Cryostats are used to preserve and cut human, animal or plant tissue specimens for study under a microscope. Cryostats combine the functions of a tissue processor(link) and a microtome(link) but are used when rapid analysis is desired – such as in an operating room, which requires a quick freezing of specimens. A cryostat consists of:
- A cryochamber that can hold up to 10 specimen disks.
- A stainless-steel rotary microtome that cuts specimens in a thickness range of 1 to 50 micrometers (microns).
- A refrigerant, either thermoelectrical or from a gas like that found in an automobile (or both).
- A drainage tube for waste liquid that is collected outside of the cryostat.
- A control panel.
The operator places the specimen holder in the cryochamber and selects the temperature typically in a range from zero to -30 degrees Celsius. The specimen, which can be frozen within minutes, is then cut on the microtome manually. This provides a 3-D orientation of up to 8 degrees in each direction. The specimen is finally mounted on a slide for viewing under a microscope.
Cryostat common problems:
- Cryochamber doesn’t cool sufficiently. This will cause poor sectioning and a potential misdiagnosis.
- Cryochamber doesn’t reach the set temperature. This will cause poor sectioning and a potential misdiagnosis.
- Microtome cuts too thick or too thin. This could cause a misdiagnosis depending on the slide reader. A cut that’s too thin could also cause the tissue to fall apart and not adhere to the slide.
- Excessive chatter/noise. This will cause a nuisance, but it could mean that something is loose and result in poor sectioning.
- Poor sectioning. This could cause a misdiagnosis depending on the slide reader.
- Manual handwheel is difficult to turn. This could lead to repetitive-stress injury in the operator.
- Peltier unit in thermoelectrical models doesn’t operate correctly. This will cause such units to not supercool and slow down the diagnosis process from about 1 minute to 5 to 10 minutes, which can be a long time in an operating room.
- No power to the cryostat. This will cause the instrument to not operate properly or at all.
- Compressor doesn’t operate. This will prevent the cryochamber from cooling sufficiently and lead to poor sectioning and a potential misdiagnosis.
- Fan doesn’t operate. This will prevent the cryochamber from cooling sufficiently and lead to poor sectioning and a potential misdiagnosis.
In the case of error codes on the tissue processor control panel display, please refer to the product user manual. Different manufacturers use different codes and have different troubleshooting steps. In the case of a loss of power, remember to check circuit breakers or fuses.
When a Tech One technician is needed to make repairs, the technician will diagnose the problem and make appropriate repairs. The typical service call is 1–3 hours; however, because a cryostat requires precision, service calls might take longer than expected to make sure the instrument is aligned properly after a repair.
Cryostat maintenance tips:
- Make sure to keep the area around the cryostat clear, so it can pull in and blow out air.
- Clean all components daily – particularly the knife holder and specimen holder.
- Make sure that anything requiring locking down is locked down properly.
- Empty the waste bottles each night.
- Call a Tech One technician for assistance.
Cryostat makes & models Tech One repairs:
- Avantik: QS11, QS12
- IEC: Minotome Plus
- Leica Biosystems: CM1510 S, CM1800, CM1850, CM1860, CM1900, CM1950, CM3050 S
- Microm: HM 325, HM 505 E, HM 505 EP, HM 550, HM 550 VP, HM 560 MV
- Sakura: Tissue-Tek Cryo3, Tissue-Tek Cryo 2000, Tissue Tek 4553
- Thermo Scientific / Shandon: AS620, Cryotome E, Cryotome FSE, Cryotome SME
- Design: Cryostats are contained in cabinets that are movable on rollers. Two adjustable feet at the front ensure a safe stand.
- Speed vs. Accuracy: Although cryostats provide faster results – roughly 15 minutes compared with 15 hours when done at room temperature through a tissue processor and microtome – the quality of the specimen is often poor by comparison.
- Peltier units: Cryostats that include this small device (roughly 2”x2”) can freeze samples at 30 degrees C lower than cryostats without This provides a more rapid cut and diagnosis – which is particularly valuable in an operating room.