Low-Field MRI for Knee Imaging: Current Insights and Evidence From a Systematic Review.

BACKGROUND

Low-field magnetic resonance imaging (MRI) has regained interest for musculoskeletal imaging due to advances in magnet design, hardware optimization, and artificial intelligence (AI)-based reconstruction, offering improved accessibility, patient comfort, and sustainability.

PURPOSE: This systematic review aimed to explore and summarize the current status of low-field MRI for knee investigations.

STUDY TYPE: Systematic review on MEDLINE, Cinhal, EMBASE, Web of Science, Scopus, and Google Scholar databases. PROSPERO protocol (CRD42024544354).

POPULATION: Approximately 3400 participants (8-89 years) encompassing healthy volunteers, community-based cohorts, and patients with diverse knee pathologies were evaluated. Few studies incorporate phantom experiments.

FIELD STRENGTH/SEQUENCE: This review covered a range of very-low-field (< 0.1 T), conventional low-field (0.1-< 0.29 T), and upper-range low-field (> 0.3 T-0.55 T) with standard, extremity, open, and weight-bearing/standing systems. SE/FSE and GRE sequences, 3D GRE quantitative protocols, and AI-based were used.

ASSESSMENT: Two reviewers independently extracted data on knee protocols, technical parameters, diagnostic performance, and reported advantages and limitations.

STATISTICAL TESTS: Study quality was assessed using appropriate JBI critical appraisal tools. A narrative synthesis and descriptive analysis of the findings from the included studies are provided due to the heterogeneity of the intervention and outcome.

RESULTS

From 3726 records, 31 were included. Low-field MRI demonstrated high diagnostic performance for meniscal and ligamentous injuries but lower sensitivity for early cartilage degeneration. Weight-bearing MRI provided distinct functional information but not direct equivalence to standard MRI. AI-enhanced reconstruction was evaluated in a limited number of single-center, vendor-specific studies and was associated with improved image quality and diagnostic confidence. Important limitations included lower signal-to-noise ratio, reduced spatial resolution, protocol heterogeneity, and limited pathology-validated evidence.

DATA

CONCLUSION

Low-field MRI may provide a clinically useful complementary option for selected knee meniscal and ligamentous indications. However, heterogeneous evidence, influenced by field strength, scanner design, sequences, and reference standards, limits claims of equivalence with high-field MRI, particularly for subtle cartilage lesions. Advances in hardware and AI have improved image quality and efficiency; however, evidence is limited and larger standardized multicenter studies are required.

EVIDENCE LEVEL: 5.

TECHNICAL EFFICACY: Stage 5.