Abstract:
An apparatus and a method for processing tissue samples are described. The apparatus comprises: at least one retort for accommodating tissue samples; at least one container for storing alcohol or xylene; a valve adapted to connect the at least one retort with the at least one container depending on an operating position of the valve; and at least a first sensor that is arranged in flow direction between the container and the retort for measuring a value of a parameter that represents a purity level of the alcohol or xylene; wherein the first sensor and the valve are configured to replace the alcohol or xylene depending on the value of the parameter that represents the purity level. The method comprises for the alcohol or xylene conducting between the container and the retort; automatically measuring the purity level and replacing depending on the purity level.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of the German patent application DE 102008054066.8 having a filing date of Oct. 31, 2008. The entire content of this prior application DE 102008054066.8 is herewith incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The invention relates to an apparatus and a method for processing tissue samples. The apparatus comprises at least one retort for accommodating the tissue samples and at least one container for storing a process medium. The container communicates with the retort depending on an operating position of a valve. 
     Biological tissue samples, in particular histological tissue samples, are often needed in the field of human medicine and veterinary medicine, in particular as a microscopic preparation for the assessment of cells and their surroundings. For the microscopic examination, thin sections of the tissue sample have to be prepared, which are assessed by an expert in incident light or in transmitted light under the microscope. 
     For preparing thin sections, for example with the aid of a microtome, the tissue sample must have a certain solidity so that thin transparent sections having a thickness in the micrometer range can be prepared with the aid of a knife. To this end, the tissue sample first has to go through a treatment process in which it is fixed, dehydrated, cleared and then infiltrated with a carrier material, preferably molten paraffin. Often, these processes are successively performed in one single apparatus, the so-called tissue processor, which, to this end, includes a closable process chamber, called retort, which accommodates the different reagents for performing the process steps at a suitable temperature and pressure. 
     An important process step in this connection is the infiltration of the tissue sample with the carrier material in order to stabilize and solidify the tissue sample. Prior to this infiltration process step, the clearing step is performed in which alcohol residuals still present from the dehydration step are removed. As a chemical solution for this clearing step xylene or a similar agent is used. In the subsequent infiltration step, in which the tissue sample is exposed to the carrier material, usually molten paraffin, still remaining xylene components are flushed out and absorbed by the liquid carrier material, as a result whereof the carrier material is contaminated in the retort. In the same way, residual dehydrating reagents are removed in the clearing step. Constituents dissolved out of the tissue sample itself can likewise contaminate the dehydrating reagents, the clearing reagents or the carrier material. Therefore, it is necessary that the individual process steps are divided into several partial process steps, in which the tissue sample is successively exposed to different reagents with increasing purity level within the use of one reagent. 
     When, for example, the infiltration process is divided into three process steps, then the tissue sample is first treated with a first carrier material which may have a relatively high contamination degree, for example, contaminated with xylene. Thereafter, a second infiltration step with a second carrier material is performed which has a higher purity level than the first carrier material. Finally, the tissue sample is exposed to a third carrier material having the highest purity level, wherein the carrier materials may comprise xylene or further reagents. In this way, the tissue sample is completely infiltrated with carrier material in a step-wise process with increasing purity level of the carrier material used for the treatment, the carrier material having sufficiently high quality for preparing a good thin section in a microtome and for a microscopic preparation. 
     The use of several liquid reagents with different purity levels makes it necessary that these reagents are kept ready in containers in a liquid state. When one of the reagents is contaminated too much, mostly this applies to the mentioned first reagent, then this reagent has to be replaced by a reagent having an improved purity level. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to specify a method and an apparatus for processing tissue samples, which easily contribute to a high quality of the finished tissue samples. 
     This object is achieved by an apparatus for processing tissue samples, comprising: at least one retort for accommodating tissue samples; at least one container for storing alcohol or xylene; a valve adapted to connect the at least one retort with the at least one container depending on an operating position of the valve; and at least a first sensor that is arranged in flow direction between the container and the retort for measuring a measured value of a parameter that represents a purity level of the alcohol or xylene; wherein the first sensor and the valve are configured to replace the alcohol or xylene depending on the measured value of the parameter that represents the purity level. 
     This object is further achieved by a method for processing tissue samples with the aforementioned apparatus, the method comprising: conducting alcohol or xylene at least one of from the container into the retort and from the retort into the container; automatically measuring by means of the sensor a measured value of a parameter that represents the purity level of the alcohol or xylene; and replacing the alcohol or xylene depending on the measured value of the parameter that represents the purity level. 
