Investigation of the structures and properties of antennas is important in the design of microwave ablation (MWA) system. In this study, we studied the performance of the novel tri- and single-slot antennas with frequency of 433 MHz in ex vivo conditions. The dielectric properties of liver tissue under different thermal coagulation levels were explored, which was beneficial to evaluate ablation condition of tissue and simulate temperature field. Then, the performances of the antennas were analyzed by using numerical method based on finite element method (FEM). It indicated that the present antennas with frequency of 433 MHz could produce a gourd-shaped MWA area with a longer length. Compared to antenna with frequency of 2450 MHz, the designed single-slot antenna could obtain the larger MWA area. In addition, the multiple-point ablations and a larger MWA area could be achieved simultaneously by using the present tri-slot antenna. This study has a potential for the innovative design of MWA antenna for treatment of liver tumor with a large range and a long length.
Liver thermal ablation techniques have been widely used for the treatment of liver cancer. Kinetic model of damage propagation play an important role for ablation prediction and real-time efficacy assessment. However, practical methods for modeling liver thermal damage are rare. A minimally invasive optical method especially adequate for in situ liver thermal damage modeling is introduced in this paper. Porcine liver tissue was heated by water bath under different temperatures. During thermal treatment, diffuse reflectance spectrum of liver was measured by optical fiber and used to deduce reduced scattering coefficient (μ ). Arrhenius parameters were obtained through non-isothermal heating approach with damage marker of μ . Activation energy (E ) and frequency factor (A) was deduced from these experiments. A pair of averaged value is 1.200 × 10 J mol and 4.016 × 10 s . The results were verified for their reasonableness and practicality. Therefore, it is feasible to modeling liver thermal damage based on minimally invasive measurement of optical property and in situ kinetic analysis of damage progress with Arrhenius model. These parameters and this method are beneficial for preoperative planning and real-time efficacy assessment of liver ablation therapy.
Microwave ablation (MWA) status monitoring in real time plays a key role in assessment of therapeutic e®ectiveness. As a novel real-time assessment method, near infrared spectroscopy (NIRs) was used to evaluate the ablation e±cacy. MWA experiments were carried out on in vitro porcine livers. An optical measurement system for biological tissue is developed by our lab to monitor reduced scattering coe±cient ( 0 s ) at 690 nm of the coagulation zones. It is noted that 0 s of liver tissue, which increases as the liver tissue being ablated, is clearly related with the coagulation status. 0 s of normal tissue and coagulated tissue is 3-5 and 17-19 cm À1 , respectively. Continuous changes of 0 s demonstrate that optical parameter can be used as an e±cacy evaluation factor because it essentially indicates the degree of thermal damage. Compared with temperature, optical parameter is more sensitive and accurate, which is promising for real-time therapeutic e±cacy assessment in MWA.
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