Does Artificial Ascites Induce the Heat-Sink Phenomenon during Percutaneous Radiofrequency Ablation of the Hepatic Subcapsular Area?: an in vivo Experimental Study Using a Rabbit Model

OBJECTIVE: To evaluate the effect of the heat-sink phenomenon induced by artificial ascites on the size of the ablation zone during percutaneous radiofrequency (RF) ablation of the hepatic subcapsular area in an in vivo rabbit model. MATERIALS AND METHODS: A total of 21 percutaneous rabbit liver RF ablations were performed with and without artificial ascites (5% dextrose aqueous solution). The rabbits were divided into three groups: a) control group (C, n = 7); b) room temperature ascites group (R, n = 7); and c) warmed ascites group (W, n = 7). The tip of a 1 cm, internally cooled electrode was placed on the subcapsular region of the hepatic dome via ultrasound guidance, and ablation was continued for 6 min. Changes in temperature of the ascites were monitored during the ablation. The size of the ablation zones of the excised livers and immediate complications rates were compared statistically between the groups (Mann-Whitney U test, Kruskal-Wallis test, linear-by-linear association, p = 0.05). RESULTS: One rabbit from the "W" group expired during the procedure. In all groups, the ascites temperatures approached their respective body temperatures as the ablations continued; however, a significant difference in ascites temperature was found between groups "W" and "R" throughout the procedures (39.2 +/- 0.4 degrees C in group W and 33.4 +/- 4.3 degrees C in group R at 6 min, p = 0.003). No significant difference was found between the size of the ablation zones (782.4 +/- 237.3 mL in group C, 1,172.0 +/- 468.9 mL in group R, and 1,030.6 +/- 665.1 mL in group W, p = 0.170) for the excised liver specimens. Diaphragmatic injury was identified in three of seven cases (42.9%) upon visual inspection of group "C" rabbits (p = 0.030). CONCLUSION: Artificial ascites are not likely to cause a significant heat-sink phenomenon in the percutaneous RF ablation of the hepatic subcapsular region.

FDG-PET for Evaluating the Antitumor Effect of Intraarterial 3-Bromopyruvate Administration in a Rabbit VX2 Liver Tumor Model

OBJECTIVE: We wanted to investigate the feasibility of using FDG-PET for evaluating the antitumor effect of intraarterial administration of a hexokinase II inhibitor, 3-bromopyruvate (3-BrPA), in a rabbit VX2 liver tumor model. MATERIALS AND METHODS: VX2 carcinoma was grown in the livers of ten rabbits. Two weeks later, liver CT was performed to confirm appropriate tumor growth for the experiment. After tumor volume-matched grouping of the rabbits, transcatheter intraarterial administration of 3-BrPA was performed (1 mM and 5 mM in five animals each, respectively). FDG-PET scan was performed the day before, immediately after and a week after 3-BrPA administration. FDG uptake was semiquantified by measuring the standardized uptake value (SUV). A week after treatment, the experimental animals were sacrificed and the necrosis rates of the tumors were calculated based on the histopathology. RESULTS: The SUV of the VX2 tumors before treatment (3.87+/-1.51[mean+/-SD]) was significantly higher than that of nontumorous liver parenchyma (1.72+/-0.34) (p < 0.0001, Mann-Whitney U test). The SUV was significantly decreased immediately after 3-BrPA administration (2.05+/-1.21) (p = 0.002, Wilcoxon signed rank test). On the one-week follow up PET scan, the FDG uptake remained significantly lower (SUV 1.41+/-0.73) than that before treatment (p = 0.002), although three out of ten animals showed a slightly increasing tendency for the FDG uptake. The tumor necrosis rate ranged from 50.00% to 99.90% (85.48%+/-15.87). There was no significant correlation between the SUV or the SUV decrease rate and the tumor necrosis rate in that range. CONCLUSION: Even though FDG-PET cannot exactly reflect the tumor necrosis rate, FDG-PET is a useful modality for the early assessment of the antitumor effect of intraarterial administration of 3-BrPA in VX2 liver tumor.

