| Objectives:1. To elucidate the effect of different imaging sequences and imaging parameters of magnetic resonance angiography (MRA) on images of normal cevical arteries. 2. To quantify the flow velocities and the diameters of cervical arteries with MRA in normal group. 3. To explore the changes of cervical arteries on MRA images in nasopharyngeal carcinoma patients after radiotherapy and the effect of the different related risk factors.Materials and Methods:1. 32 cases of healthy volunteers were performed to obtain the images of the cervical arteries with MRA by using different imaging sequences and imaging parameters,and their effects on the MRA images were observed. 2. Fifty healthy volunteers were examined with DUS scanning and 2D-TOF MRA respectively,the mean blood flow velocities of the common carotid arteries were measured with these two methods,and the results were compared with each other. The diameters of the common carotid artery,internal carotid artery,external carotid artery and vertebral artery were also measure on the images of TOP MRA. And the results of the mean flow velocities and the diameters of the above-mentioned blood vessels were considered as reference standards. 3. 30 cases of nasopharyngeal carcinoma patients who had undergone the radiotherapy for about one year or more were examined by the same methods,and the results of the mean flow velocities and the diameters of the above-mentioned blood vessels were compared with the healthy group. Then these patients were divided into 6 groups according to the age,the end time of the radiotherapy,the dose of the radiotherapy,the scope of the radiotherapy,the source of radiotherapy and the splitting time of the radiotherapy. The correlations between the changes of cervical arteries among these groups were analyzed.Result:1. The signal ratios of the blood vessel to the muscle were decreased when the TR was prolonged;and the longer the TE was,the lower the signal of the carotid artery branch was. The larger the thickness of the slab was,the more the imaging scope was proportional to increasing,but the display of the tiny arteries wasdecreases somehow. The signal to noise ratio of 3D TOP MRA image was high,the outline of the arteries were smooth but their scope were small,The signal to noise ratio and the resolution of 3D TOP MOTSA MRA image were higher when compared to that of 2D TOP MRA,but the signal ratio of the blood vessel to the muscle became lower. When compared to 2D TOP MRA,the imaging scope of CE MRA was bigger,the resolution of images was higher and the acquired time of image was shorter. So the distribution of the cervical arteries ranging from the aortic arch to the Willis's loop all could be visualized with CE MRA. The missing degree of the local signal at the posterior lateral section of the root of the internal carotid artery on the 2D TOP MRA images was related to the furcate angle of the carotid artery branches,the bigger the angle was,the more the signal was missed. 2. The normal transverse diameters of the cervical arteries of the healthy group on 2D TOP MRA images were as following:the left CCA was 6.0364+1.2912mm,right was 6.2642+0.8475mm;the left ICA was 4.2509+0.8729mm,right was 4.3148+0.6742;the left ECA was3.223210.7131 mm,right was3.1977+0.6539mm;the left VmM was 15-75cm/s,right 17-69cm/s respectively. 3. In the groups of the nasopharyngeal carcinoma patients,the calibers of the common carotid artery and the internal carotid artery decreased,the average blood velocity of the common carotid artery increased significantly when compared to that of control group. The incidence of cervical arteries' constriction in the nasopharyngeal carcinoma patients is 30%,which was higher than that of the control group. The cervical arteries' constriction can be divided into four grades:mild constriction,middle constriction,severe constriction and occlusion. The age and the end time after radiotherapy were the main related factors in carotid artery constriction of the nasopharyngeal carcinoma patients.Conclusions:1. TOP MR... |
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