Problem cases with the reconstruction images of X-ray CT scan and the solution

Here, it discuses some typical issues that caused in CT scan.

Case 1: The problem that sample does not fit into the camera (Cupping Artifact)

In this issue, it is a possibility that the periphery of the horizontal cross section of the reconstructed image becomes brighter that is cupping artifact (beam-hardening, cupping effect)

Then,

Troubles occur in the displayed 3D image as well as conducting measurement and analysis. The solution for this problem is using the algorithm of the CT reconstruction software to reduce or delete cupping artifact.

As you can see the images of the left, TomoShop® can solve cupping effect.

See ☞ Cupping artifact reduction page.

See ☞ CT reconstruction software: TomoShop® page.

 

Case 2: Variability problem of camera element sensitivity (Ring Artifact, Vertical Artifact)

When there are problems that variations of camera element sensitivity, then ring artifacts will occur. Troubles occur in 3D display as well as conducting measurement and analysis.

The recommended solutions for this problem are:

  • Conduct CT scan with stronger tube voltage.
  • Examine whether there is a problem with the input element of the camera.
  • Use special tools of the CT reconstruction software to reduce the ring/vertical artifacts. etc

As you can see the below, TomoShop® can reduce ring artifacts and output clean and better reconstruction image.

Before

After

Vertical artifacts also occur with the problem that variations of camera element sensitivity. Troubles occur in 3D display as well as conducting measurement and analysis.
As you can see the below, TomoShop® can reduce vertical artifacts and output clean and better reconstruction image.

Before

See ☞ Ring artifact reduction page.

See ☞ CT reconstruction software: TomoShop® page.

 

Case 3: Incomplete problem of circular orbit (Axial Intensity Drop)

Incomplete problem of circular orbit will cause Axial Intensity Drop. TomoShop® has three ways to solve it.

See ☞ CT Image Reconstruction page.

See ☞ CT reconstruction software: TomoShop® page.

 

Case 4: Polychromatic problem of X-ray (Cupping Artifact)

Beam hardening is caused by a polychromatic problem of X-ray that is called cupping artifact (beam-hardening, cupping effect). Troubles occur in 3D display as well as conducting measurement and analysis. The recommended solution is using the special tools of the CT reconstruction software to reduce cupping artifact.

TomoShop® will solve this problem.

Before

After (TomoShop’s Method)

Consideration on a method of CT scanning for beam-hardening (cupping effect) reduction:

The one of the common method for beam-hardening reduction is using metal filters with adjustment of X-ray current. In this case, metals with low permeability such as copper, lead, etc. are commonly used. In this case, it uses only X-rays with strong energy and block X-rays with low energy, and it seems that there is some effect to reduce the beam-hardening (cupping effect) of metal parts.

However, this method also has problems. It is effective for metal parts susceptible to beam-hardening because it removes X-ray with weak energy of continuous X-rays and uses only high-energy X-rays. but the shape of soft parts other than metals can not be reproduce beautifully.

As a countermeasure, it is conceivable to change the type of metal filter to a metal with a relatively high transmittance of relatively weak X-rays such as aluminum. Ideally, CT scanning may be performed X-rays include with X-rays with low energy and beam-hardening problem should be manage to solve by using CT software’s function.

TomoShop has functions for doing beam-hardening reduction, so it is possible to provide an ideal solution for the beam-hardening (cupping effect) reduction.

See ☞ Cupping artifact reduction page.

See ☞ CT reconstruction software: TomoShop® page.

 

Case 5: The problem that X-ray is not transmitted (Metal Artifact)

Metal artifacts will occur by the X-ray can not be transmitted.

The recommendation solutions are:

  • CT scan with stronger tube voltage.
  • Use the artifact reduction tools of CT reconstruction software to reduce metal artifact. etc

TomoShop® has the metal reduction tools that will strongly reduce the metal artifacts.

Before

After

Before

After

See ☞ Metal artifact reduction page.

See ☞ CT reconstruction software: TomoShop® page.

 

Case 6: Rotation axis and camera center, displacement of the problem of orientation

Blur image problems will occur in the 3D image reconstructed by the rotation axis and the camera center and the direction of displacement of the problem. This can be corrected by automatic and semi-automatic by using TomoShop® (CT reconstruction software).

Before

After

The following items can be considered as countermeasures.

  • Adjusting the position of the stage rotation axis and the camera center and direction.
  • Control of temperature in installation location and equipment.

See ☞ Focusing Technology page.

See ☞ CT reconstruction software: TomoShop® page.

 

Case 7: Focus movement problem of stage rotation error and the rotation pass is not circle

Reconstruction in the conventional method is impossible because of the focus shift problem with shooting trajectory of stage rotation error and the rotation pass is not circle. TomoShop® can solve this problem.

The following items can be considered as countermeasures.

  • Adjustment of stage rotation mechanism.
  • Checking the status of the X-ray generator.
  • Check the installation status of the sample.
  • Equipment installation location and temperature control inside the equipment.

See ☞ Focusing Technology page.

See ☞ CT reconstruction software: TomoShop® page.

Case8: Motion artifact

Motion artifacts are a problem in which machine operation errors occur randomly due to vibrations that occur during the CT scan, and images of streak artifacts appear in the reconstructed images.

Satisfactory results can be obtained by the well-balanced functioning of the three mechanisms of the detector, stage, and X-ray generator for the CT imaging power mechanism. However, the problems that occur with these three mechanisms are different in nature and can be difficult to control well during CT scans. The motion artifact problem is a prime example of such a problem.

Motion artifacts caused by the movement of the stage shown in the figure on the left.

A stage that moves with errors. * The black spheres are attached on the stage as markers.

Before

After

The following items can be considered as countermeasures.

  • Adjusting the position of the stage rotation axis and the camera center and direction
  • Adjustment of stage rotation mechanism
  • Check the installation status of the sample
  • Checking the status of the X-ray generator
  • Control of temperature in installation location and equipment

See ☞ Focusing Technology page that show the solution by using TomoShop®.

See ☞ CT reconstruction software: TomoShop® page.