多层螺旋CT低剂量扫描对肺及气道相关定量评价研究

目的 探讨多层螺旋CT低剂量扫描检查对肺和气道定量评价的可靠性.方法 采用多层螺旋CT机,初诊时对52例患者胸部用250 mA常规剂量扫描,复诊时分三组,分别为17例、17例及18例,分别用100 mA、50 mA和25 mA管电流进行胸部低剂量扫描;测量剂量长度乘积(DLP)、平均肺密度、肺容积及体素指数.将68例患者分为四组,每组17例分别采用250 mA、100 mA、50 mA和25 mA管电流进行全肺扫描,由3位医师对右肺上叶尖段支气管横断面影像进行评分,并进行比较.结果 随着管电流的降低,辐射剂量随之下降,对于平均肺密度和肺容积测量不产生影响,但对于体素指数的测量则产生影响,100 mA、50 mA、25 mA与250 mA时相较测得的体素指数均较高,但各组之间呈良好的正相关,r值范围0.938-0.996,均P<0.00l;管电流为100mA、50mA时支气管评分与250mA时无差别,再降低则支气管评分出现差别,评分减低,但管电流使用50 mA以上时,评分均在3分以上,可以满足对支气管的评价.结论 电流下降时,辐射剂量明显减少,低管电流扫描可用于肺测量,但支气管评价时,管电流宜用50 mA以上.

Study of low-dose multislice CT scan in lung and air-way quantitative estimate

Objective To study the reliability of low-dose multislice CT scan in lung measurement and airway estimate. Methods 52 patients were performed MSCT（GE ,LightSpeed 16） scan using tube current 250 mA. When they were reexamined, they were divided into three groups, and were checked using tube current 100 mA, 50 mA and 25 mA respectively. The dose length products（DLP） ,mean lung density,lung capability and voxel index （VI） were measured severally and compared respectively. 68 patients were divided into four groups, and were performed MSCT（GE, LightSpeed 16） scan using tube current 200 mA, 100 mA, 50 mA and 25 mA, respectively. The imaging quality of bronchus was evaluated by three radiologists at the level of right upper lobe and scores were measured. Results With the descending of the tube current, the radiation dose became direct proportion decline. There was no effect in measurement of the mean lung density and lung capacity. But the measurement of VI was effected. Although the VIs obtained by 100 mA,50 mA and 25 mA were higher than that by 250 mA,but there were high relativity between 100 mA group, 50 mA group, 25 mA group and 250 mA group, respectively. For bronchus score,there was no difference in I00 mA/250 mA groups,50 mA/250 mA groups,and 50 mA/100 mA groups. But the bronchus scores of 25 mA group was lower than that of 250 mA, 100 mA and 50 mA groups. And the score was more than 3 when the tube current was not less than 50 mA. Conclusions Low tube current CT scan could be used for measurements of lung and the tube current for evaluation of bronchus was not less than 50 mA.