Physics in Medicine最新文献

In a recent issue of Physics in Medicine, Akashi et al. demonstrated increased mortality of HeLa cells in combination with phospholipid-shelled microbubbles under high-amplitude sonication in an in-vitro experimental setup [1]. The authors attributed the increased mortality to cell damage caused by microbubble dynamics and mentioned the term sonoporation early in their paper. Their findings are a most valuable contribution with regards to ultrasonic imaging safety standards. However, the findings would be even more beneficial to the drug delivery community, provided they could be linked to previous outcomes on in-vitro experimental sonoporation. The purpose of this paper is to briefly underscore previous works with similar setups, highlighting the many agreements between early and recent work.

In this study, inactivation kinetics of Geobacillus stearothermophilus spores were evaluated in different sterilization environments. The kinetics were analysed and mathematically modelled based on experimental data collected. The inactivation kinetics were measured precisely in moist heat environments using different sterilization temperatures and holding times. All measured inactivation times were shorter than the inactivation time indicated by the Biological Indicator (BI) manufacturer. Increasing sterilization efficiency was found in the following environments: air, saturated steam, wet steam, liquid water, dialysis solutions. Applying first- and second-order reaction kinetics approaches, formulas were derived from measured data that enabled bacterial inactivation to be modelled. A mathematical first-order reaction kinetic modelling approach could be taken to effectively predict inactivation kinetics for G. stearothermophilus spores based on the experimentally measured data collected in wet steam and air environments. A second-order reaction kinetics approach could be taken, however, to model measured data more accurately in liquid water and dialysis-solution environments. The mathematical models presented here can be applied to describe inactivation kinetics for G. stearothermophilus spores in different sterilization test environments or for any given sterilization temperature profile. These findings can be used to improve the quality of sterilization processes.

Scientific efforts towards nerve regeneration and nerve-electrode interfaces depend on the possibility of guided neurite growth. The quantification and tracing of neurite growth during experiments is therefore essential. While tracing is possible under 2D cell culture conditions, it gets more complex when analysing three dimensionally orientated neurite pathways resulting in the ongoing development of 3D neuron tracing software. However, the quantification of short vertical neurite sprouts remains complicated due to difficult distinction from small cell body parts. With this study, we present a new method for precise identification and quantification of short neurite sprouts growing vertically from the surface of a track-etched membrane into 8 μm diameter pores of the membrane. Based on collected radius data from identified horizontally orientated neurites, a 95% reference interval for average radii of neurites was established and the limits were applied to trace neurite sprouts in the membrane's pores. Following this procedure, neurites were successfully distinguished from small cell body parts. This study demonstrates how to identify short neurite sprouts by assessing number, length, and radius with an additional checkpoint for bias detection.

Objectives

Without rotating instruments, for example diamond-coated drills with a core made of stainless steel, the dental routine would be unimaginable, since these are used in almost every dental activity and are thus indispensable for the professional practice. Unfortunately, such drills release Nickel particles to a high content into the cooling water of the drill. Values up to 1.3 mg/l Nickel were found by ICP – OES in the cooling water of the drillers which is of course also transferred into the patient's oral cavity with possible severe negative effects. Therefore, novel plating procedures have to be developed to increase the patients (and dentists) safety during treatment.

Methods

Dispersion layers with the hard metal Tungsten carbide (WC) particles on stainless steel blanks were deposited following two synthesis routines (i) Plasma-Electrolytic Oxidation (PEO) and (ii) galvanic plating out of a Watts bath. Both were accomplished using water-based electrolytes.

Results

In order to verify the dental applicability of the developed coatings, tests-drills were accomplished under defined conditions on plastic teeth for the sake of reproducibility.

Commercially produced drills were compared with the newly plated ones by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and the drilling cooling water was examined for heavy metal residues using Inductively Coupled Plasma (ICP) analytics. The resulting grinding patterns in the plastic teeth were investigated by light microscopy and SEM.

