Non-contrast-enhanced hepatic MR angiography with true steady-state free-precession and time spatial labeling inversion pulse: Optimization of the technique and preliminary results

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Purpose:To compare and evaluate images acquired with two different MR angiography (MRA) sequences, three-dimensional (3D) half-Fourier fast spin-echo (FSE) and 3D true steady-state free-precession (SSFP) combined with two time-spatial labeling inversion pulses (T-SLIPs), for selective and non-contrast-enhanced (non-CE) visualization of the portal vein. Materials and Methods:Twenty healthy volunteers were examined using half-Fourier FSE and true SSFP sequences on a 1.5T MRI system with two T-SLIPs, one placed on the liver and thorax, and the other on the lower abdomen. For quantitative analysis, vessel-to-liver contrast (Cv-l) ratios of the main portal vein (MPV), right portal vein (RPV), and left portal vein (LPV) were measured. The quality of visualization was also evaluated. Results:In both pulse sequences, selective visualization of the portal vein was successfully conducted in all 20 volunteers. Quantitative evaluation showed significantly better Cv-l at the RPVs and LPVs in half-Fourier FSE (P Ͻ 0.0001). At the MPV, Cv-l was better in true SSFP, but was not statistically different. Visualization scores were significantly better only at branches of segments four and eight for half-Fourier FSE (P ϭ 0.001 and 0.03, respectively). Conclusion:Both 3D half-Fourier FSE and true SSFP scans with T-SLIPs enabled selective non-CE visualization of the portal vein. Half-Fourier FSE was considered appropriate for intrahepatic portal vein visualization, and true SSFP may be preferable when visualization of the MPV is required.

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Non‐contrast‐enhanced MR portography with time‐spatial labeling inversion pulses: Comparison of imaging with three‐dimensional half‐fourier fast spin‐echo and true steady‐state free‐precession sequences

Shimada

Isoda

Okada

et al. 2009

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Non‐contrast‐enhanced MR angiography for selective visualization of the hepatic vein and inferior vena cava with true steady‐state free‐precession sequence and time‐spatial labeling inversion pulses: Preliminary results

Shimada

Isoda

Okada

et al. 2009

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Purpose:To selectively visualize the hepatic vein and inferior vena cava (IVC) using three-dimensional (3D) true steady-state free-precession (SSFP) MR angiography with time-spatial labeling inversion pulse (T-SLIP), and to optimize the acquisition protocol. Materials and Methods:Respiratory-gated 3D true SSFP scans were conducted in 23 subjects in combination with two different T-SLIPs (one placed in the thorax to suppress the arterial signal and the other in the abdomen to suppress the portal venous signal). One of the most important factors was the inversion time (TI) of abdominal T-SLIP, and the image quality was evaluated at four different TIs of 800, 1200, 1600, and 2000 msec in terms of relative signal-tonoise ratio (SNR), contrast-to-noise ratio (CNR), and mean visualization scores.Results: No significant difference was observed in SNR and CNR between each TI. However, IVC visualization scores were better at TIs of 1600 and 2000 msec, and overall image quality was better at TIs of 1200 and 1600 msec. Therefore, the TI of 1600 msec was considered to provide the optimal balance between IVC visualization and signal suppression of the portal vein in our protocol. THE HEPATIC VENOUS ANATOMY must be evaluated in detail before hepatectomy. Contrast-enhanced (CE) angiography with computed tomography (CT) or magnetic resonance imaging (MRI) is the standard and noninvasive procedure for this purpose (1,2). However, both CT and MR contrast agents have various side effects, including anaphylactic shock. In addition, they can be nephrotoxic and should not be administered to patients with decreased renal function (3). Conventional flow-based MR angiography (MRA) techniques, such as time-of-flight or phase-contrast imaging, do not require contrast agents, but have not been used successfully for hepatic venous visualization owing to overlap of the hepatic artery and the portal vein (4). Recently, non-CE MRA techniques such as fast advanced spin echo (FASE) and true steady-state free-precession (SSFP) have made rapid progress, and have been used effectively for the selective visualization of the coronary artery, renal artery, and peripheral vessels (5-7). ConclusionTrue SSFP is a fast MR technique that has been widely used in cardiac imaging. It has a high signal-tonoise ratio (SNR) per unit time (8) and can produce an image with high resolution. Steady-state precession with a fully balanced gradient waveform is used to recycle steady-state magnetization in long-T2 species. The steady-state signal is dependent on the T2-to-T1 ratio, which is relatively high for blood and has been used successfully in vascular imaging (9,10). It allows visualization of the vessels without the use of an intravenous contrast medium in a short acquisition time. However, with this technique alone, it is difficult to selectively visualize the hepatic vein and inferior vena

Non‐contrast enhanced MR angiography: Established techniques

Miyazaki

Akahane

2011

123

Until recently, time‐of‐flight (TOF) and phase contrast (PC) were the only non‐contrast MR angiography (NC‐MRA) techniques practically used in clinical. In the decade, NC‐MRA have been gained a revival of an interest among the MR researchers and scientists, in part because of safety concerns related to the possible link between gadolinium‐based contrast agents and nephrogenic systemic fibrosis (NSF). This article introduces other established NC‐MRA techniques, such as ECG‐gated partial Fourier fast spin echo (FSE) and balanced steady‐state free precession (bSSFP), both with and without arterial spin labeling. Then, the article focuses on two main applications: peripheral run‐off and renal MRA. Recently, both applications have achieved remarkable advancements and have become a viable clinical option as an alternative to contrast‐enhanced (CE)‐MRA. In addition, developments on the horizon including whole body MRA applications and further advancement at 3 Tesla are discussed. J. Magn. Reson. Imaging 2012;35:1‐19. © 2011 Wiley Periodicals, Inc.