Twenty patients with biopsy-proven osteogenic (11 cases) or Ewing's (nine cases) sarcoma were evaluated by MR imaging on a 0.15-T resistive unit to determine the value of MR in the diagnosis and treatment of these two neoplasms and to develop the best protocol for MR imaging. In all 20 cases, MR identified tumor spread into bone marrow, and it was superior to CT in five cases. Extension of tumor into the soft tissues adjacent to bone was shown better by MR than CT in six cases. Improved anatomic information from MR is the result of the ability to image in the axial, coronal, and sagittal planes. Compared with CT, MR identifies cortical disease but has inferior spatial resolution and defines calcium poorly. MR can be used to monitor tumor response to chemotherapy, and the relationship of tumor to adjacent vasculature can be determined without the use of contrast agents. Two pulse sequences are necessary for maximum display of disease, since, in general, tumor involvement of the bone marrow is best assessed on T1-weighted sequences, and tumor involvement of the soft tissue is best seen on T2-weighted sequences. Additional information about bone-marrow involvement, soft-tissue tumor extent, and the relationship of tumor to blood vessels makes MR a valuable adjunct to CT in the evaluation of these neoplasms.

Sixty-six percent of 54 patients with neuroblastoma demonstrated uptake of bone-seeking radioagents by the primary tumor. This is a higher incidence than previously reported. Uptake was slightly more common in abdominal than thoracic tumors. There was a significant correlation between the size of the tumor and tracer uptake. Calcification was demonstrated in the primary tumor in almost 90% of the 54 patients. This is a much higher incidence of calcification than previously reported. Microscopy shows that the calcification is not always due to tumor necrosis; it also occurs in areas of viable tumor cells. Tracer uptake is believed to be related to calcium metabolism. The rate of metabolic activity rather than the total amount of calcium present within the tumor may be the most important factor in determining the amount of uptake. No significant relationship was found between tracer uptake and tumor stage or homovanillic acid and vanillylmandelic acid metabolic activity.

Magnetic resonance imaging (MRI) in nine children with neuroblastoma showed that MRI can effectively demonstrate primary and metastatic disease and aid in predicting tumor resectability. MRI can show changes in tumor size and intensity in response to chemotherapy or radiation therapy. Neuroblastomas have an image intensity much lower than that of liver and muscle on inversion-recovery scans. On spin-echo 500/30 scans, the tumors have a greater intensity than muscle and a similar or slightly greater intensity than liver. On spin-echo 1000/60 scans, they are always of greater intensity than liver or muscle. At this stage, the overall accuracy of MRI as compared with other imaging methods is not known.