| Objective. The aim of this study is to investigate the effect of radiofrequency ablation on the in vivo or vitro renal tissue and to evaluate the veracity of ultrasonography measurement in renal radiofrequency, so as to supply a basic for the clinical use of RF in renal disease.Methods: Six rabbits were involved in the vivo experiment. Another ten vitro kidneys were used in vitro experiment. The kidneyswere exposed after anesthesia and then the electrode was insert in the pole of the kidney. Radio frequency ablation was performed with different original power(10W. 20W, 30W 40W respectively) and with the cluster electrode scattered to different size(0.5 cm and 1cm respectively). The time of ablation was recorded. The kidneys were resected and scaned with ultrasonography. The parameters were recorded. The specimen was then excided and measured anatomically. The results measured by ultrasonography were compared with those measured by anatomic method.The specimen was also fixed with 10% formaldehyde, imbeded in paraffin, sectioned and evaluated with HE staining. Different zones of the thermal ablation lesion were photographed for correlation and interpretations of the observed changes on imaging.Results: (1)RF with cluster electrode could generate coagulative necrosis area with clear margin in renal tissue. The ablated focus are regular global or ellipsoidal in the vitro kidneys, while they exhibits as various shapes in the in vivo kidneys, including sphericity, ellipsoid, cone and tear-shape, et al. Shortly after RF, the following components could be identified on the cross-section of the kidney: zone A, a carbonized area; zone B: a large pale area of tumoral coagulative necrosis; zone C: a outer band corresponding to congestion and hemorrhage and edema. (2)Less time was needed to reach peack impedance with greater original power then that with smaller original power. With the same electrode size and original power, vivo condition seemed to need more time to reach the peak impedance.?The difference between ultrasonographical and anatomical size of lesions was significant vivo but non-significant vitro. It seemed that lesion vivo were larger than that of vitro on the same condition (KO. 05).Conclusion : RF with cluster electrode could generate coagulative necrosis area with dear margin in renal tissue while spare part of the kidney.The size and shape of ablation lesion is related to the renal blood condition. Low original power is considered in plenty blood supplied tissue to get larger lesion area, but expanding space of radiofrequency coagulation in renal tissue demands caution. Because of the interfering of the microbubble generated during ablation and the hyperecho of renal sinus, ultrasonography is prone to overestimate or underestimate of lesion size at the instant moment of ablation.Objective: In the present study, we evaluated the feasibility, effectiveness and safty of percutaneous radio-frequency ablation using cluster electrode guided by ultrasonography in a rabbit renal tumor model.Methods: To generate a renal VX2 tumor model with VX2 cells. Ultrasonography was used to monitor the formation of tumor. Then 42 rabbits carrying renal VX2 tumor in right kidney were divided into treated group and control group randomly (27 and 15 respectively) . Radiofrequency ablation under the guidance of ultrasonography was performed in the treated group. The tumors were evaluated by two-dimensional ultrasonography for the changes of the shape and the echo pre-treatment, during the course of treatment and post-treatment (3d, 1w, 2w and 3w respectively). Vein blood was also took at the same time point for to investigate kidney function. Two rabbits from each group were sacrificed at each time point and the other rabbits died naturally. Necropsy was performed on all the animals after the death and the kidney with tumor was resected for the measurement of tumor volume. Specimen of ablated area, normal tissue and inteRFce area was collected for pathologic examination. Five rabbits from treated group were also selected randomly andunderwent CT and DSA examination pre- and post-operation. The state of tumors, the metastasis rate and the survival rate were compared between the two groups.Results: ?Paracentesis was performed successfully on all the animals and the treating time was 27-220 seconds. The tumor growth in rabbits was 100%(42/42). In the 27 rabbits in the treated group, 31 tumor were generated, which received RF treatment later. The difference of survival time between the treated group and control was significant[(45.1±9.5)d vs (33.7±6.9)d, PO.05], There was fewer metastasis nodes found in lung of the treated rabbits compared to the untreated animal. ?Since 3 days after operation the size of tumors in the treated group was smaller than the one in control group (p<0.05). The tumor grew rapidly 3 weeks after implantation in the untreated animal. The growth velocity of tumors in the treated group was slower than that of control group. The recurrent or residual tumor began to grow one week after treatment but very slowly. ?Shortly after RF, the ablated focus presented as pale or white coagulative tissue. Under microscopy, there was coagulative necrosis with congestion and hemorrhage in the centre of the ablated focus. The necrosis area enlarged with fibrotic hyperplasia, and congestion and inflammatory reaction in the surrounding area reduced with time went by. ? With CT scanning, the density of ablated lesion increased slightly. Enhanced CT scanning showed clear margin surrounding the tumor; three lesions exhibited as wedge-shaped non-enhancive area; small column of enhanced signal was observed in the surrounding area ofthe other two lesion. With DSA, most part of the tumor showed no staining because of bloodlessness, and formed a clear contrast to the strongly stained renal tissue. ?Uric acid, urea and creatinine increase slightly 1-3 days after RF and returned to normal 7 days later in the treated group while the three indexes increased dramatically and continuously in the control group.Conclusions: Percutaneous radiofrequency ablation guided by ultrasonography in a renal tumor is safe and feasible. RF can generate certain size of ablation lesion and result in coagulative necrosis in tumor. In rabbit model, RF can prolong survival of tumor-loading animal, inhibit tumor growth, reduce or postpone metastasis. The incomplete ablation of tumor is due to several factors, including the biological character of the tumor, the visibility of the tumor with ultrasonography, the cooperation and the experience