CARE Dose 4D技术降低成人胸部扫描剂量的临床价值

Clinical value of CARE Dose 4D technique in decreasing CT scanning dose of adult chest

目的探讨CAREDose4D技术在成人胸部CT扫描中降低辐射剂量及提高图像质量价值。方法选取胸部CT扫描病例100例，随机分为低剂量组及对照组各50例，低剂量组使用CAREDose4D技术。记录每位患者胸部扫描时自动显示的有效毫安秒（mAs）、容积CT剂量指数（CTDIvel）及剂量长度乘积（DLP）和每幅图像上的mAs值。取每例患者肺尖部、主动脉弓下缘水平、左房中部水平及肺底部4幅图像，共400幅。由两位副主任医师按优、良、差3级双盲法评判，测量相应部位图像噪声。结果在设置质量参考80mAs时，低剂量组比对照组最大下降44mAs，平均下降9．60mAs（12．0％）；CTDIvel值最大下降4．75mGy，平均下降0．95mGy（11．0％）；DLP值平均下降14．88mGy·cm（7．5％）。图像主观评判低剂量组平均优良率为99．5％，对照组为98．0％；肺尖及肺底水平低剂量组高于对照组，左房中部水平低于对照组，主动脉弓下缘水平两组相近。图像噪声测量结果显示低剂量组肺尖及肺底部低于对照组（t=6．299、2．332，P〈0．05），左房中部水平高于对照组（t=3．078，P〈0．05），主动脉弓下缘水平两组相似（t=1．191，P〉0．05）。结论CAREDose4D技术具有实时在线调节mAs作用，既可提高射线利用效率、降低辐射剂量，又能提高图像质量，在胸部CT扫描中具有一定临床应用价值。

Objective To investigate the value of CARE Dose 4D technique in decreasing radiation dose and improving image quality of multi-slice spiral CT in adult chest scanning. Methods 100 patients of chest CT scanning were equally divided into study group and control group randomly. CARE Dose 4D Technique was used in study group. Effective mAs value, volume CT dose index （CTDIvol） and close length product （DLP） were displayed automatically in machine while chest scanning; those values and actual mAs value of every image were recorded respectively. The image quality at apex of lung, lower edge of aorta arch, middle area of left atrium and base of lung on every image of 400 images was judged and classified as three level （excellent, good, poor） by two deputy chief physicians with double blind method, the image noise at corresponding parts was measured. Results While setting 80 mAs for quality reference mAs, the effective mAs value in study group most decreased 44 mAs than control group with an average decrease of 9.60（ 12.0% ）, CTDIvo~ with 4. 75 mGy with an average decrease of O. 95 mGy（ 11.0% ）, DLP with an average of 14.88 mGy ~ cm （7.5%）. In subjective judgment of image, the average fine rate was 99.50% in study group, with 98.0% in control group. But it was higher at apex of lung and base of lung, lower at middle area of left atrium, and similar at lower edge of aorta arch in study group than contrast group. The image noise were lower at apex of lung and base of lung in study group than control group （t = 6. 299 and 2. 332,all P 〈 0.05 ） , higher at middle area of left atrium in study group than control group （t = 3. 078,P 〈0. 05） and similar at lower edge of aorta arch in study group than control group （t = 1. 191, P 〉 0.05）. Conclusions CARE Dose 4D technique provides a function regulated mAs real-time on line, it not only raises utilization rate of radiation and decreases radiation dose, but also promises and increases image quality in chest CT scanning, and has some clinical significance.