Zhigang Cheng

Computer-aided dynamic simulation of microwave-induced thermal distribution in coagulation of liver cancer

To develop a method of dynamic three-dimensional (3-D) simulation of thermal distribution in ultrasound-guided microwave coagulation therapy of liver cancer and to verify its accuracy. The specific absorption rate (SAR) values were established by measuring the temperature in equivalent phantom tests. Those values were different under different power output condition. Dynamic 3-D temperature distributions were reconstructed with a finite-element model. Testing and rectification were performed through animal experiments and clinical trials, respectively. The temperature curves in the experiments corresponded well with simulated ones in vitro--91.4% and 88.9% using single and double electrodes, respectively. The measured coagulated boundary and simulated temperature boundary had a good correspondence in 85.7% of the specimens. In both in vivo experiments and clinical trials, blood perfusion influenced the rise in temperature significantly. Temperature curves between the simulations and actual measured results showed good correspondence--67.8% (19/28) in the patients with hepatocellular carcinoma. Distance between electrodes and combined thermal distributions were both optimized with computer-aided simulation during simultaneous two-electrode coagulation. The results demonstrated that computer-aided simulation of microwave thermal distribution is an accurate and reliable method which provides a theoretical and technical basis for controlling coagulated tissue volume and placement of the electrodes during microwave coagulation therapy of liver cancer.

Ultrasound-guided percutaneous microwave ablation of benign thyroid nodules: experimental and clinical studies

PURPOSE To obtain the treatment parameters of internally cooled microwave antenna and to evaluate the feasibility of ultrasound-guided percutaneous microwave ablation (MWA) for benign thyroid nodules. MATERIALS AND METHODS MWAs were performed by microwave antenna (16G) in ex vivo porcine liver. The lesion diameters achieved in different groups (20, 25, and 30 W for 3, 5, 7, 10, and 12 min) were compared. The clinical study was approved by the ethics committee. Written informed consent was obtained from all patients. MWA was performed in 11 patients (male to female ratio=1:10; mean age, 50±7 years) with 11 benign thyroid nodules. Ultrasound scan, laboratory data, and clinical symptoms were evaluated before and 1 day and 1, 3, 6, 9, and 12 months after the procedure. RESULTS In ex vivo study, the ablation lesion at 30 W 12 min tended to have appropriate scope and spherical shape. In clinical study, the follow-up periods ranged from 1 to 9 months. At the last follow-up, the largest diameter decreased from 2.9±1.0 (range, 1.6-4.1) to 1.9±0.7 (range, 0.4-3.0) cm (P<0.01), and the volume decreased from 5.30±4.88 (range, 0.89-14.81) to 2.40±2.06 (range, 0.02-6.35) ml (P<0.01). The volume reduction ratio was 45.99±29.90 (range, 10.56-98.15) %. The cosmetic grading score was reduced from 3.20±0.79 to 2.30±0.95 (P<0.05). One patient experienced temporary nerve palsy and was recovered within 2 months after treatment. CONCLUSION The internally cooled microwave antenna can yield ideal ablation lesions, and ultrasound-guided percutaneous MWA is a feasible technique for benign thyroid nodules.

US-guided Percutaneous Microwave Ablation of Renal Cell Carcinoma: Intermediate-term Results

PURPOSE To retrospectively review intermediate-term (median, 20.1 months) clinical outcomes after microwave ablation (MWA) of renal cell carcinoma (RCC). MATERIALS AND METHODS This retrospective study was approved by the institutional review board. The results from 46 patients with 49 RCC nodules (diameter, 0.6-7.7 cm; mean, 3.0 cm ± 1.5 [standard deviation]) treated with ultrasonography (US)-guided percutaneous MWA with cooled-shaft needle antenna from April 2006 to December 2010 were reviewed. One antenna was used for tumors smaller than 2 cm; two, for tumors 2 cm or larger. The patients were followed up with contrast material-enhanced US and computed tomography or magnetic resonance imaging at 1, 3, and 6 months and every 6 months thereafter. The effect of changes in key parameters (including overall survival, disease-free survival, and local tumor progression rate) was statistically analyzed by using the log-rank test. RESULTS Technical effectiveness (complete ablation at follow-up enhanced imaging 1 month after MWA) was achieved in 48 of 49 (98.0%) tumors, and the metastasis-free rate was 100% (46 of 46). The 1-, 2-, and 3-year local tumor progression rates were 4.6%, 7.7%, and 7.7%, respectively. The cancer-specific survival rate was 100% (46 of 46), and 1-, 2-, and 3-year overall survival rates were 100%, 100%, and 97.8%, respectively. The 1-, 2-, and 3-year disease-free survival rates were 95.4%, 92.3%, and 92.3%, respectively. No major complications occurred. Multivariate analysis showed that tumor number (P = .046), tumor growth patterns (P = .003), and ablation time (P = .04) were independent unfavorable prognostic factors. CONCLUSION In the intermediate term, US-guided percutaneous MWA appears to be a safe and effective technique for the management of RCC, especially small RCC, in selected patients.

