[Characterization of motion artifacts in multi-slice spiral CT].
OBJECTIVE
Motion artifacts in multi-slice spiral CT (MSCT) resulting from object motion in and against the table feed direction (z-direction) are examined using a spherical phantom. For image interpretation of complex anatomic structures, qualitative reference points are, also applicable to selected, which are ECG-gated cardiac imaging. In this case the motion of the coronary vessels in phase with the cardiac contraction must be considered.


METHODS
Measurements are obtained with a multi-slice spiral CT with a rotation time of 500 ms for 4 x 1.0 mm and 2 x 0.5 mm collimation. The phantom consists of an acrylic glass body with imbedded glass beads of 1, 2, and 3 mm diameter. The object motion is sinusoidal with an amplitude of 5 mm and frequencies of 60/min and 90/min. Compensation of the table feed by object motion is examined as a special case.


RESULTS
Small parameter changes can induce a strikingly different image quality, and the moving objects emerge in different slices. Depending on the phase of the movement with respect to the CT scan, objects up to a size of 3 mm can vanish completely or appear hyperintense in the image. The model investigated is also applicable to ECG-gated cardiac imaging for the detection of stenosis. It can explain variations in the reproducibility and absolute score values of the calcium scoring.


CONCLUSIONS
The presented considerations and results must be taken into account in image interpretation with possible object motion in the z-direction. Variations in the determination of the degree of stenosis or in calcium score measurements can be explained by different vessel motion during the diastolic heart phase.
Graf
H
H
Sektion für Experimentelle Radiologie, Eberhard-Karls-Universität Tübingen. hansjoerg.graf@med.uni-tuebingen.de
Heuschmid
M
M
Küttner
A
A
Kopp
A F
AF
Claussen
C D
CD
Schick
F
F
D016477:Artifacts; D003327:Coronary Disease / Q000175:diagnosis / Q000000981:diagnostic imaging*; D023921:Coronary Stenosis / Q000175:diagnosis / Q000000981:diagnostic imaging; D003971:Diastole; D004562:Electrocardiography; D006339:Heart Rate; D006801:Humans; D009038:Motion; D019047:Phantoms, Imaging; D019904:Polymethyl Methacrylate; D036542:Tomography, Spiral Computed / Q000379:methods*
D019904:Polymethyl Methacrylate