Publications by authors named "Jespersen S"

Unlabelled: Evaluating tissue microstructure and membrane integrity in the living human brain through diffusion-water exchange imaging is challenging due to requirements for a high signal-to-noise ratio and short diffusion times dictated by relatively fast exchange processes. The goal of this work was to demonstrate the feasibility of imaging of tissue micro-geometries and water exchange within the brain gray matter using the state-of-the-art Connectome 2.0 scanner equipped with an ultra-high-performance gradient system (maximum gradient strength=500 mT/m, maximum slew rate=600 T/m/s).

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Purpose: The purpose of this study is to develop a method for selecting uniform wave vectors for double diffusion encoding (DDE) to improve the accuracy and reliability of diffusion measurements.

Methods: The method relies on identifying orthogonal wave vectors with rotations, and representing these rotations as points on a three-dimensional sphere in four dimensions using quaternions. This enables an electrostatic repulsion algorithm to achieve a uniform distribution of these points.

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Article Synopsis
  • A 37-year-old woman was hospitalized with fever and muscle pain after returning from Mauritius.
  • She developed severe respiratory and circulatory failure shortly after receiving intravenous ceftriaxone, with anaphylaxis and pulmonary embolism being ruled out.
  • Ultimately, she tested positive for leptospirosis, and her critical condition was attributed to a Jarisch-Herxheimer reaction.
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Magnetic susceptibility imaging may provide valuable information about chemical composition and microstructural organization of tissue. However, its estimation from the MRI signal phase is particularly difficult as it is sensitive to magnetic tissue properties ranging from the molecular to the macroscopic scale. The MRI Larmor frequency shift measured in white matter (WM) tissue depends on the myelinated axons and other magnetizable sources such as iron-filled ferritin.

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Purpura fulminans (PF) is a life-threatening complication of septic shock that can occur due to disseminated infections with The spleen is an important organ in the immunisation process against encapsulated bacteria. Patients with asplenia, either functional or anatomical, are therefore at increased risk of developing serious infections and complications, such as PF, if infected with such bacteria.This case report presents a woman in her late 40s with unacknowledged functional asplenia who was admitted to the hospital with signs of an acute disseminated infection causing septic shock, signs of disseminated intravascular coagulation and infectious PF.

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Study Design: retrospective cohort study of prospectively collected data.

Objective: The treatment guidelines for thoracolumbar spinal fractures are controversial although minimally invasive surgery (MIS) is a popular alternative to the traditional open approach (TOA). Limited data exists about outcomes after MIS fracture treatment.

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Objectives: Disease progression, loss to follow-up, and mortality of HIV-2 compared with HIV-1 in children is not well understood. This is the first nationwide study reporting outcomes in children with the two HIV types in Guinea-Bissau.

Study Design: Nationwide retrospective follow-up study.

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Purpose: To extend quantitative susceptibility mapping to account for microstructure of white matter (WM) and demonstrate its effect on ex vivo mouse brain at 16.4T.

Theory And Methods: Previous studies have shown that the MRI measured Larmor frequency also depends on local magnetic microstructure at the mesoscopic scale.

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Cutaneous larva migrans is a common disease in the tropics and among travelers. The itchy, serpentigious rash often appears within days to weeks after transmission. There are only few reported cases of late relapses.

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Purpose: X-nuclei (also called non-proton MRI) MRI and spectroscopy are limited by the intrinsic low SNR as compared to conventional proton imaging. Clinical translation of x-nuclei examination warrants the need of a robust and versatile tool improving image quality for diagnostic use. In this work, we compare a novel denoising method with fewer inputs to the current state-of-the-art denoising method.

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Objective: AIDS-defining illness develops at higher CD4 + T-cell counts in individuals infected with HIV-2 compared with HIV-1-infected, which suggests that the two types of HIV may have different effects on other compartments of the immune system. We here investigate monocyte phenotype, activation and macrophage-derived extracellular vesicles in individuals with different HIV types.

