Abstract:
The present invention is directed to a cleaning system and methods for cleaning tissue embedding molds. The cleaning system includes a cleaning vessel that holds a cleaning solution. The tissue processing molds are supported by a basket receptacle which is placed inside the cleaning vessel. Cleaning solution is supplied to the cleaning vessel through a supply line. Additional fluids are stored in a reservoir and may be mixed with the cleaning solution in the supply line. Cleaning solution drains from the cleaning vessel through a drain line. A controller controls the opening and closing of valves and the activation or deactivation of a heat source to operate a wash cycle, a rinse cycle, and a dry cycle.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   Not Applicable. 
   BACKGROUND OF THE INVENTION 
   To facilitate microscopic examination of pathology tissue specimens, tissue specimens are typically treated with processing fluids, encased in a block of paraffin, and then sliced into thin sections. This process is carried out by placing each tissue specimen in a tissue processing cassette. Such cassettes used for pathology tissue specimens for microscopic examination are well known. While tissue processing cassettes vary in design, tissue processing cassettes generally include an open-topped base having a perforated bottom wall and a removable perforated cover. The cassettes are generally fabricated of a moldable plastic that resists damage or reaction from processing solvents or the tissue specimen itself. 
   To process a tissue specimen for examination, the tissue specimen is placed into the base of the cassette and the cover is secured to the base. The cassette and the tissue specimen are then placed in a tissue cassette processing container where various processing fluids are passed into the cassette for the purpose of dehydrating the specimen, clearing the specimen, and infiltrating the specimen with molten paraffin. After this process is completed, the cover is removed from the base and the specimen is taken from the base and placed in a tissue embedding mold. 
   The tissue embedding mold is typically constructed of stainless steel and configured to support the specimen in a lower portion thereof and to support the base of the cassette in an upper portion thereof. With the specimen and the base positioned in the mold, the mold is filled via the perforations of the base of the cassette with liquid paraffin or some other suitable encasing material. Upon the paraffin solidifying, the specimen becomes encased within a block of paraffin which extends from the base of the cassette. The base and the block of paraffin can then be mounted in a microtome where a section of the tissue specimen can be sliced for microscopic examination. 
   After a paraffin-encased tissue specimen is removed from the mold, the mold needs to be cleaned thoroughly before the mold can be used again. In the past, workers have cleaned molds by placing them in a bath of heated xylene. Unfortunately, xylene is highly flammable and thus presents an obvious fire and explosive danger. 
   Thus, there is a need for a method by which the tissue processing molds can be cleaned without creating a fire or explosive danger. It is to such a method that the present invention is directed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a prior art tissue embedding mold. 
       FIG. 2  is a schematic view of a system for cleaning tissue embedding molds in accordance with the present invention. 
       FIG. 3  is a section view of a paraffin recovery system in accordance with the present invention. 
       FIG. 4  is a schematic view of another embodiment of a system for cleaning tissue embedding molds in accordance with the present invention. 
       FIG. 5  is a schematic view of a controller for a cleaning system illustrating the functions of the controller. 
       FIG. 6  is a schematic view of another embodiment of a system for cleaning tissue embedding molds in accordance with the present invention. 
       FIG. 7  is a flow chart for a method for cleaning the tissue embedding molds in accordance with the present invention. 
       FIG. 8  is a schematic view of another embodiment of a system for cleaning tissue embedding molds connected to a computer, in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings and more particularly to  FIG. 1 , a tissue embedding mold  101  is shown to have a generally rectangular structure. In ordinary use, as noted above, the tissue embedding mold  101  is filled with paraffin to encase a specimen located in the tissue embedding mold  101 . After being used, the tissue embedding mold  101  usually contains some paraffin residue  103  at a bottom or along sidewalls of the tissue embedding mold  101 . 