It could be shown that dispersion layers plated by a galvanic procedure showed a reduced Nickel release compared to a commercial driller by factor 7.6 and 13.4 compared to PEO plated ones during dental treatments.

Conclusions

Following the clinical significance the Watts bath plated drillers showed a better WC particle distribution on the surface and better abrasive properties during the drilling experiments compared to PEO plated drillers. In addition the Nickel release during dental use is much less from the galvanic treated ones. By optimising the plating condition from the Watts dispersion bath further novel drilling devices with significantly reduced release of Nickel particles can be developed for the benefit of the patients.

Drug delivery systems (DDS) using ultrasound and microbubbles have been proposed to enhance drug efficacy and reduce undesirable side effects. While several researchers have reported the vibrational characteristics of lipid-coated microbubbles under ultrasound irradiation and the effects on cell damage, it is necessary to quantitatively evaluate the effects to establish the safety criteria of ultrasound DDS. In this paper, the effects of the microbubble behavior on adhesive HeLa cells under ultrasound irradiation were evaluated. Microbubbles coated with a phospholipid shell were fabricated and two size distributions of bubbles were prepared. The HeLa cells were exposed to pulsed ultrasound at 1 MHz with microbubbles in a water tank, and the cell mortality rate was measured quantitatively under fluorescent observation. The collapse of the microbubbles with a resonance size of approximately 2 μm enhanced the cell mortality rate. Greater sound pressure amplitude produced a higher collapsing rate of the microbubble and cell mortality rate, implying the destruction of microbubbles with resonance size generated a shock wave or microjet, inducing cell damage. While the cell mortality rate decreased exponentially with the increase in distance between cells and microbubbles, a smaller distance induced a higher cell mortality rate: 84% of the HeLa cells died within 2.5 μm of microbubbles produced by a pulsed ultrasound with 1.0 MPa at 1 MHz.

The aim of this study was to develop a Computational Fluid Dynamics (CFD) model to simulate the inactivation of bacterial spores of Geobacillus stearothermophilus inside a Peritoneal Dialysis Bag System (PDBS). The presented CFD model has three significant modifications in comparison to current state-of-the-art simulations of sterilization processes. (i) The CFD simulation can be used to consider the multiphase flow (water, steam, different dialysis solutions, non-condensable gases (NCGS)) inside the PDBS, the natural convection as well as the steam penetration. (ii) Experimentally obtained inactivation kinetics were added to the CFD code to enable simulation of the inactivation of G. stearothermophilus spores. (iii) The inactivation process of G. stearothermophilus spores was simulated in different sterilization environments which are present inside a PDBS. The CFD model was verified with measurements using Biological Indicators (BIs). Results showed that on the pre-CFD-simulated “worst case locations” CFD simulations and the BI-based verification were in well accordance.

By using the presented CFD model, the simulation of a moist heat sterilization process can be performed for any given sterilization cycle. In addition, the model is a powerful tool that can be used to optimize steam sterilization processes and guarantee a high level of sterilization efficiency and product safety.

Objective

To propose a method to develop 3-dimensional (3D) models of regular and orthodontic typodonts by using their 2-dimensional (2D) images, as an alternate method to 3D scanners.

Materials and methods

The mandibles of two typodonts, regular occlusion and malocclusion, were scanned by using a 3D scanner to generate their models. Captured scans were used to determine the accuracy of the existing method. One hundred images of each mandible were made by using a smartphone from various angles five times to create required and generate 3D models through the software. The percentage overlap of the hard tissues of the scans and the models superimposed within the group (repeatability test), and with each other (accuracy test) gathered the proposed method's accuracy and precision. The data were analyzed by using the Student's t-test.

Results

Ten scans and ten models were overlapped among themselves and each other and evaluated. Repeatability test; significant overlap in scans for both mandibles (regular and maloccluded), and their 3D model's counterparts (P < 0.05, CI 95%). Accuracy tests; significant overlap between both methods for both mandibles (P < 0.05, CI 95%).