of the operator. The complication indues unexpected burn of the surrounding organs, hematuria, implantation in needle track. RF can cause transient reversible damage of kidney function, which can be recovered in short time. Increase in urea and creatinine indicates recurrence of tumor, which leads to the damage of kidney fuction. The level of urea and creatinine can be used as a index for the evaluation of therapeutic efficiency of RF.Objective: A new technique, percutaneous radiofrequency ablation(RF), has been applied in the treatment of renal tumor. Howerer the manner of guidance and the reliability of therapeutic efficiency evaluation remain controversial. The aim of this study was to investigate ultrasonograpyic characters and the dynamic changing of blood flood in renal tumor before and after RF, so as to evaluate the application of ultrasonography in RF treatment of renal tumor. A microbubble contrast agent, Levovist, was applied to perform contrast-enhanced ultrasonography, and the valves of contrast reagent in evaluating the therapeutic efficiency of RF were studied. The factors that affect the success of manipulation were also discussed.Methods: Renal VX2 tumor models were set up by injecting tumor tissue suspension into the rabbits' renal percutaneously with ultrasound-guidence. Ultrasonographic examinations were performed timely after injection using an Acuson Sequoia 512 unit with a 15L8W high-frequency transducer. Two-dimensioned ultrasonography was performed to monitor the size, location, modality, growth and echo of the tumors. Color and power Doppler ultrasonography were performed to monitor the blood flow distribution in the tissue intra-tumor and surrounding area. The blood flow indexwas recorded. After affirming the formation of tumor node, RF was performed. With the help of ultrasonography, the pathway was selected before puncture and then electrode was punctured into a proper position with its tip on the wedge of tumor in the deep side. Then RF was performed with the monitoring of ultrasonography throughout of the course of ablation Ultrasonography examination was performed at the 3rd, 7th, 14*21 * day after RF. The index examined was as the same as that of pre-operation. The images were analyzed using a Tomtec work platform. One rabbit was selected and sacrificed at each time point. The tumor-loading kidney was resected. The specimen was then fixed, imbedded in paraffin, sliced and stained with HE. The pathological character was observed under light microscopy and compared with the findings of two-dimensioned ultrasonography. To investigate the value of contrast enhanced ultrasonography in RF treatment of renal tumor, Levovist (300-400mg/ml) was injected into the vein of the tomor-loading rabbits, and ultrasonography examination was performed 1day before operation, 1day after operation and 1week after operation respectively. The enhanced images and the characters of blood supplying of the tumor and of the ablation focus, together with the continuance time of injection and of enhanced effect, were recorded. Results.- (D Dynamic observation of the renal tumor in rabbits with ultrasonography: Most tumor depicted hypo-echo. The inteRFce between tumor and normal renal parenchyma was not clear. During the time or ablation, radial line interfering artifact appeared ontwo-dimensioned ultrasonography; flake-like hyper-echo with shadow existed intra tumor. Immediately after ablation, there was some unevenly distributed hyper-echo, which disappeared 1day later. Three days later, the ablation lesion presented as hyper-echo with clear margin, and the surrounding hypo-echo ring became faint. Two weeks later, the ablation lesion presented as uneven mixture of hyper-echo spots and hypo-echo spots; the surrounding hypo-echo ring disappeared in part of cases; irregular hypo-echo focus appeared in the surrounding area of ablation lesion which presented as hyper-echo or in nearby renal parenchyma. The ultrasonographic character of the hypo-echo focus was similar to that of the tumor pre-ablationg, which was confirmed to be recurrence or residue of tumor by pathological examination. During the course of treatment, no blood flow signal was detected intra tumor or in the surrounding area with color Doppler ultrasonography. At different time poin after treatment, spot-like blood flow signal was detected in the hypo-echo area surrounding the ablation lesion, which was confirmed to be recurrence or residue of tumor by DSA. No blood flow signal was observed in the hyper-echo ablation lesion area. ?The inner diameter of artery of the tumor-loading kidney increased in the treated group: The peak blood flow velocity of renal artery decreased markedly during the course of treatment, and increased 3-7 days later; The resistance index (Rl) of renal artery increased markedly during the course of treatment, and returned to normal 7 days later. Compared to the control, no change was noticed in the Rl of renalartery at other time point. (D The success rate of puncture under the guidance of ultrasonography was 100%. The tumor was ablated completely in 19 cases in which the electrode was put into proper position, not completely in 12 cases. The residue of tumor was confirmed by pathological examination latterly. Complications included unexpected burn of surrounding organs which happened in 4 rabbits and needle track implantation which occurred in 3 rabbits. ? Contrast-enhanced ultrasonography was performed in 6 rabbits of the treated group. The average continuance time of injection was (125±46)s. Enhancing effect existed (8-30)s after the beginning of injection, peaked very quickly and continued for (5-10)minutes. No enhancing effect was observed in 2 ablation lesion through out the time after treatment. Enhanceed Short bar-like and dendritic blood flow I and power signal was noticed in 4 cases 1day and 1week after RF, which suggested residue of tumor. One of the residue of tumor was confirmed by DSA and the other 3 was confirmed by ultrasonography during follow up.Conclusions: Characteristic presentation can be observed with ultrasonography during the course of guidance and treatment in RF management of rabbit renal VX2 tumor. Early find residue or recurrence of tumor can be achieved through the analyse of echo and blood flow with two-dimensioned and color Doppler ultrasonography, which is valuable to the evaluation of RF therapeutic efficiency. Precise pre-operative localization and intra-operative guidance of ultrasonography, proper selection of case for RF treatment and expert...
|
PDF Full Text Request