Journal
JOURNAL OF NUCLEAR MEDICINE
Volume 59, Issue 4, Pages 636-638Publisher
SOC NUCLEAR MEDICINE INC
DOI: 10.2967/jnumed.117.202861
Keywords
PET; standardization; Ga-68; calibration; trial
Funding
- Movember Foundation through the Prostate Cancer Foundation of Australia's Research Program
- Clinical Fellowship Award from the Peter MacCallum Foundation
- NHMRC Senior Practitioner Fellowship
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We report the discovery of a systematic miscalibration during the work-up process for site validation of a multicenter clinical PET imaging trial using Ga-68, which manifested as a consistent and reproducible underestimation in the quantitative accuracy (assessed by SUV) of a range of PET systems from different manufacturers at several different facilities around Australia. Methods: Sites were asked to follow a strict preparation protocol to create a radioactive phantom with Ga-68 to be imaged using a standard clinical protocol before commencing imaging in the trial. All sites had routinely used Ga-68 for clinical PET imaging for many years. The reconstructed image data were transferred to an imaging core laboratory for analysis, along with information about ancillary equipment such as the radionuclide dose calibrator. Fourteen PET systems were assessed from 10 nuclear medicine facilities in Australia, with the aim for each PET system being to produce images within 5% of the true SUV. Results: At initial testing, 10 of the 14 PET systems underestimated the SUV by 15% on average (range, 13%-23%). Multiple PET systems at one site, from two different manufacturers, were all similarly affected, suggesting a common cause. We eventually identified an incorrect factory-shipped dose calibrator setting from a single manufacturer as being the cause. The calibrator setting for Ga-68 was subsequently adjusted by the users so that the reconstructed images produced accurate values. Conclusion: PET imaging involves a chain of measurements and calibrations to produce accurate quantitative performance. Testing of the entire chain is simple, however, and should form part of any quality assurance program or prequalifying site assessment before commencing a quantitative imaging trial or clinical imaging.
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