Department of Medical Biophysics, Western University, London, Ontario, Canada.
Department of Biomedical Engineering, Western University, London, Ontario, Canada.
J Magn Reson Imaging. 2021 Jul;54(1):113-121. doi: 10.1002/jmri.27547. Epub 2021 Feb 15.
Despite its many advantages, experience with fetal magnetic resonance imaging (MRI) is limited, as is knowledge of how fetal tissue relaxation times change with gestational age (GA). Quantification of fetal tissue relaxation times as a function of GA provides insight into tissue changes during fetal development and facilitates comparison of images across time and subjects. This, therefore, can allow the determination of biophysical tissue parameters that may have clinical utility.
To demonstrate the feasibility of quantifying previously unknown T and T relaxation times of fetal tissues in uncomplicated pregnancies as a function of GA at 1.5 T.
Pilot.
Nine women with singleton, uncomplicated pregnancies (28-38 weeks GA).
FIELD STRENGTH/SEQUENCE: All participants underwent two iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL-IQ) acquisitions at different flip angles (6° and 20°) at 1.5 T.
Segmentations of the lungs, liver, spleen, kidneys, muscle, and adipose tissue (AT) were conducted using water-only images and proton density fat fraction maps. Driven equilibrium single pulse observation of T (DESPOT ) was used to quantify the mean water T of the lungs, intraabdominal organs, and muscle, and the mean water and lipid T of AT. IDEAL T maps were used to quantify the T values of the lungs, intraabdominal organs, and muscle.
F-tests were performed to assess the T and T changes of each analyzed tissue as a function of GA.
No tissue demonstrated a significant change in T as a function of GA (lungs [P = 0.89]; liver [P = 0.14]; spleen [P = 0.59]; kidneys [P = 0.97]; muscle [P = 0.22]; AT: water [P = 0.36] and lipid [P = 0.14]). Only the spleen and muscle T showed a significant decrease as a function of GA (lungs [P = 0.67); liver [P = 0.05]; spleen [P < 0.05]; kidneys [P = 0.70]; muscle [P < 0.05]).
These preliminary data suggest that the T of the investigated tissues is relatively stable over 28-38 weeks GA, while the T change in spleen and muscle decreases significantly in that period.
3 TECHNICAL EFFICACY STAGE: 2.
尽管胎儿磁共振成像（MRI）有许多优势，但经验有限，对胎儿组织弛豫时间随胎龄（GA）变化的了解也有限。定量分析 GA 时胎儿组织的弛豫时间可以深入了解胎儿发育过程中的组织变化，并有助于跨时间和受试者比较图像。因此，可以确定可能具有临床应用价值的生物物理组织参数。
在 1.5T 下证明定量分析正常妊娠胎儿组织未知 T 和 T 弛豫时间随 GA 变化的可行性。
初步研究。
9 名单胎、正常妊娠（GA 28-38 周）女性。
磁场强度/序列：所有参与者均在 1.5T 下进行两次迭代水脂分离与回波不对称最小二乘估计（IDEAL-IQ）采集，采用不同翻转角（6°和 20°）。
使用仅含水图像和质子密度脂肪分数图对肺、肝、脾、肾、肌肉和脂肪组织（AT）进行分割。利用均衡单脉冲观察 T（DESPOT）定量分析肺、腹腔器官和肌肉的平均水 T，以及 AT 的平均水和脂质 T。使用 IDEAL T 图定量分析肺、腹腔器官和肌肉的 T 值。
采用 F 检验评估随 GA 变化各分析组织的 T 和 T 变化。
没有组织的 T 值随 GA 变化有显著差异（肺[P=0.89]；肝[P=0.14]；脾[P=0.59]；肾[P=0.97]；肌肉[P=0.22]；AT：水[P=0.36]和脂质[P=0.14]）。只有脾和肌肉 T 随 GA 变化有显著下降（肺[P=0.67]；肝[P=0.05]；脾[P<0.05]；肾[P=0.70]；肌肉[P<0.05]）。
这些初步数据表明，在所研究的组织中，T 值在 28-38 周 GA 期间相对稳定，而脾和肌肉的 T 值在该期间显著下降。
3 技术功效分期：2。
