A study of plaque vascularization and inflammation using quantitative contrast-enhanced US and PET/CT.
BACKGROUND
Contrast-enhanced ultrasound (CEUS) is an in vivo methodology to quantify carotid plaque vascularization. Increased metabolism in plaques, measured as FDG uptake in PET/CT examination, has been associated with markers of inflammation in histological samples. In this study, we tested the association between FDG uptake and vascularization measured by CEUS to assess whether CEUS can be used as an in vivo marker of plaque vulnerability.


METHODS
After informed consent, subjects aged >60 years with carotid plaque height exceeding 2.5mm were recruited. CEUS was performed and analyzed using earlier described protocol and software, Contrast Quantification Program, which calculates the fraction of the plaque being contrast positive (CQP value). PET/CT examination was performed within 3 months of CEUS (median time 7 days). PET/CT images were acquired 90 min after FDG injection (2.7 MBq/kg). FDG uptake was measured as tissue background index (TBI), calculated using Spearman's rho as mean standard uptake value (SUV) of the plaque divided by mean SUV in the jugular vein (mean of 7 measuring points). Local ethics committee approved the study.


RESULTS
We recruited 13 subjects (5 women) with a mean age of 71 years, 6 had a history of stroke or TIA, 1 had a history of ipsilateral stroke. CQP values showed a significant, positive correlation with TBI of carotid plaques, r=0.67, p<0.02.


CONCLUSIONS
Plaque vascularization measured by CEUS correlates positively with FDG uptake measured by PET/CT in humans. This indicates an association between vascularization and inflammation and/or hypoxia, supporting the use of CEUS as a non-invasive method to detect plaque vulnerability.
Institute of Medicine, Sahlgrenska Academy at the University of Gothenburg, Department of Molecular and Clinical Medicine, Clinical Physiology, Gothenburg, Sweden; Sahlgrenska University Hospital, Department of Clinical Physiology, Gothenburg, Sweden. Electronic address: ola.hjelmgren@wlab.gu.se.
Ola
O
Hjelmgren
Uppsala University, Department of Radiology, Uppsala, Sweden. Electronic address: lars.johansson@radiol.uu.se.
Lars
L
Johansson
Institute of Medicine, Sahlgrenska Academy at the University of Gothenburg, Department of Molecular and Clinical Medicine, Clinical Physiology, Gothenburg, Sweden. Electronic address: ulrica-prahl-gullberg@wlab.gu.se.
Ulrica
U
Prahl
Institute of Medicine, Sahlgrenska Academy at the University of Gothenburg, Department of Molecular and Clinical Medicine, Clinical Physiology, Gothenburg, Sweden. Electronic address: caroline.schmidt@wlab.gu.se.
Caroline
C
Schmidt
Sahlgrenska University Hospital, Department of Clinical Physiology, Gothenburg, Sweden. Electronic address: johan.freden-lindqvist@vgregion.se.
Johan
J
Fredén-Lindqvist
Institute of Medicine, Sahlgrenska Academy at the University of Gothenburg, Department of Molecular and Clinical Medicine, Clinical Physiology, Gothenburg, Sweden; Sahlgrenska University Hospital, Department of Clinical Physiology, Gothenburg, Sweden. Electronic address: goran.bergstrom@hjl.gu.se.
Göran M L
GML
Bergström
D000368:Aged; D002340:Carotid Artery Diseases / Q000175:diagnosis* / Q000378:metabolism*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014463:Ultrasonography / Q000379:methods*
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
Carotid artery plaque; Positron-emission tomography; Ultrasound