CT能谱成像减少对比剂用量在肝脏增强扫描中的应用

Application of spectral CT in reducing contrast medium dosage in liver enhancement

目的:探讨能谱CT降低对比剂用量在腹部增强扫描中的可行性。方法 :收集50例行腹部增强扫描的患者,排除肝癌、肝硬化等,随机分为2组。A组(25例):行CT能谱增强扫描(个性化选择能谱扫描协议),对比剂用量350 mgI/kg体质量,重建60 keV 40%(ASIR)图像。B组(25例):传统120 kV扫描协议(根据NI 10~5 mm自动选择),对比剂用量500 mgI/kg体质量。2组注射流率依据对比剂总量和总注射时间25 s而定。分别记录2组CT剂量容积指数(CTDIvol)。在120 kV和60 keV图像上分别测量动脉期腹主动脉、门静脉期门脉主干、正常肝实质、竖脊肌的CT值及SD值,并计算相应的对比噪声比(CNR)。测量结果采用独立样本t检验。结果:2组体质量指数无明显差异(P> 0.05)。A组腹主动脉CT值及CNR值和门静脉主干CT值及CNR值均高于B组(均P<0.05)。2组肝实质CT值及CNR差异均无统计学意义(均P> 0.05)。2组竖脊肌SD值差异无统计学意义(P> 0.05)。2组CTDIvol相比,差异无统计学意义(P> 0.05)。A组对比剂碘摄入量较B组约减少22%(P<0.05)。结论:能谱CT在不增加辐射剂量和不影响图像质量的同时可显著减少对比剂碘摄入量。

Objective：To evaluate the feasibility of using spectral CT in contrast-enhanced abdominal scans to reduce the total iodine dosage while maintaining image quality. Methods：Prospectively randomized 50 patients with contrast-enhanced abdominal CT to 2 groups. 25 cases of group A underwent spectral CT with 350 mgI/kg contrast injection protocol,spectral CT images at 60 keV reconstructed with 40%ASiR,and 25 cases of group B underwent the conventional 120 kVp CT with 500 mgI/kg contrast injection. The injection rate was adjusted to have the total injection time of 25 s for both groups. For the 120 kVp scan,tube current （mA） was automatically adjusted to achieve noise index （NI） of 10 HU at 5 mm image slice; and for spectral CT,a mA was selected to produce similar CT dose index （CTDI） as the 120 kVp protocol for NI=10 HU. CTDI were recorded. CT value and standard deviation （SD） of the abdominal aorta in arterial phase （AP）,main portal vein in venous phase （VP）,live rparenchyma and erector spinae on the 120 kVp images and 60 keV spectral CT images were measured to calculate contrast-noise-ratio （CNR）. Measurements were compared with independent sample t-test. Results：The body mass index between 2groups showed no difference （P〉0.05）. CT value and CNR for the abdominal aorta and the main portal vein of group A were higher than those of group B （all P〈0.05）. CT value and CNR for the liver parenchyma,SD value for the erector spinae and the CTDIvol of the 2 groups had no differences （all P〉0.05）. Group A with spectral CT achieved 22%! iodine dose reduction compared with group B （P〈0.05）. Conclusion：Spectral CT can reduce the total iodine dosage at the same image quality and without radiation dose increase.