Feasibility study of automatic tube current modulation technique of 64-slices CT for reducing radiation doses of lower extremity arterial imaging

Objective To investigate the value of automatic tube current modulation technique of 64-slices CT for reducing radiation doses of lower extremity arterial imaging. Methods Adjustment tube current through the pre-test changes in the noise index (NI), obtained the image quality and radiation dose with better matches when NI value of 10 HU. Fifty-two diabetic and hypertensive patients suspicious of having lower extremity occlusive disease underwent 64-slices CT volume scan arranged from infra-renal aorta to feet and separated random into 2 groups. The experimental group of 26 patients(FM) used fixed tube current of 300 mA technique, and the the follow-up of 26 patients (control group) used automatic tube current modulation (ATCM) technique with NI= 10. We selected the observing levels at infra-renal aorta, femoral artery of hip joint level, popliteal artery and anterior tibial artery at ankle level. Both sets of image quality, image noise and radiation dose were analyzed by using t-test. Results The radiation dose level of ATCM group[ CTDI_(vol): 10.81 mGy,DLP: (1280.40±124.70) mGy·cm] was lower than FM group[CTDI_(vol): (5.14±1.23) mGy, DLP: (582.86±150.41) mGy·cm] by 54.4% , difference between the two groups was statistically significant(t_(CTDIvol) = 13.13, t_(DLP) = 17.36, P 0.05). Conclusion Lower extremity CT scanning with automatic tube current modulation technique (NI = 10) can greatly reduce the radiation exposure by 54.4% and maintain the equivalent image quality. Key words: Lower extremity; angiography;  Radiation dose;  Image noise;  Tomography;  X-ray computed