Technical note: the comparison of hypointense lesions from ‘pseudo-T1’ and T1-weighted images in secondary progressive multiple sclerosis

Abstract

There is a large historical database of dual-echo conventional spin-echo (CSE) magnetic resonance images in multiple sclerosis (MS). If new analysis techniques can be developed then this database could provide valuable information. We have investigated a technique in which the late echo of a dual-echo data set is subtracted from the corresponding early echoyielding images, which appear qualitatively similar to T1- weighted images. This study investigated whether the hypointense lesions on the ‘pseudo-T1’ images (created as described above) were related to hypointense lesions on conventional T1-weighted images. The hypointense lesion areas were measured by a blinded observer using a computer-assisted contouring technique applied to pseudo-T1 and T1-weighted CSE images obtained from 17 patients with secondary progressive MS (SPMS). The mean hypointense lesion area from T1-weighted images was 2218- 2072 mm², compared to 1426-1353 mm² from pseudo-T1 images (p =0.008). There was, however, a strong correlation between the values obtained from the two sets of images (r =0.93, p <0.001). The strong correlation between the values obtained from the two sets of images suggests that pseudo-T1 images may be useful to investigate a subgroup of more destructive lesions in MS from historical databases and in future prospective studies when imaging time is limited.