Oguma Tsuyoshi, Niimi Akio, Hirai Toyohiro, Jinnai Makiko, Matsumoto Hisako, Ito Isao, Yamaguchi Masafumi, Matsuoka Hirofumi, Otsuka Kojiro, Takeda Tomoshi, Nakaji Hitoshi, Chin Kazuo, Mishima Michiaki
Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Respiration. 2015;89(6):539-49. doi: 10.1159/000381553. Epub 2015 Apr 30.
Computed tomography (CT) assessment of air trapping has been considered useful as a measure of small airway disease. Mean lung density (MLD) and the percentage of the lung field occupied by low attenuation area (LAA%) can be evaluated automatically, and their expiratory/inspiratory (E/I) ratios correlate with asthma severity and spirometry parameters. However, mosaic attenuation, another indicator of air trapping, has been assessed visually, and its functional relevance remains controversial.
This retrospective study was conducted to correlate mosaic attenuation, which was assessed visually and automatically, and the E/I ratios of MLD and LAA% (defined as areas <-960 Hounsfield units) with clinical and physiological variables, including impulse oscillometry (IOS) indices.
In 36 nonsmoking patients with stable asthma, the lungs were scanned at full inspiration and full expiration. Mosaic attenuation was measured visually and automatically, by counting areas with CT values higher than the surrounding areas. MLD and LAA% were measured using our validated method. Spirometry, IOS, exhaled NO and the sputum eosinophil count were evaluated.
The automatic results and visual scores of mosaic attenuation correlated well on expiratory scans (r = 0.894) and to a lesser degree on inspiratory scans (r = 0.629; p < 0.0001 for both). However, only the E/I ratios of MLD and LAA% correlated with forced expiratory volume in 1 s/forced vital capacity of spirometry and the IOS indices of resistance from 5 to 20 Hz and the integrated area of low-frequency reactance.
Our automatic method for analysis of mosaic attenuation is likely useful, but the results themselves may not be reflecting small airway involvement of asthma, unlike the E/I ratios of MLD and LAA%.
计算机断层扫描（CT）对空气潴留的评估被认为是衡量小气道疾病的有用方法。平均肺密度（MLD）和低衰减区域（LAA%）占肺野的百分比可自动评估，其呼气/吸气（E/I）比值与哮喘严重程度和肺量计参数相关。然而，空气潴留的另一个指标——马赛克样衰减，一直是通过视觉评估的，其功能相关性仍存在争议。
本回顾性研究旨在将通过视觉和自动评估的马赛克样衰减以及MLD和LAA%（定义为低于-960亨氏单位的区域）的E/I比值与包括脉冲振荡法（IOS）指标在内的临床和生理变量相关联。
对36例稳定期哮喘的非吸烟患者在深吸气和深呼气时进行肺部扫描。通过计算CT值高于周围区域的面积，对马赛克样衰减进行视觉和自动测量。使用我们验证过的方法测量MLD和LAA%。评估肺量计、IOS、呼出一氧化氮和痰液嗜酸性粒细胞计数。
呼气扫描时，马赛克样衰减的自动结果与视觉评分相关性良好（r = 0.894），吸气扫描时相关性稍弱（r = 0.629；两者p均<0.0001）。然而，只有MLD和LAA%的E/I比值与肺量计的1秒用力呼气量/用力肺活量以及5至20 Hz的IOS阻力指标和低频电抗积分面积相关。
我们用于分析马赛克样衰减的自动方法可能有用，但与MLD和LAA%的E/I比值不同，其结果本身可能无法反映哮喘的小气道受累情况。
