Session Information
Date: Tuesday, October 23, 2018
Session Title: Imaging of Rheumatic Diseases Poster III: Other Modalities
Session Type: ACR Poster Session C
Session Time: 9:00AM-11:00AM
Background/Purpose: 18F-fluorodeoxyglucose (FDG) PET may be used to quantify vascular inflammation in large-vessel vasculitis (LVV). Quantitative analysis of arterial FDG uptake has not been standardized. Delayed acquisition time may be advantageous for vascular PET imaging but has not been studied in LVV. Arterial FDG uptake is often normalized to uptake in background tissue; however, the factors that influence tissue-specific distribution of FDG in inflammatory diseases are unknown. The study objective was to identify factors associated with FDG uptake in 1) the large arteries and 2) background tissues (liver, blood pool, spleen) at 1 and 2 hour image acquisition times in a cohort of patients with LVV and comparators.
Methods: Patients with LVV and comparators (systemic inflammatory diseases, healthy controls), were recruited into a prospective observational cohort. Participants underwent either whole body PET-MR at 1 hour acquisition time, PET-CT at 2 hour acquisition time, or both. Arterial uptake was quantified as the sum of mean standardized uptake values (SUV)max for 5 segments of the aorta, carotid, and subclavian arteries. SUVmean values were calculated for each background tissue. Multivariate linear regression models were used to identify associations between tissue-specific FDG uptake and atherosclerosis, vasculitis, and FDG clearance- related factors (see Table). The same predictor variables were included in each regression model to facilitate comparisons across different tissues. A p value < 0.05 was considered significant.
Results: PET scans were performed at 1 hour (n = 175) and 2 hours (n = 194), with most studies performed sequentially at both time points (n = 145). Age, BMI, and CRP were significantly associated with arterial-FDG uptake at both the 1 and 2 hour time points, with increased effect estimates at 2 hours. Additional vasculitis-related factors (diagnosis, treatment) were also significantly associated with arterial uptake at the 2 hour time point. Factors related to FDG clearance (uptake time, glomerular filtration rate) were significantly associated with FDG uptake in liver and blood pool at 1 hour but were weakly or not associated with FDG uptake at 2 hours. Additional factors were associated with liver and blood pool at 2 hours, but with small effects estimate sizes. Vasculitis-related factors were associated with splenic uptake at 1 and 2 hours.
Conclusion: Tissue-specific factors are associated with FDG distribution in a time-dependent manner. Delayed image acquisition demonstrates stronger associations between arterial FDG uptake and atherosclerosis/vasculitis related factors. The impact of factors related to FDG clearance in background tissues is reduced with delayed imaging. Delayed image acquisition and normalization of arterial FDG uptake to liver or vein is preferable in LVV.
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Table: Factors significantly associated with tissue distribution of 18f-fluorodeoxyglucose on positron emission tomography in large-vessel vasculitis at 1 and 2 hour imaging acquisition times
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1-hour Positron Emission Tomography
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2-hour Positron Emission Tomography
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Target Tissue
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Artery
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Age (ß =0.09, p<0.01) BMI (ß=0.28, p<0.01) CRP (ß=0.05, p<0.01) |
Age (ß=0.20, p<0.01) BMI (ß=0.41, p<0.01) CRP (ß=0.12, p=0.01) Diagnosis (ß=2.06, p=0.04) Immune Meds (ß=1.65, p=0.01) |
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Background Tissue
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Liver
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BMI (ß=0.02, p<0.01) GFR (ß=-0.002, p=0.03) Uptake time (ß=-0.003, p=0.01) |
BMI (ß=0.03, p<0.01) Age (ß=0.004, p=0.02) Female (ß=0.08, p<0.01) |
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Blood Pool
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BMI (ß=0.01, p<0.01) Uptake time (ß=-0.005, p<0.01) GFR (ß=-0.003, p<0.01) |
BMI (ß=0.02, p<0.01) Uptake time (ß=-0.003, p<0.01) Age (ß=0.004, p<0.01) Fasting Glucose (ß=0.003, p<0.01) Immune Meds (ß=-0.003, p<0.01) |
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Spleen
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BMI (ß=0.02, p<0.01) Diagnosis (ß=-0.08, p=0.03) PGA (ß=-0.03, p=0.04) WBC (ß=0.02, p<0.01) |
BMI (ß=0.03, p<0.01) Immune Meds (ß=-0.09, p=0.01) |
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*All of the following variables were included in each regression model: Atherosclerosis-related factors: Gender (male vs female), Body mass index (BMI), Age in years, Fasting glucose (mg/dL) Vasculitis-related factors: C-reactive protein (CRP, mg/L), Total white blood cell count (WBC, K/uL), Treatment with immunosuppressants (Immune Meds, Yes vs No), Daily prednisone dose (mg), Physician global assessment (PGA, 0-10 scale), Diagnosis (large-vessel vasculitis vs comparator), Hematocrit (%) FDG clearance factors: Uptake time (minutes from injection of FDG), Glomerular filtration rate (GFR, ml/minute)
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To cite this abstract in AMA style:
Rosenblum JS, Quinn K, Ahlman MA, Grayson PC. Kinetics of Tissue-Specific Distribution of 18f-Fluorodeoxyglucose in Positron Emission Tomography in Large Vessel Vasculitis [abstract]. Arthritis Rheumatol. 2018; 70 (suppl 10). https://acrabstracts.org/abstract/kinetics-of-tissue-specific-distribution-of-18f-fluorodeoxyglucose-in-positron-emission-tomography-in-large-vessel-vasculitis/. Accessed May 27, 2019.« Back to 2018 ACR/ARHP Annual Meeting
ACR Meeting Abstracts - https://acrabstracts.org/abstract/kinetics-of-tissue-specific-distribution-of-18f-fluorodeoxyglucose-in-positron-emission-tomography-in-large-vessel-vasculitis/