医学影像显示系统亮度特性的评价分析

Assessment of Luminance Characteristic for Medical Imaging Display Systems

目的通过对医学影像用显示器亮度特性的评价,了解显示器的质量现状,为显示器的稳定性质量检测和环境照度的控制提供客观依据。方法按照使用类别选择30台显示器,利用标准图像、亮度计进行客观指标测试,包括亮度综合特性、最大亮度、亮度比、亮度均匀性、亮度响应曲线、环境光照度对亮度响应的影响。选择31名具有五年以上工作经验的医师,每位分别在4种典型的环境亮度下完成阅片工作,通过主观测试选择最舒适的环境照度。结果符合"优秀"级别的显示器占26.7%,符合"良好"级别的显示器占43.4%。不同类别的显示器在综合测试中的表现没有显著性差异(P=0.0706);亮度响应偏差存在显著差异(P=0.049)。显示器的最大亮度与使用时间与存在显著性差异(P=0.01),不同照度等级的环境光对显示器的亮度响应有显著性影响(P<0.0001)。在环境照度为24 lux时,59.01%的测试者认为最舒适(95%CI为71.45%~45.68%)。结论造成显示器亮度特性不合格的主要原因是灰阶分辨能力不足和亮度响应曲线不符合DICOM标准。环境照度影响着显示器的亮度响应误差以及阅片舒适度。选择适合的工作环境照度,并在该照度下对显示器亮度特性进行校准,应作为显示器日常质控的重要内容。

Objective To provide an objective basis for the stability of quality control and environmental illumination control by evaluating luminance characteristic for medical imaging display systems and learning the quality condition of monitors. Methods A total of 30 monitors were selected according to the use category, and objective index test which including the effect of comprehensive luminance characteristics, maximum brightness, brightness ratio, uniformity of luminance, luminance response curve, and environmental brightness to luminance response was perform ed by using the standard image and brightness meter. Thirtyone physicians who had more than fi ve years experience were selected to conduct the research. Each physician fi nished radiograph reading under 4 typical environment luminance to choose the most comfortable environmental luminance. Results The excellent level of monitor accounted about 26.7%, the fine level of monitor accounted about 43.4%. There was no significant difference between different levels of monitor in the comprehensive test（P=0.0706）. But there was a signifi cant difference between the bias of luminance response（P=0.049） and there was signifi cant differences between the maximum brightness and service time（P=0.01）. The ambient light could affect the luminance response of non-corrected monitor（single factor analysis of variance, P〈0.0001）. On the condition that the ambient illumination was 24 lux, 59.01%（95%CI 71.45%~45.68%）of testers though it was the most comfortable. Conclusion The reasons for disqualification of display brightness characteristics are insufficient gray-scale resolution and the intensity transfer function doesn’t meet the standards. The environment illumination can affect luminance response of monitor and the comfort degree of radiograph reading. It is the important part of monitor quality control that choosing the proper working environment illumination and adjusting the light characteristic of monitor under this environment illumination.