|Year : 2013 | Volume
| Issue : 4 | Page : 318-326
Evaluation of the role of multidetector computed tomography in biliary obstruction
Abdel Monem Nooman Darwish, Asem Ahmed El Fert, Amr Mohamed El Badry, Eman Moussa
Department of Radiodiagnosis and Medical Imaging; Department of Tropical Medicine and Infectious Diseases, Faculty of Medicine, Tanta University, Tanta, Egypt
|Date of Submission||15-Aug-2013|
|Date of Acceptance||20-Sep-2013|
|Date of Web Publication||1-Feb-2014|
Amr Mohamed El Badry
Department of Radiodiagnosis and Medical Imaging; Department of Tropical Medicine and Infectious Diseases, Faculty of Medicine, Tanta University, Tanta
The aim of the study was to evaluate the role of multidetector computed tomography (MDCT) cholangiography in detecting the cause and the level of biliary obstruction and also evaluating the global performance of combined axial, multiplanar reformatting (MPR), and minimum-intensity projection (MinIP) image reconstructions.
Patients and methods
Between January 2012 and August 2012, this study was performed on 30 patients with clinical and biochemical signs (increased serum levels of bilirubin and/or alkaline phosphatase) suggesting bile duct obstruction who referred to the CT unit in Tanta university hospital from the department of tropical medicine and infectious diseases. These patients were examined by 16-channel CT using a three-phase contrast protocol. The results obtained were compared with the results of histopathological and operative data in patients who underwent surgery.
Our study showed that MDCT cholangiography was accurate in detecting the presence and the level of biliary obstruction in all 30 cases examined (100%), whereas it could define the cause of obstruction correctly in 93.3% of the cases. The overall performance of MPR and MinIP reconstruction in addition to conventional MDCT images showed a synergic effect to conventional axial CT images, showing an improvement in visualization in 83.3% and additional value in 30 and 16% of the cases, respectively.
MDCT cholangiography is a noninvasive and fast imaging tool in the assessment of patients with biliary obstruction. MPR and MinIP images provide an improvement of visualization of the biliary system and additional diagnostic value for differentiation of benign from malignant biliary obstruction. It represents a valuable supplement to conventional MDCT imaging of hepatopancreatic disorders.
Keywords: Biliary obstruction, minimum intensity projection, multidetector computed tomography, multiplanar reformatting
|How to cite this article:|
Darwish AN, El Fert AA, El Badry AM, Moussa E. Evaluation of the role of multidetector computed tomography in biliary obstruction. Tanta Med J 2013;41:318-26
|How to cite this URL:|
Darwish AN, El Fert AA, El Badry AM, Moussa E. Evaluation of the role of multidetector computed tomography in biliary obstruction. Tanta Med J [serial online] 2013 [cited 2018 Feb 23];41:318-26. Available from: http://www.tdj.eg.net/text.asp?2013/41/4/318/126194
| Introduction|| |
In patients with suspected biliary obstruction, accurate and early diagnosis is crucial to select the appropriate therapeutic management , . Endoscopic cholangiopancreatography (ERCP) and percutaneous transhepatic cholangiography are the gold standard techniques because they allow both a direct visualization of biliary tree and therapeutic intervention. However, they are invasive techniques and carry associated risks that range in severity from minor to life-threatening , .
Recently, multidetector computed tomography (MDCT) has been introduced into clinical practice. It allows faster scanning, which decreases motion and breathing artifacts  . MDCT's ability to obtain a volume dataset with submillimeter spatial resolution allows optimal display of the bile duct using multiplanar reformatting (MPR) and minimum-intensity projection (MinIP) without compromising the image quality. Using MinIP, the fluid density, as contained in the biliary duct, is picked up from the contrast-enhanced vessel together with that of the enhanced hepatic and pancreatic parenchyma. The combined use of MPR and MinIP techniques significantly improves the images of the biliary ducts and their site of confluence compared with those obtained by axial CT  . This leads to better assessment of obstructive biliary diseases because of the superior resolution in outlining the details of the pancreaticobiliary system  .
| Patients and methods|| |
This study was performed on 30 patients (17 men and 13 women) with clinical and biochemical signs (increased serum levels of bilirubin and/or alkaline phosphatase) suggesting bile duct obstruction referred to the Radiology and Imaging Department in Tanta University hospital from the department of Tropical and Infectious diseases.
