Figure 1.
Construction of an antibody-based molecular imaging probe requires a contrast agent specific for the imaging modality. Full and fragmented antibodies may be employed as targeting agents. Some examples of antibody fragments include F(ab′)2, Fab, single-chain variable fragment (ScFv), and nanobody (sdAb). Radioisotopes are employed for positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging. Fluorescent dyes and quantum dots are utilized for optical and photoacoustic (PA) imaging. Magnetic (e.g., iron oxide) nanoparticles are commonly used in magnetic resonance imaging (MRI).