Ferucarbotran-Enhanced MR Imaging of the Radiofrequency Ablation Zones in the Normal Rabbit Liver: Comparison with the Conventional MR Imaging

PURPOSE: We wanted to evaluate the findings of ferucarbotran-enhanced MR imaging of the radiofrequency (RF) ablation zones in normal rabbit livers and we compared the findings with the conventional MR imaging. MATERIALS AND METHODS: RF ablation zones were created in the livers of 12 rabbits in vivo by using a 17-gauge internally cooled electrode with 1-cm active tip, and RF energy (maximum power: 30 Watt) was applied for three minutes. Three rabbits were sacrificed immediately and then at three days, two weeks and six weeks after RF ablation. Before sacrifice, the T1- and T2-weighted images (WI) and the ferucarbotran-enhanced T2*WIs were obtained and compared regarding the signal intensity of ablation zone, the laminar pattern of the signal intensity and the contrast-to-noise ratio (CNR) of the ablation zone to the liver parenchyma. RESULTS: On T1- and T2WIs, the RF ablation zones showed two to four laminar patterns of signal intensity according to the time. Meanwhile, on the ferucarbotran-enhanced T2WIs, the RF ablation zones showed high signal intensity without a laminar pattern regardless of time. The CNRs of the ablation zones to the liver parenchyma on the ferucarbotran-enhanced T2*WIs (18.2+/-5.9) were significantly higher than those of the TIWIs (1.6+/-1.5) and T2WIs (2.7+/-1.9) (p < 0.05). CONCLUSION: On the ferucarbotran-enhanced T2*WI, the RF ablation zones showed high signal intensity without a distinct laminar pattern and significantly higher lesion conspicuity than did the conventional T1- and T2WIs. Therefore, the ferucarbotran-enhanced T2*WI shows the RF ablation zone more accurately and clearly than do the conventional T1- and T2WIs.

Radiofrequency Ablation of Liver Cancer: Early Evaluation of Therapeutic Response with Contrast-Enhanced Ultrasonography

The early assessment of the therapeutic response after percutaneous radiofrequency (RF) ablation is important, in order to correctly decide whether further treatment is necessary. The residual unablated tumor is usually depicted on contrast-enhanced multiphase helical computed tomography (CT) as a focal enhancing structure during the arterial and portal venous phases. Contrast-enhanced color Doppler and power Doppler ultrasonography (US) have also been used to detect residual tumors. Contrast-enhanced gray-scale US, using a harmonic technology which has recently been introduced, allows for the detection of residual tumors after ablation, without any of the blooming or motion artifacts usually seen on contrast-enhanced color or power Doppler US. Based on our experience and reports in the literature, we consider that contrast-enhanced gray-scale harmonic US constitutes a reliable alternative to contrast-enhanced multiphase CT for the early evaluation of the therapeutic response to RF ablation for liver cancer. This technique was also useful in targeting any residual unablated tumors encountered during additional ablation.

Radiofrequency Ablation of Rabbit Liver In Vivo: Effect of the Pringle Maneuver on Pathologic Changes in Liver Surrounding the Ablation Zone

OBJECTIVE: We wished to evaluate the effect of the Pringle maneuver (occlusion of both the hepatic artery and portal vein) on the pathologic changes in the hepatic vessels, bile ducts and liver parenchyma surrounding the ablation zone in rabbit livers. MATERIALS AND METHODS: Radiofrequency (RF) ablation zones were created in the livers of 24 rabbits in vivo by using a 50-W, 480-kHz monopolar RF generator and a 15-gauge expandable electrode with four sharp prongs for 7 mins. The tips of the electrodes were placed in the liver parenchyma near the porta hepatis with the distal 1 cm of their prongs deployed. Radiofrequency ablation was performed in the groups with (n=12 rabbits) and without (n=12 rabbits) the Pringle maneuver. Three animals of each group were sacrificed immediately, three days (the acute phase), seven days (the early subacute phase) and two weeks (the late subacute phase) after RF ablation. The ablation zones were excised and serial pathologic changes in the hepatic vessels, bile ducts and liver parenchyma surrounding the ablation zone were evaluated. RESULTS: With the Pringle maneuver, portal vein thrombosis was found in three cases (in the immediate [n=2] and acute phase [n=1]), bile duct dilatation adjacent to the ablation zone was found in one case (in the late subacute phase [n=1]), infarction adjacent to the ablation zone was found in three cases (in the early subacute [n=2] and late subacute [n=1] phases). None of the above changes was found in the livers ablated without the Pringle maneuver. On the microscopic findings, centrilobular congestion, sinusoidal congestion, sinusoidal platelet and neutrophilic adhesion, and hepatocyte vacuolar and ballooning changes in liver ablated with Pringle maneuver showed more significant changes than in those livers ablated without the Pringle maneuver (p < 0.05) CONCLUSION: Radiofrequency ablation with the Pringle maneuver created more severe pathologic changes in the portal vein, bile ducts and liver parenchyma surrounding the ablation zone compared with RF ablation without the Pringle maneuver. Therefore, we suggest that RF ablation with the Pringle maneuver should be performed with great caution in order to avoid unwanted thermal injury.

