Identify make and model of generator and lead
The make and model of the implanted generator and lead must be identified to allow the MR safety status of the combined system to be determined. Ideally, the referrer will have provided the make and model of the generator and leads in the MRI referral. However, if this is not the case, identification of the generator and lead can be obtained through various other approaches:
- Clinical Portal or Trak
- The NHS GG&C MRI Physics team have access to a database detailing the make and model of SNS implants implanted in NHS GG&C patients (MRI Physics have separate instructions on accessing this database)
- The patient may be aware of the make and model of the pulse generator and lead
- It may be possible to determine the make and model from previous x-rays. Some manufacturers provide guidance on how to identify the pulse generator and lead model from an x-ray within their MRI Guidelines (e.g. Appendix C of InterStim MRI Guidelines, Jan 2020 version)
- If the make and model still cannot be found and there are no previous x-rays then either a new x-ray would be required or a specialist can interrogate the device with a programmer
Identify the MR safety status
Once the make and model of the generator and lead has been identified, the current MR safety guidance from the manufacturer should be checked. The following links will direct you to MRI safety documentation from the main SNS manufacturers:
- Medtronic (e.g. Interstim): www.medtronic.com/mri
- Axonics https://www.axonics.com/hcp/resources/resource-library
- Finetech-Brindley Bladder System (Vocare) Sacral Anterior Root Stimulator https://finetech-medical.co.uk/support/
MR Conditional systems may include restrictions on which coils can be used (e.g. a Transmit/Receive head coil only) or body regions that can be scanned and the device may need to be put into MRI mode before the scan and restored to the pre-scan settings after the scan. If a device specialist will not be attending the scan to set the device to MRI mode, we recommend calling the patient before their appointment to ask them whether they are able to place the device in the appropriate mode and to ensure they bring the programmer with them to their MRI appointment.
If you are unsure of the MRI safety status of an SNS device or require help meeting the conditions, please contact MRI Physics.
MR Unsafe situations
The following examples should be considered MR Unsafe:
- the make and model of both generator and lead could not be identified
- the patient has an abandoned or broken lead in situ
- the generator battery is depleted, meaning it cannot be placed into MRI mode
If considering scanning off-label, please review the potential risks listed here.
Additional background information
Some background information on SNS devices is contained here.