Robust measurement of hepatic perfusion using an interleaved saturation prepared double echo sequence: comparison of dual-input and gradient models

K. G. Hollingsworth, M. J. Graves, D. J. Emmens, D. J. Lomas Radiology, University of Cambridge & Addenbrooke's Hospital, Cambridge, United Kingdom, Medical Physics, Addenbrooke's Hospital, Cambridge, United Kingdom Introduction Hepatic perfusion can be altered by the development of fibrosis and cirrhosis or lesions, and the ability to accurately quantify perfusion may be clinically significant [1]. In addition, assessment of liver perfusion (and perfusion heterogeneity) after orthotopic liver transplantation may indicate graft impairment. Perfusion measurements have been made with nuclear isotopes [2] or by the use of multi-phase CT acquisition and contrast agent [2,3]: such methods involve the use of ionising radiation. MRI (with Gd-DTPA) can be used in a similar way, but unlike CT, there is no linear relationship between the image intensity and contrast agent concentration. Since the liver is supplied by the hepatic artery and the portal vein, it is necessary to image contrast uptake in the aorta (as a substitute for hepatic artery), portal vein and liver parenchyma. MR images have a limited range of sensitivity to T1: imaging parameters which will be sensitive for uptake in the liver are not optimal for measuring the high concentrations in the aorta. This paper demonstrates a method of addressing this problem. Methods The study was approved by the local ethics review board and informed consent was obtained from the volunteers (3 male, 3 female, age 29-53). The volunteers fasted for 8 hours before the examination to ensure a basal portal vein flow. Examinations were performed on a 1.5T whole body MRI (Excite, GEHT, Milwaukee) using an 8 channel torso array. Pre-contrast measurements of T1 in the aorta, portal vein and liver parenchyma were made using a custom non-selective, saturationprepared, ECG-gated fast spoiled gradient echo with different saturation recovery times (11 points, TS = 200-5000ms) acquired in diastole. The dynamic uptake curves were acquired