Repeatability and Sample Size Assessment Associated with Computed Tomography-Based Lung Density Metrics
Repeatability and Sample Size Assessment Associated with Computed Tomography-Based Lung Density Metrics
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DOI：
10.15326/jcopdf.1.1.2014.0111
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发表时间：
2014-05-01
影响因子：
2.4
通讯作者：
Hoffman, Eric A.
中科院分区：
文献类型：
--
作者：
Iyer, Krishna S.;Grout, Randall W.;Hoffman, Eric A.
原理和目的：基于密度的指标评估肺部疾病的严重程度，但随肺部充气和扫描方法而变化。本研究的目的是评价单中心、基于计算机断层扫描（CT）的肺密度指标在正常人群中的可重复性，并评估当扫描参数和体积受到严格控制时检测肺密度指标的有意义变化所需的研究样本量。材料和方法：37名参与者（正常吸烟者和非吸烟者）同意随机分配重复的屏气扫描，（90%肺活量：总肺活量[TLC]）或呼气（20%肺活量：功能性残气量[FRC]）。分析重复扫描的：平均肺密度（MLD）、密度直方图的第15百分位点（P-15）、低衰减区域（LAA）和α（孔径分布的分形测量）。使用参与者之间的差异和先前报告的偏倚，从已发表文献中获得的密度指标变化（即有意义的变化）估计样本量。结果：密度指标的扫描间差异测量值较小（ICC > 0.80），全肺α-910和α-950的平均类内相关系数（ICC）分别为0.57和0.64。功率分析表明，在控制条件下，具有最小的外在变化，人口规模需要检测有意义的变化，TLC或FRC重复扫描的密度措施，范围从几个（20-40）到几百个participants，respectively.Conclusion：一个有意义的样本量预测本研究使用体积控制的正常参与者在一个受控的成像环境。在适当的屏气条件下，在正常吸烟者和非吸烟者的队列中获得了高重复性。
Rationale and Objectives: Density-based metrics assess severity of lung disease but vary with lung inflation and method of scanning. The aim of this study was to evaluate the repeatability of single center, computed tomography (CT)-based density metrics of the lung in a normal population and assess study sample sizes needed to detect meaningful changes in lung density metrics when scan parameters and volumes are tightly controlled.Materials and Methods: Thirty-seven participants (normal smokers and non-smokers) gave consent to have randomly assigned repeated, breath-held scans at either inspiration (90% vital capacity: total lung capacity [TLC]) or expiration (20% vital capacity: functional residual capacity [FRC]). Repeated scans were analyzed for: mean lung density (MLD), 15th percentile point of the density histogram (P-15), low attenuation areas (LAA) and alpha (fractal measure of hole size distribution). Using inter-participant differences and previously reported bias, sample size was estimated from change in density metrics obtained from published literature (i.e. meaningful change).Results: Inter-scan difference measurements were small for density metrics (ICC > 0.80) and average intra-class correlation coefficients (ICC) for whole lung alpha-910 and alpha-950 were 0.57 and 0.64, respectively. Power analyses demonstrated that, under the control conditions with minimal extrinsic variation, population sizes needed to detect meaningful changes in density measures for TLC or FRC repeated scans ranged from a few (20-40) to a few hundred participants, respectively.Conclusion: A meaningful sample size was predicted from this study using volume-controlled normal participants in a controlled imaging environment. Under proper breath-hold conditions, high repeatability was obtained in cohorts of normal smokers and non-smokers.