Advances in MR imaging of pediatric musculoskeletal neoplasms.

MR imaging has evolved as the most important diagnostic test for local staging of primary bone and soft tissue tumors, for monitoring response to chemotherapy, and for detecting postoperative tumor recurrence. MR imaging provides accurate preoperative staging of local tumor extent and helps to obtain adequate safety margins, prerequisites for successful limb-salvage surgery. Postcontrast MR imaging studies are helpful for evaluating the presence or absence of tumor necrosis during chemotherapy. Dynamic MR imaging after intravenous bolus administration of Gd-DTPA or other paramagnetic contrast media is particularly useful for assessing response to chemotherapy. Diffusion-weighted MR imaging is a new technique that is potentially capable of detecting and quantitating the amount of tumor necrosis after chemotherapy or radiation therapy.