The primary aim of this proposal is to serially evaluate imaging tests in previously untreated patients with osteosarcoma, Ewing's Sarcoma Family of Tumors(ESFT), rhabdomyosarcoma and intermediate and high-risk non-rhabdomyosarcoma soft tissue sarcomas whose planned treatment includes a cumulative doxorubicin dose ≥ 375 mg/m2 to determine if serial levels of one or more of these potential markers of cardiac muscle injury obtained prior to each infusion of doxorubicin and at the completion of chemotherapy correlate with increasing cumulative anthracycline exposure.