From the Departments of Radiology (M.M.C.), Fetopathology (C.F.), and Obstetrics and Gynecology (J.C.J.), University Hospital Brugmann, Université Libre de Bruxelles, Place A. Van Gehuchten 4, 1020 Brussels, Belgium; Department of Radiology, University Hospital Gasthuisberg, Leuven, Belgium (F.D.K.); Department of Radiology, UZ Brussel, Vrije Universiteit Brussel, Brussels, Belgium (M.M.C., A.L., J.d.M., F.D.R., T.V.C., I.W.); and Animalarium, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium (S.V.L.).
Radiology. 2016 Jun;279(3):754-61. doi: 10.1148/radiol.2015151258. Epub 2015 Dec 1.
Purpose To determine the changes in temperature within the gravid miniature pig uterus during magnetic resonance (MR) imaging at 3 T. Materials and Methods The study received ethics committee approval for animal experimentation. Fiber-optic temperature sensors were inserted into the fetal brain, abdomen, bladder, and amniotic fluid of miniature pigs (second trimester, n = 2; third trimester, n = 2). In the first trimester (n = 2), the sensors were inserted only into the amniotic fluid (three sacs per miniature pig, for a total of six sacs). Imaging was performed with a 3-T MR imager by using different imaging protocols in a random order for animal, each lasting approximately 15 minutes. The first regimen consisted of common sequences used for human fetal MR examination, including normal specific absorption rate (SAR). The second regimen consisted of five low-SAR sequences, for which three gradient-echo sequences were interspersed with two diffusion-weighted imaging series. Finally, a high-SAR regimen maximized the radiofrequency energy deposition (constrained by the 2-W per kilogram of body weight SAR limitations) by using five single-shot turbo spin-echo sequences. Differences in temperature increases between the three regimens and between the three trimesters were evaluated by using one-way analysis of variance. The maximum cumulative temperature increase over 1 hour was also evaluated. Results Low-SAR regimens resulted in the lowest temperature increase (mean ± standard deviation, -0.03°C ± 0.20), normal regimens resulted in an intermediate increase (0.31°C ± 0.21), and high-SAR regimens resulted in the highest increase (0.56°C ± 0.20) (P < .0001). Mean temperature increase in the third trimester was 0.38°C ± 0.27, with no significant differences compared with the first (0.23°C ± 0.27) and second (0.25°C ± 0.32) trimesters (P = .07). The cumulative temperature increase over 1-hour imaging time with high SAR can reach 2.5°C. Conclusion In pregnant miniature pigs, the use of 3-T magnets for diagnostic MR imaging with normal SAR regimens does not lead to temperature increases above 1°C if imaging time is kept below 30 minutes. Longer imaging time, especially with high-SAR regimens, can lead to an increase of 2.5°C. (©) RSNA, 2015 Online supplemental material is available for this article.
在 3T 磁共振（MR）成像期间确定妊娠小型猪子宫内的温度变化。
该研究获得了动物实验伦理委员会的批准。光纤温度传感器插入到胎儿的大脑、腹部、膀胱和羊水中小猪（妊娠中期，n=2；妊娠晚期，n=2）。在妊娠早期（n=2），传感器仅插入羊水（每头小猪三个囊，共六个囊）。使用不同的成像方案以随机顺序对动物进行成像，每种方案持续约 15 分钟，在 3T MR 成像仪上进行。第一种方案包括用于人类胎儿 MR 检查的常规序列，包括正常特定吸收率（SAR）。第二种方案包括五个低 SAR 序列，其中三个梯度回波序列与两个弥散加权成像序列交错。最后，高 SAR 方案通过使用五个单次激发涡轮自旋回波序列最大限度地增加射频能量沉积（受 2W/kg 体重 SAR 限制的约束）。通过单向方差分析评估三种方案之间和三个三个月之间的温度升高差异。还评估了 1 小时内累积的最大温度升高。
低 SAR 方案导致最低的温度升高（平均值±标准偏差，-0.03°C±0.20），常规方案导致中等程度的升高（0.31°C±0.21），高 SAR 方案导致最高的升高（0.56°C±0.20）（P<.0001）。妊娠晚期的平均温度升高为 0.38°C±0.27，与妊娠早期（0.23°C±0.27）和妊娠中期（0.25°C±0.32）相比无显著差异（P=0.07）。高 SAR 下 1 小时成像时间的累积温度升高可达 2.5°C。
在妊娠小型猪中，如果将成像时间保持在 30 分钟以下，使用常规 SAR 方案的 3T 磁体进行诊断性磁共振成像不会导致温度升高超过 1°C。更长的成像时间，特别是使用高 SAR 方案，可导致温度升高 2.5°C。（©）RSNA，2015 在线补充材料可用于本文。
