Intracranial Arterial 4D Flow in Individuals with Mild Cognitive Impairment is Associated with Cognitive Performance and Amyloid Positivity

It is becoming increasingly recognized that cerebrovascular disease is a contributing factor in the pathogenesis of Alzheimer’s disease (AD). A unique 4D-Flow magnetic resonance imaging (MRI) technique, phase contrast vastly undersampled isotropic projection imaging (PC VIPR), enables examination of angiographic and quantitative metrics of blood flow in the arteries of the Circle of Willis within a single MRI acquisition. Thirty-eight participants with mild cognitive impairment (MCI) underwent a comprehensive neuroimaging protocol (including 4D-Flow imaging) and a standard neuropsychological battery. A subset of participants (n = 22) also underwent lumbar puncture and had cerebrospinal fluid (CSF) assayed for AD biomarkers. Cut-offs for biomarker positivity in CSF resulting from a receiver operating characteristic curve analysis of AD cases and controls from the larger Wisconsin Alzheimer’s Disease Research Center cohort were used to classify MCI participants as biomarker positive or negative on amyloid-β (Aβ42), total-tau and total-tau/Aβ42 ratio. Internal carotid artery (ICA) and middle cerebral artery (MCA) mean flow were associated with executive functioning performance, with lower mean flow corresponding to worse performance. MCI participants who were biomarker positive for Aβ42 had lower ICA mean flow than did those who were Aβ42 negative. In sum, mean ICA and MCA arterial flow was associated with cognitive performance in participants with MCI and lower flow in the ICA was associated with amyloid positivity. This provides further evidence for vascular health as a contributing factor in the etiopathogenesis of AD, and could represent a point to intervene in the disease process

Rapid MR elastography of the liver for subsecond stiffness sampling

PURPOSE: Depicting the stiffness of biological soft tissues, MR elastography (MRE) has a wide range of diagnostic applications. The purpose of this study was to improve the temporal resolution of 2D hepatic MRE in order to provide more rapid feedback on the quality of the wavefield and ensure better temporal sampling of respiration-induced stiffness changes. METHODS: We developed a rapid MRE sequence that uses 2D segmented gradient-echo spiral readout to encode 40 Hz harmonic vibrations and generate stiffness maps within 625 ms. We demonstrate the use of this technique as a rapid test for shear wave amplitudes and overall MRE image quality and as a method for monitoring respiration-induced stiffness changes in the liver in comparison to 3D MRE and ultrasound-based time-harmonic elastography. RESULTS: Subsecond MRE allowed monitoring of increasing shear wave amplitudes in the liver with increasing levels of external stimulation within a single breath-hold. Furthermore, the technique detected respiration-induced changes in liver stiffness with peak values (1.83 ± 0.22 m/s) at end-inspiration, followed by softer values during forced abdominal pressure (1.60 ± 0.22 m/s) and end-expiration (1.49 ± 0.22 m/s). The effects of inspiration and expiration were confirmed by time-harmonic elastography. CONCLUSION: Our results suggest that subsecond MRE of the liver is useful for checking MRE driver settings and monitoring breathing-induced changes in liver stiffness in near real time

Off-Resonance Behaviour of RARE and TrueFISP in Imaging of Hyperpolarized 13C

Imaging of hyperpolarized 13C has recently gained interest for metabolic imaging. In comparison with 1H imaging, the signal of hyperpolarized substances cannot build up a steady state during an imaging sequence as it decays irreversibly to its thermal equilibrium value. Therefore, TrueFISP (FIESTA, balanced SSFP, b-FFE) and single-shot RARE (TSE, FSE) show comparable signal behaviour for on-resonance signal. However, TrueFISP images of hyperpolarized substances suffer in general from off-resonance signal in contrast to RARE. We demonstrate that due to off-resonance effects, TrueFISP has no advantage in comparison with RARE when hyperpolarized substances are imaged

