Avacular Necrosis of the Femoral Head: MR Imaging with Histologic Correlation

PURPOSE: To correlate MR findings with histologic findings in avascular necrosis(AVN) of the femoral head. MATERIALS AND METHODS: MR imaging was performed with 8 femoral head specimens using T1- and proton density weighted coronal SE sequences, and compared with contact radiography and histologic sections. RESULTS: In each specimen, necrotic zone in the superior portion of femoral head, repair zone located inferior to the necrotic zone, and rim adjacent to normal bone marrow could be defined. Necrotic zone showed high signal intensity on both T1- and proton density- weighted images in 3 cases which were composed of necrotic bone and marrow, and low signal intensity on both sequences in 2 cases which were composed of necrotic bone marrow with amorphous cellular debris. Mixed high and low signal intensities were seen in 3 cases. The repair zone showed low signal intensity on Tl-weighted image and high signal intenisty on proton density weighted image in 5 cases which were composed of thickened trabecular bone and meSenchymal tissue and also showed intermediate signal intensity on T1 weighted image and high signal intensity on proton density weighted image in 3 cases which were composed of osteoid, chondroid and undifferentiated mesenchymal cells. Rim shown as the low signal intensity on T1 weighted image in all cases was corresponded to viable thickened trabecular bone. CONCLUSION: MR imaging would be the best modality in the diagnosis of avascular necrosis of fernoral head and when used in conjuction with degree and location of signal intensity, the prediction of histologic finding may be possible.

Contrast Enhancement Pattern in MR Imaging of Acute Cerebral Infarction

PURPOSE: To present the enhancement pattern of acute cerebral or cerebellar cortical infarctions aged 1-3 days on MR. MATERIALS AND METHODS: Contrast-enhanced MR images of 26 patients with acute cerebral or cerebellar ischemic events were retrospectively reviewed. MR was performed within 3 days after ictus. RESULTS: Contrast enhancement in the area of infarction was observed in 61.5% (16/26) on MR. Of these 50% (13/26) showed non-parenchymal enhancement (NPE) representing either vascular or leptomeningeal enhancement, 7.7% (2/26) showed parenchymal enhancement (PE), and 2.8% (1/26) showed both NPE and PE. The earliest enhancement was seen in images obtained 12 hours after the onset of symptoms and appeared as NPE. One patient showed NPE without apparent high signal intensity at the corresponding area on T2-weighted images. In 38. 5% (10/26), there was no enhancement. CONCLUSION: Contrast-enhanced MR imaging may be needed in acute ischemic infarction, because NPE may be seen as the earliest MR finding of acute cortical infarction aged 1-3 days.

Bilobate Anterior Epidural Extension of Vertebral Lesion: MRI Features

PURPOSE: To determine the value of bilobate anterior epidrual extension(AEE) on MRI in differential diagnosis of tuberculous spondylitis, pyogenic spondylitis and malignant tumor. MATERIALS AND METHODS: SE TI-,T2- and Gd-DTPA enhanced Tl-weighted, sagittal and axial MR images of 39 patients(40 vertebral lesions), including 16 tuberculous spondylitis, 7 pyogenic spondylitis(8 lesions, consisting of 2 separate lesion of 1 patient), and 16 malignant vertebral tumors(15 metastases,1 lymphoma) with an AEE were reviewed. The frequency of bilobate AEE shown as double-convexity in the anterior epidural space on axial scans was evaluated in the above vertebral diseases. RESULTS: The bilobate AEE on the axial scans was seen in 12 out of the 16 tuberculous spondytitis(75%) and 1 out of 8 pyogenic spondylitis(13%), and 10 out of the 16 malignant tumor including 15 metastasis and 1 lymphoma(63%). CONCLUSION: The bilobate'