Microwave ablation assisted by a real-time virtual navigation system for hepatocellular carcinoma undetectable by conventional ultrasonography

OBJECTIVES To evaluate the efficiency and feasibility of microwave (MW) ablation assisted by a real-time virtual navigation system for hepatocellular carcinoma (HCC) undetectable by conventional ultrasonography. METHODS 18 patients with 18 HCC nodules (undetectable on conventional US but detectable by intravenous contrast-enhanced CT or MRI) were enrolled in this study. Before MW ablation, US images and MRI or CT images were synchronized using the internal markers at the best timing of the inspiration. Thereafter, MW ablation was performed under real-time virtual navigation system guidance. Therapeutic efficacy was assessed by the result of contrast-enhanced imagings after the treatment. RESULTS The target HCC nodules could be detected with fusion images in all patients. The time required for image fusion was 8-30 min (mean, 13.3 ± 5.7 min). 17 nodules were successfully ablated according to the contrast enhanced imagings 1 month after ablation. The technique effectiveness rate was 94.44% (17/18). The follow-up time was 3-12 months (median, 6 months) in our study. No severe complications occurred. No local recurrence was observed in any patients. CONCLUSIONS MW ablation assisted by a real-time virtual navigation system is a feasible and efficient treatment of patients with HCC undetectable by conventional ultrasonography.

Ultrasound-guided percutaneous microwave ablation of adrenal metastasis: Preliminary results

Purpose: To evaluate the feasibility, safety and therapeutic effects of ultrasound (US)-guided percutaneous microwave (MW) ablation in the treatment of adrenal metastasis. Materials and methods: From May 2006 to April 2008, five consecutive patients with pathologically proven unilateral adrenal metastases with a diameter of 2.3 to 4.5 cm were treated by US-guided percutaneous MW ablation. Four metastases were in the right side, one metastasis was in the left side. For each application, two cooled-shaft needle antennae were percutaneously inserted into the tumour under real-time US guidance. One thermocouple needle was inserted at the periphery of the tumour to monitor temperature in real-time during MW ablation. MW emission was ended when the entire tumour became hyperechoic and the temperature at the tumour border reached 54°C for at least 3 min. Technical success was defined as loss of tumour enhancement on contrast-enhanced imagings. Results: All adrenal metastases were completely ablated after scheduled MW ablation sessions (mean, 1.2 sessions, range, 1 to 2 sessions). No major complications related to MW ablation occurred. In a median follow-up of 19 months (range 8 to 31 months), persistent absence of tumour enhancement was observed in the treated tumour in all patients. Conclusions: US-guided percutaneous MW ablation appears to be a safe and effective therapy in selected adrenal metastasis.

Percutaneous microwave ablation for hepatocellular carcinoma adjacent to large vessels: a long-term follow-up.

PURPOSE To retrospectively evaluate the effectiveness and safety of ultrasound (US)-guided percutaneous microwave ablation (MWA) in the treatment of hepatocellular carcinoma (HCC) adjacent to large vessels. MATERIALS AND METHODS From February 2006 to February 2013, 452 patients with 605 HCC nodules were treated with US-guided percutaneous MWA. Into large vessels group (Group L), 139 patients with 163 lesions (diameter, 1.0-7.0 cm; mean, 2.5±1.1 cm) located less than 5mm away from large vessels were enrolled. And 313 patients with 442 lesions (diameter, 1.0-8.0 cm; mean, 2.5±1.2 cm) located more than 5mm away from hepatic surface, large vessels, gallbladder and gastrointestinal tract were included in control group (Group C). During the ablation, the temperature of marginal ablation tissues was monitored and controlled. RESULTS The median follow-up time was 24.5 months (range 2.1-87.7 months) in Group L, and 25.7 months (range 1.6-93.9 months) in Group C. Technical effectiveness was achieved in 157 of 163 (96.3%) tumors in Group L and 429 of 442 (97.1%) tumors in Group C, respectively (p>0.05). The 1-, 3- and 5-year local tumor progression rates and the 1-, 3- and 5-year accumulative survival rates in the two groups have no significantly statistical differences. In addition, no immediate or periprocedural major complications, no delayed complication of vessels or bile ducts injury were found in both of the two groups. CONCLUSIONS With strict temperature monitoring, US-guided percutaneous MWA is an efficient and safe technology in treating hepatocellular carcinoma adjacent to large vessels.