     FIG. 2  shows a schematic view of a cleaning system  100  for removing paraffin from a tissue embedding mold  101 . As shown in  FIG. 2 , the cleaning system  100  includes a cleaning vessel  102 , a surfactant reservoir  104 , a solution supply line  106 , a drain line  108 , a heat source  110 , a supply valve  112 , a drain valve  114 , a surfactant supply valve  116 , and a controller  118 . One or more molds  101  are placed in a mold receiving chamber  119  of the cleaning vessel  102  and covered with a cleaning solution. The cleaning solution may be water or a mixture of water and a surfactant or a paraffin dissolving solvent. The cleaning vessel  102  has a low-level sensor  122  and a high-level sensor  124  that indicate whether the cleaning solution is in contact with the low-level sensor  122  or the high-level sensor  124 . The low-level sensor  122  and the high-level sensor  124  are connected by wiring to the controller  118 . The lid  126  is pivotally attached to a cleaning vessel base  128 . 
   The molds  101  may be supported in the cleaning vessel by a basket  130  having a handle  132 . The handle  132  is used by a worker to manually support the basket  130  during removal or insertion of the basket  134  into the cleaning vessel  102 . An outside surface of the handle  132  is preferably made of a rubber or other tactile material to facilitate manipulation of the basket  130 . The tactile material of the handle  132  is preferably wrapped around a thermally insulating material, such as ceramic, to retard heat conduction through the handle  132  and thereby prevent the worker from being burned. 
   In operation, the cleaning system  100  is automatically controlled by the controller  118 . The controller  118  includes a temperature setting device, a wash cycle timer set, a rinse cycle timer, and a dry cycle timer set, which will be discussed below in reference to  FIG. 5 . After an operator loads the molds  101  into the basket receptacle  134 , closes the lid  126  and places inside the cleaning vessel  102 , the operator sets the temperature setting device to a design temperature, selects a wash cycle timer setting, a rinse cycle timer setting, a dry cycle timer setting, and then turns on a switch to activate the controller  118 . Alternatively, the controller  118  can be configured to begin operation upon closing of the lid  126 . 
   For the first time operation of the cleaning system  100 , the cleaning vessel  102  initially contains no cleaning solution. When the controller  118  is activated, the cleaning solution supply valve  112  opens to allow cleaning solution, or other solvent, to flow into the cleaning vessel  102 . The surfactant supply valve  116  also opens to mix a controlled amount of surfactant with the water at a T-connection  138 . The cleaning solution then fills the cleaning vessel  102  until the high-level sensor  124  senses the presence of liquid, at which time the controller  118  closes the cleaning solution supply valve  112  and the surfactant supply valve  116 . 
   When the cleaning vessel  102  is filled with the cleaning solution, the heat source  110  activates to begin heating the solution in the cleaning vessel  102 . It is generally contemplated that the heating solution supplied to the cleaning vessel  102  is ordinary hot water supplied by a commercial hot water heater in a building. However, the water may also be cold water or a paraffin solvent in which case the heat source  110  must supply heat to achieve a specified design temperature. The water may also need to be chemically treated with softeners to extend the life of the components of the cleaning system  100 . 
   The amount of surfactant in the aqueous solution is preferably in a range from about 1:5 to about 1:500. One suitable concentration of the aqueous solution is 1 part surfactant to 20 parts water. Suitable chemicals for the surfactant include alkalines. 
   It is generally contemplated that the heat source  110  has one or more electrical heating elements that fit beneath the cleaning vessel  102 . However, the heat source  110  may also be natural gas or may be one or more electrical heating elements located inside the cleaning vessel  102 . 
   The heat source  110  is designed to heat the cleaning solution to a design temperature that is at least equal to the melting temperature of the paraffins used for the tissue processing molds  101 . This design temperature is typically at least 60 degrees centigrade (140 degrees Fahrenheit). In one preferred embodiment, the design temperature is at least 100 degrees centigrade (212 degrees Fahrenheit) so that the aqueous cleaning solution will boil and sufficiently agitate the cleaning solution in the cleaning vessel  102  to facilitate removal of the paraffin from the molds  101 . 
