- •We review the state-of-the-art of antenna designs in percutaneous MWA.
- •We propose the three design criteria for percutaneous MW antennas.
- •We review the current percutaneous MW antennas regarding the three design criteria.
- •We evaluate the current solutions for achieving the three design criteria.
Principle of MWA
where (V/m) is the electric field, (Wb/m2) is the magnetic flux density, (A/m) is the magnetic field, (A/m2) is the current density, (C/m2) is the electric flux density, and (C/m2) is the free charge density,
where is the relative permittivity of biologic tissue, is the electrical conductivity, (rad/s) is the angular frequency and is the permittivity of vacuum. It has been found that the relative permittivity and electrical conductivity of biological tissues are dependent on frequency, temperature, and water content [
where (kg/m3) is the tissue density, (J/(kg·K)) is the tissue specific heat, (K) is the tissue temperature, (W/(mK)) is the thermal conductivity that is also a temperature-dependent variable [
where (V/m) is the magnitude of the electrical field.
MW antenna properties
- Guerrero Lopez G.D.
- Jesus Cepeda Rubio M.F.
- Hernandez Jacquez J.I.
- et al.
where c (m/s) is the speed of light in free space, f (Hz) is the operating frequency.
where is a complex-valued reflection coefficient, which can be expressed in the logarithmic scale by the -parameter (dB), (W) and (W) indicate the reflected power and the input power, respectively.
Three basic MW antenna types
Designs to overcome the backward heating
Addition of the sleeve, choke, or cap
|Conventional choked dipole||7||30||5||3.5||0.66|
|Modified choked dipole||7||30||5||2.5||0.70|
|Conventional floating sleeve dipole||7||30||5||3.5||0.65|
|Modified floating sleeve dipole||7||30||5||2.5||0.76|
Design of antenna slots
|Ablation Zone (cm2)||Aspect Ratio||Ref.|
|-matched periodic ten-slot||30||10||2.6||–23.5||0.98|
|-matched aperiodic tri-slot||45||10||1.79||–22.3||0.98|
|Ablation zone (cm2)||Aspect ratio|
|Matched balun-free helical antenna||42||1.9||3.2||5||0.55|
|Floating sleeve dipole antenna||42||1.9||3.5||5||0.60|
Structure design of outer conductor
Addition of cooling system
Designs to fulfill the directional ablation
Designs to improve the efficiency
where and are the characteristic impedance of the load impedance and the feeding coaxial line, respectively [
where and represent the capacitance and the inductance of the quarter-wavelength transformer, respectively, is the length of the transformer part, and are the permittivity and permeability of the dielectric, respectively, and are the outer diameter of the inner conductor and the inner diameter of the outer conductor of the transformer, respectively.
where , and are the component lengths of each part of π impedance matching network, as shown in Fig. 11(B), is the inner diameter of the thickened outer conductor of the π matching network part and is the inner diameter of the coaxial cable.
where and are the component lengths of each part of L matching network, as shown in Fig. 11C, and is the inner diameter of the thickened outer conductor of the L matching network part.
Declaration of Competing Interest
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