Artifact Reduction

TomoShop® has strong tools for reducing various type of artifacts and noises.

Ring artifact reduction

As you can see the below CT reconstruction Images from Flat Panel detector, there are ring artifacts and noises. Using Reduction tools of Ring artifacts on TomoShop®, the ring artifacts and noises in the CT reconstruction images are reduced.

☟ Video for reducing ring artifact by TomoShop®

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Vertical artifact reduction

The CT reconstruction images from Flat Panel detector is shown below. There are vertical artifacts and noises. Using Reduction tools of Vertical artifacts on TomoShop®, the vertical artifacts and noises are reduced.

☟ Video for reducing ring and vertical artifact by TomoShop®

Countermeasures against ring artifact caused by defective pixels, unevenness of detector element sensitivity

Ring artifacts and vertical artifacts might be caused by defects in the elements of the camera detector or by nonuniformity of reception sensitivity. Regular ring artifacts caused when the center of the actual scan trajectory overlap their center, however, some ring artifacts may not overlap in their centers. This is the case that is common in ring artifacts that occur when actual scan start-up does not become a circumferential orbit, and these ring artifacts can not be reduced by conventional artifact reduction methods.

TomoShop has strong artifacts reduction tools that is reliably reduced even with ring artifacts that can not be handled by conventional methods by detecting the defective pixels of the projection image data before the reconstruction and at the same time estimating the nonuniformity of the element sensibility of the detector and using the estimated information at the time of reconstruction stage.

Reduction of ring artifacts existing in non-concentric circles of images

Ring artifacts that are not on the concentric circle of the image occur when there is an errors in the actual scan trajectory and its shape does not become circumference. In such a case, it is impossible to reduce this type of ring artifact by conventional artifact reduction method. TomoShop’s artifact reduction tools can effectively and strongly reduce those irregular ring artifacts even if the scan trajectory is not circumference by using defect pixel information and sensitivity variation information at the time of reconstruction stage.

The ring artifact occurred at a position deviated from a concentric circle:

The reduction result by using conventional method :

The reduction result by using TomoShop’s method :

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Metal artifact reduction

Metal artifacts occur when the sample contains metals in the CT reconstruction images. It disturbs accuracy of inspection.

TomoShop® has strong metal artifact reduction tools that reducing metal artifacts strongly in the CT reconstruction images and it enable to present more clear and accurate CT reconstruction mages as CT scan result with fast processing, so that you can save the time.

☟ Video for metal artifact reduction by TomoShop®

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Cupping artifact reduction (beam-hardening reduction)

One of the big issue is Cupping Artifacts for X-ray CT system. It is very difficult to deal with this noises by modern X-ray CT technology. However, TomoShop can provide the solution of this tricky issue.

The problems caused by cupping artifact (beam-hardening problem) are:

• Impossible to examine the area where cupping artifact is occurring.
• Causing problem with displaying the accurate situation of the samples.
• Causing problem with 3D measurement. Unable to get accurate value for measuring.
• Others.

The CT reconstruction software TomoShop® series have the cupping artifact reduction (cupping effect reduction) tools for solving this problems in CT reconstruction images.

 

☟ Video for cupping artifact reduction (Beam-hardening) by TomoShop®

☞ Go to TomoShop® (CT reconstruction software)

 

How to reduce beam-hardening (cupping effect) by CT scanning

X-ray CT use Continuous X-rays. Continuous x-rays contains many power levels of X-rays such as strong power, middle power and weak power., etc.

Continuous X-rays ☟

 

 

When continuous x-rays are penetrating through a sample, it is like below (Pleochroism, Polychromaticity).

 

As you can see that “Strong” can penetrate though well, but not “Middle” and “weak”. From this, it can be said that “Middle” and “Weak” are causes of artifacts (beam-hardening., etc). So it appear to be said that using only “Strong” prevent the cause of artifacts.

 

So, how can it possible to use only “Strong” power of X-ray?

One of the answer is using metal filters. Set metal filters between X-ray source and a sample.

 

The materials of Metal board (metal filter) are copper, aluminum and others:

• Copper -> high interception rate. If the samples are hard materials such as metal, it is useful.
• Aluminum -> low interception rate. If the samples are soft materials, it is useful.
• Others -> need to be checked

The thickness of metal board:

• Copper -> about 3mm (maximum)
• Aluminum -> need to be checked
• Others -> need to be checked

X-ray power (tube voltage, tube current) should be high level or maximum level.
*Some samples are fragile to x-ray, so the level of x-ray should be concerned up to the sample. 

From the information above, the tests should be conducted and finding the best combination of CT scanning setting to reduce beam-hardening (cupping effect).