T1 hypointense lesion load in secondary progressive multiple sclerosis: a comparison of pre versus post contrast loads and of manual versus semi automated threshold techniques for lesion segmentation.

Magnetic resonance imaging (MRI) is increasingly being used as a monitoring tool for disease activity in therapeutic trials in multiple sclerosis. There is, however, only a limited relationship between MRI findings and clinical outcome measurements. It has been suggested that hypointense lesion load on T1 weighted imaging has a better correlation with disability than the more conventional T2 hyper intense lesion load. This study was undertaken to (i) evaluate different measurement techniques used to quantify T1 hypointense lesion load, and (ii) to compare lesion load as measured using different parameters and disability. Twenty-five patients with secondary progressive multiple sclerosis, mean age of 40 years (23-57), mean EDSS 5.7 (4-7) were analysed. T2 lesion load on FSE correlated well with both the hypointense lesion load on T1 pre-gadolinium (r = 0.8, P < 0.0001) and T1 post-gadolinium (r = 0.8, P < 0.0001) but less so with the enhancing lesion load (r = 0.4, P < 0.05). There was a very strong correlation with T1 hypo-intense lesion volume pre and post gadolinium (r = 0.96, P < 0.001). However, the EDSS was not correlated with the T2 lesion load (r = -0.27, P = 0.2), T1 pre-gadolinium load (r = -0.3, P = 0.1), T1 post gadolinium load (r = -0.4, P = 0.7) and enhancing lesion load (r = -0.28, P = 0.2), or with the degree of hypointensity of T1 weighted images determined using the threshold technique. There is a strong correlation between T1 hypointense lesion volume both pre and post gadolinium and also between T1 and T2 lesion volumes.