Levin Emma A, Morgan Ruth M, Griffin Lewis D, Jones Vivienne J
Centre for the Forensic Sciences, University College London, 35 Tavistock Square, London, WC1H 9EZ, U.K.
Department of Security and Crime Science, University College London, 35 Tavistock Square, London, WC1H 9EZ, U.K.
J Forensic Sci. 2019 Mar;64(2):431-442. doi: 10.1111/1556-4029.13938. Epub 2018 Oct 25.
Image segmentation is a fundamental precursor to quantitative image analysis. At present, no standardised methodology exists for segmenting images of fluorescent proxies for trace evidence. Experiments evaluated (i) whether manual segmentation is reproducible within and between examiners (with three participants repeatedly tracing three images) (ii) whether manually defining a threshold level offers accurate and reproducible results (with 20 examiners segmenting 10 images), and (iii) whether a global thresholding algorithm might perform with similar accuracy, while offering improved reproducibility and efficiency (16 algorithms tested). Statistically significant differences were seen between examiners' traced outputs. Manually thresholding produced good accuracy on average (within ±1% of the expected values), but poor reproducibility (with multiple outliers). Three algorithms (Yen, MaxEntropy, and RenyiEntropy) offered similar accuracy, with improved reproducibility and efficiency. Together, these findings suggest that appropriate algorithms could perform thresholding tasks as part of a robust workflow for reconstruction studies employing fluorescent proxies for trace evidence.
图像分割是定量图像分析的基本前提。目前，对于痕量证据荧光代理图像的分割不存在标准化方法。实验评估了：（i）手动分割在检查人员内部和之间是否可重复（三名参与者重复描绘三张图像）；（ii）手动定义阈值水平是否能提供准确且可重复的结果（20名检查人员分割10张图像）；以及（iii）全局阈值算法是否能以相似的准确性执行，同时提高可重复性和效率（测试了16种算法）。在检查人员的描绘输出之间观察到具有统计学意义的差异。手动阈值处理平均产生了良好的准确性（在预期值的±1%范围内），但可重复性较差（有多个异常值）。三种算法（Yen、最大熵和Renyi熵）提供了相似的准确性，同时提高了可重复性和效率。总之，这些发现表明，合适的算法可以作为使用痕量证据荧光代理的重建研究稳健工作流程的一部分来执行阈值处理任务。
