Page 134 - Assessing right ventricular function and the pulmonary circulation in pulmonary hypertension Onno Anthonius Spruijt
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Summarized, short‐axis images of the right and left ventricle were analyzed using MASS software (MEDIS Medical Imaging Systems, Leiden, The Netherlands). Endocardial borders of the right ventricle were manually traced on end‐diastolic images and on end‐systolic images. Right and left ventricular end‐diastolic and end‐systolic volumes were assessed using the Simpson rule.
IPAH Patients 18FLT PET
18FLT was synthesized as described previously [26]. Minimum 4 hours fasting was instructed prior to the PET scan, IPAH patients were scanned on a Philips Ingenuity PET/CT (Philips Healthcare, Best, The Netherlands), whilst control data sets were from a Philips Gemini TF‐64 PET/CT (Philips Healthcare, Best, The Netherlands) using an identical scanning protocol. First, following a scout‐CT scan, IPAH patients were positioned with lungs centered in the field of view of the PET scanner. Then, a dynamic 60‐min emission scan was started simultaneously with automated bolus intravenous injection of 370 MBq of 18FLT (0.8 mL/s). After completion of the emission scan, a low‐ dose CT scan was performed to correct for photon‐attenuation and scatter. Finally, emission data were reconstructed in a 36 frame (1x10, 8x5, 4x10, 3x20, 5x30, 5x60, 4x150, 4x300 and 2x600 s) using the 3‐Dimensional Row‐Action Maximum Likelihood Algorithm (3D‐RAMLA), applying all appropriate corrections for dead time, decay, scatter, attenuation and normalization. During the scan, venous blood samples were withdrawn at 5, 10, 20, 30, 40 and 60 minutes post injection and measured for the presence of radiolabeled metabolites (18F‐glucuronide) and the ratio of plasma and whole‐blood activity concentrations as described by Hoekstra et al. [27].
Kinetic Model for Data Analysis
18FLT PET data were analyzed using the plasma kinetic model as described previously [26]. The model consists of three or four rate constants, of which k3 represents phosphorylation of 18FLT by thymidine kinase and this rate constant was assumed to most closely represent proliferation rate, thus used to represent the lung 18FLT uptake. The model can be described using: CPET (t)  CT (t) VA CA (t) VV CA (t) (1), in which CPET(t) represents the measured pulmonary
activity concentrations, CT(t) the activity according to the plasma kinetic model, CA(t) and CV(t) are arterial and venous blood concentrations, respectively. To correct for contamination of the signal by blood‐pool activity, VA (arterial blood volume fraction) and VV (venous blood volume fraction) were added to the model. For CT(t), both an irreversible 2‐compartment 3k model (2T3k) and a reversible 2‐compartment 4k model (2T4k) were tested and the best fit was obtained. The use of an




























































































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