ASIR-V and 80 kVp in abdominal CT angiography：evaluation of image quality，radiation dose，and iodine intake

Abstract:

Objective：To examine the effects of 80 kVp on radiation dose，iodine intake，and image quality for abdominal computed to－mography angiography（CTA）. Methods：Abdominal CTA was performed in 49 patients（20≤BMI≤23） using GE Revolution CT. The patients were divided based on tube voltage into group A（n=27，80 kVp） and group B（n=22，120 kVp）. With the exception of kVp，all scanning parameters in the two groups were the same：automatic mA，50% ASIR-V，default NI，1.25 mm thickness，HD mode，Stnd reconstruction，80 mm detector width，and 0.5 s scan time. Iohexol contrast agent（350 mgI/mL） was administered at 300 mgI/kg（4 mL/s） in group A and at 500 mgI/kg（5 mL/s） in group B，and was automatically tracked at a threshold of 220 HU. The mean CT and SD values of the abdominal aorta，abdominal trunk，common hepatic artery，splenic artery，superior mesenteric artery，and erector spinae at those levels were measured. Image quality（volume rendering and maximum intensity projection），contrast-to-noise ratio（CNR） and signal-to-noise（SNR） of the abdominal artery，volume CT dose index（CTDIvol），dose-length product（DLP），and total iodine intake were determined and compared between the two groups using the SPSS software. Results：There was no significant difference in the CTA image score between group A（4.58±0.51；κ=0.915） and group B（4.32±0.58，κ=0.946）（P>0.05）. The CT values of the abdominal aorta，common hepatic artery，splenic artery，and superior mesenteric artery were signifi－cantly higher in group A（584.09±63.54 HU，503.22±58.72 HU，486.44±74.47 HU，and 535.23±54.94 HU，respectively） than in group B（407.89±60.78 HU，368.57±45.31 HU，371.88±49.55 HU，and 387.83±55.85 HU，respectively）（all P<0.05）. The SNRs and CNRs were also significantly higher in group A than in group B（both P<0.05）. Compared with group B，group A had significantly lower CTDIvol（3.34±0.22 mGy vs. 8.78±0.93 mGy；61.96% reduction） and DLP（172.77±13.75 mGy·cm vs. 438.30±58.23 mGy·cm；60.58% reduction）. The total iodine intake of each patient was reduced by 39.67% in group A（300 mgI/kg） compared with group B （500 mgI/kg）. Conclusion：Abdominal CTA at a low tube voltage of 80 kVp（20 kg/m2≤BMI≤23 kg/m2） significantly reduces the radiation dose and contrast agent intake in patients，and improves CNR and SNR of the abdominal aorta and its major branches.