Improvement of scintigraphic tumor imaging is extensively determined by the development of more tumor specific radiopharmaceuticals. Thus, to improve the differential diagnosis, prognosis, planning and monitoring of cancer treatment, several functional pharmaceuticals have been developed. The application of molecular targets for cancer imaging, therapy and prevention using generator-produced isotopes is the major focus of many ongoing research projects. Radionuclide imaging modalities (single photon emission computed tomography, SPECT; positron emission tomography, PET) are diagnostic cross-sectional imaging techniques that map the location and concentration of radionuclide-labeled radiotracers. Generator produced isotopes, such as 99mTc and 68Ga, are readily available and affordable. 99mTc (t1/2=6 hr; 140 keV) is used for SPECT and 68Ga (t1/2=68 min; 511 keV, 89%) is used for PET. 99mTc- and 68Ga-labeled agents using various chelators have been synthesized and their potential uses to assess tumor targets have been evaluated. Molecular targets labeled with 99mTc and 68Ga can be utilized for the prediction of therapeutic response, monitoring tumor response to treatment and aiding in the differential diagnosis of tumor versus non-tumor tissue. Molecular targets for oncological research in (1) cell apoptosis, (2) gene and nucleic acid-based approach, (3) angiogenesis (4) tumor hypoxia, and (5) metabolic imaging are discussed. Numerous imaging ligands in these categories have been developed and evaluated in animals and humans. Molecular targets were imaged and their potential to redirect optimal cancer diagnosis and therapeutics was demonstrated.
Keywords: PET, SPECT, molecular imaging