Parameter estimation in high-intensity focused ultrasound therapy

Numerical Estimation of SAR and Temperature Distributions inside Differently Shaped Female Breast Tumors during Radio-Frequency Ablation

Radio-frequency (RF) ablation is a reliable technique for the treatment of deep-seated malignant tumors, including breast carcinoma, using high ablative temperatures. The paper aims at a comparative analysis of the specific absorption rate and temperature distribution during RF ablation with regard to different female breast tumors. In the study, four tumor models equivalent to an irregular tumor were considered, i.e., an equivalent sphere and ellipsoid with the same surfaces and volumes as the irregular tumor and an equivalent sphere and ellipsoid inscribed in the irregular tumor. An RF applicator with a specific voltage, operating at 100 kHz inserted into the anatomically correct female breast, was applied as a source of electromagnetically induced heat. A conjugated Laplace equation with the modified Pennes equation was used to obtain the appropriate temperature gradient in the treated area. The levels of power dissipation in terms of the specific absorption rate (SAR) inside the naturalistically shaped tumor, together with the temperature profiles of the four simplified tumor models equivalent to the irregular one, were determined. It was suggested that the equivalent tumor models might successfully replace a real, irregularly shaped tumor, and the presented numeric methodology may play an important role in the complex therapeutic RF ablation process of irregularly shaped female breast tumors.

Multifunctional Drug-Loaded Phase-Change Nanoparticles Inhibit the Epithelial-Mesenchymal Transition of Hepatocellular Carcinoma by Affecting the Activity of Activated Hepatic Stellate Cells

Objectives. Preparation of a multifunctional drug-loaded phase-change nanoparticle (NP), pirfenidone perfluoropentane liposome NPs (PPL NPs), and combined with low-intensity focused ultrasound (LIFU) to influence epithelial mesenchymal transition (EMT) for hepatocellular carcinoma (HCC) by inhibiting the activity of activated Hepatic Stellate Cells (a-HSCs). Methods. PPL NPs were prepared by the thin film dispersion method. The appearance, particle size, zeta potential, encapsulation efficiency, drug loading rate, drug release in vitro, and stability of PPL NPs were tested. The role of a-HSCs in HCC metastasis was studied by CCK-8, colony formation assay, apoptosis, cellular uptake assay, wound healing assay, and Transwell assay. Western blot was used to detect the related protein expression levels. In vitro and vivo, the acoustic droplet vaporization (ADV) of PPL NPs was tested at different times and LIFU intensities. Biosafety of the PPL NPs was assessed by measuring nude mouse body weight and hematoxylin and eosin (H&E) staining. Results. The results showed that the PPL NPs had good biosafety, with an average particle size of 346.6 ± 62.21 nm and an average zeta potential of -15.23 mV. When the LIFU power is 2.4 W/cm2, it can improve the permeability of cells, further promote the uptake of drugs by cells, and improve the toxicity of drugs. In vitro experiments showed that PPL NPs could inhibit the proliferation of a-HSCs cells, thereby affecting the metastasis of HCC, and were related to the TGFβ-Smad2/3-Snail signaling pathway. Both in vivo and in vitro PPL NPs enhanced ultrasound imaging by LIFU-triggered ADV. Conclusion. The PPL NPs designed and prepared in this study combined with LIFU irradiation could significantly alter the EMT of HCC by inhibiting LX2. Clinically, PPL NPs will also be considered a promising contrast agent due to their ultrasound imaging capabilities.