| The liver is the biggest parenchymatous organ of the human body. It has been the hot topic of anatomy and medical imaging study because of its complicated structures and variety diseases. The existing sectional anatomy research methods, which include cryotomy, sheet plastination technique and collodion microtomy, have the shortcoming of thick kerf lost and slice intervals, and the specimen being liable to deformed. Besides, the coronal section materials of the liver are much less than that of the transversal and sagittal section among the existing sectional anatomy materials, which couldn't satisfy the need of precise interpretation of clinical coronal imaging and the requirement of modern hepatic surgery to detailed coronal sectional anatomy materials. Modern imaging techniques such as ultrasonography, MSCT and MRI can display lesions of the liver on transversal, sagittal, coronal, oblique and even arbitrary section, and ultrasonography is the most commonly used examination method for the occupying lesions of the liver. Nowadays, the imaging quality and resolution of ultrasonography has been advanced greatly, and the minute structures, which couldn't be displayed previously, can now be displayed clearly, so it is necessary to investigate not only the multi-orientation sectional anatomy but also the ultrasonographic anatomy of the liver. Meanwhile, as the demands to clinical hepatic surgery and liver transplantation have been promoted increasingly, it is imperative to establish the hepatic surgery computer simulation system. All these require higher to sectional anatomy of the liver than ever before. The sectional anatomy of the liver ought to be developed from transverse section to multiple section, from thick slice to thin slice, from reality to visualization, from section to three dimensions in order to satisfying the new demands of clinical diagnosis and treatment of hepatic lesions and promoting the development of hepatic ultrasonography imaging and clinical hepatic surgery.At the end of 80th age last century, The Federal of American Scientists (FAS) proposed The Visible Human Project (VHP), which dedicates to realize the precision simulation of human from molecule to cell, tissue, organ, system and body. The digital freezing milling technique, which developed from the carrying out of VHP, prompts the sectional anatomy of the liver to the level of sub-millimeter slice intervals and set up a new research approach for sectional anatomy. The 3D visualization of the liver and intrahepatic vessels was then carried out, and it constitutes an important part of the VHP. The first prerequisite of 3D visualization of the liver and intrahepatic vessels is to obtaining a high quality anatomic dataset. But the dataset acquisition method of the liver reported before did not involve some details, and all the virtual liver researches derived only from the cross section and the research on the basis of the coronal sectional dataset has not been reported yet; besides, the thin coronal sectional dataset of the liver has not been obtained up to now. The purpose of our study is to investigate the acquisition method of the thin coronal sectional dataset of the liver so as to acquiring a high quality anatomic dataset and satisfying the need of precise interpretation of clinical coronal imaging greatly, and providing more detailed anatomic data to modern hepatic surgery as well. We then build the digitized visible model of the hepatic vein and intrahepatic portal vein based on the coronal sectional dataset of the liver, and mark the standard ultrasonographic section of the liver in detail under the direction of the thin sectional anatomy foundation of the liver and the 3D morphology manifestation of intrahepatic vessels revealed by the visible model. Furthermore, we outline an ultrasonographic approach to the segmental anatomy of the liver on the basis of Couinaud's segmental anatomy, and investigate the branching patterns of hepatic portal vein in each hepatic segment.This study consists of 4 parts as follows: Part 1: ACQUISITION OF THE THIN CORONAL SECTIONALANATOMIC DATASET OF THE LIVEROBJECTIVE To obtain the thin coronal sectional anatomic data of the liver using digital freezing milling technique.MATERIALS AND METHODS The upper abdomen of one Chinese adult cadaver was selected as the specimen. After CT and MRI examination verified no organic lesions, the specimen was embedded with gelatin in stand erect position and frozen under profound hypothermia, and then the specimen was serially sectioned from anterior to posterior layer by layer with digital freezing milling machine in the freezing chamber. The sequential images were captured by means of a digital camera and the dataset was imported to imaging workstation.RESULTS The thin serial section of the liver added up 699 layers with each layer being 0.2mm in thickness. The shape, location, structure, intrahepatic vessels and adjacent structures of the liver was displayed clearly on each layer of the coronal sectional slice.CONCLUSION The thin coronal sectional anatomic dataset of the liver obtained by the digital freezing milling technique is of high precision and good quality. This provides foundation for three dimensional reconstruction of the liver and intrahepatic vessels based on coronal sectional anatomic