Cooled-shaft Antenna Research Articles

Microwave ablation for the treatment of arterial epistaxis: "how I do it".

Arterial epistaxis is commonly seen in the rhinology clinic and can have a significant impact on quality of life. Previous studies have explored various therapies to address epistaxis. Patients were treated in the outpatient clinic or operating room by microwave ablation (MWA) with a 2450-MHz cooled-shaft antenna to treat an epistaxis bleeding point. Of the 481 patients with arterial epistaxis, bleeding was controlled within 1 to 2 minutes and only 2 patients with recurrent bleeding required re-ablation. The shape of the thermal lesion was elliptical and it was approximately 2 mm in length, 1 mm in width, and 0.5 to 1 mm in penetration depth. Of the 481 patients, 167 (34.7%) complained of minor nasal pain on the same day of ablation. No patients complained of nasal pain or obstruction during the follow-up period. In addition, 139 (28.9%) patients showed a minor increase in rhinorrhea during the first postoperative week. Of the 481 patients, 469 (97.5%) were followed-up at 6 months with no severe MWA-related complications, such as septal perforation, synechiae formation, or orbit and brain complications. MWA is a technically feasible alternative method for patients with arterial epistaxis.

The local efficacy and influencing factors of ultrasound-guided percutaneous microwave ablation in colorectal liver metastases: a review of a 4-year experience at a single center

Purpose: To investigate the clinical effectiveness and safety of ultrasound (US)-guided percutaneous microwave ablation (MWA) for colorectal liver metastasis (CRLM) and evaluate the influencing factors of local efficacy.Methods: From January 2013 to January 2017, 137 CRLM patients accepting US-guided percutaneous MWA were included. The 2450-MHz microwave ablation system and a cooled-shaft antenna were used. All patients were regularly followed up for at least 6 months. Technical success, complete ablation, local tumor progression (LTP), complications and side effects were assessed. Logistic regression analysis was used to identify the independent prognostic factors for LTP.Results: In total, 411 lesions (mean diameter 15.4 ± 7.2 mm, range 5–67 mm) were treated. Complete ablation was achieved in 99.27% (408/411) of lesions and 97.81% (134/137) of patients. LTP occurred in 5.35% (22/411) of lesions and 16.06% (22/137) of patients. LTP was more likely to occur in lesions larger than 3 cm in diameter (OR: 14.71; p < .001; 95% CI: 3.7 3–57.92), near a large vascular structure (OR: 7.04; p < .001; 95% CI: 2.41–20.60), near the diaphragm (OR: 4.02; p = .049; 95% CI: 1.05–16.11) and in patients with no response to chemotherapy before MWA (OR: 3.25; p = .032; 95% CI: 1.14–15.30). MWA was well tolerated, with a major complication rate of 3.65%, a minor complication rate of 8.03% and a mortality rate of 0%. Fever and pain were the most common side effects after MWA.Conclusions: US-guided percutaneous MWA of CRLM is a safe and effective method that is expected to become a routine treatment for local tumor control of CRLM.

Percutaneous microwave ablation for benign focal liver lesions: Initial clinical results.

Benign focal liver lesions (BFLLs) have become a common disease diagnosed in the clinical setting following the advancement of imaging techniques. The aim of the present study was to evaluate the safety and clinical outcomes of percutaneous microwave (MW) ablation, guided by ultrasound (US), for the treatment of BFLLs. Between May 2005 and January 2011, 44 BFLLs (mean maximum diameter, 33.9±13.1 mm) in 37 patients (23 women and 14 men) were treated by US-guided percutaneous MW ablation with cooled-shaft antennae. The pathological diagnosis of a BFLL was confirmed in 91.9% (34/37) of patients using a US-guided core needle biopsy prior to ablation. The BFLLs in the other 3 cases were diagnosed by typical presentations on contrast-enhanced imaging, as the patients refused to undergo biopsies. Five inclusion criteria, including indeterminate diagnoses of nodules on contrast-enhanced imaging prior to pathological verification, were recommended. The median follow-up period was 27.0 months (range, 6-73 months). The mean MW ablation energy and time were 55.0±41.6 kJ (range, 13.5-207 kJ) and 1,039.9±706.2 sec (range, 270-3,450 sec) per lesion, respectively. In total, 40 nodules (90.9%) were completely ablated, and no evidence of recurrence was demonstrated on contrast-enhanced imaging follow-up. The other 4 nodules (9.1%) were partially ablated due to the proximity of adjacent vital organs. Minor complications without sequelae included local pain and transient hemoglobinuria and no major complications occurred in peri-ablation. Overall, US-guided percutaneous MW ablation is a safe, effective and minimally invasive therapy for BFLLs in selected patients who are non-surgical candidates.

