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Modeling of Tracer Transport Delays for Improved Quantification of Regional Pulmonary F-FDG Kinetics, Vascular Transit Times, and Perfusion
Journal article   Peer reviewed

Modeling of Tracer Transport Delays for Improved Quantification of Regional Pulmonary F-FDG Kinetics, Vascular Transit Times, and Perfusion

Tyler J. Wellman, Tilo Winkler and Marcos F. Vidal Melo
Annals of biomedical engineering, Vol.43(11), pp.2722-2734
11/01/2015
DOI: 10.1007/s10439-015-1327-2
PMCID: PMC4618094
PMID: 25940652

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Abstract

18F-FDG-PET is increasingly used to assess pulmonary inflammatory cell activity. However, current models of pulmonary 18F-FDG kinetics do not account for delays in 18F-FDG transport between the plasma sampling site and the lungs. We developed a three-compartment model of 18F-FDG kinetics that includes a delay between the right heart and the local capillary blood pool, and used this model to estimate regional pulmonary perfusion. We acquired dynamic 18F-FDG scans in 12 mechanically ventilated sheep divided into control and lung injury groups (n = 6 each). The model was fit to tracer kinetics in three isogravitational regions-of-interest to estimate regional lung transport delays and regional perfusion. 13NN bolus infusion scans were acquired during a period of apnea to measure regional perfusion using an established reference method. The delayed input function model improved description of 18F-FDG kinetics (lower Akaike Information Criterion) in 98% of studied regions. Local transport delays ranged from 2.0 to 13.6 s, averaging 6.4 ± 2.9 s, and were highest in non-dependent regions. Estimates of regional perfusion derived from model parameters were highly correlated with perfusion measurements based on 13NN-PET (R 2 = 0.92, p < 0.001). By incorporating local vascular transports delays, this model of pulmonary 18F-FDG kinetics allows for simultaneous assessment of regional lung perfusion, transit times, and inflammation.
Capillary transit times Plasma input function Positron emission tomography Tracer kinetics

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