腹部水模不同管电压、管电流CT扫描的研究

The study of CT scan with different tube voltage and current in Abdominal Water Model

目的通过不同的管电压、管电流(m As)对水模反复扫描,探索最适腹部低剂量图像的扫描条件。方法将碘剂、生理盐水按比例配制成实验水模,固定于CT质量确认模上,置于扫描床中心。选择人体腹部扫描条件,固定扫描条件(层厚、螺距、FOV等)不变,仅改变m As或管电压,对配有不同碘浓度的七只试管进行扫描,测量CT图像的一定感兴趣区(ROI)的CT值(x珋±SD,SD表示噪声值),计算得出SNR,并将常规扫描得到的CT值、图像噪声、SNR与改变扫描条件后的进行比较。观察不同管电压、管电流对CT值、图像噪声值及SNR的影响。结果 1)管电压为120k V时,管电流降到60m As时,图像质量明显下降,达不到临床诊断标准;管电压为100k V,管电流降到120m As时,图像质量明显下降,达不到临床诊断标准;管电压为80k V,管电流为200m As或低于200m As时,图像质量达不到临床诊断标准;管电压为70k V,管电流为200m As或低于200m As时,图像质量达不到临床诊断标准;2)CT值、SNR值均随对比剂碘浓度的升高而升高;CT值随电压升高而降低,而电压为100k V时,SNR值最大。结论腹部低剂量检查时,推荐扫描条件100k V,150m As,既能降低辐射剂量,也能得到接近管电压120k V、200m As图像质量的图像。

Objective To get the optimal condition of low dose abdomen scan by using different tube voltage and tube current(mAs)in water model scanning.Methods The iodine and physiological saline were mixed in a proportion and made into experimental water mold.All of the molds were fixed on the quality confirmation mold and placed In the center of the scanning bed.We selected and fixed the normal scanning condition of human abdomen scan(thickness,pitch,FOV,etc.),only changed the mAs and the tube voltage.We scaned the seven test tubes with different iodine concentrations,measured the CT values of certain ROI in the CT images.The SNRs were calculated.We compared the CT values,SNR,image noise value with normal scanning condition and those with different tube,mAs,and observed the effects of CT value,image noise value and SNR with different tube voltage,mAs.Results 1)In the case that Tube voltage was 120 kV,the tube current was down to 60 mAs,the image quality decreased significantly,the Tube voltage was 100 kV,the tube current was down to 120 mAs,the image quality decreased significantly,the Tube voltage was 80 kV,tube current was 200 mAs or lower than 200 mAs,the Tube voltage was 70 kV,tube current was 200 mAs or lower than 200 mAs,the image quality failed to meet the clinical diagnostic criteria;2)CT and SNR value both increased with the increase of the contrast agent iodine concentration.The CT value increased with the decrease of the tube voltage.When the Tube voltage was 100 kV,the SNR value was the largest.Conclusion As for low-dose abdominal scan,the recommended scanning conditions is 100 kV,150 mAs,which can reduce the radiation dose and get the image with quality close to that with the condition of tube voltage 120 kV,tube current 200mAs at the same time.