RT Journal Article
SR Electronic
T1 A new method for positron-emitting radionuclide cross-calibration of PET/CT scanners and dose calibrators from a NIST traceable Ge-68 source.
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1738
OP 1738
VO 56
IS supplement 3
A1 Levent Sensoy
A1 John Richmond
A1 John Sunderland
A1 Christine Mundt
A1 Kelli Schlarbaum
YR 2015
UL http://jnm.snmjournals.org/content/56/supplement_3/1738.abstract
AB 1738 Objectives Current NIST traceable Ge-68 dose calibrator sources are linked to dated NIST F-18 measurements, introducing ~4% bias in F-18 dose calibrator measurements. This situation results in discordant PET/CT measurements of Ga-68, F-18, and other positron-emitters. This study validates a PET/CT scanner calibration method based upon Ga-68 measurements, traceable to the NIST Ge-68 standard, rather than F-18.Methods After calibrating the dose calibrator with a NIST traceable Ge-68 syringe source, a cross-calibration of the PET scanner was performed using a phantom with known Ga-68 activity. Once the PET scanner was calibrated for Ga-68, a uniform aqueous phantom was filled with F-18 (activity measured using the standard gain recommended by the dose calibrator vendor). Upon PET imaging and reconstruction, a volume of interest from the phantom PET image was analyzed for its scanner derived mean concentration, and compared to the dose calibrator-based concentration. The resulting bias was then used to back-correct the dose calibrator gain setting for F-18, accordingly. Finally, the gain settings for other common positron-emitting radionuclides without prompt gammas, (C-11, N-13, and O-15) were adjusted relative to F-18 activities according to their positron emission branching ratios.Results The observed 4% discrepancy between the quantitative measurements of PET derived concentrations from uniform phantom images using different positron-emitting radionuclides due to inaccuracies from the conventional cross-calibration method was successfully reduced to ~1% by using the quantitative measurement capabilities of the PET scanner to generate proper radionuclide-specific gain settings for the dose calibrator.Conclusions Until new NIST traceable sources integrate the newer and more accurate F-18 measurements for dose calibrator calibration, the proposed method promises better accuracy and consistency for a range of positron-emitting radionuclides.