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Histotechnology 1 > Frozen Sectioning > Flashcards

Frozen Sectioning Flashcards

1
Q

What are the principles of frozen sectioning?

A

Sample is not processed
Tissue becomes firm by freezing it
Ice crystals provide support for cutting thin sections
Water within tissue is frozen quickly

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2
Q

What are the main reasons for creating slides on the cryostat?

A
  1. Stat samples – patient in the OR and surgeon wants a result within 15 minutes. Cut on cryostat and do a rapid H&E. Pathologist examines slide right away and reports to the OR.
  2. Lipids, etc. - Want to demonstrate lipids or other elements of tissue that may be removed during processing
  3. Histochemistry
  4. Fluourescent antibody techniques
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3
Q

What are the advantages of frozen sectioning / cryostat use?

A
  1. Rapid diagnosis – eliminate the need to process tissue

2. No shrinkage of tissue

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4
Q

What are the disadvantages of frozen sectioning / cryostat use?

A
  1. Structural details poor
  2. Thicker section
  3. Ice crystal artifact
  4. No ribbons
  5. Biohazard concerns with fresh tissue
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5
Q

How are tissues treated / prepared for cryostat?

A

TISSUE – FRESH or 10% NB FORMALIN – WASHED!

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6
Q

What precautions must be taken with the tissue intended for frozen sectioning?

A

Fresh tissues are treated with Routine Practices.

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7
Q

What are the waste removal considerations for frozen sectioning?

A

All waste must go in biohazard bags and be autoclaved or incinerated.

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8
Q

What kind of embedding medium is used when frozen sectioning on a cryostat?

A

Water based embedding medium

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9
Q

Name some cryostat parts?

A

Chuck Holder
Freezing Bar
Anti-roll device (face Plate)

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10
Q

A cryostat is basically a __________ _________ inside a __________.

A

rotary microtome

freezer

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11
Q

Fresh tissues are usually quickly frozen at what temperature range?

A

Quickly frozen at - 10°C to -30°C, dependent on the tissue type.

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12
Q

What is brain and lymph node typically frozen at?

A

Brain and lymph node at -10°C.

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13
Q

What is liver, kidney, and spleen typically frozen at?

A

Liver, kidney, and spleen at -15degC

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14
Q

What is muscle and thyroid typically frozen at?

A

Muscle and thyroid at -20C,

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15
Q

What are these tissues typically frozen at?

a) Skin
b) Breast or other tissues with adipose tissue?

A

a) Skin at -25C,

b) Breast or other tissues with adipose tissue -30C

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16
Q

What are the typical section thickness for cryotomy?

A

The section is cut at 6 to 10 um thick. Unable to cut any thinner than that.

17
Q

Describe the cryotomy process?

A

Single section is cut. You can use the face plate or a tiny paint brush to gently drag the specimen across the cutting surface to prevent it from rolling up. Then you touch a room temperature slide down to the specimen.

18
Q

What daily maintenance should be done on a cryostat?

A
  1. Daily check of temperature before use.
  2. Regular defrosting and
  3. Regular disinfection
  4. Low temperature oil & grease
19
Q

What safety considerations are required for the cryostat work area (6)?

A
  1. Unfixed tissue is potentially infectious
  2. Gloves, mask, goggles, gown
  3. Restrict work area
  4. Restrict # of instruments
  5. Restrict # of staff
  6. Pick up debris with gauze dampened with alcohol
20
Q

What are the basic steps of frozen sectioning?

A
  1. Obtain tissue sample
  2. Prepare tissue holder
  3. Water based medium
  4. Rapid freeze
  5. “Rough in” tissue
  6. Set anti-roll device
  7. Fine cutting
  8. Pick up tissue section
21
Q

For decontamination can you use sodium hypochlorite?

A

NO, cannot use Na Hypochlorite

22
Q

What is used on cryostats for daily decontamination?

A

Daily decontamination

  • 70% Ethanol (solution) – daily cleaning (not necessary to shut down unit)
  • New cryostats – UV or ozone
23
Q

What is used on cryostats for weekly decontamination (if used often)?

A

Weekly (if used often)
shut off freezing unit and clean thoroughly with something that can kill TB and HIV, HBV, etc.
95% alcohol, Glutaraldehyde vapour or 40 % formaldehyde vapour can be used.

24
Q

What to do if? Possible reasons/Remedies.

Tissue breaks off the specimen holder.

A

Causes
- Not enough contact between specimen and holder because of air trap
- Roughing in too much
Remedies
- Use ample amounts of OCT on specimen holder
- Take smaller increments

25
Q

What to do if? Possible reasons/Remedies.

No tissue cut when drive wheel advanced

A 
Causes
- Out of gear
- Mechanism frozen after incorrect maintenance procedures
- Tissue not frozen solid
Remedies
- Put pawl back on ratchet wheel
- Ensure use of low temperature oil
- Refreeze tissue; check temperature of chamber
26
Q

What to do if? Possible reasons/Remedies.

Tissue sections roll up before going under the anti-roll plate

A

Causes
Anti-roll plate not parallel to cutting edge or not far enough ahead of bevel edge

Remedies
Adjust anti-roll plate.

27
Q

What to do if? Possible reasons/Remedies.

Tissue sections stick to anti-roll plate and/or knife

A

Causes
Anti-roll plate or knife too warm
Grease or debris on anti-roll plate or knife
Remedies
Close lid of cryostat for a few moments to cool
Clean with absolute alcohol then close lid to cool plate and knife

28
Q

What to do if? Possible reasons/Remedies.

Sections have vertical splits or are scored or shredded

A 
Causes
Knife is nicked.
Dirt on anti-roll plate
Barb of plastic from damaged anti-roll plate
Remedies
Sharpen knife or move knife over.
Clean and then cool
Sand edge of the anti-roll plate on 00 emery   cloth fastened to a flat board
29
Q

What to do if? Possible reasons/Remedies.

Tissue sections are wrinkled and folded

A

Causes
Debris on knife or anti-roll plate
Dull spot on knife
Tissue left on anti-roll plate

Remedies
Wipe with tissue, cool
Sharpen knife or move knife over.
Clean anti-roll plate with absolute alcohol and cool

30
Q

What to do if? Possible reasons/Remedies.

Cut sections are not as wide as tissue block (compression)

A 
Causes: 
- Tissue too warm
- Dull knife
Remedies:
- Chill tissue
- Sharpen knife
31
Q

What to do if? Possible reasons/Remedies.

Tissue shatters with fine cracks parallel to the knife edge

A

Causes: Tissue too cold when cut
Remedies: Check cryostat temperature gauge

32
Q

What are the major reasons for nicks and chattering?

A

Nicks are caused by imperfection on the blade. Chattering usually means something is not tight enough.

33
Q

What are some tips to handle fatty tissue (3)?

A
  1. May have to lower the temperature for fatty tissues. 2. Orient specimen so it hits the fat last.
  2. Need a very sharp blade.
34
Q

What can cause shattering?

A

Block may be too cold.

Histotechnology 1 (11 decks)

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