FAT-SUPPRESSED SPOILED GRASS IMAGING OF KNEE HYALINE CARTILAGE - TECHNIQUE OPTIMIZATION AND COMPARISON WITH CONVENTIONAL MR-IMAGING

OBJECTIVE. We studied healthy volunteers with fat-suppressed three-dim ensional (3D) spoiled gradient-recalled acquisition in the steady stat e (SPGR) to determine paramaters that maximize positive contrast betwe en knee articular cartilage and fluid, marrow fat, and muscle; and we compared the technique with conventional MR imaging sequences. The pur pose was to determine if fat-suppressed 3D SPGR imaging is useful for detecting abnormalities of the articular cartilages. SUBJECTS AND METH ODS. The knees of 10 healthy volunteers were imaged in the axial plane . Fat-suppressed 3D SPGR imaging was performed with a TR of 60 msec, a TE ranging from 5 to 15 msec, and a flip angle ranging from 20 degree s to 80 degrees. This was followed by a similar set of fat-suppressed two-dimensional (2D) SPGR images, and conventional T1- and T2-weighted spin-echo and multiplanar gradient studies. Contrast-to-noise (C/N) r atios were determined for cartilage versus a saline fluid phantom, mar row fat, and muscle. Optimal parameters were determined both quantitat ively and by a blinded subjective analysis. RESULTS. A TE of 5 msec an d a flip angle of 40 degrees demonstrated the greatest CIN ratio betwe en the signals for cartilage and for fluid, marrow, and muscle. C/N ra tios in the 3D sequences were higher than in the 2D, spin-echo, and gr adient series, although the absolute C/N ratio values for the T2-weigh ted spin-echo sequence were higher than those for the 3D fat-suppresse d SPGR sequence, Subjective analysis showed articular cartilage to hav e a consistent trilaminar appearance, and independent interpreters fav ored a 3D fat-suppressed SPGR sequence with a TE of 5 msec and a flip angle of 40 degrees. Three subjects with incidental joint fluid had C/ N ratios within a 95% confidence range for cartilage versus the fluid phantom. CONCLUSION. When a fat-suppressed 3D SPGR sequence of 60/5/40 degrees (TR/TE/flip angle) is used, MR images can show high positive contrast between articular hyaline cartilage and adjacent structures. This convenient technique is different from standard MR imaging sequen ces because it demonstrates greater signal intensity in cartilage than in fluid, marrow fat, and muscle, and because it consistently shows a n organized internal architecture of hyaline cartilage. Fat-suppressed 3D SPGR imaging therefore has promise for detecting abnormalities of the articular cartilage.