FAST SPIN-ECHO IMAGING OF THE KNEE - FACTORS INFLUENCING CONTRAST

Conventional T2-weighted spin-echo magnetic resonance imaging of the k nee requires a long TR. Fast spin-echo (FSE) imaging can improve acqui sition efficiency severalfold by collecting multiple lines of k space for each TR. Compromises in resolution, section coverage, and contrast inevitably result. The authors examined the compromises encountered i n FSE imaging of the knee and discuss the variations in image contrast and resolution due to choices of sequence parameters. For short TR/TE knee imaging, FSE does not appear to offer any advantages, since the increased collection efficiency for one section reduces the available number of sections, so that the total imaging time for a given number of sections remains constant relative to conventional spin-echo imagin g. For T2-weighted images, considerable time can be saved and comparab le quality images can be obtained. This saved time can be usefully spe nt on increasing both the resolution of the image and its signal-to-no ise ratio, while still reducing total acquisition time by a factor of two. The preferred FSE T2-weighted images were acquired with a TR of 4 ,500 msec, TE of 120 msec, and eight echoes. The available number of s ections is compromised, and the sequence remains sensitive to now arti facts; however, the FSE sequence appears to be promising for knee imag ing.