Difference between a Microtome and a Cryostat

A Microtome is used to cut very thin sections at room temperature, on the other hand a Cryostat is used to cut frozen sections at sub zero temperatures (generally -30 deg C).

A cryostat is used in situations where rapid analysis of tissues is required. The water rich tissue is frozen on a quick freezing shelf inside the cryostat, this makes it very hard and it is then ready to be cut into thin sections in a microtome, also placed inside the cryostat chamber.

On the other hand to be cut in a simple microtome, the tissue needs to be first dehydrated and fixed in paraffin before  it can be sectioned. It is a long procedure compared to quick sectioning in a cryostat.

The quality of sections cut in a cryostat is inferior compared to those cut in a microtome because dehydrated and  paraffin embedded tissues give better sections but when it comes to quick sectioning, Cryostat is the choice. 

Choosing Among Manual, Semi Automatic and Fully Automatic Microtome

The main factor in your Microtome buying decision would be the throughput required.

For Low throughput : Manual

For Medium throughput : Semi Automatic

For High throughput : Fully Automatic

Difference between a Manual, Semi Automatic and Fully Automatic Microtome

In a manual microtome, specimen feed and the rotary motion (cutting stroke) is done by hand.
In a semi automatic microtome, specimen feed is motorized but the rotary motion is still done by hand.
On the other hand in a fully automatic microtome, both the specimen feed and the rotary motion is motorized.

Features of a Manual Cryostat Microtome

The following features are basic and essential in a manual cryostat microtome
1. Thermostatically controlled chamber temperature, preferably as low as -40 deg C
2. Frost Free glass for clear visibility during sectioning
3. Automatic Retraction for uniform sections.
4. Cooling down time should be less than 60 mins.
5. Auto Defrosting
6. Built in Anti Glare Illumination
7. Preferably SS chamber which is easy to clean.
8. Built in Drainage System
9. Should have castors for easy mobility
10. Digital Display of chamber temperature
11. At least 10 freezing stations.
12. Universal Knife Holder
13. Handwheel lockable in any position

Features of A Semi Automatic Microtome

What features to look for when buying a semi automatic microtome for your histology lab?

A Semi Automatic Microtome is an enhancement over manual sectioning, as it incorporates high precision motorized specimen feed for efficient operations and consistently uniform sections.

The following features are a must in a Semi Automatic Microtome:
1. Section and Trim Modes
2. Fast Forward Function
3. Fast Backward Function
4. Section/Trim thickness setting function.
5. LCD that displays section thickness and section counts
6. Feather touch keypad
7. A Universal knife holder
8. Interchangeability between universal casette clamp and standard specimen clamp
9. A knife guard
10. Lockable Hand Wheel
11. Automatic Retraction
12. Anti Roll Plate
13. LED visual limit indicators/ alarm system
14. Section waste tray for tissue debris

Microtomy Issues : No sections are cut as specimen doesn't advance

Issue
No sections are cut as specimen doesn't advance 

Causes
The specimen has reached the front limit position 

Remedy
Move back the specimen holder and the knife holder

Microtomy Issues: Sections are compressed / wrinkled

Issue
Sections are compressed / wrinkled

Causes
1. The blade is blunt
2. The specimen is too hot
3. The angle of slicing is too big
4. The sectioning speed is too fast

Remedy
1. Change to other side of the blade edge or change the blade
2. Freeze the specimen for some time before sectioning
3. Test the sections by gradually changing the angle 
4. Turn the handwheel slowly