Supported lipid bilayers (SLBs) are popular models of cell membranes with potential biotechnological applications, yet the mechanism of SLB formation is only partially understood. In this study, the adsorption and subsequent conformational changes of sonicated unilamellar vesicles on silica supports were investigated by quartz crystal microbalance with dissipation monitoring and atomic force microscopy, using mixtures of zwitterionic, negatively charged, and positively charged lipids, both in the presence and in the absence of Ca 2 + ions. Four different pathways of vesicle deposition could be distinguished. Depending on their charge, vesicles i), did not adsorb; ii), formed a stable vesicular layer; or iii), decomposed into an SLB after adsorption at high critical coverage or iv), at low coverage. Calcium was shown to enhance the tendency of SLB formation for negatively charged and zwitterionic vesicles. The role of vesicle-support, interbilayer, and intrabilayer interactions in the formation of SLBs is discussed.

Pathways of lipid vesicle deposition on solid surfaces: A combined QCM-D and AFM study

Here, we present two different brain diagnostic devices based on microwave technology and the associated two first proof-of-principle measurements that show that the systems can differentiate hemorrhagic from ischemic stroke in acute stroke patients, as well as differentiate hemorrhagic patients from healthy volunteers. The system was based on microwave scattering measurements with an antenna system worn on the head. Measurement data were analyzed with a machine-learning algorithm that is based on training using data from patients with a known condition. Computer tomography images were used as reference. The detection methodology was evaluated with the leave-one-out validation method combined with a Monte Carlo-based bootstrap step. The clinical motivation for this project is that ischemic stroke patients may receive acute thrombolytic treatment at hospitals, dramatically reducing or abolishing symptoms. A microwave system is suitable for prehospital use, and therefore has the potential to allow significantly earlier diagnosis and treatment than today.

https://publications.lib.chalmers.se/records/fulltext/207371/local_207371.pdf

Microwave-Based Stroke Diagnosis Making Global Prehospital Thrombolytic Treatment Possible

Widely used medical imaging systems in clinics currently rely on X-rays, magnetic resonance imaging, ultrasound, computed tomography, and positron emission tomography. The aforementioned technologies provide clinical data with a variety of resolution, implementation cost, and use complexity, where some of them rely on ionizing radiation. Microwave sensing and imaging (MSI) is an alternative method based on nonionizing electromagnetic (EM) signals operating over the frequency range covering hundreds of megahertz to tens of gigahertz. The advantages of using EM signals are low health risk, low cost implementation, low operational cost, ease of use, and user friendliness. Advancements made in microelectronics, material science, and embedded systems make it possible for miniaturization and integration into portable, handheld, mobile devices with networking capability. MSI has been used for tumor detection, blood clot/stroke detection, heart imaging, bone imaging, cancer detection, and localization of in-body RF sources. The fundamental notion of MSI is that it exploits the tissue-dependent dielectric contrast to reconstruct signals and images using radar-based or tomographic imaging techniques. This paper presents a comprehensive overview of the active MSI for various medical applications, for which the motivation, challenges, possible solutions, and future directions are discussed.

On the Opportunities and Challenges in Microwave Medical Sensing and Imaging

Hyperthermia therapy (HT) is the exposure of a region of the body to elevated temperatures to achieve a therapeutic effect. HT anticancer properties and its potential as a cancer treatment have been studied for decades. Techniques used to achieve a localised hyperthermic effect include radiofrequency, ultrasound, microwave, laser and magnetic nanoparticles (MNPs). The use of MNPs for therapeutic hyperthermia generation is known as magnetic hyperthermia therapy (MHT) and was first attempted as a cancer therapy in 1957. However, despite more recent advancements, MHT has still not become part of the standard of care for cancer treatment. Certain challenges, such as accurate thermometry within the tumour mass and precise tumour heating, preclude its widespread application as a treatment modality for cancer. MHT is especially attractive for the treatment of glioblastoma (GBM), the most common and aggressive primary brain cancer in adults, which has no cure. In this review, the application of MHT as a therapeutic modality for GBM will be discussed. Its therapeutic efficacy, technical details, and major experimental and clinical findings will be reviewed and analysed. Finally, current limitations, areas of improvement, and future directions will be discussed in depth.

