Low-dose 16-slice spiral CT thoracic angiography using Z-axis modulation / 中华放射学杂志

ABSTRACT

Objective To explore the feasibility of low dose in MSCT thoracic angiography using Z-axis modulation. Methods The consecutive 60 patients were averagely divided into 3 groups and underwent thoracic angiography with a Toshiba Aquilion 16 scanner. The whole chest acquisition was commenced in automatic exposure control with Z-axis modulation 20-25 seconds after the contrast material was administered at the rate of 3.5-4. 0 ml/s. With the noise index (SD) as the variable, three study groups were classified as A (SD = 12) , B (SD = 15 ), and C (SD = 18 ). The mAs value per slice and the number of slices were recorded. The noises and artifacts of the axial images and the acceptability of CT angiogram were evaluated. The difference among the groups was compared by using ANOVA or nonparametric Kruskal-Wallis test. The threshold of the P value was 0. 05. Results The mean mAs value (46. 4 ± 15.6) mAs in group A was the highest but the SD value (21.6 ±7.7) was the lowest. The mean mAs value ( 37. 0 ± 13.5 ) and the SD value ( 24. 0 t 5.4 ) in group B were the mediate. The mean mAs value ( 20. 7 ±6.3) mAs in group C was the lowe(s)t but the SD value ( 30. 7 ± 6.9) was the highest ( H = 31. 390, P =0. 000). The middle slice images in all patients had the smallest mAs (40. 9,31.3,17. 1 for group A,B,C,respectively; F =9. 578, H =22. 230, F =21. 180,P =0. 000) and SD values( 16. 3, 20. 0,25.4 for group A,B,C, respectively; H = 28. 982, H = 20. 824, H = 24. 396, P = 0. 000). The acceptability of CT angiogram in all patients was excellent. The CT value of descending aorta in group A, B, and C was ( 335 ± 85 ) HU,(334 ±56)HU, and (427 ± 63 )HU, respectively. Conclusion Low dose in MSCT thoracic angiography using Z-axis modulation is feasible. We can use low dose (20 mAs, etc. ) for CT angiography when the contrast is significant.