The purpose of this study is to test the usefulness of imaging with radiolabeled methionine
in the evaluation of children and young adults with tumor(s). Methionine is a naturally
occurring essential amino acid. It is crucial for the formation of proteins. When labeled
with carbon-11 (C-11), a radioactive isotope of the naturally occurring carbon-12, the
distribution of methionine can be determined noninvasively using a PET (positron emission
tomography) camera. C-11 methionine (MET) has been shown valuable in the monitoring of a
large number of neoplasms. Since C-11 has a short half life (20 minutes), MET must be
produced in a facility very close to its intended use. Thus, it is not widely available and
is produced only at select institutions with access to a cyclotron and PET chemistry
facility. With the new availability of short lived tracers produced by its PET chemistry
unit, St. Jude Children's Research Hospital (St. Jude) is one of only a few facilities with
the capabilities and interests to evaluate the utility of PET scanning in the detection of
tumors, evaluation of response to therapy, and distinction of residual tumor from scar tissue
in patients who have completed therapy. The investigators propose to examine the
biodistribution of MET in patients with malignant solid neoplasms, with emphasis on central
nervous system (CNS) tumors and sarcomas. This project introduces a new diagnostic test for
the noninvasive evaluation of neoplasms in pediatric oncology. Although not the primary
purpose of this proposal, the investigators anticipate that MET studies will provide useful
clinical information for the management of patients with malignant neoplasms.