Exposure to radiofrequency (RF) power deposition during magnetic resonance imaging (MRI) induces elevated body‐tissue temperatures and may cause changes in heart and breathing rates, disturbing thermoregulation. Eleven temperature sensors were placed in muscle tissue and one sensor in the rectum (measured in 10 cm depth) of 20 free‐breathing anesthetized pigs to verify temperature curves during RF exposure. Tissue temperatures and heart and breathing rates were measured before, during, and after RF exposure. Pigs were placed into a 60‐cm diameter whole‐body resonator of a 3 T MRI system. Nineteen anesthetized pigs were divided into four RF exposure groups: sham (0 W/kg), low‐exposure (2.7 W/kg, mean exposure time 56 min), moderate‐exposure (4.8 W/kg, mean exposure time 31 min), and high‐exposure (4.4 W/kg, mean exposure time 61 min). One pig was exposed to a whole‐body specific absorption rate (wbSAR) of 11.4 W/kg (extreme‐exposure). Hotspot temperatures, measured by sensor 2, increased by mean 5.0 ± 0.9°C, min 3.9; max 6.3 (low), 7.0 ± 2.3°C, min 4.6; max 9.9 (moderate), and 9.2 ± 4.4°C, min 6.1, max 17.9 (high) compared with 0.3 ± 0.3°C in the sham‐exposure group (min 0.1, max 0.6). Four time‐temperature curves were identified: sinusoidal, parabolic, plateau, and linear. These curve shapes did not correlate with RF intensity, rectal temperature, breathing rate, or heart rate. In all pigs, rectal temperatures increased (2.1 ± 0.9°C) during and even after RF exposure, while hotspot temperatures decreased after exposure. When rectal temperature increased by 1°C, hotspot temperature increased up to 42.8°C within 37 min (low‐exposure) or up to 43.8°C within 24 min (high‐exposure). Global wbSAR did not correlate with maximum hotspot. Bioelectromagnetics. 2021;42:37–50. © 2020 The Authors. Bioelectromagnetics published by Wiley Periodicals LLC on behalf of Bioelectromagnetics Society

中文翻译：

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3 T MRI 期间猪的温度 3 T (128 MHz) 体线圈射频功率沉积期间猪的温度、心率和呼吸频率

在磁共振成像 (MRI) 期间暴露于射频 (RF) 功率沉积会导致身体组织温度升高，并可能导致心脏和呼吸频率的变化，干扰体温调节。11 个温度传感器放置在肌肉组织中，1 个传感器放置在 20 头自由呼吸麻醉猪的直肠中（测量深度为 10 厘米），以验证射频暴露期间的温度曲线。在射频暴露之前、期间和之后测量组织温度以及心脏和呼吸频率。将猪放入直径为 60 厘米的 3 T MRI 系统全身谐振器中。19 只麻醉猪被分为四个射频暴露组：假（0 W/kg）、低暴露（2.7 W/kg，平均暴露时间 56 分钟）、中等暴露（4.8 W/kg，平均暴露时间 31 分钟）和高暴露（4.4 W/kg，平均暴露时间 61 分钟）。一头猪的全身比吸收率 (wbSAR) 为 11.4 W/kg（极端暴露）。由传感器 2 测量的热点温度平均增加 5.0 ± 0.9°C，最小 3.9；最高 6.3（低），7.0 ± 2.3°C，最低 4.6；最高 9.9（中度）和 9.2 ± 4.4°C，最低 6.1，最高 17.9（高），而假暴露组为 0.3 ± 0.3°C（最低 0.1，最高 0.6）。确定了四种时间-温度曲线：正弦曲线、抛物线曲线、平台曲线和线性曲线。这些曲线形状与射频强度、直肠温度、呼吸频率或心率无关。在所有猪中，在射频暴露期间甚至之后，直肠温度都会升高 (2.1 ± 0.9°C)，而在暴露后热点温度会降低。当直肠温度升高 1°C 时，热点温度在 37 分钟（低暴露）内升高至 42.8°C 或高达 43。24 分钟内 8°C（高曝光）。全球 wbSAR 与最大热点不相关。生物电磁学。2021；42:37-50。© 2020 作者。由 Wiley Periodicals LLC 代表 Bioelectromagnetics Society 出版的 Bioelectromagnetics