Effect of MR contrast agent on quantitative PET during simultaneous PET-MR imaging in cardiology

Abstract

Background MR sequences used in the determination of PET linear attenuation coefficients (LAC) are a common procedure in simultaneous PET-MRI scanning. However during dynamic PET imaging, the introduction of gadolinium-based contrast agents (MRCA) at high concentrations during a dual injection of MRCA and PET radiotracer may cause attenuation effects of the PET radiotracer, and thus errors in quantification of dynamic images. Method We performed simultaneous PET-MR imaging of a phantom using increasing MRCA concentration from 0 to 65 mM (based on MRCA left ventricular concentration in a clinical study) mixed with water and 25 MBq of [18F]-FDG. LAC of the solution was calculated by a mixture rule and compared to measurements from CT images and automated MR LAC segmentation. The effect of increases in the resulting LAC over 0–65 mM was evaluated on a simulated image-derived arterial input function (IDIF) used in the PET kinetic model. Results From 0 to 46 mM, MR segmentation applied a LAC of 0.1 cm −1 , and at >46 mM the LAC = 0.0854 cm −1 due to T1 shortening effects. Our results show an increase of only 1.3% in the LAC of the solution over the range of 0–65 mM of MRCA, with an effect on the area under an IDIF of