T1強調画像差分マップによる多発性硬化症における造影増強病変検出能の向上

In multiple sclerosis (MS), detection of contrast-enhancing lesions (T1c + L) by magnetic resonance imaging (MRI) provides valuable information for initial diagnosis and supports monitoring of acute disease activity. We investigated the added value of subtraction maps from T1-weighted images (T1_sub) for correctly detecting T1c + L.

Magnetic resonance images of 555 scans in 286 MS patients were normalized into [0;1] range and co-registered for T1_sub calculation. Ground truth (GT) assessment of T1c + L was established through consensus readings using all available sequences, particularly T1_sub images. Detection accuracy was compared to GT by three independent neuroradiologists, one with and two without available T1_sub.

GT identified 1109 T1c + L, of which 1037 were detected with subtraction maps. Without subtraction maps, approximately half of these lesions were missed. Lesions overlooked without T1_sub were smaller, less hyperintense in post-contrast scans, and more frequently located infratentorial. Without T1_sub, about one contrast-enhancing lesion remained undetected per scan; however, including T1_sub reduced the relative risk of missing a lesion by nearly 80 %. Furthermore, almost a third of examinations were falsely interpreted as free of any T1c + L. In contrast, by T1_sub implementation, the proportion of inconspicuous reports was reduced by nearly 90 %.

In a clinically meaningful way, subtraction maps improve detection of contrast-enhancing MS lesions, particularly when smaller, less intense, and infratentorial.