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16 January 2016 Tablets & Capsules How CT works In general terms, a CT system comprises an x-ray tube, a detector, a material handling apparatus, a shielding cham- ber, a work station for image acquisition, and a work station for image reconstruction and data analysis. CT is a nonde- structive evaluation method that doesn't heat the speci- men/product. In operation, it generates x-ray photons that either travel through the product or are attenuated by it. The photons that penetrate the product enter the imaging detector, carrying with them detailed information (Figure 1). The degree of photon attenuation depends on the amount of energy applied and the thickness or density of the material that the photons pass through. When scanning a tablet, for example, the system rotates it 360 degrees, which typically generates hundreds to thousands of images acquired at an equal number of different angles. Next, an algorithm reconstructs a 3D volumetric representation of the product, which you can adjust to optimize 3D visualiza- tion or slice into a number of planes. Other tools enable you to conduct an array of analyses of both single and global voxel data. It's possible, for example, to bring to the fore materials and features based on material density, creating a polygonal mesh surface. That surface, in turn, can be used to visually evaluate specific areas or materials within the product. You can also use it to generate highly accurate metrology data, CAD files, 3D printing files, CAD comparisons, finite ele- ment analyses, and other data sets (Figure 2). Tablet and capsule applications CT capabilities comprise volumetric analysis of individ- ual materials; analysis of particle size, shape, and volume; analysis of API distribution; and assessment of coating thickness and uniformity (Figure 3). These CT-viewable product characteristics carry with them information that can assist you in developing new products and processes, verifying quality, protecting intellectual property, and test- ing performance. Figure 3 Volumetric analysis of materials: assessment of coating thickness and core uniformity b. Core only c. Coating only a. Tablet core and coating Figure 1 During CT scanning, some photons penetrate the product and reach the imaging detector, carrying with them detailed information. Figure 2 CT enables you to visually evaluate specific areas or materials within tablets and capsules.