Healy B J, van der Merwe D, Christaki K E, Meghzifene A
International Atomic Energy Agency, Vienna, Austria.
University of the Witwatersrand, Johannesburg, South Africa.
Clin Oncol (R Coll Radiol). 2017 Feb;29(2):110-115. doi: 10.1016/j.clon.2016.11.002. Epub 2016 Nov 28.
Medical linear accelerators (linacs) and cobalt-60 machines are both mature technologies for external beam radiotherapy. A comparison is made between these two technologies in terms of infrastructure and maintenance, dosimetry, shielding requirements, staffing, costs, security, patient throughput and clinical use. Infrastructure and maintenance are more demanding for linacs due to the complex electric componentry. In dosimetry, a higher beam energy, modulated dose rate and smaller focal spot size mean that it is easier to create an optimised treatment with a linac for conformal dose coverage of the tumour while sparing healthy organs at risk. In shielding, the requirements for a concrete bunker are similar for cobalt-60 machines and linacs but extra shielding and protection from neutrons are required for linacs. Staffing levels can be higher for linacs and more staff training is required for linacs. Life cycle costs are higher for linacs, especially multi-energy linacs. Security is more complex for cobalt-60 machines because of the high activity radioactive source. Patient throughput can be affected by source decay for cobalt-60 machines but poor maintenance and breakdowns can severely affect patient throughput for linacs. In clinical use, more complex treatment techniques are easier to achieve with linacs, and the availability of electron beams on high-energy linacs can be useful for certain treatments. In summary, there is no simple answer to the question of the choice of either cobalt-60 machines or linacs for radiotherapy in low- and middle-income countries. In fact a radiotherapy department with a combination of technologies, including orthovoltage X-ray units, may be an option. Local needs, conditions and resources will have to be factored into any decision on technology taking into account the characteristics of both forms of teletherapy, with the primary goal being the sustainability of the radiotherapy service over the useful lifetime of the equipment.
医用直线加速器和钴 - 60治疗机都是用于外照射放疗的成熟技术。本文从基础设施与维护、剂量学、屏蔽要求、人员配备、成本、安全性、患者吞吐量以及临床应用等方面对这两种技术进行了比较。由于电子部件复杂，直线加速器对基础设施和维护的要求更高。在剂量学方面，直线加速器具有更高的束流能量、可调制的剂量率和更小的焦点尺寸，这意味着使用直线加速器更容易创建优化的治疗方案，以实现肿瘤的适形剂量覆盖，同时保护处于危险中的健康器官。在屏蔽方面，钴 - 60治疗机和直线加速器对混凝土掩体的要求相似，但直线加速器需要额外的屏蔽和中子防护。直线加速器的人员配备水平可能更高，并且需要更多的人员培训。直线加速器的生命周期成本更高，尤其是多能量直线加速器。由于钴 - 60治疗机使用高活度放射源，其安全性更为复杂。钴 - 60治疗机的患者吞吐量可能会受到源衰减的影响，但维护不善和故障会严重影响直线加速器的患者吞吐量。在临床应用中，直线加速器更容易实现更复杂的治疗技术，高能直线加速器上的电子束可用性对某些治疗可能很有用。总之，对于低收入和中等收入国家放疗选择钴 - 60治疗机还是直线加速器这个问题，没有简单的答案。事实上，一个结合多种技术（包括正交电压X射线装置）的放疗科可能是一个选择。在考虑这两种远距离治疗形式的特点时，任何技术决策都必须考虑当地需求、条件和资源，主要目标是放疗服务在设备使用寿命期间的可持续性。
