The compact 3T MRI system has been in continuous operation at the Mayo Clinic since March 2016. To date, over 200 patient studies have been completed, including 96 comparison studies with a clinical 3T whole-body MRI. The increased gradient performance has reliably resulted in consistently improved image quality.
Purpose
To develop a highly efficient magnetic field gradient coil for head imaging that achieves 200 mT/m and 500 T/m/s on each axis using a standard 1 MVA gradient driver in clinical whole‐body 3.0T MR magnet.
Methods
A 42‐cm inner diameter head‐gradient used the available 89‐ to 91‐cm warm bore space in a whole‐body 3.0T magnet by increasing the radial separation between the primary and the shield coil windings to 18.6 cm. This required the removal of the standard whole‐body gradient and radiofrequency coils. To achieve a coil efficiency ~4× that of whole‐body gradients, a double‐layer primary coil design with asymmetric x‐y axes, and symmetric z‐axis was used. The use of all‐hollow conductor with direct fluid cooling of the gradient coil enabled ≥50 kW of total heat dissipation.
Results
This design achieved a coil efficiency of 0.32 mT/m/A, allowing 200 mT/m and 500 T/m/s for a 620 A/1500 V driver. The gradient coil yielded substantially reduced echo spacing, and minimum repetition time and echo time. In high b = 10,000 s/mm2 diffusion, echo time (TE) < 50 ms was achieved (>50% reduction compared with whole‐body gradients). The gradient coil passed the American College of Radiology tests for gradient linearity and distortion, and met acoustic requirements for nonsignificant risk operation.
Conclusions
Ultra‐high gradient coil performance was achieved for head imaging without substantial increases in gradient driver power in a whole‐body 3.0T magnet after removing the standard gradient coil. As such, any clinical whole‐body 3.0T MR system could be upgraded with 3‐4× improvement in gradient performance for brain imaging.
A method is described for the indirect conductimetric assessment of microbial populations by the absorption of metabolic CO2 in an alkaline absorbent solution whose conductance is monitored. The method allows microbial growth in un‐modified conventional culture media to be monitored conductimetrically.
Belief that the extended family is in terminal decline has proved to be a
remarkably persistent myth. It is currently being revived as a result of recent
statistical trends. The belief has been closely connected to sociological enquiries
undertaken over the course of the century. The validity of the belief, and in
particular the significance of grandparents within the extended family, is
explored in two sets of life story interviews recently undertaken with adults in
Britain; one set are people in their thirties who had become step-children, and
the second set participants in a multi-generational study of social mobility. The
analysis addresses questions of contact after parental loss, sources of support
within the family, the involvement of grandparents, the importance of co-residence, conflict, emotional closeness and communication within a family.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.