Overlapping Ablation Using a Coaxial Radiofrequency Electrode and Multiple Cannulae System: Experimental Study in ex-Vivo Bovine Liver

OBJECTIVE: To assess the sizes and configurations of thermal zones after overlapping ablations using a coaxial radiofrequency (RF) electrode and multiple cannulae in ex-vivo bovine liver. MATERIALS AND METHODS: For ablation procedures, a coaxial RF electrode and introducer set was used. Employing real-time ultrasound guidance and overlapping techniques in explanted, fresh bovine liver, we created five kinds of thermal zones with one (n=10), two (n=8), four (n=3), and six ablation spheres (n=3). Following ablation, MR images were obtained and the dimensions of all thermal zones were measured on the longitudinal or transverse section of specimens. The shape of the composite ablation zones was evaluated using three-dimensional MR image reconstruction. RESULTS: At gross pathologic examination of ten single-ablation zones (spheres), the long-axis (transverse) and short-axis lengths of zones ranged from 3.7 to 4.4 (mean, 4.1) cm and from 3.5 to 4.0 (mean, 3.7) cm, respectively. The long-axis (transverse) and short-axis lengths of double-ablation zones (cylinders) with 23% overlap ranged from 7.0 to 7.7 (mean, 7.3) cm and from 3.0 to 3.9 (mean, 3.5) cm, respectively; those with 58% overlap ranged from 6.0 to 6.4 (mean, 6.2) cm and from 3.8 to 4.6 (mean, 4.3) cm, respectively. The long-axis (diagonal) and short-axis lengths on a transverse section of four-ablation zones (cakes) ranged from 8.5 to 9.7 (mean, 9.1) cm and from 3.0 to 4.1 (mean, 3.7) cm, respectively. Gross pathologic examination of three composite six-ablation zones (spheres) showed that the long-axis (diagonal) and short-axis lengths of zones ranged from 9.0 to 9.9 (mean, 9.4) cm and from 6.8 to 7.5 (mean, 7.2) cm, respectively. T2-weighted MR images depicted low-signal thermal zones containing multiple curvilinear and spotty regions of hyperintensity. CONCLUSION: Using a coaxial RF electrode and multiple cannulae, together with ultrasound guidance and precise overlapping ablation techniques, we successfully created predictable thermal zones in ex-vivo bovine liver.

Shrinkage Rate of Necrotic Lesion after Radiofrequency (RF) Ablation of Hepatocellular Carcinoma: Correlation with Marginal Recurrence and Influencing Factors

PURPOSE: To compare the CT findings of hepatocellular carcinomas (HCCs) immediately after radiofrequency (RF) ablation with those obtained at six months' follow-up, to analyse the relationship between degree of shrinkage of a necrotic lesion and marginal recurrence, and to evaluate the factors influencing shrinkage. MATERIALS AND METHODS: We retrospectively evaluated 54 patients with 62 HCCs who underwent only RF ablation between May 1999 and July 2000. For six months after ablation, all had been free from marginal recurrence ad new-growth tumors. The findings of six-month follow-up CT were compared with those obtained immediately after RF ablation, and the volume of each necrotic lesion was calculated and compared. In terms of degree of shrinkage, tumors were classified as belonging to either group I (below 50%), group II (50-80%) or group III (above 80%). Each tumor was analysed in terms of its Child-Pugh classification, vascularity at CT, size, treatment details, the post-ablation appearance of its margins, and the presence, during necrosis, of peritumoral vessles and air bubbles. For statistical evaluation, Fisher's exact test was used. Shrinkage after ablationwas correlated to marginal recurrence during a period of more than one year. RESULTS: The Follow-up CT at six months showed that since immediately after ablation, necrotic lesions had shrunk by an average of 72%. Peritumoral vessels were seen in 12 of 14 cases in group I (86%), three of 13 in cases of group II (23%), and 11 of 35 in group III (31%)(p=0.001). Immediate CT revealed the presence of air bubbles in two cases in group I (14%), five in group II (38%), and 24 in group III (69%)(p<0.05). At follow-up CT performed during a period of more than one year, marginal recurrence was noted in four cases in group I, two in group II and two in group III (p<0.05). CONCLUSION: When a necrotic lesion contains no peritumoral vessels but does contain air bubbles, the degree of post-RFablation shrinkage increases. The greater the shrinkage, the less the marginal recurrence rate.

