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[Clinical use of software-controlled x-ray tube modulation with "Smart-Scan" in spiral CT]
K J Lehmann1, J Wild, M Georgi
1Institut für Klinische Radiologie, Klinikum der Stadt Mannheim, Fakultät für Klinische Medizin Mannheim der Universität Heidelberg.
Purpose:
The modulation of tube current during 360 degree-rotation for equalization of local differences in absorption is able to reduce patient exposure in spiral-CT. The impact on CT investigations of thorax, abdomen and pelvis and the influence of patient geometry within the slice on the decrease of tube current are evaluated.
Methods:
300 spiral-CT's were performed on a HiSpeed Advantage scanner (GE) using a software-triggered modulation of tube current ("Smart-Scan"). The local absorption was measured in the 100 central channels of 2 scoutiviews (lateral and a.p.) and used for anatomical adapted modulation. The reduction of exposure as well as the height and width of the body cross-section were measured in reference slices of 100 thorax, 100 abdomen and 100 pelvis examinations.
Results:
The use of "Smart-Scar" enables a decrease of tube current of 7% in thorax, 6% in abdomen and 11% pelvis. There is a significant correlation between the height and width of body cross-section and the reduction of exposure for examinations of thorax and abdomen, but not of the pelvis.
Conclusion:
Independent of patient geometry the clinical use of "Smart-Scan" achieves the pelvis. Anatomical regions with an oval body cross-section show a decrease of x-ray tube current, too.