the last few years have seen a rapid expansion in the use and availability of ablation techniques with hundreds of papers published . radiofrequency ( rf ) remains the frontrunner in terms of cost , ease of set - up , versatility and flexibility but other techniques are catching up . ablation with cryotherapy and microwave , which were previously only available at open laparotomy due to the large size of the probes , are now readily performed percutaneously , with a predictable reduction in morbidity . cryotherapy offers the opportunity to monitor the ice - ball with ultrasound ( us ) , computed tomography ( ct ) or magnetic resonance imaging ( mri ) . cell death occurs around 40c and this isotherm lies approximately 5  mm inside the ice - ball . more powerful microwave generators have been developed and active research into better impedance matching with specific tissues should result in improved performance . microwave has several theoretical advantages ; it can be designed to share a spherical geometry with most tumours and has a more predictable dose  response curve . simultaneous use of multiple energy sources ( probes / electrodes ) is now available in all the different technologies . improvements in guidance include the development of real - time co - registration techniques , most commonly ct and us . five percent dextrose is instilled into the area adjacent to the ablation to displace vulnerable structures , usually bowel , away from the ablation zone . a displacement of as little as 1  cm is enough to protect the bowel . ablation is now accepted as the first line of treatment in patients with limited volume hepatocellular carcinoma ( hcc ) who are not candidates for transplantation . there is continuing debate in most other areas but the evidence is increasing for an important role in liver metastases , renal carcinoma , inoperable lung tumours and some bone tumours . nephron - sparing surgery presents a challenge to the surgeon . yet , there is increasing evidence that even moderate degrees of renal failure can significantly affect survival following cardiovascular events . this will increase the focus of all physicians on the need to preserve renal function wherever and whenever possible . one study found that 95.2% of patients had a glomerular filtration rate ( gfr ) > 60 ml / min per 1.73 m at 3 years post rfa compared with 70.7% post partial nephrectomy and only 39.9% post radical nephrectomy . therefore patients with a solitary kidney and others with borderline renal function will increasingly be treated with ablation . renal tumours up to 3.5  cm in diameter can be destroyed in situ by laser , rf or cryotherapy with virtually no damage to the surrounding normal renal tissue . multiple renal tumours are not rare and can be difficult to resect without complications but complications are rare after ablation , particularly if a percutaneous approach is used . bowel injury can be prevented by dextrose isolation but it remains necessary to maintain a distance of > 1  cm from the proximal ureter or cool the ureter via a stent as ablation can cause stricturing . several series have now been published including one retrospective comparison with partial nephrectomy which showed comparable oncologic efficacy albeit with a shorter mean follow - up in the radiofrequency group ( 30 months versus 47 months ) . an apparently promising meta - analysis was heavily skewed away from recent innovations by the inclusion of early technology , failure to analyse by tumour size and location , and the stipulation that success after a single procedure was the main endpoint . percutaneous ablative techniques are relatively easy to repeat compared with either surgery or laparoscopic cryotherapy . the question as to whether cryotherapy or radiofrequency is better is yet to be resolved and would be better addressed with mature technology and in a specific tumour cohort , e.g. tumours < 3.5  cm . this is predicted to be the single largest growth area in ablation over the next few years . good results can be achieved in small , peripheral tumours . both inoperable primary and limited numbers of metastatic tumours computed tomography fluoroscopy facilitates electrode placement as small , scirrhous lung lesions can be difficult to penetrate with a larger calibre needle . pneumothorax occurs in about 40% , a similar incidence to that seen with trucut biopsy , but only a small percentage ( 1015% ) require drainage . the likelihood of a pneumothorax increases with the length of aerated lung that is traversed by the electrode and is more common when treating multiple tumours . infection is an unusual complication and in our series only occurred in patients with underlying asthma or chronic obstructive airways disease . cavitation does not usually indicate infection but cavitating lesions are more likely to become infected . during treatment a penumbra of ground glass opacification ( ggo ) develops around the tumour representing the ablation zone and a surrounding inflammatory reaction . histological studies have shown that the zone of cell death lies 24  mm inside the outer margin of the ground glass shadowing . this has been corroborated in a clinical study , with > 6 months follow - up , where the width of ggo at treatment was correlated with the development and location of recurrence . a minimum ggo of 4.5  mm is recommended to ensure complete ablation . over time the ablation zone becomes increasingly dense and then reduces in size . at 12 months , up to 33% of successfully treated small lesions will have shrunk to a linear scar . recurrence is identified by enlargement of the ablation zone , or a change in the shape of the zone indicating enlargement in one area or the development of focal nodular enhancement . tumours < 3.0  cm can usually be ablated at a single session , larger tumours , 3.05.0  cm , may require more than one ablation or other additional therapy . multivariate analysis has shown size to be the dominant feature determining complete ablation , but contact with > 3  mm blood vessels or bronchi also increases the chance of recurrence . current indications include patients with small volume , but inoperable metastases and early primary lung cancer in medically inoperable patients . early clinical studies report 3- and 5-year survival of between 46% and 57% in patients with colorectal metastases , . combinations of radiotherapy and rfa have been used to good effect in primary lung cancer in inoperable patients . the rapture study showed that lung function recovered quickly after an initial immediate post - treatment reduction and was maintained at pre - treatment values 12 months later . one of the first accepted indications for ablation was the minimally invasive treatment of benign osteoid osteomas . malignant primary bone tumours are usually treated by chemotherapy , radiotherapy and surgery . however , if aggressive therapy is delivered at an early stage , recurrence can be very difficult to treat . treatment by rfa may be curative , but is more likely to form part of a palliative treatment regimen . ct or mr radiofrequency ablation and cryoablation have been advocated in the symptomatic palliation