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11. Pregnancy

11.1 MRI of the pregnant patient

For MR procedures on pregnant women, the safety of both the mother and the developing foetus needs to be considered.  There are numerous sources of guidance and readers should refer to the relevant sections of the guidance listed in 11.2

  • The decision to scan should be documented in the patient’s notes and scanning should usually take place in normal mode.

11.1.1 Scanning of the pregnant patient in controlled mode

The MHRA advises ‘If the decision is taken to scan in controlled mode this should be taken following a full risk benefit analysis and made at the time by the referring clinician, consultant radiologist and patient. This decision should be recorded in the patient’s notes and steps should be taken to utilise sequences that minimise RF and acoustic noise’. 2

11.2 Current guidance

ICNIRP Guidelines on Exposure to Static Magnetic Fields 200916
ICNIRP Amendment to the ICNIRP” Statement on Medical Magnetic Resonance (MR) procedures Protection of Patients “200917
PHE Protection of Patients and volunteers undergoing MRI Procedures 2008 15
MHRA Guidelines for Magnetic Resonance Equipment in Clinical Use2

11.3 Pulse sequence selection and parameter manipulation

Manufacturers often provide general guidance in their user manual with more specific advice available from applications support teams. If required, seek advice from your MR safety expert regarding pulse sequence selection and discuss with a radiologist or a suitably qualified radiographer the possibility of utilising a reduced protocol examination.

  • MR operators should utilise low SAR and quiet pulse sequences wherever possible

11.3.1 Reducing heating effects

Gradient echo sequences are generally less RF intensive resulting in less heating effects. Where possible, select low SAR pulse sequences.

  • It is essential to ensure patient weight is accurately obtained.

11.3.2 Reducing acoustic noise levels

Where possible, switch gradients into reduced acoustic noise mode, such as whisper or soft tone. Longer TRs, lower resolution, increased slice width and larger field of views will all reduce the dB/dt and, therefore, the acoustic noise generated. Echo Planar Imaging and other fast acquisition techniques will produce high acoustic noise levels and these should be carefully considered before their use.

11.4 Use of contrast agents in pregnant patients

Use of any Gadolinium Based Contrast Agents (GDCA) during pregnancy is not recommended unless absolutely necessary owing to the possibility of gadolinium accumulation in human tissues.30

11.5  Pregnant staff

Under the Management of Health and Safety at Work Regulations, 31 employers are obliged to undertake a risk assessment for expectant mothers relating to hazards caused by physical agents.  

In general, it is expected that the level of the time-varying electromagnetic fields, dB/dt, and the radio frequency will be relatively low except in the immediate vicinity of the scanning aperture. This may be of concern in the interventional situation. The level of the static magnetic field exposure is dependent on the field strength and shielding incorporated into the design of the magnet.2

Further information available within the SCoR 32 publication, available online:  https://www.sor.org/learning/document-library/health-safety-and-pregnanc...

  • Risk assessments should be conducted for each MR scanner.
  • The MHRA recommends that throughout their pregnancy it is advisable that staff do not remain in the scan room while scanning is underway.2

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