Abstract:
The invention relates to a tissue sample handling apparatus, in particular for grasping histological samples after infiltration of an embedding medium such as, for example, paraffin, which is characterized in that a sample is immobilizable on the handling apparatus, in particular in a sample holding position, by means of negative pressure.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of German patent application number 10 2011 002 194.9 filed Apr. 20, 2011, the entire disclosure of which is incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The invention relates to a tissue sample handling apparatus, in particular for grasping histological samples after infiltration of an embedding medium such as, for example, paraffin. 
     BACKGROUND OF THE INVENTION 
     When working with histological samples, in particular when preparing histological samples in the context of an embedding process for later microtoming, it is necessary to be able—in particular between individual process steps that as a rule occur at different laboratory locations and/or in different devices—to grasp the samples and set them down again precisely and gently. One of the difficulties existing in this context is that as a general rule the samples are impregnated or at least wetted with liquids, in particular with liquids that solidify at room temperature (for example, paraffin); this greatly complicates handling with the aid of mechanical grasping tools, for example tweezers. In addition, damage to the sample can occur. 
     Merely by way of example, mention is made below of a number of process steps during or between which it may be necessary to grasp samples and set them down again: In the context of the conditioning of histological samples, they are usually first fixed by the application of various chemicals. The tissue liquid originally present in the natural cavities of the sample is thereby replaced, in multiple steps, by a fixing liquid, for example by formalin. In order to convert the fixed samples into a state that permits sectioning by means of a microtome, the fixing liquid is replaced by an embedding medium, for example paraffin, gelatin, agar, nitrocellulose, polyester wax, polyethylene glycol, or plastic. During the aforementioned processes, the samples are usually located in a cassette that comprises a plurality of sieve-like openings so that the chemicals can flow around the samples. A particular embodiment of such a cassette is known, for example, from DE 43 33 118 A1. After infiltration of the embedding medium, i.e. for example paraffin, into the samples, the excess embedding medium is drained off. The samples can then be removed from the cassette. After this step, however, the samples can be located anywhere within the cassette; because of the paraffin residues adhering to them, for example, the samples as a rule adhere to the cassette cover, in the cassette cavity, and/or to one another. Stuck-together clumps of samples often form inside the cassette. This complicates reliable, gentle grasping of the individual samples. 
     Before further processing, in particular before automated, machine-controlled further processing, of the samples, for example before the further step of casting the samples into a paraffin block (called “blocking”), the sample or samples must be present in isolated fashion. Detachment and isolation can be performed, for example, using tweezers; disadvantageously, the risk exists that a sample may be damaged in this context and possibly even become unusable. In particular, the risk exists of unintentionally causing changes to a sample that result in artifacts upon later analysis of tissue sections of the sample. 
     DE 20 2009 017 635 U1 discloses a grasping apparatus for fixing specimens using a fixing agent. This grasping apparatus comprises a heatable and coolable probe. Also provided is a temperature regulation unit for heating and cooling the probe and for regulating the temperature of the probe in a range, the fixing agent exhibiting in that range a change in aggregate state from solid to liquid. Lastly, the paraffin adhering to a histological sample is used as an adhesion medium that, in the hardened (cooled) state, ensures that the sample to be grasped adheres to the probe. The sample can be detached again from the probe by subsequent heating of the probe, and thus re-liquefaction of the paraffin. In practice, this grasping apparatus is difficult to handle, especially because even liquefied paraffin still exerts an (albeit reduced) adhesive effect between the probe and sample. This, in particular, also disadvantageously prevents the use of this grasping apparatus in an automated system. 
     SUMMARY OF THE INVENTION 
     It is therefore the object of the present invention to describe a tissue sample handling apparatus that enables a sample to be grasped and released again efficiently, reliably, and gently. 
     The object is achieved by a tissue sample handling apparatus which is characterized in that a sample is immobilizable on the handling apparatus, in particular in a sample holding position, by means of negative pressure. 
     The invention has the very particular advantage that even samples that are wetted with a liquid, in particular with an embedding medium such as paraffin, can be grasped and set down again securely and gently, in particular without damage. Advantageously, the grasping and setting-down operations function sufficiently securely and reliably that according to the present invention automated handling of samples, in particular e.g. in the context of an automated sample processing procedure such as automated blocking, is also made possible with the tissue sample handling apparatus according to the present invention. 
     In an advantageous embodiment, a regulating apparatus is provided for regulating the negative pressure. For example, according to the present invention the negative pressure can be regulated, preferably automatically, as a function of whether or not a sample is immobilized on the handling apparatus, in particular in a sample holding position. In particular, provision can be made according to the present invention that the negative pressure is decreased, preferably automatically, when a sample is aspirated and immobilized on the handling apparatus, in order to reduce the forces acting on the sample and preferably limit them to the magnitude that is necessary in order to hold the sample on the handling apparatus, for example on an aspiration nozzle. 
