Automated Tissue Processing

8/12/2019 Automated Tissue Processing

1/19

AUTOMATED TISSUE PROCESSING


2/19

Tissue processing

Tissues and cells examined outside thebody with an imagine system,are an artifactof the original.

Histology and histopathology arecomparative sciences where like iscompared with like, like with unlike andeven sometime unlike with unlike.

It is essentisl to ensure that the artifactproduced at any stage during tissuehandling and processing is constant.


3/19

It is as much for this reason as any otherthat the predominant method forproducing tissue sections is by cutting

paraffin wax-embedded tissue on amicrotome.

Freezing tissue to obtain a solid block fromwhich thin sections could be cut is nowconfined to specialist areas such asnueropathology,lipid demonstration andurgent frozen sections.


4/19

This method of tissue section productionhas recently increased.

Paraffin wax is not miscible with water andas most fixatives where water based.

There must be treatment of tissues to allowparaffin wax impregnation. This is calledtissue processing.


5/19

Principles of tissue processing

The aim of tissue processing is to embedthe tissue in a solid medium firm enough tosupport the tissue and give it sufficientrigidity to enable thin sections to be cut.

The most satisfactory embedding materialfor routine histology is parafffin wax.


6/19

Stages involved

Dehydration: to remove fixative and waterfrom the tissue and replace them withdehydrating fluid.

Clearing: replacing the dehydrating f luidwith a fluid that is totally miscible withdehydrating fluid and the embeddingmedium.

Impregnation: replacing the clearing agentwith embedding medium.

embedding.


7/19

DEHYDRATION

A. Definition: removal of water

B. Steps

1. wash out fixative2. graded series of alcohol

a. 70%, 95%, 100%, 100%

3. replace water by diffusion4. not too long, not too short


8/19

DEHYDRATION

Procedure1. automatic tissueprocessor

a. overnight2. Baths: water,70,95,100,100 %

alcohol3. Clearing agent: 2baths of xylene


9/19

CLEARING

A. Paraffin solventB. Xylene, clearing

agentC. Makes tissue appearclear


10/19

INFILTRATION

A. Replace xylene with paraffin

B. Immerse in melted paraffin

55oC MPC. Remove all bubbles,


11/19

EMEDDING

D.Procedure

1. Place tissue cassette in

melted paraffin2. Fill mold with paraffin

3. Place tissue in mold

4. Allow to cool


12/19


13/19

Factors influencing the rate of processing

Agitation

Heat

Viscosity vaccum


14/19

Automated tissue processing

The overwhelming majority ofhistopathology department now usemachines to process tissue blocks.

These machines reduce the time taken toprocess the routine tissue by manualmethod by atleast 24 hours.


15/19

Processsing machines

Traditional carousel

Have 12 separatestages in processing.

Minimum time takenis 30 minutes in each

stage.

Enclosed pump fluidtype

Programmedelectonically

processor takes 15

minutes per station.


16/19

Important points to take care for tissue

processing Fluid and wax containers must be filled to

the appropriate level and correctly locatedin the machine.

Any spillage shoukld be wiped away.

Accumulation of wax on any surface orbeaker lids must be removed.

Wax bath thermostats are set at least 3degrees above the melting point of wax.


17/19

Paraffin wax bath on the carousel- typemachine should be checked to ensure thatthe electric plux are in contact and the waxis molten.


18/19

Automated processing schedules

in most laboratories an overnight schedule isused.

With schedules of approximately 16 to 18 hours

duration.


19/19

OVERNIGHT PROCESSING

SCHEDULESCONTAINER FLUID TIME IN HOUR

1 10% FORMALIN 0

2 70% ALCOHOL 0.5

3 95% ALCOHOL 0.54 100% ALCOHOL 0.5

5 100% ALCOHOL 1

6 100% ALCOHOL 1

7 100% ALCOHOL 1

8 100% ALCOHOL/XYLENE 0.5

9 XYLENE 1

10 XYLENE 2

11 WAX 2.5

12 WAX 4

Automated Tissue Processing

Documents

Transcript of Automated Tissue Processing