Physics in Medicine最新文献

Adequate hemodialysis minimizes complications and improves end-stage renal disease patient survival. Our study proposed a methodology for estimating hemodialysis parameters using two-compartment modelling together with Monte Carlo simulation of the probabilities of the model outputs. In addition, we modelled the removal of uremic toxins during hemodialysis, in comparison with the actual concentration of these toxins in the blood serum. Blood urea and phosphates were measured every 30 min throughout hemodialysis in 10 patients. Using a Monte Carlo simulation on the two-compartment model we estimated hemodialysis compatibility parameters for each patient individually. In patients with non-diabetic kidney disease, the actual urea and phosphate excretion dynamics were consistent with those predicted by the two-compartment model regardless of age, sex, non-diabetic comorbidities, duration of hemodialysis, residual diuresis, or type of vascular access. To measure compatibility, we used graph matching together with a quantitative measure given by a normalized coefficient of determination. In patients with end-stage diabetic kidney disease, the toxin elimination dynamics were significantly greater in the first 30 min of hemodialysis than in patients with non-diabetic kidney disease.

It remains unclear how spike-wave discharges (SWDs) in electroencephalograms (EEGs) arise, although some researchers believe that there is some focus in the deep brain and others have pointed out the importance of the interaction between the thalami and cortices. My previous work hypothesized that possible resonance in white matter may induce extremely large amplitude discharges in an EEG, which are associated with SWDs. The visual evoked potential (VEP) technique revealed a resonance phenomenon that supports this hypothesis. In this research, I theoretically reconsidered the resonance phenomenon based on the cable theory modified by considering dielectric dispersion. If both the resistive and capacitive currents in the dielectric material contribute to conduction along an axon, we can show that the current amplitude has a single maximum at a certain frequency and this amplitude depends on the geometrical ratio of capacitance to resistance. The frequency can be common for any axon in a wide white-matter area. We can infer that SWDs will arise, when the frequency generated by the thalamic reticular nucleus neurons coincides with the resonance frequency of the white matter. The resonance frequency predicted by the modified theory is close to the known frequency of the SWDs.

Steam sterilisation is a commonly used method in the sterilisation of surgical instruments. To ensure the sterility of the sterilised goods an evaluation of the sterilisation process is required. This might be achieved either through physical measurements or indicators. Optimal sterilisation results are achieved by removing the air from the sterilisation chamber. In this paper a new computational fluid dynamics (CFD) based approach is presented, which allows to calculate the steam distribution within a sterilisation chamber with focusing on hollow loads. Additional measurements were performed using a self-developed measurement chamber to validate the CFD model. A modified process challenge device (PCD) with different tube lengths in combination with a chemical indicator (CI) was tested, to identify the volumetric influence of the lumen on the resulting air-steam mixture therein. A numerically efficient model was developed to determine a steam volume fraction threshold leading to a response of the CI. This study aims to predict the volumetric amount of steam which is necessary in order to pass a PCD test fitted with a CI. Both the CFD model and the measurements showed that often an insufficient steam penetration is indicated by PCDs which can lead to an insufficient sterilisation of hollow loads.

A finite-difference time-domain (FDTD) technique was used to model the complex propagation of ultrasonic waves through the human radius. A three-dimensional model of the radius, including its uniaxial anisotropy and heterogeneity, was created using structural data obtained from high-resolution peripheral quantitative computed tomographic images. FDTD simulations were performed to achieve adequate wave convergence on the virtual fracture site in the mid shaft of a long cortical bone. The simulation comprised two steps. The first involved wave propagation from the virtual fracture site to two ring-shaped outside receiver arrays. In the second step, the receiver arrays functioned as transmitters, generating re-radiated waves based on the arrival times of the received waves. The re-radiated waves propagating from the transducer arrays were found to converge around the fracture site. Our findings will help to improve the propagation of ultrasonic irradiation through a cast to target a fracture site.

Extracellular acidification is a basic indicator for alterations in two vital metabolic pathways: glycolysis and cellular respiration. Measuring these alterations by monitoring extracellular acidification using cell-based biosensors such as LAPS plays an important role in studying these pathways whose disorders are associated with numerous diseases including cancer. However, the surface of the biosensors must be specially tailored to ensure high cell compatibility so that cells can represent more in vivo-like behavior, which is critical to gain more realistic in vitro results from the analyses, e.g., drug discovery experiments. In this work, O₂ plasma patterning on the LAPS surface is studied to enhance surface features of the sensor chip, e.g., wettability and biofunctionality. The surface treated with O₂ plasma for 30 s exhibits enhanced cytocompatibility for adherent CHO–K1 cells, which promotes cell spreading and proliferation. The plasma-modified LAPS chip is then integrated into a microfluidic system, which provides two identical channels to facilitate differential measurements of the extracellular acidification of CHO–K1 cells. To the best of our knowledge, it is the first time that extracellular acidification within microfluidic channels is quantitatively visualized as differential (bio-)chemical images.

