Micro-computed tomography (micro-CT)

How does micro-CT work, and what is it used for?

The term ‘micro’ comes from micro-CT’s micrometer (µm) resolution range, which enables it to render finely refined two-dimensional slices of the object or material. This is done when the scanner collects a series of two-dimensional planar X-ray images as the material rotates at varying angles. These “sliced” planar images are then reconstructed into a three-dimensional projection through transformation by a digital process called back projection.

Micro-CT provides detailed internal information about a wide range of sample types, from semiconductor components to biological specimens and archeological artifacts. The method is usually used to identify phase distribution, grain boundaries, defects, and cracks within a structure.

Micro-computed tomography in materials science

In materials science, micro-CT plays a pivotal role in characterizing the internal structures of various materials. Researchers and engineers use micro-CT to analyze the porosity, void fraction, and distribution of phases within materials like metals, ceramics, and composites. This information is crucial for understanding the mechanical properties and performance of materials in diverse applications, from aerospace to manufacturing.

Micro-CT in the pharmaceutical industry

The pharmaceutical industry leverages micro-CT for pharmaceutical formulation analysis, ensuring the integrity and uniformity of drug delivery systems. It aids in studying tablet porosity, coating thickness, and internal structures of pharmaceutical products. Micro-CT allows researchers to optimize drug formulations and enhance the quality control processes within the pharmaceutical manufacturing pipeline.

Advantages and limitations of micro-CT

Micro-CT presents several advantages that make it a valuable tool in materials science. A key advantage is its non-destructive or non-invasive imaging capability, allowing researchers to examine the internal structures of materials without altering or interfering with their integrity and overall composition.

In comparison to other imaging methods, like scanning electron microscopy (SEM), another advantage of micro-CT is that it can provide a clear image inside a solid structure, providing unique and complementary information to enable analytical and comprehensive characterization of solid materials. Another advantage is that it offers high resolution, providing detailed insights into microstructures and enabling three-dimensional projection visualization.

A notable drawback is the limited sampling size micro-CT provides because it restricts the potential analysis of larger objects or specimens. Sampling size as a limiting factor is made more substantial when coupled with the introduction of beam hardening artifacts. These artifacts may affect the accuracy of the two-dimensional images. Due to this, micro-CT may not be suitable for all sample types and sizes.

Micro-CT vs nano-CT

A notable distinction with micro-CT is the enhanced resolution nano-CT offers. The refined difference in resolution makes nano-CT suitable for applications requiring extremely detailed imaging, such as nanomaterial characterization.