Cardiac devices audit evaluating the use of 6 MV FFF beams following updated Radiotherapy Board guidance

Following guidance from the Radiotherapy Board for radiotherapy of patients with cardiac implantable electronic devices (CIED), a local audit of retrospective patient treatments was carried out. The guidance includes recommendations to avoid direct irradiation of the devices and the avoidance of Flattening Filter Free (FFF) beams due to the high dose rates associated with FFF beams, leading to higher risk of device malfunction.

Linac dose-rates were measured by noting the dose rate of the linac whilst delivering 6 MV FFF treatment plans, the local standard energy used for Volumetric Modulated Arc Therapy (VMAT). Plans were also assessed to determine whether treatment beams traveled through the CIED.

It was found that 1 out of 540 patients with CIEDs was treated with the CIED receiving a dose rate above 8 Gy/minute for a 6 MV FFF beam. The plan for this treatment did not have the "protect function" for CIEDs, which is now standard planning practice.

The dose rate when using 6 MV FFF beams is sufficiently reduced, and therefore we have confidence in our current practice for the protection of patients with CIEDs.

This technical note responds to recent guidance published on the safety of radiotherapy exposures for patients with cardiac devices. It audits the standard practices in a large NHS Trust, assessing whether these standard practices align with the guidance. This will be of interest to many other trusts aspiring to adhere to this guidance.