Abstract
PurposeIn the beam penumbra of stereotactic body radiotherapy volumes, dose rate effects in implantable cardioverter–defibrillators (ICDs) may be the predominant cause for failures in the absence of neutron-generating photon energies. We investigate such dose rate effects in ICDs and provide evidence for safe use of lung tumor stereotactic radioablation with flattening filter free (FFF) and flattened 6 Megavolt (MV) beams in ICD-bearing patients.MethodsSixty-two ICDs were subjected to scatter radiation in 1.0, 2.5, and 7.0 cm distance to 100 Gy within a 5 × 5 cm2 radiation field. Radiation was applied with 6 MV FFF beams (constant dose rate of 1400 cGy/min) and flattened (FLAT) 6 MV beams (430 cGy/min). Local dose rates (LDR) at the position of all ICDs were measured. All ICDs were monitored continuously.ResultsWith 6 MV FFF beams, ICD errors occurred at distances of 1.0 cm (LDR 46.8 cGy/min; maximum ICD dose 3.4 Gy) and 2.5 cm (LDR 15.6 cGy/min; 1.1 Gy). With 6 MV FLAT beams, ICD errors occurred only at 1 cm distance (LDR 16.8 cGy/min; 3.9 Gy). No errors occurred at an LDR below 7 cGy/min, translating to a safe distance of 2.5 cm (1.5 Gy) in flattened and 7 cm (0.4 Gy) in 6 MV FFF beams.ConclusionA LDR in ICDs larger than 7 cGy/min may cause ICD malfunction. At identical LDR, differences between 6 MV FFF and 6 MV FLAT beams do not yield different rates of malfunction. The dominant reason for ICD failures could be the LDR and not the total dose to the ICD. For most stereotactic treatments, it is recommended to generate a planning risk volume around the ICD in which LDR larger than 7 cGy/min are avoided.
Highlights
Considering stereotactic body radiotherapy (SBRT) and its effects on implantable cardioverter–defibrillators (ICDs), evidence is limited to case reports and mechanistic studiesDepartment of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Theodor-Kutzer-Ufer 1–3, 68167 Mannheim, GermanyI
We presented an investigation of radiationinduced effects on cardiac implantable electronic devices (CIEDs), which showed that volumetric modulated arc therapy (VMAT) without a flattening filter at 6 Megavolt (MV) with typical dose rates at the isocenter may be safely applied even at a distance (2.5 cm) close to the devices ( ICDs) [1]
The following is a description of noticed ICD failures with local ICD doses and accumulated radiation doses within the isocenter at the time of malfunction
Summary
I. Medizinische Klinik, University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany. Partner Site Heidelberg/Mannheim, German Center for Cardiovascular Research (DZHK), Mannheim, Germany which describe such phenomena but fail to identify causes aside from neutron-generating photon energies. We presented an investigation of radiationinduced effects on cardiac implantable electronic devices (CIEDs), which showed that volumetric modulated arc therapy (VMAT) without a flattening filter (flattening filter free; FFF) at 6 Megavolt (MV) with typical dose rates at the isocenter may be safely applied even at a distance (2.5 cm) close to the devices ( ICDs) [1]. The emphasis was on clinical scenarios like normo- or slightly hypofractionated treatments of mediastinal and pelvic tumors (esophageal or central lung cancer and prostate carcinoma) and discrimination of CIED effects between neutron-generating and non-neutron-generating photon beams (6 MV vs 10 MV and 18 MV).
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