Study type: Medical/biological study (experimental study)

Effects of in utero exposure to 4.7 T MR imaging conditions on fetal growth and testicular development in the mouse. med./bio.

Published in: Magn Reson Imaging 1996; 14 (3): 263-274

Aim of study (acc. to author)

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.

Background/further details

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.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 200 MHz
Modulation type: pulsed
Exposure duration: continuous for 8 h on day 9 and/or day 12 of gestation
Exposure 2: 1 MHz
Modulation type: CW
Exposure duration: 30 s

General information

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

Exposure 1

Main characteristics
Frequency 200 MHz
Type
Exposure duration continuous for 8 h on day 9 and/or day 12 of gestation
Additional info 200 MHz RF field + Gradient DC field. Reference article: P.Mansfield, P.G Morris. NMR imaging in biomedicine. New York: Academic Press; 1982: pp. 297-332.
Modulation
Modulation type pulsed
Pulse width 5 ms
Additional info

Spin echo sequence with standard characteristics (TR/TE 2000/30 ms) was applied.

Exposure setup
Exposure source
  • SISCO 4.7 T/33 cm bore imaging spectrometer
Setup 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.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 4.7 T - - - -
SAR 1.5 mW/kg spatial average calculated whole body -

Exposure 2

Main characteristics
Frequency 1 MHz
Type
Exposure duration 30 s
Modulation
Modulation type CW
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power density 5 W/cm² - - - -

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

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.

Study character:

Study funded by