The value of chemical fat-saturation pulse added to T1-weighted spin-echo sequence in evaluating gadolinium- enhancing brain lesions in multiple sclerosis

Purpose. This study was undertaken to assess the value of a chemical (spectral) fat-saturation (fat-sat) pulse added to a T1-weighted spin-echo sequence after intravenous administration of paramagnetic contrast agent in detecting enhancing lesions in multiple sclerosis. Materials and methods. Twenty patients with relapsing-remitting multiple sclerosis underwent a brain 1.0-Tesla magnetic resonance (MR) scan with T1-weighted spin-echo sequences (24 contiguous para-axial slices with a thickness of 5 mm, pixel size 0.96 mm 2, number of excitations 2, flip angle 90°) 5 min after intravenous injection of 0.1 mmol/kg of gadodiamide with and without fat-sat, acquired with randomised order of priority. Two readers counted by consensus the number of enhancing lesions and assigned a conspicuity score (low conspicuity=1; high conspicuity=2) to each enhancing lesion during a randomised reading without any visual comparison between the two corresponding images (with and without fat-sat) of the same patient. McNemar and Wilcoxon matched-pair signed-rank tests were used. Results. Seventy-two enhancing lesions without fat-sat and 94 with fat-sat were detected; 22 lesions were visible only with fatsat, whereas no lesion was detected only without fat-sat (p<0.0001). The conspicuity score was 1.17±0.38 (mean±standard deviation) and 1.57±0.44, respectively (p<0.0001). Conclusions. A fat-sat pulse added to a T1-weighted spin-echo sequence increases significantly the number and conspicuity of contrast-enhancing lesions in patients with relapsing-remitting multiple sclerosis.