Net power and energy of cooled antenna microwave ablation:ex vivo versus in vivo results in porcine liver

To explore the net power and net energy of a cooled antenna radiator in ex vivo and in vivo porcine livers. All animal experiments complied with the guidelines of our animal use committee. Microwave ablation (MWA) was performed in ex vivo and in vivo porcine livers with a cooled-shaft antenna in different microwave ablation parameter groups (50, 80 and 110 W for 10 min). The energy losses from the microwave antenna or cables were calculated. And the net power, net energy and the relationship between net power and power readout were determined. When the power displayed by the machine indicated 50 W, 80 W and 110 W, the net power during MWA was 31.3 ± 0.6, 47.3 ± 0.8 and 62.1 ± 0.9 W ex vivo and 31.8 ± 0.8, 47.4 ± 0.3 and 61.7 ± 1.5 W in vivo. For the same power readout, the ex vivo or in vivo effective power was the same (P = 0.841, P = 0.133, P = 0.551). For both ex vivo and in vivo experiments, the ratio of microwave antenna energy loss to microwave antenna input energy was relatively constant (P = 0.613, 0.326). For the same treatment time and net power, the difference was significant between ex vivo and in vivo ablation volumes (P = 0.001, 0.006, 0.001). Using net power as a reference during MWA is more accurate compared to the traditional power readout. And net energy offers a more realistic reflection of MWA energy in tissues.

Efficacy of microwave versus radiofrequency ablation for treatment of small hepatocellular carcinoma: experimental and clinical studies

To prospectively compare microwave (MW) ablation using a modified internal cooled-shaft antenna with radiofrequency (RF) ablation in in vivo porcine liver and in patients with small hepatocellular carcinoma (sHCC). In an animal study, MW and RF ablations using a cooled-shaft antenna or internally cooled electrode were performed in in vivo porcine liver. Coagulation diameters of both ablations were compared. For clinical study, 42 patients with sHCC were treated with MW or RF ablation. Complete ablation (CA) and local tumour progression (LTP) were compared. MW ablation produced significantly larger ablation zones than RF ablation in both porcine liver and sHCC with an ablated volume of 33.3 ± 15.6 cm(3) vs. 18.9 ± 9.1 cm(3) and 109.3 ± 58.3 cm(3) vs. 48.7 ± 30.5 cm(3), respectively. The CA rate was 95.5 % (21/22) for MW ablation and 95.0 % (19/20) for RF ablation. In a 5.1-month follow-up, the LTP rate was 18.2 % (4/22) in the MW ablation group and 15.0 % (3/20) in the RF ablation group. MW ablation using a modified cooled-shaft antenna produces a larger ablation zone than RF ablation, with an efficacy similar to RF ablation in local tumour control. MW ablation is a safe and promising treatment of sHCC.

Microwave Ablation Treatment of Liver Cancer with a 2,450-MHz Cooled-shaft Antenna: Pilot Study on Safety and Efficacy

To evaluate efficacy of microwave ablation in a primary clinical study, sixty patients (44 men, 16 women; mean age 53 years) with 96, 1-8 cm (mean 3.20 ± 0.17 cm) liver cancers were treated with 2,450-MHz internally cooled-shaft antenna. Complete ablation (CA) and local tumor progression (LTP) rates as well as complications were determined. CA rates in small (<3.0 cm), intermediate (3.1-5.0 cm) and large (5.1-8.0 cm) liver cancers were 96.4% (54/56), 92.3% (24/26) and 78.6% (11/14), respectively. During a mean follow-up period of 17.17 ∓ 6.52 months, LTP occurred in five (5.21%) treated cases. There was no significant difference in the CA and LTP rates between the HCC and liver metastasis patient subgroups (P<0.05). Microwave ablation provides a reliable, efficient, and safe technique to perform hepatic tumor ablation.

