Budjan Johannes, Riffel Philipp, Ong Melissa M, Schoenberg Stefan O, Attenberger Ulrike I, Hausmann Daniel
Department of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany.
BMC Med Imaging. 2017 May 9;17(1):32. doi: 10.1186/s12880-017-0203-y.
Hepatocyte-specific gadolinium based contrast agents (HSCA) provide substantial information for the classification of liver lesions in magnetic resonance imaging (MRI). However, breathing artifacts which reduce image quality and diagnostic confidence of hepatobiliary phase acquisitions are regularly observed in clinical routine. The aim of this study was to evaluate two approaches to reduce breathing artifacts for hepatobiliary phase imaging.
Twenty minutes after administration of a HSCA (gadoxetic acid), a T1-weighted VIBE sequence with radial k-space sampling (radialVIBE, 180 s acquisition time in free breathing) and a highly accelerated Cartesian VIBE with Dixon fat separation (CD-VIBE, CAIPIRINHA acceleration with r = 2 × 2, breath-hold 8-10 s) were acquired in 35 patients (12 female, 57 ± 13 years), who showed breath-holding difficulties in early phases of the examinations. Image quality (image sharpness, noise, artifacts, homogeneity of fat saturation, bile duct delineation and overall image quality) as well as conspicuity and liver-to-lesion signal intensity (SI) ratios of focal liver lesions were assessed for both radial- and CD-VIBE.
Overall image quality was rated good to excellent for both sequences, while CD-VIBE was preferred in most cases. Though radialVIBE received better results regarding image noise and artifacts, both sequences were rated equally regarding bile duct delineation and sharpness. Focal liver lesion (n = 42) conspicuity was rated significantly better and SI-ratios were significantly higher on CD-VIBE (2.45 ± 1.44 vs. 1.61 ± 0.70 in radialVIBE, p = 0.0001). In three patients, CD-VIBE was rated non-diagnostic due to severe breathing artifacts, while radialVIBE was diagnostic in those patients.
Both highly accelerated Cartesian as well as radial acquisition techniques provide good to excellent image quality in hepatobiliary phase MRI. In comparison, CD-VIBE offered better overall image quality and liver lesion conspicuity. However, radialVIBE was a valuable alternative in patients unable to sustain even short breath-hold intervals. Further studies including lager patient cohorts are desirable to allow a transfer of these results to a general patient population.
基于钆的肝细胞特异性对比剂（HSCA）为磁共振成像（MRI）中肝脏病变的分类提供了大量信息。然而，在临床常规检查中经常会观察到呼吸伪影，这会降低肝胆期采集图像的质量和诊断可信度。本研究的目的是评估两种减少肝胆期成像呼吸伪影的方法。
在给予HSCA（钆塞酸）20分钟后，对35例患者（12例女性，年龄57±13岁）进行了具有径向k空间采样的T1加权VIBE序列（radialVIBE，自由呼吸下采集时间为180秒）和具有狄克逊脂肪分离的高度加速笛卡尔VIBE序列（CD-VIBE，CAIPIRINHA加速，r = 2×2，屏气8 - 10秒），这些患者在检查早期存在屏气困难。对radialVIBE和CD-VIBE序列的图像质量（图像清晰度、噪声、伪影、脂肪抑制均匀性、胆管轮廓和整体图像质量）以及局灶性肝病变的显眼程度和肝脏与病变的信号强度（SI）比值进行了评估。
两个序列的整体图像质量均被评为良好至优秀，而在大多数情况下更倾向于CD-VIBE。虽然radialVIBE在图像噪声和伪影方面获得了更好的结果，但在胆管轮廓和清晰度方面两个序列的评分相同。CD-VIBE上局灶性肝病变（n = 42）的显眼程度评分明显更高，SI比值也明显更高（radialVIBE中为1.61±0.70，CD-VIBE中为2.45±1.44，p = 0.0001）。在三名患者中，CD-VIBE由于严重的呼吸伪影被评为无法诊断，而radialVIBE在这些患者中具有诊断价值。
高度加速的笛卡尔采集技术和径向采集技术在肝胆期MRI中均能提供良好至优秀的图像质量。相比之下，CD-VIBE提供了更好的整体图像质量和肝病变显眼程度。然而，对于无法维持即使很短屏气时间间隔的患者，radialVIBE是一种有价值的替代方法。需要包括更大患者队列的进一步研究，以便将这些结果推广到一般患者群体。