     According to the invention an apparatus for processing tissue samples comprises at least one retort for accommodating the tissue samples and at least one container for storing a process medium. The container communicates with the retort depending on an operating position of a valve. At least one sensor is provided which is arranged between the container and the retort in flow direction. The sensor is provided for detecting a measured value of a measured quantity which is representative of a purity level of the process medium. 
     The flow direction refers to the direction in which the process medium flows. In particular, this can be from the container to the retort or from the retort back to the container. The sensor easily enables to automatically detect whether the purity level of the process medium meets a predetermined condition. This allows to easily recognize when the process medium either has to be replaced for performing a predetermined process step or has to be used for another process step and thus has to be re-classified. The process medium can, for example, be a fixation reagent, a dehydrating reagent, an intermedium, a carrier material or a cleaning reagent. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Preferably, the sensor is arranged in flow direction between the retort and the valve. This is particularly advantageous when several containers with different process media are provided, and the process media are all controlled via the same valve. 
     The arrangement of the sensor between the valve and the retort then enables to detect the purity level of different process media with one single sensor. In this connection actually chemically identical reagents with merely different purity levels or chemically totally different process reagents are referred to as different process media. 
     If the process media are so different from one another that different sensors are required for checking their purity levels, then a sensor module can be provided which comprises at least the one sensor and respective further sensors. Preferably, the further sensors are then arranged according to the one sensor. 
     During the processing of the tissue sample in the retort, the process medium or the process media are regularly transported, in particular pumped, from the respective containers to the retort and back again. While doing so, they are guided past the sensor such that it enables the determination of the purity level. The purity control can be performed during pumping of the process medium to the retort as well as to the respective container. Preferably, it is automatically decided depending on the determined purity level whether the respective process medium is to be replaced or successively used for other process steps than the present process step. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are explained in the following with reference to the enclosed drawings. 
         FIG. 1  shows a tissue processor. 
         FIG. 2  shows various components of a tissue processor relating to the infiltration of tissue samples with paraffin. 
         FIG. 3  shows various components of a tissue processor relating to dehydration, cleaning or an intermediate treatment of the tissue samples. 
         FIG. 4  shows a flow chart of a program for operating the tissue processor. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Identical parts in the various figures are identified by identical reference signs. 
       FIG. 1  schematically shows a tissue processor  10 , with which the method according to the invention can be performed. In this connection, the tissue processor  10  can also be referred to as an apparatus for processing tissue samples. The tissue processor  10  comprises a retort  12  for processing tissue samples with different reagents. In this retort  12 , the tissue samples go through several process steps, in particular a fixation process, in which formalin is typically used. Thereafter, a dehydration process is performed with alcohol solutions of different purity levels QUAL ( FIG. 4 ). In a subsequent clearing process, alcohol residuals are removed from the tissue samples and the tissue samples are prepared for the uptake of carrier material. In this clearing process, xylene or a similar agent is often used. As a carrier material, preferably paraffin or wax in different compositions is used. The process steps can be divided into several partial process steps, within which the tissue samples are, for example, exposed to the mentioned reagents with increasing purity level QUAL ( FIG. 4 ). 
     After going through these process steps, a cleaning process can be performed with the mentioned or with further reagents, for example, by execution of the mentioned process steps the other way around without tissue samples. 
     The tissue processor  10  comprises a cabinet  13  with drawers. A drawer  14  serves for accommodating reagents  15  (only two of a large number are shown), which are necessary so that the fixation process, the dehydration process and/or the clearing process can be performed. The drawer  14  has a handle  16  for operation. A further drawer  17  (only partially shown) contains components for the infiltration process described below. 
     On a table plate  18   a  working area  20  is provided. Further, on the table plate  18 , a control device  22  with a screen  24  is arranged. The control device  22  controls the treatment processes for the tissue samples with the aid of a computer. 
       FIG. 2  shows important components for performing the process for the infiltration of tissue samples with carrier material, in particular paraffin or wax. 
     The retort  12  is formed as a lockable chamber having an opening  30  which can be closed. Within the retort  12 , different reagents, in particular the paraffin which is important for the infiltration process, can be subjected to pressure, vacuum and temperature. The interior of the retort  12  is connected via a valve arrangement  32  to conduits  40 ,  42 ,  44  via electrically controllable valves  34 ,  36  or  38 , respectively. 
     The conduit  42  is connected to the content of the retort  12  via the valve  36 . Controlled via the valve  36 , liquid paraffin is supplied and discharged via the conduit  42 . A further conduit  44  serves for the connection to further reagents for the fixation process, the dehydration process and/or the clearing process, which will be described further below. 
