Respiratory challenge MRI: practical aspects

Respiratory challenge MRI is the modification of arterial oxygen (PaO2) and/or carbon dioxide (PaCO2) concentration to induce a change in cerebral function or metabolism which is then measured by MRI. Alterations in arterial gas concentrations can lead to profound changes in cerebral haemodynamics which can be studied using a variety of MRI sequences. Whilst such experiments may provide a wealth of information, conducting them can be complex and challenging. In this paper we review the rationale for respiratory challenge MRI including the effects of oxygen and carbon dioxide on the cerebral circulation. We also discuss the planning, equipment, monitoring and techniques that have been used to undertake these experiments. We finally propose some recommendations in this evolving area for conducting these experiments to enhance data quality and comparison between techniques

Oxygen challenge MRI: development of a novel technique and application to acute stroke patients

The treatment of hyperacute ischaemic stroke has been revolutionised by the concept of potentially salvageable tissue – the ‘ischaemic penumbra’. However, current therapeutic practice is to administer thrombolytic therapy with recombinant tissue plasminogen activator after exclusion of intra-cerebral haemorrhage, with ‘time since onset’ used as a surrogate marker for the presence or absence of the ischaemic penumbra. The ability to identify the penumbra on an individual basis would enable bespoke treatment plans on the basis of underlying pathophysiology. The most commonly employed penumbral image technique is multi-modal magnetic resonance imaging (MRI) to identify a region of perfusion-diffusion mismatch. However, this approach remains to be validated. Moreover, a systematic review presented as an appendix to this thesis highlights the marked heterogeneity for its application. This thesis focusses on the development of a novel MRI technique (Oxygen Challenge) and is the first to report findings from human acute ischaemic stroke. The rationale for this technique is that it is sensitive to deoxyhaemoglobin, which is produced as a consequence of oxidative metabolism. It therefore has the potential to discriminate tissue compartments based on metabolic activity. For this study, 35 subjects with acute ischaemic stroke were imaged with transient hyperoxia (Oxygen Challenge) applied during continuous T2*-weighted MRI. Exploratory analyses suggested the following; •Oxygen Challenge precipitates a T2*-weighted signal increase in healthy tissue •This signal increase is partly dependent on the underlying cerebral blood volume, as suggested by univariate and multivariate analyses •In general, higher concentrations of oxygen precipitate greater T2*-weighted signal increases, but oxygen may influence T2*-weighted signal intensity in a bi-modal manner •The signal changes in operationally defined infarct core are attenuated, suggesting a metabolic influence on Oxygen Challenge results •Signal increases in the hyperacute perfusion-diffusion mismatch region were sometimes exaggerated, consistent with increased oxygen extraction fraction. However, small volumes of tissue acquired from only a few subjects limited definitive conclusions in this study •Oxygen Challenge may detect regions of crossed cerebellar diaschsis, although further confirmation is required •Maps of ‘percentage signal change’ allowed rapid evaluation of whole brain Oxygen Challenge data •Improvements in signal-to-noise ratio are required before this technique can be applied in clinical practice. On the basis of these data it is concluded that the technique is encouraging and further validation is warranted

Effect of Punarnavadi Mandoor and Shiva Gutika in Acute Deep Vein Thrombosis - A Case Report

Objectives: To minimise the dose of Anti-platelet drugs and to treat the acute case of DVT through Ayurvedic oral medications. Methods: The present diagnosed case of DVT approached to OPD of KLE BMK Ayurveda Hospital with a complaints of swelling and pain in the calf muscle of the left lower limb associated with reddish brown discoloration in the foot and occasionally nasal and gum bleeding was treated consequently for 5 months with Punarnavadi Mandoor and Shiva Gutika orally. Results: There is significant decrease in the symptoms of DVT and also major changes seen in Venous Colour Doppler study of the left lower limb. Conclusion: Acute DVT is caused by a blood clot in a deep vein and can be life threatening as it may leads to serious complication like pulmonary embolism which can be cured through Ayurvedic oral medications

Vasoreactivity in CADASIL: comparison to structural MRI and neuropsychology

Impaired cerebrovascular reactivity precedes histological and clinical evidence of CADASIL in animal models. We aimed to more fully characterise peripheral and cerebral vascular function and reactivity in a cohort of adult CADASIL patients, and explore the associations of these with conventional clinical, imaging and neuropsychological measures. 22 adults with CADASIL gave informed consent to participate in an exploratorystudy of vascular function in CADASIL. Clinical assessment, comprehensive vascular assessment, MRI and neuropsychological testing were conducted. Transcranial Doppler and arterial spin labelling MRI with hypercapnia challenge both measured cerebral vasoreactivity. Number and volume of lacunes, subcortical hyperintensity volume, microbleeds and normalised brain volume were assessed on MRI scans. Analysis was exploratory and examined associations between different markers. The results showed that cerebrovascular reactivity measured by ASL correlated with peripheral vasoreactivity measured by flow mediated dilatation. Subjects with >5 lacunes were older, with evidence of atherosclerosis and had impaired cerebral and peripheral vasoreactivity. Subjects with depressive symptoms, disability or delayed processing speed, also had impaired vasoreactivity, as well as more lacunes and brain atrophy. Impaired vasoreactivity and vascular dysfunction may play a significant role in the pathophysiology of CADASIL and vascular tests may be important to include in both longitudinal and clinical trials

Desain Eksperimen TUF Dalam Peningkatan Kualitas Garam Olahan Limbah Produksi Es dengan Metode Taguchi di PT. Putra Maesa Persada

