| QI Heng-tao,QIN Wei-chang,WANG Wei.Measurement and evaluation of image noise at 64 slice spiral CT[J].Chinese Journal of Radiological Medicine and Protection,2007,27(2):195-197 |
| Measurement and evaluation of image noise at 64 slice spiral CT |
| Received:June 07, 2006 |
| DOI： |
| KeyWords:Tomography X-ray computed Quality control Noise |
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| Abstract:: |
| Objective To measure and evaluate the CT image noise and study the influencing factors at a 64-slice spiral CT system. Methods Using SOMATOM Sensation 64-slice spiral CT and body phantoms, spiral scan and axial scan were employed with different scan parameters including slice thickness, mAs, kV, reconstruction algorithm, FOV and pitch. Then standard deviation of CT images were measured and analysed. Results At 160 mAs, the image noise are 8.4, 9.3, 10.7, 13.0, 21.8, and 28.3 at different slice thickness of 10, 7, 5, 3, 1 and 0.6 mm. At 120 kV, the noise are 8.4, 9.5, 41.4, and 44.5 at different reconstruction algorithm of B30 smooth, B40 smooth, B60 sharp, B70 sharp. For nominal thickness of 5 mm, the noise are 10.6, 11, 10.7, 10.5, and 10.9 at different pitch of 0.5, 0.75, 1, 1.25, and 1.5. The noise increase along with increase of diameter of the phantoms when spiral scan and axial scan are employed. The image noise are 7.83, 8.10, and 10.47 at different FOV of 200 mm×200 mm、150 mm×150 mm、100 mm×100 mm. Conclusions The image noise decreases along with increase of slice thickness, mAs, kV and FOV, and increases along with increase of diameter of the phantoms and the reconstruction algorithm of high resolution. But it is independent of pitch and hardly has difference for helical and axial scanning. |
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