Purpose
On coronarycomputed tomography angiography (CCTA),
we have knowing that mis-registration artifacts are caused by heart rate variation,
patient's incomplete breath holding,
patient'smotion during scan,
ECG signal errors and so on [1-9].
Among those causes,
different R-R intervals over cardiac cycles can affect the volume data and stair-step artifacts could be developed [10] (Fig.
1).
However,
it could be detected even in CT images obtained using the data from the same R-R intervals.
We thus hypothesized cradle sagging during the scan could affect the development ofstair-step...
Methods and materials
Phantom
CT scans of pulsating cardiac phantom with artificial vessels (inner diameter : 4.5 mm,
outer diameter : 5 mm) were performed using 64 MDCT (Discovery CT750 HD; GE Medical System,
Milwaukee,
Wisconsin,
USA) in retrospective ECG gating.
Two straight artificial vesselswereattached to the surface of arubber chamber.
Both artificial vesselsand rubber chamber were filled with mixture (700 HU),
combinedcontrast media andsaline.
Simulated heart rates of thepulsating cardiac phantom were set regularly at 60 beats per minute (Fig.
2).
DataAcquisitionProtocols
Detector configuration
64 × 0.625...
Results
Assessment of Tilt angle of cradle
Tilt angles at three different locations(95 cm,
125 cm and 155 cm location) showed statistically significant correlation with the increased weights on the cradle (r=0.91,
0.97 and 0.88 at each location,
P< 0.05) (Fig.
6).
Assessment of Images
In rotated vertically curved MPR images,
sagittal images showed more severestair-step artifactsthan coronal images (Fig.
7).
Moreover,stair-step artifactswere perceived more in the CT images obtained at the cradle withhigher tilt angle (Fig 6,
7).
Conclusion
Tilt angle of the cradle showed significant correlation with the weights and locations of phantom,and stair-step artifactswere noted more when higher tilt angle was detected.
To reduce stair-step artifacts,
cradle sagging should be minimized to avoid the tilting of the cradle which might affect the CT volume data.
Personal information
Snag-Woo Lee,
RT.
Radiological Technologist,
Department of Radiology,Asan Medical Center,
Seoul,
South Korea.
[email protected]
Joon-Won Kang,
M.D.,
Ph.D.
Department of Radiology and Research Institute of Radiology,University of Ulsan College of Medicine,
Asan Medical Center,Seoul,
South Korea.
[email protected]
Hyun Jung Koo,
MD.
Diagnostic radiologist,
Department of Radiology,Asan Medical Center,
Seoul,
South Korea.
Sun-Ki Kim,
RT.
Radiological Technologist,Department of Radiology,Asan Medical Center,
Seoul,
South Korea.
Dae-Keon Seo,
RT.
Radiological Technologist,Department of Radiology,Asan Medical Center,
Seoul,
South Korea.
References
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Herzog A.
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Body physique and heart rate variability determine the occurrence of stair-step artefacts in 64-slice CT coronary angiography with prospective ECG-triggering,
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Raff GL,
Gallagher MJ,
O'Neill WW,
et al.
Diagnostic accuracy of noninvasive coronary angiography using 64-slice spiral computed tomography.
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Maruyama T,
Takada M,
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Radiation dose reduction and coronary assessability of prospective electrocardiogram-gated computed tomography coronary angiography.
Journal of the...