Preliminary study of improved quality of computed tomographic angiography on tumor blood supply arteries of gastrointestinal tract malignant tumors with low tube voltage and low concentration contrast medium

OBJECTIVE: To assess the image quality of gastrointestinal tract malignant tumors arteries using low tube voltage, low contrast medium concentration and 50% adaptive statistical iterative reconstruction (ASiR) algorithm. METHODS: A total of 58 patients with pathologically confirmed gastrointestinal tract malignant tumors and body mass index (BMI) under 22 kg/m² undergoing computed tomography (CT) scanning during March‐December 2013. They were randomly divided into group A (270 mgI/ml of contrast medium, 80 kVp tube voltage scanning and 50% ASiR; 21 males and 11 females with an age range of 40‐90 years) and group B (350 mgI/ml of contrast medium, 120 kVp routine tube voltage; 22 males and 4 females with an age range of 40‐76 years). The inter‐group differences of age and gender ratio were compared with Mann‐Whitney U and Fisher exact tests respectively. Two independent radiologists reviewed reconstructions and separated the reconstructed image into 5 points according to image quality. The CT value of tumor blood supplying artery (CT1 value) and fat in anterior abdominal wall (SD value) were measured and image noise, contrast‐to‐noise ratio (CNR) and figure of merit (FOM) calculated. The interobserver variation was estimated by weighted kappa statistics and intra‐class correlation coefficients (ICC) test. The point of image quality of two groups was compared by Mann‐Whitney U test. The paired Student t test was used to compare the inter‐group differences in CT1, SD, CNR, FOM and CT dose index (CTDIvol). RESULTS: No inter‐group difference existed in patient age or gender ratio. The consistency of two radiologists was excellent (kappa value > 0.80; ICC value > 0.75). The subjective image quality scores of tumor blood supplying arteries showed no inter‐group difference (P = 0.09). The tumor blood supply arteries CT value, CNR and FOM of group A (459 ± 69 HU, 20.2 ± 3.3 and 85 ± 37) were significantly higher than those of group B (250 ± 42 HU, 9.3 ± 1.9 and 9 ± 4) (both P < 0.01). The SD value of group A (20.0 ± 1.7) was obviously lower than that of group B (22.4 ± 3.2) (P < 0.01). And the CTDIvol of group A (5.2 ± 1.2 mGy) was obviously lower than that of group B (13.5 ± 4.7 mGy) (P < 0.01). CONCLUSION: For patients of BMI ≤ 22 kg/m², low tube voltage and low contrast medium concentration scan condition with 50% ASiR algorithm is feasible for acquiring better quality image and ensuring significant reduction in effective dose.