|
 |
|
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.
|
|
|
|
Pig
abdominal scan, partial slice. Streaks caused by
both beam hardening and angular under-sampling
|
|
|
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
|
|
|
|
Pig
abdominal scan. Partial slice, the same as shown
in the left side. Result of implementing SAMARA.
|
|
|
|
Head
phantom scan (160 projections over 360 degrees), the same as shown
on the left.
Result of implementing SAMARA.
|
|
|
|
Visit
the GALLERY to see more
examples
|
|
|
|
|
|
|
 |
