Advances in imaging: target delineation.

Modern radiation oncology relies heavily on emerging technology. In this article, we review recent advances in target delineation as it applies to radiation treatment planning. We focus on the evidence to support methionine positron emission tomography use for target delineation in primary brain tumors, 2-deoxy-2-[(18)F] fluoro-D-glucose positron emission tomography use for target delineation for lung cancer and head and neck cancer, and the use of magnetic resonance imaging sequences for target delineation in prostate cancer.