In this paper, a new probe is proposed for the in vivo dielectric measurement of anisotropic tissue in radio frequency band, which could accomplish the dielectric measurement in perpendicular directions by one operation. The simulative studies are performed in the frequency range from 1–1 000 MHz in order to investigate the influence of probe dimension on the energy coupling and sensitivity of measurement. The suitable probe is designed and validated for the actual measurement in this frequency band. According to the simulation results, the energy coupling of the probe could be kept below –12 dB in the frequency range from 200–400 MHz with high sensitivity of measurement for the dielectric properties of anisotropic tissue. That indicates the new type of probe has the potential to achieve the dielectric measurement of anisotropic tissue in radio frequency band and could avoid the measurement error by multi-operations in the conventional method. This new type of probe could provide a new method for the in vivo dielectric measurement of anisotropic tissue in radio frequency band.
The temperature dependence of relative permittivity and conductivity of ex-vivo pig liver, lung and heart at 2 450 MHz was studied. The relative permittivity and conductivity of three kinds of biological tissues were measured by the open-end coaxial line method. The dielectric model was fitted according to the principle of least square method. The results showed that the relative permittivity and conductivity of pig liver, pig lung and pig heart decreased with the increase of tissue temperature from 20 to 80 ℃. The relative permittivity and conductivity models of pig liver, pig lung and pig heart were established to reflect the law of dielectric properties of biological tissue changing with temperature and provide a reference for the parameters setting of thermal ablation temperature field.
Intraoperative rapid and accurate pathological diagnosis of lung nodules is crucial for formulating individualized surgical strategies. Frozen section remains the most widely used intraoperative diagnostic method. However, its diagnostic performance may be compromised by structural alterations of lung tissue and difficulties in distinguishing early-stage lung adenocarcinoma subtypes. Modified frozen section techniques and rapid immunohistochemistry have improved diagnostic accuracy to some extent through optimized specimen preparation and the incorporation of molecular marker detection. In recent years, emerging diagnostic technologies based on physical and chemical signals, including mass spectrometry, spectroscopy, and bioelectrical impedance spectroscopy, have developed rapidly. By analyzing the molecular composition, optical characteristics, or dielectric properties of tissues, these techniques enable rapid identification of lung nodules and have shown promising potential for tumor discrimination and histological classification. This article reviews the current advances in intraoperative rapid diagnostic techniques for lung nodules.