64Cu-DOTATATE PET/MRI for Detection of Activated Macrophages in Carotid Atherosclerotic Plaques

All patients referred to our institution for carotid endarterectomy were screened for inclusion. Inclusion criteria were significant carotid stenosis with recent cerebrovascular symptoms; stroke, amaurosis fugax or TIA. Exclusion criteria were age <50 years, current infection, pregnancy, renal insufficiency, or severe claustrophobia. All patients underwent two simultaneous PET/MR procedures after one injection of a mean of 154 MBq of 64 Cu-DOTATATE. An early PET/MR was performed a median of 85 minutes (range: 56-90 min) after injection and the late PET/MR was performed a median of 299 minutes (range: 265-428 min) after injection. Carotid endarterectomy was performed the following day using standard clinical procedure. The plaque specimens were conserved for later gene expression analysis. The study was approved by the Regional Scientific Ethical Committee (protocol H-4-2012-064) and all patients received oral and written information about the study and signed an informed consent prior to inclusion. In-vivo PET/MR acquisition Simultaneous PET/MR was performed on the Biograph mMR 1 (Siemens Healthcare, Erlangen, Germany) using the mMR standard PET compatible dedicated head and neck coil (Siemens Healthcare). Patients were placed in the scanner in the supine position and scout images were obtained for localization of the carotid arteries. An mMR standard Dixon water-fat MR sequence was then recorded and segmented (into air, lung tissue, soft tissue and fat) for MR-based PET attenuation correction 2. PET acquisition was started along with the Dixon MR sequence. Acquisition time was 10 min in three-dimensional list-mode (scanner default list mode recording) in one bed position. A 3D time-of-flight (TOF) magnetic resonance angiography sequence was then performed to obtain lumen contours. MR parameters for 3D-TOF were: TR/TE 21/3.6 ms, voxel size 0.8×0.5×1.0 mm 3. Next, a stack of 14 axial 2D turbo spin echo dark blood slices (thickness 2.2 mm, gap 0.88 mm, field of view 150 mm) with fat suppression and proton density, T1 and T2 weightings was placed using the 3D-TOF angiography. Images were centered at the stenotic area. MR parameters were: T1-weighted: TR/TE=1,060/26 ms, voxel size 0.6×0.6 mm 2. T2-weighted: TR/TE=2,500/76 ms, voxel size 0.6×0.6 mm 2. Proton density-weighted: TR/TE=2,400/16 ms, voxel size 0.4×0.4 mm 2. For detailed MR parameters of 3D TOF, T1, T2 and proton density-weighted sequences see supplementary material. On average, the total examination time was below 30 minutes. The carorid artery was analyzed slice by slice on transaxial images in every subject guided by T1, T2, TOF and PD images by the …