Immuno-SPET/CT and immuno-PET/CT: a step ahead to translational imaging.

Malignant tumours have the remarkable property to express cell surface antigens. Pressman was first reporting that radiolabeled antibodies were capable of organ localization. It was a promising challenge but the expected success and the development of this imaging method was limited by a poor imaging resolution despite a rather good specificity of the antibodies used. Identification of key cell surface markers is opening a new era as potential molecular imaging biomarkers in oncologic applications. Antibodies production has been promoted by the development of engineered fragments with preserved immunological properties and pharmacokinetics optimized for molecular imaging. A good compromise has to be obtained between the biological properties of the antibody and the physical half-life of the radionuclide. Several positron emission tomography (PET) radionuclides such as iodine-124, copper-64, yttrium-86 or zirconium-89 have been the focus of recent immuno-PET studies with interesting informative images in preclinical and clinical studies. Thanks to the development of more sensitive new detectors and specific software, molecular imaging methods, particularly PET imaging, allow nowadays the detection of lesions smaller than 5 mm in human. Immuno-PET can potentially be used for tumour detection and identification at diagnosis, staging and restaging, for treatment selection and monitoring, and during follow-up. Moreover the availability of matched imaging or therapeutic radionuclide pairs, such as (124)I/(131)I, (64)Cu/(67)Cu and (86)Y/(90)Y, make easier the quantification of tissue uptake and dosimetry calculation for radioimmunotherapy.

Molecular targeting of the lymphovascular system for imaging and therapy.

Progress toward targeting cancer cells is a multi-disciplinary endeavor. In addition to the surgical and oncology specialties, radiologists collaborate with mathematicians, computer scientists, and physicists, in a constant effort to incrementally improve upon the current imaging modalities. Recently, radiologists have formed collaborations with molecular biologists and chemists in order to develop molecular agents that target cancer cells via receptor-substrate or specific physiochemical interactions. In this review, we summarize selected efforts toward molecular targeting of the lymphovascular system. Standard imaging modalities, positron emission tomography, single photon emission tomography, and ultrasound, are reviewed as well as, the targeted introduction of substances for endolymphatic therapy. We also review the current status of sentinel lymph node mapping with radiocolloids and the application of molecular targeting for the development of a radiopharmaceutical specifically designed for sentinel lymph node mapping.