There are no universal guidelines specifying radiation dose limits to CIEDs. It is widely accepted that, ideally, cumulative dose above 2Gy should be avoided. However, the risk of failure with doses in the 2-10GY range remains relatively low (Hurkmans 2012). If the device is likely to receive a dose >10Gy, then the risk of failure is significant and consideration should be given replanning the treatment to reduce the dose or relocation of the device.r
Typically, CIEDs are routinely checked at regular intervals to ensure that they are functioning correctly. If the device has not been checked in the 3 months prior to treatment, consider a device check prior to radiotherapy. Before an ICD patient undergoes radiotherapy, consideration must be given (in consultation with the patient's cardiologist) to switching the anti-tachycardia therapy off during treatment. This can be achieved by the radiation therapist placing a heavy magnet (90-130 Gauss) over the device or a trained pacemaker technician programming this function off and on at each fraction.
For all medium and high risk patients suitably trained medical staff should be present to monitor the patient during and immediately after each treatment and the "crash cart" should be readily available. If there is any suggestion of a device malfunction, either reported by the patient or from ECG evidence, additional discussion +/-consultation with the patient's cardiologist should be arranged.
||Time period of actions
|Consider relocation of device
||1st day In-vivo dosimetry
||1st day BP and pulse oximetry monitoring
||Daily BP and pulse oximetry monitoring
||Daily ECG monitoring during treatment
||Consider 1st day then weekly device check
||Consider device check after each fraction
BP - Blood pressure, ECG - Electrocardiogram
* Consider relocation of ICD if total dose > 1Gy
All pulse, BP and ECG monitoring should be performed by a suitably qualified health professional.
Post Treatment - All patients should have their cardiac devices checked post completion of radiotherapy treatment.
During radiotherapy simulation, the CIED exposure should be kept to a minimum.
McCullough et al 2007rreported that it is relatively safe for patients with pacemakers and ICDs to undergo computer tomography (CT) scans where the pacemaker or ICD move briefly (approximately < 3 seconds) through the x-ray beam, as in sequential or spiral scanning.
The FDA has provided notifications on recommendations to follow prior to CT scanning to minimise the risk to the patient.
- Ideally the patient has been seen in a cardiology clinic prior to simulation.
- Use CT scout view to determine location of implanted or externally worn electronic devices to the scanning upper and lower limits.
- Ask patients with remote control devices to shut off the device temporarily during scanning.
- Minimise x-ray exposure to the pacemaker or ICD by:
- using the lowest possible x-ray tube current to obtain the image
- ensuring the x-ray beam does not dwell over the device for more than a few seconds. Access additional information from the FDA 2017 report and literature review.
In rare cases various types of implantable devices, such as neurostimulators, drug infusion pumps, including insulin pumps, cochlear implants and retinal implants, may need to be switched off during scanning.
Note: For CT procedures that require scanning over the medical device continuously for more than a few seconds, as with CT perfusion or interventional exams, attending staff should be ready to take emergency measures to treat adverse reactions if they occur.
Magnetic resonance imaging (MRI) has long been documented as a contraindication for patients with cardiac pacemakers and ICDs. Concerns have been related to movement of the generator and/or leads, excessive heating of the leads and changes in the pacing device (including temporary or permanent functional changes) inappropriate sensing or triggering of the device.r
However, the latest generation of devices have features that include decreased ferromagnetic components, more sophisticated circuitry, and improved electromagnetic interference rejection capabilities, which may make these cardiac devices less problematic for MRI.r Discuss with the patients Cardiologist or the device company to determine/verify the CIEDs MRI compatibility. The effects of MRI on pacemakers and ICDs vary and depend on factors including:
- the type of device
- how the device is programmed
- the static magnetic field strength of the MRI system and the conditions used for the procedure (e.g. anatomic region images, the type of RF coil used and the amount of radiofrequency energy applied during imaging)
Recent investigations conducted using in vitro techniques, laboratory animals, and patients demonstrated that certain "modern day" (defined as being manufactured in year 2000 or later) pacemakers and ICDs are not adversely affected by MRI scanning, especially if procedures are performed under highly specific conditions.r
Important note: Prior to any MRI imaging a collaborative discussion between the patient's cardiologist, radiation oncologist and the radiology (MRI) department must be had to determine a patient's suitability and risk of pacemaker/ICD failure.
The management of patients with CIEDs can be divided into 3 stages:
- pre treatment - pre simulation/planning
- during treatment
- post treatment.
At time of initial consult it is important for the radiation oncologist/registrar to identify those patients with CIEDs and ensure that the following information is recorded:
- type of implanted device - pacemaker or ICD
- brand and model number if known by patient
- indicate approximate distance of radiation field from edge of CIED
- date the CIED was implanted (Note: each patient should have a device identification card with this information)
- patients level of dependence on the CIED.
It is important to work closely with the patients cardiologist or CIED technician prior to radiation treatment so a full assessment of the device can be performed if required. A strategy should be developed, specific to each patient for monitoring and verifying appropriate device operation during and following radiation treatment.
If the patient is referred to the cardiologist/electrophysiologist, the following information should be requested:
- confirmation of make and model of device
- date implanted and patient's level of dependence on the device
- recommendations on re-programming the device to a fail safe mode
- recommendation on appropriate levels of observation and monitoring of vital signs during radiotherapy
- consideration of deactivation of the device and steps to perform where required. See Appendix 4 for manufacture advice on magnet use
- surgical relocation where required
- follow up device check at completion of radiation therapy.
The CIED vendor technician's involvement throughout the patient's radiotherapy treatment will vary, and is dependent on the patients risk category. Involvement may range from an initial baseline assessment to daily monitoring of the patient during treatment.
See below for vendor contacts:
Pre treatment - simulation/planning assessment
- refer to recommendations for monitoring table
- consider calling technician to attend planning CT and assess the patients device for high risk patients
- ensure patients pacemaker or ICD device has been checked if required
- perform baseline ECG prior to performing CT scan
- avoid planning MRIs where possible, as MRIs are still a contraindication in the majority of patients
- prior to any MRI imaging a collaborative discussion between the patients cardiologist, radiation oncologist and the radiology (MRI) department must be had to determine a patient's suitability and risk of pacemaker/ICD failure
- perform CT scout scan to determine pacemaker location
- additional planning CT slices close to the level of the pacemaker/ICD during simulation will allow for an estimate cumulative dose to be calculated when the pacemaker is not located within the specified treatment area
- document the estimated cumulative dose the device is to receive
- pacemakers and ICDs should never be in the direct, unshielded radiation beam. Treatment beams should be arranged to minimise exposure where possible
- if it is not possible to avoid the pacemaker/ICD then surgical relocation is recommended.
- refer to Recommendations for Monitoring table
- have a crash trolley on stand by and alert a RT Nurse when patient is to be treated
- avoid electronic portal images (EPI) with open double exposures that include the pacemaker/ICD in the radiation field
- although transient malfunction from electromagnetic interference (EMI) is unlikely from contemporary therapy accelerators and cobalt irradiators, the patient should be closely observed during the first treatment with a linear accelerator and during subsequent treatments if magnetron or klystron misfiring (sparking) occurs.r
Equipment needed for monitoring patient during treatment:
- pulse oximeter machine
- ECG Machine
- crash trolley
- thermoluminescent dosimeters (TLDs) or other invivo dosimeters for day 1 of treatment (if requested)
- refer to recommendations for monitoring table
- record all assessments in patients notes
- recommend cardiology check up following completion of radiation therapy