The MRI study within the German National Cohort, a large-scale, population-based, longitudinal study in Germany, comprises comprehensive characterization and phenotyping of a total of 30 000 participants using 3-Tesla whole-body MR imaging. A multi-centric study design was established together with dedicated core facilities for e. g. managing incidental findings or providing quality assurance. As such, the study represents a unique opportunity to substantially impact imaging-based risk stratification leading to personalized and precision medicine. Supported by the developments in the field of computational science, the newly developing scientific field of radiomics has large potential for the future. In the present article we provide an overview on population-based imaging and Radiomics and conceptualize the rationale and design of the MRI study within the German National Cohort. Key Points: • Population-based imaging and Radiomics constitute two emerging fields with great oppertunities and challenges for Radiology. • As part of the MRI-study of the NAKO approximately 30 000 subjects will undergo 3 Tesla whole-body MRI. • MR Imaging data is publicly accessable and will provide important insights into the natural history of disease processes and personalized risk profiles of the general population. Citation Format: • Schlett CL, Hendel T, Weckbach S et al. Population-Based Imaging and Radiomics: Rationale and Perspective of the German National Cohort MRI Study. Fortschr Röntgenstr 2016; 188: 652 – 661
Motion vision is of fundamental importance for moving animals from arthropods to mammals. In this thesis I lay ground for the functional analysis of the neural circuit underlying visual motion detection in fruit flies by means of genetic tools. In Drosophila melanogaster transgenic tools allow for both experimental observation and manipulation of neural activity: genetically encoded calcium indicators (GECIs) can be used for the optophysiological characterization of neural activity and transgenes for the inhibition of neural activity can be used to determine these neurons' function. Combined, yet independent use of both tools is a powerful approach for the functional analysis of a neural network. However, GECI signals in vivo generally suffer from poor signal-to-noise ratios and GECI characteristics change dramatically and unpredictably when transfered from the cuvette into neurons of living animals, probably due to interactions with native cellular proteins.
Here, I quantified and compared the in vivo response properties of five new (Yellow Cameleon 3.60 & 2.60, D3cpV, TN-XL and TN-XXL) and two more established ratiometric GECIs (Yellow Cameleon 3.3, TN-L15). In addition, I included the single-chromophore probe GCaMP 1.6 in this comparison. The analysis was performed under 2-photon microscopy at presynaptic boutons of neuromuscular junctions in transgenic fly larvae. I quantified action potential induced changes of calcium concentrations by calibrating responses of a synthetic calcium indicator that was microinjected under 2-photon guidance. The observed cytosolic calcium concentration was 31 nM at rest and increased linearly
with stimulus frequency by 0.1 to 1.8 uM at sustained activity of 10 and 160 Hz, respectively.
This allowed for a quantitative comparison of the responses of GECIs in terms of their steady state response amplitudes, signal-to-noise ratio, response kinetics, calcium
affinities and hill coefficients in vivo. The results were then compared to in vitro properties of GECIs measured in cuvettes.
The data reveal that a new generation of GECIs retain improved signalling characteristics in vivo. Maximum
fluorescence changes were 2-3 fold increased in new compared to former ratiometric GECI variants. Small calcium changes in response to 10 Hz stimulation induced fluorescence responses with signal-to-noise ratio above 2 in Yellow Cameleon 2.60 & 3.60, D3cpv and TN-XXL. Kinetics were slowest in Yellow Cameleon 2.60 and fastest in TN-XL. The observed changes between in vitro and in vivo performance revealed systematic differences between GECIs of different types. GECIs in this study employ different calcium sensing molecules: calmodulin-M13 in Yellow Cameleons and GCaMP, a redesigned calmodulin-M13 in D3cpv, and troponin C in TN-indicators. Those indicators comprising calmodulin-M13 as calcium sensors displayed reduced maximum fluorescence changes and reduced hill coefficients in vivo, while troponin-based GECIs and D3cpv showed increased hill coefficients and increased maximum fluorescence changes in vivo. Calcium affinity of all GECIs was increased in vivo. The results demonstrate that there are now suitable
GECIs at hand for experimental questions at differing expected calcium regimes. However, in contrast to a synthetic calcium sensor, none of the tested GECIs reported calcium concentration changes related to single action potentials at presynaptic boutons of the neuromuscular junction.
