Dielectric Properties of Normal and Metastatic Lymph Nodes Ex Vivo From Lung Cancer Surgeries.

The dielectric properties of normal and tumor human tissues have been widely reported in recent years. However, the dielectric properties of intrathoracic lymph nodes (LNs) have not been reported. In this communication, we measured the dielectric properties (i.e., permittivity and conductivity) of ex vivo intrathoracic LNs obtained from lung cancer surgeries. Results show that the permittivity and conductivity of metastatic LNs are higher than those of normal LNs over the frequency range of 1 MHz-4 GHz. Statistically significant differences are observed at single specific frequencies (64, 128, 298, 433, and 915 MHz and 2.45 GHz). Our study provides the basic data to support future-related research and fills the research gap on the dielectric properties of LNs in the lungs. Bioelectromagnetics. 2020;41:148-155. © 2020 Bioelectromagnetics Society.

[Analysis of dielectric properties of metastatic and non-metastatic lymph nodes from lung cancer surgeries using an open-ended coaxial probe].

OBJECTIVE: To investigate the differences in dielectric properties (relative dielectric constant and conductivity) between metastatic and non-metastatic lymph nodes (LNs). METHODS: An open-end coaxial probe (1 MHz to 4 GHz) was used to measure the dielectric properties of the LNs obtained from 76 lung cancer patients. According to the results of pathological examination, the LNs were divided into metastatic and non-metastatic LNs, and the metastatic LNs were divided into lung squamous cell carcinomas and adenocarcinoma. The differences in dielectric properties of the LNs were analyzed at 1 MHz to 4 GHz and at 6 single frequencies (64, 128, 298, 433, 915, and 2450 MHz). RESULTS: The metastatic LNs showed higher dielectric properties than non-metastatic LNs in the frequency range from 1 MHz to 4 GHz. No significant differences were found in the dielectric properties between metastatic LNs of lung squamous cell carcinoma and adenocarcinoma. At the 6 single frequencies, the metastatic and non-metastatic LNs showed significant differences in their dielectric properties (P < 0.01). CONCLUSIONS: The open-ended coaxial probe technology is not capable of identifying the pathological type of the primary lung cancer from which the metastatic LNs are derived, but it can identify the differences in dielectric properties between metastatic and non-metastatic LNs, and thus provide a reliable means for identification of LN metastasis of lung cancer.

[Development of a near-infrared fluorescence imaging system based on fluorescence properties of methylene blue].

OBJECTIVE: To develop a near-infrared fluorescence imaging system based on the fluorescence properties of methylene blue. METHODS: According to the optical properties of methylene blue, we used a custom-made specific LED light source and an interference filter, a CCD camera and other relevant components to construct the near-infrared fluorescence imaging system. We tested the signal-to-background ratio (SBR) of this imaging system for detecting methylene blue under different experimental conditions and analyzed the SBR in urine samples collected from 15 Wistar rats with intravenous injection of methylene blue at the doses of 0, 1.4, 1.6, 1.8, or 2.0 0 mg/kg methylene blue. RESULTS: The SBR of this imaging system for detecting methylene blue was affected by the concentration of methylene blue and the distance from the sample (P<0.05). In the urine samples from Wistar rats, the SBR varied with the the injection dose, and the rats injected with 1.6 mg/kg methylene blue showed the highest SBR (8.71∓0.20) in the urine (P<0.05). CONCLUSION: This near-infrared fluorescence imaging system is useful for fluorescence detection of methylene blue and can be used for real-time recognition of ureters during abdominal surgery.

[Differences in dielectric properties between mucosal and serosal surface of malignant colorectal tissues, adjacent tissues at 1 cm and 3 cm and normal colorectal tissues].

OBJECTIVE: To investigate the differences in dielectric properties (relative permittivity and conductivity) between the mucosal surface and serosal surface of malignant colorectal tissues, adjacent tissues at 1 cm and 3 cm from the tumor focus and normal colorectal tissues. METHODS: The dielectric properties of the mucosal and serosal surface of malignant colorectal tissues, adjacent tissues (1 cm and 3 cm) and normal colorectal tissues from 39 patients with colorectal cancer were measured with an open-ended coaxial probe within the frequency range of 50 MHz-3 GHz, and the corresponding dielectric properties were analyzed respectively; statistical tests of the data were used to analyze the dielectric properties at 6 specific frequency points. RESULTS: The dielectric properties were significantly higher in the malignant mucosa surface than in the adjacent tissues and normal colorectal tissues at the 6 specific frequency points (P<0.01). The dielectric properties decreased progressively in adjacent tissues at 1 cm and 3 cm and normal mucosa surface. The mucosal and serosal surface of malignant tissues showed significant differences in dielectric properties at 64 MHz, 128 MHz, 298 MHz, 433 MHz, and 915 MHz (P<0.01) but not at 2450 MHz (P>0.01), but such differences were not observed in normal tissues (P>0.01). CONCLUSION: The dielectric properties of the mucosal surface of the mucosal decrease in the order of malignant colorectal tissue, adjacent tissues at 1 cm and 3 cm from the tumor foci and normal colorectal tissues. The dielectric properties are higher in the mucosal surface than in the serosal surface in the malignant tissue, but comparable in normal colorectal tissues.