Magnetic hyperthermia therapy for the treatment of glioblastoma: a review of the therapy's history, efficacy and application in humans.

Clinical trials have shown that hyperthermia (HT), i.e. an increase of tissue temperature to 39–44 °C, significantly enhance radiotherapy and chemotherapy effectiveness [1]. Driven by the developments in computational techniques and computing power, personalised hyperthermia treatment planning (HTP) has matured and has become a powerful tool for optimising treatment quality. Electromagnetic, ultrasound, and thermal simulations using realistic clinical set-ups are now being performed to achieve patient-specific treatment optimisation. In addition, extensive studies aimed to properly implement novel HT tools and techniques, and to assess the quality of HT, are becoming more common. In this paper, we review the simulation tools and techniques developed for clinical hyperthermia, and evaluate their current status on the path from ‘model’ to ‘clinic’. In addition, we illustrate the major techniques employed for validation and optimisation. HTP has become an essential tool for improvement, control, and ...

https://www.tandfonline.com/doi/pdf/10.3109/02656736.2013.790092

Simulation techniques in hyperthermia treatment planning

Microwave hyperthermia treatment planning (HTP) is a multi-objective task for which several cost functions have been suggested over the years. The power distribution inside the patient, achieved by amplitude and phase steering of the applicator array, must fulfill diverse requirements. On the one hand, high and homogeneous target power deposition is required for temperature elevation. On the other, healthy tissues should not be subjected to excessive heating and hot-spots outside the target should be suppressed. To these ends, two major SAR- based indicators are currently used as cost functions in clinical HTP, albeit with slightly different meanings: the HTQ and the TC. We propose a novel cost function, termed the hot-to-cold spot quotient (HCQ), aiming at simultaneous target coverage and hot-spot suppression. We show that the HCQ yields HTP solutions that represent a good compromise between the HTQ- and TC-optimal ones for two realistic cases in both single- and multi-frequency settings.

Combining target coverage and hot-spot suppression into one cost function: the hot-to-cold spot quotient

Asymmetric cationic liposomes designed for heat-activated association with cells.

TR-Hyperthermia system prototype: first phantom experiments

The evaluation of non-invasive microwave thermometry using a differential microwave imaging approach is investigated in an experimental setup. The setup consists of a monopole microwave tomographic system, a muscle phantom, and a circulation/heating system. The saline solution is used as the heated medium inside the muscle phantom. Based on Born Approximation and regularization by TSVD we reconstructed the distribution of both dielectric parameters, relative permittivity and electrical conductivity inside the investigation area. A promising agreement between measured and reconstructed electrical conductivity was achieved and some specifics for future improvement of microwave thermometry were identified.

Non-invasive Thermometry During Hyperthermia Using Differential Microwave Imaging Approach

In deep microwave hyperthermia (MW-HT), antenna arrays are used to generate an interference pattern which focuses energy in the tumor location. These arrays are subject to a number of disturbances which must be compensated for through calibration. This paper proposes and analyzes a pair of self-calibration algorithms, i.e. calibration procedures which rely only on S-matrix measurements of the N-port array applicator device, avoiding the need for external references and making real-time in-treatment calibration possible. Two algorithms are analyzed by means of simulations and experiments in terms of reliability and sensitivity to different kinds of disturbances. The results show that one of two implemented algorithms can converge to the same calibration values obtained when using an external calibration reference (monopole antenna).

/pdf/self-calibration-algorithms-for-microwave-hyperthermia-3we1biq3zb.pdf

Hana Dobsicek Trefna

Papers

Combining target coverage and hot-spot suppression into one cost function: the hot-to-cold spot quotient

Asymmetric cationic liposomes designed for heat-activated association with cells.

TR-Hyperthermia system prototype: first phantom experiments

Non-invasive Thermometry During Hyperthermia Using Differential Microwave Imaging Approach

Self-calibration algorithms for microwave hyperthermia antenna arrays