ABSTRACT
Imaging is intimately interlaced with radiation oncology. X-rays and, more recently, computed tomography (CT; Baker 1975; New et al. 1975; Reich and Seidelmann 1975), are the workhorses of tumor localization, which is an essential component of the radiation therapy (RT) process. Magnetic resonance imaging (MRI; Hawkes et al. 1980; Crooks et al. 1983) is essential for tumor localization in certain anatomical regions, particularly brain, because of its improved so«-tissue contrast. Currently, CT and MRI are the primary modalities used in the treatment process for determining patient and tumor anatomy. However, because disease progression and treatment response at the molecular and cellular levels precedes visible structural changes to tissue, “biological imaging” is receiving increasing attention as a method to understand disease progression and treatment response. Biological imaging does not have a precise de£nition. It encompasses virtually all imaging modalities and can be divided by the type of imaging processes into functional and molecular imaging. Note that the terms biological, molecular, and functional imaging are o«en used interchangeably, due to a lack of consensus regarding their de£nitions.
