18F-choline positron emission tomography (PET)/computed tomography (CT) is an integral part in restaging of patients with prostate cancer (PC). The aim of this study was to describe the whole-body physiologic distribution of 18F-choline and to discuss some abnormal sites of uptake not related to PC we observed. Eighty consecutive patients submitted to 18F-choline PET/CT imaging for primary staging or biochemical recurrence (prostate specific antigen rising) after treatment of PC was considered. Whole-body PET/CT was acquired approximately 40 min after 18F-choline injection. We observed physiological 18F-choline uptake in liver, pancreas, spleen, salivary and lachrymal glands and also, owing to renal excretion, in urinary tract. Other sites of less intense tracer uptake were bone marrow and intestines. We found abnormal and unexpected PET findings in 15 patients (18.7%), not owing to PC localizations. The majority of these findings were owing to inflammation (12 of 15); a case of low grade lymphoma was detected; two patients showed focal brain uptake of 18F-choline and were subsequently submitted to magnetic resonance: in one a meningioma and in the other a low-grade brain tumour were diagnosed. Accurate knowledge of the biodistribution of 18F-choline is essential for the correct interpretation of PET/CT imaging. CT enables differentiation of physiological bowel activity and 18F-choline excretion in the ureters. In our series, 18F-choline uptake in benign pathological conditions mainly included sites of inflammation; nevertheless, accumulation in tumour deposits not because PC cannot be excluded, particularly in the brain, where correlative imaging with magnetic resonance is of the utmost importance.

To assess the usefulness of a hybrid imaging system (single-photon emission computed tomography/computed tomography, SPECT/CT) for functional anatomical mapping (FAM) using various radiotracers and the additional value of fused SPECT/CT images compared with SPECT alone. Eighty-one consecutive patients studied for various clinical situations were evaluated: 10 with 111In-pentetreotide, four with 123I-meta-iodobenzylguanidine (I-MIBG), five with 99mTc-labelled red blood cells, two with 99mTc-antigranulocyte antibodies, four with 99mTc-nanocolloids, 10 with 67Ga, seven with 99mTc-methylene diphosphonate (99mTc-MDP), nine with 99mTc-sestamibi, 21 with 99mTc-tetrofosmin, two with 201Tl, three with 99mTc-ethylcysteinate dimer (ECD), one with 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) and three with 123I-N-w-fluoropropyl-2-beta-carbomethoxy-3-beta-(4-iodophenyl) nortropanel (FPCIT). The acquisition of both anatomical (CT) and functional (SPECT) data was performed during a single session. SPECT data were first interpreted alone and then re-evaluated with the addition of FAM. Transmission anatomical maps allowed for the precise anatomical localization of SPECT images in 79 of the 81 cases. SPECT/CT had a significant impact on the results in 33 (40.7%) of the 81 patients: FAM provided the correct localization of SPECT findings in 23 cases, allowed the definition of the functional significance of CT lesions in two and enabled the exclusion of disease in sites of physiological tracer uptake in eight. SPECT/CT with this hybrid system is a feasible technique yielding co-registered dual-modality images. FAM allows a more precise interpretation of scintigraphic studies in several cases and fused images can improve the diagnostic accuracy of SPECT in various clinical situations.

Introduction: Theranostics is an emerging field in which diagnosis and specific targeted therapy are combined to achieve a personalized treatment approach to the patient. In nuclear medicine clinical practice, theranostics is often performed utilizing the same molecule labeled with two different radionuclides, one radionuclide for imaging and another for therapy. Areas covered: The authors review the clinical applications of different radiopharmaceuticals in the field of interest, including the well-established use of radioactive iodine in differentiated thyroid cancer, radiolabeled metaiodobenzylguanidine (MIBG) in neuroblastoma and the clinical impact of peptide radionuclide receptorial therapy (PRRT) in the management of neuroendocrine tumors. Furthermore, the more cutting-edge and recently introduced theranostic approaches will be reviewed, such as the radioligand therapy with ¹⁷⁷Lu-prostate specific membrane antigen (PSMA) and targeted alpha therapy in castration resistant prostate cancer. Finally, the main applications of PET for the imaging of biomarkers suitable for the non-radionuclide targeted therapy will be covered. Expert opinion: Theranostics is envisaging a revolutionary clinical approach which is deeply connected with the concept of personalized medicine and ruled by a “patient-centered” vision. In this perspective, the theranostic applications will need well-trained specialists, capable to manage not only the technological aspects of the discipline, but also to deal with the more innovative oncological therapies in a multidisciplinary setting.