title: Simulation of Tracer Dose Reduction in18F-FDG PET/MRI: Effects on Oncologic Reading, Image Quality, and Artifacts.
abstract: The aim of our study was to evaluate the effect of stepwise-reduced doses on objective and subjective image parameters and on oncologic readings in whole-body18F-FDG PET/MRI.Methods:We retrospectively simulated the stepwise reduction of18F-FDG doses of 19 patients (mean age ± SD, 50.9 ± 11.7 y; mean body mass index ± SD, 22.8 ± 3.2 kg/m2) who received a whole-body PET/MRI examination from 3 to 0.5 MBq/kg of body weight (kgBW) in intervals of 0.25. Objective imaging parameters were assessed by measuring the SUV and coefficient of variation in different regions (aorta, liver, spleen, kidney, small bowel, lumbar vertebra, psoas muscle, urinary bladder) as well as the noise-equivalent counting rates in each bed position. Subjective image quality was evaluated with a masked reading of each simulated PET compared with the dose of 2 MBq/kgBW. Oncologic reading was performed first according to PERCIST in each dose and second by defining malignant lesions in doses of 2 MBq/kgBW and the maximum dose image (gold standard). The diagnostic confidence of each lesion was measured using a Likert scale.Results:With decreasing doses, regions in the mid abdomen showed a stronger decrease of SUVmeanand noise-equivalent counting rates than regions in the upper abdomen (SUVmean, -45% and -15% on average in the small bowel and the liver, respectively). The coefficient of variation showed a nonlinear increase, pronounced below 1.5 MBq/kgBW. Subjective image quality was stable over a range between 1.25 and 2.75 MBq/kgBW compared with 2 MBq/kgBW. However, large photopenic areas in the mid abdomen were observed in 2 patients. In the PERCIST reading, target lesions were above the liver threshold with a stable SUVpeakin all cases down to 2 MBq/kgBW. Eighty-six of 90 lesions were identified correctly with a dose of 2 MBq/kgBW; Likert scores did not differ significantly.Conclusion:A reduction of doses in18F-FDG PET/MRI might be possible down to 2 MBq/kgBW in oncologic whole-body examinations. The image quality in the mid abdomen seems to be more affected by lower doses than in the upper abdomen, and in single cases large photopenic areas can occur. Therefore, we do not recommend reducing doses below 3 MBq/kgBW in adults at this time.
authors.affiliation: Diagnostic and Interventional Radiology, Department of Radiology, Eberhard Karls University, Tuebingen, Germany.
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Seith
authors.affiliation: Diagnostic and Interventional Radiology, Department of Radiology, Eberhard Karls University, Tuebingen, Germany holger.schmidt@uni-tuebingen.de.
authors.forename: Holger
authors.initials: H
authors.lastname: Schmidt
authors.affiliation: Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, Eberhard Karls University, Tuebingen, Germany; and.
authors.forename: Julia
authors.initials: J
authors.lastname: Kunz
authors.affiliation: Diagnostic and Interventional Radiology, Department of Radiology, Eberhard Karls University, Tuebingen, Germany.|Institute of Signal Processing and System Theory, University of Stuttgart, Stuttgart, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Küstner
authors.affiliation: Diagnostic and Interventional Radiology, Department of Radiology, Eberhard Karls University, Tuebingen, Germany.
authors.forename: Sergios
authors.initials: S
authors.lastname: Gatidis
authors.affiliation: Diagnostic and Interventional Radiology, Department of Radiology, Eberhard Karls University, Tuebingen, Germany.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Nikolaou
authors.affiliation: Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, Eberhard Karls University, Tuebingen, Germany; and.
authors.forename: Christian
authors.initials: C
authors.lastname: la Fougère
authors.affiliation: Diagnostic and Interventional Radiology, Department of Radiology, Eberhard Karls University, Tuebingen, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Schwenzer
mesh_terms: D016477:Artifacts; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D009369:Neoplasms / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography / Q000379:methods*; D011829:Radiation Dosage; D011849:Radioactive Tracers; D012189:Retrospective Studies
chemical_list: D011849:Radioactive Tracers; D019788:Fluorodeoxyglucose F18
keywords: PET; PET/MRI; dose reduction; oncology