The Mitchell classification is used to stage osteonecrosis of the femoral head and is based on MRI signal characteristics within the centre of the lesion on T1 and T2-weighted images.
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Classification
The lesion is classified into four stages with stage A representing early disease and stage D representing late disease. However, the signal intensity of more than one stage can be found in a single lesion.
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stage A
T1: hyperintense
T2: intermediate
signal analogous to that of fat
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stage B
T1: hyperintense
T2: hyperintense
signal analogous to that of subacute blood
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stage C
T1: hypointense
T2: hyperintense
signal analogous to that of fluid/oedema
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stage D
T1: hypointense
T2: hypointense
signal analogous to that of fibrosis
History and etymology
This classification was described by D G Mitchell et al. in 1987 1.