Multidetector computed tomography technique
This study was performed with a 16-slice multidetector CT using a three-phase contrast protocol for imaging of the upper abdomen focusing on the liver and pancreas.
A low-residue diet was prescribed 24 h before the procedure, and the patient was instructed to come to the CT unit completely fasting for at least 4 h. The patient took 800-1000 ml of water orally before examination to distend the gastrointestinal tract. Reassurance and a brief explanation of the procedure to the patient were carried out.
All patients were examined in the supine position; each patient was instructed to remain stable and not to move during examination. Suspended breathing during the scanning duration was also important. Scanning in the anteroposterior scout view to set the scanning area from the hepatic dome to the level of L3 vertebra was carried out.
Precontrast scanning of the upper abdomen in the craniocaudal direction during breath hold to screen for gall bladder or bile duct stones was performed.
Postcontrast scanning of the hepatobiliary system was performed after automatic injection of 1 ml/kg (300 mg iodine/kg) of a nonionic iodinated contrast at a rate of 5 ml/s into the antecubital vein with a delay of 35 s for the arterial phase, 70 s for the portal venous phase, and 200 s for the delayed phase. Scan parameters for the portovenous phase are served for the reconstruction of MinIP images because of the high contrast between the bile ducts and the liver parenchyma.
Postcontrast scan parameters
Postcontrast scan parameters were: tube current 120 kV and 400 mAs, slice thickness 5 mm, collimation of 0.6 mm, pitch 0.6, and rotation time 0.5 s.
Portal venous-phase images were reconstructed at a 0.6 mm slice thickness and 0.3 slice interval and the reconstructed images were processed in coronal, sagittal, and oblique planes.
CT cholangiographic images were created by MPR and thin-slab MinIP techniques; MPR uses oblique projection of 0.6 mm thickness in contiguous planes throughout the biliary tract and the MinIP technique uses variable slab thickness according to bile duct dilatation in coronal oblique planes throughout the biliary tract.
| Results|| |
Thirty patients were selected from those referred to the Radio diagnosis and Imaging Department of Tanta University hospital with clinical and laboratory signs of biliary obstruction. The final diagnosis obtained depends on histopathological diagnosis, operative data, and clinical follow-up.
Our study patients included 30 individuals (17 men and 13 women), with a mean age of 55 years (range 35-74 years).
Our patients were classified according to the level of obstruction into four groups:
- Group I: intrahepatic level (eight cases) 27%.
- Group II: hilar level (seven cases) 23%.
- Group III: suprapancreatic level (three cases) 10%.
- Group IV: pancreatic level including ampullary level (12 cases) 40%.
Regarding the cause of biliary obstruction, our patients were classified into two categories [Table 1]:
- Benign obstruction.
- Malignant obstruction.
Standard of reference examination
A percutaneous biopsy was performed in 12 cases (an ultrasound-guided biopsy in 10 cases and a CT-guided biopsy in two cases), ERCP was performed in 10 cases, surgery was performed in five cases, and clinical and laboratory follow-up were carried out in three cases [Table 2].
Group I: intrahepatic level
Morphologic multidetector computed tomography features
The mean size of the liver masses, measured on CT scans, was 9.5 cm (range from 6-13 cm). An intrahepatic bile duct dilatation proximal to the mass was seen in all patients. Dilatation of the extrahepatic biliary ducts was not detected. Portal vein infiltration was seen in five patients (5/8) (62.5%). Small satellite nodules within the liver were detected in two patients (2/8) (25%). Regional lymph node enlargement was present in one patient (1/8) (12%). Retraction of the liver capsule was seen in one patient (1/8) (12%) [Table 3].
|Table 3: Morphologic multidetector computed tomography features in group I|
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Patterns of enhancement
In three of five patients with peripheral cholangiocarcinoma, the lesion showed peripheral rim enhancement at the arterial phase with a hypoattenuated center and progressive increased peripheral enhancement in the portovenous and the delayed phases, whereas in the other two patients, there was no significant enhancement at the arterial phase and progressive peripheral enhancement at the portovenous and the delayed phases.
