Department of Radiology, Aichi Medical University Hospital, 1-1 Yazakokarimata, Nagakute, Aichi 480-1195 Japan.
Department of Radiation Oncology, Aichi Cancer Center, 1-1 Kanokoden, Chikusa-Ku, Nagoya, Aichi 464-8681 Japan.
J Radiat Res. 2021 Jul 10;62(4):735-739. doi: 10.1093/jrr/rrab041.
Cumulative dose effects, which are one of the main causes of errors that occur when an implantable cardiac pacemaker (ICP) is irradiated with ionizing radiation, induce permanent failure in ICPs. Although flattening filter free (FFF) beams, which are often used in stereotactic radiotherapy, are known to have different characteristics from conventional (with flattening filter [WFF]) beams, the cumulative dose effects on ICPs with FFF beams have been under-investigated. This study investigates ICP failure induced by cumulative dose effects of FFF beams. When the ICP placed in the center of the irradiation field was irradiated with 10 MV-FFF at 24 Gy/min, the cumulative dose at which failure occurred was evaluated on the basis of the failure criteria associated with high cumulative dose as described in the American Association of Physicists in Medicine Task Group 203. The ICP failures such as a mild battery depletion at a cumulative dose of 10 Gy, pacing-output voltage change >25% at a cumulative dose of 122 Gy, and the loss of telemetry capability at cumulative dose 134 Gy were induced by cumulative dose effects. The cumulative doses by which the cumulative dose effects of FFF beams induced ICP failure were not very different from those reported in previous studies with WFF beams. Therefore, radiotherapy with FFF beams (and WFF beams) for patients with ICP requires appropriate management for minimizing the cumulative dose effects.
累积剂量效应是植入式心脏起搏器 (ICP) 被电离辐射照射时发生错误的主要原因之一，它会导致 ICP 永久性失效。虽然立体定向放射治疗中常用的不带平坦滤过器 (FFF) 的射线，与传统的带平坦滤过器 (WFF) 的射线相比具有不同的特性，但对于 FFF 射线对 ICP 的累积剂量效应的研究还不够充分。本研究探讨了 FFF 射线累积剂量效应对 ICP 的影响。当将置于照射野中心的 ICP 用 10 MV-FFF 以 24 Gy/min 的剂量率照射时，根据美国医学物理学家协会工作组 203 中描述的与高累积剂量相关的失效标准，评估了发生失效时的累积剂量。在累积剂量为 10 Gy 时，会出现轻微电池损耗；在累积剂量为 122 Gy 时，起搏输出电压变化 >25%；在累积剂量为 134 Gy 时，会出现遥测能力丧失等 ICP 失效。由 FFF 射线累积剂量效应引起的 ICP 失效的累积剂量与之前用 WFF 射线进行的研究报告的累积剂量没有很大差异。因此，对于植入 ICP 的患者进行 FFF 射线（和 WFF 射线）放射治疗时，需要进行适当的管理以最大程度地减少累积剂量效应。