Comparison of Microwave Ablation and Multipolar Radiofrequency Ablation In Vivo Using Two Internally Cooled Probes

The objective of our study was to compare the effectiveness of microwave ablation (MWA) and multipolar radiofrequency ablation (RFA) in vivo using two internally cooled probes. MWA (n=24) was performed by simultaneous application of double internally cooled-shaft antennae. Three power settings (60, 70, and 80 W) were used. Multipolar RFA (n=16) was also performed by simultaneously using two internally cooled bipolar applicators (lengths: 3-cm T30 and 4-cm T40) at 60 and 80 W. Probe spacing was 2 cm. Each power setting was applied for eight ablations with a 10-minute duration for each. The cooled-shaft probes were inserted approximately 7 cm into the liver parenchyma of seven adult Wuzhishan pigs under ultrasound guidance, and ablations were performed in various segments of porcine liver. The long-axis diameter (Dl), short-axis diameter (Ds) and the ratio Ds/Dl for each ablation was measured. Temperature curves at 0, 2, and 3 cm from the middle of the two probes and the time to reach 60°C at 0 cm from the parallel central line between the two probes were recorded. The long-axis diameter and short-axis diameter for all the power settings of MWA were significantly larger than that of both kinds of multipolar RFA (p<0.05). The rates of temperature rise to 60°C at 0 cm from the parallel central line between the two probes for all MWA power settings were significantly faster compared with RFA. MWA, by the simultaneous application of double antennae, can generate a larger ablation zone, in vivo, compared with multipolar RFA.

Microwave ablation: results in ex vivo and in vivo porcine livers with 2450-MHz cooled-shaft antenna.

Imaging-guided thermal ablation using different energy sources continues to gain favor as a minimally invasive technique for the treatment of primary and metastatic hepatic malignant tumors. This study aimed to evaluate the performance of microwave ablation with 2450-MHz internally cooled-shaft antenna in ex vivo and in vivo porcine livers. All studies were animal care and ethics committee approved. Microwave ablation was performed using a noncooled or cooled-shaft antenna in 23 ex vivo (92 ablations) and eight in vivo (36 ablations) porcine livers. Diameters of the coagulation zone were observed on gross specimens. The coagulation diameters achieved in different microwave ablation parameter groups were compared. Curve estimation analysis was performed to characterize the relationship between applied power and treatment duration and coagulation diameter (including short-axis and long-axis diameter). Coagulation zones were elliptical and an arrowed-shaped carbonization zone around the shaft was observed in all groups. But the antenna track was also coagulated in the noncooled-shaft antenna groups. In ex vivo livers, the short-axis diameter correlated with the power output in a quadratic curve fashion (R(2) = 0.95) by fixing ablation duration to 10 minutes, and correlated with the ablation duration in a logarithmic curve fashion (R(2) = 0.98) by fixing power output to 80 W. The short-axis reached a relative plateau within 25 minutes. In in vivo livers, short-axis diameter correlated with the coagulation duration in a sigmoidal curve fashion (60 W group R(2) = 0.76, 80 W group R(2) = 0.87), with a relative plateau achieved within 10 minutes for power settings of 60 W and 80 W. The internally cooled microwave antenna may be advantageous to minimize collateral damage. The short-axis diameter enlargement has a plateau by fixing power output.

Ultrasound-guided percutaneous microwave ablation of splenic metastasis: Report of four cases and literature review

Purpose: To investigate the feasibility, safety and efficacy of ultrasound guided percutaneous microwave (MW) ablation for small splenic metastasis.Materials and methods: A total of four patients with five pathologically proven splenic metastases (from ovarian, pulmonary, gastric adenocarcinoma and hepatocellular carcinoma, respectively) 1.3 to 2.9 cm in diameter were treated with microwave ablation. A cooled-shaft needle antenna was percutaneously inserted into the tumour under ultrasound guidance. One thermocouple was placed about 0.5 cm away from the tumour to monitor temperature in real time during ablation. Microwaves were emitted at 60 W for 600 s routinely and prolonged as necessary to attain temperatures sufficient to ensure tumour killing. Treatment efficacy was assessed by contrast-enhanced imaging at 1, 3 and 6 months, and every 6 months thereafter.Results: All tumours were completely ablated at a single session and no complications occurred. No local tumour progression was observed at a mean follow up of 22 ± 17.1 months (range 4 to 43 months). The ablation zone was well defined on contrast-enhanced imaging and it gradually shrank with time. One new metastatic lesion was detected in the spleen at 11 months after the ablation and was successfully treated by another MW ablation. The post-ablation survival was mean 22 months. No other complications were observed except for fever and abdominal pain.Conclusions: Ultrasound-guided percutaneous MW ablation appears to be a safe and effective minimally invasive technique for management of small splenic metastasis in selected patients.

