Research Center Pharmaceutical Engineering, Graz University of Technology, Inffeldgasse 21a/II, Graz, Austria.
Eur J Pharm Sci. 2011 Sep 18;44(1-2):142-8. doi: 10.1016/j.ejps.2011.06.017. Epub 2011 Jul 20.
Optical coherence tomography (OCT) is a non-invasive analysis technique allowing fast and high-quality cross-sectional imaging of scattering media. OCT is based on the physical phenomenon of low coherence interferometry and is thus well suited to image layered structures. In this paper, high-speed spectral domain OCT was used for the characterization of pharmaceutical tablet coatings, sampled at different stages of an industrial drum spray coating process, comprising tablets with a coating thickness ranging from uncoated to a target coating thickness of about 70 μm. In addition to the OCT investigation of layer thickness and homogeneity, tablet weight gain and tablet diameters were determined on a single-tablet level. Scanning electron microscopy (SEM) was applied for referencing the coating thickness obtained with OCT. We demonstrated that OCT allows rapid evaluation of coating properties, such as thickness and homogeneity independently from variations of the tablet core. In contrast to indirect methods, deviations observed with OCT can be related directly to the coating properties. Furthermore, for an extended morphological coating characterization, three dimensional images were reconstructed. Pending further developments, the high axial resolution and fast data acquisition rate of OCT has the potential for highly accurate, fast and low-cost coating control during and after manufacturing.
光学相干断层扫描（OCT）是一种非侵入性分析技术，可快速、高质量地对散射介质进行横截面成像。OCT 基于低相干干涉的物理现象，因此非常适合对分层结构进行成像。本文使用高速光谱域 OCT 对制药片剂涂层进行了表征，在工业鼓式喷涂过程的不同阶段对其进行了采样，所采样的片剂涂层厚度从无涂层到目标涂层厚度约 70μm 不等。除了对 OCT 层厚度和均匀性的研究外，还在单片剂水平上确定了片剂的增重和直径。扫描电子显微镜（SEM）用于参考 OCT 获得的涂层厚度。结果表明，OCT 可快速评估涂层性能，如厚度和均匀性，而不受片剂核心变化的影响。与间接方法相比，OCT 观察到的偏差可直接与涂层性能相关联。此外，为了进行扩展的形态涂层表征，还重建了三维图像。在进一步开发的情况下，OCT 具有高轴向分辨率和快速的数据采集速率，有望在制造过程中和制造后实现高度精确、快速和低成本的涂层控制。
