Abstract:
HTML
Purpose: We evaluate methods for a reduction of spiral artifacts
("windmill-artifacts") in multi-slice spiral CT.
Methods and Materials: Independent of the image reconstruction approach used,
rotating spiral artifacts ("windmill-artifacts") at z-inhomogeneous
high density structures such as the ribs are an image quality problem for
multi-slice spiral CT. To reduce these artifacts, an adaptive spiral
interpolation approach has been proposed (J. Hsieh, Proc. SPIE Int. Symp. Med.
Imag, 2003), relying on a weighted combination of two different spiral
interpolations for each projection sample. An alternative approach presented
here is oversampling in the z-direction during spiral acquisition which allows
the use of spiral interpolation functions reducing windmill artifacts while
maintaining spiral Slice Sensitivity Profiles (SSP). Technically, the
oversampling can e. g. be realized by a periodic motion of the focal spot of
the X-ray tube in the z-direction. The motion is synchronized with the data
read-out, subsequent projections are shifted by half a collimated slice width
in the center of rotation. We compare artifact suppression for both approaches,
using simulated CT-data of anthropomorphic thorax- and head phantoms with 16
and 32 rows at pitch 1 and 1.375. We evaluate spiral SSPs and transverse
resolution within the entire field of measurement (FOM).
Results: Both adaptive spiral interpolation and over-sampling in the
z-direction reduce multi-slice spiral artifacts. Better artifact suppression is
achieved with over-sampling in the z-direction. With the adaptive spiral
interpolation, transverse resolution is locally degraded, depending on the
z-structure of the object scanned. With z-over-sampling, transverse resolution
is maintained in the entire FOM. SSPs are well-shaped and identical to SSPs
without over-sampling.
Conclusion: Over-sampling in the z-direction by means of a periodic motion of
the focal spot of the X-ray tube is an efficient means to reduce multi-slice
spiral artifacts while maintaining transverse resolution. (T.G.F., H.B., K.S.,
S.S. are employees of Siemens Medical Solutions.)
Questions about this event email: thomas.flohr@siemens.com
Flohr PhD, T,
Evaluation of Approaches to Reduce Spiral Artifacts in Multi-Slice Spiral CT. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3104740.html