Gene Delivery to the Rat Liver Using Cationic Lipid Emulsion/DNA Complex: Comparison between Intra-arterial, Intraportal and Intravenous Administration

OBJECTIVE: To compare the efficiency of intra-arterial, intraportal, and intravenous administration of cationic lipid emulsion/DNA complex, as used for gene transfer to rat liver. MATERIALS AND METHODS: DNA-carrier complex for the in-vivo experiment was prepared by mixing DNA and a cationic lipid emulsion. According to the administration route used (intra-arterial, intraportal, or intravenous), the animals were assigned to one of three groups. The heart, lung, liver, spleen and kidneys were removed and assayed for total protein and luciferase concentration. RESULTS: The cationic lipid emulsion/DNA complex used successfully transfected the various organs via the different administration routes employed. Luciferase activity in each organ of untreated animals was negligible. Liver luciferase values were significantly higher in the groups in which intra-arterial or intraportal administration was used. CONCLUSION: The intra-arterial or intraportal administration of cationic lipid emulsion/DNA complex is superior to intravenous administration and allows selective gene transfer to the liver.

Hepatocellular Carcinoma after Radiofrequency Ablation: Recurrent Pattern and Influenting Factor

PURPOSE: To evaluate patterns of recurrence and factors which influence them in radiofreqency (RF) ablation for the treatment of hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Between May 1999 and March 2000, 69 patients with 82 HCCs underwent RF ablation for complete necrosis. They were diagnosed by tissue biopsy or tumor marker, and the results of triphasic spiral CT. The indications were that nodular lesions were clearly visualized at sonography, less than 5 cm in size and less than four in number, and that patients had no history of previous treatment. Local therapeutic efficacy such as complete necrosis and marginal recurrence, and new lesions were evaluated by means of triphasic spiral CT performed at least six months after the completion of ablation. We then analyzed the correlation between local therapeutic efficacy and various influential factors such as tumor size, whether the tumor was attached to the portal vein, gross morphology, Child-Pugh classification, and alpha- fetoprotein level before the procedure, as well as the correlation between new lesions and influential factors which included the alpha-fetoprotein level before the procedure, Child-Pugh classification, and multiplicity per person. RESULTS: During a mean follow-up period of 8.95 (range, 6-14) months after RF ablation, the rate of complete necrosis and of marginal recurrence was 91% and 12%, respectively. When a tumor was larger and was attached to a large branch of the portal vien, the incidence of incomplete necrosis and marginal recurrence was greater. The occurrence rate of new lesion was 19.4%. When the alpha-fetoprotien level before the procedure was higher and a tumor was multiple in number, new lesions occurred more frequently. CONCLUSION: Sufficient knowledge of patterns of recurrence and the factors which influence them might improve the therapeutic effects of RF ablation in patients with HCC.

