10 mT MRI with Superconducting and Room Temperature Detection

  • Dipartimento di Fisica - Aula 500
  • Seminario

Relatori

Prof. Stefania Della Penna
Department of Neuroscience, Imaging and Clinical Sciences, G. D'Annunzio University

Dettagli

Magnetic Resonance Imaging (MRI) at measurement fields of the order of 0.1 mT has been demonstrated thanks to the use of a pre-polarization field of the order of several tens of mT and to the exquisite sensitivity of SQUID based sensors. Despite to the SNR reduction with respect to standard high field MRI, there are several advantages in operating at ULF, such as the increased tissue contrast, the reduced cost and weight of scanners, the possibility to image patients that are not compatible with clinical scanners, the possibility to integrate different imaging modalities.

Specifically, this MRI set-up has provided images of the human head and might be compatible with Magnetoencephalography (MEG), but the time required for recording images is still too large. A possible strategy to speed-up data recording is to avoid the use of the pre-polarization field with the simultaneous increase of the measurement field up to ~10 mT. This field strength is still compatible with a MEG environment (MEG uses SQUID sensors and is installed in a magnetically shielded room) and can be generated by compact or open schemes. The magnetic resonance (MR) signal at 10 mT can be detected either by tuned volume coils at room temperature or by surface channels based on superconducting mixed sensors. The latter ones are hybrid sensors consisting of a superconducting loop (YBCO or Nb) with a constriction above which Giant Magnetic Resistances are placed.  These devices are able to detect changes of the local magnetic field as a function of the flux applied to the loop. Mixed sensors are more robust than SQUIDs when operated in a NMR applied field and their sensitivity is suitable for MRI. Different MRI set-ups at 10 mT with compact or open measurement field, using superconducting detection through mixed sensors or using volume coils at room temperature are discussed and compared