MRI machines have a blind spot right after the pulse, and a Stuttgart team closed it
Here is something about MRI I did not know until this week. The machine hits your tissue with a strong radio pulse, then listens for the faint signal that comes back. The catch is that the same coil does both jobs. After it sends out a pulse, it has to switch over to listening, and that switch takes time. Engineers call it the dead time. It is short, but anything that fades away during it is just gone. Some materials and some tissues give signals that die that fast, so they never show up at all.
A group at the University of Stuttgart, led by Jens Anders at the Institute of Smart Sensors, published a way around it in Science Advances. Instead of switching between sending and receiving, they do both at the same time. The setup uses a flat segmented coil driven by an array of voltage-controlled oscillators built onto a chip, running at 477 MHz. There is no transmit-receive switch and the receiver never gets gated off.
Because they are listening the whole time, they can watch the spins wobbling during the pulse itself, and they see the signal start decaying the moment the pulse ends. They also ran a Hahn echo sequence on a second setup at 17 MHz to show it handles real multi-pulse work.
The obvious uses are medical scans and materials testing, including checking porosity in concrete. I like this one because the fix is not a bigger magnet, it is better electronics.
El hecho de que usen una bobina plana segmentada a 477 MHz y eliminen el switch de transmisión‑recepción es práctico, la diferencia se nota en la captura del señal durante el pulso. Además, probaron la secuencia Hahn echo a 17 MHz para demostrar que funciona con pulsos múltiples. Esto es genial para diagnósticos sin necesidad de imanes más grandes.