Colin J. McCarthy, MB, BCh, BAO, MRCSI, FFR (RCSI); Raul N. Uppot, MD; Christos Georgiades, MD, PhD
To access 4,300 diagnoses written by the world's leading experts in radiology, please log in or subscribe.Log inSubscribe
KEY FACTS
Terminology
Preprocedure
Post Procedure
Outcomes
Procedure
TERMINOLOGY
Definitions
Ablation: Direct application of chemical or thermal therapies to tumors for tissue destruction
Overall survival (OS): Length of time from either date of diagnosis or start of treatment for disease, such as cancer, to date of death of any cause
Usually expressed in median ± standard deviation
Cancer-specific survival (CSS): Length of time from either date of diagnosis or start of treatment for disease, such as cancer, to date of death from disease
Patients who die from causes unrelated to disease are not counted in this measurement
Progression-free survival: Length of time (from set point, usually treatment) that patient demonstrates no disease progression
Time to progression: Length of time (from set point, usually treatment) until patient shows disease progression
Mortalities are excluded
Disease-free survival (DFS): Length of time after treatment, until patient dies or shows evidence for recurrent disease
Ablation Modalities
Radiofrequency ablation (RFA)
Physics
Relies on electrical conduction through tissue for heat generation
Closed circuit necessary for conduction; body acts as resistor
Direct radiofrequency heating
Occurs within millimeters of applicator needle
Thermal conduction
Heat transfer more distally; therefore, good thermal conductivity crucial for large ablation
Quick charring (dehydration) of tissue increases resistance, opens circuit, and limits ablation zone
Slow, gradual "cooking" more effective than fast ablation
Common current frequency of 400-500 kHz
Disadvantages
Irregular ablation shape, depends on thermal conductivity of tissue
Charring limits effectiveness
Heat sink effect
Flow of blood in nearby vessels cools tissue, limiting effectiveness
Impedance (instead of temperature) regulating systems may lengthen total procedure time and increase ablation zone
Grounding pads required for monopolar systems
May require slow and lengthy treatment to effectively kill tumor
Microwave ablation (MWA)
Physics
Relies on dielectric heating
Alternating electromagnetic (EM) field applied to imperfect dielectric material (tissue); forces water molecules in tissue to oscillate
Water molecules oscillate out of phase with EM field
Frictional energy loss generates heat
Higher water content = better heat absorption and conductivity = larger ablation zone
Frequencies often 915 MHz or 2.45 GHz
Relative permittivity: How well materials accept EM field (capacitance)
Lower the permittivity, the less movement of energy from source dispersed through tissues
Low relative permittivity: Bone, spleen
High relative permittivity: Muscle, lung, liver
Effective conductivity: How well tissue absorbs microwave energy
Lower the conductivity, the higher thermal energy deposited locally, and the more effective ablation around antennae
Low conductivity: Bone, lung, liver
High conductivity: Muscle, blood, spleen
Advantages
Ablation volume is more predictable, as it does not depend on thermal conductivity of tissue
Can pass through and heat tissue at any temperature or water content
Less susceptible to heat sink by producing larger areas of active heating
Does not require grounding pads
Cryoablation
Physics
Relies on Joules-Thomson effect
Compressed gas circulates within double-barreled probe
Gas released within probe results in sudden pressure drop
Resultant temperature drop cools surrounding tissues
Process consists of alternate freezing and thawing of tissue (commonly 10 minutes, 8 minutes, 10 minutes)
Multifaceted cellular death mode: Cell membrane fracture, apoptosis, vessel thrombosis/ischemia
Argon gas
Each probe has characteristic isotherms (size and shape of surface with same temperature)
Temperatures drop to ~ -150°C at probe
Heat pump effect: Nearby vessels may increase temperature and limit ablation margin
Advantages
Well tolerated (minimal pain)
"Ice ball" readily visible with CT (US/MR) guidance
Represents 0°C isotherm (not lethal)
Lethal isotherm (-20°C) ~ 5 mm inside visible "ice ball"
Operator can sculpt irregularly shaped ablation zone by altering orientation of multiple probes
Disadvantages
More expensive, as multiple probes may be required
System requires gas availability and storage
PREPROCEDURE
Indications
Contraindications
Preprocedure Imaging
Getting Started
PROCEDURE
Patient Position/Location
Baseline Imaging and Planning
Probe Insertion/Positioning
Added Maneuvers
Intraprocedural Monitoring of Patient and Treatment
Completion Imaging
Recovery
POST PROCEDURE
Things to Do
OUTCOMES
Complications
Selected References
Burke CJ et al: Ultrasound-guided therapeutic injection and cryoablation of the medial plantar proper digital nerve (Joplin's Nerve): sonographic findings, technique, and clinical outcomes. Acad Radiol. ePub, 2019
Ferrer-Mileo L et al: Efficacy of cryoablation to control cancer pain: a systematic review. Pain Pract. 18(8):1083-98, 2018
Sujka J et al: Outcomes using cryoablation for postoperative pain control in children following minimally invasive pectus excavatum repair. J Laparoendosc Adv Surg Tech A. 28(11):1383-6, 2018
Marshall RH et al: Feasibility of intraoperative nerve monitoring in preventing thermal damage to the "nerve at risk" during image-guided ablation of tumors. Cardiovasc Intervent Radiol. 39(6):875-84, 2016
Ahmed M et al: Image-guided tumor ablation: standardization of terminology and reporting criteria--a 10-year update: supplement to the consensus document. J Vasc Interv Radiol. 25(11):1706-8, 2014
Kurup AN et al: Neuroanatomic considerations in percutaneous tumor ablation. Radiographics. 33(4):1195-215, 2013
Callstrom MR et al: Painful metastases involving bone: feasibility of percutaneous CT- and US-guided radio-frequency ablation. Radiology. 224(1):87-97, 2002
Related Anatomy
Loading...
