Ultra-short and zero echo time MRI sequences for MSK investigation: A scoping review

Magnetic resonance imaging (MRI) has limited capacity to visualise cortical bone due to its low proton density and short decay time. Recently developed ultrashort (UTE) and zero-echo time (ZTE) sequences enable bone imaging without ionising radiation. This study aims to identify the key technical parameters, advantages, and limitations of UTE and ZTE for musculoskeletal (MSK) imaging.

JBI methodology was applied, and three databases (MEDLINE, EMBASE and CINAHL) were selected to identify articles published after 2005 (French-English). Keywordsand MeSH terms related to UTE, ZTE, MRI and MSK were used. Two independent reviewers screened titles, abstracts, and full texts. Disagreements were solved through consensus.

From 671 articles, 18 met all criteria. UTE and ZTE were applied for spine (6/18), lower limb (4/18), head and neck (4/18), general bone (3/18) and shoulder (1/18) investigations. Eight articles suggest a very short repetition time (TR) (0.425-8 ms), three longer TR (100-1075 ms), six did not mention TR. All articles mentioned very short echo time (TE) (0.00-0.34 ms). Acquisition time ranged from 3 to 12 min. UTE and ZTE are based on radial acquisition, allowing to acquire the cortical bone signal and increasing fracture contrast, comparable to CT-scan. Acquisition time was the main disadvantage.

UTE and ZTE sequences are promising for the MSK applications, offering good contrast for cortical bone evaluation. Further studies are necessary to assess the possibilities of AI tools as approaches to improve image quality and reduce acquisition time.

UTE and ZTE sequences can be added to MSK MRI exams to improve fracture and cortical bone evaluation, allowing radiation-free imaging. ZTE's lower acoustic noise benefits anxious, paediatric, or dementia patients' MRI experience.