Unenhanced MR portography with a half-Fourier fast spin-echo sequence and time-space labeling inversion pulses: preliminary results.

Abstract

For this study, we aimed to selectively visualize the intrahepatic portal veins using 3D half-Fourier fast spin-echo (FSE) MR angiography (MRA) with a time-space labeling inversion pulse (T-SLIP) and to optimize the acquisition protocol. Respiratory-triggered 3D half-Fourier FSE scans were obtained in 25 healthy adult subjects combined with two different T-SLIPs: one placed on the liver and the thorax to suppress signals of the liver parenchyma, hepatic veins, and abdominal arteries and the other on the lower abdomen to suppress the ascending signal of the inferior vena cava. One of the most important factors was the inversion time (TI) of the inversion pulse for the liver and thorax. Image quality was evaluated in terms of signal-to-noise ratio, contrast-to-noise ratio, and mean visualization scores at four different TIs: 800, 1,200, 1,600, and 2,000 milliseconds. Selective visualization of the portal vein was successfully achieved in all volunteers, and anatomic variations were also seen in three subjects. A TI of 1,200 milliseconds was optimal in our protocol because it was sufficient for peripheral portal vein visualization and was most suitable for signal suppression of the hepatic veins and liver parenchyma. Half-Fourier FSE scanning with T-SLIPs enabled selective visualization of the portal vein without an exogenous contrast agent.