双低扫描技术在儿童腹部增强CT中的应用研究

Applied Research on Double Low Scanning Technique in Children’s Abdominal Enhanced CT

目的对比低管电压联合应用低浓度对比剂与传统管电压联合应用传统高浓度对比剂进行儿童腹部CT增强扫描时的碘摄入量、图像质量以及辐射剂量。方法搜集A、B两组各19例,分别采用传统管电压(120 kV)联合应用传统高浓度对比剂(Iodixanol 320)及低管电压(80 kV)联合应用低浓度对比剂(Iodixanol 270)行腹部CT增强扫描,均采用管电流智能毫安扫描技术采集图像,噪声指数(NI)=10。对两组动、静脉期的图像进行定量以及主观评价,并对比两组患儿的辐射剂量和碘摄入量。结果对比A、B两组患儿的动脉期图像中腹主动脉、腹腔干、肝总动脉、脾动脉、肠系膜下动脉,静脉期图像中下腔静脉、肝静脉、左肾静脉、右肾静脉,以及动、静脉期肝实质、脾实质、软组织和空气的CT值以及噪声值,计算各感兴趣区(ROI)的信噪比(SNR),对比噪声比(CNR),图像优良指数(FOM)。动脉期的腹主动脉、腹腔干各指标对比均有统计学意义(P<0.05)B组高于A组,动脉期的肝动脉、脾动脉以及肠系膜下动脉除了噪声值无统计学意义外(P>0.05),其余指标均有统计学意义(P<0.05)。动脉期的肝、脾实质各指标均无统计学差异(P>0.05)。静脉期下腔静脉和肝静脉中除了FOM比较无统计学差异(P>0.05),其余指标均有统计学差异(P<0.05)。左肾静脉噪声值和FOM无统计学差异(P>0.05),CNR和SNR有统计学差异(P<0.05),右肾静脉噪声值、SNR和CNR无统计学意义(P>0.05),CT值有统计学意义(P<0.05)。静脉期肝实质噪声值无统计学差异(P>0.05),其余指标均有统计学差异(P<0.05)。脾实质CT值和SNR比较有统计学差异(P<0.05),其余指标无统计学差异(P>0.05)。两组软组织和空气比较除了空气的CT值无统计学意义(P>0.05)其余指标均有统计学差异(P<0.05)。A组CT容积剂量指数(CTDIvol)、剂量长度乘积(DLP)、有效辐射剂量(ED)分别为(2.24±0.27)mGy、(81.21±17.97)mGy·cm、(2.43±0.53)mSv;B组为(1.91±0.3)mGy、(63.52±21.93)mGy·cm、(1.90±0.65)mSv。两组辐射剂量比较差异有统计学意义(P<0.05)。A组主观评分:(3.63±0.46)分;B组:(3.73±0.38)分,两组比较无统计学差异(P>0.05)。A组患儿的碘摄入量(10.69±1.91)g,B组患儿的碘摄入量(9.08±1.94)g,两组对比差异有统计学意义(P<0.05)。结论在儿童腹部增强CT中采用低管电压(80 kV)联合应用低浓度对比剂(Iodixanol 270)可以有效地降低儿童的辐射剂量以及碘对比剂的摄入量,同时能够满足临床诊断的要求。

Objective To compare the iodine intake,image quality and radiation dose of children undergoing enhanced abdominal CT scanning by low tube voltage(80 kV)combined with low-concentration iodinated contrast agent(Iodixanol 270)and traditional tube voltage(120 kV)combined with high-concentration iodinated contrast agent(Iodixanol 320).Methods Nineteen patients in group A and group B were scanned with conventional tube voltage(120 kV)combined with traditional high concentration contrast agent(Iodixanol 320)and low tube voltage(80 kV)combined with low concentration contrast agent(Iodixanol 270)respectively and images were collected using(NI=10)intelligent milliampere scanning technology of tube current in both groups.Quantitatively and subjectively,the enhanced abdominal arterial phase images of the two groups were evaluated and the radiation dose of the two groups was compared.Results Comparing the aorta,the celiac axis,common hepatic artery,splenic artery and inferior mesenteric artery in the arterial phase images of the children in groups A and B,venous phase images of inferior vena cava,hepatic vein,left renal vein,right renal vein,and the liver and spleen parenchyma in both periods,the CT value and noise value of soft tissue and air are used to calculate the SNR,CNR,FOM of the area of interest.All indexes of abdominal aorta and celiac trunk in the arterial phase showed statistical significance(P<0.05).Group B was higher than that of group A.The hepatic artery,splenic artery and superior mesenteric artery in the arterial phase showed no statistical significance except for the noise value(P>0.05),and the other indicators were statistically significant(P<0.05).There was no significant difference in liver parenchyma and spleen parenchyma between the two groups(P>0.05).In the venous phase,there was no statistical difference in the inferior vena cava and hepatic veins except for the comparison of FOM(P>0.05),and the other indicators were all statistically different(P<0.05).There is no statistical difference in the noise value and the FOM of two sets of the left renal vein whereas the CNR and the SNR have the statistical differences(P<0.05).The noise value,the SNR and the CNR of the right renal vein are not statistically significant(P>0.05),and the CT value is statistically significant(P<0.05).There was no statistical difference in the noise value of hepatic parenchyma in the venous stage(P>0.05),while the other indexes were all statistically different(P<0.05).CT value and SNR of splenic parenchyma in the venous phase were significantly different between the two groups(P<0.05),while other indexes were not statistically different(P>0.05).Comparison of soft tissue and air between the two groups showed no statistical significance except for CT value of air(HU)(P>0.05),and other indicators showed statistical difference(P<0.05).CTDIvol,DLP and ED in group A were(2.24±0.27)mGy,(81.21±17.97)mGy.cm,(2.43±0.53)mSv),and in group B were(1.91±0.3)mGy,(63.52±21.93)mGy.cm,(1.90±0.65)mSv,respectively.There was significant difference in radiation dose between the two groups(P<0.05).The iodine intake of the children in group A was(10.69±1.91)g,and that of the children in group B was(9.08±1.94)g.The difference between the two groups was statistically significant(P<0.05).Conclusion Low tube voltage(80 kV)combined with low-concentration iodinated contrast agent(Iodixanol 270)can effectively reduce the radiation dose and the intake of iodine contrast agents in children in enhanced abdominal CT scanning and at the same time meets the needs of clinical diagnosis.