16 research outputs found
Accelerated Motion Correction with Deep Generative Diffusion Models
Magnetic Resonance Imaging (MRI) is a powerful medical imaging modality, but
unfortunately suffers from long scan times which, aside from increasing
operational costs, can lead to image artifacts due to patient motion. Motion
during the acquisition leads to inconsistencies in measured data that manifest
as blurring and ghosting if unaccounted for in the image reconstruction
process. Various deep learning based reconstruction techniques have been
proposed which decrease scan time by reducing the number of measurements needed
for a high fidelity reconstructed image. Additionally, deep learning has been
used to correct motion using end-to-end techniques. This, however, increases
susceptibility to distribution shifts at test time (sampling pattern, motion
level). In this work we propose a framework for jointly reconstructing highly
sub-sampled MRI data while estimating patient motion using diffusion based
generative models. Our method does not make specific assumptions on the
sampling trajectory or motion pattern at training time and thus can be flexibly
applied to various types of measurement models and patient motion. We
demonstrate our framework on retrospectively accelerated 2D brain MRI corrupted
by rigid motion
Conditional Score-Based Reconstructions for Multi-contrast MRI
Magnetic resonance imaging (MRI) exam protocols consist of multiple
contrast-weighted images of the same anatomy to emphasize different tissue
properties. Due to the long acquisition times required to collect fully sampled
k-space measurements, it is common to only collect a fraction of k-space for
some, or all, of the scans and subsequently solve an inverse problem for each
contrast to recover the desired image from sub-sampled measurements. Recently,
there has been a push to further accelerate MRI exams using data-driven priors,
and generative models in particular, to regularize the ill-posed inverse
problem of image reconstruction. These methods have shown promising
improvements over classical methods. However, many of the approaches neglect
the multi-contrast nature of clinical MRI exams and treat each scan as an
independent reconstruction. In this work we show that by learning a joint
Bayesian prior over multi-contrast data with a score-based generative model we
are able to leverage the underlying structure between multi-contrast images and
thus improve image reconstruction fidelity over generative models that only
reconstruct images of a single contrast
Stakeholder involvement in systematic reviews: a protocol for a systematic review of methods, outcomes and effects
Background
There is an expectation for stakeholders (including patients, the public, health professionals, and others) to be involved in research. Researchers are increasingly recognising that it is good practice to involve stakeholders in systematic reviews. There is currently a lack of evidence about (A) how to do this and (B) the effects, or impact, of such involvement. We aim to create a map of the evidence relating to stakeholder involvement in systematic reviews, and use this evidence to address the two points above.
Methods
We will complete a mixed-method synthesis of the evidence, first completing a scoping review to create a broad map of evidence relating to stakeholder involvement in systematic reviews, and secondly completing two contingent syntheses. We will use a stepwise approach to searching; the initial step will include comprehensive searches of electronic databases, including CENTRAL, AMED, Embase, Medline, Cinahl and other databases, supplemented with pre-defined hand-searching and contacting authors. Two reviewers will undertake each review task (i.e., screening, data extraction) using standard systematic review processes.
For the scoping review, we will include any paper, regardless of publication status or study design, which investigates, reports or discusses involvement in a systematic review. Included papers will be summarised within structured tables. Criteria for judging the focus and comprehensiveness of the description of methods of involvement will be applied, informing which papers are included within the two contingent syntheses.
Synthesis A will detail the methods that have been used to involve stakeholders in systematic reviews. Papers from the scoping review that are judged to provide an adequate description of methods or approaches will be included. Details of the methods of involvement will be extracted from included papers using pre-defined headings, presented in tables and described narratively.
Synthesis B will include studies that explore the effect of stakeholder involvement on the quality, relevance or impact of a systematic review, as identified from the scoping review. Study quality will be appraised, data extracted and synthesised within tables.
Discussion
This review should help researchers select, improve and evaluate methods of involving stakeholders in systematic reviews. Review findings will contribute to Cochrane training resources
Chronic Low-Level Vagus Nerve Stimulation Improves Long-Term Survival in Salt-Sensitive Hypertensive Rats
Chronic hypertension (HTN) affects more than 1 billion people worldwide, and is associated with an increased risk of cardiovascular disease. Despite decades of promising research, effective treatment of HTN remains challenging. This work investigates vagus nerve stimulation (VNS) as a novel, device-based therapy for HTN treatment, and specifically evaluates its effects on long-term survival and HTN-associated adverse effects. HTN was induced in Dahl salt-sensitive rats using a high-salt diet, and the rats were randomly divided into two groups: VNS (n = 9) and Sham (n = 8), which were implanted with functional or non-functional VNS stimulators, respectively. Acute and chronic effects of VNS therapy were evaluated through continuous monitoring of blood pressure (BP) and ECG via telemetry devices. Autonomic tone was quantified using heart rate (HR), HR variability (HRV) and baroreflex sensitivity (BRS) analysis. Structural cardiac changes were quantified through gross morphology and histology studies. VNS significantly improved the long-term survival of hypertensive rats, increasing median event-free survival by 78% in comparison to Sham rats. Acutely, VNS improved autonomic balance by significantly increasing HRV during stimulation, which may lead to beneficial chronic effects of VNS therapy. Chronic VNS therapy slowed the progression of HTN through an attenuation of SBP and by preserving HRV. Finally, VNS significantly altered cardiac structure, increasing heart weight, but did not alter the amount of fibrosis in the hypertensive hearts. These results suggest that VNS has the potential to improve outcomes in subjects with severe HTN