MR Imaging-Histopathologic Correlation of Radiofrequency Thermal Ablation Lesion in a Rabbit Liver Model: Observation during Acute and Chronic Stages

OBJECTIVE: To determine the ability of MR imaging to detect the pathological changes occurring in radiofrequency (RF) thermal lesions and to assess its accuracy in revealing the extent of tissue necrosis. MATERIALS AND METHODS: Using an RF electrode, thermal lesions were created in the livers of 18 rabbits. The procedure involved three phases. In the acute phase, six animals were killed the day after performing thermal ablation with RF energy, and two on day 3. In the subacute and chronic phases, eight rabbits underwent percutaneous hepatic RF ablation. After performing MR imaging, two animals were sacrificed at 1, 2, 4, and 7 weeks after the procedure, and MR-pathologic correlation was performed. RESULTS: In the acute phase, the thermal ablation lesions appeared at gross examination as well-circumscribed, necrotic areas, representing early change in the coagulative necrosis seen at microscopic examination. They were hypointense on T2-weighted images, and hyperintense on T1-weighted images. Gadolinium-enhanced MR imaging showed that a thin hyperemic rim surrounded the central coagulative necrosis. In the subacute phase, ablated lesions also showed extensive coagulative necrosis and marked inflammation at microscopic examination. Beyond two weeks, the lesions showed gradual resorption of the necrotic area, with a peripheral fibrovascular rim. The size of lesions measured by MR imaging correlated well with the findings at gross pathologic examination. CONCLUSION: MR imaging effectively demonstrates the histopathological tissue change occurring after thermal ablation, and accurately determines the extent of the target area.

Hepatic Parenchymal Changes After Percutaneous Injection of Holmium-166 in Rabbit

PURPOSE: To evaluate changes in rabbit liver parenchyma on MR images following percutaneous Holmium-166 injection, and to correlate those changes with histologic findings. MATERIALS AND METHODS: Holmium-166 (10-25 mCi) was percutaneously injected into the liver of rabbit (n=12) under sonographic guidance. MR images were obtained between one to two weeks (acute phase) after the injection in four rabbits, and between two to four weeks (subacute phase) after the injection in four rabbits. Tissue specimens of these eight rabbits were obtained immediately after MR imaging. Tissue specimens were obtained without MR imaging in four rabbits (between one to two weeks in one rabbit and between three to four weeks in three rabbits). RESULTS: Tissue specimens showed central liquefactive necrosis and peripheral coagulative necrosis containing deposition of small particles and hemorrhage. The peripheral margin of the lesions showed formation of the granulation tissue with fibrosis, which tended to be more prominent in subacute phase. The area of the necrosis tended to correlate with the dose of the radioactive Holmium-166. On MR images, the central portion of the necrosis showed hyperintensity on T2-weighted image, hypointensity on the precontrast T1-weighted images, and no enhancement on the dynamic MR images. The peripheral portion of the necrosis showed hypointensity on T2-weighted images, iso or mild hypointensity on the T1-weighted images, and mild peripheral enhancement on the delayed dynamic MR images. The peripheral margin of the lesion showed hypointensity on both T1- and T1-weighted images with increased enhancement on the delayed phase images of the dynamic MR images. CONCLUSION: After percutaneous Holmium-166 injection into rabbit liver parenchyma, the central portion showed liquefactive necrosis, the peripheral portion showed coagulative necrosis with granulation, fibrosis, hemorrhage and depostition of small granules. MR imaging may be helpful in evaluation of the histological change of the liver after percutaneous Holmium-166 treatment.

Radiofrequency Tissue Ablation with Cooled-Tip Electrodes:An Experimental Study in a Bovine Liver Model on Variables Influencing Lesion Size

PURPOSE: The purpose of this study was to determine the influence of various factors on the extent of thermal coagulation necrosis after radiofrequency (RF) tissue ablation using a cooled-tip electrode in bovine liver. MATERIALS AND METHODS: RF ablation was induced by a monopolar 500 KHz-RF generator (CC-1; Radionics,Burlington, Mass., U.S.A.) and an 18-G cooled-tip with single or clustered electrodes. The ablation protocol involveda combination of varying current, ablation time, power output, gradual or abrupt increase of this out-put, and pulsed radiofrequency techniques. The maximum diameter of all thermal lesions which showed a color change was measured perpendicular to the electrode axis by two observers who reached their decisions by consensus. Twenty representative lesions were pathologically examined. RESULTS: With increasing current lesion diameter also increased, but above 1500 mA no further increase was induced. Extending the ablation time to 9 minutes for a single electrode and 15 minutes for a clustered electrode increased lesion diameter until a steady state was reached. Higher power levels caused larger lesions, but above 100 W no increase was observed. Ample exposure time coupled with a stepwise increase in power level induced a lesion larger than that resulting from an abrupt increase. Continuous pulsed RF with a high current led to increased coagulation necrosis diameter. CONCLUSION: These experimental findings may be useful thermotherapy. The data suggest that all involved factors significantly affect lesion size: if the factors are better understood, cancer thermotherapy can be better controlled.