Korrektur von Trajektorienfehlern bei radialer Bildgebung

In schnellen, radialen Akquisitionen führen Gradientenanisotropien zu Fehlern in der Trajektorie und somit zu Artefakten. Hier wird eine simple Methode zur Korrektur der Trajektorie oder in der Rekonstruktion diskutiert und für eine radiale 3D Sequenz an Phantomen demonstriert

Reproductive biology of the electric lanternfish Electrona risso (Myctophidae) and the bigscale fishes Melamphaes polylepis and Scopelogadus mizolepis (Melamphaidae)

This study was the first to investigate the key reproductive traits of the electric lantern fish Electrona risso (Myctophidae, n = 918) and the bigscale fishes (Melamphaidae) Melamphaes polylepis (n = 260) and Scopelogadus mizolepis (n = 649). Specimens of these mesopelagic species were collected in March and April 2015 in the eastern Central Atlantic (0–24° N, 20–26° W). Sex ratio was not significantly different from 1:1 in E. risso and M. polylepis but significantly skewed toward female dominance in S. mizolepis. Reproductive phases were determined macroscopically and by histological analyses on selected individuals. Female length at 50% maturity (L50) was 55.1 mm standard length (LS) in E. risso, with an observed female maximum length (Lmax) of 81.2 mm LS. M. polylepis females had an L50 of 40.2 mm LS and an Lmax of 86.7 mm LS. S. mizolepis had an L50 of 46 mm LS and an Lmax of 97.9 mm LS. The three species show histological features of iteroparity, but the E. risso population appears to occur in two year-classes and experience only one spawning season per lifetime in the study region. All three species are batch-spawners. A batch fecundity of 2668 eggs was estimated from one E. risso individual, with a relative batch fecundity of 369 eggs g−1 gonad-free body mass. M. polylepis had a batch fecundity of 1027 eggs and a relative batch fecundity of 149 eggs g−1 (n = 3). S. polylepis had a batch fecundity of 1545 eggs and a relative batch fecundity of 215 eggs g−1 (n = 21). The median gonado-somatic index during the actively spawning phase of E. risso was 4.5, significantly lower than that of M. polylepis (7.5) and S. mizolepis (7.1). No regressing or regenerating phases were observed in this study. Batch-spawning in all three species is suggested to be advantageous to cope with intra-annual variability in food supply and other risks for offspring survival. With what appears to be in effect a (facultative) semelparous strategy in combination with a short life span in E. risso, interannual differences would have a great effect on population dynamics of this species. Knowledge is still lacking on temporal aspects of reproduction such as the duration of the spawning season and the frequency of spawning, as well as age and growth

Reproductive data of Electrona risso, Melamphaes polylepis and Scopelogadus mizolepis from the Eastern Central Atlantic in March and April 2015

Knowledge on life history traits of mesopelagic fishes is still sparse. This dataset contains reproductive data of the myctophid Electrona risso (Cocco, 1829) and the melamphaids Melamphaes polylepis Ebeling, 1962 and Scopelogadus mizolepis (Günther, 1878). The specimens were collected in March and April 2015 during cruise 383 of the fishery research vessel "FFS Walther Herwig III" in the Eastern Central Atlantic. A pelagic midwater trawl ("Aalnet", Engel Netze, Bremerhaven Germany) with multiple opening-closing device with three net bags of 20 mm mesh size and 1.8 mm mesh size in the cod-end container was used for catching fish at three depth strata per station between 50 and 700 m depth. Fish was stored in phosphate buffered 4% formalin solution and later on land in laboratories, specimens were measured, weighed, and dissected to examine gonads and oocytes under a stereo microscope. Reproductive phases were assigned based on macroscopic inspection following the standardised terminology for reproductive development in fish by Brown-Peterson et al. (2011, doi:10.1080/19425120.2011.555724). Histological cross sections of selected individuals were used for validation. The Gonadosomatic Index was calculated as GSI = 100 x gonad mass / (total mass – gonad mass). Batch fecundities were determined with the gravimetric method, counting the most advanced eggs in weighed subsamples