Relaxation-based viscosity mapping for magnetic particle imaging

Magnetic particle imaging (MPI) has been shown to provide remarkable contrast for imaging applications such as angiography, stem cell tracking, and cancer imaging. Recently, there is growing interest in the functional imaging capabilities of MPI, where 'color MPI' techniques have explored separating different nanoparticles, which could potentially be used to distinguish nanoparticles in different states or environments. Viscosity mapping is a promising functional imaging application for MPI, as increased viscosity levels in vivo have been associated with numerous diseases such as hypertension, atherosclerosis, and cancer. In this work, we propose a viscosity mapping technique for MPI through the estimation of the relaxation time constant of the nanoparticles. Importantly, the proposed time constant estimation scheme does not require any prior information regarding the nanoparticles. We validate this method with extensive experiments in an in-house magnetic particle spectroscopy (MPS) setup at four different frequencies (between 250 Hz and 10.8 kHz) and at three different field strengths (between 5 mT and 15 mT) for viscosities ranging between 0.89 mPa • s-15.33 mPa • s. Our results demonstrate the viscosity mapping ability of MPI in the biologically relevant viscosity range. © 2017 Institute of Physics and Engineering in Medicine

Relaxation-based viscosity mapping for magnetic particle imaging

Magnetic particle imaging (MPI) has been shown to provide remarkable contrast for imaging applications such as angiography, stem cell tracking, and cancer imaging. Recently, there is growing interest in the functional imaging capabilities of MPI, where 'color MPI' techniques have explored separating different nanoparticles, which could potentially be used to distinguish nanoparticles in different states or environments. Viscosity mapping is a promising functional imaging application for MPI, as increased viscosity levels in vivo have been associated with numerous diseases such as hypertension, atherosclerosis, and cancer. In this work, we propose a viscosity mapping technique for MPI through the estimation of the relaxation time constant of the nanoparticles. Importantly, the proposed time constant estimation scheme does not require any prior information regarding the nanoparticles. We validate this method with extensive experiments in an in-house magnetic particle spectroscopy (MPS) setup at four different frequencies (between 250 Hz and 10.8 kHz) and at three different field strengths (between 5 mT and 15 mT) for viscosities ranging between 0.89 mPa • s-15.33 mPa • s. Our results demonstrate the viscosity mapping ability of MPI in the biologically relevant viscosity range. © 2017 Institute of Physics and Engineering in Medicine

MORPHOLOGICAL CHANGE OF MYOCARDIUM IN HYPOTHYROIDISM

Introduction. The work covers data on the most common forms of functional disorders of the thyroid gland – hypothyroidism and a laboratory research on myocardium, performed on baby rat’s hearts to study dystrophic changes observed in a state of hypothyroidism. The aim of the research is to reveal and analyze dystrophic changes observed in a state of hypothyroidism, which developed as a result of a long-term persistent deficiency of thyroid hormones or decreasing their biological effect on the cellular level. Material and methods. The object of the study was the hearts of 50 white outbred rats of the following age groups: 3, 7, 14, 21, 30 days. Animals were divided into 3 groups. After every experimental week, the hormone level from the rat caudate vein was determined. The control and experimental groups of animals were kept in the same vivarium conditions. At the end of the experiment, the baby rats of the experimental and control groups were killed under anesthesia, the heart was kept in 10% neutral formalin, followed by piping in alcohols, pouring in paraffin and preparing histological sections. Sections of 8-10 microns thick were prepared from paraffin blocks. Microsections were stained with hematoxylin and eosin, van Gieson. Results and discussion. The study process of growth dynamics of the wall thickness of both the left and right ventricles of baby rats’ heart in hypothyroidism state, depending on different parts of the heart, showed that the wall thickness of all departments was less than the control indices. Comparing the thicknesses of wall of the right and left ventricles of the baby rats of the experimental group with the control group, a significant lag in myocardial indices was revealed. Those changes were most pronounced in 14-day-old baby rats, manifested by perivascular and interstitial lymphohistiocytic infiltrate. Conclusion. The intensity and prevalence of morphological changes are less pronounced, destructive changes in the myocardium are not detected. The use of antioxidants in analysis of experimental hypothyroidism on laboratory animals has a protective effect and prevents the development of severe destructive changes in the myocardium

Response to “Electron Microscopy of Biological Specimens in Liquid Water”

10.1016/j.bpj.2012.05.043Biophysical Journal1031165-166BIOJ

Imaging Protein Structure in Water at 2.7 nm Resolution by Transmission Electron Microscopy

AbstractWe demonstrate an in situ transmission electron microscopy technique for imaging proteins in liquid water at room temperature. Liquid samples are loaded into a microfabricated environmental cell that isolates the sample from the vacuum with thin silicon nitride windows. We show that electron micrographs of acrosomal bundles in water are similar to bundles imaged in ice, and we determined the resolution to be at least 2.7 nm at doses of ∼35 e/Å2. The resolution was limited by the thickness of the window and radiation damage. Surprisingly, we observed a smaller fall-off in the intensity of reflections in room-temperature water than in 98 K ice. Thus, our technique extends imaging of unstained and unlabeled macromolecular assemblies in water from the resolution of the light microscope to the nanometer resolution of the electron microscope. Our results suggest that real-time imaging of protein dynamics is conceptually feasible

Relaxation-based color magnetic particle imaging for viscosity mapping

Magnetic particle imaging (MPI) uses superparamagnetic iron oxide (SPIO) nanoparticles as biomedical imaging tracers. The potential applications of MPI have recently been broadened by the introduction of “color” MPI techniques that can distinguish different nanoparticles and/or environments, e.g., by exploiting the relaxation behavior of SPIOs. One of the important applications of color MPI techniques is viscosity mapping. In this work, we show relaxation-based color MPI experiments that can distinguish the biologically relevant viscosity range of up to 5 mPa s. To find the optimal drive field parameters for viscosity, we compare color MPI results at three different frequencies. We show that frequencies around 10 kHz are well-suited for viscosity mapping using the multicore cluster Nanomag-MIP nanoparticles, providing a one-to-one mapping between the estimated relaxation time constant and viscosity