الفهرس 
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Abstract
Microwave ablation is the most recent development in the field of Image Guided Thermal Tumor Ablation
The electromagnetic microwaves agitate water molecules in the surrounding tissue, producing friction and heat, thus inducing cellular death via coagulation necrosis.
MWA systems are composed of three basic elements; microwave generator, cable line and microwave antenna.
The standard straight antenna is capable of ablating Elliptical shaped lesion sizes of 5.5x2.8 cm and 6.3x3.5 cm, with 25 W for 8 and 12 minutes respectively. The new loop-shaped microwave antenna was developed. Its advantages are the ability to encircle a tumor, deliver large amounts of targeted microwaves and decrease the risk of tumor seeding. Microwave ablation with a cooled-shaft antenna enabled greater delivery of microwaves to produce large-volume coagulation in less number of treatment sessions.
Most ablation antennas are fed by coaxial lines. The newly developed triaxial cable line antenna improves the mismatch between the feed line and antenna, and also reduces the return currents. In turn, a smaller diameter antenna may be used for ablation of larger tumors.
The new simultaneous activation MWA system is adapted for the simultaneous activation of multiple-antenna clusters to achieve efficient production of large and controlled coagulation volumes to be used in large focal lesions.
Careful patient selection, choice of the most appropriate imaging modality, full pre-ablation imaging work-up is performed to accurately stage and locate the HCC lesions and to exclude tumor emboli and metastases. Proper coagulation status is needed to withstand the ablation procedures. MWA technique allows for flexible approaches to treatment, but percutaneous treatment is much preferable, as it is the least invasive, can be performed on an outpatient basis, and can be repeated in recurrent tumors. With imaging guidance (i.e., ultrasonography, computed tomography, magnetic resonance and fluoroscopy), the tumor is localized, and a microwave antenna is placed directly into the tumor. The therapeutic response is considered complete when contrasted CT or MRI showed no enhancement in the lesion.
The therapeutic efficacy of MWA can be augmented by other therapies. TACE may possibly control microscopic intra-hepatic metastases. As the two modalities are complementary, they can be used especially for treating large HCC.
Child-Pugh classification, tumor size, and number of tumors are identified as significant independent prognostic factors in patients with HCC treated with Microwave ablation.
The 5 year survival rate with microwave ablation of HCC is fairly high. There is a significantly higher long term survival for patients with a single tumor of 4.0 cm or smaller in maximum diameter and Child-Pugh class A cirrhosis.
No treatment related deaths for percutaneous MWA have been reported to date. The total complication rate range is (10%–14%), with 2% complication rate observed in the treatment of patients with one small tumor.
Comparing to RF; MWA results in larger zone of active heating allowing for a more uniform tumor kill in the targeted zone and next to blood vessels. The electromagnetic nature of microwaves makes it not subject to tissue boiling and charring which act as electrical insulators, thus allowing the intra-tumoral temperature to be driven considerably higher, resulting in a larger ablation zone within a shorter ablation time.
MWA may be superior to PEI for the local control of moderately or poorly differentiated small HCC (< or = 15 mm).
Microwave ablation may become one of the treatments of choice in Child-Pugh class C patients with small HCC lesions.