MicroCT Facility (MCT) X-Ray Computed Microtomography X-Ray Micro-Computed Tomography

About MicroCT

Jump To: Overview of microCT | Essentials of microCT |Advantages of microCT | Challenges of microCT

Overview of microCT

X-ray micro-computed tomography (or microCT) is a non-destructive technique that is useful for visualizing and measuring the 3D geometries of internal structures in opaque materials. The technique uses similar technology to that of a medical CT which one would get to identify diseases or injuries inside the body before treatment or surgery. The main difference in the two approaches is the scale at which things are being imaged. As the name would imply, microCT can resolve structures on the micrometer scale.

Cross-section of a scanned sandstone with corresponding pore network model
An example of what can be done with microCT. Left: a cross-section of a microCT image of a Berea sandstone. Right: a 3D pore network model of the sandstone generated from the microCT image.

Essentials of MicroCT

Overview of the main parts of a microCT system

Parts of a MicroCT

Brief introduction on how X-rays interact with matter and how that is useful to microCT

Interaction of X-Rays with Matter

General outline of how a microCT image is generated

Generating an Image

Advantages of microCT

  • Nondestructive: one of the biggest selling points for microCT is the ability to image internal structures without having to section the sample. This is important for many samples where the act of sectioning may degrade the integrity of the internal structures being measured, especially for brittle samples. Another consideration is if the sample simply needs to be preserved because it is a collection piece or further experimentation on the sample is required.
  • Ease of use: samples often require little to no sample preparation to begin scanning. Some exceptions to this include in-situ experimentation and low contrast samples that need contrast agent introduction.
  • In-situ experimentation: because microCT is nondestructive, physical changes in the samples can be studied with respect to time. These changes can happen in-situ or ex-situ to the CT system depending on the needs of the experiment. Some examples of in-situ experimentation include compression/tensile testing and fluid flow in porous media.
  • Wide variety of samples: microCT can be used to investigate a wide variety of samples including (but not limited to) biological matter, bone, rock, ceramic, and electronic devices.
A 3D rendering of a flower imaged using microCT
Biological materials such as flowers can be imaged.
3D rendering of a volcanic rock, reticulite.
Extremely brittle samples such as reticulite, a highly porous volcanic rock, can be scanned safely.
Full and cross-sectioned 3D renders of the toy sample
Engineered materials (e.g. plastics, composites, some metals) can be imaged for a variety of characterizations such as identifying defects or generating surface files for 3D printing.

Challenges of microCT:

  • High/Low-Z materials: the contrast in microCT images is dependent on the atomic number (Z) of the sample. The internal structure of samples with low-Z components can be hard to measure because the difference in X-ray attenuation between these materials may often be less than the noise inherent to the technique. Also, samples with very high-Z components can introduce major image artifacts because they attenuate too much of the X-rays to get a fully exposed image. Some considerations for sample composition can be taken to mitigate these difficulties.
  • Sample size dependent resolution: sample diameter is often a limiting factor for the highest resolution that can be achieved for a particular sample. The highest advertised resolution is often only applicable to very small sample sizes. Larger samples usually have to sacrifice resolution for high fidelity scans. This correlation is discussed further in the sample diameter section of scanning preparation.
  • Data size/Acquisition time: the file sizes and acquisition times for some samples can be very large. Scan sizes can be anywhere from a ~1-100 GB of data and scan times can be anywhere from 10 minutes to over 8 hours. These values are highly dependent on various factors including the size and composition of the sample and the resolution of the image.