dataset of the liver.Part 2: SECTIONAL ANATOMY OF THE LIVER ON THETHIN SERIAL CORONAL PLANEOBJECTIVE To explore the appearance of the hepatic portal vein and its branches, hepatic veins and their tributaries, hepatic lobes, hepatic segments and subsegments on the thin serial coronal section, in order to provide detailed anatomic data for modern image diagnosis and liver surgery.MATERIALS AND METHODS The thin serial coronal sectional anatomy of the liver was investigated by using the dataset obtained in part 1. The course, distribution and presentation section of the hepatic portal vein and its branches, hepatic veins and their tributaries on hepatic lobes, hepatic segments and subsegments were tracked serially and studied from the hepatic hilum section, the division and succession regularity of hepatic segments and subsegments on coronal section were exploited based on the Couinaud's segment theory.RESULTS The present sequence of four parts of left hepatic portal vein on the coronal section, from anterior to posterior, is sac part, sagittal part, angular part and transverse part. They all show axial view, and situated the joint point between the liver's middle part of the width and the mid-infra 1/3 part of the length. The branches of left hepatic portal vein appear on the coronal section in the sequence of left lateroinferior branch, left medial branch and left laterosuperior branch. The right hepatic portal vein, which divides into right anterior and right posterior branch, is wider and shorter than that of the left hepatic portal vein. The right anterior trunk courses laterally and superiorly, and gives off right anterosuperior and right anteroinferior branch, these two branches extend upward and downward respectively, and their branches take on paired appearance, with one of the paired branches locate parallel and anterior to the other. The right posterior portal vein bifurcates into the superior and inferior branches, which travel right posterosuperior and posteroinferior respectively. Three main hepatic veins drain into the inferior vena cava on the level of second porta hepatic. Left hepatic vein is confluenced by superior root and inferior root. The superior root situates posterosuperior laterally, and drains superior segment of left lateral lobe; whereas the inferior root situates anteroinferior medially, and drains inferior segment of left lateral lobe. Middle hepatic vein is confluenced by left root and right root. Its main tributaries, according to the present sequence from anterior to posterior, are left anterior tributaries, anteroinferior tributaries and right anterior tributaries, which drain left medial lobe, inferior segment and superior segment of right anterior lobe respectively. Right hepatic vein, which draining blood of right part of right anterior lobe and large portion of right posterior lobe, join the inferior vena cava solitarily. The main tributaries of right hepatic vein, according to the present sequence from anterior to posterior, are right anterior tributaries, right posterior supramarginal vein and posteroinferior tributaries.CONCLUSION The thin coronal sectional anatomy of the hepatic portal veins, hepatic veins and hepatic segments are described fully on the level of sub-millimeter slice intervals, which satisfy the need of precise interpretation of clinical coronal imaging greatly, and provide more detailed anatomic data to modern hepatic surgery as well.Part 3: THREE DIMENSIONAL RECONSTRUCTION OF THEHEPATIC VEIN AND INTRAHEPATIC PORTAL VEIN BASED ONTHE CORONAL SECTIONAL ANATOMICDATASET OF THE LIVEROBJECTIVE To build the digitized visible model of hepatic vein and intrahepatic portal vein based on the thin coronal sectional anatomic dataset of the liver obtained in part 1, providing morphologic foundation for image diagnosis and liver surgery computer simulation system.MATERIALS AND METHODS The pre-reconstructed structure were identified and extracted, and the data were segmented by the method of manual intervention. Using 3D medical visualization software exploited by Chinese University of Hong Kong, the 3D reconstruction was established by volume rendering and surface rendering reconstruction. The visualized model of hepatic vein and intrahepatic portal vein was constructed by volume rendering reconstruction.RESULTS The dynamic displaying of the hepatic vein and intrahepatic portal vein continuously at different orientation was realized on computer. The visualized model of hepatic vein and intrahepatic portal vein could be displayed singly or as a whole, and could be rotated around any axis at any angle. The model displayed the complicated adjacent relationship of the hepatic portal vein and hepatic vein realistically in 3D space. CONCLUSION High quality 2D images and suitable 3D reconstruction method ensure the accuracy and precision of the digital visualized model, which lay foundation for the transition towards clinical application.Part 4: THE ULTRASONOGRAPHIC ANATOMY OF THEHEPATIC SEGMENTSOBJECTIVE To mark the standard ultrasonographic section of the liver in detail under the direction of the thin sectional anatomy foundation of the liver and the 3D morphology manifestation of the hepatic vein and intrahepatic portal vein revealed by the digitized visible model. Furthermore, outline an ultrasonographic