Pulsed Wave and Color Doppler US Findings of Transjugular Intrahepatic Portosystemic Shunts (TIPS)

The transjugular intrahepatic portosystemic shunt (TIPS) is an effective and relatively safe and widely accepted treatment for complications arising from portal hypertension. Shunt or hepatic vein stenosis and shunt occlusion are common short- and medium-term complications arising from the procedure, though if detected early, these conditions may be treated before the recurrence of gastrointestinal bleeding or ascites. Doppler US is a relatively inexpensive, accurate, and noninvasive method for the evaluation of shunt status.

Radiofrequency Ablation of Small Hepatocellular Carcinoma: Early Experience of Efficacy and Safety

PURPOSE: To evaluate the efficacy and safety of radiofrequency (RF) ablation for the treatment of small hepato-cellular carcinoma (HCC). MATERIALS AND METHODS: Forty-four patients with 51 HCCs underwent ultrasound guided RF ablation using ex-pandable needle electrodes and a monopolar RF generator. The patients were not considered suitable candidates for surgery or declined this option, and had no history of previous treatment. Mean tumor diameter was 2.5 cm (range, 1.0 -4.0 cm). Therapeutic efficacy was evaluated by means of three-phase helical computed tomography (CT) performed at least one month after the completion of ablation. The recurrence rate was also evaluated by follow-up CT at least four months after treatment. RESULTS: Using RF ablation, complete necrosis was achieved in 48 of 51 tumors (94%). Among 20 patients in whom follow-up CT was performed at least four months after ablation, one (5%) showed marginal recurrence and in another (5%) there was recurrence in remote liver parenchyma. We experienced neither procedure-re-lated mortality nor major complications which required specific treatment. Three minor complications (one small pneumothorax and two cases of intraperitoneal bleeding) occurred, but these disappeared without specific treatment. CONCLUSION: RF ablation using an expandable needle electrode showed a high rate of complete necrosis and a low rate of complications. The technique is therefore considered effective and safe for the local control of small HCCs.

An Experimental Study on the Effect of Mixture of Absolute Ethanol and Lipiodol Injected into Normal Liver ofRabbit: CT Features and Histopathologic Changes

PURPOSE: To investigate the safety and usefulness of Lipiodol-percutaneous transhepatic ethanolinjection(L-PEI) and to determine the appropriate concentration of Lipiodol during L-PEI. This was achieved byevalvating CT findings and histopathologic changes according to the concentration of Lipiodol, amount of ethanol,and the time interval after injection into normal rabbit liver. MATERIALS AND METHODS: This experimental studyinvolved 18 New Zealand rabbits under US guidance. They were divided into five groups according to injectedmaterials; two rabbits with 0.4cc of normal saline(group I), six with 0.4cc of ethanol in the left hepaticlobe(group II), and 0.4cc of Lipiodol in the right hepatic lobe(group III), five rabbits with 5%Lipiodol-ethanol(5% vol. of Lipiodol+95% vol. of ethanol), 0.2cc in the right hepatic lobe, and 0.4cc in theleft(group IV); and five rabbits with 10% Lipiodol-ethanol as per group IV(group V). CT was performed immediately,one week, two weeks, and three-four weeks after injection, and pathologic specimens were obtained on the thirdday(acute phase) and during the third or fourth week(chronic phase) after injection. RESULTS: On CT, intrahepaticlocalization of the L-PEI injection site was well demonstrated as a focal high attenuated area which graduallydecreased in attenuation on follow up CT. The opacification of the inferior vena cava by Lipiodol, the lineardistribution of Lipiodol along portal veins or fissures, and peritoneal leakage were clearly demonstrated ingroups III-V, though the effects gradually disappeared during follow-up CT. There was no remarkable difference ingross CT attenuation between group IV and group V. The main pathologic findings during the acute phase of group IIwere coagulation necrosis surrounded by macrophage, inflammatory reaction, and early periportal and subcapsularfibrosis. The findings in group IV and V were similar to those in group II and additional fat vacuoleaccumulations in the necrotic area were also seen. During the chronic phase of group II, areas of necrosis wereabsent or smaller and were surrounded or replaced by more organized fibrosis, macrophage or multinucleated giantcell infiltration. Periportal, subcapsular fibrosis was also found. In group IV and V, the findings were similarto those of group II, though additional fat vacuoles in fibrotic or necrotic areas, foreign body reaction to fatvacuole, regenerating nodule and calcification were also observed. CONCLUSION: L-PEI is more useful for thedetection by CT of an injection site than PEI alone, and with regard to CT and histopathologic findings, there wasno significant difference between the 5% and 10% Lipiodol-ethanol groups. Compared to PEI, L-PEI provoked nosighificant additional hepatic injury; only fatty change and foreign body reaction were noted. Thus, L-PEI is moreuseful than PEI for the management of HCC.

