Dynamic T1-weighted spin-echo MR imaging: the role of digital subtraction in the demonstration of enhancing brain lesions.

We compared subtracted and non-subtracted images obtained from a contrast-enhanced dynamic T1-weighted spin echo (SE) magnetic resonance (MR) technique for the demonstration of enhancing brain lesions with and without associated hemorrhage. Thirty-four patients with enhancing brain lesions or subacute parenchymal hematomas were imaged using a contrast-enhanced dynamic T1-weighted SE MR technique modified by a keyhole scheme. On-line digital subtraction was performed. Non-subtracted and subtracted dynamic scans were compared for conspicuity and contrast-to-noise ratios (CNRs) of enhancing brain lesions. The presence and pattern of enhancement in the subacute parenchymal hematomas were evaluated on the subtracted images. In all, 47 enhancing brain lesions were detected on both the non-subtracted and the subtracted images. The enhancing brain lesions were more conspicuous on the subtracted images (P < 0.05). There was an increase in CNRs of the enhancing lesions on the subtracted images compared with the non-subtracted ones (P < 0.001). Seventeen subacute parenchymal hematomas were detected on the non-subtracted images. The subtracted images demonstrated enhancement in 15 hematomas (8 rim enhancement only/7 both nodular and rim enhancement). Digital subtraction in contrast-enhanced dynamic T1-weighted SE MR imaging is helpful in demonstrating enhancing brain lesions with and without associated hemorrhage.