US-guided Percutaneous Microwave Ablation versus Open Radical Nephrectomy for Small Renal Cell Carcinoma: Intermediate-term Results

PURPOSE To review intermediate-term clinical outcomes of microwave ablation (MWA) compared with open radial nephrectomy (ORN) in small renal cell carcinoma (RCC) patients and to identify prognostic factors associated with two techniques. MATERIALS AND METHODS This retrospective study was institutional review board-approved. A total of 163 patients (127 men and 36 women) with small RCC (≤4 cm) were included from April 2006 to March 2012. Sixty-five patients underwent MWA and 98 patients underwent ORN. Survival, recurrence, and renal function changes were compared between the two groups. Effect of changes in key parameters (ie, overall survival, RCC-related survival, and metastasis-free survival) was statistically analyzed with the log-rank test. RESULTS Although overall survival after MWA was lower than that after ORN (P = .002), RCC-related survival was comparable to ORN (P = .78). Estimated 5-year overall survival rates were 67.3% after MWA and 97.8% after ORN; for RCC-related survival, estimated 5-year rates were 97.1% after MWA and 97.8% after ORN. There was one local tumor recurrence 32 months after MWA and none after ORN. Major complication rates were comparable (P = .81) between the two techniques (MWA, 2.5% vs ORN, 3.1%). The MWA group had less surgical time (P < .001), estimated blood loss (P < .001), and postoperative hospitalization (P < .001). Multivariate analysis showed age (P = .014), tumor type (P = .003), postoperative urea nitrogen (P = .042), comorbid disease (P = .005), and treatment modality (P < .001) may become survival rate predictors. CONCLUSION In intermediate term, ultrasonographically guided percutaneous MWA and ORN provide comparable results in oncologic outcomes. MWA appears to be a safe and effective technique for management of small RCC in patients with little loss of renal function.

Percutaneous cooled-tip microwave ablation under ultrasound guidance for primary liver cancer: a multicentre analysis of 1363 treatment-naive lesions in 1007 patients in China

We read with interest the article by Auernhammer and Goke1 on therapeutic strategies for liver metastasis in neuroendocrine carcinomas. Local tumour progress following radiofrequency ablation (RFA) occurred in only 6% of neuroendocrine carcinomas, but no data on overall survival and prognostic factors following RFA were available. As another thermal ablative technique for liver cancer, microwave ablation (MWA), which uses electromagnetic energy to rapidly rotate adjacent polar water molecules to achieve primarily active heating, shows the following advantages: higher intratumorous temperatures, larger ablation …

Contrast-enhanced ultrasound-guided microwave ablation for hepatocellular carcinoma inconspicuous on conventional ultrasound

Objective: To evaluate the efficiency and feasibility of contrast-enhanced ultrasound (CEUS)-guided microwave ablation for hepatocellular carcinoma inconspicuous on conventional US. Materials and methods: From March 2006 to February 2010, 107 patients (93 male, 14 female; mean age 58.9 ± 11.0 years) with 107 hepatocellular carcinoma (HCC) nodules (mean maximum diameter 19.5 ± 8.5 mm) inconspicuous on conventional US underwent microwave (MW) ablation under CEUS guidance in this study. US contrast agent was SonoVue (Bracco, Milan, Italy), a second-generation contrast agent. CEUS was performed first, and then MW ablation was carried out by means of CEUS guidance under unconscious intravenous anaesthesia if the tumours were displayed on CEUS. Results: 105 tumours were successfully visualised on CEUS by using 1–2 times contrast agent injection and MW ablation was performed under CEUS guidance. The technical success rate was 98.13% (105/107). The number of antenna insertions for each tumour was 1.89 ± 0.92, and the mean session of MW ablation for each tumour was 1.08 ± 0.28. The mean duration of energy application for each tumour was 7.05 ± 4.03 min. The follow-up time was 12–54 months (median 18 months). The technique effectiveness rate was 99.05% (104/105). The local tumour progression rate was 1.9% (2/105). There were no severe complications in any patients. Conclusion: CEUS-guided MW ablation is an efficient and feasible treatment method for patients with hepatocellular carcinoma inconspicuous on conventional US.

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

OBJECTIVE To compare temperature curve and ablation zone between 915- and 2450-MHz cooled-shaft microwave antenna in ex vivo porcine livers. MATERIALS AND METHODS 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. RESULTS 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). CONCLUSION 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.