Marsh Suzanne, Aldington Sarah, Williams Mathew V, Nowitz Michael R, Kingzett-Taylor Andrew, Weatherall Mark, Shirtcliffe Philippa M, McNaughton Amanda A, Pritchard Alison, Beasley Richard
Medical Research Institute of New Zealand, P.O. Box 10055, Wellington, New Zealand.
Respir Med. 2007 Jul;101(7):1512-20. doi: 10.1016/j.rmed.2007.01.002. Epub 2007 Feb 20.
The role of computerised tomography (CT) lung density measurements in objective quantification of emphysema is uncertain. The aim of this study was to determine normal reference values for CT lung density measurements and investigate their utility in identifying subjects with clinical emphysema.
Normal subjects (non-smokers, no respiratory disease, n=185) and subjects with clinical emphysema (post-bronchodilator FEV(1)/FVC <70%, > or =10 pack years tobacco smoking, no childhood asthma and, either D(LCO)/VA <80% predicted and/or macroscopic emphysema on CT, n=22) were identified from a random population survey. Subjects underwent CT scanning, with measurement of areas of low attenuation as a percentage of total area (RA%) for three standardised slices and two reconstruction algorithms with a density threshold of -950 HU. Reference values in normal subjects, and ability of the measurements to discriminate between the two groups were determined.
Reference values for individual subjects showed wide confidence intervals (standard resolution scans, RA% females 0.2-3.9%, males 0.4-8.7%.) Subjects with emphysema had greater RA% values compared with normal subjects, the difference being most marked in apical slices (standard resolution algorithm, apical slice, median RA% 2.9% (95% CI 0.4-11.1%) vs. 0.1% (95% CI 0.0-0.5%), emphysema vs. normal subjects, respectively). Logistic regression analysis showed poor discriminant ability to distinguish between the groups, the most favourable cut-off yielding a sensitivity and specificity of 83.3% and 62.8%, respectively.
CT lung density measurements cannot reliably detect the presence of emphysema in an individual. We recommend further investigation into lung density measurements before their widespread use in clinical practice.
计算机断层扫描（CT）肺密度测量在肺气肿客观量化中的作用尚不确定。本研究的目的是确定CT肺密度测量的正常参考值，并研究其在识别临床肺气肿患者中的效用。
从一项随机人群调查中确定正常受试者（非吸烟者，无呼吸系统疾病，n = 185）和临床肺气肿患者（支气管扩张剂后FEV(1)/FVC < 70%，吸烟史≥10包年，无儿童哮喘，且CT显示D(LCO)/VA < 预测值的80%和/或存在宏观肺气肿，n = 22）。受试者接受CT扫描，对三个标准化层面使用两种重建算法，以-950 HU的密度阈值测量低衰减区域占总面积的百分比（RA%）。确定正常受试者的参考值，以及测量值区分两组的能力。
个体受试者的参考值显示出较宽的置信区间（标准分辨率扫描，RA%女性为0.2 - 3.9%，男性为0.4 - 8.7%）。肺气肿患者与正常受试者相比，RA%值更高，差异在肺尖层面最为明显（标准分辨率算法，肺尖层面，中位数RA%分别为2.9%（95%CI 0.4 - 11.1%）和0.1%（95%CI 0.0 - 0.5%），肺气肿患者与正常受试者）。逻辑回归分析显示区分两组能力较差，最有利的截断值产生的敏感性和特异性分别为83.3%和62.8%。
CT肺密度测量不能可靠地检测个体中肺气肿的存在。我们建议在临床实践中广泛应用肺密度测量之前进行进一步研究。
