Defining optimal tracer activities in pediatric oncologic whole-body 18F-FDG-PET/MRI

Sergios Gatidis; Holger Schmidt; Christian la Fougère; Konstantin Nikolaou; Nina F Schwenzer; Jürgen F Schäfer

doi:10.1007/s00259-016-3503-5

Defining optimal tracer activities in pediatric oncologic whole-body ¹⁸F-FDG-PET/MRI

Eur J Nucl Med Mol Imaging. 2016 Dec;43(13):2283-2289. doi: 10.1007/s00259-016-3503-5. Epub 2016 Aug 26.

Authors

Sergios Gatidis^{1

2}, Holger Schmidt³, Christian la Fougère⁴, Konstantin Nikolaou³, Nina F Schwenzer³, Jürgen F Schäfer³

Affiliations

¹ Department of Radiology, Diagnostic and Interventional Radiology, University of Tübingen, Tübingen, Germany. sergios.gatidis@med.uni-tuebingen.de.
² , Hoppe-Seyler-Str. 3, 72076, Tübingen, Germany. sergios.gatidis@med.uni-tuebingen.de.
³ Department of Radiology, Diagnostic and Interventional Radiology, University of Tübingen, Tübingen, Germany.
⁴ Department of Radiology, Nuclear Medicine, University of Tübingen, Tübingen, Germany.

PMID: 27565153
DOI: 10.1007/s00259-016-3503-5

Abstract

Purpose: To explore the feasibility of reducing administered tracer activities and to assess optimal activities for combined ¹⁸F-FDG-PET/MRI in pediatric oncology.

Methods: 30 ¹⁸F-FDG-PET/MRI examinations were performed on 24 patients with known or suspected solid tumors (10 girls, 14 boys, age 12 ± 5.6 [1-18] years; PET scan duration: 4 min per bed position). Low-activity PET images were retrospectively simulated from the originally acquired data sets using randomized undersampling of list mode data. PET data of different simulated administered activities (0.25-2.5 MBq/kg body weight) were reconstructed with or without point spread function (PSF) modeling. Mean and maximum standardized uptake values (SUV_mean and SUV_max) as well as SUV variation (SUV_var) were measured in physiologic organs and focal FDG-avid lesions. Detectability of organ structures and of focal ¹⁸F-FDG-avid lesions as well as the occurrence of false-positive PET lesions were assessed at different simulated tracer activities.

Results: Subjective image quality steadily declined with decreasing tracer activities. Compared to the originally acquired data sets, mean relative deviations of SUV_mean and SUV_max were below 5 % at ¹⁸F-FDG activities of 1.5 MBq/kg or higher. Over 95 % of anatomic structures and all pathologic focal lesions were detectable at 1.5 MBq/kg ¹⁸F-FDG. Detectability of anatomic structures and focal lesions was significantly improved using PSF. No false-positive focal lesions were observed at tracer activities of 1 MBq/kg ¹⁸F-FDG or higher. Administration of ¹⁸F-FDG activities of 1.5 MBq/kg is, thus, feasible without obvious diagnostic shortcomings, which is equivalent to a dose reduction of more than 50 % compared to current recommendations.

Conclusion: Significant reduction in administered ¹⁸F-FDG tracer activities is feasible in pediatric oncologic PET/MRI. Appropriate activities of ¹⁸F-FDG or other tracers for specific clinical questions have to be further established in selected patient populations.

Keywords: Children; FDG; PET/MRI; Radiation dose; Tracer dose.

MeSH terms

Adolescent
Child
Child, Preschool
Dose-Response Relationship, Drug
Feasibility Studies
Female
Fluorodeoxyglucose F18 / administration & dosage*
Humans
Infant
Magnetic Resonance Imaging / methods*
Male
Multimodal Imaging / methods
Neoplasms / diagnostic imaging*
Positron-Emission Tomography / methods*
Radiation Dosage
Radiation Exposure / analysis
Radiation Exposure / prevention & control*
Radiation Protection / methods*
Radiopharmaceuticals / administration & dosage
Reproducibility of Results
Sensitivity and Specificity
Whole Body Imaging / methods
Whole-Body Counting / methods

Substances

Radiopharmaceuticals
Fluorodeoxyglucose F18