Lamers R J, Kemerink G J, Drent M, van Engelshoven J M
Dept of Radiology, University Hospital Maastricht, The Netherlands.
Eur Respir J. 1998 Apr;11(4):942-5. doi: 10.1183/09031936.98.11040942.
The aim of this study was to assess the reproducibility of quantitative, spirometrically gated computed tomographic (CT) lung densitometry at defined levels of inspiration in hospitalized patients. On two consecutive days, spirometrically gated CT sections were obtained from 20 hospitalized patients at 5 cm above and 5 cm below the carina, and at 90 and 10% of the vital capacity (VC). The mean, modal and median lung densities were calculated, the cut-off points of the frequency distribution of Hounsfield units (HU) defining the lowest and the highest 10th percentile, as well as the histogram full width at half maximum. The lung density parameters of corresponding CT sections of both studies were compared. Reproducibility was expressed as the standard deviation of the signed difference between the results of Day 1 and Day 2 divided by the square root of 2. Reproducibility data were correlated with results of airflow limitation. At 90% VC, reproducibility was of the order of 3-14 HU in both lung zones. At 10% VC, reproducibility was worse by approximately a factor of three. No relationship was found between reproducibility and results of airflow limitation. In conclusion, objective measurement of lung density at spirometrically controlled levels of inspiration is a reproducible method in assessing pulmonary density. Reproducibility of lung density measurements is not influenced by severe respiratory insufficiency. The most reproducible computed tomographic lung density measurements can be obtained at 90% vital capacity.
本研究的目的是评估住院患者在特定吸气水平下，定量、肺量计门控计算机断层扫描（CT）肺密度测定的可重复性。连续两天，从20名住院患者的气管隆突上方5 cm、下方5 cm以及肺活量（VC）的90%和10%水平处获取肺量计门控CT图像。计算平均、众数和中位数肺密度，确定Hounsfield单位（HU）频率分布的截止点，即定义最低和最高第10百分位数，以及直方图半高全宽。比较两项研究中相应CT图像的肺密度参数。可重复性表示为第1天和第2天结果的符号差的标准差除以√2。可重复性数据与气流受限结果相关。在90% VC时，两个肺区的可重复性约为3 - 14 HU。在10% VC时，可重复性约差三倍。未发现可重复性与气流受限结果之间存在关联。总之，在肺量计控制的吸气水平下客观测量肺密度是评估肺密度的一种可重复方法。肺密度测量的可重复性不受严重呼吸功能不全的影响。在肺活量的90%时可获得最可重复的计算机断层扫描肺密度测量结果。
