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We present a new coaxial antenna for microwave interstitial coagulative therapy, working at 2450 MHz and endowed with a miniaturized sleeve choke in order to reduce back heating effects and make the system response less dependent on the antenna insertion depth into the tissue; the way the choke is implemented makes the overall transversal size minimum and allows small adjustments of the choke section length even during operation. We describe the main technical features of the antenna and show experimental results clearly proving the choke effectiveness. Numerical simulations well agree with experimental data, confirming the suitability of the proposed device for minimally invasive medical applications. Index Terms--Interstitial coaxial applicator, microwave coagulative therapy, miniaturized choke.

A new microwave broadband method for measuring the complex resistivity of high temperature superconducting thin films is proposed.

Background This study prospectively compared intraoperative pain scores during percutaneous microwave ablation of the liver in patients randomized between continuous and pulsed energy delivery algorithms. Methods During a 12-month period, 20 patients who underwent microwave liver ablation were prospectively randomized between 2 different energy delivery modes: “continuous mode” (CM, n=10) and “pulsed mode” (PM, n=10). All ablation sessions were performed using the same microwave ablation platform under computed tomographic guidance and intravenous analgesia. Within 30 min post ablation, all patients completed a questionnaire assigning a numeric pain intensity score from 0 (no pain) to 10. Results Mean pain scores were 8.17±1.850 in the CM group and 4.50±1.567 in the PM group, with a statistically significant difference of 3.667±2.807 pain units (P=0.001). The mean procedure time was 53.5±20.90 min in the PM group vs. 58.5±17.44 min in the CM group (P=0.279). The mean size of the lesions was 2.81±0.95 cm in the PM group and 2.81±0.85 cm in the CM group (P=0.984). On a per-lesion basis, technical success was achieved in all evaluable tumors in both groups. No difference was noted in the local tumor control on the 6-month imaging evaluation. No complications were observed in the CM arm, while small perihepatic hemorrhagic fluid collections were reported in the PM group. Conclusions Both algorithms for microwave energy delivery have comparable treatment effects in terms of 6-month local tumor control for liver lesions <3 cm in diameter. PM treatments compared to CM appear to induce significantly less pain in patients undergoing percutaneous liver ablation under intravenous analgesia. [ABSTRACT FROM AUTHOR]

Purpose:The aim of this study was to develop a predictive model of the shrinkage of liver tissues in microwave ablation. Methods:Thirty-seven cuboid specimens ofex vivobovine liver of size ranging from 2 cm to 8 cm were heated exploiting different techniques: 1) using a microwave oven (2.45 GHz) operated at 420 W, 500 W and 700 W for 8 to 20 min, achieving complete carbonisation of the specimens, 2) using a radiofrequency ablation apparatus (450 kHz) operated at 70 W for a time ranging from 6 to 7.5 min obtaining white coagulation of the specimens, and 3) using a microwave (2.45 GHz) ablation apparatus operated at 60 W for 10 min. Measurements of specimen dimensions, carbonised and coagulated regions were performed using a ruler with an accuracy of 1 mm. Based on the results of the first two experiments a predictive model for the contraction of liver tissue from microwave ablation was constructed and compared to the result of the third experiment. Results:For carbonised tissue, a linear contraction of 31 ± 6% was obtained independently of the heating source, power and operation time. Radiofrequency experiments determined that the average percentage linear contraction of white coagulated tissue was 12 ± 5%. The average accuracy of our model was determined to be 3 mm (5%). Conclusions:The proposed model allows the prediction of the shrinkage of liver tissues upon microwave ablation given the extension of the carbonised and coagulated zones. This may be useful in helping to predict whether sufficient tissue volume is ablated in clinical practice. [ABSTRACT FROM PUBLISHER]

Purpose:The aim of this study was to compare the performance of a microwave ablation (MWA) apparatus in preclinical and clinical settings. Materials and method:The same commercial 2.45 GHz MWA apparatus was used throughout this study. In total 108 ablations at powers ranging from 20 to 130 W and lasting from 3 to 30 min were obtained onex vivobovine liver; 28 ablations at 60 W, 80 W and 100 W lasting 5 and 10 min were then obtained in anin vivoswine model. Finally, 32 hepatocellular carcinomas (HCCs) and 19 liver metastases in 46 patients were treated percutaneously by administering 60 W for either 5 or 10 min. The treatment outcome was characterised in terms of maximum longitudinal and transversal axis of the induced ablation zone. Results:Ex vivoablation volumes increased linearly with deposited energy (r2 = 0.97), with higher sphericity obtained at lower power for longer ablation times. Larger ablations were obtained on liver metastases compared to HCCs treated with 60 W for 10 min (p < 0.003), as ablation diameters were 4.1 ± 0.6 cm for metastases and 3.7 ± 0.3 cm for HCC, with an average sphericity index of 0.70 ± 0.04. The results on thein vivoswine model at 60 W were substantially smaller than theex vivoand clinical results (either populations). No statistically significant difference was observed betweenex vivoresults at 60 W and HCC results (p > 0.08). Conclusions:For the selected MW ablation device,ex vivodata on bovine liver was more predictive of the actual clinical performance on liver malignancies than anin vivoporcine model. Equivalent MW treatments yielded a significantly different response for HCC and metastases at higher deposited energy, suggesting that outcomes are not only device-specific but must also be characterised on a tissue-by-tissue basis. [ABSTRACT FROM PUBLISHER]