of bone metastases following radiotherapy . initial results suggest that ablation can produce significant reductions in pain levels and analgesic requirements . it is important to select patients with a clearly defined and understood dominant site of bone pain . some authors promote the combination of ablation and cementoplasty , others argue that cementoplasty alone would be adequate . nephron - sparing surgery presents a challenge to the surgeon . yet , there is increasing evidence that even moderate degrees of renal failure can significantly affect survival following cardiovascular events . this will increase the focus of all physicians on the need to preserve renal function wherever and whenever possible . one study found that 95.2% of patients had a glomerular filtration rate ( gfr ) > 60 ml / min per 1.73 m at 3 years post rfa compared with 70.7% post partial nephrectomy and only 39.9% post radical nephrectomy . therefore patients with a solitary kidney and others with borderline renal function will increasingly be treated with ablation . renal tumours up to 3.5  cm in diameter can be destroyed in situ by laser , rf or cryotherapy with virtually no damage to the surrounding normal renal tissue . multiple renal tumours are not rare and can be difficult to resect without complications but complications are rare after ablation , particularly if a percutaneous approach is used . bowel injury can be prevented by dextrose isolation but it remains necessary to maintain a distance of > 1  cm from the proximal ureter or cool the ureter via a stent as ablation can cause stricturing . several series have now been published including one retrospective comparison with partial nephrectomy which showed comparable oncologic efficacy albeit with a shorter mean follow - up in the radiofrequency group ( 30 months versus 47 months ) . an apparently promising meta - analysis was heavily skewed away from recent innovations by the inclusion of early technology , failure to analyse by tumour size and location , and the stipulation that success after a single procedure was the main endpoint . percutaneous ablative techniques are relatively easy to repeat compared with either surgery or laparoscopic cryotherapy . the question as to whether cryotherapy or radiofrequency is better is yet to be resolved and would be better addressed with mature technology and in a specific tumour cohort , e.g. tumours < 3.5  cm . this is predicted to be the single largest growth area in ablation over the next few years . good results can be achieved in small , peripheral tumours . both inoperable primary and limited numbers of metastatic tumours computed tomography fluoroscopy facilitates electrode placement as small , scirrhous lung lesions can be difficult to penetrate with a larger calibre needle . pneumothorax occurs in about 40% , a similar incidence to that seen with trucut biopsy , but only a small percentage ( 1015% ) require drainage . the likelihood of a pneumothorax increases with the length of aerated lung that is traversed by the electrode and is more common when treating multiple tumours . infection is an unusual complication and in our series only occurred in patients with underlying asthma or chronic obstructive airways disease . cavitation does not usually indicate infection but cavitating lesions are more likely to become infected . during treatment a penumbra of ground glass opacification ( ggo ) develops around the tumour representing the ablation zone and a surrounding inflammatory reaction . histological studies have shown that the zone of cell death lies 24  mm inside the outer margin of the ground glass shadowing . this has been corroborated in a clinical study , with > 6 months follow - up , where the width of ggo at treatment was correlated with the development and location of recurrence . a minimum ggo of 4.5  mm is recommended to ensure complete ablation . over time the ablation zone becomes increasingly dense and then reduces in size . at 12 months , up to 33% of recurrence is identified by enlargement of the ablation zone , or a change in the shape of the zone indicating enlargement in one area or the development of focal nodular enhancement . tumours < 3.0  cm can usually be ablated at a single session , larger tumours , 3.05.0  cm , may require more than one ablation or other additional therapy . multivariate analysis has shown size to be the dominant feature determining complete ablation , but contact with > 3  mm blood vessels or bronchi also increases the chance of recurrence . current indications include patients with small volume , but inoperable metastases and early primary lung cancer in medically inoperable patients . early clinical studies report 3- and 5-year survival of between 46% and 57% in patients with colorectal metastases , . combinations of radiotherapy and rfa have been used to good effect in primary lung cancer in inoperable patients . the rapture study showed that lung function recovered quickly after an initial immediate post - treatment reduction and was maintained at pre - treatment values 12 months later . one of the first accepted indications for ablation was the minimally invasive treatment of benign osteoid osteomas . malignant primary bone tumours are usually treated by chemotherapy , radiotherapy and surgery . however , if aggressive therapy is delivered at an early stage , recurrence can be very difficult to treat . treatment by rfa may be curative , but is more likely to form part of a palliative treatment regimen . ct or mr radiofrequency ablation and cryoablation have been advocated in the symptomatic palliation of bone metastases following radiotherapy . it is important to select patients with a clearly defined and understood dominant site of bone pain . some authors promote the combination of ablation and cementoplasty , others argue that cementoplasty alone would be adequate . a trial to establish the relative merits of the two techniques the last few years have seen a sharp increase in our understanding of ablation , maturation of the technology , an improvement in the safety profile , ablation efficacy and monitoring techniques and the publication of results in larger patient cohorts . ablation will soon be sufficiently established to allow trials comparing ablation with conventional therapies in specific patient groups .
abstractthe last few years have seen a rapid expansion in the use and availability of ablation techniques with hundreds of papers published . 
 radiofrequency remains the front - runner in terms of cost , ease of set - up , versatility and flexibility but other techniques are catching up . 
 ablation with cryotherapy and microwave , which were previously only available at open laparotomy due to the large size of the probes , are now readily performed percutaneously , with a predictable reduction in morbidity . 
 ablation is now accepted as the first line of treatment in patients with limited volume hepatocellular carcinoma who are not candidates for transplantation . 
 there is continuing debate in most other areas but the evidence is increasing for an important role in liver metastases , renal carcinoma , inoperable lung tumours and some bone tumours .