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Poggi G.,Institute Of Care Citta Of Pavia | Tosoratti N.,HS Hospital Service SpA | Montagna B.,Institute Of Care Citta Of Pavia | Picchi C.,Institute Of Care Citta Of Pavia
World Journal of Hepatology | Year: 2015

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 nonsurgical 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. © The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved. Source

H.S. Hospital Service S.P.A. | Date: 2013-02-18

A microwave device for the ablation of biological tissues including a coaxial antenna, including an internal conductor, surrounded by a layer of dielectric material, an external conductor coaxial to the dielectric metal tip electrically connected to the internal conductor, and a quarter wave impedance transformer including a sleeve made of dielectric material having a proximal end covered with a layer of metal, the metal extending over nearly a quarter wavelength of electromagnetic field in the dielectric at the operating frequency of the device or of odd multiples of the quarter wavelength, the layer of metal material being connected electrically to the external conductor.

Cavagnaro M.,University of Rome La Sapienza | Amabile C.,HS Hospital Service SpA | Bernardi P.,University of Rome La Sapienza | Pisa S.,University of Rome La Sapienza | Tosoratti N.,HS Hospital Service SpA
IEEE Transactions on Biomedical Engineering | Year: 2011

A new coaxial antenna for microwave ablation therapies is proposed. The antenna design includes a miniaturized choke and an arrowhead cap to facilitate antenna insertion into the tissues. Antenna matching and the shape and dimension of the area of ablated tissue (thermal lesion) obtained in ex vivo conditions are evaluated both numerically and experimentally, finding an optimal agreement between numerical and experimental data. Results show that the antenna is well matched, and that it is able to produce a thermal lesion with an average length of 6.5 cm and an average diameter of 4.5 cm in ex vivo bovine liver when irradiates 60 W for 10 min. Finally, the dependence of antenna performances on possible changes in the antennas structure is investigated, finding an optimal stability with respect to manufacturing tolerances and highlighting the fundamental role played by the antennas choke. © 2011 IEEE. Source

Farina L.,University of Rome La Sapienza | Amabile C.,HS Hospital Service SpA | Nissenbaum Y.,Hebrew University of Jerusalem | Cavagnaro M.,University of Rome La Sapienza | And 7 more authors.
2015 9th European Conference on Antennas and Propagation, EuCAP 2015 | Year: 2015

Aim of this study was to characterize the changes occurring in tissues undergoing microwave ablation, in order to more accurately predict the actual treated volume. Different experiments were conducted in restricted samples (10-40 mm side cubes) and in large samples of ex-vivo bovine liver, varying the deposited energy (60 W at 2.45 GHz, applied for 1-10 min). A comparison between pre- and post-ablation dimensions was conducted, pointing out a substantial shrinkage, non-uniform over time and space, asymmetrical along the microwave antenna axis and perpendicularly to it. The obtained results show a complex tissue behavior and a correlation between the carbonized area and the contraction phenomenon. © 2015 EurAAP. Source

Farina L.,University of Rome La Sapienza | Weiss N.,Technion IIT | Nissenbaum Y.,Hebrew University of Jerusalem | Cavagnaro M.,University of Rome La Sapienza | And 7 more authors.
International Journal of Hyperthermia | Year: 2014

Results: Overall, substantial shrinkage of 52-74% of initial tissue volume was noted. The shrinkage was non-uniform over time and space, with observed asymmetry favouring the radial (23-43 % range) over the longitudinal (21-29%) direction. Algorithmic relationships for the shrinkage as a function of time were demonstrated. Furthermore, the smallest cubes showed more substantial and faster contraction (28-40% after 1 min), with more considerable volumetric shrinkage (>10%) in muscle than in liver tissue. Additionally, CT imaging demonstrated initial expansion of the tissue volume, lasting in some cases up to 3 min during the microwave ablation procedure, prior to the contraction phenomenon.Conclusions: In addition to an asymmetric substantial shrinkage of the ablated tissue volume, an initial expansion phenomenon occurs during MW ablation. Thus, complex modifications of the tissue close to a radiating antenna will likely need to be taken into account for future methods of real-time ablation monitoring.Purpose: The aim of this study was to characterise changes in tissue volume during image-guided microwave ablation in order to arrive at a more precise determination of the true ablation zone.Materials and methods: The effect of power (20-80 W) and time (1-10 min) on microwave-induced tissue contraction was experimentally evaluated in various-sized cubes of ex vivo liver (10-40 mm ± 2 mm) and muscle (20 and 40 mm ± 2 mm) embedded in agar phantoms (N = 119). Post-ablation linear and volumetric dimensions of the tissue cubes were measured and compared with pre-ablation dimensions. Subsequently, the process of tissue contraction was investigated dynamically during the ablation procedure through real-time X-ray CT scanning. © 2014 Informa UK Ltd. Source

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