Quality Control, Clinic Application And Experimental Study On Hepatic MRA By Means Of 3DDCEMRA

The primary principle of MRA is flow-related intensity effect or phase effect which demonstrates blood vessels by virtue of the flowing property of blood. At present, time of flying (TOF) and phase contrast (PC) are the frequent used un-enhanced methods of MRA, which are adapted extensively in demonstrating cerebral, jugular and peripheral blood vessels because of no damage and high sensitivity. But the methods are limited to some types of blood stream. The technique of TOF is difficult to display some blood vessels perfectly when they are not vertical to the slice, or presented obviously circuitous or bifurcated, because the saturated blood spins in the vessels can not be excited by new radio frequency pulses so that the spins produce no or very low blood signal. And when the technique of PC is adapted, if the direction or velocity of blood stream was changed abruptly, or if blood flows through a length of narrowed or dilated vessel, blood signal loss happens due to onflow or vortex leading to dephasing of blood spins. The above phenomena become obvious in body MRA, and even worse due to the influence of breath, heartbeat and movement. Three-dimensional dynamic contrast-enhanced magnetic resonance angiography (3DDCEMRA) is a technique to inject paramagnetic contrast Gd-DTPA into vein resulting in obviously more shortened T1 relaxation time of blood spins than that of background tissue (including fat tissue). The method is independent of the blood flowing effect in the vessels, and shortens the imaging time greatly so that body MRA can be achieved within the time of less than 20s with a big breath hold and a bigfield of view, thus, the saturation effect and influence of breath were decreased effectively leading to a greatly improved contrast between blood and background tissue. In addition, Gd-DTPA is a very safe contrast material without any apparent side effect. 3DDCEMRA can display the liver's interested vessel system from any angle, especially the imaging anatomy and the morphologic analysis of hepatic vein system, the dynamic blood perfusion of portal vein system and inferior vena cava behind the liver. It is of important value for diagnosis, therapy and the formulation of operation plan. Anyhow, the technique of 3DDCEMRA brings about revolutionary development of the imaging technique of liver vessels.With the development of surgical and interventional techniques, the demand for a clear exhibition of the invasion of hepatic tumor to the portal vein system before operation is becoming stronger. Hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (IHCC) are two common malignant tumors of liver, and both have the characteristics of high degree of malignancy, rapid evolvement, easy to metastasis and poor prognosis. The median survival periods of the patients without operation are only 4 and 9 months respectively, and early invasion of the portal vein system is an important factor to affect the patient's prognosis. Carcinomas thrombosis in the branches or trunk of portal vein is a usual occurrence in the patients with HCC, and cavernous transformation of portal vein system and formation of fistula between hepatic artery and portal vein is the subsequent possible complications. In patients with IHCC, portal vein involvement is revealed as annular stenosis or subulate obstruction. The damage is usually confined to the outer layer of the vessel wall, and sometimes to the inner layer, but seldom to the lumen. Therefore, it is very important for a correct therapeutic plan to make clear whether the portal vein system is involved, and what about the location and extension of the lesion is.The study of digital virtual human has become the highlighted field internationally. The research of Chinese digital virtual human involves the setup of digital 3D geometrical model of human body of the oriental character (including models of bone, muscle, skin, tissue, organ, vessel, and etc.) and the standard altar anddatabase. Some above-mentioned key techniques will intrinsically comprise the data of the models of vessel and other pipes and the structure of neural system in human body. The rapid development of CT and MRI technique can provide clinicians with 2D images of higher quality and thinner slice which make it possible to reconstruct top 3D models of vessels. Applying the thin-slice tomographic data of MRA to the reconstruction of 3D virtual model of portal vein system, meanwhile, combined with the information of hepatic lesions (for example, space-occupying lesions as tumors), it is able to demonstrate exactly the tri-dimensional figures, spatial location and adjacent relationship of portal vein and lesions, and take 3D anatomic measurement as well. This method can provide exact and reliable anatomic basis for the access and plan of operation and is very promising in liver and gall surgery and interventional therapy. 一, The quality control and clinic application study on hepatic MRA by means of3DDCEMRAObjective: To evaluate the quality control of 3DDCEMRA in hepatic vessel imaging, and to observe the normal anatomy and aberrance of hepatic vein and portal vein. In addition to analyze the involvement of inferior vena behind liver resulted from hepatocellular carcinoma. Materials and Methods: Seventy-three patients with dubious liver abnormality were included in the study to undergo 3DDCEMRA examinations. The images from 43 of the 73 patients had wholly displayed hepatic vessel structures, and were employed to evaluate the quality control of 3DDCEMRA and observe the normal anatomy and aberrance of hepatic vein and portal vein. Besides, of the 43 cases, images from 40 cases were used to determine the diameter of the main branches and trunk of the portal vein, and images from 25 cases with post-operating hepatocellular carcinoma were used to evaluate the involvement of inferior vena behind liver. 