Purpose To describe the pharmacokinetic properties of the [ 18F]fuoro-polyethylene glycol(PEG)-folate radiotracer in PET/ CT imaging of patients with advanced stage epithelial ovarian cancer (EOC).... Show morePurpose To describe the pharmacokinetic properties of the [ 18F]fuoro-polyethylene glycol(PEG)-folate radiotracer in PET/ CT imaging of patients with advanced stage epithelial ovarian cancer (EOC). Procedures In fve patients with advanced EOC (FIGO stage IIIB/IIIC, Fédération Internationale de Gynécologie et d’Obstétrique), a 90-min dynamic PET acquisition of the pelvis was performed directly after i.v. administration of 185 MBq [ 18F]fuoro-PEG6-folate. Arterial blood samples collected at nineteen timepoints were used to determine the plasma input function. A static volume of interest (VOI) for included tumor lesions was drawn manually on the PET images. Modelling was performed using PMOD software. Three diferent models (a 1-tissue compartment model (1T2k) and two 2-tissue compartment models, irreversible (2T3k) and reversible (2T4k)) were compared in goodness of ft with the time activity curves by means of the Akaike information criterion. Results The pharmacokinetic analysis in the pelvic area has proven to be much more challenging than expected. Only four out of 22 tumor lesions in fve patients were considered suitable to perform modelling on. The remaining tumor lesions were inapt due to either low tracer uptake, small size, proximity to other [ 18F]fuoro-PEG6-folate -avid structures and/or displacement by abdominal organ motion in the dynamic scan. Data from the four analyzed tumor lesions suggest that the irreversible 2T3k may best describe the pharmacokinetics. All 22 lesions were immunohistochemically stained positive for the folate receptor alpha (FRα) after resection. Conclusion Performing pharmacokinetic analysis in the abdominal pelvic region is very challenging. This brief article describes the challenges and pitfalls in pharmacokinetic analysis of a tracer with high physiological accumulation in the intestines, in case of lesions of limited size in the abdominal pelvic area. Show less
Keene, K.R.; Vught, L. van; Velde, N.M. van de; Ciggaar, I.A.; Notting, I.C.; Genders, S.W.; ... ; Beenakker, J.W.M. 2020
Although quantitative MRI can be instrumental in the diagnosis and assessment of disease progression in orbital diseases involving the extra-ocular muscles (EOM), acquisition can be challenging as... Show moreAlthough quantitative MRI can be instrumental in the diagnosis and assessment of disease progression in orbital diseases involving the extra-ocular muscles (EOM), acquisition can be challenging as EOM are small and prone to eye-motion artefacts. We explored the feasibility of assessing fat fractions (FF), muscle volumes and water T2 (T2(water)) of EOM in healthy controls (HC), myasthenia gravis (MG) and Graves' orbitopathy (GO) patients. FF, EOM volumes and T2(water)values were determined in 12 HC (aged 22-65 years), 11 MG (aged 28-71 years) and six GO (aged 28-64 years) patients at 7 T using Dixon and multi-echo spin-echo sequences. The EOM were semi-automatically 3D-segmented by two independent observers. MANOVA and t-tests were used to assess differences in FF, T2(water)and volume of EOM between groups (P< .05). Bland-Altman limits of agreement (LoA) were used to assess the reproducibility of segmentations and Dixon scans. The scans were well tolerated by all subjects. The bias in FF between the repeated Dixon scans was -0.7% (LoA: +/- 2.1%) for the different observers; the bias in FF was -0.3% (LoA: +/- 2.8%) and 0.03 cm(3)(LoA: +/- 0.36 cm(3)) for volume. Mean FF of EOM in MG (14.1% +/- 1.6%) was higher than in HC (10.4% +/- 2.5%). Mean muscle volume was higher in both GO (1.2 +/- 0.4 cm(3)) and MG (0.8 +/- 0.2 cm(3)) compared with HC (0.6 +/- 0.2 cm(3)). The average T2(water)for all EOM was 24.6 +/- 4.0 ms for HC, 24.0 +/- 4.7 ms for MG patients and 27.4 +/- 4.2 ms for the GO patient. Quantitative MRI at 7 T is feasible for measuring FF and muscle volumes of EOM in HC, MG and GO patients. The measured T2(water)was on average comparable with skeletal muscle, although with higher variation between subjects. The increased FF in the EOM in MG patients suggests that EOM involvement in MG is accompanied by fat replacement. The unexpected EOM volume increase in MG may provide novel insights into underlying pathophysiological processes. Show less