     Alternatively or additionally, provision can advantageously be made that a greater negative pressure (lower pressure) is set when no sample is immobilized on the handling apparatus, for example in order to aspirate a sample securely and reliably. A reduction in negative pressure can occur, preferably once again automatically, after aspiration. 
     Especially in the interest of automated sample processing, in a particularly advantageous embodiment of the tissue sample handling apparatus according to the present invention a sensor apparatus is provided which determines whether or not a sample is immobilized on the handling apparatus, in particular in the sample holding position. For example, the sensor apparatus can comprise a pressure sensor that measures the respective current pressure in a chamber or conduit connected to the aspiration opening. With this embodiment, the determination is based on the fact that the pressure in the chamber or conduit drops immediately when the aspiration opening is entirely or partly closed off by the immobilized sample. 
     According to the present invention, the pressure sensor can in principle be arranged in all chambers or conduits in which entire or partial closure of an aspiration opening by a sample has the effect of a change in pressure. 
     The tissue sample handling apparatus according to the present invention preferably comprises at least one aspiration nozzle. Provision can be made in particular that the location of the opening of the aspiration nozzle defines the sample holding position. The aspiration nozzle is preferably coordinated, in terms of the dimension of the aspiration opening, with the size of the samples to be immobilized. It is advantageous in particular if the aspiration nozzle offers the largest possible contact area for the sample, in order to distribute the force acting on the sample over the largest possible contact area. 
     On the other hand, the opening of the aspiration nozzle must not be selected to be so large that samples are unintentionally sucked in rather than being immobilized. For safety, however, according to the present invention a collector apparatus, for example having a collector sieve, can be provided, for example inside the tissue sample handling apparatus. 
     In an advantageous embodiment, provision is therefore made that the aspiration nozzle is exchangeable. An embodiment of the tissue sample handling apparatus in which different aspiration nozzles, in particular aspiration nozzles having different opening diameters, are attachable and/or that comprises a storage apparatus, in particular a turret or slide magazine, for different aspiration nozzles, in particular aspiration nozzles having different opening diameters, is particularly advantageous and particularly quickly adaptable to the respective utilization situation. For example, provision can be made that the respectively required aspiration nozzle can be brought into the working position, like the objectives of a microscope, by rotating an aspiration nozzle turret. 
     An advantageous embodiment of the tissue sample handling apparatus according to the present invention comprises a separation apparatus for separating a liquid and/or solid objects, in particular liquid paraffin, out of a gas stream, in particular an air stream, sucked in particularly through the aspiration nozzle. In the separation chamber, for example, the paraffin can be separated from a sucked-in paraffin mist. 
     The separation apparatus can comprise in particular a separation chamber which is embodied and arranged in such a way that a liquid sucked in with a sucked-in gas stream condenses in the separation chamber. 
     In an embodiment that promotes the condensation procedure particularly efficiently, the separation chamber is embodied and arranged in such a way that the flow velocity of the gas stream decreases upon entry into the separation chamber and/or upon flowing through the separation chamber. This can be implemented, for example, by the fact that the passthrough cross section widens. Alternatively or additionally, an impact element, for example an impact panel, and/or a deflection baffle and/or a labyrinth can be provided for the gas stream. 
     For emptying the separation chamber, provision can advantageously be made that a liquid sucked in with a gas stream, for example liquid paraffin, and/or a solid object sucked in with a gas stream, are blown out by reversing the flow direction and/or by means of positive pressure. This can be implemented, for example, in that the separation chamber is impinged upon not by a negative pressure but instead by a positive pressure, in particular from a compressed-air conduit. Alternatively or additionally, it is also possible, by reversing the flow direction, to draw out a liquid sucked in with a gas stream and/or a solid object sucked in with a gas stream by means of negative pressure. For this, a negative-pressure conduit could be temporarily attached to the aspiration nozzle. 
     Another embodiment according to the present invention, for which extremely short maintenance and cleaning down times are sufficient, comprises an exchangeable separation chamber. The separation chamber can in particular be advantageously embodied as a disposable container and/or single-use container 
     In another embodiment, the separation apparatus contains a centrifugal separator. 
     In a very particularly advantageous embodiment, at least one heating apparatus is provided for heating at least a part of the tissue sample handling apparatus. This reliably prevents a liquid sucked in with a gas stream from solidifying unintentionally and/or at locations at which the solidified liquid, for example solidified paraffin, might result in a functional impairment. 
     In particular, provision can advantageously be made that at least one heating apparatus is provided for heating the aspiration nozzle or the multiple aspiration nozzles. Provision can also be made that at least one heating apparatus is provided for heating conduits, in particular tubing conduits. 
     The tissue sample handling apparatus according to the present invention [?can] advantageously be embodied for (in particular, automatically) transporting a grasped sample into a predefined or predefinable set-down position. For this, the tissue sample handling apparatus can comprise, for example, a displacement apparatus, an X-Y-Z manipulator, or a robot arm that can move at least the aspiration nozzle in space, for example between a pickup position and a set-down position. 
