Assessment of osteosarcoma response to neoadjuvant chemotherapy: comparative usefulness of dynamic gadolinium-enhanced spin-echo magnetic resonance imaging and technetium-99m skeletal angioscintigraphy.

The aim of this work was to study and compare the usefulness of dynamic contrast-enhanced spin-echo MR imaging with high temporal resolution hydroxymethylene diphosphonate technetium-99 m skeletal angioscintigraphy in predicting the osteosarcoma histological response to neoadjuvant chemotherapy. Twelve patients with resectable osteosarcoma were prospectively monitored with dynamic MR imaging and skeletal scintigraphy before start of neoadjuvant chemotherapy, after two cycles of therapy and before surgery. Neoplasm signal intensity and activity intensity were plotted against time, and slopes were calculated for percentage increase over baseline values in the first minute. Stability and increase in slope values during or after chemotherapy were defined as a "radiological non-response". Changes in slopes were compared with the "histological response" (Huvos grading). At midpoint of the chemotherapy, these two imaging modalities failed in predicting final histological response. After the completion of the chemotherapy, these imaging modalities allowed the prediction of histological response with the same accuracy (91 %). In this series, dynamic MR imaging and technetium skeletal scintigraphy provide similar results regarding the prediction of final histological response during neoadjuvant chemotherapy; these results cannot be used to modify the therapeutic protocol at midpoint of chemotherapy; these imaging tools predict accurately the histological response at the end of chemotherapy. These latter results may permit anticipation of the adjuvant chemotherapy strategy during decalcification procedures in resected osteosarcoma and thus to monitor chemotherapy in non-surgical osteosarcoma.

Assessment of the bone mineral density in the lumbar vertebrae of newborns by quantitative computed tomography.

OBJECTIVE: To assess the true mineral density (BMD, in g/cm3) of the lumbar spine in newborns. DESIGN AND PATIENTS: A postmortem analysis of five infants with gestational ages ranging from 35 to 40 weeks, and birth weights from 2765 to 3200 g, was conducted using dual-energy quantitative computed tomography (QCT; Siemens Somatom DR). A 2 or 4 mm thick slice was obtained for each lumbar vertebra from L1 to L4. The density measured in these vertebrae was corrected by reference to a solid phantom (Osteo-CT) measured simultaneously. A three-dimensional image of the spine (Elscint CT Twin), as well as a photomicrograph of histological preparation from L2 vertebra, were also obtained in another term baby for comparison with the CT results. RESULTS AND CONCLUSIONS: In the range of values studied, the vertebral densities were not dependent on birth weight. BMD values measured in L2, L3 and L4 were not significantly different, but were 10% lower than in L1 in four of five infants. The spatial resolution of the QCT protocol used (0.4 mm) did not permit the differentiation of trabecular and cortical bone, and the vertebral bodies appeared very homogeneous and dense, with a mean density value of 210 +/- 30 mg Ca/cm3, which is 2.5 times higher than the mean maximum value found in young normal adults. These preliminary results highlight the potential of QCT in neonatology. Special protocols will, however, need to be developed for in vivo measurements in this particular paediatric field.