Matsuoka Shin, Kurihara Yasuyuki, Yagihashi Kunihiro, Hoshino Makoto, Watanabe Naoto, Nakajima Yasuo
Department of Radiology, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-Ku, Kawasaki City, Kanagawa 216-8511, Japan.
AJR Am J Roentgenol. 2008 Mar;190(3):762-9. doi: 10.2214/AJR.07.2820.
The purpose of our study was to determine the attenuation threshold value for the detection and quantification of air trapping using paired inspiratory and expiratory volumetric MDCT scans and to assess whether the densitometric parameter can be used for the quantification of airway dysfunction in chronic obstructive pulmonary disease (COPD) regardless of the degree of emphysema.
This study included 36 patients with COPD who underwent 64-MDCT. The entire lung volume with attenuation between -500 and -1,024 H was segmented as whole lung. The lung volume with attenuation between -500 and -950 H was segmented as limited lung, while the lung volume of less than -950 H was segmented as emphysema and eliminated. The relative volumes for limited lung (relative volume(n-950)) with attenuation values below thresholds (n) ranging from -850 to -950 H, and relative volume for whole lung (relative volume(<n)) were obtained on inspiratory and expiratory CT. Then the differences of relative volumes after expiration in whole lung (relative volume change(<n)) and limited lung (relative volume change(n-950)) were calculated. Patients were classified into two groups according to mean relative volume less than -950 H. Correlations between densitometry parameters and pulmonary function tests (PFTs) reflecting airway dysfunction were evaluated.
The highest correlation with PFTs was observed at the upper threshold of -860 H. In the moderate to severe emphysema group (relative volume(<-950) > 15%), relative volume change(860-950) significantly correlated with the results of PFTs, whereas no significant correlations were seen between relative volume change(<-860) and PFTs. In the minimal or mild emphysema group (inspiratory relative volume(<-950) < 15%), all densitometric parameters correlated with PFTs.
The densitometric parameter of relative volume change calculated on paired inspiratory and expiratory MDCT using the threshold of -860 H in limited lung correlated closely with airway dysfunction in COPD regardless of the degree of emphysema.
我们研究的目的是通过配对的吸气和呼气容积MDCT扫描确定检测和定量空气潴留的衰减阈值，并评估密度测定参数是否可用于慢性阻塞性肺疾病（COPD）气道功能障碍的定量分析，而不考虑肺气肿的程度。
本研究纳入36例接受64层MDCT检查的COPD患者。将衰减值在-500至-1024 H之间的整个肺容积分割为全肺。将衰减值在-500至-950 H之间的肺容积分割为受限肺，而衰减值小于-950 H的肺容积分割为肺气肿并予以排除。在吸气和呼气CT上获取衰减值低于-850至-950 H阈值（n）的受限肺相对容积（相对容积（n-950））和全肺相对容积（相对容积（<n））。然后计算全肺（相对容积变化（<n））和受限肺（相对容积变化（n-950））呼气后相对容积的差异。根据平均相对容积小于-950 H将患者分为两组。评估反映气道功能障碍的密度测定参数与肺功能测试（PFT）之间的相关性。
在-860 H的上阈值处观察到与PFT的最高相关性。在中度至重度肺气肿组（相对容积（<-950）>15%）中，相对容积变化（860-950）与PFT结果显著相关，而相对容积变化（<-860）与PFT之间未观察到显著相关性。在轻度或轻度肺气肿组（吸气相对容积（<-950）<15%）中，所有密度测定参数均与PFT相关。
在受限肺中使用-860 H阈值通过配对吸气和呼气MDCT计算的相对容积变化密度测定参数与COPD患者的气道功能障碍密切相关，而不考虑肺气肿的程度。
