THE DOUBLE-LINE SIGN OF OSTEONECROSIS - EVALUATION ON CHEMICAL-SHIFT MR IMAGES

The MR appearance of osteonecrosis was assessed on selective fat and w ater images to further evaluate the features of the double-line sign o f osteonecrosis. Conventional T1- and T2-weighted spin-echo and freque ncy selective chemical shift images of eight patients with avascular n ecrosis of the femoral head and three patients with bone infarcts were retrospectively reviewed. Eight of 11 patients showed a double-line s ign on T2-weighted spin-echo images. In these cases correlation with s elective water images revealed that a chemical shift artifact contribu ted to the appearance and location of the hyperintense line. The doubl e-line sign was not seen in three patients with radiologically and cli nically proven osteonecrosis. It is concluded that chemical shift imag ing improves our understanding of the nature of the double-line sign.