RT Journal Article SR Electronic T1 Comparison of graphical analysis methods for VT estimation of a novel kappa opioid receptor tracer in humans JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1184 OP 1184 VO 52 IS supplement 1 A1 Su Jin Kim A1 MingQiang Zheng A1 Giampaolo Tomasi A1 Jim Ropchan A1 Nabeel Nabulsi A1 Yiyun Huang A1 Richard Carson A1 Nancy Goebl A1 Johannes Tauscher A1 Evan Morris YR 2011 UL http://jnm.snmjournals.org/content/52/supplement_1/1184.abstract AB 1184 Objectives To assess the utility of the relative equilibrium-based (RE) graphical analysis method [1] and RE plot with the Gjedde-Patlak correction (RE-GP) for estimation of total distribution volume (VT) for the novel kappa-opioid receptor antagonist tracer, [11C]LY2795050[3] because RE [1] developed VT image with high signal-to-noise. Methods Dynamic [11C]LY2795050 PET scans on the HRRT were acquired for 90 min in 4 healthy human subjects. Arterial blood samples were obtained and plasma input functions were constructed based on HPLC-determined parent fraction. Brain regional time-activity curves were fitted using the two-tissue compartment model (2TCM). Pixel-by-pixel and ROI based graphical methods were used for calculation of VT according to Zhou et al [1, 2]. Results RE plot results were highly dependent on the choice of relative equilibrium time (t*). Regional VT estimates from the RE plot increased with t*. Throughout the scan duration, the ratio of tissue to plasma concentration continuously increased in high binding regions (amygdala and anterior cingulate). In addition, the apparent t* varied by region and subject. By comparison, the RE-GP plot showed consistent and reliable VT estimates if time points with very low plasma activity concentration (Cp) were avoided. The correlation with 2TCM was high (y=0.979x+0.047, r2=0.98). VT images by the modified RE-GP method had high signal-to-noise. Conclusions The RE plot does not appear to be an appropriate method for calculating VT estimates of the new kappa-opioid antagonist ligand, [11C]LY2795050. This is probably due to the inability of the tracer to reach transient equilibrium within 90 min in all regions. The RE-GP plot appears to be valid for [11C]LY2795050 because the VT(RE-GP) method is robust to the choise of t* and because the VT(RE-GP) values are highly correlated with VT(2TCM)