| Background&ObjectiveThe incidence of liver cancer increased year by year,70%-80%of which is hepatocellular carcinoma (HCC).Asian countries account for at least2/3of global HCC patients and China alone55%,the morbidity and mortality rate of China tops the world.70%-80%of HCC patients accompany with cirrhosis, HBV infection is a major factor. The complicated causes of HCC influence the choice of treatment. Surgical resection has been the preferred means, but due to the deterioration of liver function many patients are unable to select surgical resection, interventional treatment is necessary. Radiofrequency ablation (RFA) has been paid more and more attention, because it has advantages of minimal invasion, little pain, rare serious complication, repeated ablation and more thorough destruction to tumors. RFA requires a sufficiently large ablated lesion, including not only the neoplasm tissue, but also the relatively normal liver tissue of1cm around the tumor. A method by which the ablated area can be monitored simultaneously is required.Ultrasound elastography is a novel technique established by Ophir in1991, which is an important complement to the traditional ultrasound and makes up for the medical imaging modality. In the recent20years, Ultrasound elastography has developed rapidly and has become a hot research topic. Ultrasound elastography has been used for diagnosis of tumor, but it can also evaluate the ablated lesions. The heat leads the neoplasm tissue around the RF needle to form coagulation necrosis and the hardness increases. Ultrasound elastography can delineate the ablated area and has a high correlation with the gross specimen. However, the used experimental systems had various forms and were not able to apply clinically. The gas interference has not been studied yet.This study, applying the mature ultrasound elastography technology of Hitachi, was divided into two parts, in vitro experiment and clinical research. In pig liver radiofrequency ablation in vitro part,2D ultrasound and ultrasound elastography assessed the ablated lesion at three time points(Omin,30min,60min after the RFA ended) to explore if ultrasound elastography could assess the ablation area accurately and not be interferenced by gas. In the clinical studies, patients with liver cancer received RFA and strain rate ratio (SR) of liver lesions before and after RFA were compared to explore its initial value in the assessment of RFA for liver tumor.Materials and MethodsⅠ. Experimental Studies1Experimental materials:The fresh pig liver in vitro that the thickness was about3-5cm.2Experimental apparatus:Cool-tipTM RFA system(Valley lab, MA, USA),cool-tip RF electrode with a2-cm-long exposed electrode tip,HI-Vision900(Hitachi, Japan) with a3.5-13MHz linear probe.3Experimental methods:Performed RFA on pig liver in vitro by the same ablation parameters. The ablation process was monitored by2D ultrasound dynamically. Measured the long diameter (a) and transverse diameter (b) of the largest longitudinal section of the ablated lesions by2D ultrasound and elasticity imaging at three time points (0min,30min,60min after the ablation) and calculated the area and volume by ellipsoid volume formula:V=3.14/6×a×b×b=0.52×a×b2and ellipsoid area formula:S=(1/4)×3.14×a×b=0.785×a×b. All measured parameters were to take the average of three measurements. The above experiment was repeated nine times. Ⅱ. Clinical Studies1Clinical materials:Between October to December in2011,25patients with28lesions received RFA, clinic or liver biopsy being confirmed as HCC or metastatic liver cancer, in which21cases were HCC, four cases were metastatic liver cancer.18patients were male and7female,the mean age was50years, with a range of35to70years. The mean lesion diameter was3.3cm, with a range of2.5～4.0cm.24cases had solitary lesion, two cases had two lesions. The RFA treatment time was7～21min.2Experimental apparatus:Cool-tipTM RFA system(Valley lab, MA,USA),cool-tip RF electrode with a2or3-cm-long exposed electrode tip,HI-Vision900(Hitachi, Japan) with probe EUP-C532(4～8MHz), Mylab90(Esaote, Italy), Voluson730Expert (GE, Austria)3Experimental methodsObtained the elasticity image and measured the SR of liver lesion the day before and after RFA. Averaged five measurements.Ⅲ Statistic AnalysisAll statistical analyses were performed using SPSS17.0package. P-values less than0.05were considered significant.1In pig liver in vitro part, use single-factor analysis of variance (ANOVA), paired t-test and Pearson correlation analysis to analyze the long diameter, transverse diameter, area, volume of ablated lesions by2D ultrasound and ultrasound elastography at three different time points.2Compare SR of liver tumor before and after RFA with paired t-test.Results1. The cut surface of pig liver ablated lesions were oval, yellowish-white, the needle tract were in the center, narrow striped, a little black. Naked eye could clearly distinguish between the ablated lesion and surrounding tissue. Pathological microscopic examination showed liver cells of ablated lesion were coagulated necrosis, with clear boundaries with the surrounding liver tissue. 2Immediately after RFA,2D ultrasound images of the lesion were hyper echoic, with rear sound attenuation, because the acoustic shadow, the latter part of the ablated lesions were unclear, so transverse diameter couldn’t be measured. Long diameter was larger than the gross specimen.At30min,60min after ablation, the echo of2D ultrasound image decreased, the central needle tract area showed high echo, the edge between the ablated lesion and the surrounding tissue blurred. At30min, long diameter was greater than the gross specimen; transverse diameter had no significant difference with gross specimen. The maximum longitudinal section area of the ablation lesion was greater than the gross specimen; the volume has no significant difference with gross specimen. At60min, the long diameter, transverse diameter and area, volume of the ablated lesion had no significant difference with gross specimen. Transverse diameter and volume of2D image had relationship with gross specimen.3Before RFA, real-time ultrasound elastography image showed uniformly green. After RFA, the image showed the ablated lesions uniformly blue, the surrounding normal liver tissue still green, the boundary were clear.1group of9had poor imaging immediately after the ablation due to gas interference.SR at three time points were62.44±42.2,100.12±48.70,105.36±46.18and there was no significant difference.The long diameter, transverse diameter, area and volume from real-time ultrasound elastography image showed no significant different with gross specimen at different time points. There were high relation between elastography image and gross specimen (r>0.9, P<0.001) except the volume at30min.4SR of28liver tumors of25patients increased after RFA (6.68±2.55VS19.11±7.94)Conclusions1Real-time ultrasound elastography can delineate RF ablated lesion with certain interference of gas and has a high correlation with the gross specimen in pig liver in vitro. 2SR of liver cancer significantly increased after RFA, which maybe contribute to the assessment of RFA area.3Real-time ultrasound elastography may be a new imaging method for monitoring RFA of liver tumor. |
PDF Full Text Request