Design: Cross-sectional.

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Background: The global prevalence of chronic hepatitis B is more than 300 million people, and in Denmark, 17,000 people are estimated to have chronic hepatitis B. Untreated, chronic hepatitis B can lead to the development of liver cirrhosis and liver cancer. There is no curable therapy.

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Background & Aim: For older adults, the dietary protein intake has shown to be skewed towards the evening meal. Resultingly, the vital source of essential amino acids could be insufficient after some meals, while after the evening meal the dietary protein could be suboptimally utilized for protein synthesis. The present study explored if an even distribution of the protein intake could improve the dietary amino acid absorption and whole-body protein net-balance.

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MP-PCA denoising has become the method of choice for denoising MRI data since it provides an objective threshold to separate the signal components from unwanted thermal noise components. In rodents, thermal noise in the coils is an important source of noise that can reduce the accuracy of activation mapping in fMRI. Further confounding this problem, vendor data often contains zero-filling and other post-processing steps that may violate MP-PCA assumptions.

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Purpose: Estimating magnetic susceptibility using MRI depends on inverting a forward relationship between the susceptibility and measured Larmor frequency. However, an often-overlooked constraint in susceptibility fitting is that the Larmor frequency is only measured inside the sample, and after successful background field removal, susceptibility sources should only reside inside the same sample. Here, we test the impact of accounting for these constraints in susceptibility fitting.

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Objective: In the 2020 UNAIDS HIV treatment goals, 90% of people living with HIV (PLHIV) should be diagnosed, 90% of these should receive antiretroviral treatment (ART) and 90% of these should be virally suppressed. We aimed to evaluate whether Guinea-Bissau fulfills the 2020 treatment goals for both for HIV-1 and HIV-2.

Design: By combining data from a general population survey, treatment records from HIV clinics across Guinea-Bissau and a biobank from patients attending the largest HIV clinics in Bissau, we estimated each column of the 90-90-90 cascade.

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Sarcopenia is a multifactorial disease that limits autonomy for the growing elderly population. An optimal amount of dietary protein has shown to be important to maintain muscle mass during aging. Yet, the optimal distribution of that dietary protein has not been fully clarified.

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The magnetic susceptibility of tissue can provide valuable information about its chemical composition and microstructural organization. However, the relation between the magnetic microstructure and the measurable Larmor frequency shift is understood only for a few idealized cases. Here we analyze the microstructure formed by magnetized, NMR-invisible infinite cylinders suspended in an NMR-reporting fluid.

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Purpose: To develop a denoising strategy leveraging redundancy in high-dimensional data.

Theory And Methods: The SNR fundamentally limits the information accessible by MRI. This limitation has been addressed by a host of denoising techniques, recently including the so-called MPPCA: principal component analysis of the signal followed by automated rank estimation, exploiting the Marchenko-Pastur distribution of noise singular values.

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This study aimed to investigate psychological distress among patients hospitalized with a COVID-19 diagnosis in Denmark during the first 12 months of the pandemic and to assess changes in psychological distress in the three months following discharge. A single-center prospective observational survey study among patients hospitalized with a COVID-19 diagnosis between May 2020 and May 2021 was conducted. Participants completed a survey at three time points: at admission, and 1 and 3 months after discharge.

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Objectives: In low-income countries with poor SARS-CoV-2 monitoring and high HIV burden, the prevalence of SARS-CoV-2 is scarcely studied in people living with HIV (PLWH). We set out to measure SARS-CoV-2 seroprevalence in this group.

Study Design: Serosurvey of SARS-CoV-2 in PLWH.

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Aims: Little is known about automated external defibrillator (AED) functionality in real-life settings. We aimed to assess the functionality of all registered AEDs in a geographically selected area and calculate the proportion of historical out-of-hospital cardiac arrests (OHCAs) covered by non-functioning AEDs.

Methods: In this cross-sectional study we inspected all registered and available AEDs on the island of Bornholm in Denmark.

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