Clinical evaluation of fast spin echo sequences for cranial magnetic resonance imaging at 0.5 tesla.

Fast spin echo (FSE) sequences enable T2-weighted MR scans to be obtained in a fraction of the time necessary for conventional SE sequences with long TR and long TE. Comparison has been made of a FSE sequence (TR = 4000 ms, effective TE = 100 ms, 2 NEX) with the T2-weighted SE sequence (TR = 2000 ms, TE = 90 ms, 1-2 NEX) normally used in 35 patients referred for cranial MRI. Contrast-to-noise ratios (CNR) for grey:white matter and brain:CSF on the FSE sequence compared favourably with variable echo (VE) sequences which take up to three times as long to acquire. Although the conspicuity of some pathological lesions such as multiple sclerosis plaques was inferior to that of conventional T2-weighted SE scans, no lesions were missed on FSE scans. The FSE sequence was more prone to movement artefacts. The benefit of the markedly increased patient throughput made possible by using the FSE sequence outweighs the slight reduction in sensitivity for small lesions.