     According to the present invention the tissue sample handling apparatus can also comprise an image processing system that, preferably automatically, detects a sample that is to be picked up and/or a set-down position for a sample to be set down. In particular, provision can furthermore be made that an open- or closed-loop control apparatus controls in open- and/or closed-loop fashion the position and/or the travel distance of the sample holding position and/or of the aspiration nozzle, and/or the negative pressure or optionally further parameters, in accordance with the information ascertained by the image processing system. 
     As already mentioned, the tissue sample handling apparatus according to the present invention can advantageously be part of an automatic handling machine or automatic sample preparation machine. 
     Further goals, advantages, features, and possible applications of the present invention are evident from the description below of an exemplifying embodiment with reference to the drawings. In this context, all features described and/or graphically depicted, independently or in any useful combination, constitute the subject matter of the present invention, irrespective of their grouping in the claims or their internal references. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING VIEWS 
       In the drawings: 
         FIG. 1  schematically shows a tissue sample handling apparatus according to the present invention; 
         FIG. 2  shows a further tissue sample handling apparatus according to the present invention having a negative-pressure control system and a separation apparatus; and 
         FIG. 3  shows an automatically operating tissue sample handling apparatus according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  schematically shows a tissue sample handling apparatus  1  according to the present invention for grasping a histological sample  2  and setting it down again. 
     Tissue sample handling apparatus  1  comprises an aspiration nozzle  3  whose aspiration opening  4  defines a sample holding position  5 . Sample  2  can be immobilized in sample holding position  5  by means of negative pressure. 
     Aspiration nozzle  3  is connected via a heatable aspiration tube  6  to a separation apparatus  19 , namely to a separation chamber  7 . Aspiration tube  6  comprises a heating apparatus  8 . Concretely, aspiration tube  6  has a heating strip wound around it. This advantageously prevents liquid, such as paraffin, that is sucked in with a gas stream from already hardening in aspiration tube  6  and clogging it. 
     Separation chamber  7  comprises a connector  9  for a conduit  10  by means of which a negative pressure is generated in separation chamber  7 , in aspiration tube  6 , and in aspiration nozzle  3 . As long as the negative pressure exists, a sample located in sample holding position  5  is held at the tip of aspiration nozzle  3  by external air pressure. The sample can be released by switching off the negative pressure. 
     Separation chamber  7 , aspiration tube  6  and aspiration nozzle  3  can also be impinged upon via conduit  10  not with negative pressure but instead (in metered fashion) with a positive pressure. The purpose of this is, for example, to blow out the paraffin that has collected in separation chamber  7  or to detach a sample that is adhering stubbornly to the aspiration nozzle, for example because of an adhesive effect of the paraffin. 
       FIG. 2  shows a further tissue sample handling apparatus  1  according to the present invention that, in terms of basic function, operates exactly like tissue sample handling apparatus  1  depicted in  FIG. 1 . An open- and closed-loop control apparatus  13 , which controls the negative pressure in conduit  10  as a function of the negative pressure in separation chamber  7 , is additionally provided. The negative pressure in separation chamber  7  is measured with the aid of a pressure sensor  12  that forwards measurement signals to open- and closed-loop control apparatus  11 . 
     Because the pressure in separation chamber  7  drops immediately when aspiration opening  4  is closed off entirely or partly by the immobilized sample  2 , open- and closed-loop control apparatus  11  can ascertain, with the aid of pressure sensor  12 , whether or not a sample is immobilized in sample holding position  5 . 
     In the interest of gentle treatment of sample  2 , open- and closed-loop control apparatus  11  lowers the forces acting on the sample, by reducing the negative pressure in conduit  10 , when a sample  2  is immobilized in sample holding position  5 . A valve  13  controlled by open- and closed-loop control apparatus  11  is provided in conduit  10  for this purpose. 
       FIG. 3  shows an automatically operating tissue sample handling apparatus  1  according to the present invention that is embodied for autonomously and automatically grasping a sample  2 , for example out of a cassette  14 , and setting it down again at another location, for example in an embedding mold  15 . 
     Tissue sample handling apparatus  1  comprises an X-Y-Z manipulator  16  that can move at least the aspiration nozzle together with separation chamber  7  freely in space, under the control of a central control system  17 . 
     Central control system  17  controls X-Y-Z manipulator  16  as a function of the information transmitted to it from an image processing system  18  that automatically detects a sample  2  that is to be picked up, and the respective set-down position for a sample  2  that is to be set down. 
     PARTS LIST 
     
         
         
           
               1  Tissue sample handling apparatus 
               2  Sample 
               3  Aspiration nozzle 
               4  Aspiration opening 
               5  Sample holding position 
               6  Aspiration tube 
               7  Separation chamber 
               8  Heating apparatus 
               9  Connector 
               10  Conduit 
               11  Open- and closed-loop control apparatus 
               12  Pressure sensor 
               13  Valve 
               14  Cassette 
               15  Embedding mold 
               16  X-Y-Z manipulator 
               17  Central control system 
               18  Image processing system 
               19  Separation apparatus