In patients with a hepatocellular carcinoma, the lesion showed rapid vascular blush at the arterial phase and rapid washout at the portovenous phase.
In patients with a giant hemangioma, the lesion showed peripheral nodular enhancement in the arterial phase with increasing enhancement in the portovenous and the delayed phases.
In patients with multiple liver abscesses, the lesion showed a central hypodense area, intermediate ring-like enhancement, and a peripheral hypodense ring in the arterial phase. The portovenous phase showed a central hypodense area and a relatively thick ring-like enhancement of the intermediate and peripheral zones [Table 4] and [Table 5].
Group II (hilar level obstruction)
Morphologic multidetector computed tomography features and pattern of enhancement
All patients in this group showed dilatation of intrahepatic bile ducts with normal caliber extrahepatic bile ducts. In two of three patients with hilar cholangiocarcinoma, there was an isodense mass at the hepatic hilum; this mass showed slight inhomogenous enhancement at the arterial and the portovenous phases and obvious enhancement at the delayed phase; the third patient showed diffuse thickening of the intrahepatic and the extrahepatic bile ducts, which exhibit obvious enhancement at the arterial and the portovenous phases with decreased enhancement at the delayed phase.
Two patients with a postanastomotic stricture (after liver transplantation) showed intrahepatic biliary radical's dilatation with no extrahepatic biliary radical's dilatation.
Multiple enlarged portahepatis and para-aortic lymph nodes were detected in two patients.
Group III (suprapancreatic level)
Three patients had obstruction at the suprapancreatic level. One patient had a calculus within the common duct, one patient showed multiple small stones in both intrahepatic and extrahepatic ducts and the last patient had missed stones after cholecystectomy.
MDCT cholangiography using MPR and MinIP with variable slab-thickness images could detect intrahepatic and extrahepatic bile duct stones of suprapancreatic level in the three patients examined (100%), which appeared as an intraductal focus of increased density within the low attenuated bile duct [Table 6].
Group IV (pancreatic-level obstruction including ampulla of Vater)
Morphologic multidetector computed tomography features
MDCT could detect a pancreatic head mass in all six patients (100%). It appeared as a low-density lesion in maximally enhanced pancreas, the mass size ranging from 10 to 30 mm; intrahepatic and extrahepatic biliary dilatation were observed in all patients, vascular invasion (superior mesenteric vein invasion) was detected in one patient (16%), lymph node metastasis was observed in two patients (30%), distant metastasis (hepatic deposits) was observed in two patients (30%), and ascites was observed in one patient (16%).
Additional value of multiplanar reformatting compared with conventional multidetector computed tomography
According to the reference data, the source of obstruction was located at the intrahepatic level (eight patients), the hilar level (seven patients), the suprapancreatic level (three patients), the pancreatic head level (six patients), the distal common bile duct (CBD), and ampullary level in six patients. The level of obstruction was detected in all cases on both conventional MDCT and MinIP and MPR images.
In five patients with intrahepatic-level obstruction, (MPR) images show improvement in the visualization of portal vein invasion.
In three patients with hilar cholangiocarcinoma and in two patients with postanastomotic stricture, axial and coronal oblique images had an additional value over axial images due to the improvement in the definition of stenosis, accurate assessment of the hilar mass, and the extension along the CBD.
At the level of the suprapancreatic obstruction, coronal oblique images in one patient with CBD stone had improved the visualization of the stone, whereas in the other two patients with intrahepatic and extrahepatic stones, axial oblique and coronal oblique images had an additional value over axial images in detecting missed stones, which could not be detected easily with axial images.
In six patients with a pancreatic head mass, MPR images (axial oblique and coronal oblique images) had improved visualization of the dilated pancreatic duct and its relation to the mass.
In four patients with lower-end CBD obstruction, MPR and MinIP images showed a fair additional diagnostic value owing to improved characterization of the lower-end CBD stricture in two cases [Table 7].
|Table 7: Additional value of multiplanar reformatting compared with conventional multidetector computed tomography|
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Additional value of minimum-intensity projection compared with conventional multidetector computed tomography
In two patients with intrahepatic-level obstruction, MinIP images provided moderate additional value owing to the superior visualization of the intrahepatic bile duct dilatation, which increased the sensitivity in the detection of mild dilated intrahepatic biliary radicles and the transition from dilated to undilated ducts, whereas it shows no additional value in two patients and improved the visualization of the lesion in five patients.
