この研究は、高磁界（4.7 T）磁気共鳴画像（MRI）条件への子宮内ばく露が、マウスの胎仔の成長、成体の成長、および精巣の発達に与える影響を調べた。妊娠9日目および/または12日目に、8時間ばく露が行われた。また、9日目には1 MHz連続波の非収束超音波を用いた組み合わせばく露、12日目にはMRIを用いた組み合わせばく露の影響も調べた。各ばく露群は8-10匹の妊娠マウスで構成された。胎仔データは妊娠18日目に、子宮内ばく露を受けた成獣のデータを出生後50日目に収集した。その結果、複雑なMRI電磁界条件への子宮内ばく露後の敏感な生物学的エンドポイントにおいて有意差が見られた；ばく露群の胎仔重量は、ケージ対照群および擬似ばく露群の胎仔に比べ、11 %（9日目のMRI）から17 %（9日目の超音波/ 12日目のMRI）の範囲で低かった（p <または= .05）；ばく露群の頭臀長は8 %短かった（p <または= .05）；分娩後死亡率は、妊娠9日目と12日目のMRIばく露群において38 %高かった（p <または= .05）；妊娠12日目にMRIばく露を受けた成獣では、毎日の精子産生が44 %減少した（p <または= .05）;成獣オスの精巣の重量と体積にも減少が見られたが、有意ではなかった；胎仔死亡、性比、50日目の体重、脾臓重量、または精嚢重量に影響は見られなかった、と報告している。
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To study the effects of exposure in utero to high field (4.7 Tesla) magnetic resonance imaging conditions on fetal growth, adult growth, and testicular development in the mouse.
Exposures of 8 h duration were made on day 9 and/or day 12 of gestation. Effects of a combined treatment regime using continuous wave, ultrasound (1 MHz unfocused, without MRI) on day 9 and MRI on day 12 were also investigated. Fetal data were taken on day 18 of gestation. Data from adult animals that were exposed in utero were taken on day 50 postpartum.
animals were treated in seven groups: i) sham ii) MRI exposure on day 9 of gestation iii) MRI exposure on day 12 of gestation iv) MRI exposure on day 9 and day 12 of gestation v) ultrasound exposure on day 9 and MRI exposure on day 12 vi) sham exposure on day 9 and MRI exposure on day 12 vii) ultrasound exposure on day 9 and sham exposure on day 12
| Modulation type | pulsed |
|---|---|
| Pulse width | 5 ms |
| Additional information |
Spin echo sequence with standard characteristics (TR/TE 2000/30 ms) was applied. |
| ばく露の発生源／構造 |
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|---|---|
| ばく露装置の詳細 | animals in cylindrical plastic exposure chambers (14 cm in diameter, 20 cm long) which were placed inside the imaging coil; coil positioned at the center of the superconducting magnet |
| Sham exposure | A sham exposure was conducted. |
| 周波数 | 1 MHz |
|---|---|
| タイプ |
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| ばく露時間 | 30 s |
| Modulation type | CW |
|---|
| ばく露の発生源／構造 |
|
|---|---|
| Sham exposure | A sham exposure was conducted. |
| 測定量 | 値 | 種別 | Method | Mass | 備考 |
|---|---|---|---|---|---|
| 電力密度 | 5 W/cm² | - | - | - | - |
Significant differences in biological endpoints following in utero exposure to complex MRI field conditions were revealed.
Fetal weights of the irradiated groups ranged from 11% (day 9 MRI) to 17% (day 9 ultrasound, day 12 MRI) lower than those of the cage control and sham-exposed fetuses. Crown-rump length of exposed animals was reduced by 8%. The postpartum death rate increased significantly and was as high as 38% following MRI exposure on day 9 and day 12 of gestation. Daily sperm production was reduced by 44% in adults exposed to MRI on day 12 of gestation. A reduction in testis weight and volume in the adult males was also found, but the difference was not statistically significant.
No effect was revealed on embryonic deaths, sex ratio, body weight at day 50, spleen weight, or seminal vesicle weight.
The data show that in utero exposure of mice to high field, long duration MRI conditions alone or in combination with ultrasound exposure reduces fetal growth, neonatal survival, and male reproductive development when it occurs during sensitive times of the developmental cycle (day 9 and/or day 12), and that some of these effects are permanent.
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