Conclusion

The 2D images were successfully used to model the teeth (both regular and maloccluded) non-invasively. The proposed method showed high reproducibility as well as accuracy when compared to a commercially available 3D scanner.

Clinical significance

The 3D models for both regular teeth and teeth with malocclusions were modeled by using 2D images taken with a smartphone by using the novel method which was both reproducible and accurate.

Background

With increasing application of Volumetric Modulated Arc Therapy (VMAT) and the complexity of treatment plans, necessity of patient-specific quality assurance procedures is raised. Therefore, this study aimed to perform VMAT plan control using the ArcCHECK® (Sun Nuclear) and the EPID (Electronic Portal Imaging Device) A-Si1000 and make a comparison.

Methods

The study was carried out at AL KAWTAR Oncology Center (Fez-Meknes/Morocco) with the TrueBeam^TM accelerator and Eclipse^TM Treatment Planning System (TPS). GeoGebra 6.0 and Origin 2019 software were applied to statistical analysis and to reconstruct the dose distribution maps for ArcCHECK® Phantom, respectively. Gamma index test with the 3%/3 and 2%/2 mm criteria applied to compare two pretreatment quality control instrumentation.

Results

Although the EPID A-Si1000 and the ArcCHECK® phantom both were capable of performing VMAT plan control, results of gamma index analysis revealed some differences in the quality of the reviewed plans with the two devices.

Conclusion

based on the results, a single device to implement patient QA for complex VMAT plans may not be reliable. Therefore, to ensure patient protection against machine or human errors, applying the EPID A-Si1000 and the ArcCHECK® phantom both are proposed to evaluate the quality of complex VMAT plans for different cancer types.

T₁ mapping is crucial for many quantitative magnetic resonance imaging (MRI) procedures. However, studies have reported wide T₁ variations, both in vivo and in vitro. Since clinical decisions depend on T₁ relaxation times, evaluating the factors affecting their reproducibility is necessary. Available studies are limited in that they do not provide a comparative perspective on the variation of T₁ relaxation times as a function of relevant parameters, such as pulse sequence type, magnetic field strength and how their interplay with the scanner model affects the resulting T₁ values. To address these gaps, we imaged two phantoms modelling T₁ of different samples at 1.5 T and 3.0 T using fast and slow inversion recovery (IR) sequences. The results show that T₁ relaxation times from 3.0 T scanners are accurate and reproducible in terms of the expected reference values and when compared between different scanner models. Similarly, T₁ values measured with the two pulse sequences were similar for all 3.0 T scanners. On the contrary, 1.5 T scanners exhibited larger discrepancies in the measured T₁ compared with the reference values. In addition, 1.5 T scanners displayed less reproducibility in T₁ relaxation time measurements across different 1.5 T scanners, and pulse sequences.

Little is known about the steam content in mixtures of steam and NCGs (Non-Condensable Gases), also referred to as steam-air mixtures, required for successful sterilization and about the contribution of additional liquid water in the sterilization chamber to this process. In this study, sterilization efficiency was assessed with Geobacillus stearothermophilus spores in different steam-NCGs mixtures and under different temperatures and holding times. For each experiment, water, air and bioindicators (BIs) were placed in a gas-tight metal box which then underwent one pre-defined sterilization cycle. The initial water amount, sterilization temperatures and holding times were varied. The volume fractions of steam were calculated by applying thermodynamic laws, and the steam distribution was simulated using Computational Fluid Dynamics (CFD). The inactivation of the BIs was represented as a function of different steam-NCG mixtures. The main finding is that the steam volume in the gas phase is of little importance, but the amount of liquid water available to wet BIs during sterilization is crucial. This study represents the first investigation on bacterial inactivation during the sterilization process in different steam-NCG mixtures using different amounts of liquid water. The previously unknown inactivation kinetics results may prove useful for developers and researchers and enhance medical safety.