The Basic And Clinical Research On Accuracy Of Thoracic Aorta' Flow Velocity Measured By Magnetic Resonance Phase Contrast

[Abstract]Objective:In vitro, in vivo experiments to test the accuracy of aortic blood flow velocity measured by magnetic resonance phase contrast (PC MRI). On this basis, we use this method to establish the normal reference values of the thoracic aorta blood flow velocity and blood flow, which is very useful for clinical use and future aortic hemodynamic study.Methods:Part I:(1) We applied the method of PC MRI on the model of straight vessel to measured the different fluid velocity(+100%±80%±60%±40%±20%Ocm/s),compare the results with tachometer and get the correction formula of PC MRI method; (2) The accuracy of thoracic aorta in vitro were measured by PC MRI:①With different VEC(90,120,150,180cm/s), we applied the method of PC MRI on the model of aorta to measured the fluid velocity(100cm/s) in the different parts of U-type glass tube (U1, U2, U3), compare the results with tachometer and get the best VEC value;②With VEC 150cm/s, we applied the method of PC MRI on the model of aorta to measured the fluid velocity(100cm/s,80cm/s,60cm/s,40cm/s, 20cm/s, Ocm/s) of the different parts of U-type glass tube (U1, U2, U3), compare the results with tachometer and observe the accuracy of this method;③With VEC 150cm/s, we applied the method of PC MRI on the model of aorta to measured the fluid velocity(-100cm/s,-80cm/s,-60cm/s,-40cm/s,-20cm/s,-Ocm/s) of the different parts of U-type glass tube (U1, U2, U3), compare the results with tachometer and observe the accuracy of aortic regurgitation.PartⅡ:(1) We applied the method of PC MRI and the method of UCG respectively to measured the ascending aortic blood flow (31 healthy volunteers and 21 patients) with cardiovascular diseases within the cardiac cycle, results compared with the stroke volumes which were obtained by the method of 4D-MRI ventricular volume measurements, compared the measurement's accuracy of these methods. (2) We applied the method of PC MRI and the method of UCG to measured the ascending aortic blood flow of the healthy volunteers (PC MRI 9 cases, UCG 11 cases) twice, compared the first results with the second, observe the repeatability of these methods.PartⅢ:The mean blood flow volume and mean flow velocity of the ascending aorta and thoracic descending aorta were measured in 136 healthy volunteers with PC MRI. These data were analyzed.Results:PartⅠ:(1) The result have excellent correlation between PC MRI and tachometer (r=0.99) in straight vessel model. The correction formula:y= 0.97lx +0.494. (2) The accuracy of thoracic aorta in vitro were measured by PC MRI:①With VEC 90cm/s, there have significant differences between the result measured by PC MRI with the value of tachometer(P<0.05). With VEC were different (120,150, 180cm/s), there have no significant differences between the result measured by PC MRI with the value of tachometer(P> 0.05).②ith VEC 150cm/s, there have no significant differences between the velocity (±100,±80,±60,±40,±20, 0cm/s)and direction(forward, reverse) measured by PC MRI with the value of tachometer in (P> 0.05).PartⅡ:The result were measured by the method of PC MRI have excellent correlation with the method of 4D-MRI ventricular volume measurements (normal group:r4D:pc= 0.917; cardiovascular patient groups:Uo-, pc= 0.895). There has no significance between these two methods (normal group:P> 0.05, cardiovascular patient groups:P> 0.05). There have high repeatability in velocity measured by the method of PC MRI (P= 0.872, r= 0.950).The result were measured by the method of UCG have correlation with the method of 4D-MRI ventricular volume measurements (normal group:r4D:UCG= 0.737; cardiovascular patient groups:r4D:ucg= 0.633). There have significance between these two methods (normal group:P<0.05, cardiovascular patient groups:P<0.05). There have general repeatability in velocity measured by the method of UCG (P= 0.721, r= 0.753).Part III:(1) Males were larger than females in the values of diameter and mean blood flow volume of ascending aorta and thoracic descending aorta(P<0.05), There were no significance between mean flow velocity of the ascending aorta and thoracic descending aorta between sexes (P> 0.05). (2) There were significant difference between ages in values of diameter, mean blood flow volume and mean flow velocity of ascending aorta and thoracic descending aorta(P<0.05). With age rising, diameters of aorta enlarge gradually, the average blood flow and mean flow velocity of aorta decreased gradually. (3) females were larger than Males in the rate of diameter changes of aortic (ascending aorta 4.73%,2.01%; thoracic descending aorta 0.58%,0.51%). With age rising, the rates of diameter changes of aortic decreased gradually (ascending aorta 5.20%,3.82%,2.31%; thoracic descending aorta 0.81%,0.53%,0.03%).Conclusion:(1) PC MRI is a safe, non-invasive, rapid, accurate, informative, high repeatability method in measurement of parameters of aortic blood flow. The accuracy and repeatability of PC MRI is better than UCG, this method can be seen as the "gold standard" measurement of thoracic aortic blood flow. (2) There have difference in diameter, mean blood flow volume of ascending aorta and descending aorta between sexes and ages. There have no difference in mean flow velocity of ascending aorta and descending aorta between sexes. There have difference in mean flow velocity of ascending aorta and descending aorta between ages. (3) The reference range of different ages, different genders in ascending aortic:mean blood flow and mean flow velocity of 20-39 year old male is 5.56-7.13L/min, 9.45～27.63cm/s; Mean blood flow and mean flow velocity of 20～39 year old female is 4.98～6.27L/min,8.48～24.30cm/s. Mean blood flow and mean flow velocity of 40～59 year old male is 5.42～6.17L/min,9.21～23.91cm/s; Mean blood flow and mean flow velocity of 40～59 year old female is 4.82～5.37L/min,8.19～20.81 cm/s. Mean blood flow and mean flow velocity of 60～80 year old male is 5.59～6.16L/min,9.50-23.87cm/s; Mean blood flow and mean flow velocity of 60～80 year old female is 4.68～5.15L/min,7.96～19.96cm/s. (4) the reference range of different ages, different genders in descending aorta:mean blood flow and mean flow velocity of 20～39 year old male is 4.72～6.06L/min,8.02～23.4cm/s; Mean blood flow and mean flow velocity of 20～39 year old female is 4.23～5.32L/min,7.19～20.62cm/s. Mean blood flow and mean flow velocity of 40～59 year old male is 4.60～5.24 L/min,7.82～20.31 cm/s; Mean blood flow and mean flow velocity of 40～59 year old female is 4.09～4.56 L/min,6.95～17.67cm/s. Mean blood flow and mean flow velocity of 60～80 year old male is 4.75～5.23L/min,8.07～20.27cm/s; Mean blood flow and mean flow velocity of 60～80 year old female is 3.97～4.37L/min,6.75～16.93cm/s.