Comparison of temperature curve and ablation zone between 915- and 2450-MHz cooled-shaft microwave antenna: Results in ex vivo porcine livers

To compare temperature curve and ablation zone between 915- and 2450-MHz cooled-shaft microwave antenna in ex vivo porcine livers. The 915- and 2450-MHz microwave ablation and thermal monitor system were used in this study. A total of 56 ablation zones and 280 temperature data were obtained in ex vivo porcine livers. The output powers were 50, 60, 70, and 80 W and the setting time was 600 s. The temperature curve of every temperature spot, the short- and long-axis diameters of the coagulation zones were recorded and measured. At all four power output settings, the peak temperatures of every temperature spot had a tendency to increase accordingly as the MW output power was increased, and except for 5mm away from the antenna, the peak temperatures for the 915 MHz cooled-shaft antenna were significantly higher than those for the 2450 MHz cooled-shaft antenna (p<0.05). Meanwhile, the short- and long-axis diameters for the 915 MHz cooled-shaft antenna were significantly larger than those for the 2450 MHz cooled-shaft antenna (p<0.05). The 915 MHz cooled-shaft antenna can yield a significantly larger ablation zone and achieve higher temperature in ablation zone than a 2450 MHz cooled-shaft antenna in ex vivo porcine livers.

Comparison of percutaneous 915 MHz microwave ablation and 2450 MHz microwave ablation in large hepatocellular carcinoma

Purpose: To compare the effectiveness of ultrasound (US)-guided percutaneous 915 MHz microwave (MW) ablation with the 2450 MHz MW ablation for large hepatocellular carcinoma (HCC) (>4 cm in diameter).Materials and methods: Patients with HCC >4 cm in diameter who underwent US-guided percutaneous MW ablation with curative intention between March 2007 and December 2008 (39) were randomly divided into two groups, 915 MHz MW group and 2450 MHz MW group. We compared the results of ablation between the two groups.Results: Fewer antenna insertions for each tumour were required in the 915 MHz MW group (3.69 ± 0.6) than in the 2450 MHz MW group (4.71 ± 1.61) (p = 0.01). According to the follow-up contrast-enhanced imagings, technique effectiveness rate was 85.7% (18/21) and 73.7% (14/19) in the 915 MHz MW group and 2450 MHz MW group, respectively (p = 0.44). The rate of local tumour progression (LTP) was 14.3% (3/21) and 26.3% (5/19) in the 915 MHz MW group and 2450 MHz MW group, respectively (p = 0.44). There were no deaths and no thrombosis of major vessels in any patient.Conclusions: Compared with 2450 MHz MW ablation, our initial experience showed that percutaneous 915 MHz MW ablation with cooled-shaft antennae was safe and could achieve a high technique effectiveness rate with fewer insertion numbers in the treatment of large HCC. Therefore, percutaneous 915 MHz MW ablation may provide a new method for the treatment of large HCC.

Microwave ablation: Results with double 915 MHz antennae in ex vivo bovine Livers

Purpose To investigate the settings for the optimal microwave ablation geometry with the simultaneous application of double 915 MHz antennae in ex vivo bovine livers, so as to provide the technical basis for treating large liver tumor in one ablation session. Materials and methods MWAs were performed on ex vivo bovine livers by simultaneously application of double 915 MHz internally cooled-shaft antennae. Four power settings (50, 60, 70 and 80 W) were used during MWAs, while application time was fixed at 10 min. Three inter-antenna distances (2.0, 2.5 and 3.0 cm) were used. Diameters and shapes of the coagulation zones were observed on gross specimens. Results (1) The coagulation shape was related to the inter-antenna distance, which was most spherical at an inter-antenna distance of 2.0 cm. A recess of the coagulation zone was observed at an inter-antenna distances of 2.5 and 3.0 cm. (2) The long-axis and short-axis coagulation diameter enlarged with increasing power output. However, there were no significant differences in the coagulation diameters between 70 and 80 W ( P > 0.05). More desirable coagulation geometry could be obtained by simultaneous application of double antennae at 70 W for 10 min with an inter-antenna distance of 2.0 cm, the long-axis and short-axis coagulation diameter were 6.95 ± 0.32 cm and 5.30 ± 0.22 cm, respectively. Conclusion Simultaneous application of double 915 MHz antennae can generate large coagulation zones with desirable shape which may be advantageous for treating large liver tumor in one ablation session.

