Optimizing Abdominal Spectral CT Angiography Imaging with Double Low Scan Protocol in Small BMI Patients

Purpose: To explore the feasibility and application value of abdominal spectral CT angiography imaging with double low scan protocol. Methods: Total of 367 patients with the BMI ≤ 25 kg/m<sup<2</sup< who were suspected abdominal disease was performed abdominal CT angiography imaging prospectively. Firstly, these patients were divided into experience group and control group according to the first time of treatment and then were divided into two subgroups according to the BMI: Experience 1 group or control 1 group(BMI ≤ 22) and experience 2 group or control 2 group(22 BMI ≤ 25). The scan protocols as follows: Experience 1 group(80 kVp, 50% ASIR, 270 mgI/mL), experience 2 group(100 kVp, 50% ASIR, 270 mgI/mL), control 1 group(120 kVp, FBP, 350 mgI/mL), control 2 group(120 kVp, FBP, 350 mgI/mL). To compare the CT values of aorta abdominalis, CNR, FOM, CDIvol, iodine content of contrast agent and imaging quality score of renal arteries. Results: The CT values of aorta abdominalis of group experience 1, experience 2, control 1, control 2were(601.75 ±67.11) HU,(459.87 ±49.17) HU,(436.55 ±84.12) HU,(432.15 ±87.68), respectively and CT values of groups experience were higher than that of groups control(<i<P</i<<0.05). The CNR of group experience 1, experience 2, control 1, control 2 were(19.01 ±2.66),(15.24 ±2.52),(12.42 ±2.68),(10.24 ±2.22), respectively and CNR of groups experience were higher than that of groups control(<i<P</i<<0.05). The FOM of group experience 1, experience 2, control 1, control 2 were(69.72 ±29.75),(33.44 ±8.87),(20.08 ±8.05),(15.21 ±10.12), respectively and FOM of groups experience were higher than that of groups control(<i<P</i<<0.05). The CTDI<sub<vol</sub< of group experience 1, experience 2, control 1, control 2 were(5.41 ±1.38) mGy,(6.98 ±1.49) mGy,(9.87 ±2.97) mGy,(12.02 ±5.21) mGy, respectively and CTDI<sub<vol</sub< of group experience 1 was reduced by 45.19%(4.46/9.87) than that of control 1 and experience 2 was reduced by 41.93%(5.04/12.02) than that of control 2. The iodine Concentration of group experience and group control was 270 mgI/mL and 350 mgI/mL respectively. The iodine Concentration of group experience was reduced by 22.86%(80/350). The scores of renal arteries of group experience 1, experience 2, control 1, control 2 were(4.61 ±0.47),(4.22 ±0.59),(3.73 ±0.72),(3.93 ±0.66), respectively. The score of group experience 1 was higher than that of group control 1(<i<P</i<<0.05) and there was no statistical significance between group experience 2 and group control 2. Conclusion: The abdominal spectral CT angiography imaging with double low scan protocol can reduce radiation dose and iodine content sharply for the patients with small BMI, and which will be applied to clinic.