Volumetric thin-section CT: evaluation of pulmonaryinterlobar fissures

Abstract

T he pulmonary interlobar fissures are important landmarks for pulmonary anatomy. They adopt a double membrane structure formed by invagination of the visceral pleura. The interlobar fissures are 1-3 mm thick and consist of the right oblique fissure (ROF), horizontal fissure (HF), and left oblique fissure (LOF) (1, 2). The recognition of pulmonary interlobar fissures and their variations is beneficial for identifying pulmonary lesion locations, evaluating disease progression, selecting surgical operations, and applying endoscopic therapy (3-5). With the constant development of imaging techniques, thin-section computed tomography (CT) can provide more detailed information regarding lung structure with respect to the anatomy (5-7). Multiplanar reformatting (MPR) (8) and maximal intensity projection (MIP) are reconstruction techniques based on a noninvasive methodology that detect pulmonary interlobar fissure variations. The results generated by these techniques highly resemble the results of an autopsy (8). In this study, the pulmonary interlobar fissures and their variations were investigated and analyzed by volumetric thin-section MPR and MIP images. MethodsThe study was approved by the institutional review board and the institutional ethics committee. A retrospective analysis was performed on CT scans of 862 adult subjects ( PURPOSEWe aimed to perform an imaging analysis of interlobar fissures and their variations using thin-section computed tomography (CT). METHODSVolumetric thin-section CT scanning was performed in 208 subjects. Interlobar fissures were observed on axial images, and reconstructed coronal and sagittal images were observed by multiplanar reformatting (MPR). The vessel distributions were verified by maximal intensity projection (MIP). On the axial images, the interlobar fissures were characterized by lines of hyperattenuation, bands of hyperattenuation, avascular zones, and mixed imaging. The interlobar fissures were divided into seven grades according to the percentage of defects over the entire fissure. RESULTSOn the axial images, of all interlobar fissures without avascular zones, 70.2% of the right oblique fissures (ROFs) and 94.2% of the left oblique fissures (LOFs) appeared as lines, and 83.2% of the horizontal fissures (HFs) appeared as bands. All of the interlobar fissures appeared as lines on the coronal and sagittal images. Of all cases, 17.8% showed fully complete interlobar fissures for all three fissures. Incomplete fissures included 41.3% of ROFs, 58.2% of HFs, and 45.2% of LOFs. In ROFs and LOFs, discontinuity was most frequently below 20%, while in HFs discontinuity was most frequently 41%-60%. The most common classification of incomplete interlobar fissures was a discontinuous avascular zone. CONCLUSIONIncomplete interlobar fissures are common variations of interlobar fissures. Techniques including volumetric thin-section CT, MPR, and MIP can assist in the diagnosis of incomplete interlobar fissures.

The fissure: interlobar collateral ventilation and implications for endoscopic therapy in emphysema

“…Koenigkam-Santos et al 29 described a high agreement between experienced radiologists for the major fissures, but rather moderate for the minor fissure (k=0.53). Cronin et al 31 described a greater than 90% agreement for all fissures, Guan et al 34 found a fair to nearly perfect agreement between two radiologists (k=0.593–0.652) and Koenigkam-Santos et al 28 described a reported interobserver agreement of 0.70–0.76. This is the case with experienced radiologists or pneumologists; inexperienced readers most probably have lower agreement.…”

“…Possible explanations are the varying patient groups with and without pulmonary disease, different kind of reviewers, various or no criteria to define an incomplete fissure, or used CT-scan technique (eg, slide thickness). 34 …”

“…Several authors described the following diagnostic criteria for incomplete interlobar fissures: “1) neither a clear avascular zone nor interlobar line is observed; 2) vascular images in adjacent lobes cross over the interlobar region; 3) pulmonary blood vessels, particularly the pulmonary vein, penetrate the interlobar region; 4) the pulmonary vein is observed in the interlobar region and is related to the vascular images in adjacent lobes.” 30 , 32 , 34 Other authors did not use predefined diagnostic criteria, but they used consensus or experts opinion to describe the fissures as complete or incomplete. 23 , 28 , 29 , 31 , 33 …”

Double-domed horizontal fissure

“…We read with interest the article entitled "Volumetric thin-section CT: evaluation of pulmonary interlobar fissures" by Guan et al (1) in the November-December 2015 issue of Diagnostic and Interventional Radiology. The authors gave detailed information about interlobar fissures, their incompleteness, relationship to vascular structures, CT appearance, and defect location.…”

Prevalence of incomplete interlobar fissures of the lung

“…For assessment on CT, the authors usually state criteria for incomplete fissures, with several using four types accord-ing to the varying presence of vessels, including the situation when a fissure is simply missing. Data from various CT methods were mostly obtained from hundreds of patients 1,[12][13][14][15][16][17][18][19][20][21][22][23] . Only Frija et al 12 used healthy volunteers.…”