Ultrashort Echo Time and Zero Echo Time MRI and Their Applications at High Magnetic Fields: A Literature Survey.

Ultrashort echo time (UTE) and zero echo time (ZTE) imaging sequences have been developed to detect short T2 relaxation signals emanating from regions or tissues that conventional magnetic resonance imaging (MRI) methods fail to capture. Owing to the high dipole-dipole interactions in solid and semisolid tissues, the signal decay occurs very rapidly, typically in less than 1 ms. The echo time generated by conventional imaging methods is insufficiently short, resulting in void signals from these short-T2 species. The application of UTE and ZTE techniques enables the imaging of solid and semi-solid tissues, making the conventionally invisible visible, which can significantly impact clinical imaging. High- and ultra-high-field-strength (UHF) MRI offers a critical advantage in enhancing the sensitivity and specificity of MRI. When combined with UTE and ZTE sequences, it enables the recovery of signals from void areas and markedly improves signal quality. To bolster this approach and further validate the technique, while addressing its limitations, extensive efforts have been made to collect supplementary data using various research tools. Studies demonstrate that integrating UTE and ZTE sequences with advanced high and ultra-high field imaging techniques-particularly innovative developments in transmit/receive hardware, software, and novel trajectory approaches-plays a pivotal role in enhancing the clarity and accuracy of MRI for musculoskeletal, neural, lung, and dental applications.