Related Differential Diagnoses
Loading...
References
Tables
Tables
KEY FACTS
Terminology
Preprocedure
Post Procedure
Outcomes
Procedure
TERMINOLOGY
Definitions
Ablation: Direct application of chemical or thermal therapies to tumors for tissue destruction
Overall survival (OS): Length of time from either date of diagnosis or start of treatment for disease, such as cancer, to date of death of any cause
Usually expressed in median ± standard deviation
Cancer-specific survival (CSS): Length of time from either date of diagnosis or start of treatment for disease, such as cancer, to date of death from disease
Patients who die from causes unrelated to disease are not counted in this measurement
Progression-free survival: Length of time (from set point, usually treatment) that patient demonstrates no disease progression
Time to progression: Length of time (from set point, usually treatment) until patient shows disease progression
Mortalities are excluded
Disease-free survival (DFS): Length of time after treatment, until patient dies or shows evidence for recurrent disease
Ablation Modalities
Radiofrequency ablation (RFA)
Physics
Relies on electrical conduction through tissue for heat generation
Closed circuit necessary for conduction; body acts as resistor
Direct radiofrequency heating
Occurs within millimeters of applicator needle
Thermal conduction
Heat transfer more distally; therefore, good thermal conductivity crucial for large ablation
Quick charring (dehydration) of tissue increases resistance, opens circuit, and limits ablation zone
Slow, gradual "cooking" more effective than fast ablation
Common current frequency of 400-500 kHz
Disadvantages
Irregular ablation shape, depends on thermal conductivity of tissue
Charring limits effectiveness
Heat sink effect
Flow of blood in nearby vessels cools tissue, limiting effectiveness
Impedance (instead of temperature) regulating systems may lengthen total procedure time and increase ablation zone
Grounding pads required for monopolar systems
May require slow and lengthy treatment to effectively kill tumor
Microwave ablation (MWA)
Physics
Relies on dielectric heating
Alternating electromagnetic (EM) field applied to imperfect dielectric material (tissue); forces water molecules in tissue to oscillate
Water molecules oscillate out of phase with EM field
Frictional energy loss generates heat
Higher water content = better heat absorption and conductivity = larger ablation zone
Frequencies often 915 MHz or 2.45 GHz
Relative permittivity: How well materials accept EM field (capacitance)
Lower the permittivity, the less movement of energy from source dispersed through tissues
Low relative permittivity: Bone, spleen
High relative permittivity: Muscle, lung, liver
Effective conductivity: How well tissue absorbs microwave energy
Lower the conductivity, the higher thermal energy deposited locally, and the more effective ablation around antennae
Low conductivity: Bone, lung, liver
High conductivity: Muscle, blood, spleen
Advantages
Ablation volume is more predictable, as it does not depend on thermal conductivity of tissue
Can pass through and heat tissue at any temperature or water content
Less susceptible to heat sink by producing larger areas of active heating
Does not require grounding pads
Cryoablation
Physics
Relies on Joules-Thomson effect
Compressed gas circulates within double-barreled probe
Gas released within probe results in sudden pressure drop
Resultant temperature drop cools surrounding tissues
Process consists of alternate freezing and thawing of tissue (commonly 10 minutes, 8 minutes, 10 minutes)
Multifaceted cellular death mode: Cell membrane fracture, apoptosis, vessel thrombosis/ischemia
Argon gas
Each probe has characteristic isotherms (size and shape of surface with same temperature)
Temperatures drop to ~ -150°C at probe
Heat pump effect: Nearby vessels may increase temperature and limit ablation margin
Advantages
Well tolerated (minimal pain)
"Ice ball" readily visible with CT (US/MR) guidance
Represents 0°C isotherm (not lethal)
Lethal isotherm (-20°C) ~ 5 mm inside visible "ice ball"
Operator can sculpt irregularly shaped ablation zone by altering orientation of multiple probes
Disadvantages
More expensive, as multiple probes may be required
System requires gas availability and storage
PREPROCEDURE
Indications
Contraindications
Preprocedure Imaging
Getting Started
PROCEDURE
Patient Position/Location
Baseline Imaging and Planning
Probe Insertion/Positioning
Added Maneuvers
Intraprocedural Monitoring of Patient and Treatment
Completion Imaging
Recovery
POST PROCEDURE
Things to Do
OUTCOMES
Complications
Selected References
Burke CJ et al: Ultrasound-guided therapeutic injection and cryoablation of the medial plantar proper digital nerve (Joplin's Nerve): sonographic findings, technique, and clinical outcomes. Acad Radiol. ePub, 2019
Ferrer-Mileo L et al: Efficacy of cryoablation to control cancer pain: a systematic review. Pain Pract. 18(8):1083-98, 2018
Sujka J et al: Outcomes using cryoablation for postoperative pain control in children following minimally invasive pectus excavatum repair. J Laparoendosc Adv Surg Tech A. 28(11):1383-6, 2018
Marshall RH et al: Feasibility of intraoperative nerve monitoring in preventing thermal damage to the "nerve at risk" during image-guided ablation of tumors. Cardiovasc Intervent Radiol. 39(6):875-84, 2016
Ahmed M et al: Image-guided tumor ablation: standardization of terminology and reporting criteria--a 10-year update: supplement to the consensus document. J Vasc Interv Radiol. 25(11):1706-8, 2014
Kurup AN et al: Neuroanatomic considerations in percutaneous tumor ablation. Radiographics. 33(4):1195-215, 2013