The value of high spatial resolution and contrast material-enhanced ma
gnetic resonance (MR) imaging was assessed in 69 patients with either
femoral head avascular necrosis (AVN) or transient bone marrow edema l
esions. An AVN lesion was typically a well-demarcated epiphyseal area
of variable signal intensity. A transient bone marrow edema lesion app
eared as an ill-delimited low-signal-intensity epiphyseal area on T1-w
eighted images that converted to a high-signal-intensity area on T2-we
ighted images. T1- and T2-weighted spin-echo images helped distinguish
from AVN lesions some transient lesions apt -to simulate the segmenta
l pattern of AVN lesions. T2-weighted images also helped detect necrot
ic tissue in some unusual AVN lesions that mostly showed ill-delimited
edemalike marrow changes. In some cases, contrast-enhanced MR images
may increase diagnostic confidence by showing homogeneous hypervascula
rization in bone marrow edema lesions and by depicting hypovascular ma
rrow areas in AVN lesions. The authors believe sequential MR imaging i
s valuable in the assessment of equivocal femoral head lesions.