An X-ray CT system emits X-rays at a specimen or sample to generate non-destructive cross-sectional (2D) and three-dimensional (3D) images. CT stands for computed tomography. X-rays are emitted from 360 or 180 degrees around a sample, and the X-rays that pass through are detected and imaged. The detection data is then processed and reconstructed by a computer to generate images. Based on the acquired data, a cross section of the sample can be displayed from any position, allowing the viewing to verify a three-dimensional image from all angles. In general, there are two kinds of X-ray CT imaging, industrial and medical.

While industrial and medical X-ray CT imaging are based on the same principles, the equipment itself differs significantly. The main differences are as follows.

- As medical X-ray CT systems irradiate the human body with X-rays, they involve radiation exposure. For this reason, there are limits to the X-ray energy and dosage. For industrial uses, since it is not necessary to consider the impact that radiation exposure has on the sample, stronger X-rays can be used.
- It is necessary to irradiate the test subject through 360 degrees, and with medical X-ray CT systems, it is not possible to rotate the human body (patient), so the equipment rotates instead. With industrial X-ray CT systems, however, generally the sample is rotated.
- As a medical X-ray CT system needs to observe the presence or absence of tumors, it is more concerned with contrast resolution than spatial resolution. With an industrial X-ray CT system, spatial resolution is emphasized due to the need to observe minute defects.
- A medical X-ray CT system also features a fast imaging speed in order to reduce the patient's exposure to radiation. With industrial X-ray CT systems, since the focus is on image quality, imaging takes longer.
- With industrial X-ray CT systems, the sample size varies greatly, from a coin-sized sample to large components such as automotive engines. In addition, the sample material and required resolution also differ significantly. For this reason, there are many types of industrial CT systems, such as microfocus CT systems and the high-energy CT systems supplied by Hitachi High-Tech.

The use of X-ray CT scanning makes it possible to non-destructively observe the internal state of a sample. These CT exposures convert the inner density distribution of a sample into images, and by viewing these images, we can check whether there are defects inside a sample. In addition, obtaining 3D images of a sample through CT imaging and analyzing them, we can determine the three-dimensional distribution of defects, measure internal geometries, and convert the data into computational models (polygon models). This data can be utilized across a wide range of applications from reverse engineering to quality control and defect analysis. Several uses of CT X-ray imaging are shared in the Use Case section.

Check Use Case here

Industrial X-ray CT systems are classified into four areas based on their output. In general, high-energy CT scanning involves output of 1 MV and higher. millifocus CT scanning ranges from 450 to 600 KV, microfocus CT scanning ranges from 100 to 300 KV, and nanofocus CT scanning is for outputs of 180 KV and lower. As penetrability increases with output, making it possible to image large and high-density samples, high-energy CT scanning is utilized to observe large samples made from relatively high-density materials such as aluminum and steel automotive parts, cast or welded products, tires (including wheels) and archeological artifacts. Millifocus CT scanning is often used to image large cast-metal or composite material products, while microfocus CT scanning is used for small precision devices, electronic components, integrated circuits, and so on. Lastly, nanofocus CT scanning is employed when observing minute precision components, electronic components and integrated circuits.

Hitachi's high-energy X-ray CT systems support up to 9 MV of output, among the highest in the world. This allows large components such as automotive motors, engine parts and vehicle battery packs to be imaged in their entirety. In recent years automotive manufacturers have been exploring "giga casting," an optimized construction method for the integrated aluminum die-casting of ultra-large automotive components. As a result, there is an increasing demand for the non-destructive analysis of structural components and products that are even larger than before.

A wide variety of objects can be imaged, from low-density materials such as rubber and acrylic, to high-density metals such as steel and copper. As X-rays need to pass through a sample for it to be imaged and X-ray penetrability varies by material, the size of the sample that can be imaged also varies.
The higher the X-ray energy, the greater the variety of samples that can be imaged, while also allowing large samples to be imaged.
However, X-rays can damage the DNA of living things, and semiconductors can also be damaged by radiation, so caution is required. Please contact us for more information.

The sample is placed on a turntable and rotated 360 degrees to obtain X-ray penetration data, which is used in dedicated software to create CT tomographic images. Hitachi High-Tech's CT systems use the fan beam method to create a single tomographic image with a single rotation of the turntable. When creating three-dimensional images, the turntable is shifted slightly up or down before the turntable is rotated in order to obtain tomographic images of layers that are different heights. These tomographic images from different heights are then layered to construct a 3D image.

As powerful X-rays are used, the samples are affected in the following ways.

• DNA damage
• Acrylic and other resins may become discolored
• Radiation damage
• Introduction of radioactivity in samples

Please contact us to learn more about the impacts on specific samples.