Development of Antibody Immuno-PET/SPECT Radiopharmaceuticals for Imaging of Oncological Disorders-An Update.

Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are molecular imaging strategies that typically use radioactively labeled ligands to selectively visualize molecular targets. The nanomolar sensitivity of PET and SPECT combined with the high specificity and affinity of monoclonal antibodies have shown great potential in oncology imaging. Over the past decades a wide range of radio-isotopes have been developed into immuno-SPECT/PET imaging agents, made possible by novel conjugation strategies (e.g., site-specific labeling, click chemistry) and optimization and development of novel radiochemistry procedures. In addition, new strategies such as pretargeting and the use of antibody fragments have entered the field of immuno-PET/SPECT expanding the range of imaging applications. Non-invasive imaging techniques revealing tumor antigen biodistribution, expression and heterogeneity have the potential to contribute to disease diagnosis, therapy selection, patient stratification and therapy response prediction achieving personalized treatments for each patient and therefore assisting in clinical decision making.

Usefulness of Splenic Scintigraphy in Differentiating Splenosis and Malignancy on Gallium 68 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-NaI3-octreotide.

Somatostatin receptor (SSTR) imaging with gallium 68 (Ga-68) 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-peptide positron emission tomography/computed tomography (PET/CT) has been introduced in clinical routine for the diagnosis and staging of neuroendocrine tumors (NETs) with high SSTR expression. Although it has high sensitivity for NETs, there are some known diagnostic pitfalls one should be aware of. We present a case of suspected NET where Ga-68 DOTA-NaI3-octreotide (NOC) PET/CT showed several abdominal lesions with high SSTR expression suggesting malignancy. On magnetic resonance imaging, the differential diagnosis of the lesions also included splenosis. Subsequent splenic scintigraphy with technetium-99m phytate showed uptake in all suspicious lesions, and biopsy confirmed the diagnosis of splenosis. Splenic scintigraphy with single-photon emission computed tomography/CT can be a helpful noninvasive diagnostic tool when splenosis is suspected on Ga-68 DOTA-peptide PET/CT.