Clinical Molecular Imaging for Atherosclerotic Plaque

Atherosclerosis is a well-known disease leading to cardiovascular events, including myocardial infarction and ischemic stroke. These conditions lead to a high mortality rate, which explains the interest in their prevention, early detection, and treatment. Molecular imaging is able to shed light on the basic pathophysiological processes, such as inflammation, that cause the progression and instability of plaque. The most common radiotracers used in clinical practice can detect increased energy metabolism (FDG), macrophage number (somatostatin receptor imaging), the intensity of cell proliferation in the area (labeled choline), and microcalcifications (fluoride imaging). These radiopharmaceuticals, especially FDG and labeled sodium fluoride, can predict cardiovascular events. The limitations of molecular imaging in atherosclerosis include low uptake of highly specific tracers, possible overlap with other diseases of the vessel wall, and specific features of certain tracers’ physiological distribution. A common protocol for patient preparation, data acquisition, and quantification is needed in the area of atherosclerosis imaging research.

Use of 18F-FDG PET/CT to Differentiate Ectopic Adrenocorticotropic Hormone-Secreting Lung Tumors From Tumor-Like Pulmonary Infections in Patients With Ectopic Cushing Syndrome

BackgroundEctopic adrenocorticotropic hormone (ACTH)-secreting lung tumors represent the most common cause of ectopic Cushing syndrome (ECS). Pulmonary opportunistic infections are associated with ECS. The present study aimed to evaluate the usefulness of 18F-FDG PET/CT for differentiating ectopic ACTH-secreting lung tumors from tumor-like pulmonary infections in patients with ECS.MethodsWe retrospectively reviewed the imaging data of 24 patients with ECS who were suspected to have ACTH-secreting lung tumors and underwent 18F-FDG PET/CT between 2008 and 2019. Eleven patients with lung tumors and 4 with pulmonary infections also had additional somatostatin receptor imaging (99mTc-HYNIC-TOC SPECT/CT or 68Ga-DOTATATE PET/CT).ResultsIn total, 18 patients had lung tumors and six had pulmonary infections. The primary source of ECS remained occult in the six patients with pulmonary infections. The maximum standardized uptake value (SUVmax) for pulmonary infections was significantly higher than that for tumors (P = 0.008). Receiver operating characteristic analysis revealed that a cut-off SUVmax of 4.95 helped in differentiating ACTH-secreting lung tumors from infections with 75% sensitivity and 94.4% specificity. For the 11 patients with ACTH-lung tumors, somatostatin receptor imaging (SRI) was positive in 6; while for the 4 with pulmonary infections, SRI was positive in 2. The sensitivity and specificity of somatostatin receptor imaging (SRI) for detecting ACTH-secreting lung tumor was 54.5% and 50%.ConclusionsOur findings suggest that pulmonary infections exhibit significantly higher FDG uptake than ACTH-secreting lung tumors in 18F-FDG PET/CT. An SUVmax cut-off value of 4.95 may be useful for differentiating the two conditions. Our results also suggested that SRI may not be an effective tool for differentiating the two conditions given the relatively low specificity.

Hybrid SPECT/CT Somatostatin Receptor Imaging of Neuroendocrine Tumours

Cilj: Cilj rada bio je procijeniti doprinos jednofotonske emisijske tomografije / kompjutorizirane tomografije somatostatinskih receptora (SR SPECT/CT) s 99mTc-EDDA/HYNIC-Tyr3-oktreotidom (99mTc-Tektrotyd) u dijagnostici i procjeni proširenosti bolesti kod pacijenata oboljelih od neuroendokrinih tumora (NET-ova). Ispitanici i metode: Retrospektivno je analizirano 120 SR SPECT/CT snimanja pacijenata s patohistološki dokazanim NET-om s obzirom na vizualizaciju primarnih lezija i metastaza. U 45 pacijenata učinjena je i pozitronska emisijska tomografija 18F-fluorodeoksiglukozom (18F-FDG PET/CT) te su nalazi uspoređeni s nalazima SR SPECT/CT-a i vrijednostima kromogranina A. Rezultati: Od 120 pacijenata 47 (39 %) je na SR SPECT/CT upućeno nakon odstranjenja primarne lezije. Od preostala 73 pacijenta (61 %), u 56 (77 %) primarni je tumor bio vidljiv SR SPECT/CT-om, a u 9 (12 %) poznata lezija nije akumulirala radiofarmak. U 8 (11 %) pacijenata s NET-om nepoznatog primarnog sijela nalaz je bio negativan. Od 68 (57 %) pacijenta s dokazanim metastazama, u njih 57 (84 %) bile su vidljive SR SPECT/CT-om, a u 11 (16 %) nisu akumulirale radiofarmak. Od 45 (38 %) pacijenata kojima je učinjen i 18F-FDG PET/CT, u 27 (60 %) detekcija primarnih lezija i metastaza bila je sukladna nalazu SR SPECT/CT-a. Osjetljivost SR SPECT/CT-a bila je 77 % za primarne lezije i 84 % za metastaze, a 18F-FDG PET/CT-a 75 % za primarne lezije i 76 % za metastaze. Vrijednosti kromogranina A nisu pokazale statistički signifikantnu korelaciju s nalazima slikovne dijagnostike. Zaključci: SR SPECT/CT ima visoku osjetljivost za detekciju NET-ova. Osim toga, potvrđena je komplementarnost s 18F-FDG PET/CT-om te kod pacijenata s negativnim nalazom SR SPECT/CT-a treba učiniti 18F-FDG PET/CT i obrnuto.

Neuroendokrine Tumoren im Gastrointestinaltrakt

Neuroendocrine neoplasms (NEN) are increasingly diagnosed tumors with great clinical and prognostic heterogeneity. One of the peculiarities of NEN is the presence of a clinical hormone syndrome in about 30 % of cases. Somatostatin receptor imaging plays an important role in the diagnosis of spreading and in the planning of therapy. NEN patients should be co-supervised by specialized centers and if possible treated as part of studies. In the case of NEN with no or only circumscribed metastases, complete resection in curative intention is generally the highest therapeutic goal. Small neuroendocrine tumors (NET) G1 of the stomach, duodenum and rectum can be curatively endoscopically resected. In the case of a metastatic, non-curative disease, an antiproliferative therapy with the aim of growth control takes place. In patients with functionally active tumors, an antisecretory or symptomatic therapy is used to control the hormone syndrome. The treatment of metastatic NET is often multimodal and must be established by an experienced interdisciplinary team. The prognosis of NEN is mainly determined by the stage at the time of diagnosis, tumor differentiation, grading and localization of the primary tumor.