ABSTRACT
There are a number of imaging techniques that can be used for external detection of either anatomical or physiological changes in animals and humans. The anatomical techniques are important for determining the size, shape, and position of abnormalities with high resolution and the measurement of the longest dimension of the tumor by X-ray is the gold standard for tumor regression (RECIST). Positron emission tomography (PET) was developed using the short-lived radionuclides of oxygen, nitrogen, carbon, and fluorine. Their advantage in radiolabeling small molecules was readily recognized because these radionuclides represent the smallest perturbation of the chemical structure, whereas single-photon computed tomography (SPECT) radiotracers, magnetic resonance imaging (MRI) contrast agents, and fluorescent reporter probes create larger perturbations, in general. PET has been to measure blood volume (BV) using -labeled red blood cells, blood flow (BF) using -labeled water, and permeability (P) of tumors in oncology.
