Smith Rachel Weston, Evans Tony, Wolstenhulme Stephen
Department of Medical Physics, University of Leeds, Leeds, UK.
School of Healthcare, University of Leeds, Leeds, UK.
Ultrasound. 2014 May;22(2):80-90. doi: 10.1177/1742271X13513980. Epub 2013 Dec 13.
The aim of this feasibility study was to assess the impact that image processing of abdominal aortic ultrasound (US) images had on the intra-observer reliability of the diameter measurement. The study compared variability between inner-to-inner (ITI), outer-to-outer (OTO) and outer-to-inner (OTI) wall diameter measurements and their resilience to image processing. Three US images of transverse abdominal aortas were manipulated in 13 different ways using functions from Image J software (National Institutes of Health, Bethesda, MD, USA). Blinded measurements were performed of the aortic diameters from each image; this was repeated for ITI, OTO and OTI. Profiles of each image were produced and sets of rules developed to provide detailed instructions as to where, on the profile, the callipers should be placed to correspond with the actual image. The reliability of the diameter measurements compared to the original diameter measurement was least affected by adjusting the brightness and contrast of the US images (better than ± 1.5 mm). Using the functions 'Sharpen' and 'Find Edges' created the largest difference (up to -5 mm). The ITI measurements had the widest spread of variability, whereas the OTI measurements proved to be the most repeatable and resilient to image processing. This study suggests the precision of the measurements can be kept within satisfactory levels even after image manipulation. It also showed the most reliable measuring guideline was OTI, in contrast to the guideline currently used by the NHS Abdominal Aortic Aneurysm Screening Programme. Further research is needed to transfer the findings into the clinical setting of the National Screening Programme to increase its reliability.
本可行性研究的目的是评估腹主动脉超声（US）图像的图像处理对观察者内直径测量可靠性的影响。该研究比较了内到内（ITI）、外到外（OTO）和外到内（OTI）壁直径测量之间的变异性及其对图像处理的耐受性。使用来自美国国立卫生研究院（位于马里兰州贝塞斯达）的Image J软件的功能，以13种不同方式对三张腹主动脉横向的US图像进行了处理。对每张图像的主动脉直径进行了盲法测量；对ITI、OTO和OTI均重复此操作。生成了每张图像的轮廓，并制定了一套规则，以提供关于在轮廓上何处放置卡尺以与实际图像相对应的详细说明。与原始直径测量相比，直径测量的可靠性受调整US图像亮度和对比度的影响最小（优于±1.5毫米）。使用“锐化”和“查找边缘”功能产生的差异最大（可达-5毫米）。ITI测量的变异性分布最广，而OTI测量被证明是最可重复且对图像处理耐受性最强的。本研究表明，即使在图像处理后，测量精度也可保持在令人满意的水平。研究还表明，与英国国家医疗服务体系（NHS）腹主动脉瘤筛查计划目前使用的指南相比，最可靠的测量指南是OTI。需要进一步开展研究，将这些研究结果应用于国家筛查计划的临床环境，以提高其可靠性。
