Yanagawa Noriyuki, Kawata Naoko, Matsuura Yukiko, Sugiura Toshihiko, Suzuki Toshio, Kasai Hajime, Irie Ryosuke, Iesato Ken, Tada Yuji, Tanabe Nobuhiro, Suzuki Yoichi, Tatsumi Koichiro
Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan.
Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan
Acta Radiol. 2015 Apr;56(4):438-46. doi: 10.1177/0284185114528489. Epub 2014 Mar 14.
The estimation of emphysematous changes is very sensitive to computed tomography (CT) threshold level. In clinical practice, the predetermined threshold is usually set at -950 Hounsfield units (HU) for the detection of low attenuation volume (LAV). However, threshold levels that are tightly connected to pulmonary function abnormalities have not been determined.
To determine the threshold level for calculating an LAV that closely reflects airflow limitation in patients with chronic obstructive pulmonary disease (COPD).
Seventy-six consecutive non-COPD smokers and COPD patients underwent paired inspiratory and expiratory multidetector CT (MDCT). LAV% was segmented every 10 HU between -1000 and -750 HU to examine the correlation between LAV% and indexes of obstructive impairment.
LAV% gradually increased as the threshold level increased on both inspiratory and expiratory images. LAV% on inspiratory images was higher than that on expiratory images at all threshold levels between -1000 and -750 HU. The threshold level that correlated with obstructive impairment differed between the two images: -930 HU on inspiratory and -870 or -880 HU on expiratory images.
LAV% dramatically changed according to the threshold level on both inspiratory and expiratory images, indicating that LAV% is dependent on the attenuation threshold level in patients with COPD. The threshold linking LAV% to airflow limitation was higher on expiratory than on inspiratory images.
肺气肿变化的评估对计算机断层扫描（CT）阈值水平非常敏感。在临床实践中，通常将预定阈值设定为-950亨氏单位（HU）以检测低衰减体积（LAV）。然而，与肺功能异常紧密相关的阈值水平尚未确定。
确定计算LAV的阈值水平，该阈值能密切反映慢性阻塞性肺疾病（COPD）患者的气流受限情况。
76例连续的非COPD吸烟者和COPD患者接受了吸气和呼气配对的多排螺旋CT（MDCT）检查。在-1000至-750 HU之间每隔10 HU对LAV%进行分割，以检查LAV%与阻塞性损伤指标之间的相关性。
在吸气和呼气图像上，随着阈值水平的升高，LAV%逐渐增加。在-1000至-750 HU之间的所有阈值水平下，吸气图像上的LAV%均高于呼气图像上的LAV%。与阻塞性损伤相关的阈值水平在两种图像之间有所不同：吸气图像上为-930 HU，呼气图像上为-870或-880 HU。
在吸气和呼气图像上，LAV%均根据阈值水平发生显著变化，这表明在COPD患者中LAV%依赖于衰减阈值水平。与气流受限相关的LAV%的阈值在呼气图像上高于吸气图像。
