A method of adjusting SUV for injection-acquisition time differences in 18F-FDG PET Imaging

A time normalisation method of tumour SUVs in 18F-FDG PET imaging is proposed that has been verified in lung cancer patients. A two-compartment model analysis showed that, when SUV is not corrected for 18F physical decay (SUVuncorr), its value is within 5% of its peak value (t = 79 min) between 55 and 110 min after injection, in each individual patient. In 10 patients, each with 1 or more malignant lesions (n = 15), two PET acquisitions were performed within this time delay, and the maximal SUV of each lesion, both corrected and uncorrected, was assessed. No significant difference was found between the two uncorrected SUVs, whereas there was a significant difference between the two corrected ones: mean differences were 0.04 ± 0.22 and 3.24 ± 0.75 g.ml-1, respectively (95% confidence intervals). Therefore, a simple normalisation of decay-corrected SUV for time differences after injection is proposed: SUVN = 1.66*SUVuncorr, where the factor 1.66 arises from decay correction at t = 79 min. When 18F-FDG PET imaging is performed within the range 55-110 min after injection, a simple SUV normalisation for time differences after injection has been verified in patients with lung cancer, with a ±2.5% relative measurement uncertainty. (orig.)