Yetisir Filiz, Abaci Turk Esra, Feldman Henry A, Gagoski Borjan, Didier Ryne A, Barnewolt Carol, Estroff Judy A, Wald Lawrence L, Adalsteinsson Elfar, Grant P Ellen
Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA.
Fetal Neonatal Neuroimaging and Developmental Science Center, Boston Children's Hospital, Boston, Massachusetts, USA.
J Magn Reson Imaging. 2025 Sep;62(3):844-853. doi: 10.1002/jmri.29797. Epub 2025 Apr 17.
3-T MRI can improve image quality of fetal imaging compared to 1.5-T MRI. However, concerns exist regarding increased local tissue heating at 3-T.
To assess fetal MRI radiofrequency (RF) safety at 3-T by comparing simulated tissue heating to 1.5-T (using constant RF exposure) and by simulating tissue heating at 3-T using RF exposures from clinical fetal examinations.
Retrospective.
Seven voxelized anatomical pregnant body models (gestational age [GA] 30 ± 3 weeks [mean ± standard deviation], maternal body mass index [BMI] 27.8 ± 8.5 kg/m) were used. Maternal whole-body average specific absorption rate (wbSAR) logs were collected from 85 clinical examinations at 3-T (GA 25 ± 6 weeks, BMI 30.3 ± 6.8 kg/m).
FIELD STRENGTH/SEQUENCE: 3-T, 1.5-T, HASTE, VIBE, TRUFISP, EPI, DTI.
Simulated maternal and fetal peak and average SAR, temperature, and peak thermal dose were compared at 3-T and 1.5-T for 60 min 2 W/kg wbSAR using 7 body models and a 16-rung band-pass RF coil. Temperature and thermal dose were simulated in one body model using clinical wbSAR exposures at 3-T.
Factorial analysis of variance was performed using 28 maternal and fetal temperature measurements from 7 body models to detect a difference between 3-T and 1.5-T. p < 0.05 was considered statistically significant.
For constant RF exposure, we found no difference between 3-T and 1.5-T in peak maternal (1.5-T:40.38 ± 0.21°C; 3-T:40.40 ± 0.20°C; p = 0.85), peak fetal (1.5-T:39.21 ± 0.17°C; 3-T:39.09 ± 0.16°C; p = 0.19), and average maternal (1.5-T:37.32 ± 0.05°C; 3-T:37.33 ± 0.04°C; p = 0.68) temperature. We observed significantly higher average fetal temperatures at 1.5-T (1.5-T:37.75 ± 0.06°C; 3-T:37.70 ± 0.05°C). For 3-T clinical RF exposures, simulated peak temperatures exceeded the recommended limits. However, the thermal dose was below the recommended limit.
For the same RF coil geometry, local heating was similar at 3-T and 1.5-T for constant RF exposure. Although realistic 3-T RF exposures could cause peak temperatures above the recommended limits, thermal dose was below the recommended limit.
Stage 1.
与1.5-T磁共振成像（MRI）相比，3-T MRI可提高胎儿成像的图像质量。然而，人们担心3-T时局部组织发热会增加。
通过比较模拟组织加热与1.5-T时的情况（使用恒定射频暴露），以及使用临床胎儿检查的射频暴露模拟3-T时的组织加热，来评估3-T时胎儿MRI射频（RF）安全性。
回顾性研究。
使用了7个体素化的怀孕人体解剖模型（孕周[GA]30±3周[均值±标准差]，孕妇体重指数[BMI]27.8±8.5kg/m²）。从3-T时的85例临床检查（GA 25±6周，BMI 30.3±6.8kg/m²）中收集孕妇全身平均比吸收率（wbSAR）记录。
场强/序列：3-T、1.5-T、快速自旋回波（HASTE）、容积内插屏气检查（VIBE）、真实快速成像稳态进动序列（TRUFISP）、回波平面成像（EPI）、扩散张量成像（DTI）。
使用7个身体模型和一个16 rung带通射频线圈，比较3-T和1.5-T时持续60分钟、2W/kg wbSAR情况下模拟的孕妇和胎儿的峰值及平均比吸收率、温度和峰值热剂量。使用3-T时的临床wbSAR暴露，在一个身体模型中模拟温度和热剂量。
使用来自7个身体模型的28次孕妇和胎儿温度测量值进行析因方差分析，以检测3-T和1.5-T之间的差异。p<0.05被认为具有统计学意义。
对于恒定射频暴露，我们发现3-T和l.5-T时孕妇峰值温度（1.5-T：40.38±0.21°C；3-T：40.40±0.20°C；p=0.85）、胎儿峰值温度（1.5-T：39.21±0.17°C；3-T：39.09±0.16°C；p=0.19）和孕妇平均温度（1.5-T：37.32±0.05°C；3-T：37.33±0.04°C；p=0.68）没有差异。我们观察到1.5-T时胎儿平均温度显著更高（1.5-T：37.75±0.06°C；3-T：37.70±0.05°C）。对于3-T临床射频暴露，模拟的峰值温度超过了推荐限值。然而，热剂量低于推荐限值。
对于相同的射频线圈几何形状，在恒定射频暴露下，3-T和1.5-T时的局部加热相似。尽管实际的3-T射频暴露可能导致峰值温度高于推荐限值，但热剂量低于推荐限值。
1级。
1级。