Interstitial Laser Photocoagulation with Diode Laser Unit in Bovine Liver

PURPOSE: To evaluate the extent of tissue coagulation during interstitial laser photocoagulation (ILP) innormal bovine liver, using a diode laser unit and various parameters, and to determine whether the procedure isapplicable to clinical practice.. MATERIALS AND METHODS: Using an 18-gauge needle, experimental interstitiallaser photocoagulation (ILP) was carried out in normal bovine liver. On the basis of differing parameters, threegroups were established. For group I, a single photofiber with laser power of 1, 3 and 5 watts and an exposuretime of 60, 180, 300, 420 or 600 seconds was used. For groups II and III, four needles were fixed at a distance of1cm and 1.5cm ; in each case a needle fixation device was used, as well as a laser distributor for simultaneouslaser exposure of photofibers. As a control, four photofibers were placed as for groupIII, but to compare groups IIand III, each photofiber was exposed to a laser of 3 watts 300 seconds, without using a laser distributor. Toevaluate the range of tissue coagulation, specimens were analyzed both with regard to cross-sectional grossfindings and histopathologically . RESULTS: The largest diameter of thermal coagulation necrosis in Group I was15x15mm, and this was ball-shaped. Coalescence of coagulation between each photofiber was observed in Group II,and this was up to 25 mm in diameter. In Group III and controls, coalescence was not found, though the extent oftissue coagulation increased with increasing wattage and exposure time. The extent of charring at the center ofcoagulation also increased with increasing wattage. Smoke bubbles emanating from the coagulation area wereobserved, and during ILP involving a single photofiber, increased from 3 watts, applied for 300 seconds.CONCLUSION: Using an 8-gauge needle and a diode laser ILP, we have shown that a range of tissue coagulationacutely ablates normal bovine liver. In selective cases, the procedure could be applied to clinical trials.

Transjugular Intrahepatic Portosystemic Shunt with PTFE-Covered Spiral Z-stent: An Experimental Study in Swine

PURPOSE: To improve TIPS patency by inserting polytetrafluoroethylene(PTFE)-covered spiralZ-stents in swine. MATERIALS AND METHODS: Using PTFE covered spiral Z-stents lined with TIPS tract from theportal vein wall to the inferior vena caval orifice of the right hepatic ve i n , TIPS were created in seven youngswine. The animals were followed up by portal ve n o g r a p hy and venous pressure was measured at two - weekintervals for 12 weeks or until shunt occlusion. After sacrifice, resected liver was examined grossly andpre-pared for histology. RESULTS: The fifty percent patency rate using lifetime analysis was 83 % at 4 weeks, 33%at 6 weeks, 17 % at 8 weeks and 0% at 10 weeks. Venography demonstrated that the predominant sites of stenosiswere the portal vein wall(2/6), the TIPS tract(2/6) and the IVC orifice of the right hepatic vein(2/6). One swinedied 11 days after TIPS due to illness, and bile leaks were discovered in two of the seven animals. Histologicstudy demonstrated intimal hyperplasia in either the portal vein wall or the end of the stent at which the IVCorifice was located, as well as thrombus and pseudointimal hyper-plasia in the TIPS tract. CONCLUSION: P T F E -c overed spiral Z-stents were easily placed and significantly im-proved TIPS patency.

