Scientific Concept of the National Cohort (status ... - Nationale Kohorte

A.3
A.3 Study design
diseases in various organs and is routinely applied in low-prevalence populations. However,
to date, whole-body MRI has been rarely implemented in larger prospective cohort studies,
given the long acquisition and postprocessing times and insufficient resolution in the past.
Except for the SHIP study 679, 680 , whole-body MRI has not been implemented in any major
cohort nationally and internationally. Using a 3-Tesla scanner, the National Cohort will be in
a unique position to determine the predictive role of advanced, high-resolution, morphologic
phenotyping.
In the past, the assessment of multiple organs was restricted by a long examination time since
the patient had to be repositioned for single organ examinations and coils had to be changed
several times. Faster approaches for imaging of the entire body could only be implemented at
the expense of spatial and temporal resolution. Indeed, the capability of performing multiregion
and whole-body MR scans in clinical routine is a relatively new development 681-683 .
New technical improvements such as the introduction of parallel acquisition techniques
(PAT) 684 , continuous table movement techniques, multichannel receiver coils, and new sequences
685, 686 make it possible to examine different organ systems in a whole-body approach
within a reasonable scanning time of approximately 45 min 687-691 . Continuous table
movement (CTM), for example, has recently been introduced as a promising new concept
to accelerate MRI acquisition 689, 690, 692-696 . By using this technique, real-time whole-body MRI
is a seamless process during data acquisition, thereby reducing acquisition time by a factor
of 2–3. Recently, the technique has been employed in MR angiography (MRA )691, 697-699 and
oncological imaging 700-705.
MRA shows a higher accuracy, less operator dependence, a larger field-of-view, threedimensionality,
and better contrast resolution than ultrasonography. So far, contrast-enhanced
MRA using extracellular contrast agents represents standard practice. However, a
large variety of recent studies have proven that non-contrast-enhanced MRA may provide
an equivalent alternative imaging approach for patients who are at risk of developing nephrogenic
systemic fibrosis and other contrast-related complications and might therefore be of
high interest for imaging a large cohort of subjects 706-708 .
A.3.4.3 Objectives
The proposed MRI imaging substudy will apply a standardized comprehensive MRI protocol
to a random set of asymptomatic individuals both at baseline and follow-up. This will generate
a comprehensive morphologic and functional biorepository, which will serve as a source
for numerous analyses to understand the role of MRI-derived morphologic changes and
abnormalities in the natural history of various conditions as well as their potential value as
risk factors for the prediction and development of subclinical and overt disease states. The
specific objectives detailed below were formulated in collaboration with each thematic working
group, indicating their focus and major interest, but may be considered as examples
among a rich set of other novel, predominantly hypothesis-generating scientific foci.
The overall objective is supported by parallel and complementary objectives related to five
body organ systems. These objectives are addressed by the specific steps within the imaging
protocol (see below).
Brain / nervous system
Subclinical cerebrovascular disorders
MR imaging is the only available method to comprehensively examine brain morphology
noninvasively and without radiation exposure. Particularly, the prevalence and incidence
as well as cross-sectional and longitudinal associations and predictive value of subclini-
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