Dose optimization in TOF-PET/MR compared to TOF-PET/CT

Marcelo A. Queiroz, Gaspar Delso, Scott Wollenweber, Timothy Deller, Konstantinos Zeimpekis, Martin Huellner, Felipe De Galiza Barbosa, Gustav Von Schulthess, Patrick Veit-Haibach

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Abstract

Purpose To evaluate the possible activity reduction in FDG-imaging in a Time-of-Flight (TOF) PET/ MR, based on cross-evaluation of patient-based NECR (noise equivalent count rate) measurements in PET/CT, cross referencing with phantom-based NECR curves as well as initial evaluation of TOF-PET/MR with reduced activity. Materials and Methods A total of 75 consecutive patients were evaluated in this study. PET/CT imaging was performed on a PET/CT (time-of-flight (TOF) Discovery D 690 PET/CT). Initial PET/MR imaging was performed on a newly available simultaneous TOF-PET/MR (Signa PET/MR). An optimal NECR for diagnostic purposes was defined in clinical patients (NECRP) in PET/CT. Subsequent optimal activity concentration at the acquisition time ([A]0) and target NECR (NECRT) were obtained. These data were used to predict the theoretical FDG activity requirement of the new TOF-PET/MR system. Twenty-five initial patients were acquired with (retrospectively reconstructed) different imaging times equivalent for different activities on the simultaneous PET/MR for the evaluation of clinically realistic FDG-activities. Results The obtained values for NECRP, [A]0 and NECRT were 114.6 (± 14.2) kcps (Kilocounts per second), 4.0 (± 0.7) kBq/mL and 45 kcps, respectively. Evaluating the NECRT together with the phantom curve of the TOF-PET/MR device, the theoretical optimal activity concentration was found to be approximately 1.3 kBq/mL, which represents 35% of the activity concentration required by the TOF-PET/CT. Initial evaluation on patients in the simultaneous TOFPET/ MR shows clinically realistic activities of 1.8 kBq/mL, which represent 44% of the required activity. Conclusion The new TOF-PET/MR device requires significantly less activity to generate PET-images with good-to-excellent image quality, due to improvements in detector geometry and detector technologies. The theoretically achievable dose reduction accounts for up to 65% but cannot be fully translated into clinical routine based on the coils within the FOV and MRsequences applied at the same time. The clinically realistic reduction in activity is slightly more than 50%. Further studies in a larger number of patients are needed to confirm our findings.

Original languageEnglish
Article numbere0128842
JournalPLoS ONE
Volume10
Issue number7
DOIs
StatePublished - Jul 6 2015
Externally publishedYes

Funding

This research project was supported by an institutional research grant from GE Healthcare. Co-authors Gaspar Delso, Scott D. Wollenweber and Timothy Deller are employed by GE Healthcare. PVH received IIS Grants from Bayer Healthcare, Siemens Medical Solutions, Roche Pharma and GE Healthcare and speaker fees from GE Healthcare. GvS is a grant recipient from GE Healthcare and received speaker fees from GE Healthcare. There are no patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials.

FundersFunder number
GE Healthcare

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