In the visual system of Drosophila, optical recordings from motion sensitive neurons while selectively blocking certain classes of columnar neurons will allow for a network analysis of the motion detection circuit. The Gal4-UAS system can be used to express proteins that block neural activity. A similar two-part expression system, based on bacterial protein- DNA interaction (LexA and LexA-operator), can be used in parallel to drive the expression of GECIs. I generated flies expressing TN-XXL or Yellow Cameleon 3.60 under the control of the LexA-operator and demonstrated GECI expression in olfactory receptor neurons. In parallel, I cloned putative genomic enhancers that can be used to drive LexA expression in motion sensitive cells of the flies visual system.
Finally, adult fixed flies expressing TN-XXL in motion sensitive neurons were visually stimulated by large field moving gratings. Parallel fluorescence measurements from these neurons showed for the first time directional selective calcium responses in Drosophila. The next step will now be the combination of calcium imaging in these neurons and functional blocking of their presynaptic partners.
Zusammenfassung Die Steuerung des Verhaltens ist die biologische Funktion des Gehirns und der zentrale Gegenstand der Neurowissenschaft. Um diese Frage anzugehen, stellen wir ein zellulär sehr einfaches Modellsystem vor. Das Riechsystem der Taufliegenlarve (Drosophila) ist grundsätzlich dem der erwachsenen Fliege und dem von Säugern sehr ähnlich, sowohl was die „Logik“ der Rezeptorgenexpression angeht, als auch bezüglich der neuronalen Verschaltungen im Gehirn. Dabei kommen die Larven mit millionenfach weniger Zellen aus und können sich trotzdem in ihrer Duftumwelt zurecht finden und einfache Duftlernaufgaben bewältigen. Wir geben eine Übersicht über die Riech- und Schmecksysteme der Drosophila-Larve und stellen ein robustes Experiment zum verknüpfenden, assoziativen Lernen zwischen Düften und Futterbelohnung vor. Dazu werden erste Erkenntnisse über die beteiligten molekularen Vorgänge, Gehirnbereiche und Zellen dargestellt. Die Kombination aus Lernfähigkeit und zellulärer Einfachkeit der Larve mit den reichhaltigen Methoden der Drosophila-Genetik bereichern die neurobiologische Forschung um ein vielversprechendes Modellsystem.
Recent advance in the design of genetically encoded calcium indicators (GECIs) has further increased their potential for direct measurements of activity in intact neural circuits. However, a quantitative analysis of their fluorescence changes (Δ F ) in vivo and the relationship to the underlying neural activity and changes in intracellular calcium concentration (Δ[Ca 2+ ] i ) has not been given. We used two-photon microscopy, microinjection of synthetic Ca 2+ dyes and in vivo calibration of Oregon-Green-BAPTA-1 (OGB-1) to estimate [Ca 2+ ] i at rest and Δ[Ca 2+ ] i at different action potential frequencies in presynaptic motoneuron boutons of transgenic Drosophila larvae. We calibrated Δ F of eight different GECIs in vivo to neural activity, Δ[Ca 2+ ] i , and Δ F of purified GECI protein at similar Δ[Ca 2+ ] in vitro . Yellow Cameleon 3.60 (YC3.60), YC2.60, D3cpv, and TN-XL exhibited twofold higher maximum Δ F compared with YC3.3 and TN-L15 in vivo . Maximum Δ F of GCaMP2 and GCaMP1.6 were almost identical. Small Δ[Ca 2+ ] i were reported best by YC3.60, D3cpv, and YC2.60. The kinetics of Δ[Ca 2+ ] i was massively distorted by all GECIs, with YC2.60 showing the slowest kinetics, whereas TN-XL exhibited the fastest decay. Single spikes were only reported by OGB-1; all GECIs were blind for Δ[Ca 2+ ] i associated with single action potentials. YC3.60 and D3cpv tentatively reported spike doublets. In vivo , the K D (dissociation constant) of all GECIs was shifted toward lower values, the Hill coefficient was changed, and the maximum Δ F was reduced. The latter could be attributed to resting [Ca 2+ ] i and the optical filters of the equipment. These results suggest increased sensitivity of new GECIs but still slow on rates for calcium binding.
