4D-PET/CT with [(11)C]-PK11195 and [(11)C]-(D)-deprenyl does not identify the chronic inflammation in asymptomatic...

The aim of this study was to investigate the relevance of inflammation in the pathogenesis of abdominal aortic aneurysm (AAA) in vivo with two novel positron emission tomography (PET) tracers: [(11)C]-PK11195 which targets the translocator protein (18 kDa) expressed on macrophages and [(11)C]-d-deprenyl with a yet unknown target receptor expressed in chronic inflammation.

Prospective clinical study.

Five patients were examined with [(11)C]-PK11195-positron emission tomography/computed tomography (PET/CT) and 10 with [(11)C]-d-deprenyl-PET/CT. Nine large AAAs (54-66 mm) scheduled for repair and six small AAA (35-44 mm). All 15 patients were male and the AAAs were all asymptomatic. Regional activity was measured as standardised uptake values (SUVs) and retention index was calculated. Biopsies were taken from the aneurysm wall for histological examinations, in the nine patients operated on.

No aortic uptake was recorded on the visual inspection, neither with [(11)C]-PK11195 nor with [(11)C]-d-deprenyl. For [(11)C]-PK11195 the median SUV of the AAA wall was 0.9 (range 0.8-1.0) and for [(11)C]-d-deprenyl, 0.7 (range 0.4-1.2). No increased uptake was seen in the aneurysmal infrarenal aorta compared with the non-aneurysmal suprarenal aorta. Histological examination of the aneurysm wall showed high inflammatory cell infiltration with lymphocytes and macrophages.

The chronic inflammation observed in the vessel wall was not detectable with [(11)C]-PK11195 and [(11)C]-d-deprenyl. In order to study the relevance of the inflammation in the pathogenesis of AAA in vivo other PET tracers need to be investigated.