Abstract The intravoxel incoherent motion (IVIM) theory provides a framework for the separation of perfusion and diffusion effects in diffusion-weighted imaging (DWI). To measure the three free IVIM ...parameters, DWIs with several diffusion weightings b must be acquired. To date, the used b value distributions are chosen heuristically and vary greatly among researchers. In this work, optimal b value distributions for the three parameter fit are determined using Monte-Carlo simulations for the measurement of a low, medium and high IVIM perfusion regime. The first 16 b values of a b value distribution, which was optimized to be appropriate for all three regimes, are {0, 40, 1000, 240, 10, 750, 90, 390, 170, 10, 620, 210, 100, 0, 530 and 970} in units of seconds per square meter. This distribution performed well for all organs and outperformed a distribution frequently used in the literature. In case of limited acquisition time, the b values should be chosen in the given order, but at least 10 b values should be used for current clinical settings. The overall parameter estimation quality depends strongly and nonlinearly on the signal-to-noise ratio (SNR): it is essential that the SNR is considerably higher than a critical SNR. This critical SNR is about 8 for medium and high IVIM perfusion and 50 for the low IVIM perfusion regime. Initial in vivo IVIM measurements were performed in the abdomen and were in keeping with the numerically simulated results.
We present a deep learning method for the segmentation of new lesions in longitudinal FLAIR MRI sequences acquired at two different time points. In our approach, the 3D volumes are processed ...slice-wise across the coronal, axial, and sagittal planes and the predictions from the three orientations are merged using an optimized voting strategy. Our method achieved best F1 score (0.541) among all participating methods in the MICCAI 2021 challenge
Multiple sclerosis new lesions segmentation
(MSSEG-2). Moreover, we show that our method is on par with the challenge's expert neuroradiologists: on an unbiased ground truth, our method achieves results comparable to those of the four experts in terms of detection (F1 score) and segmentation accuracy (Dice score).
Abstract Purpose The objective of this work was to evaluate the diagnostic performance of the intravoxel incoherent motion (IVIM) model to differentiate between healthy and malignant prostate tissue. ...Materials and Methods Regions of interest were drawn in healthy and cancerous tissue of 13 patients with histologically proven prostate carcinoma and fitted to a monoexponential model yielding the apparent diffusion coefficient (ADC) and the IVIM signal equation (yielding the perfusion fraction f , the diffusion constant D and the pseudodiffusion coefficient of perfusion D⁎ ). Parameter maps were calculated for all parameters. Results The ADC, D and f were significantly ( P <.005) lowered in cancerous tissue (1.01±0.22 μm2 /ms, 0.84±0.19 μm2 /ms and 14.27±7.10%, respectively) compared to benign tissue (1.49±0.17 μm2 /ms, 1.21±0.22 μm2 /ms and 21.25±8.32%, respectively). Parameter maps of D and f allowed for a delineation of the tumor, but showed higher variations compared to the ADC map. Conclusion Apparent diffusion coefficient maps provide better diagnostic performance than IVIM maps for tumor detection. However, the results suggest that the reduction of the ADC in prostate cancer stems not only from changes in cellularity but also from perfusion effects. IVIM imaging might hold promise for the diagnosis of other prostatic lesions.
Did King Alfred the Great commission the Old English translation of Bede’s Historia Ecclesiastica Gentis Anglorum, probably the masterpiece of medieval Anglo-Latin Literature, as part of his famous ...program of translation to educate the Anglo-Saxons? Was the Old English Historia, by any chance, a political and religious manifesto for the emerging ‘Kingdom of the Anglo-Saxons’? Do we deal with the literary cornerstone of a nascent English identity at a time when the Anglo-Saxon kingdoms were threatened by a common enemy: the Vikings? Andreas Lemke seeks to answer these questions – among others – in his recent publication. He presents us with a unique compendium of interdisciplinary approaches to the subject and sheds new light on the Old English translation of the Historia in a way that will fascinate scholars of Literature, Language, Philology and History.
