Skip to main content

Table 2 Summary of sample preparation techniques

From: X-ray computed tomography in life sciences

PreparationProtocolConsiderations
DryingAir drying, HDMS or critical point drying (for cells) and freeze drying (for tissues) [53]• Samples become very delicate
• Subsequent fixation not possible
• Long or thin parts prone to movement during scanning
• Compatible with electron microscopy in correlative imaging
Chemical fixation10% neutral buffered formalin [54]
1% glutaraldehyde in acetone [55]
Copenhagen mix (for plants: 70% absolute alcohol, 2% glycerol, 28% water) [41]
• Typically used before heavy metal staining to minimise sample shrinkage
• Imaging may be performed in liquid or air (typically ethanol or distilled water)
• Sample may move during scanning; measures to prevent movement such as packing with foam are advised
• If imaging in air, measures to prevent drying are advised (e.g. placing sample in sealed container with a small reservoir of liquid to maintain humidity)
EmbeddingResin [56] or wax [34]• Effective at preventing sample movement
• Good for samples with long or thin parts which may otherwise vibrate during scanning, causing blurred imaging
• Can be used with or without staining
• Resin compatible with block face serial sectioning for correlative imaging
FreezingFreezing [57] or vitrification [19]• Use of a cryo-stage is necessary during CT imaging of frozen samples
• Vitrification is typical for soft nCT as it minimises cryo-damage
Native tissueNo fixative, with staining [26]• Used to provide contrast whilst minimising change in tissue mechanical properties (iodine in phosphate buffered saline has been used for this purpose)
No fixative, no staining [58]• Fix and stain unsuited to some tissues due to uptake of fluid causing swelling, e.g. intervertebral disc