Abstract
1705
Objectives: Distribution volume (DV) values are regarded as quantitative measure for specific binding of tracer in tissue. The determination of standardised uptake values (SUV), however, is only a semi-quantitative method of reporting tumor uptake. The purpose of this study was to investigate the correlation between SUV and DV values in [18F]Galacto-RGD PET imaging. Methods: PET imaging was performed in 8 patients with primary diagnosis of breast cancer. Dynamic scans were acquired covering the breast with a total scan duration of 60 min after injection of 150–200 MBq of [18F]Galacto-RGD. The images were reconstructed using the ordered-subsets expectation maximisation algorithm. Volumes of interest (VOI) were drawn on muscle, breast and tumor tissue (n=23). An image-based input function was derived from VOI definition in the aorta. The tracer kinetic data was analysed using a 2 tissue compartmental (2T) model. If no model solution could be obtained a 1 tissue compartmental (1T) model was used. Outcome measures were DV values (2T: DV=K1/k2(1+k3/k4), 1T: DV=K1/k2). Additionally, for the last seven frames sequential SUVs were derived for the same VOI. Pearson correlation coefficients (r) between SUVs and DV values were calculated for all VOI for the last seven frames. Results: Mean DV values and SUVs (55min p.i.) were 1.21±0.53 and 2.39±1.08 respectively with a ratio of K1/k2=0.32±0.13 and of k3/k4=2.83±1.81. There was a highly significant correlation between SUVs and DV values at 55min p.i. for all VOI (muscle, breast, tumor; p<0.0001) and for tumors separately (p=0.004, n=9). r values between SUV and DV values increased continuously over time from 0.78 (12.5min p.i.) to 0.92 (55min p.i.). r values between SUV and DV values only for tumor tissue increased from 0.50 (12.5min p.i.) to 0.85 (55min p.i.). The highest correlation was found after 45 and 55min p.i. Conclusions: The high ratio of k3/k4 compared to K1/k2 suggests specific tracer binding without relevant perfusion effects. Moreover, this study shows that SUVs obtained from 40 to 60 min p.i. are highly correlated to DV values and therefore represent a suitable alternative to dynamic imaging.
- Society of Nuclear Medicine, Inc.