MRI Staging of Avascular Necrosis

A staging system has been developed for avascular necrosis based on signal characteristics at the center of the lesion.

Class	T1	T2	Comment
A	High	Intermediate	Fat
B	High	High	Blood
C	Low	High	Fluid
D	Low	Low	Fibrosis

Class A signal intensity is typically seen in early disease, while class D signal intensity is typically seen in late disease. However, more than one class of signal intensity can be found in a single lesion.

References

Mitchell DG, Rao VM, Dalinka MK, Spritzer CE, Alavi A, Steinberg ME, Fallon M, Kressel HY. Femoral head avascular necrosis: correlation of MR imaging, radiographic staging, radionuclide imaging, and clinical findings. Radiology. 1987 Mar;162(3):709-15.