Fourier-domain full-field optical coherence tomography using imaging fibre bundles

断层扫描是一个术语，指的是产生三维结构图的成像技术。通常，它指的是医学成像技术，产生人体器官和组织结构的图像，通常是为了定位肿瘤或组织的其他畸形。用于绘制深埋结构地图的层析成像技术包括磁共振成像、正电子发射断层扫描、超声波和x射线，但这些技术都无法分辨尺寸小于100微米（与人类头发的直径大致相同）的细节。光学相干层析成像OCT是一种技术，它允许以比任何其他可用方法更高的分辨率对地下结构进行成像。在最高分辨率的系统中，可以看到直径几微米的单个细胞。OCT使用可见光或红外光，这些光被组织强烈散射，不会深入体内。只能从约2mm深的表层获取信息。虽然这似乎是一个缺点，但使用OCT获得的信息是非常有用的。大多数癌症始于身体的表面或上皮组织。这些包括皮肤和胃肠道的内部表面。通过使用柔性光纤内窥镜，OCT探针可以探测到内部表面和皮肤，这可以检测到预示癌前病变的微小组织变化。目前正在开发的大多数OCT探头使用单个光纤将光传输到测量区域。透镜在组织中实现几微米直径的聚焦。在不同组织类型之间的边界，光被反射回探针，并重新耦合到光纤中，从那里它与参考光束混合在检测器上。如果两束光的路径匹配，并且来自组织的反射很强，探测器就会看到一个大信号。因此，通过扫描参考光束路径长度，组织内的边界被检测为对应于不同深度的信号爆发。如果需要三维信息，则必须在样品表面的许多位置进行测量。这通常是通过用一个小的移动镜快速扫描光束来实现的。然而，很难构建用于体内的扫描系统，因为这些系统必须小型化以适应内窥镜，并且必须将电力输送到内窥镜尖端以驱动扫描仪。我们提出了一种新技术，它使用一种称为相干纤维束的组件。它可以有几米长，由数千根纤维组成，排列成直径几毫米的规则阵列。聚焦在一端的一束光在传输到另一端时没有变化。这允许使用每个单独的纤维作为一个单独的OCT系统，在整个样品表面的阵列位置，用数码相机来查看图像。因为纤维束是非常灵活的，它可以用于内窥镜。机械扫描现在只需要在身体外部的系统部分，降低了探头的复杂性。我们打算研究基于光纤束构建OCT系统的技术。来自光源的光将被用来照亮一排纤维，或者每一根纤维的快速连续，并且使用这两种技术实现的性能将被比较。现有的处理技术可以从整个样本深度中同时提取信息。使用一个广谱源，并用衍射光栅将这个广谱内许多狭窄的、离散的波长带产生的干涉条纹频率分开。另一种方法是，通过在宽光谱范围内快速扫描激光器发出的窄带光，可以及时分离来自每个波长的信息。数学处理提取深度相关的结构数据。

Tomography is a term used to refer to imaging techniques that produce a 3-dimensional map of a structure. Typically, it refers to medical imaging techniques resulting in images of organs and tissue structures within the human body, often with the aim of locating tumours or other malformations of the tissue. Tomographic techniques that produce maps of deeply buried structures include magnetic resonance imaging, positron emission tomography, ultrasound and X-ray, but none of these can resolve detail with dimensions less than about 100 micrometres (roughly the same diameter as a human hair).Optical coherence tomography OCT is a technique that allows sub-surface structure to be imaged with much higher resolution than any of the other available methods. In the highest resolution systems, individual cells, a few micrometres in diameter, can be seen. OCT uses visible or infra-red light, which is strongly scattered by tissue, and does not penetrate far into the body. Information can only be obtained from a surface layer about 2 mm deep. Although this appears initially to be a disadvantage, the information obtained using OCT is extremely useful. A majority of cancers begin in the surface, or epithelial, tissues of the body. These include the skin and internal surfaces of the gastro-intestinal tract. By using flexible optical fibre endoscopes internal surfaces, as well as the skin, are accessible to OCT probes, which can detect minor tissue changes indicative of pre-cancerous conditions.Most OCT probes currently being developed carry light to the measurement region using a single optical fibre. A lens achieves focusing to a diameter of a few micrometres in the tissue. At boundaries between different tissue types, light is reflected back towards the probe, and re-coupled into the optical fibre, from where it mixes on a detector with a reference beam. If the paths travelled by the two beams match, and the reflection from tissue is strong, a large signal is seen by the detector. Thus by scanning the reference beam path length, boundaries within the tissue are detected as signal bursts corresponding to various depths.If 3D information is required, measurements must be made at many positions across the sample surface. This is often achieved by scanning the beam rapidly with a small moving mirror. However, it is difficult to construct scanning systems for use inside the body, as these must be miniaturised to fit inside an endoscope, and electrical power must be delivered to the endoscope tip to drive the scanner. We propose a new technique that uses a component called a coherent fibre bundle. This can be several metres long, comprising many thousand fibres arranged in a regular array a few millimetres in diameter. A pattern of light focused onto one end is transmitted unchanged to the other end. This allows the use of each individual fibre as a separate OCT system at an array of positions across the sample surface, with a digital camera used to view the image. Because the fibre bundle is extremely flexible, it can be used endoscopically. Mechanical scanning is now required only in the part of the system external to the body, reducing the complexity of the probe.We intend to investigate techniques for constructing OCT systems based on optical fibre bundles. Light from the source will be used to illuminate either a row of fibres, or each fibre in rapid succession, and the performance achieved using the two techniques will be compared. Processing techniques exist to extract simultaneous information from the full sample depth. A broad spectrum source is used, and a diffraction grating separates the interference fringe frequencies produced by many narrow, discrete wavelength bands within this broad spectrum. Alternatively, the information from each wavelength can be separated in time, by rapidly sweeping narrowband light from a laser across a broad spectral range. Mathematical processing extracts the depth-dependent structural data.