Purpose: The aim of this study was to numerically and experimentally characterise the influence of tissues dimensions on the size and shape of microwave-induced ablation zones. Materials and methods: A 2.45 GHz interstitial antenna was introduced into ex vivo bovine liver samples, delivering 60 W for 10 min; then the dimensions of the coagulated area were measured. Ablations were performed both in large samples (termed unrestricted tissue) for characterising the tissue response, and in thin samples, whose dimensions in the plane perpendicular to the antenna were smaller than the short axis of the ablated area obtained in unrestricted samples. In the numerical study the electromagnetic field emitted from the antenna and the corresponding temperature increase were evaluated in both unrestricted and thin tissue samples. Results: When the height of the tissue was smaller than the ablation diameter measured in unrestricted samples, a 7.5% increase in length of the ablated zone was experimentally observed. When both the height and width were lower than the diameter measured in unrestricted samples, an elongation of about 23.4% was experimentally obtained. The numerical study showed that the boundary conditions between the target tissue and the surrounding materials are critical. Conclusions: The ex vivo performances of microwave ablation devices are notably influenced by the shape and dimension of the tissues where the procedure takes place. Accordingly, dedicated interventional protocols should be developed for treatment planning on targets of different shape and size. [ABSTRACT FROM AUTHOR]

Several letters to the editor and a response are presented in response to articles in previous issues including "In Vivo Microwave-Induced Porcine Kidney thermoablation: Results and Perspectives from Pilot Study of a New Probe?" "The Prospects for the Chemoprevention of Prostatic Cancer," and "Improving Patient Safety in Urology."

Ultrasound-guided percutaneous Microwave Thermoablation (MWA) is an increasingly popular minimally invasive therapy for the treatment of benign thyroid nodules due to its remarkable heating velocity and resilience to heat sinking. We present a cohort of 26 patients (17 F, 9M, mean age 56.2yy) with 20 goiters (mean volume 34.9cc, min 6.5cc-max 84cc) and 6 autonomously functioning nodules (AFTNs, mean volume 11.6cc, min 3.5cc-max 24cc) treated with MWA, using the moving shot technique and a novel energy delivery algorithm (MONTREAL), based on intra-operative real-time reflectivity measurements: each moving shot was automatically terminated when reflectivity was observed to ramp up. 17G or 18G internally cooled 2.45 GHz applicators were used (AMICA-PROBE, HS HOSPITAL SERVICE SpA), operated at 15-30W. On average, each treatment deposited 9.9±5.5kJ during 696±325s, through 26.7±14.4 moving shots: the mean moving shot duration was 28.1±9.0s, yielding a mean ablation time per unit nodule volume of 34.3±19.1s/cc. No mild nor severe complications were recorded. Post-MWA ultrasound follow-up showed a mean volume reduction ratio of 59.1±10.2% [min 44% - max 80%] at 3 months and of 70.1±8.5% [min 53% - max 91%] at 6 months, with slightly better outcomes in the AFTNs sub-group (volume reduction of 65.3±10.2%/76.0±4.0% at 3/6 months and, in all cases, normal TSH values at 3 months upon pharmacological therapy suspension). MWA treatments of benign nodules with the MONTREAL technique appeared to be safe, fast, and effective. Further research is warranted to confirm these preliminary results., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Although surgical resection is still the optimal treatment option for early-stage hepatocellular carcinoma (HCC) in patients with well compensated cirrhosis, thermal ablation techniques provide a valid non-surgical treatment alternative, thanks to their minimal invasiveness, excellent tolerability and safety profile, proven efficacy in local disease control, virtually unlimited repeatability and cost-effectiveness. Different energy sources are currently employed in clinics as physical agents for percutaneous or intra-surgical thermal ablation of HCC nodules. Among them, radiofrequency (RF) currents are the most used, while microwave ablations (MWA) are becoming increasingly popular. Starting from the 90s', RF ablation (RFA) rapidly became the standard of care in ablation, especially in the treatment of small HCC nodules; however, RFA exhibits substantial performance limitations in the treatment of large lesions and/or tumors located near major heat sinks. MWA, first introduced in the Far Eastern clinical practice in the 80s', showing promising results but also severe limitations in the controllability of the emitted field and in the high amount of power employed for the ablation of large tumors, resulting in a poor coagulative performance and a relatively high complication rate, nowadays shows better results both in terms of treatment controllability and of overall coagulative performance, thanks to the improvement of technology. In this review we provide an extensive and detailed overview of the key physical and technical aspects of MWA and of the currently available systems, and we want to discuss the most relevant published data on MWA treatments of HCC nodules in regard to clinical results and to the type and rate of complications, both in absolute terms and in comparison with RFA.