Flow-sensitive 4D MR imaging may constitute a promising, alternative technique to Doppler US for evaluating hemodynamics in the portal venous system of patients with liver cirrhosis and may be a means of assessing pathologic changes in flow characteristics.

Purpose: To qualitatively and quantitatively evaluate the image quality in accelerated time-resolved 3D contrastenhanced MR angiography (tr-CE-MRA) at 3T. Materials and Methods:In all, 113 MRA were performed in 107 patients on a 3T MR system after written informed consent and approval by the ethics committee. Twenty consecutive thoracic (n ϭ 87) or craniocervical (n ϭ 26) 3D data volumes were acquired. The timeframes with maximum arterial and venous contrast were determined and a total of 663 arterial and venous segments were analyzed by two blinded observers. Diagnostic image quality was graded by applying a 0 (low) to 3 (excellent) scale. Additionally, local signal-to-noise (SNR) and contrast-to-noise ratios (relative CNR) were evaluated.Results: Tr-CE-MRA was successfully performed in all patients. Good to excellent image quality (2.42 Ϯ 0.31) was observed in all individuals with preserved discrimination of arteries (2.43 Ϯ 0.48) and veins (2.20 Ϯ 0.56). Minor image degradation due to artifacts (2.62 Ϯ 0.25) and constantly high vascular signal and contrast were detected. There was a significant superiority of coronal orientation during thoracic MRA (P Ͻ 0.05). In 18 cases tr-CE-MRA provided additional information on vascular pathologies. Conclusion:Large field of view tr-CE-MRA enables constantly high-quality thoracic and craniocervical angiographies. In addition, the dynamics of tr-CE-MRA can offer additional information on vascular pathologies. OVER THE LAST DECADE, improvements in methodology have provided image acceleration techniques such as parallel imaging (1), view sharing (2-4), and partial Fourier transformation (5) that are highly beneficial for magnetic resonance (MR) image acquisition. Particularly for fast T1-weighted imaging, eg, in contrast-enhanced MR angiography (CE-MRA), the combination of such image acceleration methods provides faster acquisition schemes for improved sequence protocols with optimized spatial and/or temporal resolution. Based on a constant total acquisition time and a given spatial resolution, the temporal update rate can be increased to allow for dynamic angiographic imaging.Time-resolved imaging such as dynamic projection angiographies (6,7) and fully 3D sampling schemes (8) were presented as early as 1996. Time-resolved contrast-enhanced 3D MR-angiography (tr-CE-MRA) is constantly gaining importance since the protocols are easy to use in clinical routine, ie, no additional bolus timing and time-consuming sequence adjustments are necessary and the protocol can principally be performed without breath-hold. Furthermore, tr-CE-MRA techniques provide good separation between arteries and veins, and may offer additional "dynamic" information on the contrast agent distribution over time.Previous studies have shown that CE-MRA can benefit from imaging at 3T. In addition to the potential twofold increase in signal-to-noise ratio (SNR) (9), vessel contrast can be further enhanced due to the decrease of T1 relaxation times and thus enhanced T1 shortening effect of gadolinium (Gd)-b...

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