Tipirneni-Sajja Aaryani, Krafft Axel J, McCarville M Beth, Loeffler Ralf B, Song Ruitian, Hankins Jane S, Hillenbrand Claudia M
1 Department of Diagnostic Imaging, St. Jude Children's Research Hospital, 262 Danny Thomas Pl, Memphis, TN 38105-3678.
2 Department of Biomedical Engineering, University of Memphis, Memphis, TN.
AJR Am J Roentgenol. 2017 Jul;209(1):187-194. doi: 10.2214/AJR.16.17183. Epub 2017 May 15.
The objective of this study is to evaluate radial free-breathing (FB) multiecho ultrashort TE (UTE) imaging as an alternative to Cartesian FB multiecho gradient-recalled echo (GRE) imaging for quantitative assessment of hepatic iron content (HIC) in sedated patients and subjects unable to perform breath-hold (BH) maneuvers.
FB multiecho GRE imaging and FB multiecho UTE imaging were conducted for 46 test group patients with iron overload who could not complete BH maneuvers (38 patients were sedated, and eight were not sedated) and 16 control patients who could complete BH maneuvers. Control patients also underwent standard BH multiecho GRE imaging. Quantitative R2* maps were calculated, and mean liver R2* values and coefficients of variation (CVs) for different acquisitions and patient groups were compared using statistical analysis.
FB multiecho GRE images displayed motion artifacts and significantly lower R2* values, compared with standard BH multiecho GRE images and FB multiecho UTE images in the control cohort and FB multiecho UTE images in the test cohort. In contrast, FB multiecho UTE images produced artifact-free R2* maps, and mean R2* values were not significantly different from those measured by BH multiecho GRE imaging. Motion artifacts on FB multiecho GRE images resulted in an R2* CV that was approximately twofold higher than the R2* CV from BH multiecho GRE imaging and FB multiecho UTE imaging. The R2* CV was relatively constant over the range of R2* values for FB multiecho UTE, but it increased with increases in R2* for FB multiecho GRE imaging, reflecting that motion artifacts had a stronger impact on R2* estimation with increasing iron burden.
FB multiecho UTE imaging was less motion sensitive because of radial sampling, produced excellent image quality, and yielded accurate R2* estimates within the same acquisition time used for multiaveraged FB multiecho GRE imaging. Thus, FB multiecho UTE imaging is a viable alternative for accurate HIC assessment in sedated children and patients who cannot complete BH maneuvers.
本研究的目的是评估径向自由呼吸（FB）多回波超短TE（UTE）成像，作为笛卡尔FB多回波梯度回波（GRE）成像的替代方法，用于对镇静患者和无法进行屏气（BH）动作的受试者的肝脏铁含量（HIC）进行定量评估。
对46例无法完成BH动作的铁过载试验组患者（38例为镇静患者，8例为未镇静患者）和16例能够完成BH动作的对照患者进行了FB多回波GRE成像和FB多回波UTE成像。对照患者还接受了标准的BH多回波GRE成像。计算定量R2图，并使用统计分析比较不同采集方式和患者组的平均肝脏R2值及变异系数（CV）。
与对照队列中的标准BH多回波GRE图像和FB多回波UTE图像以及试验队列中的FB多回波UTE图像相比，FB多回波GRE图像显示出运动伪影且R2值显著更低。相比之下，FB多回波UTE图像生成了无伪影的R2图，且平均R2值与BH多回波GRE成像测量值无显著差异。FB多回波GRE图像上的运动伪影导致R2的CV比BH多回波GRE成像和FB多回波UTE成像的R2* CV高出约两倍。对于FB多回波UTE，R2* CV在R2值范围内相对恒定，但对于FB多回波GRE成像，它随R2增加而增加，这反映出随着铁负荷增加，运动伪影对R2*估计的影响更强。
由于采用径向采样，FB多回波UTE成像对运动的敏感性较低，产生了优异的图像质量，并在与多平均FB多回波GRE成像相同的采集时间内获得了准确的R2*估计值。因此，FB多回波UTE成像是对镇静儿童和无法完成BH动作的患者进行准确HIC评估的可行替代方法。
