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9. Pregnancy

9.1  MRI of the pregnant patient

For MR procedures on pregnant women, the safety of both the mother and the developing fetus needs to be carefully considered.  Departments should proceed with caution and scanning should only take place following consideration of the risks and benefits of using MRI including assessing the suitability of alternative imaging modalities.

There are numerous sources of current guidance; please refer to the documents listed in 9.2 for further information.

13695342-exclamation-point.jpg Departments should have in place a clear process for consenting and scanning pregnant patients recorded within the local rules.

Once the decision to scan has been made:

13695342-exclamation-point.jpgMR operators should ensure that, wherever possible, scanning is within the normal operating modes.  Scan parameters should be recorded on the RIS system, in particular scan duration and accumulated SAR.

9.2  Current Guidance

Please refer to the following publications for further information on potential risks and guidance and exposure limits:

International Commission on Non-Ionising Radiation (ICNIRP) Guidelines on Limits of Exposure to Static Magnetic Fields, 2009 5

Amendment to the ICNIRP Statement on Medical Magnetic Resonance (MR) procedures Protection of Patients 2009 6

Health Protection Agency (HPA) Protection of Patients and volunteers undergoing MRI procedures 2008 4

MHRA Guidelines for Magnetic Resonance Equipment in Clinical Use 2

9.3  Decision to scan pregnant patients

The MHRA2 recommends that a decision to scan should be made at the time between the referring clinician, an MRI radiologist and the patient, regarding the risks weighed against the clinical benefit to the patient.  This decision should be recorded in the patient’s notes and on any Hospital Information System (HIS) or Radiology Information System (RIS) used.

Although it is likely that an initial discussion as to whether MRI is the appropriate modality would take place between a referring clinician and radiologist, there are many MRI units operating as standalone/ satellite units often without access to radiologists.  It is within the scope of practice for a suitably trained and experienced MR radiographer to advise patients and referring clinicians on the risks and benefits associated with MRI and to offer advice on the most appropriate imaging exam.

9.3.1   Factors to consider prior to deciding to scan pregnant patients

If your opinion is requested regarding the suitability of MRI on a pregnant patient, consider the following:

  • can the examination be deferred until after delivery? Discuss with the referring clinician their proposed course of treatment/action.
  • can the clinical question be answered using a different method/modality, in particular consider ultrasound.
  • consider the risks associated with other modalities eg CT.  Consider radiation dose.

9.3.2   Consenting the pregnant patient

Departments should have in place a clear process for consenting pregnant patients.  This should include a consent form signed by the patient, the referring clinician and the MR radiologist and/or MR radiographer.

Please also refer to section 17.2   Consent.

9.4  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 advisor 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

9.4.1   Reducing heating effects

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

13695342-exclamation-point.jpg It is essential to ensure patient weight is accurately obtained.

9.4.2   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, larger Field of Views will all reduce the dB/dt and, thus, 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 use.

9.5  Use of gadolinium based contrast agents - pregnant patients

The MHRA 15 has issued advice to healthcare professionals regarding the use of gadolinium based contrast agents (GBCA):  use of any GBCA during pregnancy is not recommended unless absolutely necessary.

9.6  Pregnant staff

Under the Management of Health and Safety at Work Regulations (Regulation 16) 16 employers are obliged to undertake a risk assessment for expectant mothers relating to hazards caused by physical agents.  Further information is available within the SCoR 17 publication, available online:  https://www.sor.org/learning/document-library/health-safety-and-pregnancy-clinical-imaging-and-radiotherapy-departments-guide-pregnant-women  (accessed 28th February 2013)

13695342-exclamation-point.jpgRisk assessments should be conducted for each MR scanner.

9.6.1   Current guidance

Please refer to the documents listed in 9.2 for further information.

Employers should ensure that they comply with the advice issued in Safety Guidelines for Magnetic Resonance Equipment in Clinical Use, MHRA2,  as updated, superseded and replaced from time to time.  Currently the MHRA recommends that

‘each site should undertake a risk assessment analysing staff movement and location in relation to the levels of the magnetic fields and the total length of time that they will be exposed.  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.’

The MHRA recommends that throughout their pregnancy it is advisable that staff do not remain in the scan room while scanning is underway.

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