{'fraction_non_alphanumeric': 0.04024767801857585, 'fraction_numerical': 0.004953560371517028, 'mean_word_length': 5.464, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
MR imaging of avascular necrosis of the femoral head: value of small-field-of-view sagittal surface-coil images.

We compared coronal, large-field-of-view, body-coil MR images with sagittal, small-field-of-view, surface-coil images of 30 hips for their sensitivities in establishing the diagnosis of avascular necrosis; spatially localizing the avascular necrosis; and detecting joint-space narrowing, femoral head collapse, articular cartilage fracture, and joint fluid. We also compared the two separate plane/coil combinations for detection of the "double-line" sign (high signal inside a band of low signal, believed to be characteristic for avascular necrosis) and intertrochanteric conversion of hematopoietic marrow to fatty marrow. Coronal, large-field-of-view, body-coil images provided an adequate screening examination for the presence of avascular necrosis (sensitivity of 94%) and were preferred in all cases for mediolateral localization of focal abnormality. They were also better for assessing joint fluid and detecting fatty conversion of marrow. Sagittal, small-field-of-view, surface-coil images were preferred for anteroposterior localization in all cases and for superoinferior localization of focal abnormality in 15 of 18 cases. They detected additional cases of joint-space narrowing, articular cartilage fracture, and the double-line sign missed by coronal, body-coil images. Sagittal, small-field-of-view, surface-coil images are a valuable adjunct to MR evaluation of femoral avascular necrosis because they provide additional information that may be useful for planning surgical therapy.