The Effect of Blood Injection for the Prevention of Ethanol Reflux after Intrahepatic Ethanol Injection in the Rat

PURPOSE: To reduce ethanol reflux from the needle channel by injecting rat blood immediately after theinjection of ethanol into rat liver. MATERIALS AND METHODS: The first experiment involved 33 rat livers whichwere divided into four groups (three livers in group 1 ; ten in groups 2, 3, and 4). Group 1 animals were used ascontrols, and 0.1ml saline was injected into the liver ; in group 2, ethanol-Tc-99m-O4- mixed solution (0.1 ml,0.2 mCi) was injected into the liver ; in groups 3 and 4, the needle channel was blocked with 0.02 ml of freshblood and old blood, respectively, after the injection of ethanol. After removing the needle, a 3cm round filterpaper was laid on each injection site to absorb refluxed ethanol-Tc-99m-O4- mixed solution from the liver, andeach paper was then counted by a gamma camera unit. In the second experiment, 33 rats were divided into fourgroups (three rats in group 1 ; ten in groups 2, 3, and 4). Group 1 animals were used as controls, and afterexposing the left lateral lobe of the liver, 0.05 ml of saline was injected; in group 2, 0.05 ml of ethanol wasinjected into the liver in groups 3 and 4 the needle channel was blocked with 0.02 ml of fresh blood and oldblood, respectively, after the injection of ethanol. After ten days, peritoneal adhesions were scoredmacroscopically and microscopically. RESULTS: In the first experiment using ethanol-Tc-99m-O4- mixed solution,groups blocked with blood after the injection of mixed solution showed lower gamma counts than the group injectedwith mixed solution only (p-value = 0.0002). The group blocked with old blood showed the lowest count.Macroscopical and microscopical examination of peritoneal adhesions indicated that the grade of adhesion was lowerin groups blocked with blood than in the group injected with ethanol only (p-value = 0.0261 and 0.0163,respectively). CONCLUSION: The above results suggest that an injection of blood after an injection of ethanol isa very effective way of preventing reflux from the liver.

Saline-enhanced Radiofrequency Electrocoagulation in Bovine Liver

PURPOSE: To determine the effectiveness of saline-enhanced radiofrequency electrocoagulation in bovine liver tissue MATERIALS AND METHODS: Saline-enhanced radiofrequency electrocoagulation (group I), hot saline injection induced by radiofrequency electrocoagulation (group II), and radiofrequency electrocoagulation (group III) were performed in ex vivo bovine liver. Radiofrequency power was 100 and 200 watts, and current was applied for 10, 20, and 30 seconds. Tissue was histopathologically examined for thermal injury. RESULTS: The largest diameter of thermal injury was about 41.0 mm in group I, 12.3 mm in group II and 9.3 mm in group III. The mean diameter of the injury increased with higher wattage in group I and II and with longer procedure time in group I (p<0.05). At corresponding wattage and times, group I showed a larger diameter of thermal injury and more increase in than group II or III(p<0.05). The degree of carbonization was more severe in group III than in groups I and II. Grossly, thermal injury showed a well-defined, relatively spherical configuration without extension along parenchymal interstitium. CONCLUSION: In an animal model, saline-enhanced radiofrequency electrocoagulation may effectively induce thermal injury, and may thus be another effective tool for use in the treatment of hepatic tumors. Further clinical experience is needed.

Usfulness of Transjugular Liver Biopsy

PURPOSE: To evaluate the usefulness of transjugular liver biopsy (TJLB), and possible complications. MATERIALS AND METHODS: During a three-year period, TJLB was performed in 21 patients. Through the right internal jugular vein, a 9F sheath was introduced into the right hepatic vein, and using Mansfield forceps, biopsy was then performed. RESULTS: Reasons for TJLB included massive ascites in six patients, coagulopathy in nine, thrombocytopenia in five, and other causes in one. In 20 cases, we obtained liver tissue, and pathologic diagnosis was possible in 17 ; in three cases, the amount of biopsy tissue obtained was insufficient for pathologic diagnosis. In one patient with Budd-Chiari syndrome, we were unable to catheterize the right hepatic vein and failed to obtain liver tissue. Complications occurred in five patients, as follows: hematoma formation at the puncture site in one patient, and pain at the puncture site, lasting 24 hours, in four. CONCLUSION: TJLB may be a safe and useful method in patients in whom percutaneous liver biopsy is contraindicated.