Evaluation of low attenliation area (LAA) of the lungs in patients with reversible airway obstruction by high resolution computed tomography (HRCT).

The significance of the low attenuation area (LAA) of the lungs on high resolution computed tomography (HRCT) has not been determined in patients with asthma. We examined the relationship between the percentage of lung area with CT numbers lower than -950HU (% LAA) and the mean CT number in 81 patients with reversible airway obstruction (asthma) and in 22 healthy subjects, as well as the relationship between maximal % LAA and various parameters of pulmonary function, smoking history, disease severity and allergic type in the asthmatic subjects. The mean CT number was obtained by scans at three anatomic levels, and maximal % LAA was the % LAA which had the largest value of those measured at the three anatomic levels of the lung. We found that: 1. The mean CT number was closely related to the maximal % LAA of the lungs in all subjects studied (r= -0.916, p

【目的】気管支喘息症例において胸部HRCTを用いて% LAA(Lowattenuationarea)を評価し,臨床病態との関連を検討する｡ 【対象と方法】気管支喘息症例81例ならびに健常者22例を対象とした｡大動脈弓部,下葉分岐部,横隔膜上3cmの3スライスを撮影し,胸部CT値の演算によりCT値が-950HU以下の% LAA,さらに3スライス中の最大% LAAと3スライスの平均CT値を算出した｡その値と年齢,発症年齢,罹病期間,性別,喫煙歴,重症度,病型,肺機能との関連を検討した｡【結果】1.最大% LAAは平均CT値と強い相関を示した(r=-0.916,p<0.0001)。2.最大% LAAは喫煙喘息患者において非喫煙喘息患者,喫煙ならびに非喫煙健常者に比較して喫煙者において有意に高値を示した｡% LAAは喫煙者,非喫煙者ともに重症例において有意に高値を示した｡3.最大% LAAは肺機能では1秒率(r=-0.611,p<0.0001),全肺気量(r=-0.391,p<0.0001)と有意な相関を示した｡4.最大% LAAは喘息の重症度とは有意の竿間を示したが,病型とは関連は見られなかった｡ 【考案】喘息患者におけるHRCTによる最大% LAAは喫煙,重症度,肺機能と関連を示しており,気管支喘息の臨床病態を反映する可能性が示唆された｡