In five patients with hilar-level obstruction, MinIP images had an additional value due to improvement in the definition of stenosis in the region of the CBD bifurcation and accurate assessment of the extension of hilar cholangiocarcinoma over axial images.
In two patients with calcular obstruction, MinIP images with a small slab thickness had an additional value by increasing the conspicuity of small intrahepatic stones and missed CBD stones after cholecystectomy, which could not be easily detected more than axial images.
In the six patients with a pancreatic head tumor, MinIP images increased the conspicuity of the lesion as a hypodense tumor within enhanced pancreatic parenchyma and its relationship to the pancreatic duct [Table 8].
|Table 8: Additional value of minimum-intensity projection compared with conventional multidetector computed tomography|
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[Figure 1] shows a triphasic scan of a 61-year-old male patient: (a) the arterial phase shows an ill-defined hypodense mass at segment VII with peripheral enhancement and biliary dilatation (arrow). (b and c) Portal and delayed phases at the same level show that the lesion becomes progressively hyperattenuating relative to the liver parenchyma with hyperenhancement of the central area and peripheral low attenuation. The portal-phase image shows infiltration of the left portal vein branch. Pneumobilia is evident. MDCT cholangiography using axial (d) and coronal (e) MinIP images shows dilatation of the intrahepatic bile ducts distal to the mass.
[Figure 2] shows a triphasic scan of a 60-year-old male patient: (a) the noncontrast phase shows intrahepatic bile duct stones. The arterial phase (b) shows moderate dilatation of intrahepatic ducts because of an ill-defined hypodense tumor at the confluence of the right and the left hepatic ducts (arrows) with inhomogeneous enhancement. At the portal phase (c), the mass is hypoattenuated in relation to the enhanced hepatic parenchyma. At the delayed phase (d), it becomes attenuated to the hepatic parenchyma. Axial and coronal multiplanar images (e and f) show the extension of the spread of the tumor, the periductal infiltration of the hepatic parenchyma, and encasement of the right portal branch. The axial MinIP image (g) shows improved delination of the tumor and dilated intrahepatic bile ducts. The curved multiplanar image (c) shows a normal caliber pancreatic duct.
[Figure 3] shows axial non-contrast-enhanced CT (a) of a 51-year-old female patient with hyperattenuating stone surrounded by hypoattenuated bile at the CBD. (b) Postcontrast CT during the portal phase shows CBD stone with minimal intrahepatic bile duct dilatation, (c) coronal oblique reformatting using MinIP shows CBD stones more clearly with minimal intrahepatic bile duct dilatation (arrows).
[Figure 4] shows a triphasic scan of a 64-year-old male patient with an ill-defined small soft tissue lesion seen at the pancreatic head (open arrows).The lesion is hypoattenuated in relation to the enhanced pancreatic parenchyma at the arterial phase (a), the portovenous phase (b), and the delayed phase (c). The axial image (d) at a higher level shows dilated CBD (black arrow) and pancreatic duct (white thin arrows). Coronal oblique reformatting (e) using MinIP shows dilated intrahepatic bile ducts and CBD (white arrows) that end abruptly by the mass (open arrow). Curved MPR (f) along the pancreatic duct using MinIP shows a dilated irregular pancreatic duct (black arrows) that ends abruptly by the mass(open arrow). Ascites and multiple hepatic metastases are noted.
[Figure 5] shows a triphasic scan of a 38-year-old male patient with mild intrahepatic bile duct dilatation and dilated CBD with no mass or stone detected. (a) Axial contrast-enhanced CT at the arterial phase. (b) Axial contrast-enhanced CT at the arterial phase at a lower level. Axial contrast-enhanced CT at the portal phase. Axial contrast-enhanced CT at the delayed phase. (e) Coronal oblique MinIP. (f) Curved multiplanar along the course of CBD shows dilatation of CBD along its course with a smooth tapering end.
