摘要
目的在64层MSCT冠状动脉成像中，通过对定位像CT值与管电流关系的研究，探讨其对不同个体实施个性化剂量管理的指导价值。方法（1）连续选取100例（A组）患者完成心脏扫描，测量胸部定位像中固定R01的CT值和主动脉根部噪声，使用软件拟合CT值与噪声的关系，得到管电流与CT值的换算公式及速查表。（2）再连续选取100例（B组）患者，以相同方法测量CT值，根据管电流与CT值的速查表确定扫描时mA值，其他扫描参数2组一致。（3）分别对A、B组图像质量评分、图像噪声、有效剂量（ED）均值进行t检验。（4）分析B组32例同期行选择性冠状动脉造影（SCA）的资料，以SCA结果为“金标准”，计算B组诊断冠状动脉狭窄度的敏感性、特异性、阳性预测值、阴性预测值及准确率。结果（1）管电流与CT值换算公式为：XmA=FmA×[（K1×CTscout＋C1）／INa]^2。（2）B组噪声均值略高于A组（分别为27．66±2．57和22．22±4．17，t=11．33，P=0．000），但2组图像质量评分[分别为（3．29±0．66）和（3．37±0．67）分]差异无统计学意义（t=0．009，P=0．990），ED均值分别为（8．72±2．51）和（12．53±0．90）mSy，B组较A组下降约30％（t=14．830，P〈0．01）。（3）B组评价冠状动脉狭窄（〉／50％狭窄）的敏感性、特异性、阳性预潍值以及阴性预测值分别为94．92％（56／59）、92．13％（82／89）、88．89％（56／63）和96．47％（82／85）。对冠状动脉狭窄的检出准确率为93．24％（138／148）。结论在64层MSCT冠状动脉成像时，根据定位像CT值确定个性化管电流，可在保证图像质量满足诊断需求的前提下，更科学合理地控制X线剂量。
Objective To characterize the association between the mean CT value on a scout view and the dependent mA selection method, and to evaluate the clinical value of amA selection method based on scout view mean CT value in obtaining individualized scan protocol and consistent image quality for patient population on 64-row MSCT CT coronary angiography （CTCA）. Methods One hundred patients （ group A） underwent CCTA consecutively using standard protocol with a fixed rnA. The mean CT value of a fixed ROI （region of interest） from the scout AP view and the CTCA image noise （standard deviation on the root of ascending aorta ） were measured. The correlation between CT values and noise was studied to establish a formula and a list to determine the required mA for obtaining a consistent CTCA image noise based on the measured SV CT value. Another 100 patients （group B） were scanned using the same parameters as group A except the mA and the CT value was also measured. The mA was determined by the list established previously. The CTCA image quality （IQ） as well as the image noise （IN） and the effective dose （ED） from the two groups were statistically analyzed using t-test. The CT findings for the 32 patients in the group B were also compared with the selective coronary angiography （SCA） results. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of CCTA for detection of significant stenosis were obtained. Results The formula between the required mA and the CT value was ： XmA = FmA × [ （ K1× CTscout ＋ C1 ）/INa]2. The CCTA images in B group had statistically higher IN （27.66 ±2. 57,22.22±4. 17,t = 11. 33, P = 0. 000）, but no statistical difference between IQ scores for the two groups （3.29 ±0.66,3.37 ±0.67,t =0.009, P=0.990）, and ED [（8.72 ±2.51） versus （ 12. 53±0. 90） mSv] was 30% lower for the B group （P 〈0. 01 ）. For the 32 patients in the B group who had SCA, the CCTA sensitivity, specificity, positive predictive value, negative predictive value, and stenosis detection accuracy were 94. 92% （ 56/59 ）, 92. 13 % （ 82/89 ）, 88. 89 % （ 56/63 ） ,96.47% （ 82/85 ） and 93.24% （ 138/148 ） respectively for stenosis greater than 50%. Conclusion The mA selection method based on the SV CT value for CCTA in 64-row MSCT provides individualized protocol to obtain consistent image quality and to optimize dose delivery to patients.
出处
《中华放射学杂志》
CAS
CSCD
北大核心
2009年第7期719-724,共6页
Chinese Journal of Radiology