approach to the segmental anatomy of the liver and investigate the branching patterns of hepatic portal vein in each segment, so as to providing more detailed ultrasonographic anatomic data to clinic.MATERIALS AND METHODS One hundred subjects without digestive system symptoms, operation history and occupying lesions of the liver, who has normal liver ultrasonograms and easily visible intrahepatic vasculature, were selected as the observation object. The standardized ultrasonographic examination was peformed on the right upper abdomen of the subjects in the sequence of transverse section, sagittal section, oblique section and oblique section through the right intercostals to obtaining the ultrasonograms of all sections. The ultrasonograms of various sections were marked in detail, the ultrasonographic approach to the segmental anatomy of the liver on the basis of Couinaud's segmental theory was described and the branching patterns of the hepatic portal vein in each hepatic segment were investigated.RESULTS The standard ultrasonograms of the liver along various sections are obtained by high resolution ultrasonographic equipment, which displays the main intrahepatic structures clearly. The hepatic segments are defined on ultrasonograms by the portal veins that lead into them and by the hepatic veins that separate them, thus the branches of portal veins are used as indicative sign in the determination of segmental location, whereas the hepatic veins are used as boundary sign, and the ligaments and gallbladder is used as subsidiary landmarks. Each segment has a branch (or a group of branches) of the portal vein at its center, so the portal venous anatomy and the relationship between the lesion and the portal vein is considered far more important in definition of the hepatic segments and localization of the focal hepatic lesions. The branching patterns of the hepatic portal vein in Segment I - Segment IV can be divided into single, double, triple and tetrad branch type according to the branching numbers demonstrated on the sonograms, while the hepatic portal veins in Segment VIII and V show three kinds of branching pattern: symmetry type, interlaced type and branch appearance type. The hepatic portal veins in Segment VII and VI locate posteriorly, so they are difficult to be displayed in whole course and defined in branching patterns.CONCLUSION The profound investigation of the ultrasonographic anatomy of the hepatic segments under the direction of sectional anatomy foundation of the liver and the 3D morphologic manifestation of intrahepatic vessels provide detailed ultrasonographic anatomic data to clinic.CONCLUSIONS AND SIGNIFICANCE1. We applied the digital freezing milling technique in the present study to obtain a serial coronal section dataset of the liver in 0.2mm intervals. The upper abdomen specimen was placed in vertical position and milled from anterior to posterior by SKC500 milling machine in the freezing chamber, the serial-sectioning was done in a fixation without frequently mounting the specimen on and dismounting it off the milling table. This technique set a new research approach for human anatomy, and the data can be input computer directly to be reconstructed, all these prompt the sectional anatomic study to develop towards satisfying the clinical needs of obtaining thinner section than ever before and the visualization of three dimensions.2. The thin serial coronal sectional anatomic dataset of the liver displays the course, distribution and presentation section of the hepatic portal vein and its branches, hepatic veins and their tributaries on hepatic lobes, hepatic segments and subsegments, and the division and succession regularity of hepatic segments and subsegments on the level of sub-millimeter slice intervals, which satisfies the need of precise interpretation of clinical coronal imaging greatly, and provides more detailed anatomic data to modern hepatic surgery as well.3. The pre-reconstructed structures were identified and extracted, and the data were segmented by the method of manual intervention, then the digitized visible model of hepatic vein and intrahepatic portal vein is built by volume rendering and surface rendering reconstruction on the basis of the thin coronal sectional anatomic dataset of the liver. The 3D model reveals the complicated space location relationship between the hepatic portal vein and hepatic vein. High quality 2D images and suitable 3D reconstruction method ensure the accuracy and precision of the digital visualized model, which lay foundation for the transition towards clinical application.4. The standard ultrasonograms of various sections of the liver obtained by high resolution ultrasonographic equipment are marked in detail under the direction of thin serial sectional anatomy foundation and the 3D morphologic manifestation of intrahepatic vessels revealed by the digitized visible model. The ultrasonographic approach to the segmental anatomy of the liver on the basis of Couinaud's segmental theory is described and the branching patterns of the hepatic portal vein in each hepatic segment are investigated. The profound research of the ultrasonographic anatomy of the liver provides more detailed ultrasonographic anatomic data to clinic. |
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