Gagel Bernd, Schramm Oliver, Harms Wolfgang, Mulhern Andrew, Wenz Frederik, van Kampen Michael, Wannenmacher Michael, Eble Michael J
Department of Radiotherapy, RWTH Aachen, Germany.
Strahlenther Onkol. 2002 Aug;178(8):446-52. doi: 10.1007/s00066-002-0964-1.
The aim of this study was the validation of the visual image quality of electronic portal imaging devices (EPID) and conventional verification films from the point of view of the end-viewers of portal films, the radiotherapists.
The verification image was represented in two different forms, viz. an electronic portal image employing Siemens Beamview Plus (on a computer monitor) and two different portal films using the conventional verification films CEA-TVS and DuPont CQL-7 (on a negatoscope). A total of 270 image sets (simulation film and portal image) were evaluated by each radiotherapist, evaluation extending to 90 sets of each type of verification film. Each set was evaluated by three specialists in radiotherapy examining subjective visual image quality whereby the following aspects served as evaluation criteria: contrast, artifacts, determination of actual radiation field edge position, anatomical structures and main structural feature for the determination of treatment field position. In addition, the anatomical structures employed for visual feature correlation between reference and portal films were classified according to their importance.
In general the electronic portal image was rated significantly "visible" or better. Only the evaluation of artifacts showed an appreciable disadvantage for electronic portal imaging caused by physical artifacts due to radiographic technique and data processing aspects peculiar to the Siemens Beamview Plus 1.1. and also caused by different image processing tools reducing physical artifacts and enhancing the visibility of anatomical structures and likewise of anatomical artifacts (e.g. intestinal gas). By calculating the Spearman correlation coefficient to detect a possible relationship between the different criteria of subjective visual image quality, the research demonstrated that artifacts when limited to a tolerable proportion had no significant impact on the other criteria.
As data of EPIDS are digital, images can be postprocessed and enhanced in a wide variety of ways. Using this tool the electronic portal imaging device provides images that, in terms of visual image quality, are at least comparable to the two evaluated types of radiographic films and also have the added advantage that such images are stored and can be transferred electronically being presupposition for digital patient documentation.
本研究旨在从射野影像的终端观察者即放射治疗师的角度，验证电子射野影像装置（EPID）和传统验证片的视觉图像质量。
验证图像以两种不同形式呈现，即使用西门子Beamview Plus的电子射野图像（在计算机显示器上），以及使用传统验证片CEA - TVS和杜邦CQL - 7的两种不同射野片（在观片灯上）。每位放射治疗师共评估270组图像（模拟片和射野图像），每种验证片类型评估90组。每组由三位放射治疗专家评估主观视觉图像质量，以下方面作为评估标准：对比度、伪影、实际辐射野边缘位置的确定、解剖结构以及用于确定治疗野位置的主要结构特征。此外，根据其重要性对用于参考片和射野片之间视觉特征关联的解剖结构进行分类。
总体而言，电子射野图像的评级显著为“可见”或更好。仅伪影评估显示，由于西门子Beamview Plus 1.1特有的放射技术和数据处理方面的物理伪影，以及不同图像处理工具减少物理伪影并增强解剖结构和解剖伪影（如肠气）的可见性，电子射野成像存在明显劣势。通过计算斯皮尔曼相关系数以检测主观视觉图像质量不同标准之间的可能关系，研究表明，当伪影限制在可容忍比例时，对其他标准没有显著影响。
由于EPIDS的数据是数字的，图像可以通过多种方式进行后处理和增强。利用此工具，电子射野成像装置提供的图像在视觉图像质量方面至少与两种评估的放射胶片类型相当，并且还具有额外优势，即此类图像可存储并能以电子方式传输，这是数字患者文档的前提条件。
