Prospective respiratory triggering improves high-resolution brachial plexus MRI quality

Background: Oblique sagittal MRI sequences, orthogonal to the longitudinal axis of the brachial plexus, can reliably depict morphologic and signal abnormalities. However, nerve visualization may be obscured by ghosting artifact from periodic respiratory motion. Respiratory triggering (RT) with a thoracoabdominal bellows can reduce ghosting artifact, but it is not routinely used for brachial plexus MRI. Furthermore, the efficacy of prospective RT for brachial plexus imaging has not yet been reported.

Purpose: To compare brachial plexus MRI sequences acquired with and without respiratory triggering.

Study type: Prospective.

Subjects: Five volunteers and 20 patients were included. Each subject was imaged with and without RT during the same session.

Field strength/sequence: Proton density or T₂ -weighted Dixon fat suppressed sequences were obtained at 3.0T using receive-only 16-channel flexible array coils.

Assessment: Three musculoskeletal radiologists blindly evaluated each sequence using subjective scoring criteria for ghosting artifact, nerve conspicuity, and diagnostic confidence. Nerve conspicuity scores at three distinct plexus levels were summed to calculate an overall image quality score.

Statistical tests: Marginal proportional odds logistic regression models were used to compare all scores between RT and non-RT. Gwet's agreement coefficient was used to assess interobserver and intraobserver reliability.

Results: Mean scan time per sequence increased from 4:25 minutes (95% confidence interval [CI], 4:02-4:49 min) with non-RT to 6:09 minutes (95% CI, 5:42-6:35 min) with RT. RT reduced ghosting artifact (odds ratio [OR] = 0.21, 95% CI: 0.09-0.46, P < 0.001), improved overall image quality (OR = 4.88, 95% CI: 2.18-10.95, P < 0.001), and increased diagnostic confidence (OR = 3.72, 95% CI: 1.61-8.63, P = 0.002) for all readers. Interobserver agreement for ghosting artifact and image quality was substantial to almost perfect (AC₂ = 0.74-0.85). Interobserver agreement for all other scores was moderate to almost perfect (AC₂ = 0.61-0.82). Intraobserver agreement was substantial to almost perfect for all parameters (AC₂ = 0.76-1.0).

Data conclusion: Prospective RT with bellows can effectively minimize ghosting artifact and improve image quality for brachial plexus MRI within clinically optimal acquisition times.

Level of evidence: 1 Technical Efficacy: Stage 2.