Mark Allan Ahlman MD, Presenter: Nothing to Disclose

Roberto Maass-Moreno PhD, Abstract Co-Author: Nothing to Disclose

Davis M. Vigneault BS, Abstract Co-Author: Nothing to Disclose

Veit Sandfort MD, Abstract Co-Author: Nothing to Disclose

Nehal Mehta, Abstract Co-Author: Nothing to Disclose

David A. Bluemke MD, PhD, Abstract Co-Author: Research support, Siemens AG

Vascular target to background ratios (TBR) are calculated based on standardized uptake value (SUV) and blood pool activity (BP), which in turn are related to body weight (BW) and glomerular filtration of FDG. The purpose of this study was to determine methods to quantify FDG PET vascular activity to avoid confounders that may obscure underlying measures of vascular uptake.

25 normal adult subjects were prospectively enrolled for PET-CT at 2 hrs uptake time using lean body mass (LBM)-based FDG dosing (0.14 mCi/kg). Per subject, 200-300 descending aorta max SUV measurements and adjacent mean reference venous SUV were used to form TBR-Blood. Target SUV was measured using BW (SUV-BW) and LBM (SUV-LBM) as well as reference venous activity (BP-BW, BP-LBM). Mean liver activity was used as a reference for TBR-Liver. Spearman’s correlation of measurements with weight and BP activity were calculated. Significant changes in rho (reported where p value significance <0.05) were used to indicate if alternate quantification methods allowed for the removal of weight, BP-BW, or BP-LBM as confounding internal correlates. Coefficient of variation (COV) was reported for values of interest.

Weight correlated with BP-BW (0.60, p=0.002) and SUV-BW (0.53, p=0.007), but did not correlate with BP-LBM or SUV-LBM. BP-BW correlated with SUV-BW (0.83, p<0.0001), SUV-LBM (0.43, p=0.034), and TBR-Blood (-0.52, p=0.008). BP-LBM correlated with SUV-BW (0.61, p<0.001), SUV-LBM (0.73, p<0.0001), but not TBR-Blood. Neither BP-BW nor BP-LBM showed correlation with TBR-Liver. The COV for SUV-LBM, TBR-Blood, and TBR-Liver was 15.5%, 10.7%, and 10.1%, respectively.

Weight correlates highly with arterial SUV, likely influenced by the mathematical calculation of SUV. Likewise, BP activity is highly correlated with target arterial wall activity, likely due to volume averaging of blood in the artery lumen with adjacent wall. For our sample, the use of LBM for SUV calculation minimizes potential type I errors that may arise when correlating SUV with clinical endpoints. TBR-Blood is influenced by variability in BP activity; whereas, TBR-Liver mitigates the confounding effect of BP, has the lowest COV, and obviates LBM calculation.

This work details strategies for FDG quantification of vascular activity that minimize confounding effects and improves measurement reliability.   

Ahlman, M, Maass-Moreno, R, Vigneault, D, Sandfort, V, Mehta, N, Bluemke, D, The Confounding Effects of Weight and Blood Pool Activity in PET Vascular Imaging with ¹⁸FDG.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14045438.html