Entstand die altenglische Übersetzung der Historia Ecclesiastica Gentis Anglorum des Beda Venerabilis, des wohl bedeutendsten anglo-lateinischen Werkes des Mittelalters, auf Bestreben König Alfreds ‚des Großen‘ als Teil seines Übersetzungs- und Bildungsprogrammes? War die altenglische Historia vielleicht ein Gründungsmanifest des Königreichs der Angelsachsen? Dieses Königreich formierte sich schließlich in einer Zeit, als England sich eines äußeren Feindes zu erwehren hatte, der die politische Ordnung der angelsächsischen Königreiche bedrohte: der Wikinger. Um diese Frage zu beantworten, präsentiert Andreas Lemke ein in dieser Form einzigartiges Kompendium interdisziplinärer Ansätze und wirft ein neues Licht auf die altenglische Beda-Übersetzung, das Literatur- und Sprachwissenschaftler, Philologen und Historiker gleichermaßen anspricht.
The invasive weed Ambrosia artemisiifolia (common ragweed) constitutes a great threat to public health and agriculture in large areas of the globe. Climate change, characterized by higher ...temperatures and prolonged vegetation periods, could increase the risk of establishment in northern Europe in the future. However, as the species is a short-day plant that requires long nights to induce bloom formation, it might still fail to produce mature seeds before the onset of winter in areas at northern latitudes characterized by short summer nights. To survey the genetic variation in flowering time and study the effect of latitudinal origin on this trait, a reciprocal common garden experiment, including eleven populations of A. artemisiifolia from Europe and North America, was conducted. The experiment was conducted both outside the range limit of the species, in Sweden and within its invaded range, in Croatia. Our main hypothesis was that the photoperiodic-thermal requirements of A. artemisiifolia constitute a barrier for reproduction at northern latitudes and, thus, halts the northern range shift despite expected climate change. Results revealed the presence of a north-south gradient in flowering time at both garden sites, indicating that certain European populations are pre-adapted to photoperiodic and thermal conditions at latitudes up to, at least, 60° N. This was confirmed by phenological recordings performed in a region close to the northern range limit, the north of Germany. Thus, we conclude that there exists a high risk for establishment and spread of A. artemisiifolia in FennoScandinavia in the near future. The range shift might occur independently of climate change, but would be accelerated by it.
The Roseobacter group and SAR11 clade constitute high proportions of the marine bacterioplankton, but only scarce information exists on the abundance of distinct populations of either lineage. ...Therefore, we quantified the abundance of the largest cluster of the Roseobacter group, the RCA (Roseobacter clade affiliated) cluster together with the SAR11 clade by quantitative PCR in the southern and eastern North Sea. The RCA cluster constituted up to 15 and 21% of total bacterial 16S ribosomal RNA (rRNA) genes in September 2005 and May 2006, respectively. At a few stations, the RCA cluster exceeded the SAR11 clade, whereas at most stations, SAR11 constituted higher fractions with maxima of 37%. In most samples, only one RCA ribotype was detected. RCA abundance was positively correlated with phaeopigments, chlorophyll, dissolved and particulate organic carbon (POC), turnover rates of dissolved free amino acids (DFAAs), temperature, and negatively correlated with salinity. The SAR11 clade was only correlated with POC (negatively, May) and with DFAA turnover rates (positively, September). An abundant RCA strain, 'Candidatus Planktomarina temperata', was isolated from the southern North Sea. This strain has an identical 16S rRNA gene sequence to the dominant RCA ribotype. Detection of the pufM gene, coding for a subunit of the reaction center of bacteriochlorophyll a, indicates the potential of the isolate for aerobic anoxygenic photosynthesis. Our study shows that a distinct population of the RCA cluster constitutes an abundant bacterioplankton group in a neritic sea of the temperate zone and indicates that this population has an important role during decaying phytoplankton blooms.
