多层螺旋CT胸部低剂量扫描发现肺结节的临床研究

The experimental study and clinical application on the detection of pulmonary nodules with low-dose multislice spiral CT

目的 研究降低电流对发现肺结节 ,尤其是直径≤ 5mm结节的影响 ,并观察低剂量CT在胸部初步应用的影像效果。方法 对 6例病理证实为肺内多发结节的尸检离体肺脏制成充气固定的肺标本 ,分别行多层螺旋CT的常规剂量 (130mA)和低剂量CT(5 0、30、10mA)扫描。对 4 0例体检者和 6 0例转移瘤近期复查的患者行低剂量CT(30mA)扫描。记录直径≤ 5mm的结节的数目并判断影像有无伪影。根据诊断的把握度将结节分为肯定是结节、不能确定和肯定不是结节。对 4 0例体检者及 6 0例转移瘤仅评价影像的伪影情况。结果 肺标本研究中 ,低剂量各组 (5 0、30、10mA)的Kappa值为 0 5 15、0 2 4 2、0 15 4。经U检验 ,低剂量 5 0mA组与常规剂量组结节的发现一致性较好。 5 0、30、10mA组的敏感度分别为 88 0 %、78 4 %、75 0 % ,阳性预测值分别为 98%、94 %、93% ,准确度分别为85 %、73%、6 9%。标本影像仅在 10mA组中 2 1幅 (70 % ,2 1/ 31)图像的椎体旁的肺区见到细小条状伪影。 10 0例病人的影像中仅在 3例的肺尖可见到能影响小结节发现的条状伪影。结论 低剂量CT有望提高肺癌的早期发现。低剂量 5 0mA组对直径≤ 5mm的结节能可靠发现。研究显示 30mA可得到满意的影像质量。有条件者应开展低剂量CT筛查肺癌。

Objective To investigate the detection rate of pulmonary nodules,especially nodules ≤5 mm,in variable low-doses,and to evaluate the imaging quality of low-dose MSCT.Methods Six postmortem specimens of patients with pneumoconiosis after necropsy were fixed at end-inspiratory volume.The fixed specimens were examined by using MSCT with standard dose (130 mA) and low-dose (50,30,10 mA,respectively).Low-dose MSCT scans of 40 asymptomatic volunteers and 60 patients with pulmonary metastasis were also examined with 30 mA.The numbers of pulmonary nodules less than 5 mm at standard-dose and different low-dose were recorded.Nodules were assessed by diagnostic confidence (“definite nodule”,“questionable nodule',and “definite not nodule').The number of images with artifact in specimens and in 40 volunteers and 60 patients with pulmonary metastasis were recorded.Results In specimen′s study,the Kappa values of groups of low-dose (50,30,10 mA) were 0.515,0.242,and 0.154,respectively.The group of 50 mA had a good coincidence with standard-dose group by U test.The sensitivity of group 50,30,10 mA was 88.0%,78.4%,and 75.0%,respectively.The positive predictive values of which were 98%,94%,and 93%,respectively.The correction rates of which were 85%,73%,and 69%,respectively.In specimens′ images,subtle linear artifact was showed only in paravertebral lung field in 21 images of 31 at the group of 10 mA.Linear artifacts that affected small nodule detection were showed in lung apexes in 3 of 100 subjects.Conclusion Low-dose MSCT is expected to improve early detection of lung cancer.Pulmonary nodules less than 5 mm could be reliably detected at 50 mA tube current in specimens.Low-dose CT (30 mA) showed satisfactory imaging quality in our study.Low-dose CT screening for lung cancer may be applied if situation permits.