Recently it has become both possible and practical to use magnetic resonance (MR) at magnetic fields in the range from μT to mT, the so-called ultra-low-field (ULF) regime. SQUID (superconducting quantum interference device) sensor technology allows for ultra-sensitive detection while pulsed pre-polarizing fields greatly enhance the signal. The instrumentation allows for unprecedented flexibility in signal acquisition sequences and simplified MRI instrumentation. Here we present results for a

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... w application of ULF MRI and relaxometry for the detection and characterization of liquids. We briefly describe the motivation and advantages of the ULF MR approach, and present recent results from a seven-channel ULF MRI/relaxometer system constructed to non-invasively inspect liquids at a security checkpoint for the presence of hazardous material. The instrument was deployed at the Albuquerque International Airport in December 2008, and results from that endeavor are also presented.