Filtered-phase imaging versus susceptibility-weighted imaging for paramagnetic rim lesion detection in multiple sclerosis: A head-to-head comparison.

BACKGROUND

Paramagnetic rim lesions (PRLs) detected on susceptibility-sensitive magnetic resonance imaging (MRI) represent chronic active lesions and correlate with disease progression in multiple sclerosis (MS). However, optimal detection methods remain unclear.

OBJECTIVE

To compare PRL detection using filtered-phase imaging versus susceptibility-weighted imaging (SWI) and assess inter-rater reliability among clinical neuroimmunologists.

METHODS

We retrospectively analyzed 3T MRI from 44 relapsing-remitting MS patients. Four neurologists with neuroimmunology training received 30-minute training sessions and evaluated PRLs on both filtered-phase and SWI sequences. Consensus adjudication resolved discordant ratings and served as the reference standard for calculating diagnostic accuracy.

RESULTS

PRLs were identified in 21/44 patients (48%). Relative to consensus as the reference standard, SWI demonstrated higher sensitivity than filtered-phase imaging (66.0% vs. 60.4%), while filtered phase showed superior positive predictive value (0.903 vs. 0.714). Both sequences achieved very high specificity (>97%). Inter-rater reliability was good for SWI (Intraclass Correlation Coefficient [ICC] = 0.85) and moderate for filtered phase (ICC = 0.71) for per-subject PRL counts. Vascular complexity was the most common cause of false-positive identification (65% of cases).

CONCLUSIONS

Both techniques reliably detect PRLs with substantial inter-rater agreement. Filtered-phase imaging offers superior positive predictive value, while SWI provides better sensitivity and inter-rater reliability. Further development of a standardized training program for assessment of PRL and studies directly comparing susceptibility-sensitive sequences on different vendor platforms are warranted.