Feasibility of carotid artery PET/MRI in psoriasis patients

Abstract

We report our initial experience of performing integrated PET/MR imaging of the carotid arteries in psoriatic patients. Eleven patients with psoriasis and ten controls underwent carotid PET/MRI. Following injection of the FDG tracer, 3d T1w gradient echo sequence (atMR) was obtained for attenuation correction of PET data. High resolution images of carotid artery were then obtained, including pre-and post-contrast T1-w, T2-w and proton-density images as well as TOF images followed by PET imaging of the torso. From the fused axial PET/MRI, the arterial wall SUVmax and TBRmax was quantified in each slice. MRI images were also evaluated for vessel wall volume, plaque and internal composition. SUVmax and TBRmax were respectively, 1.72 ± 0.38 & 1.17 ± 0.27 in L- CCA, 1.75 ± 0.39 & 1.24 ± 0.19 in R-CCA, 1.59 ± 0.24 & 1.08 ± 0.14 in L-ICA and 1.62 ± 0.27 & 1.15 ± 0.17 in R-ICA in psoriatic patients and 1.74 ± 0.22 & 1.28 ± 0.44 in L- CCA, 1.74 ± 0.33 & 1.07 ± 0.28 in R-CCA, 1.78 ± 0.32 & 1.29 ± 0.39 in L-ICA and 1.60 ± 0.29 & 0.98 ± 0.25 in R-ICA in the controls. No discrete plaques were identified in any of the vessel segments in MRI. PET/MRI is feasible in evaluation of carotid arteries in psoriatic patients.

Keywords: MRI; PET; Psoriasis; atherosclerosis; carotid; inflammation.

Figure 1

Workflow of carotid artery PET/MRI in psoriasis patients. After injection of FDG, 3d T1 weighted attenuation corrected MRI images are obtained. This was followed by dedicated MRI sequences, which consisted of 3d-Time of flight, T1-w, T2-w, PD-weighed black blood images before contrast. After contrast administration, dynamic enhanced images and T1-weighed axial images were obtained. Following this, FDG PET torso acquisition was performed.

Figure 2

Transverse T1 weighted MRI image (A), PET image (B) and fused FDG-PET/MR (C) at the level of the right and left common carotid artery (blue arrows). Arterial-wall FDG uptake was quantified by drawing two region of interests (ROI) around the lumen and outer wall of each CCA (right and left) on fused FDG-PET/MR images (B) to define the wall area. Maximum standard uptake value of the carotid wall was then calculated using MIM software, which was corrected for blood pool activity (jugular vein) to obtain TBR.

Figure 3

Example of carotid PET/MRI from another patient. A. Axial T1-w MRI image at the level of common carotid artery. B. MRAC PET non-fused image of the neck. C. PET/MRI images with fused MRAC PET and T1 w black blood images demonstrate FDG activity.

Figure 4

A. Axial T1-weighted turbo spin echo (black blood) image shows high signal in the right common carotid artery (Blue arrow). B. Fused PET/MRI image in the same patient at the same level showed mild increased SUVmax at this level.

Figure 5

Box plots of absolute SUVMAX and TBRMAX values for left sided vessels comparing psoriasis patients with control group for ICA SUVMAX (A), ICA TBRMAX (B), CCA SUVMAX (C), and CCA TBRMAX (D). Box-plot edges indicate the 25th and 75th percentiles, central bars indicate medians and whiskers indicate extremes.

Figure 6

Box plots of absolute SUVMAX and TBRMAX values for right sided vessels comparing psoriasis patients with control group for ICA SUVMAX (A), ICA TBRMAX (B), CCA SUVMAX (C), and CCA TBRMAX (D). Box-plot edges indicate the 25th and 75th percentiles, central bars indicate medians and whiskers indicate extremes.

Figure 7

Correlation of SUVMAX and TBRMAX values between CCA and ICA vessels on the same side. A. Left CCA vs Left ICA SUVMAX; B. Left CCA vs Left ICA TBRMAX; C. Right CCA vs Right ICA SUVMAX; and D. Right CCA vs Right ICA TBRMAX. Significant positive correlations were demonstrated in all four segments (Spearman rank correlation test).