Reproducible image quality is of high relevance for large cohort studies and can be challenging for magnetic resonance imaging (MRI). Automated image quality assessment may contribute to conducting radiologic studies effectively.The aims of this study were to assess protocol repetition frequency in population-based whole-body MRI along with its effect on examination time and to examine the applicability of automated image quality assessment for predicting decision-making regarding repeated acquisitions.All participants enrolled in the prospective, multicenter German National Cohort (NAKO) study who underwent whole-body MRI at 1 of 5 sites from 2014 to 2016 were included in this analysis (n = 11,347). A standardized examination program of 12 protocols was used. Acquisitions were carried out by certified radiologic technologists, who were authorized to repeat protocols based on their visual perception of image quality. Eleven image quality parameters were derived fully automatically from the acquired images, and their discrimination ability regarding baseline acquisitions and repetitions was tested.At least 1 protocol was repeated in 12% (n = 1359) of participants, and more than 1 protocol in 1.6% (n = 181). The repetition frequency differed across protocols (P < 0.001), imaging sites (P < 0.001), and over the study period (P < 0.001). The mean total scan time was 62.6 minutes in participants without and 67.4 minutes in participants with protocol repetitions (mean difference, 4.8 minutes; 95% confidence interval, 4.5-5.2 minutes). Ten of the automatically derived image quality parameters were individually retrospectively predictive for the repetition of particular protocols; for instance, "signal-to-noise ratio" alone provided an area under the curve of 0.65 (P < 0.001) for repetition of the Cardio Cine SSFP SAX protocol. Combinations generally improved prediction ability, as exemplified by "image sharpness" plus "foreground ratio" yielding an area under the curve of 0.89 (P < 0.001) for repetition of the Neuro T1w 3D MPRAGE protocol, versus 0.85 (P < 0.001) and 0.68 (P < 0.001) as individual parameters.Magnetic resonance imaging protocol repetitions were necessary in approximately 12% of scans even in the highly standardized setting of a large cohort study. Automated image quality assessment shows predictive value for the technologists' decision to perform protocol repetitions and has the potential to improve imaging efficiency.
Introduction Whole-body magnetic resonance (MR) imaging is increasingly implemented in population-based cohorts and clinical settings. However, to quantify the variability introduced by the different scanners is essential to make conclusions about clinical and biological data, and relevant for internal/external validity. Thus, we determined the interscanner and intrascanner variability of different 3 T MR scanners for whole-body imaging. Methods Thirty volunteers were enrolled to undergo multicentric, interscanner as well intrascanner imaging as part of the German National Cohort pilot studies. A comprehensive whole-body MR protocol was installed at 9 sites including 7 different MR scanner models by all 4 major vendors. A set of quantitative, organ-specific measures (n = 20; eg, volume of brain's gray/white matter, pulmonary trunk diameter, vertebral body height) were obtained in blinded fashion. Reproducibility was determined using mean weighted relative differences and intraclass correlation coefficients. Results All participants (44 ± 14 years, 50% female) successfully completed the imaging protocol except for two because of technical issues. Mean scan time was 2 hours and 32 minutes and differed significantly across scanners (range, 1 hour 59 minutes to 3 hours 12 minutes). A higher reproducibility of obtained measurements was observed for intrascanner than for interscanner comparisons (intraclass correlation coefficients, 0.80 ± 0.17 vs 0.60 ± 0.31, P = 0.005, respectively). In the interscanner comparison, mean relative difference ranged from 1.0% to 53.2%. Conversely, in the intrascanner comparison, mean relative difference ranged from 0.1% to 15.6%. There were no statistical differences for intrascanner and interscanner reproducibility between the different organ foci (all P ≥ 0.24). Conclusions While whole-body MR imaging-derived, organ-specific parameters are generally associated with good to excellent reproducibility, smaller differences are obtained when using identical MR scanner models by a single vendor.
The German National Cohort (NAKO) is a multidisciplinary, population-based prospective cohort study that aims to investigate the causes of widespread diseases, identify risk factors and improve early detection and prevention of disease. Specifically, NAKO is designed to identify novel and better characterize established risk and protection factors for the development of cardiovascular diseases, cancer, diabetes, neurodegenerative and psychiatric diseases, musculoskeletal diseases, respiratory and infectious diseases in a random sample of the general population. Between 2014 and 2019, a total of 205,415 men and women aged 19-74 years were recruited and examined in 18 study centres in Germany. The baseline assessment included a face-to-face interview, self-administered questionnaires and a wide range of biomedical examinations. Biomaterials were collected from all participants including serum, EDTA plasma, buffy coats, RNA and erythrocytes, urine, saliva, nasal swabs and stool. In 56,971 participants, an intensified examination programme was implemented. Whole-body 3T magnetic resonance imaging was performed in 30,861 participants on dedicated scanners. NAKO collects follow-up information on incident diseases through a combination of active follow-up using self-report via written questionnaires at 2-3 year intervals and passive follow-up via record linkages. All study participants are invited for re-examinations at the study centres in 4-5 year intervals. Thereby, longitudinal information on changes in risk factor profiles and in vascular, cardiac, metabolic, neurocognitive, pulmonary and sensory function is collected. NAKO is a major resource for population-based epidemiology to identify new and tailored strategies for early detection, prediction, prevention and treatment of major diseases for the next 30 years.