   After a wash cycle time which begins when the heat source  110  is activated, the heat source  110  deactivates, the water drain valve  114  opens and the cleaning solution drains from the cleaning vessel  102  through the water drain line  108 . When a level of the cleaning solution in the cleaning vessel drops below the level of the low-level sensor  122 , the water drain valve  114  closes. 
   A wash cycle is defined to include all of the operations that occur from the opening of the cleaning solution supply valve  112  through the closing of the cleaning solution drain valve  114 . A rinse cycle performs the same operations as a wash cycle except that the surfactant supply valve  116  never opens to mix the surfactant with the water and, as a result, also does not subsequently close when the high-level sensor  124  detects the presence of cleaning solution. Thus, the rinse cycle operates with rinse solution being the only liquid inside the cleaning vessel  102 . 
   Using a design temperature of 60° C. and wash cycle times and rinse cycle times of three minutes, tests with typical paraffins have shown that programming the controller to operate three wash cycles followed by two rinse cycles performs a thorough cleaning of the tissue embedding molds  101 . 
   When the heater source  100  is heated to produce design temperatures of at least 100° C. for aqueous cleaning solutions, the cleaning system  100  must also include provisions for venting steam away from any personnel near the cleaning vessel  102 . It is generally contemplated that the amount of paraffin used with the processing molds will not cause problems with the sewer system of the building where the tissue processing molds  101  are cleaned. However, if there is a problem, the drain line  108  may be connected to a system to remove or recover paraffin from the waste water, which is discussed in relation to  FIG. 3 . 
     FIG. 3  shows a paraffin recovery system  150 . The paraffin recovery system  150  includes a tank  152  that receives waste cleaning solution through the drain line  108  shown in  FIG. 2 . The paraffin recovery system  150  also includes several thermoelectric baffles  154  positioned inside the tank  132 . Each baffle  154  includes a cold end  156  located near a top  158  of the tank and a hot end  160  located near a bottom  162  of the tank  152 . The cold end  156  is maintained at a temperature below the melting point of the paraffin and the hot end  160  is heated to a temperature of at least the melting point of the paraffin. 
   The thermoelectric baffles  154  are solid-state electrically-driven heat exchangers that can pump heat in a certain direction depending on a polarity of an applied voltage. The baffles operate by the Peltier Effect, by which a temperature gradient can be induced when an electrical current flows through a junction of dissimilar metals. A typical thermoelectric cooler consists of alternating blocks of N-type and P-type bismuth telluride semiconductors sandwiched between, and soldered to, two opposing thin ceramic plates. 
   The waste solution, which generally comprises cleaning solution and paraffin, enters the tank  152  at an inlet  164  and exits the tank  152  through an outlet  166 . When the waste water travels over the baffle cold ends  156 , the paraffin cools sufficiently to congeal and separate from the waste aqueous solution. The congealed paraffin collects on top cold ends  156  of the baffles  154 . After several uses of the cleaning system  100  and the paraffin recovery system  150 , a worker must scrape the paraffin from the baffles  154 . Liquid that travels through the paraffin recovery system  150  exits the outlet  166  as a treated aqueous solution. The treated cleaning solution may then be passed to the sewer line of a building or maybe passed into the mold receiving chamber  119  of the cleaning vessel  102  for reuse. 
     FIG. 4  shows an alternate embodiment of a cleaning system  200  for cleaning tissue processing molds  220  that is identical to the cleaning system  100 , except that a mechanical agitator  201  is positioned in a bottom of a cleaning vessel  202 . The cleaning system  200  also includes similar components to the cleaning system  100 , including a surfactant reservoir  204 , a heat source  210 , a cleaning solution supply valve  212 , a drain valve  214 , a surfactant supply valve  216 , a controller  218 , a low-level sensor  222 , and a high-level sensor  224 . 
