Original articleImprovement in imaging time and quality of 3D negative-contrast computed tomography cholangiography with minimum intensity projections: application of vari-slice manual cut and erosion functions
Introduction
Direct cholangiography procedures, such as percutaneous transpheptic cholangiography (PTC), endoscopic retrograde cholangiography (ERC), or intraoperative cholangiography, have been regarded as gold standard examinations for patients with suspected biliary obstruction. However, they are invasive investigations [1], [2], [3]. Although magnetic resonance cholangiography (MRC) offers cholangiographic-like images nonivasively, some contraindications and prolonged examination time have limited its use [4]. Helical CT cholangiography without biliary contrast agent has been reported as a useful tool for the assessment of biliary obstruction [4], [5], [6], [7], [8], [9], [10], [11], [12]. In contrast to CT cholangiography with positive cholangiographic contrast agent, it creates a negative contrast CT cholangiography (nCTC) [11], [13]. However, to show the entire biliary tract using 3D nCTC with minimum intensity projection (minIP), manual cut-off is required for the interfering voxels (gas, fat, etc.) surrounding the regions of intra- and extrahepatic biliary systems. This postprocessing method is a time-consuming procedure [7]. Nevertheless, during our experience, those hypodense components were difficult to be removed completely even after performing the manual cut. The purpose of this study was to investigate the improvement in imaging time and quality of 3D nCTC with minIP using the vari-slice manual cut and erosion methods.
Section snippets
Patients
Thirty-eight patients whose ultrasound examination had suggested biliary obstructive disorders accompanied by elevated total serum bilirubin and/or alkaline phosphatase level underwent retrospective CT studies. It included 18 men and 20 women ranging in age from 24 to 87 years old (mean 57.7 years). Among them, 25 patients also underwent ERC (n=10), PTC (n=3), intraoperative cholangiogram (n=5), and MRC (n=7) within 48 h to 1 week after CT examination. Final clinical diagnoses were made by
Results
The presence of biliary obstruction was correctly diagnosed using 3D nCTC with minIP after the first or second erosion in all patients. According to the Baron et al. [14] classification, seven in 38 had extrahepatic ductal obstruction at the porta hepatis, six at the suprapancreatic level, and 25 at the intrapancreatic level (including the ampulla of Vater). The whole cutting width was 157.7±18.1 mm (125–198 mm) and the mean values of the total postprocessing time were shortest with the
Discussion
The terminology of CT cholangiography using conventional intravenous contrast agent has not been uniform. Some researchers described this method as “CT cholangiography without biliary contrast agent” [4] or “CT cholangiography with minimum intensity projection” [7], [8]. Since its imaging principle is opposite to that of CT cholangiography using positive cholangiographic agent, it is also called as “CT cholangiography using a negative contrast” [11], [13] and because the pancreatic and bile
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Comparison of three-dimensional negative-contrast CT cholangiopancreatography with three-dimensional MR cholangiopancreatography for the diagnosis of obstructive biliary diseases
2012, European Journal of RadiologyCitation Excerpt :Several years ago, Park and Rao et al. reported the 3D-nCTCP with MinIP techniques, which permits to cover the whole pancreatobiliary systems in one image similar to that of 3D-MRCP, outlines clear anatomy, and provides excellent overview information for clinical diagnoses as well as no need of additional examination time or radiation exposure, but it needs to segment the liver and pancreas from the surrounding low dense tissues (gas, fat, etc.) that interferes the bile and pancreatic ducts, so a time-consuming postprocedures about 40–60 min is inevitable according to their reports [12,18]. Recently, Zhang et al. [20] have introduced a newly improved method for 3D-nCTCP with vari-slice manual cut and erosion functions in segmentation, the total postprocessing time was shorten to about 20 min, which might make this technique clinically practicable. In our study, both methods correctly identified the presence and location of biliary obstruction in all patients, especially 3D-nCTCP depicting the obstructive morphology and whole pancreatobiliary system was consistent with 3D-MRCP regardless the obstructive location occurred, so it is favorable to those patients who are unsuitable for both PTC and ERCP or failed PTC or ERCP.
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