Summary
We present a new procedure for effectively detaching particle‐associated bacteria by 10% (v/v) methanol and sonication which is particularly suitable for samples with a high particle load and ...sediments. We also optimized the sample preparation by applying the highly dsDNA‐specific fluorescent stain SybrGreen I together with an optically brilliant mounting medium (polyvinylalcohol 4–88, ‘moviol’) in one step. The new protocol allows a much faster, easy and less toxic handling of samples as compared to other methods. Cells are stained directly on a black Nuclepore filter and show an intensive fluorescence signal with low background. The detachment procedure was optimized with respect to the temperature of the 10% methanol solution (35°C), ultrasonication and centrifugation. The application of the new method in comparison with detachment procedures with pyrophosphate and Tween‐80 with various types of marine samples including sediments always yielded higher numbers and/or higher fractions of particle‐associated cells. Staining and mounting the samples with the moviol‐SybrGreen I solution allowed an accurate and highly reproduceable enumeration of bacteria also in samples with high concentrations of SPM. Fixation of bacteria by glutardialdehyde resulted in a brighter fluorescence as compared to fixation by formalin. Because of the high specificity to dsDNA and bright fluorescence of SybrGreen I, the fast and easy handling and the possibility to store stained samples for at least several months at −20°C without any loss in fluorescence intensity, the newly developed method is also an attractive alternative to DAPI staining of aquatic bacteria.
Objectives
To investigate the effect of compressed SENSE (CS), an acceleration technique combining parallel imaging and compressed sensing, on potential bias and precision of brain volumetry and ...evaluate it in the context of normative brain volumetry.
Materials and methods
In total, 171 scans from scan-rescan experiments on three healthy subjects were analyzed. Each subject received 3D-T1-weighted brain MRI scans at increasing degrees of acceleration (CS-factor = 1/4/8/12/16/20/32). Single-scan acquisition times ranged from 00:41 min (CS-factor = 32) to 21:52 min (CS-factor = 1). Brain segmentation and volumetry was performed using two different software tools:
md.brain
, a proprietary software based on voxel-based morphometry, and
FreeSurfer
, an open-source software based on surface-based morphometry. Four sub-volumes were analyzed: brain parenchyma (BP), total gray matter, total white matter, and cerebrospinal fluid (CSF). Coefficient of variation (CoV) of the repeated measurements as a measure of intra-subject reliability was calculated. Intraclass correlation coefficient (ICC) with regard to increasing CS-factor was calculated as another measure of reliability. Noise-to-contrast ratio as a measure of image quality was calculated for each dataset to analyze the association between acceleration factor, noise and volumetric brain measurements.
Results
For all sub-volumes, there is a systematic bias proportional to the CS-factor which is dependent on the utilized software and subvolume. Measured volumes deviated significantly from the reference standard (CS-factor = 1), e.g. ranging from 1 to 13% for BP. The CS-induced systematic bias is driven by increased image noise. Except for CSF, reliability of brain volumetry remains high, demonstrated by low CoV (< 1% for CS-factor up to 20) and good to excellent ICC for CS-factor up to 12.
Conclusion
CS-acceleration has a systematic biasing effect on volumetric brain measurements.
Road corridors are important conduits for plant invasions, and an understanding of the underlying mechanisms is necessary for efficient management of invasive alien species in road networks. Previous ...studies identified road type with different traffic volumes as a key driver of seed dispersal and abundance of alien plants along roads. However, how the intensity of traffic interacts with the habitat features of roadsides in shaping invasion processes is not sufficiently understood. To elucidate these interactions, we analyzed the population dynamics of common ragweed (
Ambrosia artemisiifolia
L.), a common non-indigenous annual species in Europe and other continents, in a regional road network in Germany. Over a period of five years, we recorded plant densities at roadsides along four types of road corridors, subject to different intensities of traffic, and with a total length of about 300 km. We also classified roadsides in regard to habitat features (disturbance, shade). This allowed us to determine corridor- and habitat-specific mean population growth rates and spatial-temporal shifts in roadside plant abundances at the regional scale. Our results show that both traffic intensity and roadside habitat features significantly affect the population dynamics of ragweed. The combination of high traffic intensity and high disturbance intensity led to the highest mean population growth whereas population growth in less suitable habitats (e.g. shaded roadsides) declined with decreasing traffic intensity. We conclude that high traffic facilitates ragweed invasion along roads, likely due to continued seed dispersal, and can compensate partly for less suitable habitat features (i.e. shade) that decrease population growth along less trafficked roads. As a practical implication, management efforts to decline ragweed invasions within road networks (e.g. by repeated mowing) should be prioritized along high trafficked roads, and roadside with disturbed, open habitats should be reduced as far as possible, e.g. by establishing grassland from the regional species pool.
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