The main purpose of this study is to determine if PET-imaging can be used to evaluate inflammation level of intracranial aneurysms, thus helping to evaluate the rupture risk of intracranial aneurysm.

Study subjects are patients who are diagnosed with an unruptured saccular intracranial aneurysm and planned for elective surgical treatment of intracranial aneurysms. Prior the planned surgery, all study subjects will undergo PET-imaging of the brain with 18F-FDG- and 68Ga-DOTANOC-tracers targeting glucose metabolism and somatostatin receptors in inflammatory cells. After PET-imaging, samples for histopathological examination from the intracranial aneurysm sac will be collected during the surgery from every study subject. Blood samples are collected prior to aneurysm operation from the routine pre-operative laboratory tests. Cerebrospinal fluid samples are collected during the surgical procedure from the surgical site. From blood samples we will evaluate expression of 20 different circulating microRNAs (miRNA) and the level of tumor necrosis factor-1, interleukin 1 beta, vascular endothelial growth factor, and evaluate correlations between miRNA expression and SUVmax in PET-imaging and miRNA and aneurysm histological findings.

Correlation between inflammatory findings in histological studies and PET-imaging will be evaluated (correlation of SUVmax to aneurysm histological findings).

Inclusion Criteria:

• Fusiform intracranial aneurysms
• Following medications: Asetylsalisylic acid or non-steroidal anti-inflammatory drugs.
• Patients who have contraindication for magnetic resonance imaging (Pace Makers, foreign ferromagnetic bodies or implants)
• Patients who are allergic to contrast agents.
• Pregnancy
• Underage persons
• Patients on somatostatin analogue medication or with known neuroendocrine tumor

Exclusion Criteria:

• Patients who are diagnosed with unruptured intracranial aneurysm with MRI/MRA or DSA
• Patients who are planned to undergo surgical treatment (ligation) of the intracranial aneurysm
• Age ≥18 and <75 years.
• Saccular intracranial aneurysm with maximum diameter ≥ 3 mm.