Microwave ablation treatment of liver cancer with 2,450-MHz cooled-shaft antenna: an experimental and clinical study

To evaluate effects of microwave ablation with a 2,450-MHz internally cooled-shaft antenna in animal experiments and in a clinical study. Microwave ablation was performed using a cooled-shaft antenna in eight in vivo (36 ablations) porcine livers. The coagulation diameters achieved in different microwave ablation parameter groups were compared. Sixty patients (44 men, 16 women; mean age 53 years) with 96, 1-8 cm (mean 3.20 +/- 0.17 cm) liver cancers were treated with the same microwave ablation technique. Complete ablation (CA), local tumor progression (LTP) rates and complications were determined. In vivo livers, short axis diameter correlated with the coagulation duration in a sigmoidal curve fashion (60-W group R(2) = 0.76, 80-W group R(2) = 0.87), with a relative plateau achieved within 10 min for power settings of 60 or 80 W. Within 10 min in the 60 and 80-W groups, respectively, 89 and 85.76% of maximum short axis diameter were achieved. CA rates in small (3.0 cm), intermediate (3.1-5.0 cm) and large (5.1-8.0 cm) liver cancers were 96.43% (54/56), 92.31% (24/26) and 78.57% (11/14), respectively. During a mean follow-up period of 17.17 +/- 6.52 months, LTP occurred in five (5.21%) treated cancers. There was no significant difference in the CA and LTP rate between the HCC and liver metastasis patient subgroups (P > 0.05). The short axis diameter enlargement has a relative plateau within 10 min by fixing power output to 60 or 80 W, using the 2,450-MHz internally cooled-shaft antenna in vivo porcine livers. Effective local tumor control was achieved during one microwave ablation session.

915 MHz microwave ablation with implanted internal cooled-shaft antenna: Initial experimental study in in vivo porcine livers

Purpose To explore a preferred power output for further clinical application based on the ablated lesions induced by the four power outputs of 915 MHz microwave in experimental study of in vivo porcine livers. Materials and methods A KY2000-915 microwave ablation system with an implanted 915 MHz internal cooled-shaft antenna was used in this study. A total of 24 ablations were performed in eight in vivo porcine livers. The energy was applied for 10 min at microwave output powers of 50 W, 60 W, 70 W, and 80 W. Long-axis and short-axis diameters of the coagulation zone were measured on all gross specimens. Results The shapes of the 915 MHz microwave ablation lesions were elliptical commonly. As the power increased, the long-axis and short-axis diameters of the coagulation zone had a tendency to rise. But the long-axis diameter of the ablated lesion at 50 W was not significantly smaller than that of the ablated lesion at 60 W ( P > 0.05) and there were no statistical differences in short-axis diameters of the ablated lesion among the three power outputs of 60 W, 70 W and 80 W ( P > 0.05). After 10 min irradiation of 60 W, the long-axis and short-axis diameters of the coagulation zone were 5.02 ± 0.60 cm and 3.65 ± 0.46 cm, respectively. Conclusions For decreasing the undesired damages of liver tissues along the shaft and the number of antenna in further clinically percutaneous microwave ablation treatment, the power of 60 W may be a preferred setting among the four power outputs used in present study.

Malignant Liver Tumors: Treatment with Percutaneous Microwave Ablation—Complications among Cohort of 1136 Patients

To report the complications for percutaneous microwave (MW) ablation for the treatment of malignant liver tumors and the possible risk factors for complications in a large series of patients. The study was approved by the institutional review board; informed consent was waived because of the retrospective design. Over a 13-year period, 1136 patients with 1928 malignant liver tumors underwent ultrasonographically guided percutaneous MW ablation (583 with a noncooled-shaft antenna and 553 with a cooled-shaft antenna). A total of 3697 MW ablation sessions (average, 1.8 sessions per patient) were performed. Mortality and treatment-related major and minor complications were documented. Data were subsequently analyzed to determine whether the major complication rate was related to antenna type, tumor size, tumor location, or number of MW sessions. Two deaths not directly attributable to MW ablation were encountered. Major complications occurred in 30 (2.6%) patients and included liver abscess and empyema (n = 5), bile duct injury (n = 2), perforation of the colon (n = 2), tumor seeding (n = 5), pleural effusion requiring thoracentesis (n = 12), hemorrhage requiring arterial embolization (n = 1), and skin burn requiring resection (n = 3). Minor complications included fever; pain; asymptomatic pleural effusion, gallbladder wall thickening, and arterioportal shunt; small stricture of the bile duct; and skin burn requiring no treatment. Use of noncooled-shaft antenna and an increased number of MW ablation sessions were associated with a higher rate of major complications (P < .05). MW ablation is a well-tolerated technique with an acceptably low rate of major complications for treatment of malignant liver tumors. Use of a cooled-shaft antenna, as well as fewer MW sessions, may help minimize major complications.