   The mechanical agitator  201  agitates fluid inside the cleaning vessel  202  to assist in removing paraffin from the tissue processing molds  220 . The mechanical agitator  201  is coupled to an electric motor  203  that fits beneath the cleaning vessel  202  and is operably connected to a controller  218  that activates and deactivates the electric motor  203 . In one preferred embodiment, the electric motor  203  rapidly alternates rotation directions between a clockwise and a counterclockwise direction. 
     FIG. 5  shows a schematic diagram that illustrates the operation of the controller  218  shown in  FIG. 4 . The controller  218  has an on/off switch  250  that activates operation of the cleaning system  200 . The controller  218  has a temperature setting device  252  to manually set the operating design temperature of the heat source  210 . 
   The controller  218  also includes a wash cycle timer set  254  and a rinse cycle timer set  256 . Each of the wash cycle timer set  254  and the rinse cycle timer set  256  are devices for which a cycle time of each can be specified by an operator. The controller  218  also includes a wash cycle counter set  260  and a rinse cycle counter set  262  to set the number of wash cycles and the number of rinse cycles that the cleaning system  200  will perform. 
   The low-level sensor  222  and the high-level sensor  224  sense the presence or absence of aqueous solution as described above for the cleaning system  200 . The controller  218  also includes a system logic device  264  that outputs signals based on input signals received from the low-level sensor  222 , the high-level sensor  224 , the on/off switch  250 , the temperature setting device  252 , the wash cycle timer set  254 , the rinse cycle timer set  256 , the dry cycle timer set  258 , the wash cycle counter set  260 , and the rinse cycle counter set  262 . Based on the input signals received, the system logic  264  outputs signals to controlled components  266  of the cleaning system  200 . The controlled components are the agitator motor  203 , the heat source  210 , the cleaning solution supply valve  212 , the drain valve  214 , and the solution supply valve  216 . 
   The system logic  264  may include analog electrical devices such as resistors, capacitors, inductors, switches, time-delay relays and other control relays. The system logic  264  may also be a microprocessor which must first convert the electrical input signals to digital data signals with a analog-to-digital converter. After the system logic  264  of the microprocessor processes the digital data signals, a digital-to-analog converter must be used to generate electrical signals for operating the controlled components  266 . The system logic  264  may also be a combination of analog and digital components. 
   Although the controller  218  has been shown as having operator-controlled variables, such as wash cycle time settings, rinse cycle time settings, dry cycle time settings, numbers of wash cycles, and numbers of rinse cycles, these operator-controlled variables may be set to fixed values after further use and experimentation determines that fixing these operator-controlled variables is appropriate. For example, it may later be determined that a time of four minutes is an appropriate time for both the wash cycle time setting and the rinse cycle time setting. Then, these variables can be fixed in the system logic  264  so that the operator has few decisions to make to operate the cleaning system  200 . This in turn would allow the cleaning system  200  to be operated by inexperienced or less experienced operators. 
     FIG. 6  shows an alternate embodiment of a manually controlled cleaning system  300 . The cleaning system  300  operates similarly to the cleaning system  100 , except that most of the various components of the cleaning system  300  are manually controlled by an operator. Surfactant is stored in a surfactant reservoir  304 . For the cleaning system  300 , the operator manually operates a cleaning solution supply valve  312 , a cleaning solution drain valve  314 , and a surfactant supply valve  316 . 
   After selecting and setting a design temperature, the operator opens the cleaning solution supply valve  312  to let water or other solvent into a cleaning vessel  302  until the cleaning vessel  302  is sufficiently filled with cleaning solution. Next, if water is used as the solvent, the operator opens the solution supply valve  316  to let surfactant flow into the cleaning vessel  302 . Alternatively, the cleaning system  300  may be configured without a surfactant supply valve  316 , in which case the cleaning solution is poured into the cleaning solution from a container holding the cleaning solution. 
