Gossman Michael S, Nagra Bipinpreet, Graves-Calhoun Alison, Wilkinson Jeffrey
Tri-State Regional Cancer Center, Medical Physics Section, Ashland, Kentucky 41101, USA.
Med Dosim. 2011 Winter;36(4):358-64. doi: 10.1016/j.meddos.2010.09.003. Epub 2011 Mar 5.
The medical community is advocating for progressive improvement in the design of implantable cardioverter-defibrillators and implantable pacemakers to accommodate elevations in dose limitation criteria. With advancement already made for magnetic resonance imaging compatibility in some, a greater need is present to inform the radiation oncologist and medical physicist regarding treatment planning beam profile changes when such devices are in the field of a therapeutic radiation beam. Treatment plan modeling was conducted to simulate effects induced by Medtronic, Inc.-manufactured devices on therapeutic radiation beams. As a continuation of grant-supported research, we show that radial and transverse open beam profiles of a medical accelerator were altered when compared with profiles resulting when implantable pacemakers and cardioverter-defibrillators are placed directly in the beam. Results are markedly different between the 2 devices in the axial plane and the sagittal planes. Vast differences are also presented for the therapeutic beams at 6-MV and 18-MV x-ray energies. Maximum changes in percentage depth dose are observed for the implantable cardioverter-defibrillator as 9.3% at 6 MV and 10.1% at 18 MV, with worst distance to agreement of isodose lines at 2.3 cm and 1.3 cm, respectively. For the implantable pacemaker, the maximum changes in percentage depth dose were observed as 10.7% at 6 MV and 6.9% at 18 MV, with worst distance to agreement of isodose lines at 2.5 cm and 1.9 cm, respectively. No differences were discernible for the defibrillation leads and the pacing lead.
医学界主张逐步改进植入式心脏复律除颤器和植入式起搏器的设计，以适应剂量限制标准的提高。鉴于一些产品在磁共振成像兼容性方面已经取得进展，当这些设备处于治疗性辐射束范围内时，更需要告知放射肿瘤学家和医学物理学家有关治疗计划射束轮廓的变化。进行了治疗计划建模，以模拟美敦力公司生产的设备对治疗性辐射束产生的影响。作为资助研究的延续，我们发现，与将植入式起搏器和心脏复律除颤器直接置于射束中所产生的轮廓相比，医用加速器的径向和横向开放射束轮廓发生了改变。两种设备在轴向平面和矢状平面上的结果明显不同。在6兆伏和18兆伏X射线能量下的治疗射束也存在巨大差异。植入式心脏复律除颤器的百分深度剂量最大变化在6兆伏时为9.3%，在18兆伏时为10.1%，等剂量线的最差吻合距离分别为2.3厘米和1.3厘米。对于植入式起搏器，百分深度剂量的最大变化在6兆伏时为10.7%，在18兆伏时为6.9%，等剂量线的最差吻合距离分别为2.5厘米和1.9厘米。除颤导线和起搏导线未发现差异。
