion (602) of the sample (600); Performing the embedding step (902) using an embedding mold (500), the embedding mold (500) having an undivided internal space (506), a first compartment (508), and a second compartment (510), the first compartment (508) and the second compartment (510) extending from the undivided internal space (506) and being connected to the undivided internal space (506); The embedding step (902) includes placing the sample (600) in the first compartment (508) but not in the second compartment (510), at least partially filling the first compartment (508), the second compartment (510), and the undivided internal space (506) with the embedding medium (512), and curing the embedding medium (512); The step of continuously sectioning (906) includes forming one or more of the first sections (802) from a portion (702) of the sample block (700) cured in the first compartment (508) and forming one or more of the second sections (804) from a portion (704) of the sample block (700) cured in the second compartment (510); Method (900). **Claim 12** While forming, suspending the section ribbon at a liquid surface (306), pushing one or more of the first sections (802) forward at the liquid surface (306) by a transfer distance to a target position at the liquid surface (306), the forward pushing including forming one or more of the first sections (802) in a first partial ribbon and then forming a plurality of the second sections (804) in a second partial ribbon with a cumulative length corresponding to the transfer distance. The method (1000) according to claim 1.

13. The sample block is attached to the microtome (100) such that a portion (702) of the sample block (700) formed in the first section (508) is disposed vertically below a portion (704) of the sample block (700) formed in the second section (510) and in a common vertical plane with the portion (704). The method (900, 1000) according to claim 6 or 11.

14. By cutting the portion (704) of the sample block (700) formed in the second section (510), sections having dimensions different at least in the cutting direction are formed as compared to the cutting of the portion (702) of the sample block (700) formed in the first section (508). The method (900, 1000) according to claim 6 or 11.

15. The different dimension in at least the cutting direction is a larger dimension. The method (900, 1000) according to claim 14.

16. A microtome (100) configured to perform the method according to claim 1 or 11.

17. A microtome (100), wherein the microtome (100) has a blade (304) and a sample holder (108) and is configured to produce a section ribbon (800) from a sample block (700) accommodated in the sample holder (108), the microtome (100) is configured to produce the section ribbon (800) such that the section ribbon (800) has a first partial ribbon with one or more first sections (802) of the sample block (700) and a second partial ribbon with one or more second sections (804) of the sample block (700), the microtome (100) is configured such that the first partial ribbon is produced from a first surface region (703) of the sample block (700) and the second partial ribbon is produced from a second surface region (705) of the sample block (700), and the second surface region (705) is different from the first surface region (703). The microtome (100) is configured to retract the sample block (700) from the blade (304) while producing the first partial ribbon and the second partial ribbon. Microtome (100). **Claim 18** The microtome (100) has a control unit (150) configured to supply control commands based on a process definition provided before producing the section ribbon, the process definition including a sequence in which one or more of the first sections (802) and one or more of the second sections (804) are produced to form the first partial ribbon and the second partial ribbon. The microtome (100) according to claim 17. **Claim 19** An embedding mold (500) adapted to be used in the method (900, 1000) according to claim 1 or 11, wherein the embedding mold (500) has an undivided internal space (506), a first compartment (508), and a second compartment (510), and the first compartment (508) and the second compartment (510) extend from and are connected to the undivided internal space (506). Embedding mold (500). **Claim 20** At least a portion of the undivided internal space (506) is cylindrical and has an inner diameter of 2 to 15 mm. The embedding mold (500) according to claim 19. **Claim 21** At least the internal space (506) is surrounded by a wall (502) made of a plastic material, and the wall (502) has a thickness of 0.1 to 0.5 mm. The embedding mold (500) according to claim 19. **Claim 22** The embedding mold (500) has a peeling tab and a peeling track for opening the sample block (700) formed in the embedding mold (500). The embedding mold (500) according to claim 19. **Claim 23** The embedding mold (500) has a flat bottom, and the first compartment (508) and the second compartment (510) are formed at least partially in the form of recesses in the flat bottom. The embedding mold (500) according to claim 19. **Claim 24** The recess is formed as a conical or frustum-shaped pyramid. The embedding mold (500) according to claim 23. **Claim 25** The first section (508) and the second section (510) have portions divided by a dividing structure (509) formed in the embedded type (500). The embedded type (500) according to claim 19.

26. The first section (508) and the second section (510) are formed with different dimensions or have different cross-sections in a common plane. The embedded type (500) according to claim 19.

27. The common plane is perpendicular to the longitudinal axis of the internal space (506), a line in the common plane crosses the first section (508) and the second section (510), and the length of the crossing with the first section (508) is shorter than the length of the crossing with the second section (510). The embedded type (500) according to claim 26.

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