[Figure 6] shows postcontrast-enhanced CT of a 55-year-old male patient. (a) The axial image during the portal phase at the level of lower-end CBD showing a small slightly enhanced soft tissue lesion protruding into the lower end of CBD (white arrow). (b) The axial image at the lower level shows an ill-defined heterogenous soft tissue lesion (m) at the periampullary area infiltrating the head of pancreas. (c) Coronal oblique and (d) curved MPR show a well-delinated lesion and its extension into the lower end of the CBD and infiltration of the second part of the duodenum(d). The CBD and the intrahepatic bile ducts are dilated while the pancreatic duct has normal caliber.
| Discussion|| |
Our study showed that MDCT cholangiography was accurate in detecting the presence and the level of biliary obstruction in 100% of the cases, whereas it could define correctly the cause of obstruction in 93.3% of the cases. In the study performed with Zhang et al.  MDCT cholangiography was accurate in detecting the presence and location of the obstruction in 100% of studied cases and the diagnosis of the obstruction was correctly evaluated in 95.7%.
In the present study, MDCT cholangiography demonstrated biliary tree dilatation in all cases: to a mild degree in 33.3% of the cases, to a moderate degree in 40% and to a severe degree in 26.6% of the cases. It was observed that the degree of biliary duct dilatation caused by malignancies was more severe than those caused by benign strictures; this coordinates with the study by Tongdee et al.  , who found that the degree of biliary duct dilatation caused by malignancies tend to be more severe than those caused by benign strictures, whereas biliary calculi can cause a variable degree of biliary duct dilatation, ranging from none to severe dilatation, depending on its size.
In intrahepatic level obstruction, in the present study, MDCT cholangiography could detect all intrahepatic mass lesions in all studied patients and could easily differentiate between cystic and solid lesions, other findings such as enlarged regional lymph nodes, satellite nodules and portal infiltration were detected accurately. MDCT cholangiography was more sensitive in the detection of the degree of intrahepatic bile duct dilatation, characterization of hepatic lesions according to the enhancement pattern and more accurate in the estimation of the size due to adequate delineation of the tumor size and the number relative to segmental anatomy; this agreed with Kim et al.  , whose MinIP images showed additional value in two patients with a mild degree of intrahepatic bile duct dilatation, not clearly detected in conventional axial images; MPR images also improved the visualization of vascular infiltration detected by axial images in five patients. This agreed with the study by Denecke et al.  , who concluded that MinIP and MPR images combined with conventional MDCT improve the assessment of mild degree of bile duct dilatation and in vascular invasion.
In hilar level obstruction in our study, MDCT cholangiography diagnosed all patients with hilar obstruction (100%) correctly. In three patients with hilar cholangiocarcinoma; accurate diagnosis of the horizontal and the vertical spreading of the tumor was performed in the 3 cases studied (100%); accurate evaluation of vascular encasement and nodal metastasis was noted. In the study performed by Kim et al.  MDCT cholangiography diagnosed all studied cases of hilar cholangiocarcinoma (100%) correctly.
In addition, our study demonstrated that MinIP and MPR images had an additional value in the diagnostic accuracy for the staging of bile duct cancer over the use of axial images alone, due to improvement in the definition of stenosis in the region of the CBD bifurcation and accurate assessment of the extension of hilar cholangiocarcinoma, which coordinate with the study performed by Ryoo et al.  , who concluded that MDCT with MinIP and MPR images was able to provide an accuracy for the Bismuth-Corlette-type classification comparable to that of transaxial MDCT only. Other studies performed by Park et al.  and Lee et al.  had the same conclusion.Suprapancreatic-level obstruction MDCT cholangiography using MPR and MinIP with variable slab thickness images was accurate in demonstrating small intrahepatic and extrahepatic bile duct stones, whereas in one case of lower-end CBD obstruction, lower-end CBD stone of soft tissue density was misdiagnosed as an ampullary mass. Zandrino et al.  and Anderson et al.  reported a sensitivity of MDCT of 82 and 77.8%, respectively, in choledocholithiasis; these studies reported that MDCT has a lower sensitivity in detecting iso-attenuated bile duct stones. In the present study, the postprocessing technique shows additional value in detecting bile duct stone; in one patient with intrahepatic stones, axial oblique MinIP images in the plane along the course of the intrahepatic dilated bile duct delineated the stones more clearly than the axial plane images, whereas coronal oblique images along the course of CBD were used in two patients with CBD stones. The curved MPR image was useful in one patient with tortuous CBD. This agreed with several investigators such as Kim et al.  , Zandrino et al.  and Tongdee et al.  . Pancreatic including ampullary-level obstruction, MDCT could detect the pancreatic head mass in all six cases studied (100%). This coincides with the study by Heller et al.  who stated that the sensitivity of MDCT in the detection of pancreatic head mass approached 100%. MinIP images increased the conspicuity of the tumor as a hypodense lesion in contrast to the enhanced pancreatic parenchyma that agreed with Salles et al.  who reported that MinIP, by emphasizing hypodense structures, shows well not only ducts, but also emphasizes the variably hypodense ductal adenocarcinoma against the background of more intensely enhancing normal pancreatic parenchyma. Using variable obliquities, the relationship of the tumor to other structures, such as stomach and duodenum, can be emphasized to aid surgical planning. MPR and cMPR images drawn along the CBD, the pancreatic duct, showed improvement in tumor detection in all six cases studied (100%) and additional value (two cases) in the detection of vascular invasion and enlarged regional lymph nodes; this agrees with Karmazanovsky et al.  who reported that MDCT combined with the use of multiplanar reconstruction can stage pancreatic cancer in a more careful and accurate way. Prokesch et al.  using curved MPR (cMPR) along the CBD, the pancreatic duct, and mesenteric vessels showed a sensitivity for tumor detection of 98% compared with 95% for axial images alone.
Concerning the detection of ampullary tumor on CT, our study showed that MDCT using thin-collimation combined with MPR images could identify the enhancing ampullary mass in the three cases studied; the use of negative oral contrast material (e.g. water) increased the conspicuity of the enhancing ampullary mass within the distended duodenum. Chang et al.  showed a sensitivity of MDCT of 91.7% in the detection of ampullary mass compared with 20-39% by single-slice CT; the increase in sensitivity owing to advances in MDCT resolution, which has been improved to the submillimeter level, and so the major duodenal papillae, can be observed and measured. The study reported many criteria for the differentiation between an ampullary tumor and a benign stricture including the measurability, the enhancement pattern, and the attenuation value of the papilla/papillary mass on the portal venous phase, and the maximum diameters of the extrahepatic duct and the main pancreatic duct. However, it emphasizes that the only variable by which ampullary tumor could be differentiated from benign papillary stricture was the size of the papilla/papillary mass. The most appropriate cutoff value of papilla/papillary mass size was 12.3 mm, whereas all patients with no measurable papilla/papillary mass had a benign stricture.
Regarding the detection and classification of bile duct narrowing, MDCT with multiplanar capabilities, especially in the coronal, curved linear and oblique planes, increased the ease of visualization and characterization of the biliary stricture. Anderson et al.  and Kim et al.  reported the CT criteria of benign strictures as smooth and gradual narrowing of the CBD in a short segment less than 1 cm without mass. In the present study, these criteria were seen in four patients. The diagnosis was confirmed by ERCP in three of four cases, whereas the ERCP finding was suspicious in one case; further biopsy revealed malignant infiltration. In our study, the overall performance of MPR and MinIP reconstruction in addition to conventional MDCT images showed a synergic effect to conventional axial CT images showing improvement in visualization in 83.3% and additional value in 30 and 16% of the cases, respectively; this was higher than a study performed by Denecke et al.  , in which they revealed an improved visualization of the biliary system in 73% of the cases and additional value in13% of the cases studied.
| Conclusion|| |
MDCT cholangiography showed high sensitivity in detecting the cause and the level of biliary obstruction; multiphasic MDCT cholangiography was also important in cases of malignant obstruction for characterization of the lesion according to the enhancement pattern. In calcular obstruction, MDCT cholangiography with postprocessing techniques (MPR and MinIP) was of significant value in biliary stones. In malignant obstruction, MDCT cholangiography with MPR and MinIP images allows one-step evaluation of the biliary tree and the surrounding liver, pancreas and lymph nodes with optimal assessment of the lesion location and extension. Hence, it is of considerable value in preoperative staging of hilar cholangiocarcinoma.
| Acknowledgements|| |
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]