Tri-State Regional Cancer Center, Medical Physics Section, Ashland, Kentucky 41101, USA.
J Appl Clin Med Phys. 2009 Dec 23;11(1):3115. doi: 10.1120/jacmp.v11i1.3115.
Recent improvements to the functionality and stability of implantable pacemakers and cardioverter-defibrillators involve changes that include efficient battery power consumption and radiation hardened electrical circuits. Manufacturers have also pursued MRI-compatibility for these devices. While such newer models of pacemakers and cardioverter-defibrillators are similar in construction to previously marketed devices - even for the recent MRI-compatible designs currently in clinical trials - there is increased interest now with regard to radiation therapy dose effects when a device is near or directly in the field of radiation. Specifically, the limitation on dose to the device from therapeutic radiation beams is being investigated for a possible elevation in limiting dose above 200 cGy. We present here the first-ever study that evaluates dosimetric effects from implantable pacemakers and implantable cardioverter-defibrillators in high energy X-ray beams from a medical accelerator. Treatment plan simulations were analyzed for four different pacemakers and five different implantable cardioverter-defibrillators and intercompared with direct measurements from a miniature ionization chamber in water. All defibrillators exhibited the same results and all pacemakers were seen to display the same consequences, within only a +/- 1.8% deviation for all X-ray energies studied. Attenuation, backscatter, and lateral scatter were determined to be -13.4%, 2.1% and 1.5% at 6 MV, and -6.1%, 3.1% and 5.1% at 18 MV for the defibrillator group. For the pacemaker group, this research showed results of -15.9%, 2.8% and 2.5% at 6 MV, and -9.4%, 3.4% and 5.7% at 18 MV, respectively. Limited results were discovered from scattering processes through computer modeling. Strong verification from measurements was concluded with respect to simulating attenuation characteristics. For IP and ICD leads, measured dose changes were less than 4%, existing as attenuation processes only, and invariant with regard to X-ray energy.
最近，植入式心脏起搏器和除颤器的功能和稳定性得到了改善，涉及到包括高效电池功耗和辐射硬化电路在内的变化。制造商还追求这些设备的磁共振兼容性。虽然这些新型心脏起搏器和除颤器在结构上与以前市场上的设备相似 - 即使是最近正在临床试验中的磁共振兼容设计也是如此 - 但现在人们对设备靠近或直接处于辐射场时的辐射治疗剂量效应越来越感兴趣。具体来说，正在研究治疗辐射束对设备的限制剂量，以可能将限制剂量提高到 200cGy 以上。我们在这里首次展示了一项研究，评估了来自医用加速器高能 X 射线的植入式心脏起搏器和植入式除颤器的剂量学效应。对四个不同的心脏起搏器和五个不同的植入式除颤器进行了治疗计划模拟，并与水中小型电离室的直接测量结果进行了比较。所有除颤器都表现出相同的结果，所有心脏起搏器都表现出相同的结果，所有 X 射线能量研究的偏差仅在 +/-1.8% 以内。在 6MV 时，对于除颤器组，衰减、背散射和侧向散射分别为-13.4%、2.1%和 1.5%，在 18MV 时为-6.1%、3.1%和 5.1%。对于起搏器组，这项研究显示在 6MV 时的结果为-15.9%、2.8%和 2.5%，在 18MV 时为-9.4%、3.4%和 5.7%。通过计算机建模发现散射过程的结果有限。通过测量得出了关于模拟衰减特性的强烈验证。对于 IP 和 ICD 引线，测量的剂量变化小于 4%，仅存在衰减过程，并且与 X 射线能量无关。
