低剂量CT对肺小结节大小定量测量影响的体模研究

Repeatability of small lung nodule measurement in low-dose CT:a phantom study

目的:利用体模,研究不同的管电流和管电压组合的低剂量扫描对肺小结节大小测量一致性的影响。方法:采用胸部体模,分别扫描8个直径为3 mm、5 mm、8 mm、10 mm的磨玻璃结节和实性结节,采用不同管电压(kV)和管电流(m A)组合扫描方案。4种管电压分别为:70 kV、80 kV、100 kV、120 kV。9种管电流分别为:20 mAs、30 mAs、40 mAs、50 mAs、60 mAs、70 mAs、80 mAs、90 mAs、100 m As。使用工作站测量不同扫描组合结节的平均直径和体积。所有实验数据均采用SPSS 21.0进行统计学分析处理。结果:与常规剂量组(120 kVp、100 mAs)比较,所有扫描组合测得的结节直径和实性结节体积均有较好的一致性,P均>0.05;与常规剂量组(120 kVp、100 mAs)比较,测得10 mm(GGNs)(F=48.555、P=0.000)中(80 kVp、50 mAs)组合(P=0.109)及以上组合的体积P均>0.05,无统计学差异;测得8 mm(GGNs)(F=55.645、P=0.000)中(80 kVp、70 mAs)组合(P=0.205)及以上组合的体积P均>0.05,无统计学差异;测得5 mm(GGNs)(F=30.539、P=0.000)中(80 kVp、70 mAs)组合(P=0.138)及以上组合的体积P均>0.05,无统计学差异;测得3 mm(GGNs)(F=28.183、P=0.000)中(80 kVp、80 mAs)组合(P=0.191)及以上组合的体积P均>0.05,无统计学差异。结论:肺癌筛查实验中应选择超过80 kVp、80 mAs的扫描组合才能同时满足肺小结节直径和体积准确测量的要求。

Objectives:The aim of this phantom study was to investigate whether images captured with low dose computed tomography(CT)in different tube voltages and tube current scan could improve the repeatability of small nodule measurement,and whether this approach could further reduce the radiation dose of CT while maintaining its measurement repeatability.Methods:An anthropomorphic chest phantom containing artificial solid and ground glass nodules(GGNs,3~10 mm)was examined with a multi-detector CT scanner with nine tube currents of 20,30,40,50,60,70,80,90,100 mAs in combination with four tube voltages of 70,80,100 and 120 kVp.The average diameter and volume of all nodules were measured by using a commercially-available computer-aided detection(CAD)system on a workstation.Statistical analysis was performed using commercially available software(SPSS 21.0).Results:Compared to the standard CT(120 kVp,100 mAs),the average diameter of all nodules and volume of all solid nodules had no difference(P>0.05).Compared to the standard CT(120 kVp,100 m As),volume of GGNs(10 mm)with more than 80 kVp,50 mAs had no difference(F=48.555,P=0.000,P=0.109);volume of GGNs(8 mm)with more than 80 kVp,70 mAs had no difference(F=55.645,P=0.000,P=0.205);volume of GGNs(5 mm)with more than 80 kVp,70 mAs had no difference(F=30.539,P=0.000,P=0.138);volume of GGNs(3 mm)with more than 80 kVp,80 mAs had no difference(F=28.183,P=0.000,P=0.191).Conclusions:Our results suggest a CT protocol with more than 80 mAs and 80 kVp is optimal for measurement of small nodules in lung cancer screening.