Comparison of Ablation Zone Between 915- and 2,450-MHz Cooled-Shaft Microwave Antenna: Results in In Vivo Porcine Livers

The objective of our study was to compare the ablation zones of two cooled-shaft microwave antennae-one operating at 915 MHz and one operating at 2,450 MHz-in in vivo porcine livers. The 915-MHz cooled-shaft microwave antenna can lead to deeper penetration of liver tissue and can yield a significantly larger ablation zone than the 2,450-MHz cooled-shaft antenna in in vivo porcine livers. In light of the result, 915-MHz cooled-shaft microwaves may be more effective for tumor ablation, especially for large tumors.

Ultrasound Guided Percutaneous Microwave Ablation for Small Renal Cancer: Initial Experience

We evaluated the feasibility, safety and efficacy of ultrasound guided percutaneous microwave ablation for small renal cell cancers. A total of 12 patients with a pathologically proven renal cell cancer 1.3 to 3.8 cm in diameter were treated with microwave ablation. A cooled shaft needle antenna was percutaneously inserted into the tumor under ultrasound guidance. One antenna was used for tumors 2 cm or smaller and antennae were used for tumors larger than 2 cm. One thermocouple was placed about 0.5 cm away from the tumor to monitor temperature in real time during ablation. Microwaves were emitted at 50 W for 500 seconds and prolonged as necessary to attain temperatures sufficient to ensure tumor kill. Immediate treatment efficacy was assessed by contrast enhanced ultrasound 1 day after ablation. Short-term efficacy was assessed by contrast enhanced computerized tomography and/or contrast enhanced ultrasound at 1, 3 and 6 months, and every 6 months thereafter. All tumors were completely ablated at a single session and no complications occurred. No residual tumor or recurrence was observed at a median followup of 11 months (range 4 to 20). The ablation zone was well defined on contrast enhanced imaging and it gradually shrank with time. Ultrasound guided percutaneous microwave ablation appears to be a safe and effective technique for small renal cell cancer in select patients.

Liver Cancer: Increased Microwave Delivery to Ablation Zone with Cooled-Shaft Antenna—Experimental and Clinical Studies

To prospectively investigate whether the ablation zone induced with microwaves could be increased by delivering greater energy with a cooled-shaft antenna. All studies were animal care and ethics committee approved. Written informed consent was obtained from all patients. Microwave ablation was performed by using a cooled-shaft antenna in 48 ex vivo and 12 in vivo experiments with porcine livers. The coagulation diameters achieved in different microwave ablation parameter groups (60-90 W for 5-25 minutes) were compared. Ninety patients (78 men, 12 women; mean age, 53 years; age range, 20-82 years) with 133 0.8-8.0-cm (mean, 2.7 cm +/- 1.5 [standard deviation]) primary or metastatic liver cancers were treated with the same microwave ablation technique. Complete ablation (CA) and local tumor progression (LTP) rates were determined. Generalized estimating equations were used to compare differences in tumor size, ablation zone diameter, and CA and LTP rates between different patient subgroups. In the ex vivo livers, in vivo livers, and liver cancers, one application of microwave energy with 80 W for 25 minutes produced mean coagulation diameters of 5.6 x 7.4 cm, 3.5 x 5.9 cm, and 3.6 x 5.0 cm, respectively. Skin burn was not observed. CA rates in small (<or=3.0-cm), intermediate (3.1-5.0-cm), and large (5.1-8.0-cm) liver cancers were 94% (81 of 86), 91% (31 of 34), and 92% (12 of 13), respectively. During a mean follow-up period of 17.4 months, LTP occurred in seven (5%) treated cancers. There was a significant difference in LTP rate between the cirrhosis and no-cirrhosis groups (P = .03). Four patients had major complications. Delivery of greater microwave energy with cooled-shaft antennas yielded large ablation zones in ex vivo and in vivo livers and in liver cancers. Effective local tumor control was achieved during one microwave ablation session.