[Diagnostic value of localized hypofixations in the radioisotope scanning of bones]

The scintigraphic appearances of all localized, evolutive bone lesions, whatever their nature, is usually a "hot spot", that is a zone of hyperfixation of the radioactive material. False negatively scintigraphs are, however, noted: the scintigraphic image appears normal, without a zone of hyperfixation, although radiographs of the skeleton are pathological. The 8 cases presented in this article demonstrate that certain bone lesions (aseptic osteonecrosis and malignant destruction of bone) may sometimes be represented as real zones of hypofixation, as veritable "cold spots". These areas of hypofixation result from either a local interruption in the vascularization, which prevents the isotope from reaching the bony structures, or from a quantitative insufficiency of the bony tissue, this being replaced by neoplastic tissue which, in the cases studied, fixed labelled Bleomycin or iodine-131. These areas of hypofixation and any absences of fixation really are the scintigraphic images of areas of osteolysis or of aseptic osteonecrosis but they are generally masked by hyperfixation around the lesion that results in reactional osteogenesis and hypervascularization.