title: PET/CT Imaging of Unstable Carotid Plaque with68Ga-Labeled Somatostatin Receptor Ligand.
abstract: 68Ga-labeled somatostatin receptor ligand PET imaging has recently been shown in preclinical and early human studies to have a potential role in the evaluation of vulnerable arterial plaques. We prospectively evaluated carotid plaque68Ga-DOTATATE uptake in patients with recent carotid events, assessed inter- and intraobserver variability of such measurements, and explored the mechanism of any plaque DOTATATE activity with immunohistochemistry in resected specimens.Methods:Twenty consecutively consenting patients with recent symptomatic carotid events (transient ischemic attack, stroke, or amaurosis fugax), due for carotid endarterectomy, were prospectively recruited.68Ga-DOTATATE PET/CT of the neck was performed before surgery.68Ga-DOTATATE uptake was measured by drawing regions of interest along the carotid plaques and contralateral plaques/carotid arteries by an experienced radionuclide radiologist and radiographer. Two PET quantification methods with inter- and intraobserver variability were assessed. Resected carotid plaques were retrieved for somatostatin receptor subtype-2 (sst2) immunohistochemical staining.Results:The median time delay between research PET and surgery was 2 d. SUVs and target-to-background ratios for the symptomatic plaques and the asymptomatic contralateral carotid arteries/plaques showed no significant difference (n= 19,P> 0.10), regardless of quantification method. The intraclass correlation coefficient was greater than 0.8 in all measures of carotid artery/plaque uptake (SUV) and greater than 0.6 in almost all measures of target-to-background ratio. None of the excised plaques was shown to contain cells (macrophages, lymphocytes, vessel-associated cells) expressing sst2 on their cell membrane.Conclusion:68Ga-DOTATATE activity on PET in recently symptomatic carotid plaques is not significantly different from contralateral carotids/plaques. Any activity seen on PET is not shown to be from specific sst2 receptor-mediated uptake in vitro. It is therefore unlikely that sst2 PET/CT imaging will have a role in the detection and characterization of symptomatic carotid plaques.
authors.affiliation: Institute of Nuclear Medicine, University College London, London, United Kingdom mwan@nhs.net.
authors.forename: Ming Young Simon
authors.initials: MYS
authors.lastname: Wan
authors.affiliation: Institute of Nuclear Medicine, University College London, London, United Kingdom.
authors.forename: Raymond
authors.initials: R
authors.lastname: Endozo
authors.affiliation: Institute of Nuclear Medicine, University College London, London, United Kingdom.
authors.forename: Sofia
authors.initials: S
authors.lastname: Michopoulou
authors.affiliation: Institute of Nuclear Medicine, University College London, London, United Kingdom.
authors.forename: Robert
authors.initials: R
authors.lastname: Shortman
authors.affiliation: Department of Histopathology, University College London, London, United Kingdom.
authors.forename: Manuel
authors.initials: M
authors.lastname: Rodriguez-Justo
authors.affiliation: Institute of Nuclear Medicine, University College London, London, United Kingdom.
authors.forename: Leon
authors.initials: L
authors.lastname: Menezes
authors.affiliation: Department of Vascular Surgery, Brighton and Sussex University Hospitals, Sussex, United Kingdom.
authors.forename: Syed
authors.initials: S
authors.lastname: Yusuf
authors.affiliation: Department of Vascular Surgery, University College London, London, United Kingdom.
authors.forename: Toby
authors.initials: T
authors.lastname: Richards
authors.affiliation: Division of Nuclear Medicine, University of Basel Hospital, Basel, Switzerland; and.
authors.forename: Damian
authors.initials: D
authors.lastname: Wild
authors.affiliation: Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Berne, Switzerland.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Waser
authors.affiliation: Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Berne, Switzerland.
authors.forename: Jean Claude
authors.initials: JC
authors.lastname: Reubi
authors.affiliation: Institute of Nuclear Medicine, University College London, London, United Kingdom.
authors.forename: Ashley
authors.initials: A
authors.lastname: Groves
mesh_terms: D000368:Aged; D016893:Carotid Stenosis / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008297:Male; D057054:Molecular Imaging / Q000379:methods*; D015588:Observer Variation; D009942:Organometallic Compounds / Q000493:pharmacokinetics*; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D017481:Receptors, Somatostatin / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; C513399:gallium Ga 68 dotatate
keywords: DOTATATE; PET/CT; carotid; somatostatin; vulnerable plaques