3DDCEMRA was acquired by 3D FMSPGR sequence and coronary collection. The main parameters listed as follows: TR/TE/FA/FOV/Matrix were 5.9ms/1.2ms/30o/40x36cm/256xl28 respectively, with the slice of 3-5 mm. Gd-DTPA was used as the contrast agency for enhanced imaging with the three-fold routine dose of average 30-45 ml (0.3 mmol/Kg) and the injection velocity of 3 ml/s.The delayed time for scan was predicted by means of self-contrast from 20 cases with beforehand experimentation and to divide into groups according to different ages. Results: 1) The best collect-time for delayed scan of portal vein was 40-50s after injected contrast agency. Significant difference was not found in signal intensity of portal vein between groups according to different ages. 2) The right, middle and left hepatic vein were 92.3%, 87.5% and 80.2% respectively. The anatomical I and II type of hepatic vein were 40 cases (93%) and 3 cases (7%) respectively. The displaying percentage of right infero- posterior- hepatic vein was 9.35% (4/43). 3) The displaying percentage of the first to third grade branches of portal vein amounted to 100%, and the forth grade and it subordinate branches were also exhibited clearly. The situation of variant portal vein was showed as follows: anatomic I type, 2 cases (4.7%), II type, 2 cases(4.7%), and III type, 1 case (2.3%) respectively. Conclusion: 1) 3DDCEMRA is a rapid and accurate examination method for vessel imaging with the advantage of no damage. This method can display interested hepatic vessels clearly with homogeneous signal and good contrast between blood and background tissues. 2) It is very important in the quality control for vessel imaging on 3DDCEMRA by means of appropriated scanning sequence, specified quantity of contrast agency and finishing technique for imaging. The key to portography was to precisely estimate the delayed scanning time. 3) It is very helpful for the clinical application to observe the normal anatomy and aberrance of hepatic vein and evaluate the involvement of inferior vena behind liver resulted from hepatocellular carcinoma. 3DDCEMRA has peculiarly advantage to display anatomic structure of portal system and is very promising in clinical application.H > The value of 3DDCEMRA in the diagnosis of portal vein involvement withhepatocellular carcinoma and intrahepatic cholangiocarcinomaObjective: To evaluate the value of 3DDCEMRA in the diagnosis of portal veininvolvement with hepatocellular carcinoma and intrahepatic cholangiocarcinoma.Materials and Methods: 21 cases of HCC and 14 cases of IHCC (10 cases of hilarIHCC and 4 cases of IH PCC included) confirmed by surgery and pathology werecollected in this study. Plain and 3DDCEMRA was adopted. Results: Portal vein infiltration (6/42) and tumor thrombosis (8/42) were demonstrated in HCC group, and IHCC group showed portal vein infiltration (3/28), narrowing (5/28) and occlusion (7/28). Significant difference was found in portal vein invasion between HCC group and IHCC group (P<0.05). Conclusion: 3DDCEMRA showed high accuracy, no damage and direction in the diagnosis of portal vein involvement with hepatocellular carcinoma and intrahepatic cholangiocarcinoma, and is very important in the differentiation. It is very helpful for the selection of surgery and therapy plan in clinic. H, The experimental study of 3D reconstruction model of portal vein based on MRI images and 3D reconstruction model of hepatic veins based on VCH data set Objective: To reconstruct three-dimensional model of portal vein on the basis of MRI images and three-dimensional model of hepatic vein based on VCH data set. Materials and Methods: one normal male volunteer was employed to undergo liver dynamic enhanced MR scan using the sequence of 3D FMSPGR. The sequence was obtained with the main parameters as 5.9 ms TR, 1.2 ms TE, 30° FA, 40X36cm FOV and 128X128 Matrix. The slice was 1.0 mm with 0 mm space. The dose of Gd-DTPA was 25 ml and the injection velocity 3 ml/s. 2D fast axial image acquirement was used with the scan time of 46s and 80 frames of continuous images were obtained in portal phase. The upper abdomen data of virtual Chinese female referred to the VCH-Fl data set from the Nan Fang University (selecting one in every 5 slices with the thickness of 0.2 mm and interval of 1.0 mm respectively, total 85 slices). Such methods as image registration, image segmentation, and edge abstract were used for the establishment of three-dimensional model of portal vein or hepatic vein. The import software was 3D-Doctor and Photoshop 7.01. Results: The three-dimensional model of portal vein was established from the upper abdomen data of the male volunteer and demonstrated favorably the distribution and spatial configuration of the main branches of portal vine. The three-dimensional model of hepatic vein was established from the VCH data set. The model exactly showed the relationship and 3D anatomy at the spot of hepatic vein converging to inferior vena cava. Conclusions: High qualitythree-dimensional models of portal vein and hepatic vein were established successfully. It can demonstrate from varied views the basic situation and the adjacent structure relationships of portal vein system and hepatic vein system precisely and can be applied widely in clinical practice of liver and gall surgery and interventional therapy.