TY - JOUR T1 - Measurement of PET Quantitative Bias In Vivo JF - Journal of Nuclear Medicine JO - J Nucl Med DO - 10.2967/jnumed.120.251397 SP - jnumed.120.251397 AU - Martin A Lodge AU - Wojciech Lesniak AU - Michael A. Gorin AU - Kenneth J Pienta AU - Steven P. Rowe AU - Martin G. Pomper Y1 - 2020/10/01 UR - http://jnm.snmjournals.org/content/early/2020/10/09/jnumed.120.251397.abstract N2 - Quantitative imaging biomarkers are widely used in PET for both research and clinical applications, yet bias in the underlying image data has not been well-characterized. In the absence of a readily available reference standard for in vivo quantification, bias in PET images has been inferred using physical phantoms, even though arrangements of this sort provide only a poor approximation of the imaging environment in real patient examinations. In this study we used data acquired in patient volunteers to assess PET quantitative bias in vivo. Image-derived radioactivity concentrations in the descending aorta were compared with blood samples counted on a calibrated gamma counter. Methods: Ten patients with prostate cancer were studied using 18F-DCFPyL PET/CT. For each patient, 3 whole-body PET/CT image series were acquired following a single administration of the radiotracer: shortly after injection as well as approximately 1 and 4 hours later. Venous blood samples were obtained at 8 time points over an 8 hour period and whole-blood was counted on a NaI gamma counter. A 10 mm diameter, 20 mm long cylindrical volume-of-interest was positioned in the descending thoracic aorta to estimate the PET-derived radioactivity concentration in blood (CPET). A tri-exponential function was fit to the gamma counter blood data and used to estimate the radioactivity concentration (Cgamma) at the time of each PET acquisition. Results: CPET and Cgamma were linearly related with R2 = 0.985 over a range of relevant radioactivity concentrations. The mean difference between the PET and gamma counter data corresponded to 4.8 ± 8.6 % with the PET measurements tending to be greater. Conclusion: Human image data acquired on a conventional whole-body PET/CT system with a typical clinical protocol differed by an average of around 5 % compared to blood samples counted on a calibrated gamma counter. This bias may be partly attributable to residual uncorrected scatter or attenuation correction error. These data offer an opportunity for the assessment of PET bias in vivo and provide additional support for the use of quantitative imaging biomarkers. ER -