Hedderich Dennis M, Weiss Kilian, Spiro Judith E, Giese Daniel, Beck Gabriele M, Maintz David, Persigehl Thorsten
Department of Radiology, University Hospital Cologne, Germany.
Department of Diagnostic and Interventional Neuroradiology, Klinikum rechts der Isar, Technical University Munich, Munich, Germany.
Rofo. 2018 Jul;190(7):601-609. doi: 10.1055/s-0044-101263. Epub 2018 Mar 13.
Contrast-enhanced T1-weighted MR imaging of the liver is typically acquired using breath-hold techniques to reduce motion artifacts and to allow for optimal diagnostic image quality. Insufficient breath-holds during MR data collection can cause severe reduction of image quality up to the point of being non-diagnostic. The aim of this study was to evaluate the subjective and objective clinical image quality of a novel free-breathing radial k-space sampling MR technique.
Consent for this study was given by the local IRB committee. 86 patients who underwent both breath-hold (BH) and free-breathing (FB) late-phase contrast T1w-FS-FFE liver MRI using conventional BH Cartesian (Cartesian-eTHRIVE) and FB "pseudo golden angle" radial k-space sampling (Radial-eTHRIVE) were included in this retrospective analysis. Subjective analysis comprised 5-point Likert scale ratings (1 = very good; 5 = non-diagnostic) for "artifact impact", "anatomic sharpness", "vessel sharpness", "contrast impression", and "overall diagnostic quality". Relative signal intensities in different ROIs were compared between Cartesian-eTHRIVE and Radial-eTHRIVE. For statistical differences paired Wilcoxon test and paired t-test have been performed (p < 0.05).
The MR scan time was significantly longer for FB Radial-eTHRIVE (2 min, 54 s) compared to BH Cartesian-eTHRIVE (0 min 15 s). Cartesian-eTHRIVE demonstrated a superior subjective contrast impression and objective measurements revealed an increased lesion-to-liver-contrast for hypointense liver lesions (Hypo-LTLC: 0.33 ± 0.19 vs. 0.20 ± 0.11; p = 0.000), while no difference was observed for hyperintense liver lesions (Hyper-LTLC). Subjective evaluation showed superior anatomic sharpness ratings by both readers for Radial-eTHRIVE. Most importantly, in a subgroup analysis of patients who were unable to perform adequate breath-holds, free-breathing Radial-eTHRIVE still demonstrated good subjective image quality.
Free-breathing, radial k-space sampling T1w MRI of the liver delivers high diagnostic image quality, especially in patients who are unable to adequately perform breath-hold maneuvers. Thus, Radial-eTHRIVE can be an important clinical alternative in patients with impaired respiration status.
· Delayed-phase contrast-enhanced MRI of the liver can be robustly performed using a "pseudo golden angle" Radial-eTHRIVE sequence.. · Free-breathing Radial-eTHRIVE yields good diagnostic image quality in case of a high artifact burden in breath-hold Cartesian-eTHRIVE and thus could be used as a "back-up" for patients with impaired respiratory capacity.. · A lower lesion-to-liver-contrast ratio is observed for hypointense liver lesions in free-breathing Radial-eTHRIVE sequence..
· Hedderich DM, Weiss K, Spiro JE et al. Clinical Evaluation of Free-Breathing Contrast-Enhanced T1w MRI of the Liver using Pseudo Golden Angle Radial k-Space Sampling. Fortschr Röntgenstr 2018; 190: 601 - 609.
肝脏对比增强T1加权磁共振成像通常采用屏气技术进行采集，以减少运动伪影并获得最佳诊断图像质量。磁共振数据采集期间屏气不足会导致图像质量严重下降，甚至无法诊断。本研究旨在评估一种新型自由呼吸径向k空间采样磁共振技术的主观和客观临床图像质量。
本研究获得当地机构审查委员会的批准。86例患者同时接受了屏气（BH）和自由呼吸（FB）晚期对比增强T1加权脂肪抑制快速场回波肝脏磁共振成像，分别采用传统的屏气笛卡尔（笛卡尔-eTHRIVE）和自由呼吸“伪黄金角”径向k空间采样（径向-eTHRIVE）。主观分析采用5级李克特量表对“伪影影响”“解剖清晰度”“血管清晰度”“对比效果”和“整体诊断质量”进行评分（1=非常好；5=无法诊断）。比较笛卡尔-eTHRIVE和径向-eTHRIVE不同感兴趣区域的相对信号强度。采用配对Wilcoxon检验和配对t检验进行统计学差异分析（p<0.05）。
与屏气笛卡尔-eTHRIVE（0分15秒）相比，自由呼吸径向-eTHRIVE的磁共振扫描时间明显更长（2分54秒）。笛卡尔-eTHRIVE显示出更好的主观对比效果，客观测量显示低信号肝脏病变的病变-肝脏对比度增加（低信号病变-肝脏对比度：0.33±0.19对0.20±0.11；p=0.000），而高信号肝脏病变（高信号病变-肝脏对比度）无差异。主观评估显示两位阅片者对径向-eTHRIVE的解剖清晰度评分更高。最重要的是，在对无法进行充分屏气的患者进行的亚组分析中，自由呼吸径向-eTHRIVE仍显示出良好的主观图像质量。
肝脏自由呼吸径向k空间采样T1加权磁共振成像具有较高的诊断图像质量，尤其适用于无法充分进行屏气动作的患者。因此，径向-eTHRIVE对于呼吸功能受损的患者可能是一种重要的临床替代方法。
· 使用“伪黄金角”径向-eTHRIVE序列可稳健地进行肝脏延迟期对比增强磁共振成像。· 在屏气笛卡尔-eTHRIVE伪影负担较高的情况下，自由呼吸径向-eTHRIVE可产生良好的诊断图像质量，因此可作为呼吸功能受损患者的“备用”方法。· 在自由呼吸径向-eTHRIVE序列中，低信号肝脏病变的病变-肝脏对比度较低。
· Hedderich DM, Weiss K, Spiro JE等。使用伪黄金角径向k空间采样对肝脏自由呼吸对比增强T1加权磁共振成像的临床评估。Fortschr Röntgenstr 2018; 190: 601 - 609。
