title: Validity of dual MRI and F-FDG PET imaging in predicting vulnerable and inflamed carotid plaque.
abstract: BACKGROUND
  Vulnerable and inflamed plaques in the carotid artery are at high risk of ischemic stroke, suggesting the importance of diagnostic modalities to detect them in patients with carotid stenosis with high sensitivity and specificity. Although many investigators have reported that magnetic resonance imaging (MRI) is a useful tool to predict the vulnerable components of carotid plaque, its validity is not established. On the other hand, (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) may be an alternative modality to directly identify the inflamed plaque in carotid artery stenosis. Therefore, this study aimed at evaluating the validity of MRI and FDG-PET to predict vulnerable and inflamed carotid plaque.
  
  
  METHODS
  This prospective study totally included 25 patients who underwent carotid endarterectomy (CEA) for carotid artery stenosis at our institute between January 2009 and January 2012. Prior to CEA, FDG-PET, black-blood T1-weighted imaging (BB-T1WI), and 3-dimensional time-of-flight (TOF) imaging were performed. The specimens were stained with hematoxylin-eosin to assess the different plaque components (lipid, hemorrhage, calcification, and fibrous tissue). In addition, they were stained with primary antibodies against CD68 (activated macrophages) and matrix metalloproteinase (MMP)-9.
  
  
  RESULTS
  High FDG uptake was detected in 13 (52.0%) of 25 patients. All of them had lipid-rich plaque. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) to identify the lipid-rich plaques were all 100% for FDG-PET. More importantly, all of the FDG-positive plaques had strong immunoreactivity against both CD68 and MMP-9. There was a significant correlation between the findings on FDG-PET and those on immunohistochemistry against CD68 and MMP-9 (p = 0.006 and 0.004, respectively). On the other hand, 16 (64.0%) of 25 patients had high signal intensity plaque on BB-T1WI. In 7 of these 16 patients, the lesions also showed high signal intensity on TOF imaging. All of them had a large intraplaque hemorrhage. The sensitivity, specificity, PPV, and NPV to identify a large intraplaque hemorrhage were 70, 100, 100, and 83%, respectively, for MRI.
  
  
  CONCLUSIONS
  These findings suggest that FDG-PET and MRI are complementary to predict high-risk carotid plaque, such as lipid-rich or hemorrhagic plaque. FDG-PET can accurately predict the lipid-rich and inflamed plaque. MRI is valuable to identify unstable plaque with a large intraplaque hemorrhage. The combination of these two modalities may play an important role in predicting carotid plaque at high risk of ischemic stroke.
authors: Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors: Hisayasu
authors: H
authors: Saito
authors: Satoshi
authors: S
authors: Kuroda
authors: Kenji
authors: K
authors: Hirata
authors: Keiichi
authors: K
authors: Magota
authors: Tohru
authors: T
authors: Shiga
authors: Nagara
authors: N
authors: Tamaki
authors: Daisuke
authors: D
authors: Yoshida
authors: Satoshi
authors: S
authors: Terae
authors: Naoki
authors: N
authors: Nakayama
authors: Kiyohiro
authors: K
authors: Houkin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000032:analysis; D002545:Brain Ischemia / Q000209:etiology; D002339:Carotid Arteries / Q000737:chemistry / Q000000981:diagnostic imaging* / Q000473:pathology*; D002340:Carotid Artery Diseases / Q000150:complications / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D016009:Chi-Square Distribution; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007150:Immunohistochemistry; D007249:Inflammation / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D058226:Plaque, Atherosclerotic; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D012422:Rupture, Spontaneous; D020521:Stroke / Q000209:etiology
chemical_list: D015415:Biomarkers; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18