The Application Of The Combination Of Adaptive Statistical Iterative Reconstruction And Auto Tube Current Modulation In Low Dose CT Scanning

Objective: With the popularity of multi-slice spiral CT (MS CT)，thequality of image and accuracy of clinical diagnostic is has greatlyimproved. But the radiation dose of abdominal CT scanning has alsoincreased. To reduce the radiation dose has become one of the importantissues to the radiologist. Our studies showed a low dose abdominal CTtechnique, which combined adaptive iterative reconstruction algorithm(ASiR) and automatic tube current modulation, which was related by theparameter of noise index (NI), The first study observed ASiR techniqueapplication to low dose abdominal CT scanning；the second studyresearched ASiR technique application to the patients with liver lesions.Methods: All patients who performed abdominal CT scanning wererandomly divided into3groups in order sequence, Group A（NI=8），Group B（NI=9），and Group C (NI=11), By used different ASiR imagereconstructment of30%,40%,50%respectively in the first study, the results were denoted with A1, A2, A3, B1, B2, B3, C1, C2, C3in eachgroup. The second study used30%ASiR image constructed in thepatients with liver lesions. The dose-length product (DLP) of each groupwas recorded and the radiation effective dose (ED) was estimated, thevalue of reconstructed image noise was calculated in each group, imagequality was evaluated by two physicians through5-point system.Results: In the fist study, all image quality of each groups were goodenough for clinical diagnosis. The average of effective dose in Group Awas (5.74±1.45) mSv, group B was (3.35±1.35) mSv, group C was(2.57±1.71) mSv. Image noise in A3group was the lowest ((6.80±0.67)Hu,(10.02±0.88) Hu,(7.91±0.81) Hu), and image quality score washighest (4.43±0.50) points. In the second study, The image quality of9groups were up to the standard level of clinical diagnosis, and had nosignificant difference in the diagnostic characteristics of liver lesions. Theeffective dose in Group A was (5.76±1.80) mSv, group B was (3.19±1.06) mSv, group C was (2.57±0.67) mSv.Conclusions:①All50%ASiR image reconstruction imagesshowed the better quality and lower noise in each group respectively.②The combination of ASiR and automatic tube current modulation helpto reduce radiation dose in abdominal CT scanning.