     The conduit  42  is connected to a distributor  46  which, controlled via valves  48 ,  50 ,  52 ,  54 , distributes liquid paraffin. Connected to the distributor  46  is the conduit  56  which connects it to a supply station  58  for paraffin. The supply station  58  is formed as a drawer and comprises pull-out rails  60  and a handle  62 . 
     Further, three conduits  64 ,  66 ,  68  are connected to the distributor  46  for connecting it to a first container  70 , a second container  72  or a third container  74 , respectively. These containers  70 ,  72 ,  74  contain liquid paraffin with increasing purity level QUAL. The containers  70 ,  72 ,  74 , too, are formed as drawers and can be pulled out of the chamber of the tissue processor  12  and subsequently be removed. 
     All conduits  40 ,  42 ,  56 ,  64 ,  66 ,  68  are heated, as is the distributor  46  and, depending on the reagent used, also the valve arrangement  32  to ensure that the paraffin is always kept in a liquid state, for example, at 65° C., and does not solidify in operation. 
     The same applies to the retort  12  and its component parts as well as to the supply station  58  and the containers  70 ,  72 ,  74 . The respective heating elements are omitted in the Figure for clarity reasons. 
     The supply station  58  has a considerably larger volume than the respective container  70 ,  72 ,  74 . It also serves to melt paraffin which is present in the solid state as paraffin pellets or paraffin scales. The bulk volume of paraffin pellets or paraffin scales is considerably larger than the liquid volume of molten paraffin for the same weight. The larger volume of the supply station  58  thus allows that sufficient bulk volume of solid paraffin can be filled in, without solid paraffin having to be refilled for a sufficient liquid supply. In this way, the handling with solid paraffin is facilitated. Moreover, the liquid volume of the supply station  58  is sufficiently large so that it can supply the containers  70 ,  72 ,  74  with uncontaminated paraffin for a relatively long operating time, for example also in the case of an automatic operation during nighttime, when operating personnel does not have to be present. 
     Between the containers  70 ,  72 ,  74  and the retort  12 , in particular between the distributor  46  with its valves  48 ,  50 ,  52 ,  54 , a sensor  78  is arranged. The sensor  78  is provided for sensing a purity level QUAL of the paraffin that currently flows through the conduit  42 . Thus, during pumping of the paraffin towards the retort  12  and back to the containers  70 ,  72 ,  74 , the different purity levels QUAL of the currently used paraffin before and after the treatment of the tissue samples can be determined. The sensor  78  is, for example, an optical sensor which detects turbidity or coloration of the paraffin, wherein the paraffin may be treated with a dye for determining the purity level QUAL. Alternatively, the density or the conductance of the paraffin can be detected with the sensor  78 , dependent on which the purity level QUAL can then be determined. 
       FIG. 3  shows system bottles  80  which each have a connection  82  for a conduit  86  for pumping out a process medium, and a connection  84  for applying pressure to the system bottles  80 . Further, the system bottles  80  have caps  88  via which the process medium can be filled in. 
     In the system bottles  80 , chemically basically the same process medium is contained, each of the various system bottles  80  containing the respective process medium with a different purity level QUAL. In this connection, the process media with different purity levels QUAL can also be referred to as different process media. 
     In stations  90  with different baths  96 , further process reagents with different purity levels QUAL can be stored. The stations  90  each have one connection  92  for the transport of the respective process medium and one compressed air connection  94  for applying pressure to the stations. The connection  92  communicates with a rotational valve  100  via a conduit  98 . 
     Depending on the operating position of the rotational valve  100 , the conduit  86  or the conduit  98  communicates with the conduit  102  which leads from the rotational valve  100  to the coupling element  104 . On the coupling element  104 , a density sensor  106  and a pressure sensor  108  are arranged. The density sensor  106  and the pressure sensor  108  allow to detect the density of the process medium which currently flows through the coupling element  104 . Depending on the density of the process medium, its purity level QUAL can be determined. Thus, the density sensor  106  and the pressure sensor  108  form a sensor module for detecting a measured value which is representative of the purity level QUAL of the process medium. The density sensor  106  is particularly suited for determining the purity level QUAL of alcohol or xylene. 
