Pulmonary Intersegmental Planes: Imaging Appearance and Possible Reasons Leading to Their Visualization

Abstract

Purpose:To describe the normal imaging appearance of pulmonary intersegmental planes on thoracic computed tomographic (CT) scans and determine the possible reasons related to their visualization in terms of aging and anatomy. Materials and Methods:The study was approved by the internal ethics review board. Informed consent was obtained. A retrospective review was undertaken of 104 thoracic multidetector CT scans of an older group (.65 years) and younger group (,55 years). The number, location, and appearance rate of intersegmental planes were assessed. Group comparisons were made, and linear regression analysis was used to assess relationships between age and visualization of intersegmental planes. Thirty lung samples (10 3 10 3 10 mm 3 ) from autopsy were scanned by using micro-CT. Thicknesses of intersegmental planes were measured. Significant differences of the thickness between visible and invisible intersegmental planes were assessed with the independent t test. In five fetal specimens (17-21 weeks in gestational age), 7.0-T magnetic resonance (MR) imaging was performed to determine the congenital difference of thickness of intersegmental planes. Results:Within the right lung, appearance rates of visible intersegmental planes were 71.2% at S 1 -S 3 , 54.8% at S 4 -S 5 , and 70.2% at S 7 -S 10 . Within the left lung, appearance rates of visible intersegmental planes were 39.4% at S 1+2 to S 3 , 64.4% at S 4 -S 5 , 18.3% at S 7 -S 8 , and 89.4% at S 7 -S 10 . Appearance rates of visible intersegmental planes on thoracic CT scans were not significantly different (P  .38) between younger and older groups. Mean thicknesses of visible and invisible intersegmental planes were 681.3 mm 6 75.3 (standard deviation) and 221.7 mm 6 54.1, respectively. Visible intersegmental planes were significantly thicker than invisible intersegmental planes (P , .05). Visible intersegmental planes were also seen on fetal lung 7.0-T MR images. Conclusion:The thickness of pulmonary intersegmental planes and variation of intersegmental veins were closely related to visualization of intersegmental planes on thoracic CT scans. Aging was excluded as the possible reason.q RSNA, 2013

CT imaging and pathological basis of linear shadow connecting pulmonary segmental artery to horizontal fissure

“…The linear shadow connecting the pulmonary segmental arteries to the horizontal fissure in this study has been mentioned in some literatures, but no in-depth study is conducted. [ 2 , 3 ] To the best of our knowledge, this is the first systematic analysis for the linear shadow connecting the pulmonary segmental arteries to the horizontal fissure. According to the study, we observe that: first, the linear shadow is observed in 54.33% of normal lung CT images without correlation with gender, age, and smoking history, but with correlating to the integrity of the horizontal fissure.…”

“…Although linear shadows are intrinsic to the lungs, it is still necessary to identify similar normal and abnormal structures in the lungs on thin-slice CT, such as interlobular septum, segmental septum, pulmonary ligament, fibrous cords, and etc. [ 2 , 10 ] First, the interlobular septa are formed by the inward recession of the visceral pleura, which cannot be seen in normal circumstances unless the interstitium of the interlobular septa are thickened. The interlobular septa are perpendicular to the pleura with the length of about 10 to 25 mm.…”

“…Second, the segmental septum is a thin membranous structure located between 2 or 3 adjacent lung segments. Commonly, the medial margin of the segmental septa connects to the mediastinum and the lateral margin connects to the pulmonary segmental veins, [ 2 , 11 ] while for the linear shadow connects to the pulmonary segmental artery and the horizontal fissure respectively. Third, the pulmonary ligament is a bilayer membrane-like structure formed by the visceral pleura.…”

Kohn's pores are not responsible for collateral ventilation between inflated and deflated segments: a microscopic study of pulmonary intersegmental septa in the human lung

“…; Zuo et al. ), and demonstrated that the intersegmental septa can be seen as lines with hyper‐attenuation on multi‐slice computed tomography (MSCT). The high density on MSCT scans of the intersegmental septum indicated the existence of local interstitial fluid.…”

“…; Zuo et al. ), and its composition is only visible in H&E sections at low magnification (Berkmen et al. ).…”