   Next, the operator adjusts a temperature control knob on controller  318  and turns on a heat source  310  by turning on a switch on the controller  318 . When the heat source  310  has operated for a certain wash cycle time interval, the operator can then drain the cleaning vessel  302  by opening water drain valve  314 . The wash cycle and the rinse cycle are timed by the operator using an ordinary watch or clock. 
   For this manual operation, the operator may visually inspect tissue processing molds  320  after each wash cycle to ensure that all paraffin has been removed. If there is still paraffin on the molds  320 , the operator can operate another wash cycle using a different wash cycle time. On a second or subsequent wash cycle, the heat source temperature may be adjusted to a higher level. When enough wash cycles have been operated to completely remove the paraffin, at least one rinse cycle should be operated with rinse solution and no cleaning solution to remove surfactant from the molds  320 . 
   The manual cleaning system  300  can have advantages in that the manual cleaning system  300  may use less energy, may require less time and may be more efficient. The automatic cleaning systems  100  and  200  have advantages in that the automatic cleaning systems  100  and  200  may remove dirt, bacteria and tissue fragments not visible to the naked eye, does not require monitoring by the operator, and may be less expensive to operate when the cost of human monitoring are taken into account. 
     FIG. 7  is a flow chart for a method  400  for cleaning the tissue processing molds. At step  402 , the molds are placed inside the cleaning vessel. At step  404 , the input parameters are selected. The input parameters include the design temperature, the wash cycle time t w , the rinse cycle time t r , the dry cycle time t d , the number of wash cycles N w , and the number of rinse cycles N r . At step  406 , a wash cycle counter I is set to zero. At step  408 , water is added to the cleaning vessel. 
   At step  410 , surfactant is added to the aqueous or non aqueous solution. At step  412 , the heat source is activated at the selected design temperature setting. For cleaning systems having an agitator, the agitator motor is also activated at step  412  to agitate the cleaning solution. The wash cycle timer also begins operating when the heat source is activated at step  412 . 
   At the end of the selected wash cycle time t w , at step  414 , the heat source is deactivated and the cleaning solution is drained from the cleaning vessel. In one preferred embodiment, the wash cycle time is about five minutes. At step  416 , the wash cycle counter is updated from I to I+1. At step  418 , the wash cycle counter I is compared to the selected value of the numbers of wash cycles N w  to be performed. If I is less than N w , then the wash cycle is repeated. If I is equal to N w , then the wash cycle is ended. 
   The rinse cycle begins at step  420  by setting rinse cycle counter J to zero. At step  422 , rinse solution is added to the cleaning vessel. At step  424 , the heat source is activated and, if the cleaning system has an agitator, the agitator is activated. A rinse cycle timer is also started at step  424 . At step  426 , after a selected rinse cycle time t r , the agitator is deactivated (if applicable) and the cleaning solution is drained from the cleaning vessel. At step  428 , the value of the counter J is updated to have the value of J+1. At step  430 , the value of J is compared to the value of N r . If the value of J is less than N r , then the rinse cycle is repeated. If the value of J equals N r , then the rinse cycle is ended. 
   At step  432 , the cleaned and dried molds are inspected. At step  434 , an operator inspects the molds to determine whether the molds are clean. If the molds are clean, the molds are returned to service at step  436 . If the molds are not sufficiently clean, the molds are returned to the cleaning system at step  402  to be cleaned again. 
     FIG. 8  shows a cleaning system  500  having a controller  502  connected to a computer  504  with a monitor or other user interface  506 . The computer  504  has programming to prompt an operator to enter input parameters such as a wash cycle timer setting, a rinse cycle timer setting, a dry cycle timer setting, a design temperature, a number of wash cycles to be operated and a number of rinse cycles to be operated. The programming may also have a default setting for the input parameters so that the operator may simply select the “default settings” option to operate the system. 
   From the above description, it is clear that the present invention is well adapted to carry out the objects and to attain the advantages mentioned herein as well as those inherent in the invention. While presently preferred embodiments of the invention have been described for purposes of this disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are accomplished within the spirit of the invention disclosed as defined in the appended claims.