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Dose Optimization in TOF-PET/MR Compared to TOF-PET/CT.

Queiroz MA, Delso G, Wollenweber S, Deller T, Zeimpekis K, Huellner M, de Galiza Barbosa F, von Schulthess G, Veit-Haibach P - PLoS ONE (2015)

Bottom Line: 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 MR-sequences 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Imaging, Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.

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 TOF-PET/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 MR-sequences 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.

No MeSH data available.


Related in: MedlinePlus

Evaluation and transfer steps from activities in PET/CT (1) to theoretically (2,3) achievable reduction in injected activity in TOF-PET/MR (4) and clinically realistically activities in TOF-PET/MR (5—blue arrow).
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pone.0128842.g004: Evaluation and transfer steps from activities in PET/CT (1) to theoretically (2,3) achievable reduction in injected activity in TOF-PET/MR (4) and clinically realistically activities in TOF-PET/MR (5—blue arrow).

Mentions: See enlarged image of the clinically relevant area (black box) in Fig 4.


Dose Optimization in TOF-PET/MR Compared to TOF-PET/CT.

Queiroz MA, Delso G, Wollenweber S, Deller T, Zeimpekis K, Huellner M, de Galiza Barbosa F, von Schulthess G, Veit-Haibach P - PLoS ONE (2015)

Evaluation and transfer steps from activities in PET/CT (1) to theoretically (2,3) achievable reduction in injected activity in TOF-PET/MR (4) and clinically realistically activities in TOF-PET/MR (5—blue arrow).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493146&req=5

pone.0128842.g004: Evaluation and transfer steps from activities in PET/CT (1) to theoretically (2,3) achievable reduction in injected activity in TOF-PET/MR (4) and clinically realistically activities in TOF-PET/MR (5—blue arrow).
Mentions: See enlarged image of the clinically relevant area (black box) in Fig 4.

Bottom Line: 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 MR-sequences 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Imaging, Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.

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 TOF-PET/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 MR-sequences 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.

No MeSH data available.


Related in: MedlinePlus