光学相干断层成像检验技术

Optical Coherence Tomography: Principles and Applications in Forensic Science

光学相干断层成像技术(optical coherence tomography,OCT)是一种新型的利用生物组织散射光相干原理的光学成像技术,具有无损、断层成像、高分辨率、易小型化等特点。它的原理类似于超声成像,不同之处是它利用的是光,而不是声音。OCT技术最早和最成熟的应用是在医学成像领域,随着技术的进一步发展,它逐渐在非生物医学领域也开始出现相关研究。在法庭科学领域,物证检验技术正朝着低损、快速、高精度的方向发展。光学影像检验技术是最重要的物证检验手段之一,其在物证的快速搜索、发现、提取和分析方面具有独特优势。OCT技术以其三维高分辨断层成像能力,拓展现有的物证检验手段和能力,得到越来越多法庭科学研究者们的关注,显示出广阔的应用前景。本文介绍了OCT技术的概念、原理、技术手段和类别,综述了利用OCT技术进行法庭科学研究的报道,列举了OCT技术在指纹显现增强、假币鉴别、油画鉴定、纹身鉴别、血斑分析、死亡时间推断、枪弹检验等方面的应用。相信其在物证检验实践中将显示出重要的作用。

Optical coherence tomography （OCT）, an imaging system very similar to ultrasound by use of light instead of sound, is an emerging technology for non-invasive, high resolution and cross-sectional imaging based on low-coherence interferometry. In the past, OCT has been widely applied in medical imaging, especially in ophthalmology, cardiology, dermatology and gastrointestinal observation. Yet, its ability to provide three-dimensional tomographic images is also rendering it attractive for applications beyond the medical. In practice, the forensic imaging technology plays an important role in searching, extracting and analyzing the evidence with merits of non-invasiveness, high speed and high precision. Thus OCT, competent to explore the internal features of an object with micro-meter resolution, will greatly expand the scope of current evidence examination technology, showing a broadly applicable prospect. In this review, we will introduce the basic concepts, principles, categories of OCT technology and a detailed introduction of the so far presented OCT-based methods and applications, ranging from fingerprint imaging, counterfeit banknote detection, easel painting examination, tattoo inspection, bloodstain volume determination, post-mortem interval and bullet imaging. Owing to the characteristic of non-invasive and cross-sectional imaging, OCT is able to detect artificial fingerprint, counterfeit banknote, forgery painting and tattoo. Besides, capable of 3D high resolution imaging, OCT can provide promising applications in high quality imaging and quantitative analyzing, including multi-layer tomography extraction, determination of the volume of bloodstain in the crime scene, image obtainment of the human hair with ultrahigh resolution, estimation of the post-mortem interval and non-contact examination of bullets. Furthermore, OCT techniques have many other advantages as an advanced imaging method with high potential for future forensic applications, for example, the use of near infrared light enabling the non-invasive and non-contact imaging of sample to keep the integrality and authenticity of evidence. Meanwhile, the ability to realize 3D high-resolution cross-sectional imaging will reveal more precise information for sample to authenticate and identify. Moreover, OCT, via extracting different properties such as the spectrum, elasticity and polarization, can achieve diversified functional imaging to further improve the image contrast in demonstrating its appropriateness for forensic imaging.