radiofrequency ablation ( rfa ) is a proven method of treatment of hepatocellular carcinoma ( hcc ) in patients who are not candidates for liver transplantation or those in whom surgical resection can not be performed . the major limitation of rfa has been the small volume of ablation of tumor and its dependence on imaging for planning , monitoring , and assessment of the final outcome . although there are studies in literature describing the use of contrast - enhanced ultrasound ( ce - us ) for rfa monitoring , these have used only visual interpretation of the pre- and post - procedural images . in india , contrast - enhanced computer tomography ( cect ) scan has been traditionally used as the imaging tool for the monitoring and follow - up of rfa . ce - us has recently been made available in our country , and we would like to report its use along with a software package to analyze contrast dynamics , for assessing treatment response , during rfa of liver hcc . a 55-year - old man who was hepatitis c virus hcv positive with cirrhosis ( child pugh b ) was found to have a 43.5-cm hypoechoic nodule in the left lobe of liver in segment 2 , on routine usg surveillance [ figure 1 ] . his alphafetoprotein afp level was 18 iu / ml . a prior usg guided fine - needle aspiration cytology had shown hcc . grey scale usg image shows a hypoechoic nodule ( arrow ) in the left lobe of the liver rfa was planned using conscious sedation with a cool tip rf system ( valleylab tyco , colorado , usa ) with a 200-kw generator and a 4-cm tip cluster electrode connected to a peristaltic pump with rotating rollers to push cold saline water to the tip of the electrode to achieve a uniform ablation zone . an intravenous line was maintained for sedation and for the injection of 2 ml of microbubbles ( sonovue , bracco , italy ) followed by 10 ml of saline . imaging was done using an acuson s2000 scanner ( siemens , mountain view , ca , usa ) with contrast pulse sequence technology , using a low mechanical index mi of 0.6 . all images were stored in a cine loop video of 130 frames and analyzed offline using dynamic contrast analysis software ( siemens ag ) . these images showed intense arterial enhancement of the hcc nodule in the arterial phase at 18 s [ figure 2a ] . the contrast dynamics evaluation showed marked arterial enhancement with a peak of 97.7% compared to peak enhancement of the normal liver parenchyma of 64.7% [ figure 2b , c ] . five minutes after the completion of ablation and before removing the rfa electrode , a baseline usg image was obtained , followed by ce - us with a second injection of 2 ml of sonovue followed by 10 ml saline . real - time images were acquired and stored as cine loop videos , in the arterial and portal phases , in the same way as the pre - procedure images and were then analyzed for contrast dynamics . the baseline pre - contrast post - rfa image showed the nodule to be hypoechoic with a peripheral echogenic rim of hemorrhage and necrosis , while the post ce - us image [ figure 3a ] showed no enhancement of the nodule in the arterial phase , with a markedly reduced contrast signal peak of only 0.4% on the contrast dynamics software [ figure 3b ] . following this , post - procedure recovery was uneventful , and the patient was discharged after 2 hours of observation . the first follow up of the patient was done at 3 months using ce - us and showed no arterial enhancement at the rfa scar site . pre - rfa evaluation . ce - us ( a ) shows the enhancing liver nodule ( arrow ) in the arterial phase . the contrast dynamics software shows analysis of the peak enhancement of the hcc nodule -97.7% ( b ) at 15 seconds compared tonormal liver enhancement pattern with peak enhancement of the normal liver of 64.7% ( c ) post - rfa evaluation . ce - us ( a ) shows a non - enhancing nodule ( arrow ) in the arterial phase . please note that the post - ablation contrast dynamics ( b ) of the hcc nodule shows no arterial ( 0.4% ) enhancement the final goal of all ablative treatments is to obtain complete necrosis of the malignant nodule by disruption of the blood supply to the tumor tissue . so far , cect has been used for the above purpose , and the absence of arterial enhancement has been the sine qua non of a successful procedure . however , there are limitations with the use of ct , namely the use of radiation , administration of iodinated contrast repeatedly , and the lack of real - time monitoring . any demonstration of residual enhancement / tumor tissue is an indication to perform the rfa again , preferably in the same session . so far , ce - us is the only imaging modality that not only monitors the procedure in real time but also accurately shows the treatment response at the end of the procedure . to be able to improve the differentiation between complete and incomplete treatment response , the use of second - generation contrast agents like perfluoro agents has been suggested , and the images can now be analyzed using dedicated contrast dynamics software programs , as shown in our patient . in our initial experience , we felt that this was of tremendous help to the operator and helped him decide immediately whether a further rfa session was required or not even before the electrodes were removed . earlier studies using first- and second - generation usg contrast have also reported a higher specificity of ce - us , namely 94% , to assess immediate post - procedure tumor response , while cect shows a much lower specificity , namely 20% to 24% . the reasons for the latter have been reported to be the presence of peripheral hyperemia , the presence of gas , and the uncooperative nature of patients while on the ct scan gantry table . ce - us has so far been used for rfa only in limited institutes world wide mainly due to the lack of availability of ultrasound contrast media and dedicated ce - us hardware and software . however , these limitations are offset by the reduced cost of ce - us vis a vis cect ( using 1:2 ) . the case highlights the usefulness of ce - us as an imaging modality to monitor rfa in patients with hcc . with the use of contrast dynamics analysis , one can accurately detect the presence of any residual tumor immediately at the end of the procedure . our initial experience suggests high operator comfort and patient ease during ablation with improved visualization of the end point of the procedure with the use ce - us .
radiofrequency ablation ( rfa ) of hepatocellular carcinoma ( hcc ) is an established alternative treatment to surgery and intra - arterial chemotherapy , usually performed under contrast - enhanced ct scan guidance . 
 we describe our experience with the use of contrast - enhanced ultrasound and contrast dynamics analysis for planning and monitoring rfa in a patient with hcc .