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  Reasons for streak artifacts 

  in reconstructed CT slices 

Excluding from the consideration streak artifacts caused by metal (see the section of our site devoted to metal artifact reduction) there are still many reasons for streak artifacts in CT slices. First, severe streaks can be caused by asymmetric high-density objects (like bones) under conditions when low-dose data acquisition can not correctly represent the line integral. Other possible causes are  object motion or/and misalignment in the  scanner geometry description. And finally, streaks can be the result of angular under-sampling, aggravated by missing projections. 

Streak And Metal Artifact Reduction Algorithm.Pig abdominal scan. Partial slice.

Pig abdominal scan, partial slice. Streaks caused by both beam hardening and angular under-sampling

Streak And Metal Artifact Reduction Algorithm. Head phantom scan (160 projections over 360 degrees).. Partial slice

Head phantom scan (160 projections over 360 degrees). Streaks (appearing as a typical pattern noise) are caused by angular under-sampling. 

  SAMARA: Streak And Metal 

  Artifact Reduction Algorithm 

Exxim has developed and implemented an iterative  algorithm for 3D reconstruction, which is more tolerant to input data imperfections than the standard Feldkamp method. Such data imperfections can have any nature, e.g. absorption non-linearities or scanner geometry misalignments. One possible field of application of the method  is streak artifact reduction.  

 SAMARA technology is available as an option 

in COBRA starting version 4 

Exxim's  Streak And Metal Artifact Reduction Algorithm (SAMARA) does not depend on where streaks come from

Modern research has found some algorithms and techniques reducing streaks in reconstructed images. The best known practical solutions are satisfactory in some cases but require knowledge of the streak source (they are case-dependent). However, in medical practice it is often hard to pinpoint the source  of streaks. Usually this is even impossible because the streaks are caused by a combination of reasons listed on the left. This situation is typical for (but not restricted to) cone- beam CT with non-rigid gantries (C-Arms, radiotherapy treatment heads, etc). SAMARA technology (available as an option in COBRA starting version 4) provides significant reduction of streaks in reconstructed images independent of the source of streaks.

SAMARA (Streak And Metal Artifact Reduction Algorithm) is efficient technology 

to get streak-free images  

Streak And Metal Artifact Reduction Algorithm.Result of implementing SAMARA.

Pig abdominal scan. Partial slice, the same as shown in the left side. Result of implementing SAMARA.

Streak And Metal Artifact Reduction Algorithm.Result of implementing SAMARA.

Head phantom scan (160 projections over 360 degrees), the same as shown on the left. Result of implementing SAMARA.

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