Im J G, Kim S H, Chung M J, Koo J M, Han M C
Department of Radiology, Seoul National University Hospital, Korea.
J Comput Assist Tomogr. 1996 Sep-Oct;20(5):756-62. doi: 10.1097/00004728-199609000-00013.
Our goal was to analyze patients with pulmonary lobular low attenuation (LLA) on thin section CT with regard to the underlying pulmonary diseases and the dynamic changes occurring in the low attenuation regions during respiration.
Forty-eight consecutive patients with LLA on thin section CT were analyzed retrospectively. Forty-six patients (95%) had symptoms related to respiratory disease, such as productive cough (n = 25) and hemoptysis (n = 18). Only two patients, one with chronic pulmonary embolism and one with Takayasu arteritis combined with bronchiectasis, had pulmonary vascular disease. Six patients, four with bronchiectasis and two with vascular disease, were studied with dynamic CT during forced vital capacity maneuver. Attenuation values for LLA areas and adjacent lung were measured and time-density curves were plotted.
Forty-one (85%) patients had bronchiectasis, typically in other than the regions of the LLA. Areas with proximal bronchiectasis showed low attenuation but without notable lobular distribution. Pulmonary vessels in the LLA areas were smaller than those of adjacent normal lung (n = 45). Of 22 patients who underwent pulmonary function tests, 15 had obstructive pattern of impairment. Respiratory dynamic CT showed expiratory air trapping in LLA areas in all six patients. The mean attenuation values of LLA areas were lower than those of the adjacent normal lung by 67 HU at end-inspiration and by 165 HU at end-expiration (p = 0.002).
The majority of the patients with LLA shown by thin section CT had bronchiectasis elsewhere in the lung, and evidence of air trapping in the LLA was clearly demonstrated. Bronchiolar obstruction may be the most prevalent cause for the development of LLA.
我们的目标是分析薄层CT上出现肺小叶低密度（LLA）的患者的潜在肺部疾病，以及呼吸过程中低密度区域发生的动态变化。
回顾性分析48例薄层CT上出现LLA的连续患者。46例（95%）患者有与呼吸系统疾病相关的症状，如咳痰（n = 25）和咯血（n = 18）。只有2例患者患有肺部血管疾病，1例为慢性肺栓塞，1例为高安动脉炎合并支气管扩张。6例患者，4例患有支气管扩张，2例患有血管疾病，在用力肺活量动作期间进行了动态CT研究。测量LLA区域和相邻肺组织的衰减值，并绘制时间-密度曲线。
41例（85%）患者患有支气管扩张，通常不在LLA区域。近端支气管扩张区域显示低密度，但无明显的小叶分布。LLA区域的肺血管比相邻正常肺组织的肺血管小（n = 45）。在22例接受肺功能测试的患者中，15例有阻塞性损害模式。呼吸动态CT显示所有6例患者的LLA区域均有呼气性气体潴留。LLA区域的平均衰减值在吸气末比相邻正常肺组织低67 HU，在呼气末低165 HU（p = 0.002）。
薄层CT显示LLA的大多数患者在肺部其他部位有支气管扩张，并且在LLA中气体潴留的证据得到了明确证实。细支气管阻塞可能是LLA发生的最常见原因。
