"mechanical: closer to the cryoprobe, the lowest (up to -40 degrees Celsius) temperatures are achieved. A sudden temperature drop translates into intracellular ice formation, damaging intracellular organelles and the cell wall 4."
"osmotic: more peripherally, relatively higher temperatures (-20 to 0 degrees Celsius) might be unable to create intracellular ice but can form ice crystals in the extracellular compartment. In the following thawing cycle, the newly liquified, electrolyte-rich interstitial fluid can passively diffuse into the cells suddenly altering their concentration of solutes and key metabolic processes 4. For this reason, the thawing cycle is an absolutely crucial part of the cryoablation procedure."
"ischaemic: local hypothermia is expected to have an effect on blood and oxygen supply, exacerbating the tissue damage during the ablation process7."
"immunologic: animal studies have suggested a possible sensitisation of the immune system, that would then target and destroy residual sublethally injured tumour tissue 8. This theory however is disputed and not widely accepted."
"under sterile conditions, verify that there is no gas leak from the cryoprobes by inserting them in water."
"ensure that cooling and active heating are functional."
"US or CT-guided insertion of cryoprobes in the lesion - the number of cryoprobes and location depend on the size of the lesion."
"the injection of CO2 in the epidural space to protect the spinal cord."
"ablation zone achievable with cryoablation is smaller than the one created with radiofrequency ablation or microwave ablation; this means that more probes are required, increasing the complication rates."
"ischaemic: local hypothermia is expected to have an effect on blood and oxygen supply, exacerbating the tissue damage during the ablation process7."
"immunologic: animal studies have suggested a possible sensitisation of the immune system, that would then target and destroy residual sublethally injured tumour tissue 8. This theory however is disputed and not widely accepted."
"Freeze–thaw cycles"
"requires accurate needle placement between structures which may be ineffective in osteolytic lesions, post-operative adhesions or post-radiotherapy cases"
"it is reported to be less painful in the post-intervention period compared to other ablation techniques 3"
"similar to radiofrequency or microwave ablation interventions cryoablation can also result in post-ablation syndrome; a flu-like illness due to systemic response very rarely"
"US or CT-guided insertion of cryoprobes in the lesion - the number of cryoprobes and location depend on the size of the lesion."
"Freeze–thaw cycles"
"They are variable, depending on location of the lesion, institutions and operators."
"Freezing for 3 min, then 2 min of passive heating, 1 min of active heating, 7 min of freezing - after this cycle a CT control may be performed"
"Passive heating for 6 min, active heating for 1 min, freezing for 10 min"
"Active heating and removal of cryoprobes"
Expected headings
"Mechanism of action"
"Cryoprobe design"
"Imaging"
"Prevention of complications"
"Advantages"
"Disadvantages"
"During cryoablation, one or more specifically designed needles (cryoprobes) are placed under direct imaging in the desired area. Tumour destruction is thought to be achieved via different mechanisms:"
"They are variable, depending on location of the lesion, institutions and operators."
"The key element of the cryoprobe is an expansion chamber, located at the end of the needle. Exploiting the Joule-Thompson effect (i.e. compression or expansion of gases results in a change in their temperature), a cryogenic gas (usually argon) is allowed to expand at the tip of the needle, thus lowering its temperature. The opposite occurs in the thawing phase, where argon is replaced by another agent (e.g. helium) with opposite properties (e.g. helium, which increases in temperature during expansion)."
"The key element of the cryoprobe is an expansion chamber, located at the end of the needle. Exploiting the Joule-Thompson effect (i.e. compression or expansion of gases results in a change in their temperature), a cryogenic gas (usually argon) is allowed to expand at the tip of the needle, thus lowering its temperature. The opposite occurs in the thawing phase, where argon is replaced by another agent (e.g. helium) with opposite properties (e.g. helium, which increases in temperature during expansion)."
"The shape and size of the ablation zone depend on the tissue characteristics, as well as the number and properties of the cryoprobes. On ultrasonography, it is seen as a hyperechoic line with posterior acoustic shadowing, mirroring the surface of the ice ball; on CT, it is a well defined water density low-attenuation region. Its hallmark on MRI is a flow-void region 9."
"ablation zone achievable with cryoablation is smaller than the one created with radiofrequency ablation or microwave ablation; this means that more probes are required, increasing the complication rates."
"cryoablation is more time-consuming; in addition to the need for multiple probes, a typical procedure would require two freezing cycles with a thawing phase in between (versus, for example, a single 2-minute cycle during an MWA procedure)"
"similar to radiofrequency or microwave ablation interventions cryoablation can also result in post-ablation syndrome; a flu-like illness due to systemic response very rarely"