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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

The NEMA phantom curve of the TOF-PET/CT (continuous) and TOF-PET/MR (dashed), provided by its manufacturer.See enlarged image of the clinically relevant area (black box) in Fig 4.
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pone.0128842.g003: The NEMA phantom curve of the TOF-PET/CT (continuous) and TOF-PET/MR (dashed), provided by its manufacturer.See enlarged image of the clinically relevant area (black box) in Fig 4.

Mentions: The NECRP was then cross-referenced in the graphic NECRP x Activity concentration (Fig 2) in order to get the corresponding optimal activity concentration at the acquisition time ([A]0). By obtaining this value, it is now possible to establish the relation between patient-based and phantom-based count-rate measurements. Applying the calculated [A]0 value on the NEMA phantom curve of the GE Discovery D690 (Fig 3) that was used in these acquisitions, the target NECR (NECRT) was obtained. Notice that this image quality target value is independent of the PET system used.


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)

The NEMA phantom curve of the TOF-PET/CT (continuous) and TOF-PET/MR (dashed), provided by its manufacturer.See enlarged image of the clinically relevant area (black box) in Fig 4.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0128842.g003: The NEMA phantom curve of the TOF-PET/CT (continuous) and TOF-PET/MR (dashed), provided by its manufacturer.See enlarged image of the clinically relevant area (black box) in Fig 4.
Mentions: The NECRP was then cross-referenced in the graphic NECRP x Activity concentration (Fig 2) in order to get the corresponding optimal activity concentration at the acquisition time ([A]0). By obtaining this value, it is now possible to establish the relation between patient-based and phantom-based count-rate measurements. Applying the calculated [A]0 value on the NEMA phantom curve of the GE Discovery D690 (Fig 3) that was used in these acquisitions, the target NECR (NECRT) was obtained. Notice that this image quality target value is independent of the PET system used.

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