Laboratory Equipment & Services Information System by Centralized Laboratory Management Office (CeLMO)

A "freezing microtome Shandon" is a specialized medical device, specifically a cryostat manufactured by Shandon, used to rapidly freeze tissue samples and then precisely slice them into thin sections for analysis under a microscope, primarily in pathology laboratories to quickly diagnose conditions during surgery by examining frozen tissue samples; essentially, it allows for rapid tissue sectioning while preserving the tissue's structural integrity at very low temperatures. 

Specifications of the Shandon FE Cryostat

• Touch screen display for setting up sectioning parameters
  
   
• Section thickness adjustment 1-20 μm in 1μm adjustments and 20–60 μm in 5μm adjustments
  
   
• Vertical cutting stroke 57mm
  
   
• Horizontal specimen advance of 25 mm
  
   
• Cryochamber temperature control 0° to -35°C
  
   
• Cryobar and dedicated adjustable cryobar cooling system to -55°C. The cryobar refrigeration system cools specimen in as little as two hours while preventing freezing
  
   
• Specimen holder temperature control 0° to 40°C (±10° of chamber temperature)
  
   
• Positive locking flywheel to prevent injury while working around blade and specimen
  
   
• Automatic fumigation cycle to disinfect chamber
  
   
• Uses CFC-free refrigerants and foam insulation
  
   
• Dual compressor system to ensure specimen integrity by keeping specimens frozen if the cryobar fails
  
   
• Ergonomic design including a three-level adjustable footrest to help reduce fatigue while sitting or standing and a raised cutting area to help prevent back strain while sectioning

Similar to a standard microtome, a cryostat functions to obtain thin (1-10 mm in thickness) sections from a piece of tissue, but while a standard microtome carries the operation at room temperature, the cryostat enables the operator to section the tissue at low temperature (–20 to –30 C). In a cryostat, the blade and the sample are located inside an upright stationary freezer/chamber while the wheel for rotating the sample holder is externally located.

Tissues for cryostat sectioning do not need be fixed in formalin for hours or days, as is the case for routine histology. Instead, tissues are immediately cryofixed after sampling. For cryofixation, the tissue pieces are placed in a viscous, gel-like medium (OCT) and are plunged in isopentane cooled with dry ice or liquid nitrogen.

For sectioning, the frozen OCT tissue blocks are placed on a metal plate which brings their temperature to –20 to –30 C. Once that temperature is reached, the specimen is mounted on the microtome chuck and sectioned. Once sections of a satisfactory quality are obtained, they are mounted on a glass slide at room temperature (~20 C). The higher temperature of the glass slide relative to that of the tissue section causes the section to instantaneously melt and adhere to the glass.

The entire process from cryofixation to obtaining sections on glass slides can take as little as 10 to 20 minutes, allowing for rapid sample analysis.