Giantsoudi Drosoula, De Man Bruno, Verburg Joost, Trofimov Alexei, Jin Yannan, Wang Ge, Gjesteby Lars, Paganetti Harald
Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States of America.
Phys Med Biol. 2017 Apr 21;62(8):R49-R80. doi: 10.1088/1361-6560/aa5293. Epub 2017 Mar 21.
A significant and increasing number of patients receiving radiation therapy present with metal objects close to, or even within, the treatment area, resulting in artifacts in computed tomography (CT) imaging, which is the most commonly used imaging method for treatment planning in radiation therapy. In the presence of metal implants, such as dental fillings in treatment of head-and-neck tumors, spinal stabilization implants in spinal or paraspinal treatment or hip replacements in prostate cancer treatments, the extreme photon absorption by the metal object leads to prominent image artifacts. Although current CT scanners include a series of correction steps for beam hardening, scattered radiation and noisy measurements, when metal implants exist within or close to the treatment area, these corrections do not suffice. CT metal artifacts affect negatively the treatment planning of radiation therapy either by causing difficulties to delineate the target volume or by reducing the dose calculation accuracy. Various metal artifact reduction (MAR) methods have been explored in terms of improvement of organ delineation and dose calculation in radiation therapy treatment planning, depending on the type of radiation treatment and location of the metal implant and treatment site. Including a brief description of the available CT MAR methods that have been applied in radiation therapy, this article attempts to provide a comprehensive review on the dosimetric effect of the presence of CT metal artifacts in treatment planning, as reported in the literature, and the potential improvement suggested by different MAR approaches. The impact of artifacts on the treatment planning and delivery accuracy is discussed in the context of different modalities, such as photon external beam, brachytherapy and particle therapy, as well as by type and location of metal implants.
越来越多接受放射治疗的患者在治疗区域附近甚至内部存在金属物体，这在计算机断层扫描（CT）成像中会产生伪影，而CT成像是放射治疗中最常用的治疗计划成像方法。在存在金属植入物的情况下，例如头颈部肿瘤治疗中的牙科填充物、脊柱或脊柱旁治疗中的脊柱稳定植入物或前列腺癌治疗中的髋关节置换物，金属物体对光子的极端吸收会导致明显的图像伪影。尽管当前的CT扫描仪包括一系列针对束硬化、散射辐射和噪声测量的校正步骤，但当治疗区域内或附近存在金属植入物时，这些校正并不足够。CT金属伪影会对放射治疗的治疗计划产生负面影响，要么导致难以勾勒靶区体积，要么降低剂量计算精度。根据放射治疗的类型、金属植入物的位置和治疗部位，人们探索了各种减少金属伪影（MAR）的方法，以改善放射治疗治疗计划中的器官勾勒和剂量计算。本文简要介绍了已应用于放射治疗的CT MAR方法，试图对文献中报道的CT金属伪影在治疗计划中的剂量学效应以及不同MAR方法提出的潜在改进进行全面综述。在不同的治疗方式（如光子外照射、近距离放射治疗和粒子治疗）以及金属植入物的类型和位置的背景下，讨论了伪影对治疗计划和交付准确性的影响。
