J Clin Neurol.  2013 Jul;9(3):176-185. 10.3988/jcn.2013.9.3.176.

Complementarity between 18F-FDG PET/CT and Ultrasonography or Angiography in Carotid Plaque Characterization

• Noh SM
• Choi WJ
• Kang BT
• Jeong SW
• Lee DK
• Schellingerhout D
• Yeo JS
• Kim DE

• KMID: 2287556
• DOI: http://doi.org/10.3988/jcn.2013.9.3.176

Abstract

BACKGROUND AND PURPOSE
To estimate clinical roles of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) versus angiography and ultrasonography in carotid plaque characterization.
METHODS
We characterized two groups of patients with recently (<1 month) symptomatic (n=14; age=71.8+/-8.6 years, mean+/-SD) or chronic (n=13, age=68.9+/-9.0 years) carotid stenosis using a battery of imaging tests: diffusion magnetic resonance (MR) imaging, MR or transfemoral angiography, duplex ultrasonography (DUS), and carotid FDG-PET/computed tomography.
RESULTS
The degree of angiographic stenosis was greater in patients with recently symptomatic carotid plaques (67.5+/-21.5%) than in patients with chronic carotid plaques (32.4+/-26.8%, p=0.001). Despite the significant difference in the degree of stenosis, lesional maximum standardized uptake values (maxSUVs) on the carotid FDG-PET did not differ between the recently symptomatic (1.56+/-0.53) and chronic (1.56+/-0.34, p=0.65) stenosis groups. However, lesional-to-contralesional maxSUV ratios were higher in the recently symptomatic stenosis group (113+/-17%) than in the chronic stenosis group (98+/-10%, p=0.017). The grayscale median value of the lesional DUS echodensities was lower in the recently symptomatic stenosis group (28.2+/-10.0, n=9) than in the chronic stenosis group (53.9+/-14.0, n=8; p=0.001). Overall, there were no significant correlations between angiographic stenosis, DUS echodensity, and FDG-PET maxSUV. Case/subgroup analyses suggested complementarity between imaging modalities.
CONCLUSIONS
There were both correspondences and discrepancies between the carotid FDG-PET images and DUS or angiography data. Further studies are required to determine whether FDG-PET could improve the clinical management of carotid stenosis.

Keyword

carotid plaque; FDG-PET/CT; angiography; ultrasonography; molecular imaging; atherosclerosis

MeSH Terms

Angiography
Atherosclerosis
Carotid Stenosis
Constriction, Pathologic
Diffusion
Fluorodeoxyglucose F18
Humans
Magnetic Resonance Spectroscopy
Molecular Imaging
Positron-Emission Tomography
Fluorodeoxyglucose F18

Figure

• 

  Fig. 1 FDG-PET/CT, angiography, and ultrasonography in carotid plaque characterization: study methods (A) and results (B-F). The box plots show the median as a horizontal line within the box, upper and lower quartiles as the upper and lower limits of the box, and the largest and smallest values as whiskers. The p values were obtained using the Mann-Whitney test (B, C and D) or Spearman's correlation (E and F). GSM: grayscale median, maxSUV: maximum standardized uptake value.

• 

  Fig. 2 Symptomatic echolucent plaques having a higher FDG-PET uptake than asymptomatic mixed-echoic plaques. Diffusion MRI reveals embolic cortical and subcortical infarcts in the right hemisphere (A). Conventional angiography (B) and DUS (C and D) show that the ipsilesional carotid plaque causing significant luminal narrowing (B, *) has mostly a low echodensity (C, yellow arrowheads). Compared with the culprit plaques with a high FDG uptake (E, yellow arrows), no FDG-PET signal is evident in the contralateral carotid artery with asymptomatic plaques (E, white arrows) having mixed echodensity on DUS (D, white arrowheads). DUS: duplex ultrasonography, ICA: internal carotid artery.

• 

  Fig. 3 Asymptomatic plaques with a relatively high FDG-PET uptake. Diffusion MRI shows that cortical and subcortical infarcts are scattered in the left hemisphere (A). Conventional angiography (B) and DUS (C and D) show that ipsilateral carotid plaques with significant luminal narrowing have low and mixed echodensity (C, yellow arrowheads). Compared with the culprit plaques (E, yellow arrows), contralateral echogenic plaques on DUS (D, white arrowheads) have a relatively high FDG uptake (E, white arrows). DUS: duplex ultrasonography.

• 

  Fig. 4 Focal FDG-PET uptake restricted to a distal portion of a stenotic carotid artery lesion. Diffusion MRI shows embolic cortical border-zone infarcts in the left hemisphere (A). FDG uptake is restricted to the distal end of the diffusely stenotic left proximal internal carotid artery (B and C; red arrows and red arrowhead, respectively).

• 

  Fig. 5 FDG-PET uptake not restricted to the most stenotic area of a symptomatic carotid artery. Diffusion MRI (A) and conventional angiography (B) show an ischemic infarction in the left frontal cortex, probably due to embolism from the severely stenotic atheromatous lesion in the left proximal ICA (B, red arrowhead), where strong FDG-PET uptake is evident (C, red arrows). However, similarly strong FDG-PET uptake is evident in the bilateral CCAs (C, blue arrows) and contralesional asymptomatic ICA (C, yellow arrow). CCA: common carotid artery, ICA: internal carotid artery.

• 

  Fig. 6 Complementarity between carotid imaging modalities. Diffusion MRI shows that several subcortical infarcts are scattered in the left hemisphere (A). On CT angiography, the proximal left ICA appears occluded (B, white arrowhead to yellow arrow). However, on carotid DUS, cephalad arterial flow is evident inside the lumen (*) distal to the distal edge (C, yellow arrow) of the patent but severely stenotic ICA. DUS also visualizes three echolucent plaque areas (D): below *, #, and white arrowhead. FDG-PET/CT reveals that the distal-most of the three plaques (corresponding to below * in D) has a strong FDG uptake (E). White arrowheads and yellow arrows (B-E) point, respectively, to the same proximal and distal locations in the left ICA. DUS: duplex ultrasonography, ICA: internal carotid artery.

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