Effects of in vivo Flip Angle Variations on the Accuracy of DCE-MRI Perfusion Parameters at 1 . 5 T and 3 . 0 T

Introduction: Dynamic contrast-enhanced (DCE)-MRI of tumors has emerged as one of the prime methods for assessing the effectiveness of antiangiogenic and antivascular agents. In DCE-MRI, a dynamic series of T1-weighted images is acquired during intravenous bolus injection of a contrast agent and the measured signal subsequently fitted to a model to quantify perfusion parameters, such as K and ve. During the fitting procedure, most current studies assume that the prescribed nominal flip angles are accurately played out. It was previously shown that large flip angle variations can exist throughout the FOV which can cause substantial errors in perfusion measurements in coronal sections of the body on a standard 1.5T MRI system [1]. In this work, we compare the flip angle variations and its effects on the accuracy of K and ve for different orientation planes on three different scanners: standard 1.5T and 3.0T systems (Siemens Sonata and Trio), as well as on a short-bore 1.5T system (Siemens Espree) to determine whether higher fields and short bore systems potentially exacerbates these measurement inaccuracies.