Scanning acoustic microscopy in the gigahertz regime (GHz-SAM) has long been a versatile and complementary micro and nanoscopic imaging and analysis tool. Nevertheless, it remained obscured to some extent, compared to its counterparts, such as atomic force microscopy (AFM), despite its unique capability of subsurface analysis. Some current research in our lab at Georgia Tech Lorraine is devoted to the use of the subsurface imaging of GHz-SAM in biological tissues, which has been restricted, mostly, to very stiff materials, in terms of acousto-mechanical impedance, such as metals.

The feasibility, degrees of complexity, the different techniques, and future fates of (GHz-SAM) are discussed with particular focus on those most used in the biological applications, such as the combined phase and magnitude contrasts acoustic microscopy.

This paper gives a general overview of SAM, the peculiarities of GHz-SAM with emphasis on the restrictions that led to the semi-obscurity of GHz-SAM so far, and reveals some recent research developments in this field in our laboratory.

Background

Electrical Properties Tomography (EPT) is a new sequence which delivers information on tissue electrical conductivity. It has been mostly used for tumor imaging. Ischemic stroke is another promising application. The aim of this study was to demonstrate the feasibility of EPT in a rodent model of stroke.

Methods

Wistar rats with and without temporary middle cerebral occlusion (MCAo) were examined in a 3T scanner. EPT was performed using a Steady-State Free-Precession (SSFP) sequence. From the transceive phase ɸ of these SSFP scans, conductivity σ was estimated by the equation σ = Δɸ/(2μ₀ω) with Δ the Laplacian operator, μ₀ the magnetic permeability, and ω the Larmor frequency. Subsequently, a median filter was applied.

Results

Healthy cortical grey matter, white matter and cerebrospinal fluid showed significantly different conductivity (0.83 ± 0.14 S/m, 0.63 ± 0.06 S/m, 2.33 ± 0.49 S/m, p < 0.05). Infarcted tissue exhibited increased conductivity (1.937 ± 1.347 vs. 0.782 ± 0.429 S/m, p < 0.05).

Conclusion

EPT is feasible in a rodent model of stroke. Infarcted tissue after MCAo exhibited increased conductivity. Further in-vivo experiments with examination of the influence of reperfusion status and temporal evolution of the infarcted areas should be conducted.

This paper presents a CFD model to predict the fluid flow, fluid temperature, load temperature and the theoretical inactivation of bacteria in a modern steam sterilizer, with three significant modifications compared to current state-of-the-art simulations of steam sterilizers. 1) The fluid and the load temperature was investigated for unwrapped load. Measurements of the fluid temperature and the load temperature were performed to validate the CFD model. The average error between the simulated and the measured temperatures was below 0.4 K. 2) The steam quality inside a steam sterilizer was investigated for unwrapped load. With the developed CFD model it is possible to predict the steam quality inside the steam sterilizer spatially and temporally resolved. 3) A first order reaction kinetic approach was added to the CFD model to predict the theoretical inactivation of two different types of bacteria in the steam sterilizer, as well as on the surface of the unwrapped load based on sterilization parameters. The results indicate that the CFD model is able to predict the theoretical inactivation of bacteria on the surface of the load, based on sterilization parameters.

Due to the advantages of rapid and non-invasive detection of traumatic dural hematoma using near-infrared differential optical density method, this technology has become a hot research topic in tissue optics in recent years and has important applications in clinical emergency treatment. To further improve the detection accuracy of traumatic subdural hematoma degree, in this paper, a multi-channel differential optical density method was used to obtain the bilaterally-symmetric optical density data of brain. A calibration model with the optical absorption coefficient of the brain tissue and the differential optical density was established using the partial least squares method to predict intracranial epidural hematoma. Simulation results show that the average relative error of the absorption coefficient of dural hematoma using the prediction model was 11.16% and the average relative error on hematoma depth prediction was less than 1%. The model meets the demands of noninvasive traumatic subdural hematoma degree detection. By introducing multi-channel differential optical density method into the noninvasive detection of subdural hematoma, the effects of individual differences on the detection result could be eliminated significantly and the detection accuracy of traumatic subdural hematoma degree can be improved.

Two different molecularly imprinted polymers (MIP) were designed to selectively bind the insecticides carbofuran (CBF) and profenofos (PFF). CBF-MIP are based on methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a crosslinker, and azobisisobutyronitrile (AIBN) as an initiator. The PFF-MIP comprised of polyurethane based on poly (4-vinylphenol) (PVP), and diphenyl methane-4,4′-di-isocyanate (DPDI) as functional monomers, phloroglucinol (PG) as the cross-linker, and diphenylmethane (DPM) as the porogen. For sensor measurement, MIPs were spin-coated onto one electrode pair of a dual-electrode QCM, while the second pair was spin-coated with NIPs. Fourier transform infrared (FT-IR) spectroscopy confirms successful template removal from the polymer matrix. The resulting CBF- and PFF-MIP coated onto quartz crystal microbalances (QCMs) lead to pesticide QCM sensors revealing the following analytical characteristics, respectively: dynamic detection range of 0.5–1000 μM for CBF-MIP and 10–1000 μM for PFF-MIP. In both cases, the MIP exhibit roughly ten times higher sensor signals, than the corresponding non-imprinted polymers (NIP).