Tissue permittivity: a monitor for progressive tissue fibrosis as observed in bystander tissues following experimental high dose rate irradiation

Measure of lung dielectric proprieties in patients with Idiopathic Pulmonary Fibrosis: correlation with clinical, radiological and pulmonary functional parameters

BACKGROUND

Dielectric properties of biological tissues are biophysical parameters; in lung they change with amount of air, blood and parenchyma. Remote Dielectric Sensing (ReDS™) technology measures dielectric properties of lung tissues quantifying the content of fluids inside the scan volume. We aimed to evaluate the reliability of ReDS™ measure in Idiopathic Pulmonary Fibrosis (IPF) patients and in healthy volunteers, and to investigate the correlation of ReDS™ score with clinical, radiological and functional parameters.

METHODS

We conducted a prospective observational study, including 52 patients with diagnosis of IPF and 17 healthy volunteers; for each patient we recorded: complete functional evaluation, dyspnoea score (mMRC scale), Usual Interstitial Pneumonia (UIP) Computed Tomography (CT) pattern (UIP definite or probable) and ReDS™ measure (expressed in %).

RESULTS

ReDS™ measure was reported as correct both in patients and controls, the firsts with higher scores (33.8% vs 29.1%, p = 0.003). In IPF patients we observed a significant inverse correlation with ReDS™ score and Forced Vital Capacity (FVC), Vital Capacity (VC) and Total Lung Capacity (TLC) measures and, when we considered only patients with UIP definite CT pattern, the correlation was inverse with FVC, VC, TLC, DLCO. In IPF patients the higher was mMRC dyspnoea index, the higher was ReDS™ score. No significant correlations were observed between ReDS™ score and functional parameters in healthy controls.

DISCUSSION

We demonstrated a correlation of ReDS™ scores with some functional (mainly indicative or diagnostic for restriction) and clinical parameters in IPF patients; the score was correlated with density of tissues possibly quantifying tissue fibrosis in IPF patients.

Impedance and conductivity of bovine myocardium during freezing and thawing at slow rates - implications for cardiac cryo-ablation

Increasing impedance during freezing might be a valuable marker for guiding cardiac cryo-ablation. We provide model based insights on how decreasing temperature below the freezing point of tissue relates to the percentage of frozen water. Furthermore, we provide experimental data for comparing this percentage with the increase in impedance. Measurements were performed on a bovine tissue sample at frequencies between 5 and 80 kHz. Slow cooling and heating rates were applied to minimize temperature gradients in the myocardial sample and to allow accurate assessment of the freezing point. Computer simulation was applied to link impedance with temperature dependent conductivities. The osmotic virial equation was used to estimate the percentage of frozen water. Measurements identified the freezing point at -0.6 ^∘C. At -5 ^∘C, impedance rose by more than a factor of ten compared to that at the freezing point and the percentage of frozen water was estimated as being 89%. At -49 ^∘C impedance had increased by up to three orders of magnitude and ice formation was most pronounced in the extracellular space. Progressive ice formation in tissue is reflected by a large increase in impedance, and impedance increases monotonically with the percentage of frozen water. Its analysis allows for experimental assessment of factors relevant to cell death. Solid ice contributes to the rupture of the micro-vasculature, while phase shifts reflect concentration differences between extra- and intracellular space driving osmotic water transfer across cell membranes.

New electrical impedance methods for the in situ measurement of the complex permittivity of anisotropic skeletal muscle using multipolar needles

This paper provides a rigorous analysis on the measurement of the permittivity of two-dimensional anisotropic biological tissues such as skeletal muscle using the four-electrode impedance technique. The state-of-the-art technique requires individual electrodes placed at the same depth in contact with the anisotropic material, e.g. using monopolar needles. In this case, the minimum of measurements in different directions needed to estimate the complex permittivity and its anisotropy direction is 3, which translates into 12 monopolar needle insertions (i.e. 3 directions × 4 electrodes in each direction). Here, we extend our previous work and equip the reader with 8 new methods for multipolar needles, where 2 or more electrodes are spaced along the needle's shaft in contact with the tissue at different depths. Using multipolar needles, the new methods presented reduce the number of needle insertions by a factor of 2 with respect to the available methods. We illustrate the methods with numerical simulations and new experiments on ex vivo ovine skeletal muscle (n = 3). Multi-frequency longitudinal and transverse permittivity data from 30 kHz to 1 MHz is made publicly available in the supplementary material. The methods presented here for multipolar needles bring closer the application of needle electrical impedance to patients with neuromuscular diseases.

Bio-Physical Modeling, Characterization, and Optimization of Electro-Quasistatic Human Body Communication

Human body communication (HBC) has emerged as an alternative to radio wave communication for connecting low power, miniaturized wearable, and implantable devices in, on, and around the human body. HBC uses the human body as the communication channel between on-body devices. Previous studies characterizing the human body channel has reported widely varying channel response much of which has been attributed to the variation in measurement setup. This calls for the development of a unifying bio-physical model of HBC, supported by in-depth analysis and an understanding of the effect of excitation, termination modality on HBC measurements. This paper characterizes the human body channel up to 1 MHz frequency to evaluate it as a medium for the broadband communication. The communication occurs primarily in the electro-quasistatic (EQS) regime at these frequencies through the subcutaneous tissues. A lumped bio-physical model of HBC is developed, supported by experimental validations that provide insight into some of the key discrepancies found in previous studies. Voltage loss measurements are carried out both with an oscilloscope and a miniaturized wearable prototype to capture the effects of non-common ground. Results show that the channel loss is strongly dependent on the termination impedance at the receiver end, with up to 4 dB variation in average loss for different termination in an oscilloscope and an additional 9 dB channel loss with wearable prototype compared to an oscilloscope measurement. The measured channel response with capacitive termination reduces low-frequency loss and allows flat-band transfer function down to 13 KHz, establishing the human body as a broadband communication channel. Analysis of the measured results and the simulation model shows that instruments with 50 Ω input impedance (Vector Network Analyzer, Spectrum Analyzer) provides pessimistic estimation of channel loss at low frequencies. Instead, high impedance and capacitive termination should be used at the receiver end for accurate voltage mode loss measurements of the HBC channel at low frequencies. The experimentally validated bio-physical model shows that capacitive voltage mode termination can improve the low frequency loss by up to 50 dB, which helps broadband communication significantly.

Bone-targeted therapies in metastatic castration-resistant prostate cancer: evolving paradigms

Majority of patients with metastatic castrate resistant prostate cancer (mCRPC) develop bone metastases which results in significant morbidity and mortality as a result of skeletal-related events (SREs). Several bone-targeted agents are either in clinical use or in development for prevention of SREs. Bisphosphonates were the first class of drugs investigated for prevention of SREs and zoledronic acid is the only bisphosphonate that is FDA-approved for this indication. Another bone-targeted agent is denosumab which is a fully humanized monoclonal antibody that binds to the RANK-L thereby inhibiting RANK-L mediated bone resorption. While several radiopharmaceuticals were approved for pain palliation in mCRPC including strontium and samarium, alpharadin is the first radiopharmaceutical to show significant overall survival benefit. Contemporary therapeutic options including enzalutamide and abiraterone have effects on pain palliation and SREs as well. Other novel bone-targeted agents are currently in development, including the receptor tyrosine kinase inhibitors cabozantinib and dasatinib. Emerging therapeutics in mCRPC has resulted in great strides in preventing one of the most significant sources of complications of bone metastases.