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generator and will stimulate the water molecules in the Image guidance modalities
neighboring tissue to induce heat and abrasion, resulting in MCT for the treatment of HCC can be used in an open surgery
[7]
coagulation necrosis of tissue. [12,19] procedure or in a percutaneous approach. The surgical use
of MCT for HCC is performed under the monitor of direct
The technique of cool recycling makes the temperature visualization or image guidance modalities like ultrasound
[13]
in the antenna shaft below 37 °C to avoid pain at the Type B. After verification of the tumor dimensions, the rod
puncture site of the patient undergoing MCT. Coagulation antenna is inserted into the tumor for coagulation. [17]
[41]
temperature in the ablation area is precisely controlled by
monitoring devices. Two modes of thermometry are used When a percutaneous approach is taken, there are more
[25]
simultaneously during the procedure. Thermometers are choices regarding image guidance modalities including
installed both in and outside the rod antenna. A warning ultrasound, X-ray fluoroscopy, computed tomography,
temperature is set by the operator to ensure the safety of and magnetic resonance image (MRI). [48] Among them,
the patient. [42] ultrasound and MRI offer radiation-free alternatives to image
guidance, and MRI provides high-resolution and multi-planar
[49]
For ablation of larger tumors, two to three microwave antenna images. However, MRI-compatible microwave electrode
needles can be used at the same time to produce maximum and accessories must be prepared. [50]
coagulation area. Simultaneous use of two antenna needles
[43]
could not be simply regarded as a linear superposition of CURRENT STATUS IN CLINICS
two solitary thermal fields, because the interaction between
two thermal fields constitutes a spherical coagulation area Cool-tip MCT for the treatment of HCC has several beneficial
that is significantly greater than the coagulation area when characteristics in clinical application, as well as microwave
two needles are used separately with the same power and systems, with an electrode with saline passing through and
injected continuously into the target area. Direct puncture
[51]
time period. The mode of impulse transmission enhances of lesions makes the operational procedure relatively simple
[44]
the depth of microwave penetration and contributes to and easy. [17]
the increase in coagulation area and the decrease in tissue
carbonization. [45]
General anesthesia is necessary in a surgical MCT procedure
while in a percutaneous approach local anesthesia is
Parameters commonly used with venous analgesics such as pethidine and
Most systems use 2,450 MHz as the working frequency sedatives as additional pain-killers. Under the guidance of
[52]
for tumor destruction. [4,12] For MCT, the higher the a selected image modality, the tumor is localized, and the
frequency, the more powerful the instant energy, but needle is directly inserted into the tumor with the needle tip
the weaker the penetrating power. [46] Thus, the 2,450 placed at a calculated point. The ablated area is assessed
[11]
MHz microwave is usually used for MCT because of the through real-time images to find tumor tissues that are still
advantage of its powerful instant energy while the 915 and viable. Repeated ablation procedures are performed to
[40]
433 MHz microwaves with strong penetration are used for ensure no viable tumor tissue remained at the site. [53]
thermotherapy of other diseases. [3,4] The novel dual-band
systems have two working frequencies including 2,450 and MCT is different from RFA, which has a longer history and
915 MHz. The 915 MHz microwave creates a remarkably has acquired a broad acceptance as a first-line treatment
[47]
larger area of ablation and is suitable for one-time ablation option for early HCC. However, RFA has the limitations
[54]
of large tumors in-situ because this frequency produces associated with treating large tumors and tumors at high-risk
double depth of penetration in tissues compared with locations. MCT has the advantage of treating larger tumors
[22]
that produced by the 2,450 MHz microwave. The output and is regarded as a valuable alternative to RFA. Compared
[48]
power for ablation is usually set at 40-80 W. Microwave with other available modalities and devices for thermal
[4]
with high power and high frequency (135 W, 2.45 GHz) ablation, MCT offers the advantages of greater volume of
has been used in the animal study for producing large tumor ablation, consistently greater temperatures in the
ablation areas in short time periods. Power and time ablation area, better analysis of heat transfer, and shorter
[28]
period for coagulation are determined on the basis of ablation sessions. [7]
tumor size. With tumor sizes ranging from 3 to 5 cm in
[9]
diameter, microwave power for ablation is set at 50-60 W for A recent single-center study reported the treatment outcome
[4]
5-15 min; with tumors over 5 cm in diameter, two needles of MCT for the treatment of 719 consecutive HCC patients
are used simultaneously. [25] in more than 15 years. The 1-, 3-, 5-, 7-, and 10-year overall

Hepatoma Research | Volume 1 | Issue 3 | October 15, 2015 161