     The process media which are stored in the stations  90  or the system bottles  80  comprise, for example, fixation reagents, in particular alkaline fixation reagents, for example formalin, dehydrating reagents, in particular alcohols, in particular ethanol, intermedia, for example isopropanol or aromatic hydrocarbons, in particular xylene, and/or cleaning reagents, in particular distilled water. Further, the fixation reagents, the dehydrating reagents and/or the intermedia can also be used for cleaning, and in this connection also be referred to as cleaning reagents. As an alternative to the density sensor  106  and/or the pressure sensor, one or more other sensors can likewise be provided. What is important is that by means of the respective sensor the purity level QUAL of the respective process medium can be determined. Preferably, just as many sensors are provided that the purity levels QUAL of all process media used can be determined. The purity level QUAL can, for example, also be determined by means of a photo sensor, a conductance measurement and/or by means of a measurement of a pH value of the respective process medium. 
     The tissue samples are now successively subjected to the individual process steps and thus successively exposed to the different process media. In particular, the tissue samples are successively exposed to process media with different purity levels QUAL during the partial process steps. During the treatment with chemically identical process media having different purity levels QUAL, the tissue samples are exposed to the process media preferably with increasing purity level QUAL. 
     On a storage medium of a control device for the operation of the tissue processor, preferably a program is stored ( FIG. 4 ). The program serves to automatically determine the purity level QUAL of the currently used process medium and to automatically decide on the further handling of the respective process medium. 
     The program is preferably started in a step S 2 , in which variables may be initialized. 
     In a step S 4 , a measured value MESS of the sensor or the sensors  78 ,  106  is detected. 
     In a step S 6 , the purity level QUAL is determined depending on the measured value MESS. For this purpose, a data base can, for example, be stored on the storage medium, in which the corresponding purity levels QUAL are assigned to the different measured values MESS. 
     In a step S 8 , it is checked whether the purity level QUAL is smaller than a predetermined threshold value THD. If the condition of step S 8  is met, then the purity level QUAL is sufficiently good so that the process medium can still be used for the same process step and the program is preferably continued in a step S 12 . If the condition of step S 8  is not met, then this is representative of the fact that the purity level QUAL has decreased such that the process medium can no longer be used for the same process step. Further, the program is then continued in a step S 10 . 
     In the step S 10 , a re-arrangement of the process media takes place. In particular, a process medium classified as a third process medium MED 3  is subsequently classified as a second process medium MED 2  and thus subsequently no longer used for a third one of the partial process steps but for a second one of the partial process steps. The current second process medium MED 2  is subsequently classified as a first process medium MED 1  and subsequently used for a first one of the partial process steps. The process medium currently classified as the first process medium MED 1  is replaced by means of a renewal command NEW and is exchanged with a new process medium having the highest purity level QUAL, which is classified as the third process medium MED 3  and used for the third partial process step. Thus, the contaminated process media are not always replaced by process media having the highest purity level QUAL but always by a process medium having the next higher purity level QUAL. In doing so, the process media are preferably not transferred by pumping but are merely classified differently. 
     In step S 12 , the program can be terminated. Preferably, however, the program is re-executed whenever the process medium is conducted from the container to the retort  12  or from the retort  12  back to the respective container. 
     The invention is not restricted to the embodiments described. For example, all process media can be conducted to the retort via merely one conduit or even more conduits can be present for the process media mentioned or for further process media. The number of the sensors provided is then reduced or increased accordingly. Further, the sensors can be arranged very close to the valve, the containers or the retort, for example, within the same housing. 
     LIST OF REFERENCE SIGNS 
     
         
         
           
               10  tissue processor 
               12  retort 
               13  cabinet 
               14  drawer 
               15  reagents 
               16  handle 
               17  drawer 
               18  table plate 
               20  working area 
               22  control device 
               24  screen 
               30  opening 
               32  valve arrangement 
               34 ,  36 ,  38  valves 
               40 ,  42 ,  44  conduits 
               46  distributor 
               48 ,  50 ,  52 ,  54  valves 
               56  conduit 
               58  supply station 
               60  pull-out rails 
               62  handle 
               64 ,  66 ,  68  conduits 
               70  first container 
               72  second container 
               74  third container 
               78  sensor 
               80  system bottles 
               82 ,  84  connections 
               86 ,  98  conduits 
               88  caps 
               90  stations 
               92 ,  94  connections 
               96  baths 
               100  rotational valve 
               102  conduit 
               104  coupling element 
               106  density sensor 
               108  pressure sensor 
             START program start 
             MESS measured value 
             QUAL purity level 
             THD threshold value 
             MED 1  first process medium 
             MED 2  second process medium 
             MED 3  third process medium 
             END program end 
             S 2  to S 12  method steps