Indonesia has salt resources in seawater along the Java Sea coast. However, the high salt content in seawater causes difficulties for various industries that use seawater as their raw material. A Taguchi experimental design using TUF filters was carried out to determine the best TUF filter composition in producing high-quality salt. The factors considered were the compositions of three materials, namely crushed coral, charcoal, and palm fibers. The results obtained for the sample filters were analyzed using one-way ANOVA, Minitab, and the Signal-to-Noise Ratio (SNR) method. The optimal TUF filter composition was found to be 450g finely crushed coral, 350g finely crushed charcoal, and 30g palm fibers. The study results revealed that the best factor for improving salt quality was crushed coral, with a contribution of 65.63842% and an F-value of 109.3333. Charcoal also provided a significant contribution of 24.40453% with an F-value of 40.65041. However, palm fibers did not contribute significantly to improving salt quality. The optimal TUF filter composition can help improve salt quality and increase productivity while reducing costs for various industries such as food production and preservation. The optimal composition of 450g of crushed coral, 350g of charcoal, and 30g of palm fibers can significantly improve the quality of salt production. In conclusion, the use of TUF filters with the optimal composition of 450g crushed coral, 350g charcoal, and 30g palm fibers can significantly improve salt quality. This study provides insight into the potential applications of TUF filters and should encourage further exploration of the technology's potential in various industries

Scabies

https://digitalcommons.imsa.edu/hd_graphic_novels/1019/thumbnail.jp

Melanoma

https://digitalcommons.imsa.edu/hd_graphic_novels/1025/thumbnail.jp

Improving Signal and Photobleaching Characteristics of Temporal Focusing Microscopy with the Increase in Pulse Repetition Rate

Wide-field temporal focused (WF-TeFo) two-photon microscopy allows for the simultaneous imaging of a large planar area, with a potential order of magnitude enhancement in the speed of volumetric imaging. To date, low repetition rate laser sources with over half a millijoule per pulse have been required in order to provide the high peak power densities for effective two-photon excitation over the large area. However, this configuration suffers from reduced signal intensity due to the low repetition rate, saturation effects due to increased excitation fluences, as well as faster photobleaching of the fluorescence probe. In contrast, with the recent advent of high repetition rate, high pulse energy laser systems could potentially provide the advantages of high repetition rate systems that are seen in traditional two-photon microscopes, while minimizing the negatives of high fluences in WF-TeFo setups to date. Here, we use a 100 microjoule/high repetition rate (50-100 kHz) laser system to investigate the performance of a WF-TeFo two-photon microscope. While using micro-beads as a sample, we demonstrate a proportionate increase in signal intensity with repetition rate, at no added cost in photobleaching. By decreasing pulse intensity, via a corresponding increase in repetition rate to maintain fluorescence signal intensity, we find that the photobleaching rate is reduced by ~98.4%. We then image live C. elegans at a high repetition rate for 25 min. as a proof-of-principle. Lastly, we identify the steady state temperature increase as the limiting process in further increasing the repetition rate, and we estimate that repetition rate in the range between 0.5 and 5 MHz is ideal for live imaging with a simple theoretical model. With new generation low-cost fiber laser systems offering high pulse energy/high repetition rates in what is essentially a turn-key solution, we anticipate increased adoption of this microscopy technique by the neuroscience community

Oxygen challenge magnetic resonance imaging in healthy human volunteers

Oxygen challenge imaging involves transient hyperoxia applied during deoxyhaemoglobin sensitive (T2*-weighted) magnetic resonance imaging and has the potential to detect changes in brain oxygen extraction. In order to develop optimal practical protocols for oxygen challenge imaging, we investigated the influence of oxygen concentration, cerebral blood flow change, pattern of oxygen administration and field strength on T2*-weighted signal. Eight healthy volunteers underwent multi-parametric magnetic resonance imaging including oxygen challenge imaging and arterial spin labelling using two oxygen concentrations (target FiO2 of 100 and 60%) administered consecutively (two-stage challenge) at both 1.5T and 3T. There was a greater signal increase in grey matter compared to white matter during oxygen challenge (p < 0.002 at 3T, P < 0.0001 at 1.5T) and at FiO2 = 100% compared to FiO2 = 60% in grey matter at both field strengths (p < 0.02) and in white matter at 3T only (p = 0.0314). Differences in the magnitude of signal change between 1.5T and 3T did not reach statistical significance. Reduction of T2*-weighted signal to below baseline, after hyperoxia withdrawal, confounded interpretation of two-stage oxygen challenge imaging. Reductions in cerebral blood flow did not obscure the T2*-weighted signal increases. In conclusion, the optimal protocol for further study should utilise target FiO2 = 100% during a single oxygen challenge. Imaging at both 1.5T and 3T is clinically feasible

Mimicking subsecond neurotransmitter dynamics with femtosecond laser stimulated nanosystems

Existing nanoscale chemical delivery systems target diseased cells over long, sustained periods of time, typically through one-time, destructive triggering. Future directions lie in the development of fast and robust techniques capable of reproducing the pulsatile chemical activity of living organisms, thereby allowing us to mimic biofunctionality. Here, we demonstrate that by applying programmed femtosecond laser pulses to robust, nanoscale liposome structures containing dopamine, we achieve sub-second, controlled release of dopamine – a key neurotransmitter of the central nervous system – thereby replicating its release profile in the brain. The fast delivery system provides a powerful new interface with neural circuits and to the larger range of biological functions that operate on this short timescale